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  • 1. Aalbers, J.
    et al.
    Agostini, F.
    Alfonsi, M.
    Amaro, F. D.
    Amsler, C.
    Aprile, E.
    Arazi, L.
    Arneodo, F.
    Barrow, P.
    Baudis, L.
    Benabderrahmane, M. L.
    Berger, T.
    Beskers, B.
    Breskin, A.
    Breur, P. A.
    Brown, A.
    Brown, E.
    Bruenner, S.
    Bruno, G.
    Budnik, R.
    Butikofer, L.
    Calvén, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Cardoso, J. M. R.
    Cichon, D.
    Coderre, D.
    Colijn, A. P.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Cussonneau, J. P.
    Decowski, M. P.
    Diglio, S.
    Drexlin, G.
    Duchovni, E.
    Erdal, E.
    Eurin, G.
    Ferella, Alfredo
    Stockholm University, Faculty of Science, Department of Physics.
    Fieguth, A.
    Fulgione, W.
    Rosso, A. Gallo
    Di Gangi, P.
    Di Giovanni, A.
    Galloway, M.
    Garbini, M.
    Geis, C.
    Glueck, F.
    Grandi, L.
    Greene, Z.
    Grignon, C.
    Hasterok, C.
    Hannen, V.
    Hogenbirk, E.
    Howlett, J.
    Hilk, D.
    Hils, C.
    James, A.
    Kaminsky, B.
    Kazama, S.
    Kilminster, B.
    Kish, A.
    Krauss, L. M.
    Landsman, H.
    Lang, R. F.
    Lin, Q.
    Linde, F. L.
    Lindemann, S.
    Lindner, M.
    Lopes, J. A. M.
    Undagoitia, T. Marrodan
    Masbou, J.
    Massoli, F. V.
    Mayani, D.
    Messina, M.
    Micheneau, K.
    Molinario, A.
    Morå, Knut D.
    Stockholm University, Faculty of Science, Department of Physics.
    Morteau, E.
    Murra, M.
    Naganoma, J.
    Newstead, J. L.
    Ni, K.
    Oberlack, U.
    Pakarha, P.
    Pelssers, Bart
    Stockholm University, Faculty of Science, Department of Physics.
    de Perio, P.
    Persiani, R.
    Piastra, F.
    Piro, M. C.
    Plante, G.
    Rauch, L.
    Reichard, S.
    Rizzo, A.
    Rupp, N.
    Dos Santos, J. M. F.
    Sartorelli, G.
    Scheibelhut, M.
    Schindler, S.
    Schumann, M.
    Schreiner, J.
    Lavina, L. Scotto
    Selvi, M.
    Shagin, P.
    Silva, M. C.
    Simgen, H.
    Sissol, P.
    von Sivers, M.
    Thers, D.
    Thum, J.
    Tiseni, A.
    Trotta, R.
    Tunnell, C. D.
    Valerius, K.
    Vargas, M. A.
    Wang, H.
    Wei, Y.
    Weinheimer, C.
    Wester, T.
    Wulf, J.
    Zhang, Y.
    Zhu, T.
    Zuber, K.
    DARWIN: towards the ultimate dark matter detector2016In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, no 11, article id 017Article in journal (Refereed)
    Abstract [en]

    DARk matter WImp search with liquid xenoN (DARWIN(2)) will be an experiment for the direct detection of dark matter using a multi-ton liquid xenon time projection chamber at its core. Its primary goal will be to explore the experimentally accessible parameter space for Weakly Interacting Massive Particles (WIMPs) in a wide mass-range, until neutrino interactions with the target become an irreducible background. The prompt scintillation light and the charge signals induced by particle interactions in the xenon will be observed by VUV sensitive, ultra-low background photosensors. Besides its excellent sensitivity to WIMPs above a mass of 5 GeV/c(2), such a detector with its large mass, low-energy threshold and ultra-low background level will also be sensitive to other rare interactions. It will search for solar axions,galactic axion-like particles and the neutrinoless double-beta decay of Xe-136, as well as measure the low-energy solar neutrino flux with <1% precision, observe coherent neutrino-nucleus interactions, and detect galactic supernovae. We present the concept of the DARWIN detector and discuss its physics reach, the main sources of backgrounds and the ongoing detector design and R&D efforts.

  • 2. Aamer, Aysha
    et al.
    Nicholl, Matt
    Jerkstrand, Anders
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gomez, Sebastian
    Oates, Samantha R.
    Smartt, Stephen J.
    Srivastav, Shubham
    Leloudas, Giorgos
    Anderson, Joseph P.
    Berger, Edo
    de Boer, Thomas
    Chambers, Kenneth
    Chen, Ting-Wan
    Galbany, Lluís
    Gao, Hua
    Gompertz, Benjamin P.
    González-Bañuelos, Maider
    Gromadzki, Mariusz
    Gutiérrez, Claudia P.
    Inserra, Cosimo
    Lowe, Thomas B.
    Magnier, Eugene A.
    Mazzali, Paolo A.
    Moore, Thomas
    Müller-Bravo, Tomás E.
    Pursiainen, Miika
    Rest, Armin
    Schulze, Steve
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Smith, Ken W.
    Terwel, Jacco H.
    Wainscoat, Richard
    Young, David R.
    A precursor plateau and pre-maximum [O ii] emission in the superluminous SN2019szu: a pulsational pair-instability candidate2023In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 527, no 4, p. 11970-11995Article in journal (Refereed)
    Abstract [en]

    We present a detailed study on SN2019szu, a Type I superluminous supernova at z = 0.213 that displayed unique photometric and spectroscopic properties. Pan-STARRS and ZTF forced photometry show a pre-explosion plateau lasting ∼40 d. Unlike other SLSNe that show decreasing photospheric temperatures with time, the optical colours show an apparent temperature increase from ∼15 000 to ∼20 000 K over the first 70 d, likely caused by an additional pseudo-continuum in the spectrum. Remarkably, the spectrum displays a forbidden emission line (likely attributed to λλ7320,7330) visible 16 d before maximum light, inconsistent with an apparently compact photosphere. This identification is further strengthened by the appearances of [O III] λλ4959, 5007, and [O III] λ4363 seen in the spectrum. Comparing with nebular spectral models, we find that the oxygen line fluxes and ratios can be reproduced with ∼0.25 M of oxygen-rich material with a density of ∼10−15 g cm−3⁠. The low density suggests a circumstellar origin, but the early onset of the emission lines requires that this material was ejected within the final months before the terminal explosion, consistent with the timing of the precursor plateau. Interaction with denser material closer to the explosion likely produced the pseudo-continuum bluewards of ∼5500 Å. We suggest that this event is one of the best candidates to date for a pulsational pair-instability ejection, with early pulses providing the low density material needed for the formation of the forbidden emission line, and collisions between the final shells of ejected material producing the pre-explosion plateau.

  • 3. Aartsen, M. G.
    et al.
    Ackermann, M.
    Adams, J.
    Aguilar, J. A.
    Ahlers, M.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Altmann, D.
    Anderson, T.
    Arguelles, C.
    Arlen, T. C.
    Auffenberg, J.
    Bai, X.
    Barwick, S. W.
    Baum, V.
    Bay, R.
    Beatty, J. J.
    Tjus, J. Becker
    Becker, K. -H
    BenZvi, S.
    Berghaus, P.
    Berley, D.
    Bernardini, E.
    Bernhard, A.
    Besson, D. Z.
    Binder, G.
    Bindig, D.
    Bissok, M.
    Blaufuss, E.
    Blumenthal, J.
    Boersma, D. J.
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Bos, F.
    Bose, D.
    Boeser, S.
    Botner, O.
    Brayeur, L.
    Bretz, H. -P
    Brown, A. M.
    Brunner, J.
    Buzinsky, N.
    Casey, J.
    Casier, M.
    Cheung, E.
    Chirkin, D.
    Christov, A.
    Christy, B.
    Clark, K.
    Classen, L.
    Clevermann, F.
    Coenders, S.
    Cowen, D. F.
    Silva, A. H. Cruz
    Daughhetee, J.
    Davis, J. C.
    Day, M.
    de Andre, J. P. A. M.
    De Clercq, C.
    De Ridder, S.
    Desiati, P.
    de Vries, K. D.
    de With, M.
    De Young, T.
    Diaz-Velez, J. C.
    Dunkman, M.
    Eagan, R.
    Eberhardt, B.
    Eichmann, B.
    Eisch, J.
    Euler, S.
    Evenson, P. A.
    Fadiran, O.
    Fazely, A. R.
    Fedynitch, A.
    Feintzeig, J.
    Felde, J.
    Feusels, T.
    Filimonov, K.
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fischer-Wasels, T.
    Flis, Samuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Franckowiak, A.
    Frantzen, K.
    Fuchs, T.
    Gaisser, T. K.
    Gaior, R.
    Gallagher, J.
    Gerhardt, L.
    Gier, D.
    Gladstone, L.
    Gluesenkamp, T.
    Goldschmidt, A.
    Golup, G.
    Gonzalez, J. G.
    Goodman, J. A.
    Gora, D.
    Grant, D.
    Gretskov, P.
    Groh, J. C.
    Gross, A.
    Ha, C.
    Haack, C.
    Ismail, A. Haj
    Hallen, P.
    Hallgren, A.
    Halzen, F.
    Hanson, K.
    Hebecker, D.
    Heereman, D.
    Heinen, D.
    Helbing, K.
    Hellauer, R.
    Hellwig, D.
    Hickford, S.
    Hill, G. C.
    Hoffman, K. D.
    Hoffmann, R.
    Homeier, A.
    Hoshina, K.
    Huang, F.
    Huelsnitz, W.
    Hulth, Per Olof
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hussain, S.
    Ishihara, A.
    Jacobi, E.
    Jacobsen, J.
    Jagielski, K.
    Japaridze, G. S.
    Jero, K.
    Jlelati, O.
    Jurkovic, M.
    Kaminsky, B.
    Kappes, A.
    Karg, T.
    Karle, A.
    Kauer, M.
    Keivani, A.
    Kelley, J. L.
    Kheirandish, A.
    Kiryluk, J.
    Klaes, J.
    Klein, S. R.
    Koehne, J. -H
    Kohnen, G.
    Kolanoski, H.
    Koob, A.
    Koepke, L.
    Kopper, C.
    Kopper, S.
    Koskinen, D. J.
    Kowalski, M.
    Kriesten, A.
    Krings, K.
    Kroll, G.
    Kroll, M.
    Kunnen, J.
    Kurahashi, N.
    Kuwabara, T.
    Labare, M.
    Lanfranchi, J. L.
    Larsen, D. T.
    Larson, M. J.
    Lesiak-Bzdak, M.
    Leuermann, M.
    Luenemann, J.
    Madsen, J.
    Maggi, G.
    Maruyama, R.
    Mase, K.
    Matis, H. S.
    Maunu, R.
    McNally, F.
    Meagher, K.
    Medici, M.
    Meli, A.
    Meures, T.
    Miarecki, S.
    Middell, E.
    Middlemas, E.
    Milke, N.
    Miller, J.
    Mohrmann, L.
    Montaruli, T.
    Morse, R.
    Nahnhauer, R.
    Naumann, U.
    Niederhausen, H.
    Nowicki, S. C.
    Nygren, D. R.
    Obertacke, A.
    Odrowski, S.
    Olivas, A.
    Omairat, A.
    O'Murchadha, A.
    Palczewski, T.
    Paul, L.
    Penek, Oe.
    Pepper, J. A.
    de los Heros, C. Perez
    Pfendner, C.
    Pieloth, D.
    Pinat, E.
    Posselt, J.
    Price, P. B.
    Przybylski, G. T.
    Puetz, J.
    Quinnan, M.
    Raedel, L.
    Rameez, M.
    Rawlins, K.
    Redl, P.
    Rees, I.
    Reimann, R.
    Relich, M.
    Resconi, E.
    Rhode, W.
    Richman, M.
    Riedel, B.
    Robertson, S.
    Rodrigues, J. P.
    Rongen, M.
    Rott, C.
    Ruhe, T.
    Ruzybayev, B.
    Ryckbosch, D.
    Saba, S. M.
    Sander, H. -G
    Sandroos, J.
    Santander, M.
    Sarkar, S.
    Schatto, K.
    Scheriau, F.
    Schmidt, T.
    Schmitz, M.
    Schoenen, S.
    Schoeneberg, S.
    Schoenwald, A.
    Schukraft, A.
    Schulte, L.
    Schulz, O.
    Seckel, D.
    Sestayo, Y.
    Seunarine, S.
    Shanidze, R.
    Smith, M. W. E.
    Soldin, D.
    Spiczak, G. M.
    Spiering, C.
    Stamatikos, M.
    Stanev, T.
    Stanisha, N. A.
    Stasik, A.
    Stezelberger, T.
    Stokstad, R. G.
    Stoessl, A.
    Strahler, E. A.
    Strom, R.
    Strotjohann, N. L.
    Sullivan, G. W.
    Taavola, H.
    Taboada, I.
    Tamburro, A.
    Tepe, A.
    Ter-Antonyan, S.
    Terliuk, A.
    Tesic, G.
    Tilav, S.
    Toale, P. A.
    Tobin, M. N.
    Tosi, D.
    Tselengidou, M.
    Unger, E.
    Usner, M.
    Vallecorsa, S.
    van Eijndhoven, N.
    Vandenbroucke, J.
    van Santen, J.
    Vehring, M.
    Voge, M.
    Vraeghe, M.
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wallraff, M.
    Weaver, Ch.
    Wellons, M.
    Wendt, C.
    Westerhoff, S.
    Whelan, B. J.
    Whitehorn, N.
    Wichary, C.
    Wiebe, K.
    Wiebusch, C. H.
    Williams, D. R.
    Wissing, H.
    Wolf, Martin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wood, T. R.
    Woschnagg, K.
    Xu, D. L.
    Xu, X. W.
    Yanez, J. P.
    Yodh, G.
    Yoshida, S.
    Zarzhitsky, P.
    Ziemann, J.
    Zierke, S.
    Zoll, Marcel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Determining neutrino oscillation parameters from atmospheric muon neutrino disappearance with three years of IceCube DeepCore data2015In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 91, no 7, article id 072004Article in journal (Refereed)
    Abstract [en]

    We present a measurement of neutrino oscillations via atmospheric muon neutrino disappearance with three years of data of the completed IceCube neutrino detector. DeepCore, a region of denser IceCube instrumentation, enables the detection and reconstruction of atmospheric muon neutrinos between 10 and 100 GeV, where a strong disappearance signal is expected. The IceCube detector volume surrounding DeepCore is used as a veto region to suppress the atmospheric muon background. Neutrino events are selected where the detected Cherenkov photons of the secondary particles minimally scatter, and the neutrino energy and arrival direction are reconstructed. Both variables are used to obtain the neutrino oscillation parameters from the data, with the best fit given by Delta m(32)(2) = 2.72(-0.20)(+0.19) x 10(-3) eV(2) and sin(2)theta(23) = 0.53(-0.12)(+0.09) (normal mass ordering assumed). The results are compatible, and comparable in precision, to those of dedicated oscillation experiments.

  • 4. Aartsen, M. G.
    et al.
    Ackermann, M.
    Adams, J.
    Aguilar, J. A.
    Ahlers, M.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Altmann, D.
    Anderson, T.
    Arguelles, C.
    Arlen, T. C.
    Auffenberg, J.
    Bai, X.
    Barwick, S. W.
    Baum, V.
    Beatty, J. J.
    Tjus, J. Becker
    Becker, K. -H
    BenZvi, S.
    Berghaus, P.
    Berley, D.
    Bernardini, E.
    Bernhard, A.
    Besson, D. Z.
    Binder, G.
    Bindig, D.
    Bissok, M.
    Blaufuss, E.
    Blumenthal, J.
    Boersma, D. J.
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Bos, F.
    Bose, D.
    Boeser, S.
    Botner, O.
    Brayeur, L.
    Bretz, H. -P
    Brown, A. M.
    Casey, J.
    Casier, M.
    Cheung, E.
    Chirkin, D.
    Christov, A.
    Christy, B.
    Clark, K.
    Classen, L.
    Cleverinann, F.
    Coenders, S.
    Cowen, D. F.
    Silva, A. H. Cruz
    Danninger, Matthias
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Daughhetee, J.
    Davis, J. C.
    Day, M.
    de Andre, J. P. A. M.
    De Clercq, C.
    De Ridder, S.
    Desiati, P.
    de Vries, K. D.
    de With, M.
    DeYoung, T.
    Diaz-Velez, J. C.
    Dunkman, M.
    Eagan, R.
    Eberhardt, B.
    Eichmann, B.
    Eisch, J.
    Euler, S.
    Evenson, P. A.
    Fadiran, O.
    Fazely, A. R.
    Fedynitch, A.
    Feintzeig, J.
    Felde, J.
    Feusels, T.
    Filimonov, K.
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fischer-Wasels, T.
    Flis, Samuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Franckowiak, A.
    Frantzen, K.
    Fuchs, T.
    Gaisser, T. K.
    Gaior, R.
    Gallagher, J.
    Gerhardt, L.
    Gier, D.
    Gladstone, L.
    Gluesenkamp, T.
    Goldschmidt, A.
    Golup, G.
    Gonzalez, J. G.
    Goodman, J. A.
    Gora, D.
    Grant, D.
    Gretskov, P.
    Groh, J. C.
    Gross, A.
    Ha, C.
    Haack, C.
    Ismail, A. Haj
    Hallen, P.
    Hallgren, A.
    Halzen, F.
    Hanson, K.
    Hebecker, D.
    Heereman, D.
    Heinen, D.
    Helbing, K.
    Hellauer, R.
    Hellwig, D.
    Hickford, S.
    Hill, G. C.
    Hoffman, K. D.
    Hoffmann, R.
    Homeier, A.
    Hoshina, K.
    Huang, F.
    Huelsnitz, W.
    Hulth, Per Olof
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hussain, S.
    Ishihara, A.
    Jacobi, E.
    Jacobsen, J.
    Jagielski, K.
    Japaridze, G. S.
    Jero, K.
    Jlelati, O.
    Jurkovic, M.
    Kaminsky, B.
    Kappes, A.
    Karg, T.
    Karle, A.
    Kauer, M.
    Kelley, J. L.
    Kheirandish, A.
    Kiryluk, J.
    Klaes, J.
    Klein, S. R.
    Koehne, J. -H
    Kohnen, G.
    Kolanoski, H.
    Koob, A.
    Koepke, L.
    Kopper, C.
    Kopper, S.
    Koskinen, D. J.
    Kowalski, M.
    Kriesten, A.
    Krings, K.
    Kroll, G.
    Kroll, M.
    Kunnen, J.
    Kurahashi, N.
    Kuwabara, T.
    Labare, M.
    Larsen, D. T.
    Larson, M. J.
    Lesiak-Bzdak, M.
    Leuermann, M.
    Leute, J.
    Luenemann, J.
    Madsen, J.
    Maggi, G.
    Maruyama, R.
    Mase, K.
    Matis, H. S.
    Maunu, R.
    McNally, F.
    Meagher, K.
    Medici, M.
    Meli, A.
    Meures, T.
    Miarecki, S.
    Middell, E.
    Middlemas, E.
    Milke, N.
    Miller, J.
    Mohrmann, L.
    Montaruli, T.
    Morse, R.
    Nahnhauer, R.
    Naumann, U.
    Niederhausen, H.
    Nowicki, S. C.
    Nygren, D. R.
    Obertacke, A.
    Odrowski, S.
    Olivas, A.
    Omairat, A.
    O'Murchadha, A.
    Palczewski, T.
    Paul, L.
    Penek, Oe.
    Pepper, J. A.
    de los Heros, C. Perez
    Pfendner, C.
    Pieloth, D.
    Pinat, E.
    Posselt, J.
    Price, P. B.
    Przybylski, G. T.
    Puetz, J.
    Quinnan, M.
    Raedel, L.
    Rameez, M.
    Rawlins, K.
    Redl, P.
    Rees, I.
    Reimann, R.
    Relich, M.
    Resconi, E.
    Rhode, W.
    Richman, M.
    Riedel, B.
    Robertson, S.
    Rodrigues, Jp.
    Rongen, M.
    Rott, C.
    Ruhe, T.
    Ruzybayev, B.
    Ryckbosch, D.
    Saba, S. M.
    Sander, H. -G
    Sandroos, J.
    Santander, M.
    Sarkar, S.
    Schatto, K.
    Scheriau, F.
    Schmidt, T.
    Schmitz, M.
    Schoenen, S.
    Schoeneberg, S.
    Schoenwald, A.
    Schukraft, A.
    Schulte, L.
    Schulz, O.
    Seckel, D.
    Sestayo, Y.
    Seunarine, S.
    Shanidze, R.
    Smith, M. W. E.
    Soldin, D.
    Spiczak, G. M.
    Spiering, C.
    Stamatikos, M.
    Stanev, T.
    Stanisha, N. A.
    Stasik, A.
    Stezelberger, T.
    Stokstad, R. G.
    Stoessl, A.
    Strahler, E. A.
    Stroem, R.
    Strotjohann, N. L.
    Sullivan, G. W.
    Taavola, H.
    Taboada, I.
    Tamburro, A.
    Tepe, A.
    Ter-Antonyan, S.
    Terliuk, A.
    Tesic, G.
    Tilav, S.
    Toale, P. A.
    Tobin, M. N.
    Tosi, D.
    Tselengidou, M.
    Unger, E.
    Usner, M.
    Vallecorsa, S.
    van Eijndhoven, N.
    Vandenbroucke, J.
    van Santen, J.
    Vehring, M.
    Voge, M.
    Vraeghe, M.
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wallraff, M.
    Weaver, Ch.
    Wellons, M.
    Wendt, C.
    Westerhoff, S.
    Whelan, B. J.
    Whitehorn, N.
    Wichary, C.
    Wiebe, K.
    Wiebusch, C. H.
    Williams, D. R.
    Wissing, H.
    Wolf, Martin
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wood, T. R.
    Woschnagg, K.
    Xu, D. L.
    Xu, X. W.
    Yanez, J. P.
    Yodh, G.
    Yoshida, S.
    Zarzhitsky, P.
    Ziemann, J.
    Zierke, S.
    Zoll, Marcel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Searches for small-scale anisotropies from neutrino point sources with three years of IceCube data2015In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 66, p. 39-52Article in journal (Refereed)
    Abstract [en]

    Recently, IceCube found evidence for a diffuse signal of astrophysical neutrinos in an energy range of similar to 60 TeV to the PeV-scale [1]. The origin of those events, being a key to understanding the origin of cosmic rays, is still an unsolved question. So far, analyses have not succeeded to resolve the diffuse signal into point-like sources. Searches including a maximum-likelihood-ratio test, based on the reconstructed directions and energies of the detected down- and up-going neutrino candidates, were also performed on IceCube data leading to the exclusion of bright point sources. In this paper, we present two methods to search for faint neutrino point sources in three years of IceCube data, taken between 2008 and 2011. The first method is an autocorrelation test, applied separately to the northern and southern sky. The second method is a multipole analysis, which expands the measured data in the northern hemisphere into spherical harmonics and uses the resulting expansion coefficients to separate signal from background. With both methods, the results are consistent with the background expectation with a slightly more sparse spatial distribution, corresponding to an underfluctuation. Depending on the assumed number of sources, the resulting upper limit on the flux per source in the northern hemisphere for an E-2 energy spectrum ranges from similar to 1.5. 10(-8) GeV/cm(2) s(-1), in the case of one assumed source, to similar to 4. 10(-10) GeV/cm(2) s(-1), in the case of 3500 assumed sources.

  • 5. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhang, Z.
    Detection of astrophysical tau neutrino candidates in IceCube2022In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 82, no 11, article id 1031Article in journal (Refereed)
    Abstract [en]

    High-energy tau neutrinos are rarely produced in atmospheric cosmic-ray showers or at cosmic particle accelerators, but are expected to emerge during neutrino propagation over cosmic distances due to flavor mixing. When high energy tau neutrinos interact inside the IceCube detector, two spatially separated energy depositions may be resolved, the first from the charged current interaction and the second from the tau lepton decay. We report a novel analysis of 7.5 years of IceCube data that identifies two candidate tau neutrinos among the 60 High-Energy Starting Events (HESE) collected during that period. The HESE sample offers high purity, all-sky sensitivity, and distinct observational signatures for each neutrino flavor, enabling a new measurement of the flavor composition. The measured astrophysical neutrino flavor composition is consistent with expectations, and an astrophysical tau neutrino flux is indicated at 2.8 sigma significance.

  • 6. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    IceCube Search for Neutrinos Coincident with Gravitational Wave Events from LIGO/Virgo Run O32023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 944, no 1, article id 80Article in journal (Refereed)
    Abstract [en]

    Using data from the IceCube Neutrino Observatory, we searched for high-energy neutrino emission from the gravitational-wave events detected by the advanced LIGO and Virgo detectors during their third observing run. We did a low-latency follow-up on the public candidate events released during the detectors' third observing run and an archival search on the 80 confident events reported in the GWTC-2.1 and GWTC-3 catalogs. An extended search was also conducted for neutrino emission on longer timescales from neutron star containing mergers. Follow-up searches on the candidate optical counterpart of GW190521 were also conducted. We used two methods; an unbinned maximum likelihood analysis and a Bayesian analysis using astrophysical priors, both of which were previously used to search for high-energy neutrino emission from gravitational-wave events. No significant neutrino emission was observed by any analysis, and upper limits were placed on the time-integrated neutrino flux as well as the total isotropic equivalent energy emitted in high-energy neutrinos.

  • 7. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Low energy event reconstruction in IceCube DeepCore2022In: European Physical Journal C, ISSN 1434-6044, E-ISSN 1434-6052, Vol. 82, no 9, article id 807Article in journal (Refereed)
    Abstract [en]

    The reconstruction of event-level information, such as the direction or energy of a neutrino interacting in IceCube DeepCore, is a crucial ingredient to many physics analyses. Algorithms to extract this high level information from the detector's raw data have been successfully developed and used for high energy events. In this work, we address unique challenges associated with the reconstruction of lower energy events in the range of a few to hundreds of GeV and present two separate, state-of-the-art algorithms. One algorithm focuses on the fast directional reconstruction of events based on unscattered light. The second algorithm is a likelihood-based multipurpose reconstruction offering superior resolutions, at the expense of larger computational cost.

  • 8. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for Astrophysical Neutrinos from 1FLE Blazars with IceCube2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 938, no 1, article id 38Article in journal (Refereed)
    Abstract [en]

    The majority of astrophysical neutrinos have undetermined origins. The IceCube Neutrino Observatory has observed astrophysical neutrinos but has not yet identified their sources. Blazars are promising source candidates, but previous searches for neutrino emission from populations of blazars detected in ≳GeV gamma rays have not observed any significant neutrino excess. Recent findings in multimessenger astronomy indicate that high-energy photons, coproduced with high-energy neutrinos, are likely to be absorbed and reemitted at lower energies. Thus, lower-energy photons may be better indicators of TeV–PeV neutrino production. This paper presents the first time-integrated stacking search for astrophysical neutrino emission from MeV-detected blazars in the first Fermi Large Area Telescope low energy (1FLE) catalog using ten years of IceCube muon–neutrino data. The results of this analysis are found to be consistent with a background-only hypothesis. Assuming an E−2 neutrino spectrum and proportionality between the blazars MeV gamma-ray fluxes and TeV–PeV neutrino flux, the upper limit on the 1FLE blazar energy-scaled neutrino flux is determined to be 1.64 × 10−12 TeV cm−2 s−1 at 90% confidence level. This upper limit is approximately 1% of IceCube's diffuse muon–neutrino flux measurement.

  • 9. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm Univ, Oskar Klein Ctr, SE-10691 Stockholm, Sweden.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for High-energy Neutrino Emission from Galactic X-Ray Binaries with IceCube2022In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 930, no 2, article id L24Article in journal (Refereed)
    Abstract [en]

    We present the first comprehensive search for high-energy neutrino emission from high- and low-mass X-ray binaries conducted by IceCube. Galactic X-ray binaries are long-standing candidates for the source of Galactic hadronic cosmic rays and neutrinos. The compact object in these systems can be the site of cosmic-ray acceleration, and neutrinos can be produced by interactions of cosmic rays with radiation or gas, in the jet of a microquasar, in the stellar wind, or in the atmosphere of the companion star. We study X-ray binaries using 7.5 yr of IceCube data with three separate analyses. In the first, we search for periodic neutrino emission from 55 binaries in the Northern Sky with known orbital periods. In the second, the X-ray light curves of 102 binaries across the entire sky are used as templates to search for time-dependent neutrino emission. Finally, we search for time-integrated emission of neutrinos for a list of 4 notable binaries identified as microquasars. In the absence of a significant excess, we place upper limits on the neutrino flux for each hypothesis and compare our results with theoretical predictions for several binaries. In addition, we evaluate the sensitivity of the next generation neutrino telescope at the South Pole, IceCube-Gen2, and demonstrate its power to identify potential neutrino emission from these binary sources in the Galaxy.

  • 10. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for neutrino emission from cores of active galactic nuclei2022In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 106, no 2, article id 022005Article in journal (Refereed)
    Abstract [en]

    The sources of the majority of the high-energy astrophysical neutrinos observed with the IceCube neutrino telescope at the South Pole are unknown. So far, only a flaring gamma-ray blazar was compellingly associated with the emission of high-energy neutrinos. However, several studies suggest that the neutrino emission from the gamma-ray blazar population only accounts for a small fraction of the total astrophysical neutrino flux. In this work we probe the production of high-energy neutrinos in the cores of active galactic nuclei (AGN), induced by accelerated cosmic rays in the accretion disk region. We present a likelihood analysis based on eight years of IceCube data, searching for a cumulative neutrino signal from three AGN samples created for this work. The neutrino emission is assumed to be proportional to the accretion disk luminosity estimated from the soft x-ray flux. Next to the observed soft x-ray flux, the objects for the three samples have been selected based on their radio emission and infrared color properties. For the largest sample in this search, an excess of high-energy neutrino events with respect to an isotropic background of atmospheric and astrophysical neutrinos is found, corresponding to a post-trial significance of 2.60σ. If interpreted as a genuine signal with the assumptions of a proportionality of x-ray and neutrino fluxes and a model for the subthreshold flux distribution, then this observation implies that at 100 TeV, 27%–100% of the observed neutrinos arise from particle acceleration in the core of AGN at 1σ confidence interval.

  • 11. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for quantum gravity using astrophysical neutrino flavour with IceCube2022In: Nature Physics, ISSN 1745-2473, E-ISSN 1745-2481, Vol. 18, no 11, p. 1287-1292Article in journal (Refereed)
    Abstract [en]

    Along their long propagation from production to detection, neutrinos undergo flavour conversions that convert their types or flavours. High-energy astrophysical neutrinos propagate unperturbed over a billion light years in vacuum and are sensitive to small effects caused by new physics. Effects of quantum gravity are expected to appear at the Planck energy scale. Such a high-energy universe would have existed only immediately after the Big Bang and is inaccessible by human technologies. On the other hand, quantum gravity effects may exist in our low-energy vacuum, but are suppressed by inverse powers of the Planck energy. Measuring the coupling of particles to such small effects is difficult via kinematic observables, but could be observable through flavour conversions. Here we report a search with the IceCube Neutrino Observatory, using astrophysical neutrino flavours to search for new space-time structure. We did not find any evidence of anomalous flavour conversion in the IceCube astrophysical neutrino flavour data. We apply the most stringent limits of any known technologies, down to 10-42 GeV-2 with Bayes factor greater than 10 on the dimension-six operators that parameterize the space-time defects. We thus unambiguously reach the parameter space of quantum-gravity-motivated physics.

  • 12. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Searches for connections between dark matter and high-energy neutrinos with IceCube2023In: Journal of Cosmology and Astroparticle Physics, E-ISSN 1475-7516, Vol. 2023, no 10, article id 003Article in journal (Refereed)
    Abstract [en]

    In this work, we present the results of searches for signatures of dark matter decay or annihilation into Standard Model particles, and secret neutrino interactions with dark matter. Neutrinos could be produced in the decay or annihilation of galactic or extragalactic dark matter. Additionally, if an interaction between dark matter and neutrinos exists then dark matter will interact with extragalactic neutrinos. In particular galactic dark matter will induce an anisotropy in the neutrino sky if this interaction is present. We use seven and a half years of the High-Energy Starting Event (HESE) sample data, which measures neutrinos in the energy range of approximately 60 TeV to 10 PeV, to study these phenomena. This all-sky event selection is dominated by extragalactic neutrinos. For dark matter of ∼ 1 PeV in mass, we constrain the velocity-averaged annihilation cross section to be smaller than 10-23 cm3/s for the exclusive μ+μ- channel and 10-22 cm3/s for the bb̅ channel. For the same mass, we constrain the lifetime of dark matter to be larger than 1028 s for all channels studied, except for decaying exclusively to bb̅ where it is bounded to be larger than 1027 s. Finally, we also search for evidence of astrophysical neutrinos scattering on galactic dark matter in two scenarios. For fermionic dark matter with a vector mediator, we constrain the dimensionless coupling associated with this interaction to be less than 0.1 for dark matter mass of 0.1 GeV and a mediator mass of 10-4 GeV. In the case of scalar dark matter with a fermionic mediator, we constrain the coupling to be less than 0.1 for dark matter and mediator masses below 1 MeV.

  • 13. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Searches for Neutrinos from Gamma-Ray Bursts Using the IceCube Neutrino Observatory2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 939, no 2, article id 116Article in journal (Refereed)
    Abstract [en]

    Gamma-ray bursts (GRBs) are considered as promising sources of ultra-high-energy cosmic rays (UHECRs) due to their large power output. Observing a neutrino flux from GRBs would offer evidence that GRBs are hadronic accelerators of UHECRs. Previous IceCube analyses, which primarily focused on neutrinos arriving in temporal coincidence with the prompt gamma-rays, found no significant neutrino excess. The four analyses presented in this paper extend the region of interest to 14 days before and after the prompt phase, including generic extended time windows and targeted precursor searches. GRBs were selected between 2011 May and 2018 October to align with the data set of candidate muon-neutrino events observed by IceCube. No evidence of correlation between neutrino events and GRBs was found in these analyses. Limits are set to constrain the contribution of the cosmic GRB population to the diffuse astrophysical neutrino flux observed by IceCube. Prompt neutrino emission from GRBs is limited to ≲1% of the observed diffuse neutrino flux, and emission on timescales up to 104 s is constrained to 24% of the total diffuse flux.

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  • 14. Abbasi, R.
    et al.
    Ahrens, Maryon
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Searching for High-energy Neutrino Emission from Galaxy Clusters with IceCube2022In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 938, no 2, article id L11Article in journal (Refereed)
    Abstract [en]

    Galaxy clusters have the potential to accelerate cosmic rays (CRs) to ultrahigh energies via accretion shocks or embedded CR acceleration sites. The CRs with energies below the Hillas condition will be confined within the cluster and eventually interact with the intracluster medium gas to produce secondary neutrinos and gamma rays. Using 9.5 yr of muon neutrino track events from the IceCube Neutrino Observatory, we report the results of a stacking analysis of 1094 galaxy clusters with masses ≳1014 M and redshifts between 0.01 and ∼1 detected by the Planck mission via the Sunyaev–Zel’dovich effect. We find no evidence for significant neutrino emission and report upper limits on the cumulative unresolved neutrino flux from massive galaxy clusters after accounting for the completeness of the catalog up to a redshift of 2, assuming three different weighting scenarios for the stacking and three different power-law spectra. Weighting the sources according to mass and distance, we set upper limits at a 90% confidence level that constrain the flux of neutrinos from massive galaxy clusters (≳1014 M) to be no more than 4.6% of the diffuse IceCube observations at 100 TeV, assuming an unbroken E−2.5 power-law spectrum.

  • 15. Abbasi, R.
    et al.
    Deoskar, K.
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, M.
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Constraining High-energy Neutrino Emission from Supernovae with IceCube2023In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 949, no 1, article id L12Article in journal (Refereed)
    Abstract [en]

    Core-collapse supernovae are a promising potential high-energy neutrino source class. We test for correlation between seven years of IceCube neutrino data and a catalog containing more than 1000 core-collapse supernovae of types IIn and IIP and a sample of stripped-envelope supernovae. We search both for neutrino emission from individual supernovae as well as for combined emission from the whole supernova sample, through a stacking analysis. No significant spatial or temporal correlation of neutrinos with the cataloged supernovae was found. All scenarios were tested against the background expectation and together yield an overall p-value of 93%; therefore, they show consistency with the background only. The derived upper limits on the total energy emitted in neutrinos are 1.7 x 10(48) erg for stripped-envelope supernovae, 2.8 x 10(48) erg for type IIP, and 1.3 x 10(49) erg for type IIn SNe, the latter disfavoring models with optimistic assumptions for neutrino production in interacting supernovae. We conclude that stripped-envelope supernovae and supernovae of type IIn do not contribute more than 14.6% and 33.9%, respectively, to the diffuse neutrino flux in the energy range of about [ 10(3)-10(5)] GeV, assuming that the neutrino energy spectrum follows a power-law with an index of -2.5. Under the same assumption, we can only constrain the contribution of type IIP SNe to no more than 59.9%. Thus, core-collapse supernovae of types IIn and stripped-envelope supernovae can both be ruled out as the dominant source of the diffuse neutrino flux under the given assumptions.

  • 16. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kovacevich, M.
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    A Search for Coincident Neutrino Emission from Fast Radio Bursts with Seven Years of IceCube Cascade Events2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 946, no 2, article id 80Article in journal (Refereed)
    Abstract [en]

    This paper presents the results of a search for neutrinos that are spatially and temporally coincident with 22 unique, nonrepeating fast radio bursts (FRBs) and one repeating FRB (FRB 121102). FRBs are a rapidly growing class of Galactic and extragalactic astrophysical objects that are considered a potential source of high-energy neutrinos. The IceCube Neutrino Observatory's previous FRB analyses have solely used track events. This search utilizes seven years of IceCube cascade events which are statistically independent of track events. This event selection allows probing of a longer range of extended timescales due to the low background rate. No statistically significant clustering of neutrinos was observed. Upper limits are set on the time-integrated neutrino flux emitted by FRBs for a range of extended time windows.

  • 17. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nisa, M. U.
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zimmerman, M.
    Search for Extended Sources of Neutrino Emission in the Galactic Plane with IceCube2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 956, no 1, article id 20Article in journal (Refereed)
    Abstract [en]

    The Galactic plane, harboring a diffuse neutrino flux, is a particularly interesting target in which to study potential cosmic-ray acceleration sites. Recent gamma-ray observations by HAWC and LHAASO have presented evidence for multiple Galactic sources that exhibit a spatially extended morphology and have energy spectra continuing beyond 100 TeV. A fraction of such emission could be produced by interactions of accelerated hadronic cosmic rays, resulting in an excess of high-energy neutrinos clustered near these regions. Using 10 years of IceCube data comprising track-like events that originate from charged-current muon neutrino interactions, we perform a dedicated search for extended neutrino sources in the Galaxy. We find no evidence for time-integrated neutrino emission from the potential extended sources studied in the Galactic plane. The most significant location, at 2.6σ post-trials, is a sized region coincident with the unidentified TeV gamma-ray source 3HWC J1951+266. We provide strong constraints on hadronic emission from several regions in the galaxy.

  • 18. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    A Search for IceCube Sub-TeV Neutrinos Correlated with Gravitational-wave Events Detected By LIGO/Virgo2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 959, no 2, article id 96Article in journal (Refereed)
    Abstract [en]

    The LIGO/Virgo collaboration published the catalogs GWTC-1, GWTC-2.1, and GWTC-3 containing candidate gravitational-wave (GW) events detected during its runs O1, O2, and O3. These GW events can be possible sites of neutrino emission. In this paper, we present a search for neutrino counterparts of 90 GW candidates using IceCube DeepCore, the low-energy infill array of the IceCube Neutrino Observatory. The search is conducted using an unbinned maximum likelihood method, within a time window of 1000 s, and uses the spatial and timing information from the GW events. The neutrinos used for the search have energies ranging from a few GeV to several tens of TeV. We do not find any significant emission of neutrinos, and place upper limits on the flux and the isotropic-equivalent energy emitted in low-energy neutrinos. We also conduct a binomial test to search for source populations potentially contributing to neutrino emission. We report a nondetection of a significant neutrino-source population with this test.

  • 19. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm Univ, Oskar Klein Ctr, Stockholm, Sweden.
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Constraints on Populations of Neutrino Sources from Searches in the Directions of IceCube Neutrino Alerts2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 951, no 1, article id 45Article in journal (Refereed)
    Abstract [en]

    Beginning in 2016, the IceCube Neutrino Observatory has sent out alerts in real time containing the information of high-energy (E & GSIM; 100 TeV) neutrino candidate events with moderate to high (& GSIM;30%) probability of astrophysical origin. In this work, we use a recent catalog of such alert events, which, in addition to events announced in real time, includes events that were identified retroactively and covers the time period of 2011-2020. We also search for additional, lower-energy neutrinos from the arrival directions of these IceCube alerts. We show how performing such an analysis can constrain the contribution of rare populations of cosmic neutrino sources to the diffuse astrophysical neutrino flux. After searching for neutrino emission coincident with these alert events on various timescales, we find no significant evidence of either minute-scale or day-scale transient neutrino emission or of steady neutrino emission in the direction of these alert events. This study also shows how numerous a population of neutrino sources has to be to account for the complete astrophysical neutrino flux. Assuming that sources have the same luminosity, an E (-2.5) neutrino spectrum, and number densities that follow star formation rates, the population of sources has to be more numerous than 7 x 10(-9) Mpc(-3). This number changes to 3 x 10(-7) Mpc(-3) if number densities instead have no cosmic evolution.

  • 20. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    IceCat-1: The IceCube Event Catalog of Alert Tracks2023In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 269, no 1, article id 25Article in journal (Refereed)
    Abstract [en]

    We present a catalog of likely astrophysical neutrino track-like events from the IceCube Neutrino Observatory. IceCube began reporting likely astrophysical neutrinos in 2016, and this system was updated in 2019. The catalog presented here includes events that were reported in real time since 2019, as well as events identified in archival data samples starting from 2011. We report 275 neutrino events from two selection channels as the first entries in the catalog, the IceCube Event Catalog of Alert Tracks, which will see ongoing extensions with additional alerts. The Gold and Bronze alert channels respectively provide neutrino candidates with a 50% and 30% probability of being astrophysical, on average assuming an astrophysical neutrino power-law energy spectral index of 2.19. For each neutrino alert, we provide the reconstructed energy, direction, false-alarm rate, probability of being astrophysical in origin, and likelihood contours describing the spatial uncertainty in the alert's reconstructed location. We also investigate a directional correlation of these neutrino events with gamma-ray and X-ray catalogs, including 4FGL, 3HWC, TeVCat, and Swift-BAT.

  • 21. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for Correlations of High-energy Neutrinos Detected in IceCube with Radio-bright AGN and Gamma-Ray Emission from Blazars2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 954, no 1, article id 75Article in journal (Refereed)
    Abstract [en]

    The IceCube Neutrino Observatory sends realtime neutrino alerts with a high probability of being astrophysical in origin. We present a new method to correlate these events and possible candidate sources using 2089 blazars from the Fermi-LAT 4LAC-DR2 catalog and with 3413 active galactic nuclei (AGNs) from the Radio Fundamental Catalog. No statistically significant neutrino emission was found in any of the catalog searches. The result suggests that a small fraction, <1%, of the studied AGNs emit neutrinos that pass the alert criteria, and is compatible with prior evidence for neutrino emission presented by IceCube and other authors from sources such as TXS 0506 + 056 and PKS 1502 + 106. We also present cross-checks to other analyses that claim a significant correlation using similar data samples.

  • 22. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for Galactic Core-collapse Supernovae in a Decade of Data Taken with the IceCube Neutrino Observatory2024In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 961, no 1, article id 84Article in journal (Refereed)
    Abstract [en]

    The IceCube Neutrino Observatory has been continuously taking data to search for s long neutrino bursts since 2007. Even if a Galactic core-collapse supernova is optically obscured or collapses to a black hole instead of exploding, it will be detectable via the MeV neutrino burst emitted during the collapse. We discuss a search for such events covering the time between 2008 April 17 and 2019 December 31. Considering the average data taking and analysis uptime of 91.7% after all selection cuts, this is equivalent to 10.735 yr of continuous data taking. In order to test the most conservative neutrino production scenario, the selection cuts were optimized for a model based on an 8.8 solar mass progenitor collapsing to an O–Ne–Mg core. Conservative assumptions on the effects of neutrino oscillations in the exploding star were made. The final selection cut was set to ensure that the probability to detect such a supernova within the Milky Way exceeds 99%. No such neutrino burst was found in the data after performing a blind analysis. Hence, a 90% C.L. upper limit on the rate of core-collapse supernovae out to distances of ≈25 kpc was determined to be 0.23 yr−1. For the more distant Magellanic Clouds, only high neutrino luminosity supernovae will be detectable by IceCube, unless external information on the burst time is available. We determined a model-independent limit by parameterizing the dependence on the neutrino luminosity and the energy spectrum.

  • 23. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Search for sub-TeV Neutrino Emission from Novae with IceCube-DeepCore2023In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 953, no 2, article id 160Article in journal (Refereed)
    Abstract [en]

    The understanding of novae, the thermonuclear eruptions on the surfaces of white dwarf stars in binaries, has recently undergone a major paradigm shift. Though the bolometric luminosity of novae was long thought to arise directly from photons supplied by the thermonuclear runaway, recent gigaelectronvolt (GeV) gamma-ray observations have supported the notion that a significant portion of the luminosity could come from radiative shocks. More recently, observations of novae have lent evidence that these shocks are acceleration sites for hadrons for at least some types of novae. In this scenario, a flux of neutrinos may accompany the observed gamma rays. As the gamma rays from most novae have only been observed up to a few GeV, novae have previously not been considered as targets for neutrino telescopes, which are most sensitive at and above teraelectronvolt (TeV) energies. Here, we present the first search for neutrinos from novae with energies between a few GeV and 10 TeV using IceCube-DeepCore, a densely instrumented region of the IceCube Neutrino Observatory with a reduced energy threshold. We search both for a correlation between gamma-ray and neutrino emission as well as between optical and neutrino emission from novae. We find no evidence for neutrino emission from the novae considered in this analysis and set upper limits for all gamma-ray detected novae.

  • 24. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zhelnin, P.
    Searches for Neutrinos from Large High Altitude Air Shower Observatory Ultra-high-energy γ-Ray Sources Using the IceCube Neutrino Observatory2023In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 945, no 1, article id L8Article in journal (Refereed)
    Abstract [en]

    Galactic PeV cosmic-ray accelerators (PeVatrons) are Galactic sources theorized to accelerate cosmic rays up to PeV in energy. The accelerated cosmic rays are expected to interact hadronically with nearby ambient gas or the interstellar medium, resulting in gamma-rays and neutrinos. Recently, the Large High Altitude Air Shower Observatory (LHAASO) identified 12 gamma-ray sources with emissions above 100 TeV, making them candidates for PeVatrons. While at these high energies the Klein-Nishina effect exponentially suppresses leptonic emission from Galactic sources, evidence for neutrino emission would unequivocally confirm hadronic acceleration. Here, we present the results of a search for neutrinos from these gamma-ray sources and stacking searches testing for excess neutrino emission from all 12 sources as well as their subcatalogs of supernova remnants and pulsar wind nebulae with 11 yr of track events from the IceCube Neutrino Observatory. No significant emissions were found. Based on the resulting limits, we place constraints on the fraction of gamma-ray flux originating from the hadronic processes in the Crab Nebula and LHAASO J2226+6057.

  • 25. Abbasi, R.
    et al.
    Deoskar, Kunal
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Finley, Chad
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hidvegi, Attila
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hultqvist, Klas
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Jansson, Matti
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zimmerman, M.
    Search for Continuous and Transient Neutrino Emission Associated with IceCube's Highest-energy Tracks: An 11 yr Analysis2024In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 964, no 1, article id 40Article in journal (Refereed)
    Abstract [en]

    IceCube alert events are neutrinos with a moderate-to-high probability of having astrophysical origin. In this study, we analyze 11 yr of IceCube data and investigate 122 alert events and a selection of high-energy tracks detected between 2009 and the end of 2021. This high-energy event selection (alert events + high-energy tracks) has an average probability of ≥0.5 of being of astrophysical origin. We search for additional continuous and transient neutrino emission within the high-energy events' error regions. We find no evidence for significant continuous neutrino emission from any of the alert event directions. The only locally significant neutrino emission is the transient emission associated with the blazar TXS 0506+056, with a local significance of 3σ, which confirms previous IceCube studies. When correcting for 122 test positions, the global p-value is 0.156 and compatible with the background hypothesis. We constrain the total continuous flux emitted from all 122 test positions at 100 TeV to be below 1.2 × 10−15 (TeV cm2 s)−1 at 90% confidence assuming an E−2 spectrum. This corresponds to 4.5% of IceCube's astrophysical diffuse flux. Overall, we find no indication that alert events in general are linked to lower-energetic continuous or transient neutrino emission.

  • 26. Abdalla, Elcio
    et al.
    Arendse, Nikki
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Di Valentino, Eleonora
    Niedermann, Florian
    Stockholm University, Nordic Institute for Theoretical Physics (Nordita).
    Zumalacárregui, Miguel
    Cosmology intertwined: A review of the particle physics, astrophysics, and cosmology associated with the cosmological tensions and anomalies2022In: Journal of High Energy Astrophysics, ISSN 2214-4048, E-ISSN 2214-4056, Vol. 34, p. 49-211Article, review/survey (Refereed)
    Abstract [en]

    The standard Λ Cold Dark Matter (ΛCDM) cosmological model provides a good description of a wide range of astrophysical and cosmological data. However, there are a few big open questions that make the standard model look like an approximation to a more realistic scenario yet to be found. In this paper, we list a few important goals that need to be addressed in the next decade, taking into account the current discordances between the different cosmological probes, such as the disagreement in the value of the Hubble constant H0, the σ8–S8 tension, and other less statistically significant anomalies. While these discordances can still be in part the result of systematic errors, their persistence after several years of accurate analysis strongly hints at cracks in the standard cosmological scenario and the necessity for new physics or generalisations beyond the standard model. In this paper, we focus on the 5.0σ tension between the Planck CMB estimate of the Hubble constant H0 and the SH0ES collaboration measurements. After showing the H0 evaluations made from different teams using different methods and geometric calibrations, we list a few interesting new physics models that could alleviate this tension and discuss how the next decade's experiments will be crucial. Moreover, we focus on the tension of the Planck CMB data with weak lensing measurements and redshift surveys, about the value of the matter energy density Ωm, and the amplitude or rate of the growth of structure (σ8,fσ8). We list a few interesting models proposed for alleviating this tension, and we discuss the importance of trying to fit a full array of data with a single model and not just one parameter at a time. Additionally, we present a wide range of other less discussed anomalies at a statistical significance level lower than the H0–S8 tensions which may also constitute hints towards new physics, and we discuss possible generic theoretical approaches that can collectively explain the non-standard nature of these signals. Finally, we give an overview of upgraded experiments and next-generation space missions and facilities on Earth that will be of crucial importance to address all these open questions.

  • 27. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Allafort, A.
    Amin, M. A.
    Baldini, L.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Blandford, R. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brigida, M.
    Buehler, R.
    Bulmash, D.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Cavazzuti, E.
    Cecchi, C.
    Charles, E.
    Cheung, C. C.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). The Royal Swedish Academy of Sciences, Sweden.
    Corbet, R. H. D.
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Dermer, C. D.
    Drell, P. S.
    Drlica-Wagner, A.
    Favuzzi, C.
    Finke, J.
    Focke, W. B.
    Fukazawa, Y.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Hadasch, D.
    Hayashida, M.
    Hays, E.
    Hughes, R. E.
    Inoue, Y.
    Jackson, M. S.
    Jogler, T.
    Johannesson, G.
    Johnson, A. S.
    Kamae, T.
    Knoedlseder, J.
    Kuss, M.
    Lande, J.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Mazziotta, M. N.
    Mehault, J.
    Michelson, P. F.
    Mizuno, T.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nemmen, R.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Paneque, D.
    Perkins, J. S.
    Pesce-Rollins, M.
    Piron, F.
    Pivato, G.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reyes, L. C.
    Ritz, S.
    Romoli, C.
    Roth, M.
    Parkinson, P. M. Saz
    Sgro, C.
    Siskind, E. J.
    Spandre, G.
    Spinelli, P.
    Takahashi, H.
    Takeuchi, Y.
    Tanaka, T.
    Thayer, J. G.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Tinivella, M.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Tronconi, V.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Vianello, G.
    Vitale, V.
    Waite, A. P.
    Werner, M.
    Winer, B. L.
    Wood, K. S.
    GAMMA-RAY FLARING ACTIVITY FROM THE GRAVITATIONALLY LENSED BLAZAR PKS 1830-211 OBSERVED BY Fermi LAT2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 799, no 2, article id 143Article in journal (Refereed)
    Abstract [en]

    The Large Area Telescope ( LAT) on board the FermiGamma- ray Space Telescope routinely detects the MeV- peaked flat- spectrum radio quasar PKS 1830- 211 ( z = 2.507). Its apparent isotropic. - ray luminosity ( E > 100 MeV), averaged over 3 years of observations and peaking on 2010 October 14/ 15 at 2.9 x 1050 erg s- 1, makes it among the brightest high- redshift Fermi blazars. No published model with a single lens can account for all of the observed characteristics of this complex system. Based on radio observations, one expects time- delayed variability to follow about 25 days after a primary flare, with flux about a factor of 1.5 less. Two large. - ray flares of PKS 1830- 211 have been detected by the LAT in the considered period, and no substantial evidence for such a delayed activity was found. This allows us to place a lower limit of about 6 on the. - ray flux ratio between the two lensed images. Swift XRT observations from a dedicated Target of Opportunity program indicate a hard spectrum with no significant correlation of X- ray flux with the. - ray variability. The spectral energy distribution can be modeled with inverse Compton scattering of thermal photons from the dusty torus. The implications of the LAT data in terms of variability, the lack of evident delayed flare events, and different radio and. - ray flux ratios are discussed. Microlensing effects, absorption, size and location of the emitting regions, the complex mass distribution of the system, an energy- dependent inner structure of the source, and flux suppression by the lens galaxy for one image path may be considered as hypotheses for understanding our results.

  • 28. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Ampe, J.
    Anderson, B.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Bagagli, R.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bartelt, J.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bédérède, D.
    Bellardi, F.
    Bellazzini, R.
    Belli, F.
    Berenji, B.
    Bisello, D.
    Bissaldi, E.
    Bloom, E. D.
    Bogaert, G.
    Bogart, J. R.
    Bonamente, E.
    Borgland, A. W.
    Bourgeois, P.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Busetto, G.
    Caliandro, G. A.
    Cameron, R. A.
    Campell, M.
    Caraveo, P. A.
    Carius, S.
    Carlson, P.
    Casandjian, J. M.
    Cavazzuti, E.
    Ceccanti, M.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Chipaux, R.
    Cillis, A. N.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Condamoor, S.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Corbet, R.
    Cutini, S.
    Davis, D. S.
    Deklotz, M.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Dizon, P.
    Dormody, M.
    Do Couto E Silva, E.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Edmonds, Y.
    Fabiani, D.
    Farnier, C.
    Favuzzi, C.
    Ferrara, E. C.
    Ferreira, O.
    Fewtrell, Z.
    Flath, D. L.
    Fleury, P.
    Focke, W. B.
    Fouts, K.
    Frailis, M.
    Freytag, D.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Goodman, J.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hakimi, M.
    Haller, G.
    Hanabata, Y.
    Hart, P. A.
    Hascall, P.
    Hays, E.
    Huffer, M.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, T. J.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kavelaars, A.
    Kelly, H.
    Kerr, M.
    Klamra, W.
    Knödlseder, J.
    Kocian, M. L.
    Kuehn, F.
    Kuss, M.
    Latronico, L.
    Lavalley, C.
    Leas, B.
    Lee, B.
    Lee, S.-H.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Lung, D. K.
    Madejski, G. M.
    Makeev, A.
    Marangelli, B.
    Marchetti, M.
    Massai, M. M.
    May, D.
    Mazzenga, G.
    Mazziotta, M. N.
    McEnery, J. E.
    McGlynn, S.
    Meurer, C.
    Michelson, P. F.
    Minuti, M.
    Mirizzi, N.
    Mitra, P.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Mongelli, M.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nelson, D.
    Nilsson, L.
    Nishino, S.
    Nolan, P. L.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paccagnella, A.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Picozza, P.
    Pinchera, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Rapposelli, E.
    Raynor, W.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Reyes, L. C.
    Ritz, S.
    Robinson, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Ryde, F.
    Sacchetti, A.
    Sadrozinski, H. F.-W.
    Saggini, N.
    Sanchez, D.
    Sander, A.
    Sapozhnikov, L.
    Saxton, O. H.
    Saz Parkinson, P. M.
    Sellerholm, A.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Physics.
    Sgrò, C.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Starck, J.-L.
    Stephens, T. E.
    Strickman, M. S.
    Strong, A. W.
    Sugizaki, M.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Tenze, A.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Tibolla, O.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Turri, M.
    Usher, T. L.
    Vilchez, N.
    Virmani, N.
    Vitale, V.
    Wai, L. L.
    Waite, A. P.
    Wang, P.
    Winer, B. L.
    Wood, D. L.
    Wood, K. S.
    Yasuda, H.
    Ylinen, T.
    Ziegler, M.
    The on-orbit calibration of the Fermi Large Area Telescope2009In: Astroparticle physics, ISSN 0927-6505, E-ISSN 1873-2852, Vol. 32, no 3-4, p. 193-219Article in journal (Refereed)
    Abstract [en]

    The Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope began its on-orbit operations on June 23, 2008. Calibrations, defined in a generic sense, correspond to synchronization of trigger signals, optimization of delays for latching data, determination of detector thresholds, gains and responses, evaluation of the perimeter of the South Atlantic Anomaly (SAA), measurements of live time, of absolute time, and internal and spacecraft boresight alignments. Here we describe on-orbit calibration results obtained using known astrophysical sources, galactic cosmic rays, and charge injection into the front-end electronics of each detector. Instrument response functions will be described in a separate publication. This paper demonstrates the stability of calibrations and describes minor changes observed since launch. These results have been used to calibrate the LAT datasets to be publicly released in August 2009.

  • 29. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Antolini, E.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Cannon, A.
    Caraveo, P. A.
    Carrigan, S.
    Casandjian, J. M.
    Cecchi, C.
    Celik, Oe
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Costamante, L.
    Cutini, S.
    Dermer, C. D.
    de Palma, F.
    Donato, D.
    do Couto e Silva, E.
    Drell, P. S.
    Dubois, R.
    Escande, L.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Focke, W. B.
    Fortin, P.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Guiriec, S.
    Hadasch, D.
    Hayashida, M.
    Hays, E.
    Hughes, R. E.
    Itoh, R.
    Johannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Knoedlseder, J.
    Kuss, M.
    Lande, J.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Latronico, L.
    Lee, S. -H
    Garde, Maja Llena
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Makeev, A.
    Mazziotta, M. N.
    McEnery, J. E.
    Mehault, J.
    Michelson, P. F.
    Mizuno, T.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Naumann-Godo, M.
    Nishino, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Okumura, A.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Roth, M.
    Sadrozinski, H. F. -W
    Sanchez, D.
    Sander, A.
    Schinzel, F. K.
    Sgro, C.
    Siskind, E. J.
    Smith, P. D.
    Sokolovsky, K. V.
    Spandre, G.
    Spinelli, P.
    Strickman, M. S.
    Suson, D. J.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uehara, T.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wallace, E.
    Wang, P.
    Winer, B. L.
    Wood, K. S.
    SUBYang, Z.
    Ylinen, T.
    Ziegler, M.
    Berdyugin, A.
    Boettcher, M.
    Carraminana, A.
    Carrasco, L.
    de la Fuente, E.
    Diltz, C.
    Hovatta, T.
    Kadenius, V.
    Kovalev, Y. Y.
    Lahteenmaki, A.
    Lindfors, E.
    Marscher, A. P.
    Nilsson, K.
    Pereira, D.
    Reinthal, R.
    Roustazadeh, P.
    Savolainen, T.
    Sillanpaa, A.
    Takalo, L. O.
    Tornikoski, M.
    THE FIRST FERMI MULTIFREQUENCY CAMPAIGN ON BL LACERTAE: CHARACTERIZING THE LOW-ACTIVITY STATE OF THE EPONYMOUS BLAZAR2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 730, no 2, p. 101-Article in journal (Refereed)
    Abstract [en]

    We report on observations of BL Lacertae during the first 18 months of Fermi LAT science operations and present results from a 48 day multifrequency coordinated campaign from 2008 August 19 to 2008 October 7. The radio to gamma-ray behavior of BL Lac is unveiled during a low-activity state thanks to the coordinated observations of radio-band (Metsahovi and VLBA), near-IR/optical (Tuorla, Steward, OAGH, and MDM), and X-ray (RXTE and Swift) observatories. No variability was resolved in gamma rays during the campaign, and the brightness level was 15 times lower than the level of the 1997 EGRET outburst. Moderate and uncorrelated variability has been detected in UV and X-rays. The X-ray spectrum is found to be concave, indicating the transition region between the low- and high-energy components of the spectral energy distribution (SED). VLBA observation detected a synchrotron spectrum self-absorption turnover in the innermost part of the radio jet appearing to be elongated and inhomogeneous, and constrained the average magnetic field there to be less than 3 G. Over the following months, BL Lac appeared variable in gamma rays, showing flares (in 2009 April and 2010 January). There is no evidence for the correlation of gamma rays with the optical flux monitored from the ground in 18 months. The SED may be described by a single-zone or a two-zone synchrotron self-Compton (SSC) model, but a hybrid SSC plus external radiation Compton model seems to be preferred based on the observed variability and the fact that it provides a fit closest to equipartition.

  • 30. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Asano, K.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bhat, P. N.
    Bissaldi, E.
    Bloom, E. D.
    Bonamente, E.
    Bonnell, J.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Briggs, M. S.
    Brigida, M.
    Bruel, P.
    Burgess, J. M.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Çelik, Ö.
    Chaplin, V.
    Charles, E.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Connaughton, V.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Cutini, S.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Dingus, B. L.
    Do Couto E Silva, E.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Fishman, G.
    Focke, W. B.
    Foschini, L.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Gibby, L.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Granot, J.
    Greiner, J.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Grupe, D.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hoversten, E. A.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Kippen, R. M.
    Knödlseder, J.
    Kocevski, D.
    Kouveliotou, C.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McBreen, S.
    McEnery, J. E.
    McGlynn, S.
    Mészáros, P.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paciesas, W. S.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Petrosian, V.
    Piron, F.
    Porter, T. A.
    Preece, R.
    Rainò, S.
    Ramirez-Ruiz, E.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Schalk, T. L.
    Sgrò, C.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Stamatikos, M.
    Stecker, F. W.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Toma, K.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Uehara, T.
    Usher, T. L.
    van der Horst, A. J.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    von Kienlin, A.
    Waite, A. P.
    Wang, P.
    Wilson-Hodge, C.
    Winer, B. L.
    Wood, K. S.
    Wu, X. F.
    Yamazaki, R.
    Ylinen, T.
    Ziegler, M.
    the Fermi LAT Collaboration,
    A limit on the variation of the speed of light arising from quantum gravity effects2009In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 462, no 7271, p. 331-334Article in journal (Refereed)
    Abstract [en]

    A cornerstone of Einstein’s special relativity is Lorentz invariance—the postulate that all observers measure exactly the same speed of light in vacuum, independent of photon-energy. While special relativity assumes that there is no fundamental length-scale associated with such invariance, there is a fundamental scale (the Planck scale, lPlanck~1.62×10-33cm or EPlanck = MPlanckc2~1.22×1019GeV), at which quantum effects are expected to strongly affect the nature of space–time. There is great interest in the (not yet validated) idea that Lorentz invariance might break near the Planck scale. A key test of such violation of Lorentz invariance is a possible variation of photon speed with energy. Even a tiny variation in photon speed, when accumulated over cosmological light-travel times, may be revealed by observing sharp features in γ-ray burst (GRB) light-curves. Here we report the detection of emission up to ~31GeV from the distant and short GRB090510. We find no evidence for the violation of Lorentz invariance, and place a lower limit of 1.2EPlanck on the scale of a linear energy dependence (or an inverse wavelength dependence), subject to reasonable assumptions about the emission (equivalently we have an upper limit of lPlanck/1.2 on the length scale of the effect). Our results disfavour quantum-gravity theories in which the quantum nature of space–time on a very small scale linearly alters the speed of light.

  • 31. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Asano, K.
    Atwood, W. B.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bhat, P. N.
    Bissaldi, E.
    Blandford, R. D.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Briggs, M. S.
    Brigida, M.
    Bruel, P.
    Burgess, J. M.
    Burrows, D. N.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Çelik, Ö.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Connaughton, V.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Cutini, S.
    d'Elia, V.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Dingus, B. L.
    Silva, E. do Couto e.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Fishman, G.
    Focke, W. B.
    Fortin, P.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gehrels, N.
    Germani, S.
    Giavitto, G.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Goldstein, A.
    Granot, J.
    Greiner, J.
    Grenier, I. A.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Horan, D.
    Hughes, R. E.
    Jackson, M. S.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Kippen, R. M.
    Knödlseder, J.
    Kocevski, D.
    Komin, N.
    Kouveliotou, C.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McBreen, S.
    McEnery, J. E.
    McGlynn, S.
    Meegan, C.
    Mészáros, P.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paciesas, W. S.
    Paneque, D.
    Panetta, J. H.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Petrosian, V.
    Piron, F.
    Porter, T. A.
    Preece, R.
    Rainò, S.
    Rando, R.
    Rau, A.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Roming, P. W. A.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Schalk, T. L.
    Sgrò, C.
    Siskind, E. J.
    Smith, P. D.
    Spinelli, P.
    Stamatikos, M.
    Stecker, F. W.
    Stratta, G.
    Strickman, M. S.
    Suson, D. J.
    Swenson, C. A.
    Tajima, H.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Uehara, T.
    Usher, T. L.
    van der Horst, A. J.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    von Kienlin, A.
    Waite, A. P.
    Wang, P.
    Wilson-Hodge, C.
    Winer, B. L.
    Wood, K. S.
    Yamazaki, R.
    Ylinen, T.
    Ziegler, M.
    Fermi Observations of GRB 090902B: A Distinct Spectral Component in the Prompt and Delayed Emission2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 706, no 1, p. L138-L144Article in journal (Refereed)
    Abstract [en]

    We report on the observation of the bright, long gamma-ray burst (GRB), GRB 090902B, by the Gamma-ray Burst Monitor (GBM) and Large Area Telescope (LAT) instruments on-board the Fermi observatory. This was one of the brightest GRBs to have been observed by the LAT, which detected several hundred photons during the prompt phase. With a redshift of z = 1.822, this burst is among the most luminous detected by Fermi. Time-resolved spectral analysis reveals a significant power-law component in the LAT data that is distinct from the usual Band model emission that is seen in the sub-MeV energy range. This power-law component appears to extrapolate from the GeV range to the lowest energies and is more intense than the Band component, both below ~50 keV and above 100 MeV. The Band component undergoes substantial spectral evolution over the entire course of the burst, while the photon index of the power-law component remains constant for most of the prompt phase, then hardens significantly toward the end. After the prompt phase, power-law emission persists in the LAT data as late as 1 ks post-trigger, with its flux declining as t –1.5. The LAT detected a photon with the highest energy so far measured from a GRB, 33.4+2.7 –3.5 GeV. This event arrived 82 s after the GBM trigger and ~50 s after the prompt phase emission had ended in the GBM band. We discuss the implications of these results for models of GRB emission and for constraints on models of the extragalactic background light

  • 32. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwoo, W. B.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R. D.
    Bonamente, E.
    Borgland, A. W.
    Bottacini, E.
    Bouvier, A.
    Bregeon, J.
    Brigida, M.
    Bruel, P.
    Buehler, R.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Charles, E.
    Chekhtman, A.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cutini, S.
    D'Ammando, F.
    de Angelis, A.
    de Palma, F.
    Dermer, C. D.
    Digel, S. W.
    Silva, E. do Couto E
    Drell, P. S.
    Drlica-Wagner, A.
    Dubois, R.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Fortin, P.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Gomez-Vargas, G. A.
    Grenier, I. A.
    Grove, J. E.
    Guiriec, S.
    Hadasch, D.
    Hays, E.
    Hill, A. B.
    Horan, D.
    Hou, X.
    Hughes, R. E.
    Iafrate, G.
    Jackson, M. S.
    Johannesson, G.
    Johnson, A. S.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Knoedlseder, J.
    Kuss, M.
    Lande, J.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Mazziotta, M. N.
    McEnery, J. E.
    Mehault, J.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Naumann-Godo, M.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Okumura, A.
    Omodei, N.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pesce-Rollins, M.
    Pierbattista, M.
    Piron, F.
    Pivato, G.
    Poon, H.
    Porter, T. A.
    Prokhorov, D.
    Raino, S.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Rochester, L. S.
    Roth, M.
    Sadrozinski, H. F. -W
    Sanchez, D. A.
    Sbarra, C.
    Schalk, T. L.
    Sgro, C.
    Share, G. H.
    Siskind, E. J.
    Spandre, G.
    Spinelli, P.
    Stawarz, L.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. G.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Tinivella, M.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Vianello, G.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Winer, B. L.
    Wood, D. L.
    Wood, K. S.
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zimmer, Stephan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    FERMI OBSERVATIONS OF gamma-RAY EMISSION FROM THE MOON2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 758, no 2, p. 140-Article in journal (Refereed)
    Abstract [en]

    We report on the detection of high-energy gamma-ray emission from the Moon during the first 24 months of observations by the Fermi Large Area Telescope (LAT). This emission comes from particle cascades produced by cosmic-ray (CR) nuclei and electrons interacting with the lunar surface. The differential spectrum of the Moon is soft and can be described as a log-parabolic function with an effective cutoff at 2-3 GeV, while the average integral flux measured with the LAT from the beginning of observations in 2008 August to the end of 2010 August is F(> 100 MeV) = (1.04 +/- 0.01 [statistical error] +/- 0.1 [systematic error]) x 10(-6) cm(-2) s(-1). This flux is about a factor 2-3 higher than that observed between 1991 and 1994 by the EGRET experiment on board the Compton Gamma Ray Observatory, F(> 100 MeV) approximate to 5 x 10(-7) cm-2 s-1, when solar activity was relatively high. The higher gamma-ray flux measured by Fermi is consistent with the deep solar minimum conditions during the first 24 months of the mission, which reduced effects of heliospheric modulation, and thus increased the heliospheric flux of Galactic CRs. A detailed comparison of the light curve with McMurdo Neutron Monitor rates suggests a correlation of the trends. The Moon and the Sun are so far the only known bright emitters of gamma-rays with fast celestial motion. Their paths across the sky are projected onto the Galactic center and high Galactic latitudes as well as onto other areas crowded with high-energy gamma-ray sources. Analysis of the lunar and solar emission may thus be important for studies of weak and transient sources near the ecliptic.

  • 33. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Caliandro, G. A.
    Cameron, R. A.
    Camilo, F.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cognard, I.
    Cohen-Tanugi, J.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    de Angelis, A.
    de Palma, F.
    Dormody, M.
    Silva, E. do Couto e.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Frailis, M.
    Freire, P. C. C.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gehrels, N.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Halpern, J.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hobbs, G.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, T. J.
    Johnson, W. N.
    Johnston, S.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kramer, M.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Lyne, A. G.
    Makeev, A.
    Manchester, R. N.
    Marelli, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Norris, J. P.
    Noutsos, A.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Ransom, S. M.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Stappers, B. W.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Theureau, G.
    Thompson, D. J.
    Thorsett, S. E.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Uchiyama, Y.
    Usher, T. L.
    Van Etten, A.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Wang, N.
    Watters, K.
    Weltevrede, P.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Fermi Large Area Telescope Detection of Pulsed γ-rays from the Vela-like Pulsars PSR J1048–5832 and PSR J2229+61142009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 706, no 2, p. 1331-1340Article in journal (Refereed)
    Abstract [en]

    We report the detection of γ-ray pulsations (>=0.1 GeV) from PSR J2229+6114 and PSR J1048–5832, the latter having been detected as a low-significance pulsar by EGRET. Data in the γ-ray band were acquired by the Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope, while the radio rotational ephemerides used to fold the γ-ray light curves were obtained using the Green Bank Telescope, the Lovell telescope at Jodrell Bank, and the Parkes Telescope. The two young radio pulsars, located within the error circles of the previously unidentified EGRET sources 3EG J1048–5840 and 3EG J2227+6122, present spin-down characteristics similar to the Vela pulsar. PSR J1048–5832 shows two sharp peaks at phases 0.15 ± 0.01 and 0.57 ± 0.01 relative to the radio pulse confirming the EGRET light curve, while PSR J2229+6114 presents a very broad peak at phase 0.49 ± 0.01. The γ-ray spectra above 0.1 GeV of both pulsars are fit with power laws having exponential cutoffs near 3 GeV, leading to integral photon fluxes of (2.19 ± 0.22 ± 0.32) × 10–7 cm–2 s–1 for PSR J1048–5832 and (3.77 ± 0.22 ± 0.44) × 10–7 cm–2 s–1 for PSR J2229+6114. The first uncertainty is statistical and the second is systematic. PSR J1048–5832 is one of the two LAT sources which were entangled together as 3EG J1048–5840. These detections add to the growing number of young γ-ray pulsars that make up the dominant population of GeV γ-ray sources in the Galactic plane.

  • 34. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Çelik, Ö.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Cutini, S.
    de Angelis, A.
    de Palma, F.
    Di Bernardo, G.
    Silva, E. do Couto e.
    Drell, P. S.
    Drlica-Wagner, A.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Focke, W. B.
    Fortin, P.
    Foschini, L.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giavitto, G.
    Giebels, B.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Hayashida, M.
    Hays, E.
    Horan, D.
    Hughes, R. E.
    Jackson, M. S.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McConville, W.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Reyes, L. C.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Schalk, T. L.
    Sellerholm, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Sgrò, C.
    Shaw, M. S.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Tanaka, Y.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Fermi Observations of TeV-Selected Active Galactic Nuclei2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 2, p. 1310-1333Article in journal (Refereed)
    Abstract [en]

    We report on observations of TeV-selected active galactic nuclei (AGNs) made during the first 5.5 months of observations with the Large Area Telescope (LAT) on-board the Fermi Gamma-ray Space Telescope (Fermi). In total, 96 AGNs were selected for study, each being either (1) a source detected at TeV energies (28 sources) or (2) an object that has been studied with TeV instruments and for which an upper limit has been reported (68 objects). The Fermi observations show clear detections of 38 of these TeV-selected objects, of which 21 are joint GeV-TeV sources, and 29 were not in the third EGRET catalog. For each of the 38 Fermi-detected sources, spectra and light curves are presented. Most can be described with a power law of spectral index harder than 2.0, with a spectral break generally required to accommodate the TeV measurements. Based on an extrapolation of the Fermi spectrum, we identify sources, not previously detected at TeV energies, which are promising targets for TeV instruments. Evidence for systematic evolution of the γ-ray spectrum with redshift is presented and discussed in the context of interaction with the extragalactic background light.

  • 35. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Çelik, Ö.
    Charles, E.
    Chaty, S.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Corbel, S.
    Corbet, R.
    Cutini, S.
    Dermer, C. D.
    de Angelis, A.
    de Luca, A.
    de Palma, F.
    Digel, S. W.
    Dormody, M.
    do Couto e Silva, E.
    Drell, P. S.
    Dubois, R.
    Dubus, G.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hill, A. B.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, T. J.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Larsson, S.
    Stockholm University, Faculty of Science, Department of Physics.
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Marelli, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Nuss, E.
    Ohsugi, T.
    Okumura, A.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Ray, P. S.
    Razzano, M.
    Rea, N.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Shaw, M. S.
    Sierpowska-Bartosik, A.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Striani, E.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Fermi LAT Observations of LS I +61°303: First Detection of an Orbital Modulation in GeV Gamma Rays2009In: Astrophysical Journal Letters, Vol. 701, no 2, p. L123-L128Article in journal (Refereed)
    Abstract [en]

    This Letter presents the first results from the observations of LS I +61°303 using Large Area Telescope data from the Fermi Gamma-Ray Space Telescope between 2008 August and 2009 March. Our results indicate variability that is consistent with the binary period, with the emission being modulated at 26.6 ± 0.5 days. This constitutes the first detection of orbital periodicity in high-energy gamma rays (20 MeV-100 GeV, HE). The light curve is characterized by a broad peak after periastron, as well as a smaller peak just before apastron. The spectrum is best represented by a power law with an exponential cutoff, yielding an overall flux above 100 MeV of 0.82 ± 0.03(stat) ± 0.07(syst) 10-6 ph cm-2 s-1, with a cutoff at 6.3 ± 1.1(stat) ± 0.4(syst) GeV and photon index Γ = 2.21 ± 0.04(stat) ± 0.06(syst). There is no significant spectral change with orbital phase. The phase of maximum emission, close to periastron, hints at inverse Compton scattering as the main radiation mechanism. However, previous very high-energy gamma ray (>100 GeV, VHE) observations by MAGIC and VERITAS show peak emission close to apastron. This and the energy cutoff seen with Fermi suggest that the link between HE and VHE gamma rays is nontrivial.

  • 36. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R. D.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Çelik, Ö.
    Chaty, S.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Corbel, S.
    Corbet, R.
    Cutini, S.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Silva, E. do Couto e.
    Drell, P. S.
    Dubois, R.
    Dubus, G.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Fortin, P.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hill, A. B.
    Horan, D.
    Hughes, R. E.
    Jackson, M. S.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, T. J.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kuehn, F.
    Kuss, M.
    Lande, J.
    Larsson, S.
    Stockholm University, Faculty of Science, Department of Physics.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Marelli, M.
    Mazziotta, M. N.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Ray, P. S.
    Razzano, M.
    Rea, N.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Sierpowska-Bartosik, A.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Tanaka, Y.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Venter, C.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wallace, E.
    Wang, P.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Fermi/LAT observations of LS 50392009In: Astrophysical Journal Letters, ISSN 05717248, Vol. 706, no 1, p. L56-L61Article in journal (Refereed)
    Abstract [en]

    The first results from observations of the high-mass X-ray binary LS 5039 using the Fermi Gamma-ray Space Telescope data between 2008 August and 2009 June are presented. Our results indicate variability that is consistent with the binary period, with the emission being modulated with a period of 3.903 ± 0.005 days; the first detection of this modulation at GeV energies. The light curve is characterized by a broad peak around superior conjunction in agreement with inverse Compton scattering models. The spectrum is represented by a power law with an exponential cutoff, yielding an overall flux (100 MeV-300 GeV) of 4.9 ± 0.5(stat) ± 1.8(syst) ×10–7 photon cm–2 s–1, with a cutoff at 2.1 ± 0.3(stat) ± 1.1(syst) GeV and photon index Γ = 1.9 ± 0.1(stat) ± 0.3(syst). The spectrum is observed to vary with orbital phase, specifically between inferior and superior conjunction. We suggest that the presence of a cutoff in the spectrum may be indicative of magnetospheric emission similar to the emission seen in many pulsars by Fermi.

  • 37. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R. D.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Cannon, A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Çelik, Ö.
    Charles, E.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Colafrancesco, S.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Costamante, L.
    Cutini, S.
    Davis, D. S.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Donato, D.
    Silva, E. do Couto e.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Edmonds, Y.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Finke, J.
    Focke, W. B.
    Fortin, P.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Georganopoulos, M.
    Germani, S.
    Giebels, B.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Horan, D.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, R. P.
    Johnson, T. J.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mazziotta, M. N.
    McConville, W.
    McEnery, J. E.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sambruna, R.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Shaw, M. S.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Tanaka, T.
    Taylor, G. B.
    Thayer, J. B.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Vilchez, N.
    Waite, A. P.
    Wang, P.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Harris, D. E.
    Massaro, F.
    Stawarz, Ł.
    Fermi Large Area Telescope Gamma-Ray Detection of the Radio Galaxy M872009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 1, p. 55-60Article in journal (Refereed)
    Abstract [en]

    We report the Fermi Large Area Telescope (LAT) discovery of high-energy (MeV/GeV) γ-ray emission positionally consistent with the center of the radio galaxy M87, at a source significance of over 10σ in 10 months of all-sky survey data. Following the detections of Cen A and Per A, this makes M87 the third radio galaxy seen with the LAT. The faint point-like γ-ray source has a >100 MeV flux of 2.45 (±0.63) × 10–8 photons cm–2 s–1 (photon index = 2.26 ± 0.13) with no significant variability detected within the LAT observation. This flux is comparable with the previous EGRET upper limit (<2.18 × 10–8 photons cm–2 s–1, 2σ), thus there is no evidence for a significant MeV/GeV flare on decade timescales. Contemporaneous Chandra and Very Long Baseline Array data indicate low activity in the unresolved X-ray and radio core relative to previous observations, suggesting M87 is in a quiescent overall level over the first year of Fermi-LAT observations. The LAT γ-ray spectrum is modeled as synchrotron self-Compton (SSC) emission from the electron population producing the radio-to-X-ray emission in the core. The resultant SSC spectrum extrapolates smoothly from the LAT band to the historical-minimum TeV emission. Alternative models for the core and possible contributions from the kiloparsec-scale jet in M87 are considered, and cannot be excluded.

  • 38. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Baughman, B. M.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Çelik, Ö.
    Celotti, A.
    Chekhtman, A.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Collmar, W.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Costamante, L.
    Cutini, S.
    de Angelis, A.
    de Palma, F.
    Silva, E. Do Couto e.
    Drell, P. S.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Fortin, P.
    Foschini, L.
    Frailis, M.
    Fuhrmann, L.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Hays, E.
    Hughes, R. E.
    Jackson, M. S.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kadler, M.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocian, M. L.
    Kuss, M.
    Lande, J.
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Max-Moerbeck, W.
    Mazziotta, M. N.
    McConville, W.
    McEnery, J. E.
    McGlynn, S.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Nestoras, I.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Parent, D.
    Pavlidou, V.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Rainò, S.
    Rando, R.
    Razzano, M.
    Readhead, A.
    Reimer, O.
    Reposeur, T.
    Richards, J. L.
    Rodriguez, A. Y.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Shaw, M. S.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Strickman, M. S.
    Suson, D. J.
    Tagliaferri, G.
    Tajima, H.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Tibolla, O.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Wehrle, A. E.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Zensus, J. A.
    Ziegler, M.
    The Fermi/LAT Collaboration,
    Angelakis, E.
    Bailyn, C.
    Bignall, H.
    Blanchard, J.
    Bonning, E. W.
    Buxton, M.
    Canterna, R.
    Carramiñana, A.
    Carrasco, L.
    Colomer, F.
    Doi, A.
    Ghisellini, G.
    Hauser, M.
    Hong, X.
    Isler, J.
    Kino, M.
    Kovalev, Y. Y.
    Kovalev, Yu. A.
    Krichbaum, T. P.
    Kutyrev, A.
    Lahteenmaki, A.
    van Langevelde, H. J.
    Lister, M. L.
    Macomb, D.
    Maraschi, L.
    Marchili, N.
    Nagai, H.
    Paragi, Z.
    Phillips, C.
    Pushkarev, A. B.
    Recillas, E.
    Roming, P.
    Sekido, M.
    Stark, M. A.
    Szomoru, A.
    Tammi, J.
    Tavecchio, F.
    Tornikoski, M.
    Tzioumis, A. K.
    Urry, C. M.
    Wagner, S.
    Multiwavelength Monitoring of the Enigmatic Narrow-Line Seyfert 1 PMN J0948+0022 in 2009 March-July2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 1, p. 727-737Article in journal (Refereed)
    Abstract [en]

    Following the recent discovery of γ rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to γ rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to γ-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the γ-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.

  • 39. Abdo, A. A.
    et al.
    Ackermann, M.
    Ajello, M.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Blandford, R. D.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Cannon, A.
    Caraveo, P. A.
    Carrigan, S.
    Casandjian, J. M.
    Cavazzuti, E.
    Cecchi, C.
    Celik, Oe.
    Charles, E.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Costamante, L.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    do Couto e Silva, E.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Fegan, S. J.
    Focke, W. B.
    Frailis, M.
    Fukazawa, Y.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Grenier, I. A.
    Grondin, M. -H
    Guiriec, S.
    Hayashida, M.
    Hays, E.
    Hill, A. B.
    Horan, D.
    Hughes, R. E.
    Johannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Knoedlseder, J.
    Kuss, M.
    Lande, J.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Astronomy.
    Latronico, L.
    Lemoine-Goumard, M.
    Garde, Maja Llena
    Stockholm University, Faculty of Science, Department of Physics.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Madejski, G. M.
    Makeev, A.
    Mansutti, O.
    Massaro, E.
    Mazziotta, M. N.
    McConville, W.
    McEnery, J. E.
    Meurer, C.
    Stockholm University, Faculty of Science, Department of Physics.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monte, C.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Panetta, J. H.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Raino, S.
    Rando, R.
    Razzano, M.
    Reimer, A.
    Reimer, O.
    Ritz, S.
    Rodriguez, A. Y.
    Romani, R. W.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F. -W
    Sander, A.
    Scargle, J. D.
    Schalk, T. L.
    Sgro, C.
    Siskind, E. J.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Starck, J. -L
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Takahashi, T.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Thompson, D. J.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    Waite, A. P.
    Wang, P.
    Wehrle, A. E.
    Winer, B. L.
    Wood, K. S.
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics.
    Ylinen, T.
    Ziegler, M.
    FERMI-LARGE AREA TELESCOPE OBSERVATIONS OF THE EXCEPTIONAL GAMMA-RAY OUTBURSTS OF 3C 273 IN 2009 SEPTEMBER2010In: The Astrophysical Journal Letters, ISSN 2041-8205, Vol. 714, no 1, p. L73-L78Article in journal (Refereed)
    Abstract [en]

    We present the light curves and spectral data of two exceptionally luminous gamma-ray outbursts observed by the Large Area Telescope experiment on board the Fermi Gamma-ray Space Telescope from 3C 273 in 2009 September. During these flares, having a duration of a few days, the source reached its highest gamma-ray flux ever measured. This allowed us to study, in some details, their spectral and temporal structures. The rise and the decay are asymmetric on timescales of 6 hr, and the spectral index was significantly harder during the flares than during the preceding 11 months. We also found that short, very intense flares put out the same time-integrated energy as long, less intense flares like that observed in 2009 August.

  • 40. Abdo, A. A.
    et al.
    Ackermann, M.
    Asano, K.
    Atwood, W. B.
    Axelsson, M.
    Stockholm University, Faculty of Science, Department of Astronomy.
    Baldini, L.
    Ballet, J.
    Band, D. L.
    Barbiellini, G.
    Bastieri, D.
    Bechtol, K.
    Bellazzini, R.
    Berenji, B.
    Bhat, P. N.
    Bissaldi, E.
    Bloom, E. D.
    Bonamente, E.
    Borgland, A. W.
    Bouvier, A.
    Bregeon, J.
    Brez, A.
    Briggs, M. S.
    Brigida, M.
    Bruel, P.
    Burnett, T. H.
    Caliandro, G. A.
    Cameron, R. A.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Chaplin, V.
    Chekhtman, A.
    Cheung, C. C.
    Chiang, J.
    Ciprini, S.
    Claus, R.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Connaughton, V.
    Conrad, J.
    Stockholm University, Faculty of Science, Department of Physics.
    Cutini, S.
    Dermer, C. D.
    de Angelis, A.
    de Palma, F.
    Digel, S. W.
    Silva, E. do Couto e.
    Drell, P. S.
    Dubois, R.
    Dumora, D.
    Farnier, C.
    Favuzzi, C.
    Focke, W. B.
    Frailis, M.
    Fukazawa, Y.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Gehrels, N.
    Germani, S.
    Gibby, L.
    Giebels, B.
    Giglietto, N.
    Giordano, F.
    Glanzman, T.
    Godfrey, G.
    Goldstein, A.
    Granot, J.
    Grenier, I. A.
    Grondin, M.-H.
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hughes, R. E.
    Jóhannesson, G.
    Johnson, A. S.
    Johnson, W. N.
    Kamae, T.
    Katagiri, H.
    Kataoka, J.
    Kawai, N.
    Kerr, M.
    Knödlseder, J.
    Kocevski, D.
    Komin, N.
    Kouveliotou, C.
    Kuehn, F.
    Kuss, M.
    Latronico, L.
    Longo, F.
    Loparco, F.
    Lott, B.
    Lovellette, M. N.
    Lubrano, P.
    Makeev, A.
    Mazziotta, M. N.
    McBreen, S.
    McEnery, J. E.
    McGlynn, S.
    Meegan, C.
    Meurer, C.
    Michelson, P. F.
    Mitthumsiri, W.
    Mizuno, T.
    Monte, C.
    Monzani, M. E.
    Moretti, E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nolan, P. L.
    Norris, J. P.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Omodei, N.
    Orlando, E.
    Ormes, J. F.
    Ozaki, M.
    Paciesas, W. S.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Pelassa, V.
    Pepe, M.
    Pesce-Rollins, M.
    Piron, F.
    Porter, T. A.
    Preece, R.
    Rainò, S.
    Rando, R.
    Razzano, M.
    Razzaque, S.
    Reimer, O.
    Reposeur, T.
    Ritz, S.
    Rochester, L. S.
    Rodriguez, A. Y.
    Roth, M.
    Ryde, F.
    Sadrozinski, H. F.-W.
    Sanchez, D.
    Sander, A.
    Saz Parkinson, P. M.
    Scargle, J. D.
    Sgrò, C.
    Siskind, E. J.
    Smith, D. A.
    Smith, P. D.
    Spandre, G.
    Spinelli, P.
    Stamatikos, M.
    Strickman, M. S.
    Suson, D. J.
    Tajima, H.
    Takahashi, H.
    Tanaka, T.
    Thayer, J. B.
    Thayer, J. G.
    Tibaldo, L.
    Torres, D. F.
    Tosti, G.
    Tramacere, A.
    Uchiyama, Y.
    Usher, T. L.
    van der Horst, A. J.
    Vasileiou, V.
    Vilchez, N.
    Vitale, V.
    von Kienlin, A.
    Waite, A. P.
    Wang, P.
    Wilson-Hodge, C.
    Winer, B. L.
    Wood, K. S.
    Ylinen, T.
    Ziegler, M.
    Fermi Observations of High-energy Gamma-ray Emission from GRB 080825C2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 707, no 1, p. 580-592Article in journal (Refereed)
    Abstract [en]

    The Fermi Gamma-ray Space Telescope has opened a new high-energy window in the study of gamma-ray bursts (GRBs). Here we present a thorough analysis of GRB 080825C, which triggered the Fermi Gamma-ray Burst Monitor (GBM), and was the first firm detection of a GRB by the Fermi Large Area Telescope (LAT). We discuss the LAT event selections, background estimation, significance calculations, and localization for Fermi GRBs in general and GRB 080825C in particular. We show the results of temporal and time-resolved spectral analysis of the GBM and LAT data. We also present some theoretical interpretation of GRB 080825C observations as well as some common features observed in other LAT GRBs.

  • 41. Abdo, A. A.
    et al.
    Ajello, M.
    Allafort, A.
    Baldini, L.
    Ballet, J.
    Barbiellini, G.
    Baring, M. G.
    Bastieri, D.
    Belfiore, A.
    Bellazzini, R.
    Bhattacharyya, B.
    Bissaldi, E.
    Bloom, E. D.
    Bonamente, E.
    Bottacini, E.
    Brandt, T. J.
    Bregeon, J.
    Brigida, M.
    Bruel, P.
    Buehler, R.
    Burgay, M.
    Burnett, T. H.
    Busetto, G.
    Buson, S.
    Caliandro, G. A.
    Cameron, R. A.
    Camilo, F.
    Caraveo, P. A.
    Casandjian, J. M.
    Cecchi, C.
    Celik, Oe .
    Charles, E.
    Chaty, S.
    Chaves, R. C. G.
    Chekhtman, A.
    Chen, A. W.
    Chiang, J.
    Chiaro, G.
    Ciprini, S.
    Claus, R.
    Cognard, I.
    Cohen-Tanugi, J.
    Cominsky, L. R.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Royal Swedish Academy of Sciences, Sweden.
    Cutini, S.
    D'Ammando, F.
    De Angelis, A.
    DeCesar, M. E.
    De Luca, A.
    Den Hartog, P. R.
    De Palma, F.
    Dermer, C. D.
    Desvignes, G.
    Digel, S. W.
    Di Venere, L.
    Drell, P. S.
    Drlica-Wagner, A.
    Dubois, R.
    Dumora, D.
    Espinoza, C. M.
    Falletti, L.
    Favuzzi, C.
    Ferrara, E. C.
    Focke, W. B.
    Franckowiak, A.
    Freire, P. C. C.
    Funk, S.
    Fusco, P.
    Gargano, F.
    Gasparrini, D.
    Germani, S.
    Giglietto, N.
    Giommi, P.
    Giordano, F.
    Giroletti, M.
    Glanzman, T.
    Godfrey, G.
    Gotthelf, E. V.
    Grenier, I. A.
    Grondin, M. -H
    Grove, J. E.
    Guillemot, L.
    Guiriec, S.
    Hadasch, D.
    Hanabata, Y.
    Harding, A. K.
    Hayashida, M.
    Hays, E.
    Hessels, J.
    Hewitt, J.
    Hill, A. B.
    Horan, D.
    Hou, X.
    Hughes, R. E.
    Jackson, M. S.
    Janssen, G. H.
    Jogler, T.
    Johannesson, G.
    Johnson, R. P.
    Johnson, A. S.
    Johnson, T. J.
    Johnson, W. N.
    Johnston, S.
    Kamae, T.
    Kataoka, J.
    Keith, M.
    Kerr, M.
    Knoedlseder, J.
    Kramer, M.
    Kuss, M.
    Lande, J.
    Larsson, Stefan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Latronico, L.
    Lemoine-Goumard, M.
    Longo, F.
    Loparco, F.
    Lovellette, M. N.
    Lubrano, P.
    Lyne, A. G.
    Manchester, R. N.
    Marelli, M.
    Massaro, F.
    Mayer, M.
    Mazziotta, M. N.
    McEnery, J. E.
    McLaughlin, M. A.
    Mehault, J.
    Michelson, P. F.
    Mignani, R. P.
    Mitthumsiri, W.
    Mizuno, T.
    Moiseev, A. A.
    Monzani, M. E.
    Morselli, A.
    Moskalenko, I. V.
    Murgia, S.
    Nakamori, T.
    Nemmen, R.
    Nuss, E.
    Ohno, M.
    Ohsugi, T.
    Orienti, M.
    Orlando, E.
    Ormes, J. F.
    Paneque, D.
    Panetta, J. H.
    Parent, D.
    Perkins, J. S.
    Pesce-Rollins, M.
    Pierbattista, M.
    Piron, F.
    Pivato, G.
    Pletsch, H. J.
    Porter, T. A.
    Possenti, A.
    Raino, S.
    Rando, R.
    Ransom, S. M.
    Ray, P. S.
    Razzano, M.
    Rea, N.
    Reimer, A.
    Reimer, O.
    Renault, N.
    Reposeur, T.
    Ritz, S.
    Romani, R. W.
    Roth, M.
    Rousseau, R.
    Roy, J.
    Ruan, J.
    Sartori, A.
    Parkinson, P. M. Saz
    Scargle, J. D.
    Schulz, A.
    Sgro, C.
    Shannon, R.
    Siskind, E. J.
    Smith, D. A.
    Spandre, G.
    Spinelli, P.
    Stappers, B. W.
    Strong, A. W.
    Suson, D. J.
    Takahashi, H.
    Thayer, J. G.
    Thayer, J. B.
    Theureau, G.
    Thompson, D. J.
    Thorsett, S. E.
    Tibaldo, L.
    Tibolla, O.
    Tinivella, M.
    Torres, D. F.
    Tosti, G.
    Troja, E.
    Uchiyama, Y.
    Usher, T. L.
    Vandenbroucke, J.
    Vasileiou, V.
    Venter, C.
    Vianello, G.
    Vitale, V.
    Wang, N.
    Weltevrede, P.
    Winer, B. L.
    Wolff, M. T.
    Wood, D. L.
    Wood, K. S.
    Wood, M.
    Yang, Zhaoyu
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    THE SECOND FERMI LARGE AREA TELESCOPE CATALOG OF GAMMA-RAY PULSARS2013In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 208, no 2Article in journal (Refereed)
    Abstract [en]

    This catalog summarizes 117 high-confidence >= 0.1 GeV gamma-ray pulsar detections using three years of data acquired by the Large Area Telescope (LAT) on the Fermi satellite. Half are neutron stars discovered using LAT data through periodicity searches in gamma-ray and radio data around LAT unassociated source positions. The 117 pulsars are evenly divided into three groups: millisecond pulsars, young radio-loud pulsars, and young radio-quiet pulsars. We characterize the pulse profiles and energy spectra and derive luminosities when distance information exists. Spectral analysis of the off-peak phase intervals indicates probable pulsar wind nebula emission for four pulsars, and off-peak magnetospheric emission for several young and millisecond pulsars. We compare the gamma-ray properties with those in the radio, optical, and X-ray bands. We provide flux limits for pulsars with no observed gamma-ray emission, highlighting a small number of gamma-faint, radio-loud pulsars. The large, varied gamma-ray pulsar sample constrains emission models. Fermi's selection biases complement those of radio surveys, enhancing comparisons with predicted population distributions.

  • 42. Abdo, A. A.
    et al.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Royal Swedish Academy of Sciences, Sweden.
    Meruer, C.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sellerholm, Alexander
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ziegler, M.
    Spectrum of the Isotropic Diffuse Gamma-Ray Emission Derived from First-Year Fermi Large Area Telescope Data2010In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 104, article id 101101Article in journal (Refereed)
    Abstract [en]

    We report on the first Fermi Large Area Telescope (LAT) measurements of the so-called ‘‘extra- galactic’’ diffuse gamma-ray emission (EGB). This component of the diffuse Υ-ray emission is generally considered to have an isotropic or nearly isotropic distribution on the sky with diverse contributions discussed in the literature. The derivation of the EGB is based on detailed modeling of the bright foreground diffuse Galactic gamma-ray emission, the detected LAT sources, and the solar gamma-ray emission. We find the spectrum of the EGB is consistent with a power law with a differential spectral index of 2.41 \pm 0.05 and intensity I(>100 MeV)=(1.03\pm 0.17) e-5 cm**2 s **-1 sr**-1 , where the error is systematics dominated. Our EGB spectrum is featureless, less intense, and softer than that derived from EGRET data.

  • 43. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    Sellerholm, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Bright Active Galactic Nuclei Source List from the First Three Months of the Fermi Large Area Telescope All-Sky Survey2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 700, no 1, p. 597-622Article in journal (Refereed)
    Abstract [en]

    The first three months of sky-survey operation with the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope reveal 132 bright sources at |b|>10° with test statistic greater than 100 (corresponding to about 10σ). Two methods, based on the CGRaBS, CRATES, and BZCat catalogs, indicate high-confidence associations of 106 of these sources with known active galactic nuclei (AGNs). This sample is referred to as the LAT Bright AGN Sample (LBAS). It contains two radio galaxies, namely, Centaurus A and NGC 1275, and 104 blazars consisting of 58 flat spectrum radio quasars (FSRQs), 42 BL Lac objects, and 4 blazars with unknown classification. Four new blazars were discovered on the basis of the LAT detections. Remarkably, the LBAS includes 10 high-energy-peaked BL Lacs (HBLs), sources which were previously difficult to detect in the GeV range. Another 10 lower-confidence associations are found. Only 33 of the sources, plus two at |b| < 10°, were previously detected with Energetic Gamma-Ray Experiment Telescope(EGRET), probably due to variability. The analysis of the γ-ray properties of the LBAS sources reveals that the average GeV spectra of BL Lac objects are significantly harder than the spectra of FSRQs. No significant correlation between radio and peak γ-ray fluxes is observed. Blazar log N-log S distributions and luminosity functions are constructed to investigate the evolution of the different blazar classes, with positive evolution indicated for FSRQs but none for BL Lacs. The contribution of LAT blazars to the total extragalactic γ-ray intensity is estimated.

  • 44. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    Sellerholm, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Fermi/Large Area Telescope Bright Gamma-Ray Source List2009In: Astrophysical Journal Supplement Series, ISSN 0067-0049, E-ISSN 1538-4365, Vol. 183, no 1, p. 46-66Article in journal (Refereed)
    Abstract [en]

    Following its launch in 2008 June, the Fermi Gamma-ray Space Telescope (Fermi) began a sky survey in August. The Large Area Telescope (LAT) on Fermi in three months produced a deeper and better resolved map of the γ-ray sky than any previous space mission. We present here initial results for energies above 100 MeV for the 205 most significant (statistical significance greater than ~10σ) γ-ray sources in these data. These are the best characterized and best localized point-like (i.e., spatially unresolved) γ-ray sources in the early mission data.

  • 45. Abdo, A, et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    Sellerholm, Alexander
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Measurement of the Cosmic Ray e++e- Spectrum from 20GeV to 1TeV with the Fermi Large Area Telescope2009In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 102, no 18Article in journal (Refereed)
    Abstract [en]

    Designed as a high-sensitivity gamma-ray observatory, the Fermi Large Area Telescope is also an electron detector with a large acceptance exceeding 2m2sr at 300 GeV. Building on the gamma-ray analysis, we have developed an efficient electron detection strategy which provides sufficient background rejection for measurement of the steeply falling electron spectrum up to 1 TeV. Our high precision data show that the electron spectrum falls with energy as E-3.0 and does not exhibit prominent spectral features. Interpretations in terms of a conventional diffusive model as well as a potential local extra component are briefly discussed.

  • 46. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi LAT Collboration,
    The Fermi GBM Collaboration,
    Fermi Observations of High-Energy Gamma-Ray Emission from GRB 080916C2009In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 323, no 5922, p. 1688-Article in journal (Refereed)
    Abstract [en]

    Gamma-ray bursts (GRBs) are highly energetic explosions signaling the death of massive stars in distant galaxies. The Gamma-ray Burst Monitor and Large Area Telescope onboard the Fermi Observatory together record GRBs over a broad energy range spanning about 7 decades of gammaray energy. In September 2008, Fermi observed the exceptionally luminous GRB 080916C, with the largest apparent energy release yet measured. The high-energy gamma rays are observed to start later and persist longer than the lower energy photons. A simple spectral form fits the entire GRB spectrum, providing strong constraints on emission models. The known distance of the burst enables placing lower limits on the bulk Lorentz factor of the outflow and on the quantum gravity mass.

  • 47. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Discovery of Pulsations from the Pulsar J0205+6449 in SNR 3C 58 with the Fermi Gamma-Ray Space Telescope2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 699, no 2, p. L102-L107Article in journal (Refereed)
    Abstract [en]

    We report the discovery of γ-ray pulsations (>=0.1 GeV) from the young radio and X-ray pulsar PSR J0205 + 6449 located in the Galactic supernova remnant 3C 58. Data in the γ-ray band were acquired by the Large Area Telescope aboard the Fermi Gamma-ray Space Telescope (formerly GLAST), while the radio rotational ephemeris used to fold γ-rays was obtained using both the Green Bank Telescope and the Lovell telescope at Jodrell Bank. The light curve consists of two peaks separated by 0.49 ± 0.01 ± 0.01 cycles which are aligned with the X-ray peaks. The first γ-ray peak trails the radio pulse by 0.08 ± 0.01 ± 0.01, while its amplitude decreases with increasing energy as for the other γ-ray pulsars. Spectral analysis of the pulsed γ-ray emission suggests a simple power law of index –2.1 ± 0.1 ± 0.2 with an exponential cutoff at 3.0+1.1 –0.7 ± 0.4 GeV. The first uncertainty is statistical and the second is systematic. The integral γ-ray photon flux above 0.1 GeV is (13.7 ± 1.4 ± 3.0) × 10–8 cm–2 s–1, which implies for a distance of 3.2 kpc and assuming a broad fan-like beam a luminosity of 8.3 × 1034 erg s–1 and an efficiency η of 0.3%. Finally, we report a 95% upper limit on the flux of 1.7 × 10–8 cm–2 s–1 for off-pulse emission from the object.

  • 48. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Early Fermi Gamma-ray Space Telescope Observations of the Quasar 3C 454.32009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 699, no 1, p. 817-823Article in journal (Refereed)
    Abstract [en]

    This is the first report of Fermi Gamma-Ray Space Telescope observations of the quasar 3C 454.3, which has been undergoing pronounced long-term outbursts since 2000. The data from the Large Area Telescope, covering 2008 July 7-October 6, indicate strong, highly variable γ-ray emission with an average flux of ~3 × 10–6 photons cm–2 s–1, for energies >100 MeV. The γ-ray flux is variable, with strong, distinct, symmetrically shaped flares for which the flux increases by a factor of several on a timescale of about 3 days. This variability indicates a compact emission region, and the requirement that the source is optically thin to pair production implies relativistic beaming with Doppler factor δ>8, consistent with the values inferred from Very Long Baseline Interferometry observations of superluminal expansion (δ ~ 25). The observed γ-ray spectrum is not consistent with a simple power law, but instead steepens strongly above ~2 GeV, and is well described by a broken power law with photon indices of ~2.3 and ~3.5 below and above the break, respectively. This is the first direct observation of a break in the spectrum of a high-luminosity blazar above 100 MeV, and it is likely direct evidence for an intrinsic break in the energy distribution of the radiating particles. Alternatively, the spectral softening above 2 GeV could be due to γ-ray absorption via photon-photon pair production on the soft X-ray photon field of the host active galactic nucleus, but such an interpretation would require the dissipation region to be located very close (lsim100 gravitational radii) to the black hole, which would be inconsistent with the X-ray spectrum of the source.

  • 49. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Fermi/Large Area Telescope Discovery of Gamma-Ray Emission from a Relativistic Jet in the Narrow-Line Quasar PMN J0948+00222009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 699, no 2, p. 976-984Article in journal (Refereed)
    Abstract [en]

    We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope of high-energy γ-ray emission from the peculiar quasar PMN J0948+0022 (z = 0.5846). The optical spectrum of this object exhibits rather narrow Hβ (FWHM(Hβ) ~1500 km s–1), weak forbidden lines, and is therefore classified as a narrow-line type I quasar. This class of objects is thought to have relatively small black hole mass and to accrete at a high Eddington ratio. The radio loudness and variability of the compact radio core indicate the presence of a relativistic jet. Quasi-simultaneous radio/optical/X-ray and γ-ray observations are presented. Both radio and γ-ray emissions (observed over five months) are strongly variable. The simultaneous optical and X-ray data from Swift show a blue continuum attributed to the accretion disk and a hard X-ray spectrum attributed to the jet. The resulting broadband spectral energy distribution (SED) and, in particular, the γ-ray spectrum measured by Fermi are similar to those of more powerful Flat-Spectrum Radio Quasars (FSRQs). A comparison of the radio and γ-ray characteristics of PMN J0948+0022 with the other blazars detected by LAT shows that this source has a relatively low radio and γ-ray power with respect to other FSRQs. The physical parameters obtained from modeling the SED also fall at the low power end of the FSRQ parameter region discussed in Celotti & Ghisellini. We suggest that the similarity of the SED of PMN J0948+0022 to that of more massive and more powerful quasars can be understood in a scenario in which the SED properties depend on the Eddington ratio rather than on the absolute power.

  • 50. Abdo, A., et al
    et al.
    Axelsson, Magnus
    Stockholm University, Faculty of Science, Department of Astronomy.
    Conrad, Jan
    Stockholm University, Faculty of Science, Department of Physics.
    Meurer, Christine
    Stockholm University, Faculty of Science, Department of Physics.
    The Fermi/LAT Collaboration,
    Fermi/Large Area Telescope Discovery of Gamma-Ray Emission from the Flat-Spectrum Radio Quasar PKS 1454–3542009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 697, no 1, p. 934-941Article in journal (Refereed)
    Abstract [en]

    We report the discovery by the Large Area Telescope (LAT) onboard the Fermi Gamma-Ray Space Telescope of high-energy γ-ray (GeV) emission from the flat-spectrum radio quasar PKS 1454–354 (z = 1.424). On 2008 September 4, the source rose to a peak flux of (3.5 ± 0.7) × 10–6 ph cm–2 s–1 (E > 100 MeV) on a timescale of hours and then slowly dropped over the following 2 days. No significant spectral changes occurred during the flare. Fermi/LAT observations also showed that PKS 1454–354 is the most probable counterpart of the unidentified EGRET source 3EG J1500–3509. Multiwavelength measurements performed during the following days (7 September with Swift; 6-7 September with the ground-based optical telescope Automated Telescope for Optical Monitoring; 13 September with the Australia Telescope Compact Array) resulted in radio, optical, UV, and X-ray fluxes greater than archival data, confirming the activity of PKS 1454–354.

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