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  • 1. Adams, S. M.
    et al.
    Blagorodnova, N.
    Kasliwal, M. M.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Barlow, T.
    Bue, B.
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cao, Y.
    Cenko, S. B.
    Cook, D. O.
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fox, O. D.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gezari, S.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ho, A. Y. Q.
    Hung, Tiara
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Karamehmetoglu, Emir
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kulkarni, S. R.
    Kupfer, T.
    Laher, R. R.
    Masci, F. J.
    Miller, A. A.
    Neill, J. D.
    Nugent, P. E.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walters, R.
    iPTF Survey for Cool Transients2018In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 130, no 985, article id 034202Article in journal (Refereed)
    Abstract [en]

    We performed a wide-area (2000 deg2) g and I band experiment as part of a two month extension to the Intermediate Palomar Transient Factory. We discovered 36 extragalactic transients including iPTF17lf, a highly reddened local SN Ia, iPTF17bkj, a new member of the rare class of transitional Ibn/IIn supernovae, and iPTF17be, a candidate luminous blue variable outburst. We do not detect any luminous red novae and place an upper limit on their rate. We show that adding a slow-cadence I band component to upcoming surveys such as the Zwicky Transient Facility will improve the photometric selection of cool and dusty transients.

  • 2.
    Ahrens, Maryon
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bohm, Christian
    Stockholm University, Faculty of Science, Department of Physics.
    Conrad, Jan M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dumm, Jonathan P.
    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).
    Flis, Samuel
    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).
    Walck, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Zoll, Marcel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Meyer, Manuel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stanford University, USA.
    Rosswog, Stephan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Feindt, Ulrich
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Roy, Rupak
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Farnier, Christian
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Linnaeus University, Sweden.
    Morå, Knut
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wagner, Robert M.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Multi-messenger Observations of a Binary Neutron Star Merger2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 848, no 2, article id L12Article in journal (Refereed)
    Abstract [en]

    On 2017 August 17 a binary neutron star coalescence candidate (later designated GW170817) with merger time 12:41:04 UTC was observed through gravitational waves by the Advanced LIGO and Advanced Virgo detectors. The Fermi Gamma-ray Burst Monitor independently detected a gamma-ray burst (GRB 170817A) with a time delay of similar to 1.7 s with respect to the merger time. From the gravitational-wave signal, the source was initially localized to a sky region of 31 deg(2) at a luminosity distance of 40(-8)(+8) Mpc and with component masses consistent with neutron stars. The component masses were later measured to be in the range 0.86 to 2.26 M-circle dot. An extensive observing campaign was launched across the electromagnetic spectrum leading to the discovery of a bright optical transient (SSS17a, now with the IAU identification of AT 2017gfo) in NGC 4993 (at similar to 40 Mpc) less than 11 hours after the merger by the One-Meter, Two Hemisphere (1M2H) team using the 1 m Swope Telescope. The optical transient was independently detected by multiple teams within an hour. Subsequent observations targeted the object and its environment. Early ultraviolet observations revealed a blue transient that faded within 48 hours. Optical and infrared observations showed a redward evolution over similar to 10 days. Following early non-detections, X-ray and radio emission were discovered at the transient's position similar to 9 and similar to 16 days, respectively, after the merger. Both the X-ray and radio emission likely arise from a physical process that is distinct from the one that generates the UV/optical/near-infrared emission. No ultra-high-energy gamma-rays and no neutrino candidates consistent with the source were found in follow-up searches. These observations support the hypothesis that GW170817 was produced by the merger of two neutron stars in NGC4993 followed by a short gamma-ray burst (GRB 170817A) and a kilonova/macronova powered by the radioactive decay of r-process nuclei synthesized in the ejecta.

  • 3. Altavilla, G.
    et al.
    Ruiz-Lapuente, P.
    Balastegui, A.
    Méndez, J.
    Irwin, M.
    España-Bonet, C.
    Ellis, R. S.
    Folatelli, G.
    Stockholm University, Faculty of Science, Department of Physics.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Hillebrandt, W.
    McMahon, R. M.
    Nobili, Serena
    Stockholm University, Faculty of Science, Department of Physics.
    Stanishev, Vallery
    Stockholm University, Faculty of Science, Department of Physics.
    Walton, N. A.
    Type Ia SNe Along Redshift: The \mathcal {R}(Si II) Ratio and the Expansion Velocities in Intermediate-z Supernovae2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 695, p. 135-148Article in journal (Refereed)
    Abstract [en]

    We present a study of intermediate-z Type Ia supernovae (SNe Ia) using empirical physical diagrams which permit the investigation of those SNe explosions. This information can be very useful to reduce systematic uncertainties of the Hubble diagram of SNe Ia up to high z. The study of the expansion velocities and the measurement of the ratio \mathcal {R}(Si II) allow subtyping of SNe Ia as done in nearby samples. The evolution of this ratio as seen in the diagram \mathcal {R}(Si II)-(t) together with \mathcal {R}(Si II)max versus (B - V)0 indicates consistency of the properties at intermediate-z compared with the nearby SNe Ia. At intermediate-z, expansion velocities of Ca II and Si II are found similar to those of the nearby sample. This is found in a sample of six SNe Ia in the range 0.033 <=z<= 0.329 discovered within the International Time Programme of SNe Ia for Cosmology and Physics in the spring run of 2002.7The program run under Omega and Lambda from Supernovae and the Physics of Supernova Explosions within the International Time Programme at the telescopes of the European Northern Observatory (ENO) at La Palma (Canary Islands, Spain). Two SNe Ia at intermediate-z were of the cool FAINT type, one being an SN1986G-like object highly reddened. The \mathcal {R}(Si II) ratio as well as subclassification of the SNe Ia beyond templates help to place SNe Ia in their sequence of brightness and to distinguish between reddened and intrinsically red supernovae. This test can be done with very high z SNe Ia and it will help to reduce systematic uncertainties due to extinction by dust. It should allow to map the high-z sample into the nearby one.

  • 4. Altavilla, G.
    et al.
    Stehle, M.
    Ruiz-Lapuente, P.
    Mazzali, P.
    Pignata, G.
    Balastegui, A.
    Benetti, S.
    Blanc, G.
    Canal, R.
    Elias-Rosa, N.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Harutyunyan, A.
    Pastorello, A.
    Patat, F.
    Rich, J.
    Salvo, M.
    Schmidt, B. P.
    Stanishev, V.
    Taubenberger, S.
    Hillebrandt, W.
    The early spectral evolution of SN2004dt2007In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 475, no 2, p. 585-595Article in journal (Refereed)
    Abstract [en]

    Aims. We study the optical spectroscopic properties of Type Ia Supernova (SNIa) 2004dt, focusing our attention on the early epochs. Methods. Observation triggered soon after the SN 2004dt discovery allowed us to obtain a spectrophotometric coverage from day -10 to almost one year (similar to 353 days) after the B band maximum. Observations carried out on an almost daily basis allowed us a good sampling of the fast spectroscopic evolution of SN 2004dt in the early stages. To obtain this result, low-resolution, long-slit spectroscopy was obtained using a number of facilities. Results. This supernova, which in some absorption lines of its early spectra showed the highest degree of polarization ever measured in any SN Ia, has a complex velocity structure in the outer layers of its ejecta. Unburnt oxygen is present, moving at velocities as high as similar to 16 700 km s(-1), with some intermediate-mass elements (Mg, Si, Ca) moving equally fast. Modeling of the spectra based on standard density profiles of the ejecta fails to reproduce the observed features, whereas enhancing the density of outer layers significantly improves the fit. Our analysis indicates the presence of clumps of high-velocity, intermediate-mass elements in the outermost layers, which is also suggested by the spectropolarimetric data.

  • 5.
    Amanullah, R.
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Clement, B.
    Cuby, J. -G
    Dahle, H.
    Dahlen, T.
    Hjorth, J.
    Fabbro, S.
    Jönsson, Jakob
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kneib, J. -P
    Lidman, C.
    Limousin, M.
    Milvang-Jensen, B.
    Mortsell, E.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Paech, K.
    Richard, J.
    Riehm, Teresa
    Stockholm University, Faculty of Science, Department of Astronomy.
    Stanishev, V.
    Watson, D.
    A HIGHLY MAGNIFIED SUPERNOVA AT z=1.703 BEHIND THE MASSIVE GALAXY CLUSTER A16892011In: ASTROPHYS J LETT, ISSN 2041-8205, Vol. 742, no 1, p. L7-Article in journal (Refereed)
    Abstract [en]

    Our ability to study the most remote supernova explosions, crucial for the understanding of the evolution of the high-redshift universe and its expansion rate, is limited by the light collection capabilities of telescopes. However, nature offers unique opportunities to look beyond the range within reach of our unaided instruments thanks to the light-focusing power of massive galaxy clusters. Here we report on the discovery of one of the most distant supernovae ever found, at redshift z = 1.703. Due to a lensing magnification factor of 4.3 +/- 0.3, we are able to measure a light curve of the supernova, as well as spectroscopic features of the host galaxy with a precision comparable to what would otherwise only be possible with future generation telescopes.

  • 6.
    Amanullah, Rahman
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    PERTURBATIONS OF SNe Ia LIGHT CURVES, COLORS, AND SPECTRAL FEATURES BY CIRCUMSTELLAR DUST2011In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 735, no 1, p. 20-Article in journal (Refereed)
    Abstract [en]

    It has been suggested that multiple scattering on circumstellar dust could explain the non-standard reddening observed in the line of sight to Type Ia supernovae. In this work, we use Monte Carlo simulations to examine how the scattered light would affect the shape of optical light curves and spectral features. We find that the effects on the light curve widths, apparent time evolution of color excess, and blending of spectral features originating at different photospheric velocities should allow for tests of the circumstellar dust hypothesis on a case by case basis. Our simulations also show that for circumstellar shells with radii r = 10(16)-10(19) cm, the light curve modifications are well described by the empirical Delta m(15) parameter and intrinsic color variations of order sigma(BV) = 0.05-0.1 arise naturally. For large shell radii an excess light curve tail is expected in B-band, as observed in, e.g., SN2006X.

  • 7.
    Amanullah, Rahman
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Banerjee, D. P. K.
    Venkataraman, V.
    Joshi, V.
    Ashok, N. M.
    Cao, Y.
    Kasliwal, M. M.
    Kulkarni, S. R.
    Nugent, P. E.
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stanishev, V.
    THE PECULIAR EXTINCTION LAW OF SN 2014J MEASURED WITH THE HUBBLE SPACE TELESCOPE2014In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 788, no 2, p. L21-Article in journal (Refereed)
    Abstract [en]

    The wavelength dependence of the extinction of Type Ia SN 2014J in the nearby galaxy M82 has been measured using UV to near-IR photometry obtained with the Hubble Space Telescope, the Nordic Optical Telescope, and the Mount Abu Infrared Telescope. This is the first time that the reddening of an SN Ia is characterized over the full wavelength range of 0.2-2 mu m. A total-to-selective extinction, R-V >= 3.1, is ruled out with high significance. The best fit at maximum using a Galactic type extinction law yields R-V = 1.4 +/- 0.1. The observed reddening of SN 2014J is also compatible with a power-law extinction, A(lambda)/A(V) = (lambda/lambda(V))(p) as expected from multiple scattering of light, with p = -2.1 +/- 0.1. After correcting for differences in reddening, SN 2014J appears to be very similar to SN 2011 fe over the 14 broadband filter light curves used in our study.

  • 8.
    Amanullah, Rahman
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Papadogiannakis, Seméli
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Brown, P. J.
    Cao, Y.
    Contreras, C.
    Dahle, H.
    Elias-Rosa, N.
    Fynbo, J. P. U.
    Gorosabel, J.
    Guaita, L.
    Hangard, Laura
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Howell, D. A.
    Hsiao, E. Y.
    Kankare, E.
    Kasliwal, M.
    Leloudas, G.
    Lundqvist, Peter
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mattila, S.
    Nugent, P.
    Phillips, M. M.
    Sandberg, Andreas
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stanishev, V.
    Sullivan, M.
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Östlin, Göran
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Asadi, Saghar
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Herrero-Illana, R.
    Jensen, J. J.
    Karhunen, K.
    Lazarevic, S.
    Varenius, E.
    Santos, P.
    Sridhar, S. Seethapuram
    Wallström, S. H. J.
    Wiegert, J.
    Diversity in extinction laws of Type Ia supernovae measured between 0.2 and 2 mu m2015In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 453, no 3, p. 3300-3328Article in journal (Refereed)
    Abstract [en]

    We present ultraviolet (UV) observations of six nearby Type Ia supernovae (SNe Ia) obtained with the Hubble Space Telescope, three of which were also observed in the near-IR (NIR) with Wide-Field Camera 3. UV observations with the Swift satellite, as well as ground-based optical and NIR data provide complementary information. The combined data set covers the wavelength range 0.2-2 mu m. By also including archival data of SN 2014J, we analyse a sample spanning observed colour excesses up to E(B - V) = 1.4 mag. We study the wavelength-dependent extinction of each individual SN and find a diversity of reddening laws when characterized by the total-to-selective extinction R-V. In particular, we note that for the two SNe with E(B - V) greater than or similar to 1 mag, for which the colour excess is dominated by dust extinction, we find R-V = 1.4 +/- 0.1 and R-V = 2.8 +/- 0.1. Adding UV photometry reduces the uncertainty of fitted R-V by similar to 50 per cent allowing us to also measure R-V of individual low-extinction objects which point to a similar diversity, currently not accounted for in the analyses when SNe Ia are used for studying the expansion history of the Universe.

  • 9.
    Amanullah, Rahman
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Lidman, Chris
    Stockholm University, Faculty of Science, Department of Physics.
    Rubin, D.
    Aldering, G.
    Astier, P.
    Barbary, K.
    Burns, M. S.
    Conley, A.
    Dawson, K. S.
    Deustua, S. E.
    Doi, M.
    Fabbro, S.
    Faccioli, L.
    Fakhouri, H. K.
    Folatelli, G.
    Fruchter, A. S.
    Furusawa, H.
    Garavini, G.
    Goldhaber, G.
    Goobar, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Groom, D. E.
    Hook, I.
    Howell, D. A.
    Kashikawa, N.
    Kim, A. G.
    Knop, R. A.
    Kowalski, M.
    Linder, E.
    Meyers, J.
    Morokuma, T.
    Nobili, Serena
    Stockholm University, Faculty of Science, Department of Physics.
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Nugent, P. E.
    Östman, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    Pain, R.
    Panagia, N.
    Perlmutter, S.
    Raux, J.
    Ruiz-Lapuente, P.
    Spadafora, A. L.
    Strovink, M.
    Suzuki, N.
    Wang, L.
    Wood-Vasey, W. M.
    Yasuda, N.
    Supernova Cosmology Project, The
    Spectra and Hubble Space Telescope Light Curves of Six Type Ia Supernovae at 0.511 < z < 1.12 and the Union2 Compilation2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 716, p. 712-738Article in journal (Refereed)
    Abstract [en]

    We report on work to increase the number of well-measured Type Ia supernovae (SNe Ia) at high redshifts. Light curves, including high signal-to-noise Hubble Space Telescope data, and spectra of six SNe Ia that were discovered during 2001, are presented. Additionally, for the two SNe with z > 1, we present ground-based J-band photometry from Gemini and the Very Large Telescope. These are among the most distant SNe Ia for which ground-based near-IR observations have been obtained. We add these six SNe Ia together with other data sets that have recently become available in the literature to the Union compilation. We have made a number of refinements to the Union analysis chain, the most important ones being the refitting of all light curves with the SALT2 fitter and an improved handling of systematic errors. We call this new compilation, consisting of 557 SNe, the Union2 compilation. The flat concordance ΛCDM model remains an excellent fit to the Union2 data with the best-fit constant equation-of-state parameter w = -0.997+0.050 -0.054(stat)+0.077 -0.082(stat + sys together) for a flat universe, or w = -1.038+0.056 -0.059(stat)+0.093 -0.097(stat + sys together) with curvature. We also present improved constraints on w(z). While no significant change in w with redshift is detected, there is still considerable room for evolution in w. The strength of the constraints depends strongly on redshift. In particular, at z >~ 1, the existence and nature of dark energy are only weakly constrained by the data. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under the NASA contract NAS 5-26555. The observations are associated with programs HST-GO-08585 and HST-GO-09075. Based, in part, on observations obtained at the ESO La Silla Paranal Observatory (ESO programs 67.A-0361 and 169.A-0382). Based, in part, on observations obtained at the Cerro-Tololo Inter-American Observatory (CTIO), National Optical Astronomy Observatory (NOAO). Based on observations obtained at the Canada-France-Hawaii Telescope (CFHT). Based, in part, on observations obtained at the Gemini Observatory (Gemini programs GN-2001A-SV-19 and GN-2002A-Q-31). Based, in part on observations obtained at the Subaru Telescope. Based, in part, on data that were obtained at the W. M. Keck Observatory.

  • 10.
    Andersson, Karl
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Peterson, J. R.
    Madejski, G.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Characterizing the Properties of Clusters of Galaxies as a Function of Luminosity and Redshift2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 696, p. 1029-1050Article in journal (Refereed)
    Abstract [en]

    We report the application of the new Monte Carlo method, smoothed particle inference (SPI, described in a pair of companion papers), toward analysis and interpretation of X-ray observations of clusters of galaxies with the XMM-Newton satellite. Our sample consists of publicly available well exposed observations of clusters at redshifts z > 0.069, totaling 101 objects. We determine the luminosity and temperature structure of the X-ray emitting gas, with the goal to quantify the scatter and the evolution of the LX -T relation, as well as to investigate the dependence on cluster substructure with redshift. This work is important for the establishment of the potential robustness of mass estimates from X-ray data which in turn is essential toward the use of clusters for measurements of cosmological parameters. We use the luminosity and temperature maps derived via the SPI technique to determine the presence of cooling cores, via measurements of luminosity and temperature contrast. The LX -T relation is investigated, and we confirm that LX vprop T 3. We find a weak redshift dependence (\propto (1+z)^{\beta _{LT}}, \beta _{LT}=0.50 \pm 0.34), in contrast to some Chandra results. The level of dynamical activity is established using the "power ratio" method, and we compare our results to previous application of this method to Chandra data for clusters. We find signs of evolution in the P 3/P 0 power ratio. A new method, the "temperature two-point correlation function," is proposed. This method is used to determine the "power spectrum" of temperature fluctuations in the X-ray emitting gas as a function of spatial scale. We show how this method can be fruitfully used to identify cooling core clusters as well as those with disturbed structures, presumably due to ongoing or recent merger activity.

  • 11. Andreoni, I.
    et al.
    Ackley, K.
    Cooke, J.
    Acharyya, A.
    Allison, J. R.
    Anderson, G. E.
    Ashley, M. C. B.
    Baade, D.
    Bailes, M.
    Bannister, K.
    Beardsley, A.
    Bessell, M. S.
    Bian, F.
    Bland, P. A.
    Boer, M.
    Booler, T.
    Brandeker, Alexis
    Stockholm University, Faculty of Science, Department of Astronomy.
    Brown, I. S.
    Buckley, D. A. H.
    Chang, S. -W.
    Coward, D. M.
    Crawford, S.
    Crisp, H.
    Crosse, B.
    Cucchiara, A.
    Cupak, M.
    de Gois, J. S.
    Deller, A.
    Devillepoix, H. A. R.
    Dobie, D.
    Elmer, E.
    Emrich, D.
    Farah, W.
    Farrell, T. J.
    Franzen, T.
    Gaensler, B. M.
    Galloway, D. K.
    Gendre, B.
    Giblin, T.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Green, J.
    Hancock, P. J.
    Hartig, B. A. D.
    Howell, E. J.
    Horsley, L.
    Hotan, A.
    Howie, R. M.
    Hu, L.
    Hu, Y.
    James, C. W.
    Johnston, S.
    Johnston-Hollitt, M.
    Kaplan, D. L.
    Kasliwal, M.
    Keane, E. F.
    Kenney, D.
    Klotz, A.
    Lau, R.
    Laugier, R.
    Lenc, E.
    Li, X.
    Liang, E.
    Lidman, C.
    Luvaul, L. C.
    Lynch, C.
    Ma, B.
    Macpherson, D.
    Mao, J.
    McClelland, D. E.
    McCully, C.
    Moller, A.
    Morales, M. F.
    Morris, D.
    Murphy, T.
    Noysena, K.
    Onken, C. A.
    Orange, N. B.
    Oslowski, S.
    Pallot, D.
    Paxman, J.
    Potter, S. B.
    Pritchard, T.
    Raja, W.
    Ridden-Harper, R.
    Romero-Colmenero, E.
    Sadler, E. M.
    Sansom, E. K.
    Scalzo, R. A.
    Schmidt, B. P.
    Scott, S. M.
    Seghouani, N.
    Shang, Z.
    Shannon, R. M.
    Shao, L.
    Shara, M. M.
    Sharp, R.
    Sokolowski, M.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy.
    Staff, J.
    Steele, K.
    Sun, T.
    Suntzeff, N. B.
    Tao, C.
    Tingay, S.
    Towner, M. C.
    Thierry, P.
    Trott, C.
    Tucker, B. E.
    Vaisanen, P.
    Krishnan, V. Venkatraman
    Walker, M.
    Wang, L.
    Wang, X.
    Wayth, R.
    Whiting, M.
    Williams, A.
    Williams, T.
    Wolf, C.
    Wu, C.
    Wu, X.
    Yang, J.
    Yuan, X.
    Zhang, H.
    Zhou, J.
    Zovaro, H.
    Follow Up of GW170817 and Its Electromagnetic Counterpart by Australian-Led Observing Programmes2017In: Publications Astronomical Society of Australia, ISSN 1323-3580, E-ISSN 1448-6083, Vol. 34, article id e069Article, review/survey (Refereed)
    Abstract [en]

    The discovery of the first electromagnetic counterpart to a gravitational wave signal has generated follow-up observations by over 50 facilities world-wide, ushering in the new era of multi-messenger astronomy. In this paper, we present follow-up observations of the gravitational wave event GW170817 and its electromagnetic counterpart SSS17a/DLT17ck (IAU label AT2017gfo) by 14 Australian telescopes and partner observatories as part of Australian-based and Australian-led research programs. We report early- to late-time multi-wavelength observations, including optical imaging and spectroscopy, mid-infrared imaging, radio imaging, and searches for fast radio bursts. Our optical spectra reveal that the transient source emission cooled from approximately 6 400 K to 2 100 K over a 7-d period and produced no significant optical emission lines. The spectral profiles, cooling rate, and photometric light curves are consistent with the expected outburst and subsequent processes of a binary neutron star merger. Star formation in the host galaxy probably ceased at least a Gyr ago, although there is evidence for a galaxy merger. Binary pulsars with short (100 Myr) decay times are therefore unlikely progenitors, but pulsars like PSR B1534+12 with its 2.7 Gyr coalescence time could produce such a merger. The displacement (similar to 2.2 kpc) of the binary star system from the centre of the main galaxy is not unusual for stars in the host galaxy or stars originating in the merging galaxy, and therefore any constraints on the kick velocity imparted to the progenitor are poor.

  • 12. Astier, P.
    et al.
    Balland, C.
    Brescia, M.
    Cappellaro, E.
    Carlberg, R. G.
    Cavuoti, S.
    Della Valle, M.
    Gangler, E.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Guy, J.
    Hardin, D.
    Hook, I. M.
    Kessler, R.
    Kim, A.
    Linder, E.
    Longo, G.
    Maguire, K.
    Mannucci, F.
    Mattila, S.
    Nichol, R.
    Pain, R.
    Regnault, N.
    Spiro, S.
    Sullivan, M.
    Tao, C.
    Turatto, M.
    Wang, X. F.
    Wood-Vasey, W. M.
    Extending the supernova Hubble diagram to z similar to 1.5 with the Euclid space mission2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 572, p. A80-Article in journal (Refereed)
    Abstract [en]

    We forecast dark energy constraints that could be obtained from a new large sample of Type Ia supernovae where those at high redshift are acquired with the Euclid space mission. We simulate a three-prong SN survey: a z < 0.35 nearby sample (8000 SNe), a 0.2 < z < 0.95 intermediate sample (8800 SNe), and a 0.75 < z < 1.55 high-z sample (1700 SNe). The nearby and intermediate surveys are assumed to be conducted from the ground, while the high-z is a joint ground-and space-based survey. This latter survey, the Dark Energy Supernova Infra-Red Experiment (DESIRE), is designed to fit within 6 months of Euclid observing time, with a dedicated observing programme. We simulate the SN events as they would be observed in rolling-search mode by the various instruments, and derive the quality of expected cosmological constraints. We account for known systematic uncertainties, in particular calibration uncertainties including their contribution through the training of the supernova model used to fit the supernovae light curves. Using conservative assumptions and a 1D geometric Planck prior, we find that the ensemble of surveys would yield competitive constraints: a constant equation of state parameter can be constrained to sigma(omega) = 0.022, and a Dark Energy Task Force figure of merit of 203 is found for a two-parameter equation of state. Our simulations thus indicate that Euclid can bring a significant contribution to a purely geometrical cosmology constraint by extending a high-quality SN Ia Hubble diagram to z similar to 1.5. We also present other science topics enabled by the DESIRE Euclid observations.

  • 13. Barbary, K.
    et al.
    Aldering, G.
    Amanullah, R.
    Brodwin, M.
    Connolly, N.
    Dawson, K. S.
    Doi, M.
    Eisenhardt, P.
    Faccioli, L.
    Fadeyev, V.
    Fakhouri, H. K.
    Fruchter, A. S.
    Gilbank, D. G.
    Gladders, M. D.
    Goldhaber, G.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Hattori, T.
    Hsiao, E.
    Huang, X.
    Ihara, Y.
    Kashikawa, N.
    Koester, B.
    Konishi, K.
    Kowalski, M.
    Lidman, C.
    Lubin, L.
    Meyers, J.
    Morokuma, T.
    Oda, T.
    Panagia, N.
    Perlmutter, S.
    Postman, M.
    Ripoche, P.
    Rosati, P.
    Rubin, D.
    Schlegel, D. J.
    Spadafora, A. L.
    Stanford, S. A.
    Strovink, M.
    Suzuki, N.
    Takanashi, N.
    Tokita, K.
    Yasuda, N.
    THE HUBBLE SPACE TELESCOPE CLUSTER SUPERNOVA SURVEY. II. THE TYPE Ia SUPERNOVA RATE IN HIGH-REDSHIFT GALAXY CLUSTERS2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 745, no 1, p. 32-Article in journal (Refereed)
    Abstract [en]

    We report a measurement of the Type Ia supernova (SN Ia) rate in galaxy clusters at 0.9 < z < 1.46 from the Hubble Space Telescope Cluster Supernova Survey. This is the first cluster SN Ia rate measurement with detected z > 0.9 SNe. Finding 8 +/- 1 cluster SNe Ia, we determine an SN Ia rate of 0.50(-0.19)(+0.23) (stat) (+0.10)(-0.09) (sys) h(70)(2) SNuB (SNuB equivalent to 10(-12) SNe (L-1)circle dot(,B) yr(-1)). In units of stellar mass, this translates to 0.36(-0.13)(+0.16) (stat) (+0.07)(-0.06) (sys) h(70)(2) SNuM (SNuM = 10(-12) SNe M-1 circle dot yr(-1)). This represents a factor of approximate to 5 +/- 2 increase over measurements of the cluster rate at z < 0.2. We parameterize the late-time SN Ia delay time distribution (DTD) with a power law: Psi(t) t(s). Under the approximation of a single-burst cluster formation redshift of z(f) = 3, our rate measurement in combination with lower-redshift cluster SN Ia rates constrains s = -1.41(-0.40)(+0.47), consistent with measurements of the DTD in the field. This measurement is generally consistent with expectations for the double degenerate scenario and inconsistent with some models for the single degenerate scenario predicting a steeper DTD at large delay times. We check for environmental dependence and the influence of younger stellar populations by calculating the rate specifically in cluster red-sequence galaxies and in morphologically early-type galaxies, finding results similar to the full cluster rate. Finally, the upper limit of one hostless cluster SN Ia detected in the survey implies that the fraction of stars in the intra-cluster medium is less than 0.47 (95% confidence), consistent with measurements at lower redshifts.

  • 14. Barbary, K.
    et al.
    Aldering, G.
    Amanullah, R.
    Brodwin, M.
    Connolly, N.
    Dawson, K. S.
    Doi, M.
    Eisenhardt, P.
    Faccioli, L.
    Fadeyev, V.
    Fakhouri, H. K.
    Fruchter, A. S.
    Gilbank, D. G.
    Gladders, M. D.
    Goldhaber, G.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hattori, T.
    Hsiao, E.
    Huang, X.
    Ihara, Y.
    Kashikawa, N.
    Koester, B.
    Konishi, K.
    Kowalski, M.
    Lidman, C.
    Lubin, L.
    Meyers, J.
    Morokuma, T.
    Oda, T.
    Panagia, N.
    Perlmutter, S.
    Postman, M.
    Ripoche, P.
    Rosati, P.
    Rubin, D.
    Schlegel, D. J.
    Spadafora, A. L.
    Stanford, S. A.
    Strovink, M.
    Suzuki, N.
    Takanashi, N.
    Tokita, K.
    Yasuda, N.
    THE HUBBLE SPACE TELESCOPE CLUSTER SUPERNOVA SURVEY. VI. THE VOLUMETRIC TYPE Ia SUPERNOVA RATE2012In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 745, no 1, article id 31Article in journal (Refereed)
    Abstract [en]

    We present a measurement of the volumetric Type Ia supernova (SN Ia) rate out to z similar or equal to 1.6 from the Hubble Space Telescope Cluster Supernova Survey. In observations spanning 189 orbits with the Advanced Camera for Surveys we discovered 29 SNe, of which approximately 20 are SNe Ia. Twelve of these SNe Ia are located in the foregrounds and backgrounds of the clusters targeted in the survey. Using these new data, we derive the volumetric SN Ia rate in four broad redshift bins, finding results consistent with previous measurements at z greater than or similar to 1 and strengthening the case for an SN Ia rate that is greater than or similar to 0.6 x 10(-4) h(70)(3) yr(-1) Mpc(-3) at z similar to 1 and flattening out at higher redshift. We provide SN candidates and efficiency calculations in a form that makes it easy to rebin and combine these results with other measurements for increased statistics. Finally, we compare the assumptions about host-galaxy dust extinction used in different high-redshift rate measurements, finding that different assumptions may induce significant systematic differences between measurements.

  • 15. Barbary, K.
    et al.
    Dawson, K. S.
    Tokita, K.
    Aldering, G.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics.
    Connolly, N. V.
    Doi, M.
    Faccioli, L.
    Fadeyev, V.
    Fruchter, A. S.
    Goldhaber, G.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Gude, A.
    Huang, X.
    Ihara, Y.
    Konishi, K.
    Kowalski, M.
    Lidman, C.
    Meyers, J.
    Morokuma, T.
    Nugent, P.
    Perlmutter, S.
    Rubin, D.
    Schlegel, D.
    Spadafora, A. L.
    Suzuki, N.
    Swift, H. K.
    Takanashi, N.
    Thomas, R. C.
    Yasuda, N.
    Discovery of an Unusual Optical Transient with the Hubble Space Telescope2009In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 690, p. 1358-1362Article in journal (Refereed)
    Abstract [en]

    We present observations of SCP 06F6, an unusual optical transient discovered during the Hubble Space Telescope Cluster Supernova Survey. The transient brightened over a period of ~100 days, reached a peak magnitude of ~ 21.0 in both i 775 and z 850, and then declined over a similar timescale. There is no host galaxy or progenitor star detected at the location of the transient to a 3σ upper limit of i 775 >= 26.4 and z 850 >= 26.1, giving a corresponding lower limit on the flux increase of a factor of ~ 120. Multiple spectra show five broad absorption bands between 4100 Å and 6500 Å, and a mostly featureless continuum longward of 6500 Å. The shape of the light curve is inconsistent with microlensing. The transient's spectrum, in addition to being inconsistent with all known supernova types, does not match any spectrum in the Sloan Digital Sky Survey database. We suggest that the transient may be one of a new class. Based in part on observations made with the NASA/ESA Hubble Space Telescope, obtained from the data archive at the Space Telescope Science Institute (STScI). STScI is operated by the Association of Universities for Research in Astronomy (AURA), Inc. under the NASA contract NAS 5-26555. The observations are associated with program GO-10496. Based in part on observations obtained at the European Southern Observatory under ESO program 077.A-0110. Based in part on observations collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan. Some of the data presented herein were obtained at the W.M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and NASA.

  • 16. Betoule, M.
    et al.
    Kessler, R.
    Guy, J.
    Mosher, J.
    Hardin, D.
    Biswas, R.
    Astier, P.
    El-Hage, P.
    Konig, M.
    Kuhlmann, S.
    Marriner, J.
    Pain, R.
    Regnault, N.
    Balland, C.
    Bassett, B. A.
    Brown, P. J.
    Campbell, H.
    Carlberg, R. G.
    Cellier-Holzern, F.
    Cinabro, D.
    Conley, A.
    D'Andrea, C. B.
    DePoy, D. L.
    Doi, M.
    Ellis, R. S.
    Fabbro, S.
    Filippenko, A. V.
    Foley, R. J.
    Frieman, J. A.
    Fouchez, D.
    Galbany, L.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gupta, R. R.
    Hill, G. J.
    Hlozek, R.
    Hogan, C. J.
    Hook, I. M.
    Howell, D. A.
    Jha, S. W.
    Le Guillou, L.
    EGENLeloudas, G.
    Lidrnan, C.
    Marshall, J. L.
    Moeller, A.
    Mourao, A. M.
    Neveu, J.
    Nichol, R.
    Olmstead, M. D.
    Palanque-Delabrouille, N.
    Perlinutter, S.
    Prieto, J. L.
    Pritchet, C. J.
    Richinond, M.
    Riess, A. G.
    Ruhlmann-Kleider, V.
    Sako, M.
    Sehahmaneche, K.
    Schneider, D. P.
    Smith, M.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sullivan, M.
    Walton, N. A.
    Wheeler, C. J.
    Improved cosmological constraints from a joint analysis of the SDSS-II and SNLS supernova samples2014In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 568, p. A22-Article in journal (Refereed)
    Abstract [en]

    Aims. We present cosmological constraints from a joint analysis of type la supernova (SN Ia) observations obtained by the SDSS-II and SNLS collaborations. The dataset includes several low-redshift samples (z < 0.1), all three seasons from the SDSS-11 (0.05 < z < 0.4), and three years from SNLS (0.2 < z < 1), and it totals 740 spectroscopically confirmed type la supernovae with high quality light curves. Methods. We followed the methods and assumptions of the SNLS three-year data analysis except for the following important improvements: I) the addition of the full SDSS-II spectroscopically-confirmed SN la sample in both the training of the SALT2 light-curve model and in the Hubble diagram analysis (374 SNe); 2) intercalibration of the SNLS and SDSS surveys and reduced systematic uncertainties in the photometric calibration, performed blindly with respect to the cosmology analysis; and 3) a thorough investigation of systematic errors associated with the SALT2 modeling of SN la light curves. Results. We produce recalibrated SN la light curves and associated distances for the SDSS-II and SNLS samples. The large SOSS-II sample provides an effective, independent, low -z anchor for the Hubble diagram and reduces the systematic error from calibration systematics in the low -z SN sample. For a flat ACDM cosmology, we find Omega(m), = 0.295 0.034 (stat+sys), a value consistent with the most recent cosmic microwave background (CMB) measurement from the Planck and WMAP experiments. Our result is 1.8 sigma (stat+sys) different than the previously published result of SNLS three-year data. The change is due primarily to improvements in the SNLS photometric calibration. When combined with CMB constraints, we measure a constant dark energy equation of state parameter omega = -1.018 +/- 0,057 (sral+sys) for a fiat universe. Adding baryon acoustic oscillation distance measurements gives similar constraints: omega = 59 -1.027 0.055. Our supernova measurements provide the most stringent constraints to date on the nature of dark energy.

  • 17. Boldt, Luis N.
    et al.
    Stritzinger, Maximilian D.
    Burns, Chris
    Hsiao, Eric
    Phillips, M. M.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Marion, G. H.
    Stanishev, Vallery
    Near-Infrared K Corrections of Type Ia Supernovae and their Errors2014In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 126, no 938, p. 324-337Article in journal (Refereed)
    Abstract [en]

    In this paper we use near-infrared (NIR) spectral observations of Type Ia supernovae (SNe Ia) to study the uncertainties inherent in NIR K corrections. To do so, 75 previously published NIR spectra of 33 SNe Ia are employed to determine K-correction uncertainties in the YJHK(s) passbands as a function of temporal phase and redshift. The resultant K corrections are then fed into an interpolation algorithm that provides mean K corrections as a function of temporal phase and robust estimates of the associated errors. These uncertainties are both statistical and intrinsic-i.e., due to the diversity of spectral features from object to object and must be included in the overall error budget of cosmological parameters constrained through the use of NIR observations of SNe Ia. Intrinsic variations are likely the dominant source of error for all four passbands at maximum light. Given the present data, the total Y-band K-correction uncertainties at maximum are smallest, amounting to +/- 0.04 mag at a redshift of z = 0.08. The J-band K-term errors are also reasonably small (+/- 0.06 mag), but intrinsic variations of spectral features and noise introduced by telluric corrections in the H-band currently limit its total K-correction errors at maximum to +/- 0.10 mag at z = 0.08. Finally, uncertainties in the K-s-band K terms at maximum amount to +/- 0.07 mag at this same redshift. These results are largely constrained by the small number of published NIR spectra of SNe Ia, which do not yet allow spectral templates to be constructed as a function of the light curve decline rate.

  • 18.
    Bulla, Mattia
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Feindt, Ulrich
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Estimating dust distances to Type Ia supernovae from colour excess time evolution2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 473, no 2, p. 1918-1929Article in journal (Refereed)
    Abstract [en]

    We present a new technique to infer dust locations towards reddened Type Ia supernovae and to help discriminate between an interstellar and a circumstellar origin for the observed extinction. Using Monte Carlo simulations, we show that the time evolution of the light-curve shape and especially of the colour excess E(B - V) places strong constraints on the distance between dust and the supernova. We apply our approach to two highly reddened Type Ia supernovae for which dust distance estimates are available in the literature: SN 2006X and SN 2014J. For the former, we obtain a time-variable E(B - V) and from this derive a distance of 27.5(-4.9)(+ 9.0) or 22.1(-3.8)(+ 6.0) pc depending on whether dust properties typical of the Large Magellanic Cloud (LMC) or the Milky Way (MW) are used. For the latter, instead, we obtain a constant E(B - V) consistent with dust at distances larger than similar to 50 and 38 pc for LMC-and MW-type dust, respectively. Values thus extracted are in excellent agreement with previous estimates for the two supernovae. Our findings suggest that dust responsible for the extinction towards these supernovae is likely to be located within interstellar clouds. We also discuss how other properties of reddened Type Ia supernovae - such as their peculiar extinction and polarization behaviour and the detection of variable, blue-shifted sodium features in some of these events - might be compatible with dust and gas at interstellar-scale distances.

  • 19.
    Bulla, Mattia
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Dhawan, Suhail
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Shedding light on the Type Ia supernova extinction puzzle: dust location found2018In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 479, no 3, p. 3663-3674Article in journal (Refereed)
    Abstract [en]

    The colour evolution of reddened Type Ia supernovae can place strong constraints on the location of dust and help address the question of whether the observed extinction stems from the interstellar medium or from circumstellar material surrounding the progenitor. Here, we analyse BV photometry of 48 reddened Type Ia supernovae from the literature and estimate the dust location from their B - V colour evolution. We find a time-variable colour excess E(B - V) for 15 supernovae in our sample and constrain dust to distances between 0.013 and 45 pc (4 x 10(16)-10(20) cm). For the remaining supernovae, we obtain a constant E(B - V) evolution and place lower limits on the dust distance from the explosion. In all the 48 supernovae, the inferred dust location is compatible with an interstellar origin for the extinction. This is corroborated by the observation that supernovae with relatively nearby dust (less than or similar to 1 pc) are located close to the centre of their host galaxy in high-density dusty regions, where interactions between the supernova radiation and interstellar clouds close by are likely to occur. For supernovae showing time-variable E(B - V), we identify a potential preference for low-R-V values, unusually strong sodium absorption, and blue-shifted and time-variable absorption features. Within the interstellar framework, this brings evidence to a proposed scenario, where cloud-cloud collisions induced by the supernova radiation pressure can shift the grain size distribution to smaller values and enhance the abundance of sodium in the gaseous phase.

  • 20. Cao, Yi
    et al.
    Johansson, J.
    Nugent, Peter E.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nordin, Jakob
    Kulkarni, S. R.
    Cenko, S. Bradley
    Fox, Ori D.
    Kasliwal, Mansi M.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hsiao, E. Y.
    Perley, D. A.
    Bue, Brian D.
    Masci, Frank J.
    Lee, William H.
    Chotard, Nicolas
    ABSENCE OF FAST-MOVING IRON IN AN INTERMEDIATE TYPE Ia SUPERNOVA BETWEEN NORMAL AND SUPER-CHANDRASEKHAR2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 823, no 2, article id 147Article in journal (Refereed)
    Abstract [en]

    In this paper, we report observations of a peculiar SN Ia iPTF13asv (a.k.a., SN2013cv) from the onset of the explosion to months after its peak. The early-phase spectra of iPTF13asv show an absence of iron absorption, indicating that synthesized iron elements are confined to low-velocity regions of the ejecta, which, in turn, implies a stratified ejecta structure along the line of sight. Our analysis of iPTF13asv's light curves and spectra shows that it is an intermediate case between normal and super-Chandrasekhar events. On the one hand, its light curve shape (B-band Delta m(15)=1.03 +/- 0.01) and overall spectral features resemble those of normal SNe Ia. On the other hand, its large peak optical and UV luminosity (M-B = -19.84 mag, M-uvm2 = -15.5 mag) and its low but almost constant Si II velocities of about 10,000 km s (1) are similar to those in super-Chandrasekhar events, and its persistent carbon signatures in the spectra are weaker than those seen commonly in super-Chandrasekhar events. We estimate a Ni-56 mass of 0.81(-0.18)(+0.10) M-circle dot and a total ejecta mass of 1.59(-0.12)(+0.45) M-circle dot. The large ejecta mass of iPTF13asv and its stratified ejecta structure together seemingly favor a double-degenerate origin.

  • 21. Cao, Yi
    et al.
    Kulkarni, S. R.
    Howell, D. Andrew
    Gal-Yam, Avishay
    Kasliwal, Mansi M.
    Valenti, Stefano
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Horesh, Assaf
    Sagiv, Ilan
    Cenko, S. Bradley
    Nugent, Peter E.
    Arcavi, Iair
    Surace, Jason
    Wozniak, P. R.
    Moody, Daniela I.
    Rebbapragada, Umaa D.
    Bue, Brian D.
    Gehrels, Neil
    A strong ultraviolet pulse from a newborn type Ia supernova2015In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 521, no 7552, p. 328-+Article in journal (Refereed)
    Abstract [en]

    Type Ia supernovae(1) are destructive explosions of carbon-oxygen white dwarfs(2,3). Although they are used empirically to measure cosmological distances(4-6), the nature of their progenitors remains mysterious(3). One of the leading progenitor models, called the single degenerate channel, hypothesizes that a white dwarf accretes matter from a companion star and the resulting increase in its central pressure and temperature ignites thermonuclear explosion(3,7,8). Here we report observations with the Swift Space Telescope of strong but declining ultraviolet emission from a type Ia supernova within four days of its explosion. This emission is consistent with theoretical expectations of collision between material ejected by the supernova and a companion star(9), and therefore provides evidence that some type Ia supernovae arise from the single degenerate channel.

  • 22. D'Andrea, Chris B.
    et al.
    Sako, Masao
    Dilday, Benjamin
    Frieman, Joshua A.
    Holtzman, Jon
    Kessler, Richard
    Konishi, Kohki
    Schneider, D. P.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy.
    Wheeler, J. Craig
    Yasuda, Naoki
    Cinabro, David
    Jha, Saurabh
    Nichol, Robert C.
    Lampeitl, Hubert
    Smith, Mathew
    Atlee, David W.
    Bassett, Bruce
    Castander, Francisco J.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Miquel, Ramon
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Östman, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    Prieto, José L.
    Quimby, Robert
    Riess, Adam G.
    Stritzinger, Maximilian
    Type II-P Supernovae from the SDSS-II Supernova Survey and the Standardized Candle Method2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 708, no 1, p. 661-674Article in journal (Refereed)
    Abstract [en]

    We apply the Standardized Candle Method (SCM) for Type II Plateau supernovae (SNe II-P), which relates the velocity of the ejecta of a SN to its luminosity during the plateau, to 15 SNe II-P discovered over the three season run of the Sloan Digital Sky Survey-II Supernova Survey. The redshifts of these SNe—0.027 < z < 0.144—cover a range hitherto sparsely sampled in the literature; in particular, our SNe II-P sample contains nearly as many SNe in the Hubble flow (z > 0.01) as all of the current literature on the SCM combined. We find that the SDSS SNe have a very small intrinsic I-band dispersion (0.22 mag), which can be attributed to selection effects. When the SCM is applied to the combined SDSS-plus-literature set of SNe II-P, the dispersion increases to 0.29 mag, larger than the scatter for either set of SNe separately. We show that the standardization cannot be further improved by eliminating SNe with positive plateau decline rates, as proposed in Poznanski et al. We thoroughly examine all potential systematic effects and conclude that for the SCM to be useful for cosmology, the methods currently used to determine the Fe II velocity at day 50 must be improved, and spectral templates able to encompass the intrinsic variations of Type II-P SNe will be needed. Based in part on data collected at Subaru Telescope, which is operated by the National Astronomical Observatory of Japan.

  • 23. Dawson, K. S.
    et al.
    Aldering, G.
    Amanullah, R.
    Barbary, K.
    Barrientos, L. F.
    Brodwin, M.
    Connolly, N.
    Dey, A.
    Doi, M.
    Donahue, M.
    Eisenhardt, P.
    Ellingson, E.
    Faccioli, L.
    Fadeyev, V.
    Fakhouri, H. K.
    Fruchter, A. S.
    Gilbank, D. G.
    Gladders, M. D.
    Goldhaber, G.
    Gonzalez, A. H.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Gude, A.
    Hattori, T.
    Hoekstra, H.
    Huang, X.
    Ihara, Y.
    Jannuzi, B. T.
    Johnston, D.
    Kashikawa, K.
    Koester, B.
    Konishi, K.
    Kowalski, M.
    Lidman, C.
    Linder, E. V.
    Lubin, L.
    Meyers, J.
    Morokuma, T.
    Munshi, F.
    Mullis, C.
    Oda, T.
    Panagia, N.
    Perlmutter, S.
    Postman, M.
    Pritchard, T.
    Rhodes, J.
    Rosati, P.
    Rubin, D.
    Schlegel, D. J.
    Spadafora, A.
    Stanford, S. A.
    Stanishev, Vallery
    Stern, D.
    Strovink, M.
    Suzuki, N.
    Takanashi, N.
    Tokita, K.
    Wagner, M.
    Wang, L.
    Yasuda, N.
    Yee, H. K. C.
    Supernova Cosmology Project, The
    An Intensive Hubble Space Telescope Survey for z>1 Type Ia Supernovae by Targeting Galaxy Clusters2009In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 138, p. 1271-1283Article in journal (Refereed)
    Abstract [en]

    We present a new survey strategy to discover and study high-redshift Type Ia supernovae (SNe Ia) using the Hubble Space Telescope (HST). By targeting massive galaxy clusters at 0.9 < z < 1.5, we obtain a twofold improvement in the efficiency of finding SNe compared to an HST field survey and a factor of 3 improvement in the total yield of SN detections in relatively dust-free red-sequence galaxies. In total, sixteen SNe were discovered at z>0.95, nine of which were in galaxy clusters. This strategy provides an SN sample that can be used to decouple the effects of host-galaxy extinction and intrinsic color in high-redshift SNe, thereby reducing one of the largest systematic uncertainties in SN cosmology. Based on observations made with the NASA/ESA Hubble Space Telescope and obtained from the data archive at the Space Telescope Institute. STScI is operated by the Association of Universities for Research in Astronomy, Inc. under the NASA contract NAS 5-26555. The observations are associated with program 10496.

  • 24.
    Dhawan, Suhail
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    The effect of inhomogeneities on dark energy constraints2018In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 024Article in journal (Refereed)
    Abstract [en]

    Constraints on models of the late time acceleration of the universe assume the cosmological principle of homogeneity and isotropy on large scales. However, small scale inhomogeneities can alter observational and dynamical relations, affecting the inferred cosmological parameters. For precision constraints on the properties of dark energy, it is important to assess the potential systematic effects arising from these inhomogeneities. In this study, we use the Type Ia supernova magnitude-redshift relation to constrain the inhomogeneities as described by the Dyer-Roeder distance relation and the effect they have on the dark energy equation of state (w), together with priors derived from the most recent results of the measurements of the power spectrum of the Cosmic Microwave Background and Baryon Acoustic Oscillations. We find that the parameter describing the inhomogeneities (eta) is weakly correlated with w. The best fit values w = -0.933 +/- 0.065 and eta = 0.61 +/- 0.37 are consistent with homogeneity at < 2 sigma level. Assuming homogeneity (eta = 1), we find w = -0.961 +/- 0.055, indicating only a small change in w. For a time-dependent dark energy equation of state, w(0) = -0.951 +/- 0.112 and w(a) = 0.059 +/- 0.418, to be compared with w(0) = -0.983 +/- 0.127 and w(a) = 0.07 +/- 0.432 in the homogeneous case, which is also a very small change. We do not obtain constraints on the fraction of dark matter in compact objects, f(p), at the 95% C.L. with conservative corrections to the distance formalism. Future supernova surveys will improve the constraints on eta, and hence, f(p), by a factor of similar to 10.

  • 25.
    Dhawan, Suhail
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Feindt, Ulrich
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Narrowing down the possible explanations of cosmic acceleration with geometric probes2017In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, E-ISSN 1475-7516, no 7, article id 040Article in journal (Refereed)
    Abstract [en]

    Recent re-calibration of the Type Ia supernova (SNe Ia) magnitude-redshift relation combined with cosmic microwave background (CMB) and baryon acoustic oscillation (BAO) data have provided excellent constraints on the standard cosmological model. Here, we examine particular classes of alternative cosmologies, motivated by various physical mechanisms, e.g. scalar fields, modified gravity and phase transitions to test their consistency with observations of SNe Ia and the ratio of the angular diameter distances from the CMB and BAO. Using a model selection criterion for a relative comparison of the models (the Bayes Factor), we find moderate to strong evidence that the data prefer flat Lambda CDM over models invoking a thawing behaviour of the quintessence scalar field. However, some exotic models like the growing neutrino mass cosmology and vacuum metamorphosis still present acceptable evidence values. The bimetric gravity model with only the linear interaction term as well as a simplified Galileon model can be ruled out by the combination of SNe Ia and CMB/BAO datasets whereas the model with linear and quadratic interaction terms has a comparable evidence value to standard Lambda CDM. Thawing models are found to have significantly poorer evidence compared to flat Lambda CDM cosmology under the assumption that the CMB compressed likelihood provides an adequate description for these non-standard cosmologies. We also present estimates for constraints from future data and find that geometric probes from oncoming surveys can put severe limits on non-standard cosmological models.

  • 26. Dilday, Benjamin
    et al.
    Bassett, Bruce
    Becker, Andrew
    Bender, Ralf
    Castander, Francisco
    Cinabro, David
    Frieman, Joshua A.
    Galbany, Lluís
    Garnavich, Peter
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hopp, Ulrich
    Ihara, Yutaka
    Jha, Saurabh W.
    Kessler, Richard
    Lampeitl, Hubert
    Marriner, John
    Miquel, Ramon
    Mollá, Mercedes
    Nichol, Robert C.
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Riess, Adam G.
    Sako, Masao
    Schneider, Donald P.
    Smith, Mathew
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Wheeler, J. Craig
    Östman, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    Bizyaev, Dmitry
    Brewington, Howard
    Malanushenko, Elena
    Malanushenko, Viktor
    Oravetz, Dan
    Pan, Kaike
    Simmons, Audrey
    Snedden, Stephanie
    A Measurement of the Rate of Type Ia Supernovae in Galaxy Clusters from the SDSS-II Supernova Survey2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 715, p. 1021-1035Article in journal (Refereed)
    Abstract [en]

    We present measurements of the Type Ia supernova (SN) rate in galaxy clusters based on data from the Sloan Digital Sky Survey-II (SDSS-II) Supernova Survey. The cluster SN Ia rate is determined from 9 SN events in a set of 71 C4 clusters at z <= 0.17 and 27 SN events in 492 maxBCG clusters at 0.1 <= z <= 0.3. We find values for the cluster SN Ia rate of (0.37+0.17+0.01 -0.12-0.01) SNur h 2 and (0.55+0.13+0.02 -0.11-0.01) SNur h 2 (SNux = 10-12 L -1 xsun yr-1) in C4 and maxBCG clusters, respectively, where the quoted errors are statistical and systematic, respectively. The SN rate for early-type galaxies is found to be (0.31+0.18+0.01 -0.12-0.01) SNur h 2 and (0.49+0.15+0.02 -0.11-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The SN rate for the brightest cluster galaxies (BCG) is found to be (2.04+1.99+0.07 -1.11-0.04) SNur h 2 and (0.36+0.84+0.01 -0.30-0.01) SNur h 2 in C4 and maxBCG clusters, respectively. The ratio of the SN Ia rate in cluster early-type galaxies to that of the SN Ia rate in field early-type galaxies is 1.94+1.31+0.043 -0.91-0.015 and 3.02+1.31+0.062 -1.03-0.048, for C4 and maxBCG clusters, respectively. The SN rate in galaxy clusters as a function of redshift, which probes the late time SN Ia delay distribution, shows only weak dependence on redshift. Combining our current measurements with previous measurements, we fit the cluster SN Ia rate data to a linear function of redshift, and find rL = [(0.49+0.15 -0.14)+(0.91+0.85 -0.81) × z] SNuB h 2. A comparison of the radial distribution of SNe in cluster to field early-type galaxies shows possible evidence for an enhancement of the SN rate in the cores of cluster early-type galaxies. With an observation of at most three hostless, intra-cluster SNe Ia, we estimate the fraction of cluster SNe that are hostless to be (9.4+8.3 -5.1)%.

  • 27. Dilday, Benjamin
    et al.
    Smith, Mathew
    Bassett, Bruce
    Becker, Andrew
    Bender, Ralf
    Castander, Francisco
    Cinabro, David
    Filippenko, Alexei V.
    Frieman, Joshua A.
    Galbany, Lluís
    Garnavich, Peter M.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Hopp, Ulrich
    Ihara, Yutaka
    Jha, Saurabh W.
    Kessler, Richard
    Lampeitl, Hubert
    Marriner, John
    Miquel, Ramon
    Mollá, Mercedes
    Nichol, Robert C.
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Riess, Adam G.
    Sako, Masao
    Schneider, Donald P.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy.
    Wheeler, J. Craig
    Östman, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    Bizyaev, Dmitry
    Brewington, Howard
    Malanushenko, Elena
    Malanushenko, Viktor
    Oravetz, Dan
    Pan, Kaike
    Simmons, Audrey
    Snedden, Stephanie
    Measurements of the Rate of Type Ia Supernovae at Redshift lsim0.3 from the Sloan Digital Sky Survey II Supernova Survey2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 713, p. 1026-1036Article in journal (Refereed)
    Abstract [en]

    We present a measurement of the volumetric Type Ia supernova (SN Ia) rate based on data from the Sloan Digital Sky Survey II (SDSS-II) Supernova Survey. The adopted sample of supernovae (SNe) includes 516 SNe Ia at redshift z <~ 0.3, of which 270(52%) are spectroscopically identified as SNe Ia. The remaining 246 SNe Ia were identified through their light curves; 113 of these objects have spectroscopic redshifts from spectra of their host galaxy, and 133 have photometric redshifts estimated from the SN light curves. Based on consideration of 87 spectroscopically confirmed non-Ia SNe discovered by the SDSS-II SN Survey, we estimate that 2.04+1.61 -0.95% of the photometric SNe Ia may be misidentified. The sample of SNe Ia used in this measurement represents an order of magnitude increase in the statistics for SN Ia rate measurements in the redshift range covered by the SDSS-II Supernova Survey. If we assume an SN Ia rate that is constant at low redshift (z < 0.15), then the SN observations can be used to infer a value of the SN rate of rV = (2.69+0.34+0.21 -0.30-0.01)×10-5 SNe yr-1 Mpc-3 (H 0/(70 km s-1 Mpc-1))3 at a mean redshift of ~0.12, based on 79 SNe Ia of which 72 are spectroscopically confirmed. However, the large sample of SNe Ia included in this study allows us to place constraints on the redshift dependence of the SN Ia rate based on the SDSS-II Supernova Survey data alone. Fitting a power-law model of the SN rate evolution, rV (z) = Ap × ((1 + z)/(1 + z 0))ν, over the redshift range 0.0 < z < 0.3 with z 0 = 0.21, results in Ap = (3.43+0.15 -0.15) × 10-5 SNe yr-1 Mpc-3 (H 0/(70 km s-1 Mpc-1))3 and ν = 2.04+0.90 -0.89.

  • 28.
    Ferretti, Raphael
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Joel
    Lundqvist, Peter
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    No evidence of circumstellar gas surrounding Type Ia Supernova SN 2017cbvIn: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213Article in journal (Refereed)
  • 29.
    Ferretti, Raphael
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Joel
    Lundqvist, Peter
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    No Evidence of Circumstellar Gas Surrounding Type Ia Supernova SN 2017cbv2017In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 851, no 2, article id L43Article in journal (Refereed)
    Abstract [en]

    Nearby type Ia supernovae (SNe Ia), such as SN 2017cbv, are useful events to address the question of what the elusive progenitor systems of the explosions are. Hosseinzadeh et al. suggested that the early blue excess of the light curve of SN 2017cbv could be due to the supernova ejecta interacting with a non-degenerate companion star. Some SN Ia progenitor models suggest the existence of circumstellar (CS) environments in which strong outflows create low-density cavities of different radii. Matter deposited at the edges of the cavities should be at distances at which photoionization due to early ultraviolet (UV) radiation of SNe. Ia causes detectable changes to the observable Na I D and Ca II H&K absorption lines. To study possible narrow absorption lines from such material, we obtained a time series of high-resolution spectra of SN 2017cbv at phases between -14.8 and +83 days with respect to B-band maximum, covering the time at which photoionization is predicted to occur. Both narrow Na I D and Ca II H&K are detected in all spectra, with no measurable changes between the epochs. We use photoionization models to rule out the presence of Na I and Ca II gas clouds along the line of sight of SN 2017cbv between similar to 8 x 10(16)-2 x 10(19) cm and similar to 10(15)-10(17) cm, respectively. Assuming typical abundances, the mass of a homogeneous spherical CS gas shell with radius R must be limited to M-HI(CSM) < 3 x 10(-4) x (R/10(17)[cm(2)]) M-circle dot. The bounds point to progenitor models that deposit little gas in their CS environment.

  • 30.
    Ferretti, Raphael
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, J.
    Vreeswijk, P. M.
    Butler, R. P.
    Cao, Y.
    Cenko, S. B.
    Doran, G.
    Filippenko, A. V.
    Freeland, Emily
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hosseinzadeh, G.
    Howell, D. A.
    Lundqvist, P.
    Mattila, S.
    Nordin, J.
    Nugent, P. E.
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Valenti, S.
    Vogt, S.
    Wozniak, P.
    Time-varying sodium absorption in the Type Ia supernova 2013gh2016In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 592, article id A40Article in journal (Refereed)
    Abstract [en]

    Context. Temporal variability of narrow absorption lines in high-resolution spectra of Type Ia supernovae (SNe Ia) is studied to search for circumstellar matter. Time series which resolve the profiles of absorption lines such as Na I D or Ca II H&K are expected to reveal variations due to photoionisation and subsequent recombination of the gases. The presence, composition, and geometry of circumstellar matter may hint at the elusive progenitor system of SNe Ia and could also affect the observed reddening law. Aims. To date, there are few known cases of time-varying Na I D absorption in SNe Ia, all of which occurred during relatively late phases of the supernova (SN) evolution. Photoionisation, however, is predicted to occur during the early phases of SNe Ia, when the supernovae peak in the ultraviolet. We attempt, therefore, to observe early-time absorption-line variations by obtaining high-resolution spectra of SNe before maximum light. Methods. We have obtained photometry and high-resolution spectroscopy of SNe Ia 2013gh and iPTF 13dge, to search for absorption-line variations. Furthermore, we study interstellar absorption features in relation to the observed photometric colours of the SNe. Results. Both SNe display deep Na I D and Ca II H&K absorption features. Furthermore, small but significant variations are detected in a feature of the Na I D profile of SN 2013gh. The variations are consistent with either geometric effects of rapidly moving or patchy gas clouds or photoionisation of Na I gas at R approximate to 10(19) cm from the explosion. Conclusions. Our analysis indicates that it is necessary to focus on early phases to detect photoionisation effects of gases in the circumstellar medium of SNe Ia. Different absorbers such as Na I and Ca II can be used to probe for matter at different distances from the SNe. The nondetection of variations during early phases makes it possible to put limits on the abundance of the species at those distances.

  • 31.
    Ferretti, Raphael
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Borthakur, S.
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fox, O.
    Freeland, Emily
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hangard, Laura
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hayes, Matthew
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Probing gas and dust in the tidal tail of NGC 5221 with the type Ia supernova iPTF16abc2017In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 606, article id A111Article in journal (Refereed)
    Abstract [en]

    Context. Type Ia supernovae (SNe Ia) can be used to address numerous questions in astrophysics and cosmology. Due to their wellknown spectral and photometric properties, SNe Ia are well suited to study gas and dust along the lines-of-sight to the explosions. For example, narrow Na I D and Ca II H&K absorption lines can be studied easily, because of the well-defined spectral continuum of SNe Ia around these features.

    Aims. We aim to study the gas and dust along the line-of-sight to iPTF16abc, which occurred in an unusual location, in a tidal arm, 80 kpc from centre of the galaxy NGC 5221.

    Methods. Using a time-series of high-resolution spectra, we have examined narrow Na I D and Ca II H&K absorption features for variations in time, which would be indicative for circumstellar (CS) matter. Furthermore, we have taken advantage of the well known photometric properties of SNe Ia to determine reddening due to dust along the line-of-sight.

    Results. From the lack of variations in Na I D and Ca II H&K, we determine that none of the detected absorption features originate from the CS medium of iPTF16abc. While the Na I D and Ca II H&K absorption is found to be optically thick, a negligible amount of reddening points to a small column of interstellar dust.

    Conclusions. We find that the gas along the line-of-sight to iPTF16abc is typical of what might be found in the interstellar medium (ISM) within a galaxy. It suggests that we are observing gas that has been tidally stripped during an interaction of NGC 5221 with one of its neighbouring galaxies in the past ~109 years. In the future, the gas clouds could become the locations of star formation. On a longer time scale, the clouds might diuse, enriching the circum-galactic medium (CGM) with metals. The gas profile along the line-of-sight should be useful for future studies of the dynamics of the galaxy group containing NGC 5221.

  • 32. Frieman, Josh
    et al.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Östman, Linda
    Stockholm University, Faculty of Science, Department of Physics.
    The Sloan Digital Sky Survey-II Supernova Survey: Technical Summary2008In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 135, no 1, p. 338-347Article in journal (Refereed)
    Abstract [en]

    The Sloan Digital Sky Survey-II (SDSS-II) has embarked on a multi-year project to identify and measure light curves for intermediate-redshift (0.05 < z < 0.35) Type Ia supernovae (SNe Ia) using repeated five-band (ugriz) imaging over an area of 300 sq. deg. The survey region is a stripe 2.5° wide centered on the celestial equator in the Southern Galactic Cap that has been imaged numerous times in earlier years, enabling construction of a deep reference image for the discovery of new objects. Supernova imaging observations are being acquired between September 1 and November 30 of 2005-7. During the first two seasons, each region was imaged on average every five nights. Spectroscopic follow-up observations to determine supernova type and redshift are carried out on a large number of telescopes. In its first two three-month seasons, the survey has discovered and measured light curves for 327 spectroscopically confirmed SNe Ia, 30 probable SNe Ia, 14 confirmed SNe Ib/c, 32 confirmed SNe II, plus a large number of photometrically identified SNe Ia, 94 of which have host-galaxy spectra taken so far. This paper provides an overview of the project and briefly describes the observations completed during the first two seasons of operation.

  • 33. Garavini, G
    et al.
    Folatelli, Gastón
    Stockholm University, Faculty of Science, Department of Physics.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Nobili, Serena
    al., et
    Spectroscopic Observations and Analysis of the Peculiar SN 1999aa2004In: Astronomical Journal, ISSN 0004-6256, E-ISSN 1538-3881, Vol. 128, p. 387-404Article in journal (Refereed)
    Abstract [en]

    We present an extensive new time series of spectroscopic data of the peculiar SN 1999aa in NGC 2595. Ourdata set includes 25 optical spectra between 11 and +58 days with respect to B-band maximum light, providingan unusually complete time history. The early spectra resemble those of an SN 1991T–like object but with arelatively strong Ca H and K absorption feature. The first clear sign of Si ii k6355, characteristic of Type Iasupernovae, is found at day 7, and its velocity remains constant up to at least the first month after B-bandmaximum light. The transition to normal-looking spectra is found to occur earlier than in SN 1991T, suggestingSN 1999aa as a possible link between SN 1991T–like and Branch-normal supernovae. Comparing the observationswith synthetic spectra, doubly ionized Fe, Si, and Ni are identified at early epochs. These are characteristicof SN 1991T–like objects. Furthermore, in the day 11 spectrum, evidence is found for an absorptionfeature that could be identified as high velocity C ii k6580 or H. At the same epoch C iii k4648.8 at photosphericvelocity is probably responsible for the absorption feature at 4500 8. High-velocity Ca is found aroundmaximum light together with Si ii and Fe ii confined in a narrow velocity window. Implied constraints onsupernovae progenitor systems and explosion hydrodynamic models are briefly discussed.

  • 34.
    Goobar, Ariel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Stockholm University, Faculty of Science, Department of Physics.
    Kulkarni, S. R.
    Nugent, P. E.
    Johansson, Joel
    Steidel, C.
    Law, D.
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Quimby, Robert
    Blagorodnova, N.
    Brandeker, A.
    Cao, Y.
    Cooray, A.
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hangard, Laura
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwai, M.
    Kupfer, T.
    Lunnan, R.
    Masci, F.
    Miller, A. A.
    Nayyeri, H.
    Neill, J. D.
    Ofek, E. O.
    Papadogiannakis, Seméli
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ravi, V.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sullivan, M.
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Walters, R.
    Wilson, D.
    Yan, L.
    Yaron, O.
    iPTF16geu: A multiply imaged, gravitationally lensed type Ia supernova2017In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 356, no 6335, p. 291-295Article in journal (Refereed)
    Abstract [en]

    We report the discovery of a multiply imaged, gravitationally lensed type Ia supernova, iPTF16geu (SN 2016geu), at redshift z = 0.409. This phenomenon was identified because the light from the stellar explosion was magnified more than 50 times by the curvature of space around matter in an intervening galaxy. We used high-spatial-resolution observations to resolve four images of the lensed supernova, approximately 0.3 arc seconds from the center of the foreground galaxy. The observations probe a physical scale of ~1 kiloparsec, smaller than is typical in other studies of extragalactic gravitational lensing. The large magnification and symmetric image configuration imply close alignment between the lines of sight to the supernova and to the lens. The relative magnifications of the four images provide evidence for substructures in the lensing galaxy.

  • 35.
    Goobar, Ariel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cao, Y.
    Perley, D. A.
    Kasliwal, M. M.
    Ferretti, Raphael
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nugent, P. E.
    Harris, C.
    Gal-Yam, A.
    Ofek, E. O.
    Tendulkar, S. P.
    Dennefeld, M.
    Valenti, S.
    Arcavi, I.
    Banerjee, D. P. K.
    Venkataraman, V.
    Joshi, V.
    Ashok, N. M.
    Cenko, S. B.
    Diaz, R. F.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Horesh, A.
    Howell, D. A.
    Kulkarni, S. R.
    Papadogiannakis, Seméli
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Petrushevska, Tanja
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Sand, D.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stanishev, V.
    Bloom, J. S.
    Surace, J.
    Dupuy, T. J.
    Liu, M. C.
    THE RISE OF SN 2014J IN THE NEARBY GALAXY M822014In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 784, no 1, article id L12Article in journal (Refereed)
    Abstract [en]

    We report on the discovery of SN 2014J in the nearby galaxy M82. Given its proximity, it offers the best opportunity to date to study a thermonuclear supernova (SN) over a wide range of the electromagnetic spectrum. Optical, near-IR, and mid-IR observations on the rising light curve, orchestrated by the intermediate Palomar Transient Factory, show that SN 2014J is a spectroscopically normal Type Ia supernova (SN Ia), albeit exhibiting high-velocity features in its spectrum and heavily reddened by dust in the host galaxy. Our earliest detections start just hours after the fitted time of explosion. We use high-resolution optical spectroscopy to analyze the dense intervening material and do not detect any evolution in the resolved absorption features during the light curve rise. Similar to other highly reddened SNe Ia, a low value of total-to-selective extinction, R-V less than or similar to 2, provides the best match to our observations. We also study pre-explosion optical and near-IR images from Hubble Space Telescope with special emphasis on the sources nearest to the SN location.

  • 36.
    Goobar, Ariel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kromer, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Siverd, R.
    Stassun, K. G.
    Pepper, J.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwal, M.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    CONSTRAINTS ON THE ORIGIN OF THE FIRST LIGHT FROM SN 2014J2015In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 799, no 1, p. 106-Article in journal (Refereed)
    Abstract [en]

    We study the very early light curve of supernova 2014J (SN 2014J) using the high-cadence broad-band imaging data obtained by the Kilodegree Extremely Little Telescope, which fortuitously observed M 82 around the time of the explosion, starting more than 2 months prior to detection, with up to 20 observations per night. These observations are complemented by observations in two narrow-band filters used in an Ha survey of nearby galaxies by the intermediate Palomar Transient Factory that also captured the first days of the brightening of the supernova. The evolution of the light curves is consistent with the expected signal from the cooling of shock heated material of large scale dimensions, greater than or similar to 1R(circle dot). This could be due to heated material of the progenitor, a companion star or pre-existing circumstellar environment, e.g., in the form of an accretion disk. Structure seen in the light curves during the first days after explosion could also originate from radioactive material in the outer parts of an exploding white dwarf, as suggested from the early detection of gamma-rays. The model degeneracy translates into a systematic uncertainty of +/- 0.3 days on the estimate of the first light from SN 2014J.

  • 37.
    Goobar, Ariel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Leibundgut, Bruno
    Supernova Cosmology: Legacy and Future2011In: Annual Review of Nuclear and Particle Science, ISSN 0163-8998, E-ISSN 1545-4134, Vol. 61, p. 251-279Article, review/survey (Refereed)
    Abstract [en]

    The discovery of dark energy by the first generation of high-redshift supernova surveys has generated enormous interest beyond cosmology and has dramatic implications for fundamental physics. Distance measurements using supernova explosions are the most direct probes of the expansion history of the universe, making them extremely useful tools with which to study the cosmic fabric and the properties of gravity at the largest scales. The past decade has seen confirmation of the original results. Type Ia supernovae are among the leading techniques to obtain high-precision measurements of the dark energy equation-of-state parameter and, in the near future, its time dependence. The success of these efforts depends on our ability to understand a large number of effects, mostly of an astrophysical nature, that influence the observed flux at Earth. The frontier now lies in understanding whether the observed phenomenon is due to vacuum energy, despite its unnatural density, or some exotic new physics. Future surveys will address the systematic effects with improved calibration procedures and will provide thousands of supernovae for detailed studies.

  • 38.
    Goobar, Ariel
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Paech, Kerstin
    Stockholm University, Faculty of Science, Department of Physics.
    Stanishev, Vallery
    Stockholm University, Faculty of Science, Department of Physics.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics.
    Dahlén, T.
    Jönsson, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Kneib, J. P.
    Lidman, Chris
    Stockholm University, Faculty of Science, Department of Physics.
    Limousin, M.
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics.
    Nobili, Serena
    Stockholm University, Faculty of Science, Department of Physics.
    Richard, J.
    Riehm, Teresa
    Stockholm University, Faculty of Science, Department of Astronomy.
    von Strauss, Mikael
    Stockholm University, Faculty of Science, Department of Physics.
    Near-IR search for lensed supernovae behind galaxy clusters. II. First detection and future prospects2009In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 507, no 1, p. 71-83Article in journal (Refereed)
    Abstract [en]

    Aims: Powerful gravitational telescopes in the form of massive galaxy clusters can be used to enhance the light collecting power over a limited field of view by about an order of magnitude in flux. This effect is exploited here to increase the depth of a survey for lensed supernovae at near-IR wavelengths.

    Methods: We present a pilot supernova search programme conducted with the ISAAC camera at VLT. Lensed galaxies behind the massive clusters A1689, A1835, and AC114 were observed for a total of 20 h divided into 2, 3, and 4 epochs respectively, separated by approximately one month to a limiting magnitude J ≲ 24 (Vega). Image subtractions including another 20 h worth of archival ISAAC/VLT data were used to search for transients with lightcurve properties consistent with redshifted supernovae, both in the new and reference data.

    Results: The feasibility of finding lensed supernovae in our survey was investigated using synthetic lightcurves of supernovae and several models of the volumetric type Ia and core-collapse supernova rates as a function of redshift. We also estimate the number of supernova discoveries expected from the inferred star-formation rate in the observed galaxies. The methods consistently predict a Poisson mean value for the expected number of supernovae in the survey of between N_SN = 0.8 and 1.6 for all supernova types, evenly distributed between core collapse and type Ia supernovae. One transient object was found behind A1689, 0.5 arcsec from a galaxy with photometric redshift z_gal = 0.6 ± 0.15. The lightcurve and colors of the transient are consistent with being a reddened type IIP supernova at z_SN = 0.59. The lensing model predicts 1.4 mag of magnification at the location of the transient, without which this object would not have been detected in the near-IR ground-based search described in this paper (unlensed magnitude J ~ 25). We perform a feasibility study of the potential for lensed supernovae discoveries with larger and deeper surveys and conclude that the use of gravitational telescopes is a very exciting path for new discoveries. For example, a monthly rolling supernova search of a single very massive cluster with the HAWK-I camera at VLT would yield ≳ 10 lensed supernova lightcurves per year, where type Ia supernovae would constitute about half of the expected sample. Based on observations made with ESO telescopes at the La Silla Paranal Observatory under programme ID 079.A-0192 and ID 081.A-0734.

  • 39.
    Gunnarsson, C
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Dahlén, T
    Stockholm University, Faculty of Science, Department of Physics.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Jönsson, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Corrections for Gravitational Lensing of Supernovae: Better than Average?2006In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 640, p. 417-427Article in journal (Refereed)
    Abstract [en]

    We investigate the possibility of correcting for magnification due to gravitational lensing of standard candle sources, such as Type Ia supernovae. Our method uses the observed properties of the foreground galaxies along the lines of sight to each source, and the accuracy of the lensing correction depends on the quality and depth of these observations as well as the uncertainties in translating the observed luminosities to the matter distribution in the lensing galaxies. The current work is limited to cases in which the matter density is dominated by the individual galaxy halos. However, it is straightforward to generalize the method to also include gravitational lensing from cluster scale halos. We show that the dispersion due to lensing for a standard candle source at z = 1.5 can be reduced from about 7% to 3%; i.e., the magnification correction is useful in reducing the scatter in the Type Ia Hubble diagram, especially at high redshifts where the required long exposure times make it hard to reach large statistics and the dispersion due to lensing becomes comparable to the intrinsic Type Ia scatter.

  • 40.
    Gunnarsson, Christofer
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Dahlen, Tomas
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Jönsson, Jakob
    Stockholm University, Faculty of Science, Department of Physics.
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics.
    Corrections for gravitational lensing of supernovae: better than average?2006In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 640, p. 417-427Article in journal (Refereed)
    Abstract [en]

    We investigate the possibility of correcting for magnification due to gravitational lensing of standard candlesources, such as Type Ia supernovae. Our method uses the observed properties of the foreground galaxies along thelines of sight to each source, and the accuracy of the lensing correction depends on the quality and depth of theseobservations as well as the uncertainties in translating the observed luminosities to the matter distribution in thelensing galaxies. The current work is limited to cases in which the matter density is dominated by the individualgalaxy halos. However, it is straightforward to generalize the method to also include gravitational lensing fromcluster scale halos.We show that the dispersion due to lensing for a standard candle source at z ¼1:5 can be reducedfrom about 7% toP3%; i.e., the magnification correction is useful in reducing the scatter in the Type Ia Hubble diagram,especially at high redshifts where the required long exposure times make it hard to reach large statistics andthe dispersion due to lensing becomes comparable to the intrinsic Type Ia scatter.

  • 41. Hoffmann, Samantha L.
    et al.
    Macri, Lucas M.
    Riess, Adam G.
    Yuan, Wenlong
    Casertano, Stefano
    Foley, Ryan J.
    Filippenko, Alexei V.
    Tucker, Brad E.
    Chornock, Ryan
    Silverman, Jeffrey M.
    Welch, Douglas L.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    OPTICAL IDENTIFICATION OF CEPHEIDS IN 19 HOST GALAXIES OF TYPE Ia SUPERNOVAE AND NGC 4258 WITH THE HUBBLE SPACE TELESCOPE2016In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 830, no 1, article id 10Article in journal (Refereed)
    Abstract [en]

    We present results of an optical search conducted as part of the SH0ES project (Supernovae and H-0 for the Equation of State of dark energy) for Cepheid variable stars using the Hubble Space Telescope (HST) in 19 hosts of Type Ia supernovae (SNe Ia) and the maser-host galaxy NGC 4258. The targets include nine newly imaged SN. Ia hosts using a novel strategy based on a long-pass filter that minimizes the number of HST orbits required to detect and accurately determine Cepheid properties. We carried out a homogeneous reduction and analysis of all observations, including new universal variability searches in all SN. Ia hosts, which yielded a total of 2200 variables with well-defined selection criteria, the largest such sample identified outside the Local Group. These objects are used in a companion paper to determine the local value of H-0 with a total uncertainty of 2.4%.

  • 42. Hsiao, E. Y.
    et al.
    Burns, C. R.
    Contreras, C.
    Hoeflich, P.
    Sand, D.
    Marion, G. H.
    Phillips, M. M.
    Stritzinger, M.
    Gonzalez-Gaitan, S.
    Mason, R. E.
    Folatelli, G.
    Parent, E.
    Gall, C.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Anupama, G. C.
    Arcavi, I.
    Banerjee, D. P. K.
    Beletsky, Y.
    Blanc, G. A.
    Bloom, J. S.
    Brown, P. J.
    Campillay, A.
    Cao, Y.
    De Cia, A.
    Diamond, T.
    Freedman, W. L.
    Gonzalez, C.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Holmbo, S.
    Howell, D. A.
    Johansson, Joel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwal, M. M.
    Kirshner, R. P.
    Krisciunas, K.
    Kulkarni, S. R.
    Maguire, K.
    Milne, P. A.
    Morrell, N.
    Nugent, P. E.
    Ofek, E. O.
    Osip, D.
    Palunas, P.
    Perley, D. A.
    Persson, S. E.
    Piro, A. L.
    Rabus, M.
    Roth, M.
    Schiefelbein, J. M.
    Srivastav, S.
    Sullivan, M.
    Suntzeff, N. B.
    Surace, J.
    Wozniak, P. R.
    Yaron, O.
    Strong near-infrared carbon in the Type Ia supernova iPTF13ebh2015In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 578, article id A9Article in journal (Refereed)
    Abstract [en]

    We present near-infrared (NIR) time-series spectroscopy, as well as complementary ultraviolet (UV), optical, and NIR data, of the Type Ia supernova (SN Ia) iPTF13ebh, which was discovered within two days from the estimated time of explosion. The first NIR spectrum was taken merely 2 : 3 days after explosion and may be the earliest NIR spectrum yet obtained of a SN Ia. The most striking features in the spectrum are several NIR C I lines, and the C I lambda 1.0693 mu m line is the strongest ever observed in a SN Ia. Interestingly, no strong optical C II counterparts were found, even though the optical spectroscopic time series began early and is densely cadenced. Except at the very early epochs, within a few days from the time of explosion, we show that the strong NIR C I compared to the weaker optical C II appears to be general in SNe Ia. iPTF13ebh is a fast decliner with Delta m(15)(B) = 1.79 +/- 0.01, and its absolute magnitude obeys the linear part of the width-luminosity relation. It is therefore categorized as a transitional event, on the fast-declining end of normal SNe Ia as opposed to subluminous/91bg-like objects. iPTF13ebh shows NIR spectroscopic properties that are distinct from both the normal and subluminous/91bg-like classes, bridging the observed characteristics of the two classes. These NIR observations suggest that composition and density of the inner core are similar to that of 91bg-like events, and that it has a deep-reaching carbon burning layer that is not observed in more slowly declining SNe Ia. There is also a substantial difference between the explosion times inferred from the early-time light curve and the velocity evolution of the Si II lambda 0.6355 mu m line, implying a long dark phase of similar to 4 days.

  • 43.
    Johansson, Joel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Herschel limits on far-infrared emission from circumstellar dust around three nearby Type Ia supernovae2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 431, no 1, p. L43-L47Article in journal (Refereed)
    Abstract [en]

    We report upper limits on dust emission at far-infrared (IR) wavelengths from three nearby Type Ia supernovae: SNe 2011by, 2011fe and 2012cg. Observations were carried out at 70 and 160 mu m with the Photodetector Array Camera and Spectrometer onboard the Herschel Space Observatory. None of the supernovae were detected in the far-IR, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. Due to its proximity, SN 2011fe provides the tightest constraints, M-dust less than or similar to 7 x 10(-3)M(circle dot) at a 3 sigma level for dust temperatures T-dust similar to 500K assuming silicate or graphite dust grains of size a = 0.1 mu m. For SNe 2011by and 2012cg the corresponding upper limits are less stringent, with M-dust less than or similar to 10(-1)M(circle dot) for the same assumptions.

  • 44.
    Johansson, Joel
    et al.
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwal, M. M.
    Helou, G.
    Masci, F.
    Tinyanont, S.
    Jencson, J.
    Cao, Y.
    Fox, O. D.
    Kromer, Markus
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Banerjee, D. P. K.
    Joshi, V.
    Jerkstrand, A.
    Kankare, E.
    Prince, T. A.
    Spitzer observations of SN 2014J and properties of mid-IR emission in Type Ia supernovae2017In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 466, no 3, p. 3442-3449Article in journal (Refereed)
    Abstract [en]

    SN 2014J in M 82 is the closest Type Ia supernova (SN Ia) in decades. The proximity allows for detailed studies of supernova physics and provides insights into the circumstellar and interstellar environment. In this work, we analyse Spitzer mid-infrared (mid-IR) data of SN 2014J in the 3.6 and 4.5 mu m wavelength range, together with several other nearby and well-studied SNe Ia. We compile the first composite mid-IR light-curve templates from our sample of SNe Ia, spanning the range from before peak brightness well into the nebular phase. Our observations indicate that SNe Ia form a very homogeneous class of objects at these wavelengths. Using the low-reddening supernovae for comparison, we constrain possible thermal emission from circumstellar dust around the highly reddened SN 2014J. We also study SNe 2006X and 2007le, where the presence of matter in the circumstellar environment has been suggested. No significant mid-IR excess is detected, allowing us to place upper limits on the amount of pre-existing dust in the circumstellar environment. For SN 2014J, M-dust less than or similar to 10(-5) M-circle dot within r(dust) similar to 10(17) cm, which is insufficient to account for the observed extinction. Similar limits are obtained for SNe 2006X and 2007le.

  • 45. Jönsson, J.
    et al.
    Dahlén, T.
    Hook, I.
    Goobar, A.
    Stockholm University, Faculty of Science, Department of Physics.
    Mörtsell, E.
    Stockholm University, Faculty of Science, Department of Physics.
    Weighing dark matter haloes with gravitationally lensed supernovae2010In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 402, no 1, p. 526-536Article in journal (Refereed)
    Abstract [en]

    High-redshift Type Ia supernovae (SNe Ia) are likely to be gravitationally lensed by dark matter haloes of galaxies in the foreground. Since SNe Ia have very small dispersion after light-curve shape and colour corrections, their brightness can be used to measure properties of the dark matter haloes via gravitational magnification. We use observations of galaxies and SNe Ia within the Great Observatories Origins Deep Survey (GOODS) to measure the relation between galaxy luminosity and dark matter halo mass. The relation we investigate is a scaling law between velocity dispersion and galaxy luminosity in the B band: σ = σ*(L/L*)η, where L* = 1010h-2Lsolar. The best-fitting values to this relation are σ* = 136 kms-1 and η = 0.27. We find σ* <~ 190 kms-1 at the 95 per cent confidence level. This method provides an independent cross-check of measurements of dark matter halo properties from galaxy-galaxy lensing studies. Our results agree with the galaxy-galaxy lensing results, but have much larger uncertainties. The GOODS sample of SNe Ia is relatively small (we include 24 SNe) and the results therefore depend on individual SNe Ia. We have investigated a number of potential systematic effects. Light-curve fitting, which affects the inferred brightness of the SNe Ia, appears to be the most important one. Results obtained using different light-curve fitting procedures differ at the 68.3 per cent confidence level.

  • 46.
    Jönsson, Jakob
    et al.
    Stockholm University, Faculty of Science, Department of Physics.
    Dahlén, Tomas
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics.
    Gunnarsson, Christofer
    Stockholm University, Faculty of Science, Department of Physics.
    Mörtsell, Edvard
    Stockholm University, Faculty of Science, Department of Physics.
    Lensing magnification of supernovae in the GOODS-fields2006In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 639, no 2, p. 991-998Article in journal (Refereed)
    Abstract [en]

    Gravitational lensing of high-redshift supernovae is potentially an important source of uncertainty when cosmological parameters are being derived from the measured brightness of Type Ia supernovae, especially in deep surveys with scarce statistics. Photometric and spectroscopic measurements of foreground galaxies along the lines of sight of 33 supernovae discovered with the Hubble Space Telescope, both core-collapse and Type Ia, are used to model the magnification probability distributions of the sources. Modelling galaxy halos with SIS or NFW profiles and using M/L scaling laws provided by the Faber-Jackson and Tully-Fisher relations, we find clear evidence for supernovae with lensing (de)magnification. However, the magnification distribution of the Type Ia supernovae used to determine cosmological distances matches very well the expectations for an unbiased sample; i.e., their mean magnification factor is consistent with unity. Our results show that the lensing distortions of the supernova brightness can be well understood for the GOODS sample and that correcting for this effect has a negligible impact on the derived cosmological parameters.

  • 47. Kasliwal, M. M.
    et al.
    Nakar, E.
    Singer, L. P.
    Kaplan, D. L.
    Cook, D. O.
    Van Sistine, A.
    Lau, R. M.
    Fremling, C.
    Gottlieb, O.
    Jencson, J. E.
    Adams, S. M.
    Feindt, Ulrich
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hotokezaka, K.
    Ghosh, S.
    Perley, D. A.
    Yu, P-C.
    Piran, T.
    Allison, J. R.
    Anupama, G. C.
    Balasubramanian, A.
    Bannister, K. W.
    Bally, J.
    Barnes, J.
    Barway, S.
    Bellm, E.
    Bhalerao, V.
    Bhattacharya, D.
    Blagorodnova, N.
    Bloom, J. S.
    Brady, P. R.
    Cannella, C.
    Chatterjee, D.
    Cenko, S. B.
    Cobb, B. E.
    Copperwheat, C.
    Corsi, A.
    De, K.
    Dobie, D.
    Emery, S. W. K.
    Evans, P. A.
    Fox, O. D.
    Frail, D. A.
    Frohmaier, C.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Hallinan, G.
    Harrison, F.
    Helou, G.
    Hinderer, T.
    Ho, A. Y. Q.
    Horesh, A.
    Ip, W-H.
    Itoh, R.
    Kasen, D.
    Kim, H.
    Kuin, N. P. M.
    Kupfer, T.
    Lynch, C.
    Madsen, K.
    Mazzali, P. A.
    Miller, A. A.
    Mooley, K.
    Murphy, T.
    Ngeow, C-C.
    Nichols, D.
    Nissanke, S.
    Nugent, P.
    Ofek, E. O.
    Qi, H.
    Quimby, R. M.
    Rosswog, Stephan
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Rusu, F.
    Sadler, E. M.
    Schmidt, P.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Steele, I.
    Williamson, A. R.
    Xu, Y.
    Yan, L.
    Yatsu, Y.
    Zhang, C.
    Zhao, W.
    Illuminating gravitational waves: A concordant picture of photons from a neutron star merger2017In: Science, ISSN 0036-8075, E-ISSN 1095-9203, Vol. 358, no 6370, p. 1559-+Article in journal (Refereed)
    Abstract [en]

    Merging neutron stars offer an excellent laboratory for simultaneously studying strong-field gravity and matter in extreme environments. We establish the physical association of an electromagnetic counterpart (EM170817) with gravitational waves (GW170817) detected from merging neutron stars. By synthesizing a panchromatic data set, we demonstrate that merging neutron stars are a long-sought production site forging heavy elements by r-process nucleosynthesis. The weak gamma rays seen in EM170817 are dissimilar to classical short gamma-ray bursts with ultrarelativistic jets. Instead, we suggest that breakout of a wide-angle, mildly relativistic cocoon engulfing the jet explains the low-luminosity gamma rays, the high-luminosity ultraviolet-optical-infrared, and the delayed radio and x-ray emission. We posit that all neutron star mergers may lead to a wide-angle cocoon breakout, sometimes accompanied by a successful jet and sometimes by a choked jet.

  • 48. Kessler, Richard
    et al.
    Cinabro, David
    Bassett, Bruce
    Dilday, Benjamin
    Frieman, Joshua A.
    Garnavich, Peter M.
    Jha, Saurabh
    Marriner, John
    Nichol, Robert C.
    Sako, Masao
    Smith, Mathew
    Bernstein, Joseph P.
    Bizyaev, Dmitry
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kuhlmann, Stephen
    Schneider, Donald P.
    Stritzinger, Maximilian
    Photometric Estimates of Redshifts and Distance Moduli for Type Ia Supernovae2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 717, no 1, p. 40-57Article in journal (Refereed)
    Abstract [en]

    Large planned photometric surveys will discover hundreds of thousands of supernovae (SNe), outstripping the resources available for spectroscopic follow-up and necessitating the development of purely photometric methods to exploit these events for cosmological study. We present a light curve fitting technique for type Ia supernova (SN Ia) photometric redshift (photo-z) estimation in which the redshift is determined simultaneously with the other fit parameters. We implement this "LCFIT+Z" technique within the frameworks of the MLCS2K2 and SALTII light curve fit methods and determine the precision on the redshift and distance modulus. This method is applied to a spectroscopically confirmed sample of 296 SNe Ia from the Sloan Digital Sky Survey-II (SDSS-II) SN Survey and 37 publicly available SNe Ia from the Supernova Legacy Survey (SNLS). We have also applied the method to a large suite of realistic simulated light curves for existing and planned surveys, including the SDSS, SNLS, and the Large Synoptic Survey Telescope. When intrinsic SN color fluctuations are included, the photo-z precision for the simulation is consistent with that in the data. Finally, we compare the LCFIT+Z photo-z precision with previous results using color-based SN photo-z estimates.

  • 49.
    Kromer, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Pakmor, R.
    Taubenberger, S.
    Amanullah, Rahman
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Cenko, S. B.
    Fransson, Claes
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Leloudas, G.
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Roepke, F. K.
    Seitenzahl, I. R.
    Sim, S. A.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    The peculiar Type Ia supernova iPTF14atg: Chandrasekhar-mass explosion or violent merger?2016In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 459, no 4, p. 4428-4439Article in journal (Refereed)
    Abstract [en]

    iPTF14atg, a subluminous peculiar Type Ia supernova (SN Ia) similar to SN 2002es, is the first SN Ia for which a strong UV flash was observed in the early-time light curves. This has been interpreted as evidence for a single-degenerate (SD) progenitor system, where such a signal is expected from interactions between the SN ejecta and the non-degenerate companion star. Here, we compare synthetic observables of multidimensional state-of-the-art explosion models for different progenitor scenarios to the light curves and spectra of iPTF14atg. From our models, we have difficulties explaining the spectral evolution of iPTF14atg within the SD progenitor channel. In contrast, we find that a violent merger of two carbon-oxygen white dwarfs with 0.9 and 0.76 M-aS (TM), respectively, provides an excellent match to the spectral evolution of iPTF14atg from 10 d before to several weeks after maximum light. Our merger model does not naturally explain the initial UV flash of iPTF14atg. We discuss several possibilities like interactions of the SN ejecta with the circumstellar medium and surface radioactivity from an He-ignited merger that may be able to account for the early UV emission in violent merger models.

  • 50. Lampeitl, Hubert
    et al.
    Smith, Mathew
    Nichol, Robert C.
    Bassett, Bruce
    Cinabro, David
    Dilday, Benjamin
    Foley, Ryan J.
    Frieman, Joshua A.
    Garnavich, Peter M.
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Im, Myungshin
    Jha, Saurabh W.
    Marriner, John
    Miquel, Ramon
    Nordin, Jakob
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Östman, Linda
    Riess, Adam G.
    Sako, Masao
    Schneider, Donald P.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stritzinger, Maximilian
    The Effect of Host Galaxies on Type Ia Supernovae in the SDSS-II Supernova Survey2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 722, p. 566-576Article in journal (Refereed)
    Abstract [en]

    We present an analysis of the host galaxy dependences of Type Ia Supernovae (SNe Ia) from the full three year sample of the SDSS-II Supernova Survey. We re-discover, to high significance, the strong correlation between host galaxy type and the width of the observed SN light curve, i.e., fainter, quickly declining SNe Ia favor passive host galaxies, while brighter, slowly declining Ia's favor star-forming galaxies. We also find evidence (at between 2σ and 3σ) that SNe Ia are sime0.1 ± 0.04 mag brighter in passive host galaxies than in star-forming hosts, after the SN Ia light curves have been standardized using the light-curve shape and color variations. This difference in brightness is present in both the SALT2 and MCLS2k2 light-curve fitting methodologies. We see evidence for differences in the SN Ia color relationship between passive and star-forming host galaxies, e.g., for the MLCS2k2 technique, we see that SNe Ia in passive hosts favor a dust law of RV = 1.0 ± 0.2, while SNe Ia in star-forming hosts require RV = 1.8+0.2 -0.4. The significance of these trends depends on the range of SN colors considered. We demonstrate that these effects can be parameterized using the stellar mass of the host galaxy (with a confidence of >4σ) and including this extra parameter provides a better statistical fit to our data. Our results suggest that future cosmological analyses of SN Ia samples should include host galaxy information.

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