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  • 1.
    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.

  • 2. Bellm, Eric C.
    et al.
    Kulkarni, Shrinivas R.
    Graham, Matthew J.
    Dekany, Richard
    Smith, Roger M.
    Riddle, Reed
    Masci, Frank J.
    Helou, George
    Prince, Thomas A.
    Adams, Scott M.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Barlow, Tom
    Bauer, James
    Beck, Ron
    Belicki, Justin
    Biswas, Rahul
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Blagorodnova, Nadejda
    Bodewits, Dennis
    Bolin, Bryce
    Brinnel, Valery
    Brooke, Tim
    Bue, Brian
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Burruss, Rick
    Cenko, S. Bradley
    Chang, Chan-Kao
    Connolly, Andrew
    Coughlin, Michael
    Cromer, John
    Cunningham, Virginia
    De, Kishalay
    Delacroix, Alex
    Desai, Vandana
    Duev, Dmitry A.
    Eadie, Gwendolyn
    Farnham, Tony L.
    Feeney, Michael
    Feindt, Ulrich
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Flynn, David
    Franckowiak, Anna
    Frederick, S.
    Fremling, C.
    Gal-Yam, Avishay
    Gezari, Suvi
    Giomi, Matteo
    Goldstein, Daniel A.
    Golkhou, V. Zach
    Goobar, Ariel
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Groom, Steven
    Hacopians, Eugean
    Hale, David
    Henning, John
    Ho, Anna Y. Q.
    Hover, David
    Howell, Justin
    Hung, Tiara
    Huppenkothen, Daniela
    Imel, David
    Ip, Wing-Huen
    Ivezic, Zeljko
    Jackson, Edward
    Jones, Lynne
    Juric, Mario
    Kasliwal, Mansi M.
    Kaspi, S.
    Kaye, Stephen
    Kelley, Michael S. P.
    Kowalski, Marek
    Kramer, Emily
    Kupfer, Thomas
    Landry, Walter
    Laher, Russ R.
    Lee, Chien-De
    Lin, Hsing Wen
    Lin, Zhong-Yi
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Giomi, Matteo
    Mahabal, Ashish
    Mao, Peter
    Miller, Adam A.
    Monkewitz, Serge
    Murphy, Patrick
    Ngeow, Chow-Choong
    Nordin, Jakob
    Nugent, Peter
    Ofek, Eran
    Patterson, Maria T.
    Penprase, Bryan
    Porter, Michael
    Rauch, Ludwig
    Rebbapragada, Umaa
    Reiley, Dan
    Rigault, Mickael
    Rodriguez, Hector
    van Roestel, Jan
    Rusholme, Ben
    van Santen, Jakob
    Schulze, S.
    Shupe, David L.
    Singer, Leo P.
    Soumagnac, Maayane T.
    Stein, Robert
    Surace, Jason
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Szkody, Paula
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Terek, Scott
    Van Sistine, Angela
    van Velzen, Sjoert
    Vestrand, W. Thomas
    Walters, Richard
    Ward, Charlotte
    Ye, Quan-Zhi
    Yu, Po-Chieh
    Yan, Lin
    Zolkower, Jeffry
    The Zwicky Transient Facility: System Overview, Performance, and First Results2019In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 131, no 995, article id 018002Article in journal (Refereed)
    Abstract [en]

    The Zwicky Transient Facility (ZTF) is a new optical time-domain survey that uses the Palomar 48 inch Schmidt telescope. A custom-built wide-field camera provides a 47 deg(2) field of view and 8 s readout time, yielding more than an order of magnitude improvement in survey speed relative to its predecessor survey, the Palomar Transient Factory. We describe the design and implementation of the camera and observing system. The ZTF data system at the Infrared Processing and Analysis Center provides near-real-time reduction to identify moving and varying objects. We outline the analysis pipelines, data products, and associated archive. Finally, we present on-sky performance analysis and first scientific results from commissioning and the early survey. ZTF's public alert stream will serve as a useful precursor for that of the Large Synoptic Survey Telescope.

  • 3. Fremling, C.
    et al.
    Ko, H.
    Dugas, A.
    Ergon, Mattias
    Stockholm University, Faculty of Science, Department of Astronomy. 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).
    Bagdasaryan, A.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Belicki, J.
    Bellm, E.
    Blagorodnova, N.
    De, K.
    Dekany, R.
    Frederick, S.
    Gal-Yam, A.
    Goldstein, D. A.
    Golkhou, V. Z.
    Graham, M.
    Kasliwal, M.
    Kowalski, M.
    Kulkarni, S. R.
    Kupfer, T.
    Laher, R. R.
    Masci, F. J.
    Miller, A. A.
    Neill, J. D.
    Perley, D. A.
    Rebbapragada, U. D.
    Riddle, R.
    Rusholme, B.
    Schulze, S.
    Smith, R. M.
    Tartaglia, Leonardo
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Yan, Lin
    Yao, Y.
    ZTF18aalrxas: A Type IIb Supernova from a Very Extended Low-mass Progenitor2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 878, no 1, article id L5Article in journal (Refereed)
    Abstract [en]

    We investigate ZTF18aalrxas, a double-peaked Type IIb core-collapse supernova (SN) discovered during science validation of the Zwicky Transient Facility. ZTF18aalrxas was discovered while the optical emission was still rising toward the initial cooling peak (0.7 mag over 2 days). Our observations consist of multi-band (ultraviolet and optical) light curves (LCs), and optical spectra spanning from approximate to 0.7 to approximate to 480 days past the explosion. We use a Monte-Carlo based non-local thermodynamic equilibrium model that simultaneously reproduces both the Ni-56-powered bolometric LC and our nebular spectrum. This model is used to constrain the synthesized radioactive nickel mass (0.17 M-circle dot) and the total ejecta mass (1.7 M-circle dot) of the SN. The cooling emission is modeled using semi-analytical extended envelope models to constrain the progenitor radius (790-1050 R-circle dot) at the time of explosion. Our nebular spectrum shows signs of interaction with a dense circumstellar medium (CSM), and this spectrum is modeled and analyzed to constrain the amount of ejected oxygen (0.3-0.5 M-circle dot) and the total hydrogen mass (approximate to 0.15 M-circle dot) in the envelope of the progenitor. The oxygen mass of ZTF18aalrxas is consistent with a low (12-13 M-circle dot) zero-age main-sequence mass progenitor. The LCs and spectra of ZTF18aalrxas are not consistent with massive single-star SN Type IIb progenitor models. The presence of an extended hydrogen envelope of low mass, the presence of a dense CSM, the derived ejecta mass, and the late-time oxygen emission can all be explained in a binary model scenario.

  • 4.
    Fremling, Christoffer
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kasliwal, M. M.
    Kulkarni, S. R.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ergon, Mattias
    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).
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Arcavi, I
    Cenko, S. B.
    Clubb, K.
    De Cia, A.
    Duggan, G.
    Filippenko, A.
    Gal-Yam, A.
    Graham, M. L.
    Horesh, A.
    Hosseinzadeh, G.
    Howell, D. A.
    Kuesters, D.
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Matheson, T.
    Nugent, P. E.
    Perley, D. A.
    Quimby, R. M.
    Saunders, C.
    Oxygen and helium in stripped-envelope supernovae2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 618, article id A37Article in journal (Refereed)
    Abstract [en]

    We present an analysis of 507 spectra of 173 stripped-envelope (SE) supernovae (SNe) discovered by the untargeted Palomar Transient Factory (PTF) and intermediate PTF (iPTF) surveys. Our sample contains 55 Type IIb SNe (SNe 45 Type Ib SNe (SNe IIb), 56 Type Ic SNe (SNe Ic), and 17 Type Ib/c SNe (SNe Ib/c). We have compared the SE SN subtypes via measurements of the pseudo-equivalent widths (pEWs) and velocities of the He I lambda lambda 5876, 7065 and O I lambda 7774 absorption lines. Consistent with previous work, we find that SNe Ic show higher pEWs and velocities in O I lambda 7774 compared to SNe IIb and Ib. The pEWs of the He I lambda lambda 5876, 7065 lines are similar in SNe Ib and IIb after maximum light. The He I lambda lambda 5876, 7065 velocities at maximum light are higher in SNe Ib compared to SNe IIb. We identify an anticorrelation between the He I lambda 7065 pEW and O I lambda 7774 velocity among SNe IIb and Ib. This can be interpreted as a continuum in the amount of He present at the time of explosion. It has been suggested that SNe Ib and Ic have similar amounts of He, and that lower mixing could be responsible for hiding He in SNe Ic. However, our data contradict this mixing hypothesis. The observed difference in the expansion rate of the ejecta around maximum light of SNe Ic (V-m root 2E(k)/M-ej approximate to 15 000 km s(-1)) and SNe Ib (V-m approximate to 9000 km s(-1)) would imply an average He mass difference of similar to 1.4 M-circle dot, if the other explosion parameters are assumed to be unchanged between the SE SN subtypes. We conclude that SNe Ic do not hide He but lose He due to envelope stripping.

  • 5. Graham, Matthew J.
    et al.
    Barbarino, Cristina
    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).
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. 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).
    Biswas, Rahul
    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).
    Zolkower, Jeffry
    The Zwicky Transient Facility: Science Objectives2019In: Publications of the Astronomical Society of the Pacific, ISSN 0004-6280, E-ISSN 1538-3873, Vol. 131, no 1001, article id 078001Article in journal (Refereed)
    Abstract [en]

    The Zwicky Transient Facility (ZTF), a public-private enterprise, is a new time-domain survey employing a dedicated camera on the Palomar 48-inch Schmidt telescope with a 47 deg(2) field of view and an 8 second readout time. It is well positioned in the development of time-domain astronomy, offering operations at 10% of the scale and style of the Large Synoptic Survey Telescope (LSST) with a single 1-m class survey telescope. The public surveys will cover the observable northern sky every three nights in g and r filters and the visible Galactic plane every night in g and r. Alerts generated by these surveys are sent in real time to brokers. A consortium of universities that provided funding (partnership) are undertaking several boutique surveys. The combination of these surveys producing one million alerts per night allows for exploration of transient and variable astrophysical phenomena brighter than r similar to 20.5 on timescales of minutes to years. We describe the primary science objectives driving ZTF, including the physics of supernovae and relativistic explosions, multi-messenger astrophysics, supernova cosmology, active galactic nuclei, and tidal disruption events, stellar variability, and solar system objects.

  • 6. Ho, Anna Y. Q.
    et al.
    Goldstein, Daniel A.
    Schulze, Steve
    Khatami, David K.
    Perley, Daniel A.
    Ergon, Mattias
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gal-Yam, Avishay
    Corsi, Alessandra
    Andreoni, Igor
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bellm, Eric C.
    Blagorodnova, Nadia
    Bright, Joe S.
    Burns, E.
    Cenko, S. Bradley
    Cunningham, Virginia
    De, Kishalay
    Dekany, Richard
    Dugas, Alison
    Fender, Rob P.
    Fransson, Claes
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fremling, Christoffer
    Goldstein, Adam
    Graham, Matthew J.
    Hale, David
    Horesh, Assaf
    Hung, Tiara
    Kasliwal, Mansi M.
    Kuin, N. Paul M.
    Kulkarni, S. R.
    Kupfer, Thomas
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Masci, Frank J.
    Ngeow, Chow-Choong
    Nugent, Peter E.
    Ofek, Eran O.
    Patterson, Maria T.
    Petitpas, Glen
    Rusholme, Ben
    Sai, Hanna
    Sfaradi, Itai
    Shupe, David L.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Soumagnac, Maayane T.
    Tachibana, Yutaro
    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, Richard
    Wang, Xiaofeng
    Yao, Yuhan
    Zhang, Xinhan
    Evidence for Late-stage Eruptive Mass Loss in the Progenitor to SN2018gep, a Broad-lined Ic Supernova: Pre-explosion Emission and a Rapidly Rising Luminous Transient2019In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 887, no 2, article id 169Article in journal (Refereed)
    Abstract [en]

    We present detailed observations of ZTF18abukavn (SN2018gep), discovered in high-cadence data from the Zwicky Transient Facility as a rapidly rising (1.4 +/- 0.1 mag hr(-1)) and luminous (M-g,M- peak = -20 mag) transient. It is spectroscopically classified as a broad-lined stripped-envelope supernova (Ic-BL SN). The high peak luminosity (L-bol greater than or similar to 3 x 10(44) erg s(-1)), the short rise time (t(rise) = 3 days in g band), and the blue colors at peak (g-r similar to -0.4) all resemble the high-redshift Ic-BL iPTF16asu, as well as several other unclassified fast transients. The early discovery of SN2018gep (within an hour of shock breakout) enabled an intensive spectroscopic campaign, including the highest-temperature (T-eff greater than or similar to 40,000 K) spectra of a stripped-envelope SN. A retrospective search revealed luminous (M-g similar to M-r approximate to -14 mag) emission in the days to weeks before explosion, the first definitive detection of precursor emission for a Ic-BL. We find a limit on the isotropic gamma-ray energy release E-gamma,E- iso < 4.9 x 10(48) erg, a limit on X-ray emission L-X < 10(40) erg s(-1), and a limit on radio emission nu L-v less than or similar to 10(37) erg s(-1). Taken together, we find that the early (< 10 days) data are best explained by shock breakout in a massive shell of dense circumstellar material (0.02 M-circle dot) at large radii (3 x 10(14) cm) that was ejected in eruptive pre-explosion mass-loss episodes. The late-time (> 10 days) light curve requires an additional energy source, which could be the radioactive decay of Ni-56.

  • 7. Jencson, Jacob E.
    et al.
    Adams, Scott M.
    Bond, Howard E.
    van Dyk, Schuyler D.
    Kasliwal, Mansi M.
    Bally, John
    Blagorodnova, Nadejda
    De, Kishalay
    Fremling, Christoffer
    Yao, Yuhan
    Fruchter, Andrew
    Rubin, David
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. 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).
    Miller, Adam A.
    Hicks, Erin K. S.
    Malkan, Matthew A.
    Andreoni, Igor
    Bellm, Eric C.
    Buchheim, Robert
    Dekany, Richard
    Feeney, Michael
    Frederick, Sara
    Gal-Yam, Avishay
    Gehrz, Robert D.
    Giomi, Matteo
    Graham, Matthew J.
    Green, Wayne
    Hale, David
    Hankins, Matthew J.
    Hanson, Mark
    Helou, George
    Ho, Anna Y. Q.
    Hung, T.
    Juric, Mario
    Kendurkar, Malhar R.
    Kulkarni, S. R.
    Lau, Ryan M.
    Masci, Frank J.
    Neill, James D.
    Quin, Kevin
    Riddle, Reed L.
    Rusholme, Ben
    Sims, Forrest
    Smith, Nathan
    Smith, Roger M.
    Soumagnac, Maayane T.
    Tachibana, Yutaro
    Tinyanont, Samaporn
    Walters, Richard
    Watson, Stanley
    Williams, Robert E.
    Discovery of an Intermediate-luminosity Red Transient in M51 and Its Likely Dust-obscured, Infrared-variable Progenitor2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 880, no 2, article id L20Article in journal (Refereed)
    Abstract [en]

    We present the discovery of an optical transient (OT) in Messier. 51, designated M51 OT2019-1 (also ZTF 19aadyppr, AT 2019abn, ATLAS19bz1), by the Zwicky Transient Facility (ZTF). The OT rose over 15. days to an observed luminosity of M-r = -13 (nu L-nu = 9 x 10(6) L-circle dot), in the luminosity gap between novae and typical supernovae (SNe). Spectra during the outburst show a red continuum, Balmer emission with a velocity width of approximate to 400 km s(-1), Ca II and [Ca II] emission, and absorption features characteristic of an F-type supergiant. The spectra and multiband light curves are similar to the so-called SN impostors and intermediate-luminosity red transients (ILRTs). We directly identify the likely progenitor in archival Spitzer Space Telescope imaging with a 4.5 mu m luminosity of M-[4.5] approximate to -12.2 mag and a [3.6]-[4.5] color redder than 0.74 mag, similar to those of the prototype ILRTs SN 2008S and NGC 300 OT2008-1. Intensive monitoring of M51 with Spitzer further reveals evidence for variability of the progenitor candidate at [ 4.5] in the years before the OT. The progenitor is not detected in pre-outburst Hubble Space Telescope optical and near-IR images. The optical colors during outburst combined with spectroscopic temperature constraints imply a higher reddening of E(B - V) approximate to 0.7 mag and higher intrinsic luminosity of M-r approximate to -14.9 mag (nu L-nu = 5.3 x 10(7) L-circle dot) near peak than seen in previous ILRT candidates. Moreover, the extinction estimate is higher on the rise than on the plateau, suggestive of an extended phase of circumstellar dust destruction. These results, enabled by the early discovery of M51. OT2019-1 and extensive pre-outburst archival coverage, offer new clues about the debated origins of ILRTs and may challenge the hypothesis that they arise from the electron-capture induced collapse of extreme asymptotic giant branch stars.

  • 8. McBrien, Owen R.
    et al.
    Smartt, Stephen J.
    Chen, Ting-Wan
    Inserra, Cosimo
    Gillanders, James H.
    Sim, Stuart A.
    Jerkstrand, Anders
    Rest, Armin
    Valenti, Stefano
    Roy, Rupak
    Gromadzki, Mariusz
    Taubenberger, Stefan
    Flörs, Andreas
    Huber, Mark E.
    Chambers, Ken C.
    Gal-Yam, Avishay
    Young, David R.
    Nicholl, Matt
    Kankare, Erkki
    Smith, Ken W.
    Maguire, Kate
    Mandel, Ilya
    Prentice, Simon
    Rodríguez, Ósmar
    Pineda Garcia, Jonathan
    Gutiérrez, Claudia P.
    Galbany, Lluís
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Clark, Peter S. J.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kulkarni, Shrinivas R.
    De, Kishalay
    Buckley, David A. H.
    Rau, Arne
    SN2018kzr: A Rapidly Declining Transient from the Destruction of a White Dwarf2019In: Astrophysical Journal Letters, ISSN 2041-8205, E-ISSN 2041-8213, Vol. 885, no 1, article id L23Article in journal (Refereed)
    Abstract [en]

    We present SN2018kzr, the fastest declining supernova-like transient, second only to the kilonova, AT2017gfo. SN2018kzr is characterized by a peak magnitude of M-r & xfffd;=& xfffd;?17.98, a peak bolometric luminosity of ?1.4 & xfffd;& x5e0;10(43) erg s(?1), and a rapid decline rate of 0.48 & xfffd;& xfffd;0.03 mag day(?1) in the r band. The bolometric luminosity evolves too quickly to be explained by pure Ni-56 heating, necessitating the inclusion of an alternative powering source. Incorporating the spin-down of a magnetized neutron star adequately describes the lightcurve and we estimate a small ejecta mass of M-ej & xfffd;=& xfffd;0.10 & xfffd;& xfffd;0.05 M. Our spectral modeling suggests the ejecta is composed of intermediate mass elements including O, Si, and Mg and trace amounts of Fe-peak elements, which disfavors a binary neutron star merger. We discuss three explosion scenarios for SN2018kzr, given the low ejecta mass, intermediate mass element composition, and high likelihood of additional powering?the core collapse of an ultra-stripped progenitor, the accretion induced collapse (AIC) of a white dwarf, and the merger of a white dwarf and neutron star. The requirement for an alternative input energy source favors either the AIC with magnetar powering or a white dwarf?neutron star merger with energy from disk wind shocks.

  • 9. Melandri, A.
    et al.
    Malesani, D. B.
    Izzo, L.
    Japelj, J.
    Vergani, S. D.
    Schady, P.
    Sagues Carracedo, A.
    de Ugarte Postigo, A.
    Anderson, J. P.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bolmer, J.
    Breeveld, A.
    Calissendorff, Per
    Stockholm University, Faculty of Science, Department of Astronomy.
    Campana, S.
    Cano, Z.
    Carini, R.
    Covino, S.
    D'Avanzo, P.
    D'Elia, V.
    della Valle, M.
    De Pasquale, M.
    Fynbo, J. P. U.
    Gromadzki, M.
    Hammer, F.
    Hartmann, D. H.
    Heintz, K. E.
    Inserra, C.
    Jakobsson, P.
    Kann, D. A.
    Kotilainen, J.
    Maguire, K.
    Masetti, N.
    Nicholl, M.
    Olivares E, F.
    Pugliese, G.
    Rossi, A.
    Salvaterra, R.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stone, M. B.
    Tagliaferri, G.
    Tomasella, L.
    Thone, C. C.
    Xu, D.
    Young, D. R.
    GRB171010A/SN 2017htp: a GRB-SN at z=0.332019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 490, no 4, p. 5366-5374Article in journal (Refereed)
    Abstract [en]

    The number of supernovae known to be connected with long-duration gamma-ray bursts (GRBs) is increasing and the link between these events is no longer exclusively found at low redshift (z less than or similar to 0.3) but is well established also at larger distances. We present a new case of such a liaison at z = 0.33 between GRB171010A and SN 2017htp. It is the second closest GRB with an associated supernova of only three events detected by Fermi-LAT. The supernova is one of the few higher redshift cases where spectroscopic observations were possible and shows spectral similarities with the well-studied SN 1998bw, having produced a similar Ni mass (M-Ni = 0.33 +/- 0.02 M-circle dot) with slightly lower ejected mass (M-ej = 4.1 +/- 0.7 M-circle dot) and kinetic energy (E-K = 8.1 +/- 2.5 x 10(51) erg). The host-galaxy is bigger in size than typical GRB host galaxies, but the analysis of the region hosting the GRB revealed spectral properties typically observed in GRB hosts and showed that the progenitor of this event was located in a very bright H II region of its face-on host galaxy, at a projected distance of similar to 10 kpc from its galactic centre. The star-formation rate (SFRGRB similar to 0.2 M-circle dot yr(-1)) and metallicity (12 + log(O/H) similar to 8.15 +/- 0.10) of the GRB star-forming region are consistent with those of the host galaxies of previously studied GRB-SN systems.

  • 10. Prentice, S. J.
    et al.
    Ashall, C.
    James, P. A.
    Short, L.
    Mazzali, P. A.
    Bersier, D.
    Crowther, P. A.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Chen, T. -W.
    Copperwheat, C. M.
    Darnley, M. J.
    Denneau, L.
    Elias-Rosa, N.
    Fraser, M.
    Galbany, L.
    Gal-Yam, A.
    Harmanen, J.
    Howell, D. A.
    Hosseinzadeh, G.
    Inserra, C.
    Kankare, E.
    Karamehmetoglu, Emir
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Lamb, G. P.
    Limongi, M.
    Maguire, K.
    McCully, C.
    Olivares E., F.
    Piascik, A. S.
    Pignata, G.
    Reichart, D. E.
    Rest, A.
    Reynolds, T.
    Rodríguez, Ó.
    Saario, J. L. O.
    Schulze, S.
    Smartt, S. J.
    Smith, K. W.
    Sollerman, Jesper
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Stalder, B.
    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).
    Valenti, S.
    Vergani, S. D.
    Williams, S. C.
    Young, D. R.
    Investigating the properties of stripped-envelope supernovae; what are the implications for their progenitors?2019In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 485, no 2, p. 1559-1578Article in journal (Refereed)
    Abstract [en]

    We present observations and analysis of 18 stripped-envelope supernovae observed during 2013-2018. This sample consists of five H/He-rich SNe, sixH-poor/He-rich SNe, three narrow lined SNe Ic, and four broad lined SNe Ic. The peak luminosity and characteristic time-scales of the bolometric light curves are calculated, and the light curves modelled to derive Ni-56 and ejecta masses (M-Ni and M-cj). Additionally, the temperature evolution and spectral line velocity curves of each SN are examined. Analysis of the [O I] line in the nebular phase of eight SNe suggests their progenitors had initial masses < 20 M-circle dot. The bolometric light curve properties are examined in combination with those of other SE events from the literature. The resulting data set gives the M-ej distribution for 80 SE-SNe, the largest such sample in the literature to date, and shows that SNe Ib have the lowest median M-ej, followed by narrow-lined SNe Ic, H/He-rich SNe, broad-lined SNe Ic, and finally gamma-ray burst SNe. SNe Ic-6/7 show the largest spread of M-ej ranging from similar to 1.2-11 M-circle dot, considerably greater than any other subtype. For all SE-SNe <M-ej> = 2.8 +/- 1.5 M-circle dot which further strengthens the evidence that SE-SNe arise from low-mass progenitors which are typically <5 M-circle dot at the time of explosion, again suggesting M-ZAMS < 25 M-circle dot. The low <M-ej> and lack of clear bimodality in the distribution implies < 30 M-circle dot progenitors and that envelope stripping via binary interaction is the dominant evolutionary pathway of these SNe.

  • 11. Smartt, S. J.
    et al.
    Chen, T. -W.
    Jerkstrand, A.
    Coughlin, M.
    Kankare, E.
    Sim, S. A.
    Fraser, M.
    Inserra, C.
    Maguire, K.
    Chambers, K. C.
    Huber, M. E.
    Kruhler, T.
    Leloudas, G.
    Magee, M.
    Shingles, L. J.
    Smith, K. W.
    Young, D. R.
    Tonry, J.
    Kotak, R.
    Gal-Yam, A.
    Lyman, J. D.
    Homan, D. S.
    Agliozzo, C.
    Anderson, J. P.
    Angus, C. R.
    Ashall, C.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Bauer, F. E.
    Berton, M.
    Botticella, M. T.
    Bulla, Mattia
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). Inter-University Centre for Astronomy and Astrophysics (IUCAA), India.
    Bulger, J.
    Cannizzaro, G.
    Cano, Z.
    Cartier, R.
    Cikota, A.
    Clark, P.
    De Cia, A.
    Della Valle, M.
    Denneau, L.
    Dennefeld, M.
    Dessart, L.
    Dimitriadis, G.
    Elias-Rosa, N.
    Firth, R. E.
    Flewelling, H.
    Floers, A.
    Franckowiak, A.
    Frohmaier, C.
    Galbany, L.
    Gonzalez-Gaitan, S.
    Greiner, J.
    Gromadzki, M.
    Guelbenzu, A. Nicuesa
    Gutierrez, C. P.
    Hamanowicz, A.
    Hanlon, L.
    Harmanen, J.
    Heintz, K. E.
    Heinze, A.
    Hernandez, M. -S.
    Hodgkin, S. T.
    Hook, I. M.
    Izzo, L.
    James, P. A.
    Jonker, P. G.
    Kerzendorf, W. E.
    Klose, S.
    Kostrzewa-Rutkowska, Z.
    Kowalski, M.
    Kromer, M.
    Kuncarayakti, H.
    Lawrence, A.
    Lowe, T. B.
    Magnier, E. A.
    Manulis, I.
    Martin-Carrillo, A.
    Mattila, S.
    McBrien, O.
    Mueller, A.
    Nordin, J.
    O'Neill, D.
    Onori, F.
    Palmerio, J. T.
    Pastorello, A.
    Patat, F.
    Pignata, G.
    Podsiadlowski, Ph.
    Pumo, M. L.
    Prentice, S. J.
    Rau, A.
    Razza, A.
    Rest, A.
    Reynolds, T.
    Roy, Rupak
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ruiter, A. J.
    Rybicki, K. A.
    Salmon, L.
    Schady, P.
    Schultz, A. S. B.
    Schweyer, T.
    Seitenzahl, I. R.
    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).
    Stalder, B.
    Stubbs, C. W.
    Sullivan, M.
    Szegedi, H.
    Taddia, Francesco
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Taubenberger, S.
    Terreran, G.
    van Soelen, B.
    Vos, J.
    Wainscoat, R. J.
    Walton, N. A.
    Waters, C.
    Weiland, H.
    Willman, M.
    Wiseman, P.
    Wright, D. E.
    Wyrzykowski, L.
    Yaron, O.
    A kilonova as the electromagnetic counterpart to a gravitational-wave source2017In: Nature, ISSN 0028-0836, E-ISSN 1476-4687, Vol. 551, no 7678, p. 75-+Article in journal (Refereed)
    Abstract [en]

    Gravitational waves were discovered with the detection of binary black-hole mergers(1) and they should also be detectable from lower-mass neutron-star mergers. These are predicted to eject material rich in heavy radioactive isotopes that can power an electromagnetic signal. This signal is luminous at optical and infrared wavelengths and is called a kilonova(2-5). The gravitational-wave source GW170817 arose from a binary neutron-star merger in the nearby Universe with a relatively well confined sky position and distance estimate(6). Here we report observations and physical modelling of a rapidly fading electromagnetic transient in the galaxy NGC 4993, which is spatially coincident with GW170817 and with a weak, short.-ray burst(7,8). The transient has physical parameters that broadly match the theoretical predictions of blue kilonovae from neutron-star mergers. The emitted electromagnetic radiation can be explained with an ejected mass of 0.04 +/- 0.01 solar masses, with an opacity of less than 0.5 square centimetres per gram, at a velocity of 0.2 +/- 0.1 times light speed. The power source is constrained to have a power-law slope of -1.2 +/- 0.3, consistent with radioactive powering from r-process nuclides. (The r-process is a series of neutron capture reactions that synthesise many of the elements heavier than iron.) We identify line features in the spectra that are consistent with light r-process elements (atomic masses of 90-140). As it fades, the transient rapidly becomes red, and a higher-opacity, lanthanide-rich ejecta component may contribute to the emission. This indicates that neutron-star mergers produce gravitational waves and radioactively powered kilonovae, and are a nucleosynthetic source of the r-process elements.

  • 12.
    Sollerman, Jesper
    et al.
    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).
    Arcavi, I.
    Fremling, Christoffer
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Fransson, Claes
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Burke, J.
    Cenko, S. B.
    Andersen, O.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Andreoni, I.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Blagorodova, N.
    Brink, T. G.
    Filippenko, A. V.
    Gal-Yam, A.
    Hiramatsu, D.
    Hosseinzadeh, G.
    Howell, D. A.
    de Jaeger, T.
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    McCully, C.
    Perley, D. A.
    Tartaglia, Leonardo
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Terreran, G.
    Valenti, S.
    Wang, X.
    Late-time observations of the extraordinary Type II supernova iPTF14hls2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 621, article id A30Article in journal (Refereed)
    Abstract [en]

    Aims. We study iPTF14hls, a luminous and extraordinary long-lived Type II supernova, which lately has attracted much attention and disparate interpretation.

    Methods. We have presented new optical photometry that extends the light curves up to more than three years past discovery. We also obtained optical spectroscopy over this period, and furthermore present additional space-based observations using Swift and HST.

    Results. After an almost constant luminosity for hundreds of days, the later light curve of iPTF14hls finally fades and then displays a dramatic drop after about 1000 d, but the supernova is still visible at the latest epochs presented. The spectra have finally turned nebular, and our very last optical spectrum likely displays signatures from the deep and dense interior of the explosion. A high-resolution HST image highlights the complex environment of the explosion in this low-luminosity galaxy.

    Conclusions. We provide a large number of additional late-time observations of iPTF14hls, which are (and will continue to be) used to assess the many different interpretations for this intriguing object. In particular, the very late (+1000 d) steep decline of the optical light curve is difficult to reconcile with the proposed central engine models. The lack of very strong X-ray emission, and the emergence of intermediate-width emission lines including [S II] that we propose originate from dense, processed material in the core of the supernova ejecta, are also key observational tests for both existing and future models.

  • 13.
    Taddia, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. 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).
    Fremling, C.
    Barbarino, Cristina
    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).
    Arcavi, I.
    Cenko, S. B.
    Filippenko, A.
    Gal-Yam, A.
    Hiramatsu, D.
    Hosseinzadeh, G.
    Howell, D. A.
    Kulkarni, S. R.
    Laher, R.
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC). California Institute of Technology, USA.
    Masci, F.
    Nugent, P. E.
    Nyholm, Anders
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Perley, D. A.
    Quimby, R.
    Silverman, J. M.
    Analysis of broad-lined Type Ic supernovae from the (intermediate) Palomar Transient Factory2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 621, article id A71Article in journal (Refereed)
    Abstract [en]

    We study 34 Type Ic supernovae that have broad spectral features (SNe Ic-BL). This is the only SN type found in association with long-duration gamma-ray bursts (GRBs). We obtained our photometric data with the Palomar Transient Factory (PTF) and its continuation, the intermediate PTF (iPTF). This is the first large, homogeneous sample of SNe Ic-BL from an untargeted survey. Furthermore, given the high observational cadence of iPTF, most of these SNe Ic-BL were discovered soon after explosion. We present K-corrected Bgriz light curves of these SNe, obtained through photometry on template-subtracted images. We analyzed the shape of the r-band light curves, finding a correlation between the decline parameter Delta m(15) and the rise parameter Delta m-(10 ). We studied the SN colors and, based on g - r, we estimated the host-galaxy extinction for each event. Peak r-band absolute magnitudes have an average of -18.6 +/- 0.5 mag. We fit each r-band light curve with that of SN 1998bw (scaled and stretched) to derive the explosion epochs. We computed the bolometric light curves using bolometric corrections, r-band data, and g - r colors. Expansion velocities from Fen were obtained by fitting spectral templates of SNe Ic. Bolometric light curves and velocities at peak were fitted using the semianalytic Arnett model to estimate ejecta mass M-ej , explosion energy E-K and Ni-56 mass M( Ni-56) for each SN. We find average values of M-ej = 4 +/- 3 M-circle dot, E-K = (7 +/- 6) x 10(51) erg, and M( Ni-56) = 0.31 +/- 0.16 M-circle dot . The parameter distributions were compared to those presented in the literature and are overall in agreement with them. We also estimated the degree of Ni-56 mixing using scaling relations derived from hydrodynamical models and we find that all the SNe are strongly mixed. The derived explosion parameters imply that at least 21% of the progenitors of SNe Ic-BL are compatible with massive (>28 M-circle dot), possibly single stars, whereas at least 64% might come from less massive stars in close binary systems.

  • 14.
    Taddia, Francesco
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. 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).
    Fremling, C.
    Karamehmetoglu, Emir
    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).
    Lunnan, Ragnhild
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    West, Stuart
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Gal-Yam, A.
    The luminous late-time emission of the type-Ic supernova iPTF15dtg-evidence for powering from a magnetar?2019In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 621, article id A64Article in journal (Refereed)
    Abstract [en]

    Context. The transient iPTF15dtg is a type-Ic supernova (SN) showing a broad light curve around maximum light, consistent with massive ejecta if we assume a radioactive-powering scenario.

    Aims. We aim to study the late-time light curve of iPTF15dtg, which turned out to be extraordinarily luminous for a stripped-envelope (SE) SN, and investigate possible powering mechanisms.

    Methods. We compare the observed light curves to those of other SE SNe and also to models for the (56) Co decay. We analyze and compare the spectra to nebular spectra of other SE SNe. We build a bolometric light curve and fit it with different models, including powering by radioactivity, magnetar powering, and a combination of the two.

    Results. Between 150 and 750 d post-explosion, the luminosity of iPTF15dtg declined by merely two magnitudes instead of the six magnitudes expected from Co-56 decay. This is the first spectroscopically regular SE SN found to show this behavior. The model with both radioactivity and magnetar powering provides the best fit to the light curve and appears to be the most realistic powering mechanism. An alternative mechanism might be circumstellar-medium (CSM) interaction. However, the spectra of iPTF15dtg are very similar to those of other SE SNe, and do not show signs of strong CSM interaction.

    Conclusions. The object iPTF15dtg is the first spectroscopically regular SE SN whose light curve displays such clear signs of a magnetar contributing to its late-time powering. Given this result, the mass of the ejecta needs to be revised to a lower value, and therefore the progenitor mass could be significantly lower than the previously estimated >35 M-circle dot.

  • 15.
    Tartaglia, Leonardo
    et al.
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Pastorello, 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).
    Fransson, Claes
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Mattila, S.
    Fraser, 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).
    Tomasella, L.
    Turatto, M.
    Morales-Garoffolo, A.
    Elias-Rosa, N.
    Lundqvist, Peter
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Harmanen, J.
    Reynolds, T.
    Cappellaro, E.
    Barbarino, Cristina
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Nyholm, Anders
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Kool, Erik
    Stockholm University, Faculty of Science, Department of Astronomy. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Ofek, E.
    Gao, X.
    Jin, Z.
    Tan, H.
    Sand, D. J.
    Ciabattari, F.
    Wang, X.
    Zhang, J.
    Huang, F.
    Li, W.
    Mo, J.
    Rui, L.
    Xiang, D.
    Zhang, T.
    Hosseinzadeh, G.
    Howell, D. A.
    McCully, C.
    Valenti, S.
    Benetti, S.
    Callis, E.
    Sagués Carracedo, Ana
    Stockholm University, Faculty of Science, Department of Physics. Stockholm University, Faculty of Science, The Oskar Klein Centre for Cosmo Particle Physics (OKC).
    Fremling, C.
    Kangas, T.
    Rubin, A.
    Somero, A.
    Terreran, G.
    The long-lived Type IIn SN 2015da: Infrared echoes and strong interaction within an extended massive shell star star star2020In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 635, article id A39Article in journal (Refereed)
    Abstract [en]

    In this paper we report the results of the first similar to four years of spectroscopic and photometric monitoring of the Type IIn supernova SN 2015da (also known as PSN J13522411+3941286, or iPTF16tu). The supernova exploded in the nearby spiral galaxy NGC 5337 in a relatively highly extinguished environment. The transient showed prominent narrow Balmer lines in emission at all times and a slow rise to maximum in all bands. In addition, early observations performed by amateur astronomers give a very well-constrained explosion epoch. The observables are consistent with continuous interaction between the supernova ejecta and a dense and extended H-rich circumstellar medium. The presence of such an extended and dense medium is difficult to reconcile with standard stellar evolution models, since the metallicity at the position of SN 2015da seems to be slightly subsolar. Interaction is likely the mechanism powering the light curve, as confirmed by the analysis of the pseudo bolometric light curve, which gives a total radiated energy greater than or similar to 10(51) erg. Modeling the light curve in the context of a supernova shock breakout through a dense circumstellar medium allowed us to infer the mass of the prexisting gas to be similar or equal to 8 M-circle dot, with an extreme mass-loss rate for the progenitor star similar or equal to 0.6 M-circle dot yr(-1), suggesting that most of the circumstellar gas was produced during multiple eruptive events. Near- and mid-infrared observations reveal a fluxexcess in these domains, similar to those observed in SN 2010jl and other interacting transients, likely due to preexisting radiatively heated dust surrounding the supernova. By modeling the infrared excess, we infer a mass greater than or similar to 0.4 x 10(-3) M-circle dot for the dust.

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