Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events

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  • E. Y. Hsiao, Florida State University
  • ,
  • P. Hoeflich, Florida State University
  • ,
  • C. Ashall, Florida State University
  • ,
  • J. Lu, Florida State University
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  • C. Contreras, Carnegie Observatories, Las Campanas Observatory, La Serena, Chile
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  • C. R. Burns, Observatories of the Carnegie Institution for Science
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  • M. M. Phillips, Las Campanas Observatory
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  • L. Galbany, University of Granada
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  • J. P. Anderson, European Southern Observatory
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  • C. Baltay, Yale University
  • ,
  • E. Baron, Homer L. Dodge Department of Physics and Astronomy
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  • S. Castellón, Las Campanas Observatory
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  • S. Davis, Florida State University
  • ,
  • Wendy L. Freedman, University of Chicago
  • ,
  • C. Gall
  • C. Gonzalez, Las Campanas Observatory
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  • M. L. Graham, University of Washington
  • ,
  • M. Hamuy, Universidad de Chile
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  • T. W.S. Holoien, Observatories of the Carnegie Institution for Science
  • ,
  • E. Karamehmetoglu
  • K. Krisciunas, Texas A and M University
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  • S. Kumar, Florida State University
  • ,
  • H. Kuncarayakti, University of Turku
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  • N. Morrell, Las Campanas Observatory
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  • T. J. Moriya, National Institutes of Natural Sciences - National Astronomical Observatory of Japan, Monash University
  • ,
  • P. E. Nugent, Lawrence Berkeley National Laboratory, University of California at Berkeley
  • ,
  • S. Perlmutter, Lawrence Berkeley National Laboratory, University of California at Berkeley
  • ,
  • S. E. Persson, Observatories of the Carnegie Institution for Science
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  • A. L. Piro, Carnegie Institution of Washington
  • ,
  • D. Rabinowitz, Yale University
  • ,
  • M. Roth, GMTO Corporation, Las Campanas Observatory
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  • M. Shahbandeh, Florida State University
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  • B. J. Shappee, University of Hawaii
  • ,
  • M. D. Stritzinger
  • N. B. Suntzeff, Texas A and M University
  • ,
  • F. Taddia
  • S. A. Uddin, Observatories of the Carnegie Institution for Science

The Type Ia supernova (SN Ia) LSQ14fmg exhibits exaggerated properties that may help to reveal the origin of the "super-Chandrasekhar"(or 03fg-like) group. The optical spectrum is typical of a 03fg-like SN Ia, but the light curves are unlike those of any SNe Ia observed. The light curves of LSQ14fmg rise extremely slowly. At -23 rest-frame days relative to B-band maximum, LSQ14fmg is already brighter than MV = -19 mag before host extinction correction. The observed color curves show a flat evolution from the earliest observation to approximately 1 week after maximum. The near-infrared light curves peak brighter than -20.5 mag in the J and H bands, far more luminous than any 03fg-like SNe Ia with near-infrared observations. At 1 month past maximum, the optical light curves decline rapidly. The early, slow rise and flat color evolution are interpreted to result from an additional excess flux from a power source other than the radioactive decay of the synthesized 56Ni. The excess flux matches the interaction with a typical superwind of an asymptotic giant branch (AGB) star in density structure, mass-loss rate, and duration. The rapid decline starting at around 1 month past B-band maximum may be an indication of rapid cooling by active carbon monoxide (CO) formation, which requires a low-temperature and high-density environment. These peculiarities point to an AGB progenitor near the end of its evolution and the core degenerate scenario as the likely explosion mechanism for LSQ14fmg.

OriginalsprogEngelsk
Artikelnummer140
TidsskriftAstrophysical Journal
Vol/bind900
Nummer2
Antal sider17
ISSN0004-637X
DOI
StatusUdgivet - sep. 2020

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