Carnegie Supernova Project II: The Slowest Rising Type Ia Supernova LSQ14fmg and Clues to the Origin of Super-Chandrasekhar/03fg-like Events
: E. Y. Hsiao, P. Hoeflich, C. Ashall, J. Lu, C. Contreras, C. R. Burns, M. M. Phillips, L. Galbany, J. P. Anderson, C. Baltay, E. Baron, S. Castellón, S. Davis, Wendy L. Freedman, C. Gall, C. Gonzalez, M. L. Graham, M. Hamuy, T. W.-S. Holoien, E. Karamehmetoglu, K. Krisciunas, S. Kumar, H. Kuncarayakti, N. Morrell, T. J. Moriya, P. E. Nugent, S. Perlmutter, S. E. Persson, A. L. Piro, D. Rabinowitz, M. Roth, M. Shahbandeh, B. J. Shappee, M. D. Stritzinger, N. B. Suntzeff, F. Taddia, and S. A. Uddin
Publisher: IOP PUBLISHING LTD
: 2020
: Astrophysical Journal
: ASTROPHYSICAL JOURNAL
: ASTROPHYS J
: ARTN 140
: 900
: 2
: 17
: 0004-637X
: 1538-4357
DOI: https://doi.org/10.3847/1538-4357/abaf4c
: https://arxiv.org/abs/2008.05614
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 toB-band maximum, LSQ14fmg is already brighter thanJandHbands, 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 Ni-56. 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 pastB-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.
