We examine the early phase intrinsic (B - V)0 color evolution of a dozen SNe Ia discovered within three days of the inferred time of first light (t first) and have (B - V)0 color information beginning within five days of t first. The sample indicates there are two distinct early populations. The first is a population exhibiting blue colors that slowly evolve, and the second population exhibits red colors and evolves more rapidly. We find that the early blue events are all 1991T/1999aa-like with more luminous, slower declining light curves than those exhibiting early red colors. Placing the first sample on the Branch diagram (i.e., ratio of Si II λλ5972, 6355 pseudo-Equivalent widths) indicates that all blue objects are of the Branch shallow silicon (SS) spectral type, while all early red events except for the 2000cx-like SN 2012fr are of the Branch Core Normal (CN) or CooL (CL) type. A number of potential processes contributing to the early emission are explored, and we find that, in general, the viewing-angle dependance inherent in the companion collision model is inconsistent with all of the SS objects with early-time observations being blue and exhibiting an excess. We caution that great care mustmore »
Investigating the Unusual Spectroscopic Time Evolution in SN 2012fr
The type Ia supernova (SN) 2012fr displayed an unusual combination of
its Si II λλ5972, 6355 features. This includes the ratio
of their pseudo-equivalent widths, placing it at the border of the
shallow silicon (SS) and core normal (CN) spectral subtype in the Branch
diagram, while the Si II λ6355 expansion velocities place it as a
high-velocity (HV) object in the Wang et al. spectral type that most
interestingly evolves slowly, placing it in the low-velocity gradient
(LVG) typing of Benetti et al. Only 5% of SNe Ia are HV and located in
the SS+CN portion of the Branch diagram, and fewer than 10% of SNe Ia
are both HV and LVG. These features point toward SN 2012fr being quite
unusual, similar in many ways to the peculiar SN 2000cx. We modeled the
spectral evolution of SN 2012fr to see if we could gain some insight
into its evolutionary behavior. We use the parameterized radiative
transfer code SYNOW to probe the abundance stratification of SN 2012fr
at pre-maximum, maximum, and post-maximum light epochs. We also use a
grid of W7 models in the radiative transfer code PHOENIX to probe the
effect of different density structures on the formation of the more »
- Award ID(s):
- 1715133
- Publication Date:
- NSF-PAR ID:
- 10093383
- Journal Name:
- Astrophysical journal
- Volume:
- 869
- Page Range or eLocation-ID:
- 162
- ISSN:
- 1538-4357
- Sponsoring Org:
- National Science Foundation
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