%AStritzinger, Maximilian%AShappee, Benjamin%APiro, Anthony%AAshall, Christopher%ABaron, E.%AHoeflich, Peter%AHolmbo, Simon%AHoloien, Thomas%APhillips, M.%ABurns, C.%AContreras, Carlos%AMorrell, Nidia%ATucker, Michael%BJournal Name: Astrophysical journal; Journal Volume: 861
%D2018%I
%JJournal Name: Astrophysical journal; Journal Volume: 861
%K
%MOSTI ID: 10093384
%PMedium: X
%TRed versus Blue: Early Observations of Thermonuclear
Supernovae Reveal Two Distinct Populations?
%XWe 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 must be
taken when interpreting early phase light curves as there may be a
variety of physical processes that are possibly at play and significant
theoretical work remains to be done.
%0Journal Article