TY - JOUR
T1 - Early Blue Excess from the Type Ia Supernova 2017cbv and Implications for Its Progenitor
AU - Hosseinzadeh, Griffin
AU - Sand, David J.
AU - Valenti, Stefano
AU - Brown, Peter
AU - Howell, D. Andrew
AU - McCully, Curtis
AU - Kasen, Daniel
AU - Arcavi, Iair
AU - Bostroem, K. Azalee
AU - Tartaglia, Leonardo
AU - Hsiao, Eric Y.
AU - Davis, Scott
AU - Shahbandeh, Melissa
AU - Stritzinger, Maximilian D.
N1 - Publisher Copyright:
© 2017. The American Astronomical Society. All rights reserved..
PY - 2017/8/20
Y1 - 2017/8/20
N2 - We present very early, high-cadence photometric observations of the nearby Type Ia SN 2017cbv. The light curve is unique in that it has a blue bump during the first five days of observations in the U, B, and g bands, which is clearly resolved given our photometric cadence of 5.7 hr during that time span. We model the light curve as the combination of early shocking of the supernova ejecta against a nondegenerate companion star plus a standard SN Ia component. Our best-fit model suggests the presence of a subgiant star 56 R from the exploding white dwarf, although this number is highly model-dependent. While this model matches the optical light curve well, it overpredicts the observed flux in the ultraviolet bands. This may indicate that the shock is not a blackbody, perhaps because of line blanketing in the UV. Alternatively, it could point to another physical explanation for the optical blue bump, such as interaction with circumstellar material or an unusual nickel distribution. Early optical spectra of SN 2017cbv show strong carbon (C ii λ6580) absorption up through day -13 with respect to maximum light, suggesting that the progenitor system contains a significant amount of unburned material. These early results on SN 2017cbv illustrate the power of early discovery and intense follow-up of nearby supernovae to resolve standing questions about the progenitor systems and explosion mechanisms of SNe Ia.
AB - We present very early, high-cadence photometric observations of the nearby Type Ia SN 2017cbv. The light curve is unique in that it has a blue bump during the first five days of observations in the U, B, and g bands, which is clearly resolved given our photometric cadence of 5.7 hr during that time span. We model the light curve as the combination of early shocking of the supernova ejecta against a nondegenerate companion star plus a standard SN Ia component. Our best-fit model suggests the presence of a subgiant star 56 R from the exploding white dwarf, although this number is highly model-dependent. While this model matches the optical light curve well, it overpredicts the observed flux in the ultraviolet bands. This may indicate that the shock is not a blackbody, perhaps because of line blanketing in the UV. Alternatively, it could point to another physical explanation for the optical blue bump, such as interaction with circumstellar material or an unusual nickel distribution. Early optical spectra of SN 2017cbv show strong carbon (C ii λ6580) absorption up through day -13 with respect to maximum light, suggesting that the progenitor system contains a significant amount of unburned material. These early results on SN 2017cbv illustrate the power of early discovery and intense follow-up of nearby supernovae to resolve standing questions about the progenitor systems and explosion mechanisms of SNe Ia.
KW - supernovae: general
KW - supernovae: individual (SN 2017cbv)
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U2 - 10.3847/2041-8213/aa8402
DO - 10.3847/2041-8213/aa8402
M3 - Article
AN - SCOPUS:85028452436
SN - 2041-8205
VL - 845
JO - Astrophysical Journal Letters
JF - Astrophysical Journal Letters
IS - 2
M1 - L11
ER -