@misc{10481/72422,
year = {2021},
month = {4},
url = {http://hdl.handle.net/10481/72422},
abstract = {Unburned carbon is potentially a powerful probe of Type Ia supernova (SN) explosion mechanisms. We present comprehensive optical and near-infrared (NIR) data on the "transitional" Type Ia SN 2015bp. An early NIR spectrum (t=−9.9 days with respect to B-band maximum) displays a striking C I λ1.0693μm line at 11.9×103~km s−1, distinct from the prominent Mg II λ1.0927μm feature, which weakens toward maximum light. SN 2015bp also displays a clear C II λ6580A notch early (t=−10.9 days) at 13.2×103~km s−1, consistent with our NIR carbon detection. At MB=−18.46, SN 2015bp is less luminous than a normal SN Ia and, along with iPTF13ebh, is the second member of the transitional subclass to display prominent early-time NIR carbon absorption. We find it unlikely that the C I feature is misidentified He I λ1.0830μm because this feature grows weaker toward maximum light, while the helium line produced in some double-detonation models grows stronger at these times. Intrigued by these strong NIR carbon detections, but lacking NIR data for other SNe Ia, we investigated the incidence of optical carbon in the sample of nine transitional SNe Ia with early-time data (t≲−4 days). We find that four display C II λ6580A, while two others show tentative detections, in line with the SN Ia population as a whole. We conclude that at least ∼50% of transitional SNe Ia in our sample do not come from sub-Chandrasekhar mass explosions due to the clear presence of carbon in their NIR and optical spectra.},
organization = {National Science Foundation (NSF)
	AST-1821967	
	AST-1821987	
	AST-1813708	
	AST-1813466	
	AST-1908972	
	PHY-1607611	
	AST1813176	
	AST-2008108},
organization = {Heising-Simons Foundation
	20201864},
organization = {National Science Foundation (NSF)
	AST-1008343	
	AST-1613426	
	AST-1613455	
	AST-1613472},
organization = {Danish Agency for Science and Technology and Innovation},
organization = {Florida Space Grant Consortium},
organization = {European Commission
	839090},
organization = {Spanish grant within the European Funds for Regional Development (FEDER)
	PGC2018-095317-B-C21},
organization = {Villum Foundation
	13261	
	28021},
organization = {Independent Research Fund Denmark
	8021-00170B},
organization = {TABASGO Foundation},
organization = {Christopher R. Redlich Fund},
organization = {Miller Institute for Basic Research in Science (U.C. Berkeley)},
organization = {International Gemini Observatory
	GN-2015A-Q-8	
	GS-2015A-Q-5},
organization = {W.M. Keck Foundation},
organization = {University of Hawaii
	80HQTR19D0030},
organization = {National Aeronautics & Space Administration (NASA)},
organization = {ESO Telescopes at the La Silla Paranal Observatory
	188.D-3003	
	191.D-0935: PESSTO},
publisher = {IOP Publishing},
title = {Strong Near-Infrared Carbon Absorption in the Transitional Type Ia SN 2015bp},
doi = {10.3847/1538-4357/abf7c3},
author = {Wyatt, S. D. and Galbany González, Lluis},
}