Radiative-transfer models for supernovae IIb/Ib/Ic from binary-star progenitors

TL;DR

This paper presents detailed 1-D radiative transfer simulations of Type IIb/Ib/Ic supernovae from binary progenitors, analyzing their light curves, spectra, and progenitor properties to improve understanding of their observational signatures.

Contribution

It introduces new radiative transfer models for SNe IIb/Ib/Ic from binary progenitors, linking spectral features to progenitor composition and explosion parameters.

Findings

Arnett's rule overestimates Ni-56 mass by ~50%.

Presence of strong CI lines indicates helium under-abundance.

Little scatter in (V-R) color 10 days after R-band maximum.

Abstract

We present 1-D non-Local-Thermodynamic-Equilibrium time-dependent radiative-transfer simulations for supernovae (SNe) of type IIb, Ib, and Ic that result from the terminal explosion of the mass donor in a close-binary system. Here, we select three ejecta with a total kinetic energy of ~1.2e51erg, but characterised by different ejecta masses (2-5Msun), composition, and chemical mixing. The type IIb/Ib models correspond to the progenitors that have retained their He-rich shell at the time of explosion. The type Ic model arises from a progenitor that has lost its helium shell, but retains 0.32Msun of helium in a CO-rich core of 5.11Msun. We discuss their photometric and spectroscopic properties during the first 2-3 months after explosion, and connect these to their progenitor and ejecta properties including chemical stratification. For these three models, Arnett's rule overestimates the 56Ni mass by ~50% while the procedure of Katz et al., based on an energy argument, yields a more reliable estimate. The presence of strong CI lines around 9000A prior to maximum is an indicator that the pre-SN star was under-abundant in helium. As noted by others, the 1.08micron feature is a complex blend of CI, MgII, and HeI lines, which makes the identification of He uncertain in SNe Ibc unless other HeI lines can be identified. Our models show little scatter in (V-R) colour 10d after R-band maximum. We also address a number of radiative transfer properties of SNe Ibc, including the notion of a photosphere, the inference of a representative ejecta expansion rate, spectrum formation, blackbody fits and "correction factors".