H and He in stripped-envelope SNe - how much can be hidden?
Abstract
H and He features in photospheric spectra have rarely been used to constrain the structure of Type IIb/Ib/Ic supernovae (SNe IIb/Ib/Ic). The lines have to be modelled with a detailed non-local-thermodynamic-equilibrium (NLTE) treatment, including effects uncommon in stars. Once this is done, however, one obtains valuable hints on the characteristics of progenitors and explosions (composition, explosion energy, . . .). We have extended a radiative transfer code to compute synthetic spectra of SNe IIb, Ib and Ic. Here, we discuss our first larger set of models, focusing on the question: How much H/He can be hidden (i.e. remain undetected in photospheric spectra) in SNe Ib/Ic? For the SNe studied (relatively low M ej = 1. . .3 M⊙), we find a limit of M He <~ 0.1 M ⊙ in SNe Ic (no unambiguous He lines). Stellar evolution models for single stars normally always yield higher masses. We suggest that low- or moderate-mass SNe Ic result from efficient envelope stripping in binaries. We propose similar studies on H/He in high-mass and extremely aspherical SNe, and observations covering the region of He I λ 20581.
- Publication:
-
Death of Massive Stars: Supernovae and Gamma-Ray Bursts
- Pub Date:
- September 2012
- DOI:
- 10.1017/S1743921312012793
- Bibcode:
- 2012IAUS..279..122H
- Keywords:
-
- supernovae: general;
- supernovae: individual (SN 2008ax;
- SN 1994I);
- techniques: spectroscopic;
- radiative transfer