Journal Article

Core-collapse explosions of Wolf–Rayet stars and the connection to Type IIb/Ib/Ic supernovae

Luc Dessart, D. John Hillier, Eli Livne, Sung-Chul Yoon, Stan Woosley, Roni Waldman and Norbert Langer

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 414, issue 4, pages 2985-3005
Published in print July 2011 | ISSN: 0035-8711
Published online July 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2011.18598.x
Core-collapse explosions of Wolf–Rayet stars and the connection to Type IIb/Ib/Ic supernovae

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We present non-Local Thermodynamic Equilibrium (LTE) time-dependent radiative-transfer simulations of supernova (SN) IIb/Ib/Ic spectra and light curves, based on ∼1051 erg piston-driven ejecta, with and without 56Ni, produced from single and binary Wolf–Rayet (WR) stars evolved at solar and sub-solar metallicities. Our bolometric light curves show a 10-d long post-breakout plateau with a luminosity of 1–5 × 107 L, visually brighter by ≳10 mag than the progenitor WR star. In our 56Ni-rich models, with ∼3 M ejecta masses, this plateau precedes a 20 to 30 d long re-brightening phase initiated by the outward-diffusing heat wave powered by radioactive decay at depth. A larger ejecta mass or a deeper 56Ni location increases the heat diffusion time and acts to both delay and broaden the light-curve peak. Discriminating between the two effects requires spectroscopic modelling. In low ejecta-mass models with moderate mixing, γ-ray leakage starts as early as ∼50 d after explosion and causes the nebular luminosity to steeply decline by ∼0.02 mag d−1. Such signatures, which are observed in standard SNe IIb/Ib/Ic, are consistent with low-mass progenitors derived from a binary-star population. We propose that the majority of stars with an initial mass ≲20 M yield SNe II-P if ‘effectively’ single, SNe IIb/Ib/Ic if part of a close binary system, and SN-less black holes if more massive. Our ejecta, with outer hydrogen mass fractions as low as ≳0.01 and a total hydrogen mass of ≳0.001 M, yield the characteristic SN IIb spectral morphology at early times. However at later times, ∼15 d after the explosion, only Hα may remain as a weak absorption feature. Our binary models, characterized by helium surface mass fractions of ≳0.85, systematically show He i lines during the post-breakout plateau, irrespective of the 56Ni abundance. Synthetic spectra show a strong sensitivity to metallicity, which offers the possibility to constrain it directly from SN spectroscopic modelling.

Keywords: radiative transfer; stars: atmospheres; stars: evolution; supernovae: individual: SN 2008D

Journal Article.  16790 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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