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

International audienceWe present non-Local Thermodynamic Equilibrium (LTE) time-dependent radiative-transfer simulations of supernova (SN) IIb/Ib/Ic spectra and light curves, based on similar to 10(51) erg piston-driven ejecta, with and without Ni-56, 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 x 10(7) L-circle dot, visually brighter by greater than or similar to 10 mag than the progenitor WR star. In our Ni-56-rich models, with similar to 3M(circle dot) 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 Ni-56 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, gamma-ray leakage starts as early as similar to 50 d after explosion and causes the nebular luminosity to steeply decline by similar to 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 less than or similar to 20M(circle dot) 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 greater than or similar to 0.01 and a total hydrogen mass of greater than or similar to 0.001M(circle dot), yield the characteristic SN IIb spectral morphology at early times. However at later times, similar to 15 d after the explosion, only H alpha may remain as a weak absorption feature. Our binary models, characterized by helium surface mass fractions of greater than or similar to 0.85, systematically show He I lines during the post-breakout plateau, irrespective of the Ni-56 abundance. Synthetic spectra show a strong sensitivity to metallicity, which offers the possibility to constrain it directly from SN spectroscopic modelling