TYPE Ib/c SUPERNOVAE IN BINARY SYSTEMS. I. EVOLUTION AND PROPERTIES OF THE PROGENITOR STARS

We investigate the evolution of Type Ib/c supernova (SN Ib/c) progenitors in close binary systems, using new evolutionary models that include the effects of rotation, with initial masses of 12-25 M for the primary components, and of single helium stars with initial masses of 2.8-20 M . We find that, despite the impact of tidal interaction on the rotation of primary stars, the amount of angular momentum retained in the core at the presupernova stage in different binary model sequences converges to a value similar to those found in previous single star models. This amount is large enough to produce millisecond pulsars, but too small to produce magnetars or long gammaray bursts. We employ the most up-to-date estimate for the Wolf-Rayet mass-loss rate, and its implications for SN Ib/c progenitors are discussed in detail. In terms of stellar structure, SN Ib/c progenitors in binary systems at solar metallicity are predicted to have a wide range of final masses up to about 7 M , with helium envelopes of M He 0.16-1.5 M . Our results indicate that, if the lack of helium lines in the spectra of SNe Ic were due to small amounts of helium (e.g., M He 0.5), the distribution of both initial and final masses of SN Ic progenitors should be bimodal. Furthermore, we find that a thin hydrogen layer (0.001 M M H 0.01 M ) is expected to be present in many SN Ib progenitors at the presupernova stage. We show that the presence of hydrogen, together with a rather thick helium envelope, can lead to a significant expansion of some SN Ib/c progenitors by the time of supernova explosion. This may have important consequences for the shock break-out and supernova light curve. We also argue that some SN progenitors with thin hydrogen layers produced via Case AB/B transfer might be related to Type IIb supernova progenitors with relatively small radii of about 10 R .

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