The Explosion of Helium Stars Evolved with Mass Loss

Abstract

Light curves, explosion energies, and remnant masses are calculated for a grid of supernovae resulting from massive helium stars that have been evolved including mass loss. These presupernova stars should approximate the results of binary evolution for stars in interacting systems that lose their envelopes close to the time of helium core ignition. Initial helium star masses are in the range 2.5 to 40 M , which correspond to main sequence masses of about 13 to 90 M . Common Type Ib and Ic supernovae result from stars whose final masses are approximately 2.5 to 5.6 M . For heavier stars, a large fraction of collapses lead to black holes, though there is an island of explodability for presupernova masses near 10 M . The median neutron star mass in binaries is 1.35-1.38 M and the median black hole mass is between 9 and 11 M . Even though black holes less massive than 5 M are rare, they are predicted down to the maximum neutron star mass. There is no empty "gap", only a less populated mass range. For standard assumptions regarding the explosions and nucleosynthesis, the models predict light curves that are fainter than the brighter common Type Ib and Ic supernovae. Even with a very liberal, but physically plausible increase in 56 Ni production, the highest energy models are fainter, at peak, than 10 42.6 erg s −1 , and very few approach that limit. The median peak luminosity ranges from 10 42.0 to 10 42.3 erg s −1 . Possible alternatives to the standard neutrino-powered and radioactive-illuminated models are explored. Magnetars are a promising alternative. Several other unusual varieties of Type I supernovae at both high and low mass are explored.

Supernovae Ib and Ic from the explosion of helium stars

“…As discussed by Yoon (2017), these models also produce faint WC stars at death, with log L in the range 4.6−5.2. The final mass and luminosity of these models appear similar to those of Ertl et al (2020) for their "1.5 ×Ṁ" prescription (see their Table 1).…”

“…Unlike all previous studies, we address the suitability of the models both against the photometric properties and the spectroscopic properties using nonlocal thermodynamic equilibrium (nonLTE) time-dependent radiative transfer calculations that encompass the ejecta evolution from 3 to 50-100 d after explosion. Woosley (2019) and Ertl et al (2020) performed similar simulations for the evolution and explosion of He stars (with a number of differences in the approach) but these were limited to the computation of SN bolometric light curves and a coarser comparison to observations than presented here.…”

Is there a supernova bound on axions?

“…According to [74], "explosion models" of SN1987A, quoted from Refs. [76] and [77], indicate a gravitational mass M for the compact remnant that is smaller than the critical mass needed to form a BH (about 2.3 M ⊙ ). This, again according to [74], "strongly suggests that a BH remnant in SN1987A is unlikely".…”

“…However, the simulations of Ref. [76] and [77] were artificial DνM explosions: the explosion energy and the compact remnant mass in these simulations were free parameters, selected by hand (see Sec. 2.2 in [76] and Sec.…”

“…2.2 in [76] and Sec. 3.1 in [77]) by artificially adjusting the neutrino luminosity of the compact object until explosion is reached. In other words, Ref.…”