Supernovae Ib and Ic from the explosion of helium stars

Luc Dessart,Norbert Langer,Sung-Chul Yoon,David R Aguilera-Dena

doi:10.1051/0004-6361/202038763

Abstract

Much difficulty has so far prevented the emergence of a consistent scenario for the origin of Type Ib and Ic supernovae (SNe). Either the SN rates or the ejecta masses and composition were in tension with inferred properties from observations. Here, we follow a heuristic approach by examining the fate of helium stars in the mass range from 4 to 12 M⊙, which presumably form in interacting binaries. The helium stars were evolved using stellar wind mass loss rates that agree with observations and which reproduce the observed luminosity range of galactic Wolf-Rayet stars, leading to stellar masses at core collapse in the range from 3 to 5.5 M⊙. We then exploded these models adopting an explosion energy proportional to the ejecta mass, which is roughly consistent with theoretical predictions. We imposed a fixed 56Ni mass and strong mixing. The SN radiation from 3 to 100 d was computed self-consistently, starting from the input stellar models using the time-dependent nonlocal thermodynamic equilibrium radiative-transfer code CMFGEN. By design, our fiducial models yield very similar light curves, with a rise time of about 20 d and a peak luminosity of ~1042.2 erg s−1, which is in line with representative SNe Ibc. The less massive progenitors retain a He-rich envelope and reproduce the color, line widths, and line strengths of a representative sample of SNe Ib, while stellar winds remove most of the helium in the more massive progenitors, whose spectra match typical SNe Ic in detail. The transition between the predicted Ib-like and Ic-like spectra is continuous, but it is sharp, such that the resulting models essentially form a dichotomy. Further models computed with varying explosion energy, 56Ni mass, and long-term power injection from the remnant show that a moderate variation of these parameters can reproduce much of the diversity of SNe Ibc. We conclude that massive stars stripped by a binary companion can account for the vast majority of ordinary Type Ib and Ic SNe and that stellar wind mass loss is the key to removing the helium envelope in the progenitors of SNe Ic.

Highlights

Further models computed with varying explosion energy, 56Ni mass, and long-term power injection from the remnant show that a moderate variation of these parameters can reproduce much of the diversity of SNe Ibc
The same applies to the SN Ibc sample, for which one finds that the 56Ni-power model combined with the standard neutrino-driven mechanism cannot explain the high-luminosity end. These brighter events probably owe their luminosity to a distinct power source. It seems that the grid of models we present here, based on moderate explosion energies, a range of 56Ni masses between 0.08 and 0.16 M, or boosted by a slowly rotating magnetar can reproduce the energetics of most SNe Ibc light curves
We have presented a set of nonLTE time-dependent radiative transfer simulations for explosions arising from He star progenitors evolved with mass loss and at solar metallicity

Summary

Introduction

Binary-star evolution has been recognized as an essential ingredient for the production of Type I core-collapse supernovae (SNe) since the 1980s (Wheeler & Levreault 1985; Wheeler et al 1987; Ensman & Woosley 1988; Podsiadlowski et al 1992; Woosley et al 1995; Vanbeveren et al 1998; Wellstein & Langer 1999; Dessart et al 2011; Smith et al 2011; Langer 2012) This result was required to explain the frequencies of SNe Ibc (as well as SNe IIb), their short rise times to maximum light of about 20 d, and the narrow light-curve widths around bolometric maximum (see for example the analyses of large samples by Drout et al 2011, Taddia et al 2015; Lyman et al 2016, or Prentice et al 2016, 2019). Depending on the mass loss rate, the winds of higher mass He-stars may or may not peel off the He-rich outer layers and produce a SN Ic, assuming that He deficiency is a prerequisite for a Type Ic classification (Liu et al 2016)

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Discussion

Conclusion