Stripped-envelope stars in different metallicity environments

Abstract

Stripped-envelope stars can be observed as Wolf-Rayet (WR) stars or as less luminous hydrogen-poor stars with low mass-loss rates and transparent winds. Both types are potential progenitors of Type I core-collapse supernovae (SNe). We used grids of core-collapse models obtained from single helium stars at different metallicities to study the effects of metallicity on the transients and remnants these stars produce. We characterised the surface and core properties of our core-collapse models and investigated their ‘explodability’ using three criteria. In the cases where explosions are predicted, we estimated the ejecta mass, explosion energy, nickel mass, and neutron star (NS) mass. Otherwise, we predicted the mass of the resulting black hole (BH). We constructed a simplified population model and find that the properties of SNe and compact objects depend strongly on metallicity. The ejecta masses and explosion energies for Type Ic SNe are best reproduced by models with Z = 0.04 that exhibit strong winds during core helium burning. This implies that either their mass-loss rates are underestimated or that Type Ic SN progenitors experience mass loss through other mechanisms before exploding. The distributions of ejecta masses, explosion energies, and nickel mass for Type Ib SNe are not well reproduced by progenitor models with WR mass loss, but are better reproduced if we assume no mass loss in progenitors with luminosities below the minimum WR star luminosity. We find that Type Ic SNe become more common as metallicity increases, and that the vast majority of progenitors of Type Ib SNe must be transparent-wind stripped-envelope stars. We find that several models with pre-collapse CO masses of up to ∼30 M⊙ may form ∼3 M⊙ BHs in fallback SNe. This may have important consequences for our understanding of SNe, binary BH and NS systems, X-ray binary systems, and gravitational wave transients.

Optical Color of Type Ib and Ic Supernovae and Implications for Their Progenitors

“…This scenario has been supported by many observational and theoretical studies as discussed in Section 1 (e.g., Matheson et al 2001;Dessart et al 2012;Hachinger et al 2012;Liu et al 2016;Fremling et al 2018;Yoon et al 2019;Dessart et al 2020;Moriya et al 2020;Teffs et al 2020;Williamson et al 2021;Shahbandeh et al 2022). Recent stellar evolution models also suggest that SN Ib and Ic progenitors would not form a continuous sequence in terms of He amount if mass-loss enhancement during the WC phase of Wolf-Rayet stars, which is implied by recent Wolf-Rayet star observations of the local universe, is assumed (see Yoon 2017 for a detailed discussion and references therein; see also Woosley et al 2021 andAguilera-Dena et al 2023). In this section, we explore the consequence of the dichotomic nature of helium content in SN Ib/Ic color (see also Yoon et al 2019).…”

Chemical Evolution of the Universe and its Consequences for Gravitational‐Wave Astrophysics

“…Both winds and binary interactions can affect the mass and structure of stellar envelope and the final core [ 66–68 ] in a way that depends on metallicity. [ 65,69 ] Stars stripped of their envelopes eject less mass from the system during the core‐collapse/supernova and potentially lead to the formation of NS/BH with small velocities (so‐called natal kicks, [ 70 ] ). This increases the chances that the binary/multiple remains bound after the formation of the compact object.…”