Very massive stars, pair-instability supernovae and intermediate-mass black holes with the SEVN code

Mario Spera; Michela Mapelli

doi:10.1093/mnras/stx1576

paper

Very massive stars, pair-instability supernovae and intermediate-mass black holes with the SEVN code

arXiv:1706.06109 · doi:10.1093/mnras/stx1576

Abstract

Understanding the link between massive ( $≳ 30$ M $_{⊙}$ ) stellar black holes (BHs) and their progenitor stars is a crucial step to interpret observations of gravitational-wave events. In this paper, we discuss the final fate of very massive stars (VMSs), with zero-age main sequence (ZAMS) mass $> 150$ M $_{⊙}$ , accounting for pulsational pair-instability supernovae (PPISNe) and for pair-instability supernovae (PISNe). We describe an updated version of our population synthesis code SEVN, in which we added stellar evolution tracks for VMSs with ZAMS mass up to $350$ M $_{⊙}$ and we included analytical prescriptions for PPISNe and PISNe. We use the new version of SEVN to study the BH mass spectrum at different metallicity $Z$ , ranging from $Z = 2.0 \times 1 0^{- 4}$ to $Z = 2.0 \times 1 0^{- 2}$ . The main effect of PPISNe and PISNe is to favour the formation of BHs in the mass range of the first gravitational-wave event (GW150914), while they prevent the formation of remnants with mass 60 - 120 M $_{⊙}$ . In particular, we find that PPISNe significantly enhance mass loss of metal-poor ( $Z \leq 2.0 \times 1 0^{- 3}$ ) stars with ZAMS mass $60 \leq$ M $_{ZAMS} /$ M $_{⊙} \leq 125$ . In contrast, PISNe become effective only for moderately metal-poor ( $Z < 8.0 \times 1 0^{- 3}$ ) VMSs. VMSs with M $_{ZAMS} ≳ 220$ M $_{⊙}$ and $Z < 1 0^{- 3}$ do not undergo PISNe and form intermediate-mass BHs (IMBHs, with mass $≳ 200$ M $_{⊙}$ ) via direct collapse.

12 pages, 9 figures, 3 tables, accepted for publication in MNRAS

Very massive stars, pair-instability supernovae and intermediate-mass black holes with the SEVN code

Abstract

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