The Pair-instability Mass Gap for Black Holes
Abstract
Stellar evolution theory predicts a "gap" in the black hole birth function caused by the pair instability. Many presupernova stars that have a core mass below some limiting value, Mlow, after all pulsational activity is finished, collapse to black holes, while more massive ones, up to some limiting value, Mhigh, explode, promptly and completely, as pair-instability supernovae. Previous work has suggested Mlow ≈ 50 M⊙ and Mhigh ≈ 130 M⊙. These calculations have been challenged by recent LIGO observations that show many black holes merging with individual masses Mlow ≳ 65 M⊙. Here we explore four factors affecting the theoretical estimates for the boundaries of this mass gap: nuclear reaction rates, evolution in detached binaries, rotation, and hyper-Eddington accretion after black hole birth. Current uncertainties in reaction rates by themselves allow Mlow to rise to 64 M⊙ and Mhigh as large as 161 M⊙. Rapid rotation could further increase Mlow to ∼70 M⊙, depending on the treatment of magnetic torques. Evolution in detached binaries and super-Eddington accretion can, with great uncertainty, increase Mlow still further. Dimensionless Kerr parameters close to unity are allowed for the more massive black holes produced in close binaries, though they are generally smaller.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- May 2021
- DOI:
- 10.3847/2041-8213/abf2c4
- arXiv:
- arXiv:2103.07933
- Bibcode:
- 2021ApJ...912L..31W
- Keywords:
-
- Stellar mass black holes;
- Core-collapse supernovae;
- Hypernovae;
- Gravitational wave astronomy;
- 1611;
- 304;
- 775;
- 675;
- Astrophysics - Solar and Stellar Astrophysics;
- Astrophysics - High Energy Astrophysical Phenomena;
- General Relativity and Quantum Cosmology;
- Nuclear Theory
- E-Print:
- 16 pages, 4 figure panels, 6 tables, submitted to ApJ