Collapsar Gamma-ray Bursts Grind their Black Hole Spins to a Halt
Jonatan Jacquemin-Ide, Ore Gottlieb, Beverly Lowell, Alexander, Tchekhovskoy

TL;DR
This paper models the spin evolution of black holes in collapsars, showing that magnetic effects limit their spin to low values, which explains observed gamma-ray burst energetics and low spins from gravitational wave data.
Contribution
It introduces a semi-analytic model of magnetically arrested disk (MAD) driven black hole spin evolution in collapsars, linking low spins to GRB jet energetics and gravitational wave observations.
Findings
Black hole spins are limited to a rac{1}{5} 0.2 for typical accretion.
GRB jet luminosities are consistent with low black hole spins, rac{1}{5} to rac{1}{3} 0.3.
Delayed MAD onset can produce more luminous jets while maintaining low spins.
Abstract
The spin of a newly formed black hole (BH) at the center of a massive star evolves from its natal value due to two competing processes: accretion of gas angular momentum that increases the spin, and extraction of BH angular momentum by outflows that decreases the spin. Ultimately, the final, equilibrium spin is set by the balance between both processes. In order for the BH to launch relativistic jets and power a -ray burst (GRB), the BH magnetic field needs to be dynamically important. Thus, we consider the case of a magnetically arrested disk (MAD) driving the spin evolution of the BH. By applying the semi-analytic MAD BH spin evolution model of Lowell et al. (2023) to collapsars, we show that if the BH accretes of its initial mass, its dimensionless spin inevitably reaches small values, . For such spins, and for mass accretion rates inferred…
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Taxonomy
TopicsGamma-ray bursts and supernovae · Astrophysical Phenomena and Observations · Mechanics and Biomechanics Studies
