坍缩星伽马射线暴使其黑洞旋转停止
Collapsar Gamma-ray Bursts Grind their Black Hole Spins to a Halt
摘要：
在大质量恒星中心新形成的黑洞（BH）的自旋从其出生值演化，这是由于两个相互竞争的过程：气体角动量的吸积增加自旋，以及流出的BH角动量的提取减少自旋。最终，最终的平衡自旋由两个过程之间的平衡决定。为了使黑洞发射相对论性喷流并为$ γ$射线暴（GRB）提供动力，黑洞磁场需要具有动力学重要性。因此，我们考虑磁制动盘（MAD）驱动BH自旋演化的情况。通过将Lowell等人（2023）的半解析MAD BH自旋演化模型应用于B-sars，我们证明了如果BH吸积其初始质量的$ \sim 20\% $，它的无量纲自旋必然会达到小值$ a \lesssim 0.2 $ .对于这样的自旋，和质量吸积率推断从星模拟，我们表明，我们的半解析模型再现了典型的伽玛暴喷流，$L_{\rm jet}\sim10^{50}\,\,{\rm erg\,s^{-1}}$的能量。我们表明，我们的半解析模型再现了典型的伽玛暴喷流的近恒定功率。如果MAD的开始被延迟，这将允许在伽玛暴光度分布的高端出现强大的喷流，$L_{\rm jet}\sim10^{52}\,\,{\rm erg\,s^{-1}}$，但最终的自旋仍然很低，$ a \lesssim 0.3 $。这些结果与由引力波探测到的BH并合双星的低自旋是一致的。在Gottlieb等人（2023）的一篇配套论文中，我们使用伽玛射线暴观测结果将出生时的BH自旋限制为$ a \simeq 0.2 $。
英文摘要：
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 $ γ$-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 $ \sim 20\% $ of its initial mass, its dimensionless spin inevitably reaches small values, $ a \lesssim 0.2 $. For such spins, and for mass accretion rates inferred from collapsar simulations, we show that our semi-analytic model reproduces the energetics of typical GRB jets, $L_{\rm jet}\sim10^{50}\,\,{\rm erg\,s^{-1}}$. We show that our semi-analytic model reproduces the nearly constant power of typical GRB jets. If the MAD onset is delayed, this allows powerful jets at the high end of the GRB luminosity distribution, $L_{\rm jet}\sim10^{52}\,\,{\rm erg\,s^{-1}}$, but the final spin remains low, $ a \lesssim 0.3 $. These results are consistent with the low spins inferred from gravitational wave detections of binary BH mergers. In a companion paper, Gottlieb et al. (2023), we use GRB observations to constrain the natal BH spin to be $ a \simeq 0.2 $.
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