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Exploring the Spin Distribution of Stellar Mass Black Holes

Presentation #114.06 in the session Stellar-Mass and Galactic Black Holes.

Published onJun 29, 2022
Exploring the Spin Distribution of Stellar Mass Black Holes

Astrophysical black holes are entirely described by their mass and angular momentum, which can be expressed as the dimensionless spin parameter. Understanding the spin distribution across stellar-mass black holes provides an insight into the formation of black holes, supernova events, collapsar models, gamma-ray bursts, the formation and evolution of X-ray binary systems and binary black hole systems, and the physics of accretion. The preferred spin measurement techniques are “continuum fitting” (see e.g., Gou et al. 2009) and “relativistic reflection” (see e.g., Miller 2007). Relativistic reflection is independent of black hole mass, accretion rate, and distance to the system, making it a more versatile technique. Up until now, spin measurements for the same black hole using the two methods did not always agree, and even measurements using the same method did not always adopt the same sets of assumptions and theoretical prescriptions. Our work provides a pipeline that uses state of the art relativistic reflection theoretical models to fully explore the entire physical parameter space and to provide a uniform treatment of a large sample of black holes . Using our pipeline on NuSTAR data, we measure more than a dozen new black hole spins in X-ray binary systems, significantly expanding the measured sample size. Additionally, we analyze possible observational biases of the sample and compare the distribution to that of spins measured in mergers of binary black hole systems observed through gravitational waves, in order to offer a unified view of black hole spin evolution. In the future, this pipeline will also be used to remeasure old black hole spins in order to compile a distribution of measurements made using entirely consistent methods and systematic uncertainties. Understanding the distribution of black hole spins in X-ray binaries paves the way for future Gravitational Wave efforts and for future X-ray missions such as XRISM or ATHENA.

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