Exploring Black Hole Spin with Relativistic Reflection Spectroscopy: Insights from Stellar-mass and Supermassive Black Hole Populations

This paper investigates black hole spin using the relativistic reflection method, which analyses distorted X-ray spectra to understand accretion dynamics near the event horizon. The RELXILL series of models are very popular in anaylising refletion features. These Models enable a detailed and consistent understanding of the interaction between the accretion disk and relativistic effects. The paper shows the spin distribution of 33 black holes, including 14 stellar-mass black holes and 19 supermassive black holes. [1] High-spin (0.8) systems dominate, highlighting their association with intense relativistic effects near the innermost stable circular orbit. The high spin in stellar-mass black holes is driven by binary accretion, while the high spin in suppermassive black holes is driven by prolonged disk accretion and aligned mergers. [2] These results confirm the reliability of the method and provide insights into black hole evolution and accretion physics. Future research should explore how evolving models can refine spin predictions for complex systems.