Session P09: The Spins of Stellar-Mass Black Holes

From 1D to 3D simulations: the pursuit to model the spins and tilts of stellar-mass black holes

Understanding the spin magnitudes and tilts of stellar-mass black holes is crucial for unraveling their evolutionary histories. As the sensitivity of electromagnetic telescopes and gravitational wave detectors increases, we will gain precise measurements of these properties for both Galactic and high-redshift populations. To make sense of this data, we must accurately model the physical processes that are responsible for shaping the spins and tilts of these stellar-mass black holes. This pursuit demands a multitude of methodologies and theoretical perspectives. In this talk, I will review the existing models for both spin magnitudes and tilts, exploring insights gained from theoretical studies on stellar and binary evolution, as well as accretion disk simulations. I will highlight what these studies have revealed about the spins and tilts of stellar-mass black holes and outline the questions we need to address in our pursuit of a comprehensive understanding of the formation and lives of stellar-mass black holes.   

The spins of stellar-mass black holes measured with gravitational waves

With more than one hundred compact binary mergers detected in gravitational-wave data, it is becoming possible to measure the properties of the astrophysical population -- or populations -- that generate the sources. In this talk I will focus on gravitational-wave measurements of black hole spin magnitude and orientation, which can help differentiate and characterize the formation channel(s) of LIGO-Virgo-KAGRA's compact binaries. First, I will explain why these measurements are proving more challenging than what some of the early studies had forecast. Then I will discuss the existing constraints, including possible hints of correlation between spin magnitude and other parameters. Finally, I will show how these uncertain measurements will evolve as more sources are detected.   

EM Observations Overview: Electromagnetic probes of Black Hole rotation

The age of X-ray Astronomy started in 1962, through the discovery of the first source of X-rays outside of our solar system: Scorpius X-1. Only two years later, the galactic black hole Cygnus X-1 was discovered, back when black holes were mere solutions to Einstein's field equations. Throughout the following 60 years, more than 50 X-ray observatories were launched, all producing the data that led to the exponential evolution of our understanding of those mysterious objects, and their effects on their surroundings. However, the picture explaining the physics of black holes is far from complete, especially regarding their rotation, characterized through the dimensionless spin parameter. In this talk, I will discuss the evolution of X-ray methods for probing black hole rotation based on spectral, timing, and polarization measurements, discuss the current results, views, and limitations of the field, and hint at directions for the future, both from an observational and theoretical perspective.