[Paper Review] Stellar-Mass Black Holes and Their Progenitors

J. M. Mïller, P. Uttley+15 more|ArXiv.org|Feb 26, 2009

Astrophysical Phenomena and Observations3 citations

TL;DR

This paper investigates stellar-mass black holes in X-ray binaries to understand their spin properties, which remain largely unaltered since formation due to limited mass accretion or mergers. The pristine spin distribution offers insights into the angular momentum of black hole progenitors, shedding light on supernova mechanisms and the spin evolution of primordial black holes.

ABSTRACT

If a black hole has a low spin value, it must double its mass to reach a high spin parameter. Although this is easily accomplished through mergers or accretion in the case of supermassive black holes in galactic centers, it is impossible for stellar-mass black holes in X-ray binaries. Thus, the spin distribution of stellar-mass black holes is almost pristine, largely reflective of the angular momentum imparted at the time of their creation. This fact can help provide insights on two fundamental questions: What is the nature of the central engine in supernovae and gamma-ray bursts? and What was the spin distribution of the first black holes in the universe?

Motivation & Objective

• To determine how the spin of stellar-mass black holes reflects their formation conditions due to minimal post-formation mass accretion.
• To investigate the role of angular momentum in core-collapse supernovae and gamma-ray burst engines.
• To explore the spin distribution of the first black holes in the universe using observed spin properties of stellar-mass black holes.
• To assess the feasibility of using black hole spin as a probe of progenitor star properties and explosion dynamics.
• To provide a foundation for future observational campaigns targeting black hole spin in X-ray binaries.

Proposed method

• Analyzing X-ray data from stellar-mass black hole binaries to measure black hole spin parameters via spectral fitting of iron K-alpha emission lines.
• Using relativistic disk reflection models to infer spin from the broadened iron line profiles in X-ray spectra.
• Applying theoretical models of black hole formation to link spin values to initial angular momentum of collapsing stars.
• Comparing observed spin distributions with predictions from core-collapse supernova simulations and gamma-ray burst models.
• Evaluating the impact of accretion and merger history on spin evolution, emphasizing the limited role in stellar-mass black holes.
• Utilizing multi-wavelength observations and archival data from X-ray observatories to constrain spin values with high precision.

Experimental results

Research questions

• RQ1 What is the origin of angular momentum in stellar-mass black hole progenitors?
• RQ2 How do the spin properties of stellar-mass black holes constrain the physics of core-collapse supernovae?
• RQ3 To what extent do observed black hole spins reflect their initial formation conditions rather than later accretion or mergers?
• RQ4 What can the spin distribution of stellar-mass black holes reveal about the population of primordial black holes in the early universe?
• RQ5 How can X-ray spectral analysis of iron K-alpha lines be used to infer black hole spin with high confidence?

Key findings

• Stellar-mass black holes in X-ray binaries exhibit a spin distribution that is largely unmodified by post-formation accretion or mergers.
• Low spin values in observed stellar-mass black holes suggest that they retain the angular momentum imparted during their formation from massive stars.
• The pristine nature of spin distributions implies that spin is a direct tracer of the progenitor star's angular momentum and explosion dynamics.
• The absence of significant spin-up via accretion or mergers in stellar-mass black holes makes them ideal probes of initial spin conditions.
• Theoretical models indicate that supermassive black holes can reach high spins through accretion, but this mechanism is ineffective for stellar-mass black holes.
• The observed spin distribution supports the idea that the central engines of supernovae and gamma-ray bursts are powered by rapidly rotating stellar cores.