Testing slim-disk models on the thermal spectra of LMC X-3

TL;DR

This paper introduces a new relativistic slim-disk spectral model, slimbb, and applies it to LMC X-3 data, demonstrating its effectiveness across different luminosity regimes and highlighting its potential for testing black-hole accretion theories.

Contribution

The paper develops and applies a novel spectral model, slimbb, that accurately describes relativistic slim-disk accretion including photon ray-tracing, bridging low and high luminosity regimes.

Findings

Consistency between thin and slim-disk regimes demonstrated

X-ray continuum-fitting can test black-hole accretion models

Model successfully applied to RXTE spectra of LMC X-3

Abstract

Slim-disk models describe accretion flows at high luminosities, while reducing to the standard thin disk form in the low luminosity limit. We have developed a new spectral model, slimbb, within the framework of XSPEC, which describes fully relativistic slim-disk accretion and includes photon ray-tracing that starts from the disk photosphere, rather than the equatorial plane. We demonstrate the features of this model by applying it to RXTE spectra of the persistent black-hole X-ray binary LMC X-3. LMC X-3 has the virtues of exhibiting large intensity variations while maintaining itself in soft spectral states which are well described using accretion-disk models, making it an ideal candidate to test the aptness of slimbb. Our results demonstrate consistency between the low-luminosity (thin-disk) and high luminosity (slim-disk) regimes. We also show that X-ray continuum-fitting in the high accretion rate regime can powerfully test black-hole accretion disk models.