THE CONSTANT INNER-DISK RADIUS OF LMC X-3: A BASIS FOR MEASURING BLACK HOLE SPIN

• Main Authors: Steiner, James F. (Author), McClintock, Jeffrey E. (Author), Gou, Lijun (Author), Yamada, Shin'ya (Author), Narayan, Ramesh (Author), Remillard, Ronald A (Author)
• Other Authors: MIT Kavli Institute for Astrophysics and Space Research (Contributor), Remillard, Ronald Alan (Contributor)
• Format: Article
• Language: English
• Published: IOP Publishing, 2015-02-26T18:40:50Z.
• Subjects: Article
• Online Access: Get fulltext

The black hole binary system LMC X-3 has been observed by virtually every X-ray mission since the inception of X-ray astronomy. Among the persistent sources, LMC X-3 is uniquely both habitually soft and highly variable. Using a fully relativistic accretion disk model, we analyze hundreds of spectra collected during eight X-ray missions that span 26 years. For a selected sample of 391 RXTE spectra, we find that to within ≈2% the inner radius of the accretion disk is constant over time and unaffected by source variability. Even considering an ensemble of eight X-ray missions, we find consistent values of the radius to within ≈4%-6%. Our results provide strong evidence for the existence of a fixed inner-disk radius. The only reasonable inference is that this radius is closely associated with the general relativistic innermost stable circular orbit. Our findings establish a firm foundation for the measurement of black hole spin.
Goddard Space Flight Center