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arXiv · 1006.5729

The Constant Inner-Disk Radius of LMC X-3: A Basis for Measuring Black Hole Spin

James F. Steiner·Jeffrey E. McClintock·Ronald A. Remillard·Lijun Gou·Shin'ya Yamada·Ramesh Narayan
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Abstract

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 percent 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 percent. 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 (ISCO). Our findings establish a firm foundation for the measurement of black hole spin.

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James F. Steiner, Jeffrey E. McClintock, Ronald A. Remillard, Lijun Gou, Shin'ya Yamada, Ramesh Narayan. 2010-06-29. The Constant Inner-Disk Radius of LMC X-3: A Basis for Measuring Black Hole Spin. https://doi.org/10.1088/2041-8205%2F718%2F2%2Fl117

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