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

Understand

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.