A Broad Iron Line in LMC X-1. (arXiv:1209.3269v1 [astro-ph.HE])

A Broad Iron Line in LMC X-1. (arXiv:1209.3269v1 [astro-ph.HE]):
We present results from a deep Suzaku observation of the black hole in LMC
X-1, supplemented by coincident monitoring with RXTE. We identify broad
relativistic reflection features in a soft disc-dominated spectrum. A strong
and variable power-law component of emission is present which we use to
demonstrate that enhanced Comptonisation strengthens disc reflection. We
constrain the spin parameter of the black hole by modelling LMC X-1's broad
reflection features. For our primary and most comprehensive spectral model, we
obtain a high value for the spin: a* = 0.97(+0.01,-0.13) (68 per cent
confidence). However, by additionally considering two alternate models as a
measure of our systematic uncertainty, we obtain a broader constraint: a* =
0.97(+0.02,-0.25). Both of these spin values are entirely consistent with a
previous estimate of spin obtained using the continuum-fitting method. At 99
per cent confidence, the reflection features require a* > 0.2. In addition to
modelling the relativistically broadened reflection, we also model a sharp and
prominent reflection component that provides strong evidence for substantial
reprocessing in the wind of the massive companion. We infer that this wind
sustains the ionisation cone surrounding the binary system; this hypothesis
naturally produces appropriate and consistent mass, time, and length scales for
the cone structure.