The microquasar Cyg X-1: a short review
Abstract
We review the spectral properties of the black hole candidate Cygnus X-1. Specifically, we discuss two recent sets of multi-satellite observations. One comprises a 0.5-500 keV spectrum, obtained with every flying X-ray satellite at that time, that is among the hardest Cyg X-1 spectra observed to date. The second set is comprised of 0.5-40 keV Chandra-HETG plus RXTE-PCA spectra from a radio-quiet, spectrally soft state. We first discuss the ``messy astrophysics'' often neglected in the study of Cyg X-1, i.e., ionized absorption from the wind of the secondary and the foreground dust scattering halo. We then discuss components common to both state extremes: a low temperature accretion disk, and a relativistically broadened Fe line and reflection. Hard state spectral models indicate that the disk inner edge does not extend beyond gtrsim 40 GM/c2, and may even approach as close as ≈ 6 GM/c2. The soft state exhibits a much more prominent disk component; however, its very low normalization plausibly indicates a spinning black hole in the Cyg X-1 system.
- Publication:
-
Memorie della Societa Astronomica Italiana
- Pub Date:
- 2012
- DOI:
- 10.48550/arXiv.1107.2391
- arXiv:
- arXiv:1107.2391
- Bibcode:
- 2012MmSAI..83..202N
- Keywords:
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- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- To appear in the proceedings of "Multifrequency Behaviour of High Energy Cosmic Sources", Frascati Workshop 2011, May 23-28, Vulcano, Italy 5 pages