Black-hole states in external galaxies
Abstract
A large number of Ultra-Luminous X-ray Sources in external galaxies is now known, but the discussion about their nature is still unsettled: intermediate-mass black holes or stellar-mass black holes accreting above the Eddington limit? A promising path that can provide an answer is through comparison with "normal" stellar-mass black holes. These display separate states, identified from both their energy spectra and their fast variability. Although the nature of these states and their transitions is not clear, such a comparison can be extremely useful. In this paper, I briefly outline our current phenomenological knowledge of these states and present a (partial) overview of the different approaches followed to make these comparisons.
- Publication:
-
Astronomische Nachrichten
- Pub Date:
- May 2011
- DOI:
- 10.1002/asna.201011492
- arXiv:
- arXiv:1012.0783
- Bibcode:
- 2011AN....332..324B
- Keywords:
-
- accretion;
- accretion disks;
- galaxies: stellar content;
- X-rays: binaries;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 6 pages, 8 figures, accepted for publication in Astronomische Nachrichten, to appear in the proceedings of the conference "Ultra-Luminous X-ray sources and Middle Weight Black Holes" (Madrid, May 24-26, 2010)