Astronomy and Astrophysics – Astrophysics
Scientific paper
2004-11-14
Astrophys.Space Sci. 300 (2005) 177-188
Astronomy and Astrophysics
Astrophysics
To appear in "From X-ray Binaries to Quasars: Black Hole Accretion on All Mass Scales" edited by T. Maccarone, R. Fender, L. H
Scientific paper
10.1007/s10509-005-1178-7
At luminosities below a few percent of Eddington, accreting black holes switch to a hard spectral state which is very different from the soft blackbody-like spectral state that is found at higher luminosities. The hard state is well-described by a two-temperature, optically thin, geometrically thick, advection-dominated accretion flow (ADAF) in which the ions are extremely hot (up to $10^{12}$ K near the black hole), the electrons are also hot ($\sim10^{9-10.5}$ K), and thermal Comptonization dominates the X-ray emission. The radiative efficiency of an ADAF decreases rapidly with decreasing mass accretion rate, becoming extremely low when a source reaches quiescence. ADAFs are expected to have strong outflows, which may explain why relativistic jets are often inferred from the radio emission of these sources. It has been suggested that most of the X-ray emission also comes from a jet, but this is less well established.
No associations
LandOfFree
Low-Luminosity Accretion in Black Hole X-ray Binaries and Active Galactic Nuclei does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Low-Luminosity Accretion in Black Hole X-ray Binaries and Active Galactic Nuclei, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Low-Luminosity Accretion in Black Hole X-ray Binaries and Active Galactic Nuclei will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-38819