Author： Narayan Ramesh
Publisher： Springer Publishing Company
ISSN： 0004-640X
Source： Astrophysics and Space Science, Vol.300, Iss.1-3, 2005-11, pp. : 177-188
Disclaimer: Any content in publications that violate the sovereignty, the constitution or regulations of the PRC is not accepted or approved by CNPIEC.
Abstract
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 1012 K near the black hole), the electrons are also hot (∼109−10.5 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.
Related content
By Janiuk Agnieszka Czerny Bożena
Monthly Notices of the Royal Astronomical Society, Vol. 414, Iss. 3, 2011-07 ,pp. :
Access to resources
Recommend
