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A Jet‐ADAF Model for Sgr A*
Author(s) -
Yuan F.,
Markoff S.,
Falcke H.
Publication year - 2003
Publication title -
astronomische nachrichten
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.394
H-Index - 63
eISSN - 1521-3994
pISSN - 0004-6337
DOI - 10.1002/asna.200385044
Subject(s) - physics , astrophysics , accretion (finance) , supermassive black hole , bremsstrahlung , jet (fluid) , galactic center , astronomy , active galactic nucleus , black hole (networking) , radius , galaxy , electron , mechanics , nuclear physics , computer network , routing protocol , routing (electronic design automation) , computer security , computer science , link state routing protocol
We briefly review the observations and theoretical models for Sgr A*, the supermassive black hole in the center of our Galaxy, emphasizing the coupled jet plus accretion disk model for this source. In this model, the accretion flow is described as an ADAF fed by hot plasma in the Galactic Center region. At the innermost region of the accretion flow, a small fraction of the accretion flow is ejected out and forms a jet. Because the accretion flow is supersonic at the innermost region, during this process a standing shock occurs. As a result, the electron temperature increases to ∼2 × 10 11 K, which is about 10 times higher than the highest temperature attained in the ADAF, therefore leading to strong radiation via synchrotron and the Compton scattering processes. The emergent spectrum of Sgr A* is the sum of the emission from jet and underlying ADAF. Specifically, the submm‐bump is produced by the base of the jet, while the radio spectrum is due to the outer part of the jet. The X‐ray flux in the quiescent state is the sum of the bremsstrahlung emission from the underlying accretion flow and SSC from the jet. We also briefly discuss the application of our model to another low‐luminosity AGN, NGC4258.