High-energy spectrum of the galactic center black hole Sgr A

Research output: Contribution to journalArticlepeer-review


The massive blackhole candidate Sgr A* may be accreting from an ambient Galactic center wind at a rate ≈ 1022 g s-1. Dissipational processes within the large-scale quasi-spherical infall, from 50 rg to 105 rg (where rg = 3 × 1011 cm is the Schwarzschild radius for M = 106 M) can account well for the observed radio spectrum and flux (due to cyclotron/synchrotron emission) and its X-ray/Gamma-ray luminosity (apparently due to Bremsstrahlung emission). Small scale instabilities associated with the stagnation region of the flow produce fluctuations in the accretion rate with an amplitude of up to 30% and a time scale of several months to over a year. This may account for the long term variability of the high-energy (and radio) luminosity observed from Sgr A*. Although the average accreted angular momentum is approximately zero, these instabilities also induce fluctuations in the specific angular momentum of the accreted gas that lead to a circularized flow at distances less than about 20 rg. Optically thick emission from this "disk" (roughly the size of Mercury's orbit) is the origin of the IR flux recently detected from the location of Sgr A*, but is not itself a significant source of high-energy emission. Published by Elsevier Science on behalf of COSPAR.

Original languageEnglish (US)
Pages (from-to)71-74
Number of pages4
JournalAdvances in Space Research
Issue number1
StatePublished - 1997

ASJC Scopus subject areas

  • Aerospace Engineering
  • Astronomy and Astrophysics
  • Geophysics
  • Atmospheric Science
  • Space and Planetary Science
  • Earth and Planetary Sciences(all)


Dive into the research topics of 'High-energy spectrum of the galactic center black hole Sgr A'. Together they form a unique fingerprint.

Cite this