What Is the Accretion Rate in Sgr a ∗ ?
نویسنده
چکیده
The radio source Sgr A at the center of our Galaxy is believed to be a 2.6× 10M⊙ black hole which accretes gas from the winds of nearby stars. We show that limits on the X-ray and infrared emission from the Galactic Center provide an upper limit of ∼ 8 × 10M⊙ yr −1 on the mass accretion rate in Sgr A. The advection-dominated accretion flow (ADAF) model favors a rate <∼ 10 M⊙ yr . In comparison, the Bondi accretion rate onto Sgr A, estimated using the observed spatial distribution of mass losing stars and assuming non-interacting stellar winds, is ∼ 3×10M⊙ yr . There is thus rough agreement between the Bondi, the ADAF, and the X-ray inferred accretion rates for Sgr A*. We discuss uncertainties in these estimates, emphasizing the importance of upcoming observations by the Chandra X-ray observatory (CXO) for tightening the X-ray derived limits. Subject Headings: accretion, accretion disks – black holes – Galaxy: center – radio sources: Sgr A*
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