What Color is Black? Multi-Band Photometry at the location of the Black Hole Candidate SGR A*

Details What Color is Black? Multi-Band Photometry at the location of the Black Hole Candidate SGR A* What Color is Black? Multi-Band Photometry at the location of the Black Hole Candidate SGR A*

Dec 1992

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...181.3802c&link_type=abstract

American Astronomical Society, 181st AAS Meeting, #38.02; Bulletin of the American Astronomical Society, Vol. 24, p.1178

Astronomy and Astrophysics

Astronomy

10

Scientific paper

A new adaptive tip-tilt image stabilization instrument, FASTTRAC, has enabled deep high resolution images of the Galactic center to be obtained. Images in both the K band (2.2microns), and the H band (1.65microns) over a 1'x1' field were produced at 0.7" in resolution. To capitalize on this high spatial resolution; Wiener filter, and blind iterative deconvolution techniques are applied to the images to reveal any faint sources near the bright IRS 16 complex. Both these techniques independently detect a 3sigma point source within 0.2" of the nominal radio position of Sgr A*. Sgr A* is a unique compact nonthermal radio source at the dynamical center of the galaxy, and commonly believed to be a massive black hole candidate. Until now multi-band photometry of this source had not been successful, however, we have obtained a K magnitude of 13.3+/-0.5 and a H magnitude of 15.5+/-0.5. The corresponding heavily reddened H-K color is in good agreement with the value of ~ 2.0 observed at IRS 16. This color eliminates the possibility of an accidental foreground detection. The observed H-K value is also in agreement with a 2.0 power law flux typical of a thin accretion disk in the near IR. A model for Sgr A* based on a quasi-spherical wind accreting to a thin, inclined inner accretion disk around a 10(6) solar mass black hole is considered. The model self-consistently fits observed radio and X-ray data to the emmission from the quasi-spherical infall. The newly measured infrared fluxes from Sgr A* place contraints on the type and inclination of the accretion disk. This work is supported by grants from the NSF (AST 88-22465;AST 92-03336) and NASA (NAGW-2254). L.M.Close is supported by a NSERC graduate scholarship.

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