FLUX-DENSITY OF SAGITTARIUS-A AT LAMBDA=3 MILLIMETERS

We have analyzed aperture synthesis observations of Sgr A at lambda = 3 millimeters from 1985 to 1990. We find significant flux density variations from 0.8 to 2.3 Jy with timescales as short as approximately 10 days. Spectra during the decay of a flare in 1990 show a turnover between 23 and 89 GHz. The variations may be associated with unstable accretion onto a black hole. The rapid flux density variations do not significantly degrade the 3 millimeter wavelength images but are a source of confusion for the determination of the spectrum of Sgr A*. The mean flux density of Sgr A* at 85-89 GHz is approximately 1.1 Jy in 1985-86 and 1988-90. There is a plume of emission extending 10'' to the north of Sgr A* which is probably associated with the tail of IRS 7. The integrated flux density of 110 mJy is consistent with optically thick thermal and/or dust emission in the tail. The integrated flux density within a 2' field at lambda = 3 mm is 27 Jy from a combination of BIMA (Berkeley Illinois Maryland Association) and Nobeyama data. The previously reported nonthermal emission from this area at lambda = 3 mm is probably the poorly sampled large-scale emission from a halo component which may or may not be associated with the Galactic center.