THE GALACTIC CENTER WEATHER FORECAST

In accretion-based models for Sgr A*, the X-ray, infrared, and millimeter emission arise in a hot, geometrically thick accretion flow close to the black hole. The spectrum and size of the source depend on the black hole mass accretion rate (M) over dot. Since Gillessen et al. have recently discovered a cloud moving toward Sgr A* that will arrive in summer 2013, (M) over dot may increase from its present value (M) over dot(0). We therefore reconsider the best-bet accretion model of Moscibrodzka et al., which is based on a general relativistic MHD flow model and fully relativistic radiative transfer, for a range of (M) over dot. We find that for modest increases in (M) over dot. the characteristic ring of emission due to the photon orbit becomes brighter, more extended, and easier to detect by the planned Event Horizon Telescope submillimeter Very Long Baseline Interferometry experiment. If (M) over dot greater than or similar to 8 (M) over dot(0), this silhouette of the black hole will be hidden beneath the synchrotron photosphere at 230 GHz, and for (M) over dot greater than or similar to 16 (M) over dot(0) the silhouette is hidden at 345 GHz. We also find that for (M) over dot > 2 (M) over dot(0) the near-horizon accretion flow becomes a persistent X-ray and mid-infrared source, and in the near-infrared Sgr A* will acquire a persistent component that is brighter than currently observed flares.