The Galactic Center Weather Forecast
Abstract
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 \dot{M}. Since Gillessen et al. have recently discovered a cloud moving toward Sgr A* that will arrive in summer 2013, \dot{M} may increase from its present value \dot{M}_0. We therefore reconsider the "best-bet" accretion model of Mościbrodzka et al., which is based on a general relativistic MHD flow model and fully relativistic radiative transfer, for a range of \dot{M}. We find that for modest increases in \dot{M} 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 \dot{M} \gtrsim 8 \,\dot{M}_0, this "silhouette" of the black hole will be hidden beneath the synchrotron photosphere at 230 GHz, and for \dot{M} \gtrsim 16 \,\dot{M}_0 the silhouette is hidden at 345 GHz. We also find that for \dot{M} > 2 \,\dot{M}_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.
- Publication:
-
The Astrophysical Journal
- Pub Date:
- June 2012
- DOI:
- 10.1088/2041-8205/752/1/L1
- arXiv:
- arXiv:1204.1371
- Bibcode:
- 2012ApJ...752L...1M
- Keywords:
-
- Galaxy: center;
- Astrophysics - High Energy Astrophysical Phenomena
- E-Print:
- 15 pages, 5 figures, accepted to ApJ Letters