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 Moscibrodzka 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 submm VLBI 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.

15 pages, 5 figures, accepted to ApJ Letters

References in corpus (8)

• Event-horizon-scale structure in the supermassive black hole candidate at the Galactic Centre
• A gas cloud on its way towards the super-massive black hole in the Galactic Centre
• The Submillimeter Bump in Sgr A* from Relativistic MHD Simulations
• Simulating the Emission and Outflows from Accretion Disks
• The Submillimeter Polarization of Sgr A*
• Jet-lag in Sgr A*: What size and timing measurements tell us about the central black hole in the Milky Way
• Global GRMHD Simulations of Black Hole Accretion Flows: a Convergence Study
• Near-Infrared and X-ray Quasi-Periodic Oscillations in Numerical Models of Sgr A*

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• The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
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• Radio Synchrotron Emission from a Bow Shock around the Gas Cloud G2 Heading toward the Galactic Center
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• The Properties and Fate of the Galactic Center G2 Cloud
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• Multi-Epoch VERA Observations of Sagittarius A*: I. Images and Structural Variability
• No asymmetric outflows from Sagittarius A* during the pericenter passage of the gas cloud G2
• Probing spacetime around Sagittarius A* using modeled VLBI closure phases
• Multiple accretion events as a trigger for Sgr A* activity
• Multi-phase environment of compact galactic nuclei: the role of the Nuclear Star Cluster
• A Possible Time-Delayed Brightening of the Sgr A* Accretion Flow after the Pericenter Passage of G2 Cloud
• Reconstruction of Static Black Hole Images Using Simple Geometric Forms
• Long-term monitoring of Sgr A* at 7 mm with VERA and KaVA
• S0-2 star, G1- and G2-objects and flaring activity of the Milky Way's Galactic Center black hole in 2019
• Colliding with G2 near the Galactic Centre: a geometrical approach
• Theory of G2 Cloud Multi-Wavelength Emission