A Possible Rossby Wave Instability Origin for the Flares in Sagittarius A*

Abstract

In recent years, near-IR and X-ray flares have been detected from the Galaxy's central radio point source, Sagittarius A* (Sgr A*), believed to be a \~3.10^6 solar masses supermassive black hole. In some cases, the transient emission appears to be modulated with a (quasi-)periodic oscillation (QPO) of ~ 17-20 minutes. The implied ~ 3 r_S size of the emitter (where r_S = 2GM/c^2 is the Schwarzschild radius) points to an instability - possibly induced by accretion - near the Marginally Stable Orbit (MSO) of a slowly spinning object. But Sgr A* is not accreting via a large, `standard' disk; instead, the low density environment surrounding it apparently feeds the black hole with low angular momentum clumps of plasma that circularize within ~ 10-300 r_S and merge onto a compact, hot disk. In this Letter, we follow the evolution of the disk following such an event, and show that a Rossby wave instability, particularly in its magnetohydrodynamic (MHD) form, grows rapidly and produces a period of enhanced accretion lasting several hours. Both the amplitude of this response, and its duration, match the observed flare characteristics rather well.

arXiv commentAccepted for publication in ApJ Letters

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• Sgr A* flares: tidal disruption of asteroids and planets?
• NuSTAR detection of high-energy X-ray emission and rapid variability from Sagittarius A* flares
• Distinguishing black holes and wormholes with orbiting hot spots
• Rossby Wave Instability in three dimensional discs
• Near infrared flares of Sagittarius A*: Importance of near infrared polarimetry
• The X-ray flaring properties of Sgr A* during six years of monitoring with Swift
• MHD Simulations of Accretion onto Sgr A*: Quiescent Fluctuations, Outbursts, and Quasi-Periodicity
• On the orientation of the Sagittarius A* system
• Rossby Wave Instability in Astrophysical Discs
• Rossby Wave Instability with Self-Gravity
• The pattern of accretion flow onto Sgr A*
• Periodic Modulations in an X-ray Flare from Sagittarius A*
• Testing the No-Hair Theorem with Observations of Black Holes in the Electromagnetic Spectrum
• A Testable the Stochastic Acceleration Model for Flares in Sagittarius A*
• General Relativistic Flux Modulations from Disk Instabilities in Sagittarius A*
• The origin of hotspots around Sgr A*: Orbital or pattern motion?
• Statistics of X-ray flares of Sagittarius A*: evidence for solar-like self-organized criticality phenomenon
• Exploring plasma evolution during Sagittarius A* flares
• Magnetic reconnection plasmoid model for Sagittarius A* flares
• How strong are the Rossby vortices?
• A magnetohydrodynamic model for multi-wavelength flares from Sagittarius~A${}^{\star }$ (I): model and the near-infrared and X-ray flares
• Sagittarius A* High Energy X-ray Flare Properties During NuSTAR Monitoring of the Galactic Center from 2012 to 2015
• Testing the nature of the supermassive black hole candidate in SgrA* with light curves and images of hot spots
• Sixteen years of X-ray monitoring of Sagittarius A*: Evidence for a decay of the faint flaring rate from 2013 August, 13 months before a rise in the bright flaring rate
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• Using infrared/X-ray flare statistics to probe the emission regions near the event horizon of Sgr A*
• Modelling Accretion Disk and Stellar Wind Interactions: the Case of Sgr A*
• Submillimeter Quasi-Periodic Oscillations in Magnetically Choked Accretion Flows Models of Sgr A*
• Distinguishing an ejected blob from alternative flare models at the Galactic centre with GRAVITY
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• Prospects for multi-messenger extended emission from core-collapse supernovae in the Local Universe
• Soft gamma-ray constraints on a bright flare from the Galactic Center supermassive black hole
• A microquasar classification from a disk instability perspective
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• Modulated X-ray Emissivity near the Stress Edge in Sgr A*
• Correlation between Flux and Spectral Index during Flares in Sagittarius A*
• Broadband extended emission in gravitational waves from core-collapse supernovae
• On the Rossby Wave Instability in accretion discs surrounding spinning black holes
• Low angular momentum flow model of Sgr A* activity
• Rossby Wave Instability and High-Frequency Quasi-Periodic Oscillations in accretion discs orbiting around black holes
• Rossby Vortices in Thin Magnetized Accretion Discs
• Polarimetric Imaging of Sgr A* in its Flaring State
• Flares from spiral waves by lensing and time-delay amplification?
• Sagittarius A* near-infrared flares polarization as a probe of space-time I: Non-rotating exotic compact objects