The S2 star as a probe of the accretion disk of Sgr A*

Abstract

How accretion proceeds around the massive black hole in the Galactic center and other highly sub-Eddington accretors remains poorly understood. The orbit of the S2 star in the Galactic center passes through the accretion disk of the massive black hole and any observational signature from such interaction may be used as an accretion probe. Because of its early stellar type, S2 is expected to possess a fairly powerful wind. We show here that the ram pressure of the accretion disk shocks the stellar wind fairly close to the star. The shocked fluid reaches a temperature of ~ 1 keV and cools efficiently through optically thin, thermal bremsstrahlung emission. The radiation from the shocked wind peaks around the epoch of the pericenter passage of the star at a luminosity potentially comparable to the quiescent emission detected from Sgr A*. Detection of shocked wind radiation can constrain the density of the accretion disk at a distance of several thousands of gravitational radii from the black hole.

5 pages, 1 figure, submitted to MNRAS

References in corpus (5)

• GRMHD Simulations of Magnetized Advection Dominated Accretion on a Non-Spinning Black Hole: Role of Outflows
• An Unambiguous Detection of Faraday Rotation in Sagittarius A*
• On the nature of the fast moving star S2 in the Galactic Center
• New observations of the gas cloud G2 in the Galactic Center
• Radio Synchrotron Emission from a Bow Shock around the Gas Cloud G2 Heading toward the Galactic Center

Cited by in corpus (12)

• The Black Hole Accretion Code
• Non-Thermal Electron Acceleration in Low Mach Number Collisionless Shocks. I. Particle Energy Spectra and Acceleration Mechanism
• Hydrodynamic Simulations of the Inner Accretion Flow of Sagittarius A* Fueled By Stellar Winds
• Plasmoid formation in global GRMHD simulations and AGN flares
• Observations of Sagittarius A* during the pericenter passage of the G2 object with MAGIC
• Radio Synchrotron Emission from the Bow Shock of G2
• Modelling Accretion Disk and Stellar Wind Interactions: the Case of Sgr A*
• Constraining the accretion flow density profile near Sgr A* using the $L^{\prime }$-band emission of the S2 star
• The formation and stability of a cold disc made out of stellar winds in the Galactic Centre
• Detecting Stars at the Galactic Centre via Synchrotron Emission
• Simulating the pericentre passage of the Galactic centre star S2
• Flares from Galactic centre pulsars: a new class of X-ray transients?