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Dynamic modeling of the X-ray emission and accretion flow in the Galactic center via colliding stellar winds

Published onJun 01, 2020
Dynamic modeling of the X-ray emission and accretion flow in the Galactic center via colliding stellar winds

The Galactic center is a prime candidate for studying the Bondi-radius/parsec-size flow of matter towards a supermassive black hole (SMBH) due to our ability to resolve the sources that are continually injecting material into this region. Hydrodynamic simulations of the inner parsec's dominant injection source — the stellar winds of ~25 Wolf-Rayet stars orbiting the SMBH Sgr A* — reproduce not only the inferred accretion rate down to a radius of 0.1pc, but also the diffuse X-ray emission seen by the Chandra X-ray Observatory in terms of flux level and spectral shape. This indicates that the X-ray emission in the region of comparison (a 2–5 arcsec annulus centered on the SMBH) is from Wolf-Rayet wind collisions. Two sets of more recent simulations, one that includes the 65 OB stellar winds and the other that shows an accretion disk similar to that recently reported in ALMA observations, show the same intriguing difference with the earlier work: the X-ray emission centered on Sgr A* is notably reduced. This is important for rectifying how the modeled colliding-wind emission and the unmodeled X-rays produced much nearer to Sgr A* itself via its radiatively inefficient accretion flow (RIAF) sum together to produce the observed, quiescent X-ray properties in line of sight with Sgr A*. We will present our newer simulations, their synthesized X-ray emission, and additional constraints we can derive on the RIAF through comparisons with Chandra observations.

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