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Modelling the thermal X-ray emission around the Galactic centre from colliding Wolf-Rayet winds

Published online by Cambridge University Press:  09 February 2017

Christopher M. P. Russell ,
Q. Daniel Wang  and
Jorge Cuadra
Christopher M. P. Russell
Affiliation:
X-ray Astrophysics Laboratory, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA(NASA Postdoctoral Program Fellow, administered by USRA) email: crussell@udel.edu
Q. Daniel Wang
Affiliation:
Department of Astronomy, University of Massachusetts, Amherst, MA 01003, USA
Jorge Cuadra
Affiliation:
Instituto de Astrofísica, Facultad de Física, Pontificia Universidad Católica de Chile, 782-0436 Santiago, Chile
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Abstract

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The Galactic centre is a hotbed of astrophysical activity, with the injection of wind material from ~30 massive Wolf-Rayet (WR) stars orbiting within 12″ of the super-massive black hole (SMBH) playing an important role. Hydrodynamic simulations of such colliding and accreting winds produce a complex density and temperature structure of cold wind material shocking with the ambient medium, creating a large reservoir of hot, X-ray-emitting gas. This work aims to confront the 3Ms of Chandra X-ray Visionary Program (XVP) observations of this diffuse emission by computing the X-ray emission from these hydrodynamic simulations of the colliding WR winds, amid exploring a variety of SMBH feedback mechanisms. The major success of the model is that it reproduces the spectral shape from the 2″–5″ ring around the SMBH, where most of the stellar wind material that is ultimately captured by Sgr A* is shock-heated and thermalised. This naturally explains that the hot gas comes from colliding WR winds, and that the wind speeds of these stars are in general well constrained. The flux level of these spectra, as well as 12″×12″ images of 4–9 keV, show the X-ray flux is tied to the SMBH feedback strength; stronger feedback clears out more hot gas, thereby decreasing the thermal X-ray emission. The model in which Sgr A* produced an intermediate-strength outflow during the last few centuries best matches the observations to within about 10%, showing SMBH feedback is required to interpret the X-ray emission in this region.

Keywords

Galaxy: centrestars: Wolf-Rayetstars: windsoutflowsX-rays: starsradiative transferhydrodynamics
Type
Contributed Papers
Information
Proceedings of the International Astronomical Union , Volume 11 , Symposium S322: The Multi-Messenger Astrophysics of the Galactic Centre , July 2016 , pp. 39 - 42
Copyright
Copyright © International Astronomical Union 2017 

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