No sign of G2s encounter affecting Sgr A*s X-ray flaring rate from $Chandra$ observations


Abstract in English

An unusual object, G2, had its pericenter passage around Sgr A*, the $4times10^6$ M$_odot$ supermassive black hole in the Galactic Centre, in Summer 2014. Several research teams have reported evidence that following G2s pericenter encounter the rate of Sgr A*s bright X-ray flares increased significantly. Our analysis carefully treats varying flux contamination from a nearby magnetic neutron star and is free from complications induced by using data from multiple X-ray observatories with different spatial resolutions. We test the scenario of an increased bright X-ray flaring rate using a massive dataset from the textit{Chandra X-ray Observatory}, the only X-ray instrument that can spatially distinguish between Sgr A* and the nearby Galactic Centre magnetar throughout the full extended period encompassing G2s encounter with Sgr A*. We use X-ray data from the 3 Ms observations of the textit{Chandra} textit{X-ray Visionary Program} (XVP) in 2012 as well as an additional 1.5 Ms of observations up to 2018. We use detected flares to make distributions of flare properties. Using simulations of X-ray flares accounting for important factors such as the different $Chandra$ instrument modes, we test the null hypothesis on Sgr A*s bright (or any flare category) X-ray flaring rate around different potential change points. In contrast to previous studies, our results are consistent with the null hypothesis; the same model parameters produce distributions consistent with the observed ones around any plausible change point.

Download