A Study Of The X-ray Emission From The Galactic Center

X-ray observations of the Galactic Center(GC),in particular those afforded by the Chandra X-ray Observatory,provide a unique way to trace stellar populations and study high-energy activities in the GC.The investigation of the GC X-ray emission is com-posed of two parts:i)We present an updated catalog of X-ray point sources in the inner 500."(?20 pc)of the GC,where the nuclear star cluster(NSC)stands,based on a total of 4.5 Ms of Chandra observations taken from 1999 September to 2013 April.A total of 3619 sources are detected in the 2-8 keV band,among which?3500 are probable GC sources and?1300 are new identifications.We explore their global source proper-ties,including long-term variability,cumulative spectra,luminosity function,and spa-tial distribution.Based on the equivalent width and relative strength of the iron lines,we suggest that in addition to the arguably predominant population of magnetic cat-aclysmic variables(CVs),non-magnetic CVs contribute substantially to the detected sources,especially in the lower-luminosity group.ii)We have investigated the linear X-ray filament,G359.944-0.052,previously identified as a likely X-ray counterpart of a parsec-scale jet from the Galactic Center super-massive black hole(SMBH),Sagittar-ius A*(Sgr A*),using a total of?5.6 Ms ultra-deep Chandra observations taken from September 1999 to July 2017.We find no flux or spectral variation in G359.944-0.052 after the G2 periapsis passage around early 2014,however,a moderate flux increase of?2? significance might be associated with the periapsis passage of G1 in early 2001.The filament exhibits an unusually hard spectrum(photon-index ?1)in its portion clos-est to Sgr A*(i.e.,n ear-side)and a significant spectral softening in the more distant portion,which can be interpreted as synchrotron cooling of the relativistic electrons moving along the jet path.In particular,the hard spectrum of the near-side suggests a piling up of quasi-monoenergetic electrons caused by rapid radiative cooling.The spectral and temporal properties of G359.944-0.052 strengthen the case of it being the X-ray counterpart of a jet launched by Sgr A*.