Event Details

What are the thousands of X-ray emitting point sources in the center of the Milky Way?

Kaya Mori

Columbia University
Feb 20, 2018

MSI Seminar

MSI Conference Room

The Nuclear Spectroscopic Telescope Array (NuSTAR), carrying the first focusing telescopes capable of making sub-arcminute resolution images above 10 keV, conducted a deep survey of the Galactic Center region. One of our primary goals was to identify the origin of the ~9,000 unidentified X-ray sources detected by Chandra in the central ~100 pc of our Galaxy. As a result, NuSTAR discovered the diffuse, central hard X-ray emission (CHXE) over a ~10 pc region centered on the supermassive black hole Sgr A* and detected 70 hard X-ray sources above 10 keV. The CHXE and most of the NuSTAR point sources were attributed to a class of highly magnetized white dwarf binaries called intermediate polars. Their hard X-ray emission (kT ~ 30 keV), in contrast to the softer X-ray emission (kT ~ 15 keV) in the Galactic Ridge detected by Suzaku and INTEGRAL, suggests distinct X-ray source populations between the Galactic Center and Ridge. In the central parsec, NuSTAR detected four X-ray transients including a new magnetar SGR J1745-2900. Our NuSTAR spectral and timing analysis of two new Swift-discovered X-ray transients in 2016 suggests they were outbursting black hole binaries. In addition to an overabundance of transient X-ray binaries observed by Swift and NuSTAR, I present a remarkable cluster of quiescent X-ray binaries in the central parsec, identified with Chandra, and whose properties, numbers and distribution indicate the presence of the long-sought black hole cusp. Throughout my talk, I will present our current understanding of the X-ray source populations in the Galactic Center based on the recent results from NuSTAR, Chandra and other X-ray telescopes.