NuSTAR Galactic Center Survey
Abstract
During its 2-year baseline mission, the Nuclear Spectroscopic Array (NuSTAR) has carried out a survey of the Galactic Center region with total area coverage of ~0.7 deg2 and total exposure of ~2 Msec. The NuSTAR survey with ~40 ksec depth has detected over 30 point sources above 10 keV, including three known X-ray transients during their outbursts. Some of the NuSTAR point sources have remarkably hard X-ray spectra beyond 40 keV, indicating that they are either Intermediate Polars or X-ray binaries with neutron star or black hole. We will present our spectral and timing analysis to identify the hard X-ray sources. Deep Sgr A* observations with total exposure of ~400 ksec detected Sgr A* flares above 10 keV, and most remarkably NuSTAR's sub-arcminute images above 20 keV revealed previously undetected diffuse hard X-ray emission around Sgr A*. Hard X-ray emission above 40 keV is dominated by a point-like source that is spatially and spectroscopically consistent with the PWN candidate G359.95-0.04, a potential counterpart of the TeV source HESS J1745-290. In Sgr A and B2 region, NuSTAR has spatially resolved the molecular clouds for the first time above 10 keV, and broad-band X-ray spectroscopy was used to explore an origin of their X-ray emission, either due to low energy cosmic-ray heating and/or X-ray reflection of giant flares from Sgr A* in the past. We will also discuss NuSTAR detection of non-thermal X-ray filaments and implications for their emission mechanisms.
- Publication:
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American Astronomical Society Meeting Abstracts #225
- Pub Date:
- January 2015
- Bibcode:
- 2015AAS...22522201M