NuSTAR Discoverty of a 40 keV High-energy X-ray Source within the Central Parsec of the Galaxy

Soft X-ray observations have revealed that The central parsec of the Galaxy harbors a supermassive black hole, a pulsar wind nebula candidate, a cusp of quiescent black hole systems and complicated diffuse X-ray emission components. NuSTAR's arcminte spatial resolution beyond 10 keV allowed us to investigate what the Galactic center has to offer in the high-energy X-ray band. In this talk, I would like to report our discovery of a new High-energy X-ray source located at merely 1 parsec from the Galactic center supermassive black hole Sgr A*. This source is most significantly detected as an extended source in 40-50 keV. It spatially coincides with a region showing velocity discontinuum of the slighted ionized gas in the circumnuclear disk. I am going to discuss two possible origins of this high-energy source in the vicinity of Sgr A*: 1) ionization of the circumnuclear disk by X-ray photon outflows from Sgr A* or a nearby pulsar wind nebula; 2) excitation of the circumnuclear disk by MeV-GeV electrons/protons.