The High Energy X-ray Probe (HEX-P): resolving the nature of Sgr A* flares, compact object binaries, ultra-relativistic cosmic-rays and particle accelerators in the Galactic Center

HEX-P is a probe-class mission concept that will combine high spatial resolution X-ray imaging (< 10′′ FWHM) and broad spectral coverage (0.2–80 keV) with a sensitivity far superior to current facilities (including XMM-Newton and NuSTAR). These capabilities will enable revolutionary new insights into a variety of important astrophysical problems. We present scientific objectives and simulations of HEX-P observations of the Galactic Center (GC) and Bulge. We demonstrate the unique and powerful capabilities of the HEX-P observatory for studying both X-ray point sources and diffuse X-ray emission. HEX-P will be uniquely equipped to explore a variety of major topics in Galactic astrophysics, allowing us to (1) investigate broad-band X-ray properties of X-ray flares emitted from the supermassive black hole (BH) at Sgr A* and probe the associated particle acceleration and emission mechanisms; (2) determine the distribution of compact object binaries in the nuclear star cluster and the composition of the Galactic Ridge X-ray emission; (3) identify hard X-ray sources detected by NuSTAR and determine X-ray point source populations in different regions and luminosity ranges; (4) measure white dwarf (WD) masses of magnetic CVs for deeply understanding the CV evolution and the origin of WD magnetic fields; (5) identify X-ray transients and measure fundamental parameters such as BH spins; (6) search for BH-OB binaries in young star clusters; (7) explore primary particle accelerators in the GC in synergy with the future TeV and neutrino observatories; (8) resolve cosmic-ray distributions through observing non-thermal X-ray filaments; (9) explore past X-ray outbursts from Sgr A* through X-ray reflection components from giant molecular clouds in the GC.