Galactic Ridge X-ray Emission study with NuSTAR

The paradigm of the Galactic Ridge X-ray Emission (GRXE) or hard X-ray background of the Milky Way has been dramatically changed over the past years. The stellar origin of the GRXE has been strongly supported by morphological and spectral studies with RXTE, INTEGRAL and Chandra observatories. The GRXE does not arise from the interaction of cosmic rays with the interstellar medium, as was believed before, but is associated with the (predominantly old) stellar population of the Galaxy, namely with hard X-ray emission from accreting white dwarfs and coronaly active stars. I will present results of the GRXE spectral study with NuSTAR hard X-ray mission launched into the orbit in 2012. The GRXE measurements have been done in a part of the Galactic Center survey program 2012-2014. New data allow us to reconstruct both GRXE spatial distribution and broadband (3-80 keV) spectrum, providing another test for its interpretation.