ASCA Discovery of Diffuse 6.4 keV Emission near the Sagittarius C Complex: A New X‐Ray Reflection Nebula

Abstract

We present an ASCA discovery of diffuse hard X-ray emission from theSgr C complex with its peak in the vicinity of the molecular cloudcore. The X-ray spectrum is characterized by a strong 6.4 keV lineand large absorption. These properties suggest that Sgr C is a newX-ray reflection nebula that emits fluorescent and scattered X-raysvia irradiation from an external X-ray source. We found no adequatelybright source in the immediate Sgr C vicinity to fully account forthe fluorescence. The irradiating source may be the Galactic nucleusSgr A*, which was brighter in the past than it is now, as is suggestedfrom observations of the first X-ray reflection nebula Sgr B2.