X-ray observation of very high energy gamma-ray source, HESS J1745-303, with Suzaku

Abstract

Suzaku observations of a TeV unidentified source, HESS J1745-303, are presented. A possible excess of neutral iron line emission is discovered, and is likely associated with the main part of HESS J1745-303, named "region A." It may be an X-ray reflection nebula where the X-rays from previous Galactic center (GC) activity are reflected by a molecular cloud. This result further strengthens the assumption that the molecular cloud, which is spatially coincident with region A of HESS J1745-303, is located in the GC region. The TeV emission from molecular clouds is reminiscent of the diffuse TeV gamma rays from the GC giant molecular clouds, and it could have the same emission mechanism. With deep exposure mapping observations by Suzaku, a tight upper limit on the 2-10 keV continuum diffuse emission from region A is obtained as 2.1 × 10-13 erg s-1 cm-2. The flux ratio between 1-10 TeV and 2-10 keV is larger than 4. Possible scenarios to reproduce wide-band spectra from keV to TeV are examined. Thermal X-rays from nearby two old supernova remnants, G359.0-0.9 and G359.1-0.5, are detected, and their emission properties are well determined in the present study with deep exposure. © 2009. The American Astronomical Society. All rights reserved..