XMM-Newton Observations of G32.45+0.1and G38.55+0.0: diffuse hard X-ray sources found with the ASCA Galactic Plane Survey

Original · EN

We report on XMM-Newton observations of G32.45+0.1 and G38.55+0.0. These were discovered as diffuse hard X-ray sources with the ASCA Galactic plane survey, but the limited spatial resolution of ASCA could not conclude whether these are truly diffuse or a group of unresolved point-sources. XMM-Newton, with higher spatial resolution than ASCA, confirmed that G32.45+0.1 has a diffuse shell-like structure with a radius of 4'. The spectrum shows featureless continuum, hence can be fitted with a power-law model of Gamma 2.2 with an absorption of Nₕ 5.2*10²²cm⁻². From this Nₕ value, we estimate the distance to G32.45+0.1 to be 17kpc, then the luminosity (in the 0.5-10.0keV band) and radius of the shell are 9.5*10³⁴ergs/s and 20pc, respectively. The radio complex sources in the NRAO/VLA Sky Survey (NVSS; 1.4GHz) are globally associated to the X-ray shell of G32.45+0.1. Therefore G32.45+0.1 is likely to be a synchrotron dominant shell-like SNR. No significant diffuse structure was found in the XMM-Newton image of another ASCA diffuse source G38.55+0.0. The upper limit of the observed flux (0.5-10.0keV) is estimated to be 9.0*10⁻¹³ergs/cm²/s being consistent with the ASCA result.