Discovery Of New SNR Candidates in the Galactic Center Region withASCA andChandra

Abstract

We report the discovery of diffuse X-ray features which are possible SNR candidates near the Galactic Center (GC) observed with ACSA and Chandra G0.570–0.018 has extremely small (20″ diameter) shell-like morphology. Its X-ray spectrum exhibits strong Fe-K line emission and is well fitted by an NEI model with a temperature of about 6 keV. These characteristics suggest that G0.570–0.018 is a quite young (t∼ 100 year) SNR. Diffuse hard X-rays were also detected from G359.92–0.09. Its X-ray spectrum also exhibits strong Fe-K line emission. The X-ray excess coincides with the shell-type feature observed in the radio continuum (e.g., Ho et al. 1985), which is attributable to a new SNR. In addition, we have discovered several soft X-ray clumps. Their X-ray spectra are thermal (kT ∼ 1 keV) and clearly show atomic line features such as Si, S, Ar and Ca. The origin of the diffuse X-ray emission from the GC region has been an unresolved issue for over a decade. Hard clumps such as G0.570–0.018 are likely to be young/middle-aged SNRs, and could produce the hot component of the GC plasma, while relatively soft (∼1 keV) clumps, which also may be SNRs, could contribute to the cool component of the GC plasma.