Discovery of new SNR candidates in the Galactic Center region with ASCA and Chandra

Senda, A.1, Murakami, H.2, and Koyama, K.1

1 Kyoto University, Sakyo-ku, Kyoto 606-8502, Japan
2 ISAS, Sagamihara, Kanagawa 229-8510, Japan

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See: ApJ, 565, 1017 (2002)

We report the result of Chandra observations of X-ray diffuse structures which are possible SNR candidates located within 100 pc of the Galactic Center. With its superior spatial resolution, Chandra revealed that the diffuse X-rays distribute clumpier than observed with ASCA. From a lot of newly discovered clumps, we picked up some of them which are likely to be SNRs and analized them in detail.

G0.570-0.018 has a small (40'' diameter) shell like morphology and shows a strong Fe K-line emission. Electron temperature is as high as 6 keV and the hot plasma is in a state of NEI (Non Equiliblium of Ionization). These features suggest that G0.570-0.018 is a quite young (t~100 year) SNR. About 5' south of Sgr A East, we also found an diffuse X-ray excess from the SNR. X-ray spectrum is thermal and the excess coincides with that the shell-type feature observed with radio continuum, which is attributable to a new SNR G359.92-0.09 (e.g. Coil & Ho 2000). An X-ray emission from the ``wisp'' is also detected, which is interacting with a molecular cloud M-0.13-0.08 (Ho et al. 1985). In addition, we newly discovered some X-ray clumps around (l, b)=(359.8, -0.25). Their X-ray spectra are thermal (kT~1 keV) and clearly show atomic line features such as Silicon, Sulfur, Argon and Calcium.

The origin of the Galactic Center hot plasma is an open issue over a decade. Young SNRs such as G0.570-0.018 could be attributable to the hot component of the GC plasma, while relatively low temperature (~1 keV) clumps, which also may be SNRs, could explain the cool component of the GC plasma.