PSPC Observation of the Composite Supernova Remnant 3C391
Abstract
We report preliminary results of a 24 ks ROSAT PSPC observation of the supernova remnant 3C391 (G31.9+0.0). The PSPC image reveals centrally concentrated X-ray emission inside the radio shell, while Einstein IPC observation (Wang & Seward 1984, ApJ) was not able to determine whether the SNR is shell-like or center-filled. The northwestern part has a strong radio shell and weak central X-ray emission. In contrast, the southeastern part has strong central X-ray emission and weak radio emission. The X-ray image is largely circular and slightly extended outside the radio shell in southwestern direction. The PSPC spectra alone give similarly good fits using one-temperature thermal model with N_H = 1.9 times 10(22) cm(-2) and kT = 1.1 keV and with N_H = 1.5 times 10(22) cm(-2) and kT = 2.30 keV. This bimodality in PSPC fit contours has been noted elsewhere (Bregman & Pildis 1992, ApJL; Rho et al. 1994, ApJ). However, the fit combining PSPC and IPC yields a best fit of N_H = 1.8 (+1.0}_{-0.2) times 10(22) cm(-2) and kT = 1.13(+0.7}_{-0.6) keV, which rules out the higher temperature fit. There are large spectral variations between the northwestern and southeastern parts of the remnant: either the northwestern part has higher N_H or the southeastern part has lower temperature. But the PSPC data can not determine one or the other. When assuming constant temperature across the remnant, the difference in N_H is large enough to state that the low X-ray surface brightness in the northwestern part is due to the absorption. When assuming constant N_H, the northwestern emission shows higher temperature and pressure than the southeastern part. The interpretation of the southeastern radio and X-ray emission representing a ``breakout'' from the northwestern main shell, will be discussed.
- Publication:
-
American Astronomical Society Meeting Abstracts
- Pub Date:
- December 1994
- Bibcode:
- 1994AAS...185.6203R