RX J0852.0-4622: Another nonthermal shell-type supernova remnant (G266.2-1.2)

The newly discovered supernova remnant G266.2-1.2 (RX J0852.0-4622), along the line of sight to the Vela supernova remnant (SNR), was observed with ASCA for 120 ks. We find that the X-ray spectrum is featureless and well described by a power law, extending to three of the class of shell-type SNRs dominated by nonthermal X-ray emission. Like G347.3-0.5, this low-latitude remnant displays discrete regions of enhanced emission along the rim as well as faint nonthermal emission from the interior. We derive limits on the thermal content of the remnant emission, although the presence of the Vela SNR compromises our ability to seriously constrain a low-temperature component. Limits placed on the amount of Sc-K emission are compared with the expected flux based on the reported Ti-44 emission from G266.2-1.2. We also report on an unresolved X-ray source surrounded by diffuse emission near the center of the remnant. The properties of the source are not well determined but appear consistent with the interpretation that the source is a neutron star surrounded by a synchrotron nebula. Alternatively, the source may be associated with one of two stars located within the positional error circle, but this appears somewhat unlikely.