X‐Ray Emission from Multiphase Shock in the Large Magellanic Cloud Supernova Remnant N49

Abstract

The supernova remnant (SNR) N49 in the Large Magellanic Cloud hasbeen observed with the Advanced CCD Imaging Spectrometer (ACIS) onboard the Chandra X-Ray Observatory. The superb angular resolutionof the Chandra/ACIS images resolves a point source, the likely X-raycounterpart of soft gamma-ray repeater SGR 0526-66, and the diffuselaments and knots across the SNR. These filamentary features representthe blast wave sweeping through the ambient interstellar medium andnearby dense molecular clouds. We detect metal-rich ejecta beyondthe main blast wave shock boundary in the southwest of the SNR, whichappear to be explosion fragments, or bullets, ejected from the progenitorstar. The detection of strong H-like Si line emission in the easternside of the SNR requires multiphase shocks in order to describe theobserved X-ray spectrum, whereas such a multiphase plasma is notevident in the western side. This complex spectral structure of N49suggests that the postshock regions toward the east of the SNR mighthave been reheated by the reverse shock off the dense molecular cloudswhile the blast wave shock front has decelerated as it propagatesinto the dense clouds. The X-ray spectrum of the detected pointlikesource is continuum-dominated and can be described with a power lawof Gammasimilar to3. This provides a confirmation that this pointlikeX-ray source is the counterpart of SGR 0526-66 in the quiescent state.