Radio continuum and Hi observations of the supernova remnant G296.8–00.3

Abstract

We present Australia Telescope Compact Array (ATCA) observations of the supernova remnant (SNR) G296.8-00.3. A 1.3-GHz continuum image shows the remnant to have a complex multi-shelled appearance, with an unusual rectangular strip running through its centre. HI absorption yields a kinematic distance to the remnant of 9.6+/-0.6 kpc, from which we estimate an age in the range (2-10) x 10^3 yr. The ATCA's continuum mode allows a measurement of the Faraday rotation across the band, from which we derive a mean rotation measure towards the SNR of 430 rad m^(-2). We consider possible explanations for the morphology of G296.8-00.3, and conclude that it either has a biannular structure, as might be produced through interaction with an asymmetric progenitor wind, or that its appearance is caused by the effects of the surrounding interstellar medium. We argue that the adjacent pulsar J1157-6224 is at a similar distance as the SNR, but that a physical association is highly unlikely. The pulsar is the only detectable source in the field in circular polarization, suggesting a method for finding pulsars during aperture synthesis.