A radio continuum study of the Magellanic Clouds VI. Discrete sources common to radio and X-ray surveys of the Magellanic Clouds

By comparing Parkes telescope radio surveys with the X-ray ROSAT All-Sky Survey (RASS) we have found 71 discrete sources of both radio and X-ray emission in the Large Magellanic Cloud (LMC). These 71 sources are mainly supernova remnants (SNRs) and SNR candidates (36), and background sources (27). For six of the sources we have no proposed identification and the other two are H II regions. A source-intensity comparison of the radio and X-ray sources shows very little correlation, but we note that the strongest SNRs at both radio and X-ray frequencies are young SNRs from Population I. Six new LMC SNR candidates are proposed. From the radio flux density of the SNRs we have estimated the SNR birth rate to be one every 100 (+/-20) yr and the star-formation rate (SFR) to be 0.7 (+/-0.2) M. yr(-1). A similar comparison was undertaken for the Small Magellanic Cloud (SMC), but instead of the RASS we used a roster of pointed observations made with the ROSAT Position Sensitive Proportional Counter (PSPC). This comparison resulted in 27 sources in common between the Parkes radio and ROSAT PSPC surveys. Two new SMC sources are proposed for SNR candidates. The SMC SNR birth rate was estimated to be one every 350 (+/-70) yr and the SFR was estimated to be 0.15 (+/-0.05) M. yr(-1).