Coincidence of compact supernova remnants with three COS-B γ-ray sources

Abstract

POSITIONAL coincidences and a `near miss' of four small-diameter supernova remnants (SNR) with three of the 11 unidentified COS-B γ-ray sources¹ are reported here. I argue that it is unlikely that all four SNR-γ-ray source associations are accidental, and that their compactness probably indicates that their ages are not greater than about 10⁴ yr. Although these four SNR are not associated with known pulsars, the radio emission^2-4 in each case is centrally peaked which admits the possibility of a central pulsar. If these associations are physical the γ rays could originate from a remnant pulsar or could be due to cosmic ray interactions in the vicinity of the remnant⁵. The only two previously identified^6,7 and confirmed⁸ γ-ray sources are the Crab pulsar and the Vela pulsar ,both of which are associated with young (<~ 2×4 yr) SNR. In these two cases the γ-ray emission is predominantly pulsed and therefore comes directly from the remnant short-period pulsars.