Abstract
Although supernova explosions are widely thought to give rise to cosmic rays (nucleons), there is, as yet, no direct evidence from individual objects to support this view. A possible tool in this respect is the detection of ..gamma..-rays emitted by supernova remnants (SNRs) via ..pi../sup 0/ decay. However, the accumulating ..gamma..-ray data show that SNRs as a class are not ..gamma..-ray sources, but rather that ..gamma..-ray sources are, in general, closely linked with young objects. We examine, among other possibilities, whether a restricted class of SNRs are actually ..gamma..-ray sources; we restrict the class to those SNRs physically linked with extreme Population I objects. Spatial coincidences between SNRs and OB associations or H II regions (SNOBs) are sought by various methods, and this yields a list of about 30 objects (which is certainly incomplete). From the Cos B data, one finds that five (perhaps six) out of 11 as yet unidentified ..gamma..-ray sources (above 100 MeV) are associated with SNOBs, and there is a hint that as much as three-fourths of the best identified SNOBs are seen in ..gamma..-rays. The associated probabilities of chance coincidence are approx.10/sup -4/. Angular and other statistical considerations also support this association. Pending confirmation, ifmore » a substantial proportion of the observed ..gamma..-rays does come from ..pi../sup 0/ decay, SNOBs appear to be a major source of galactic cosmic rays, in which cosmic-ray (> or =2 GeV) energy densities in the range approx.10--100 times the solar neighborhood value are found. Cosmic rays are produced by a two-step process, in which low-energy (MeV range) particles are injected by young stars pertaining to an OB association, and are subsequently accelerated by the shock wave of a neighboring supernova explosion. The case of ''isolated'' SNRs, the possible links with light-element production, further observational tests, and the links between SNOBs and other astronomical objects are discussed.« less
Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
