Gamma-ray sources, supernova remnants, OB associations, and the origin of cosmic rays

Journal Article · Sun Jul 01 04:00:00 EDT 1979 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/157166· OSTI ID:5929658

Montmerle, T

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, if 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.

• Research Organization: Section d'Astrophysique, Centre d'Etudes Nucleaires de Saclay, France
• OSTI ID: 5929658
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 231:1; ISSN ASJOA
• Country of Publication: United States
• Language: English

Related Subjects

640101 -- Astrophysics & Cosmology-- Cosmic Radiation
640103* -- Astrophysics & Cosmology-- Quasi-Stellar
Radio
& X-Ray Sources-- (-1987)
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
BOSONS
COSMIC GAMMA SOURCES
COSMIC NUCLEI
COSMIC RADIATION
COSMIC RADIO SOURCES
COSMIC RAY SOURCES
ELECTROMAGNETIC RADIATION
ELEMENTARY PARTICLES
GAMMA RADIATION
H2 REGIONS
HADRONS
IONIZING RADIATIONS
MESONS
NUCLEI
ORIGIN
PIONS
PIONS NEUTRAL
PSEUDOSCALAR MESONS
RADIATIONS
SHOCK WAVES
STAR CLUSTERS
SUPERNOVA REMNANTS