The gamma ray line of 44Ti, combined with radio observations, as a probe of supernovae

Abstract The decay of 44 Ti can be used to search for young Galactic supernova remnants (SNRs). While these objects may be hidden in obscured regions toward the inner Galaxy not accessible to optical telescopes, observations at both gamma ray and radio wavelengths can be used to discover and explore these objects. The OSSE instrument on the Compton Gamma Ray Observatory can observe the gamma ray lines accompanying 44 Ti 44 Sc 44 Ca decay, especially the 1.16 MeV line, and detect recent supernovae (SNe) with ages up to several centuries. Centimeter wavelength radio continuum observations can then be used to identify the young SNRs associated with the gamma-ray detections. The radio observations provide information on the interaction of the SN blast wave with the progenitor star's circumstellar environment and local ISM, together with information on the expansion velocity and small scale structure of young SNRs. The determination of the radio morphology of young SNRs, whose SN type can be inferred from the gamma-ray observations, provides valuable insight into the interpretation of existing radio observations of older SNRs.