Search for Linear Polarization in Gamma-Ray Sources: Possible Evidence for the VELA Pulsar

Abstract

The use of the azimuthal distribution of planes containing e(+)/e(-) pairs from high-energy photon materialization to investigate the nature of gamma-ray sources is discussed. Analytical work done on COS B data for bright COS B sources (Vela, Crab, and Geminga) and for a reference background region is presented along with results which are indicative of a low-chance-probability anisotropy effect for Vela. The case for the Vela pulsar is studied in more detail, starting from its pulsation properties and from a polarization interpretation of the observed anisotropy. A possible physical interpretation of the results is given in the context of pulsar gamma-ray emission, and requirements for future gamma-ray telescopes derived from COS B experience are examined.