GAMMA-RAY PULSAR STUDIES WITH COMPTEL

Since the launch of the Compton Gamma-Ray Observatory (CGRO) the numbe r of detected gamma-ray pulsars increased from two to six. COMPTEL, on -board CGRO and sensitive to gamma-rays with energies between approxim ately 0.7 and 30 MeV, detected three of these unambiguously. The class ical Crab and Vela pulsars have been observed on several occasions and detailed pulse patterns and spectral parameters have been derived. Th e new CGRO gamma-ray pulsar PSR B1 509-58 has been detected by COMPTEL at a significance level above 4 sigma, consistently in a timing and s patial analysis. A likely detection of Geminga has been obtained at a approximately 3 sigma level. This indication is found in a phase inter val in which COS B data showed the presence of a new variable componen t, Interpeak 2, exhibiting a very soft spectrum above 50 MeV. The dive rsities in light-curve shapes and spectral distributions, the apparent time variabilities, and the significant differences in the fractions of the spin-down power radiated at gamma-ray energies in this small sa mple of gamma-ray pulsars pose important constraints to pulsar modelin g.