γ Rays of 0.3–30 MeV from PSR0833–45

Abstract

Pulsed γ rays from the Vela pulsar PSR0833–45 are reported here for the first time at the medium energies, E, of 0.3–30 MeV. They were observed with the University of California, Riverside double scatter γ-ray telescope¹ flown on a balloon from Alice Springs, Australia, on 10 November 1981, 31 days after a large glitch in the pulsar period. The first and second pulses were detected from single scatters in the top scintillators, S1, at energies >0.3 MeV with statistical significances of 1.6σ and 1.6σ (together 2σ), and hy double scatters from all detector cell pairs at energies of 1–30 MeV with significances of 4.8σ and 3.8σ (together 5.8σ). The phase separation of the two pulses is 0.43±0.02 at the same absolute phases previously found by SAS 2 ² and COS B ³ for E>35 MeV. The energy distribution with six points from 0.3 to 30 MeV appears to bend away from the COS B power law⁴ at the lower energies and is well below the HEAO 1 ⁵ upper limits.