We present new stringent upper limits to a redshifted e± annihilation radiation line from the Crab pulsar. These upper limits are based on OSSE observations that were optimized for the 400-500 keV range. We have searched for the emission over several different phase intervals of the pulsar light curve. We find no evidence for the redshifted emission at 440 keV reported by the FIGARO team. The typical 3 σ upper limit to phase-averaged flux (i.e., the net flux from the pulsar averaged over the entire light curve) is about 2 × 10-5 photons cm-2 s-1. This value is about a factor of 4 lower than the 3 σ flux reported by the FIGARO team. This result places significant new constraints on some models in which positrons are flowing down toward the surface of the Crab pulsar.
- Gamma rays: theory
- Pulsars: individual (Crab pulsar)
ASJC Scopus subject areas
- Astronomy and Astrophysics
- Space and Planetary Science