High‐Energy Gamma‐Ray Observations of Two Young, Energetic Radio Pulsars

We present results of Compton Gamma-Ray Observatory EGRET observations of theunidentified high-energy gamma-ray sources 2EG J1049-5847 (GEV J1047-5840, 3EGJ1048-5840) and 2EG J1103-6106 (3EG J1102-6103). These sources are spatiallycoincident with the young, energetic radio pulsars PSRs B1046-58 andJ1105-6107, respectively. We find evidence for an association between PSRB1046-58 and 2EG J1049-5847. The gamma-ray pulse profile, obtained by foldingtime-tagged photons having energies above 400 MeV using contemporaneous radioephemerides, has probability of arising by chance of 1.2E-4 according to thebinning-independent H-test. A spatial analysis of the on-pulse photons revealsa point source of equivalent significance 10.2 sigma. Off-pulse, thesignificance drops to 5.8 sigma. Archival ASCA data show that the only hardX-ray point source in the 95% confidence error box of the gamma-ray source isspatially coincident with the pulsar within the 1' uncertainty (Pivovaroff,Kaspi & Gotthelf 1999). The double peaked gamma-ray pulse morphology andleading radio pulse are similar to those seen for other gamma-ray pulsars andare well-explained in models in which the gamma-ray emission is produced incharge-depleted gaps in the outer magnetosphere. The inferred pulsed gamma-rayflux above 400 MeV, (2.5 +/- 0.6) x 10E-10 erg/cm^2/s, represents 0.011 +/-0.003 of the pulsar's spin-down luminosity, for a distance of 3 kpc and 1 srbeaming. For PSR J1105-6107, light curves obtained by folding EGRET photonsusing contemporaneous radio ephemerides show no significant features. Weconclude that this pulsar converts less than 0.014 of its spin-down luminosityinto E > 100 MeV gamma-rays beaming in our direction (99% confidence), assuminga distance of 7 kpc, 1 sr beaming and a duty cycle of 0.5.Comment: Accepted for publication in the Astrophysical Journa