2002A&A...393..511D

We investigate the role of rotational effects in inducing asymmetry present above ∼5GeV in the double-peak lightcurves of the bright EGRET pulsars: Vela, Crab, and Geminga. According to Thompson (2001, AIP Conf. Proc., 558, 103), the trailing peak dominates over the leading peak above ∼5GeV consistently for all three pulsars, even though this is not the case over the entire energy range of EGRET, i.e. above ∼100MeV. We present the results of Monte Carlo simulations of electromagnetic cascades in a pulsar magnetosphere within a single-polar-cap scenario with rotationally-induced propagation effects of the order of β (where β is the dimensionless local corotation velocity). We find that even in the case of nearly aligned rotators with spin periods of P∼0.1s rotation may lead to asymmetric (with respect to the magnetic axis) magnetic photon absorption which in turn leads to asymmetric gamma-ray pulse profiles. The resulting features - softer spectrum of the leading peak and the dominance of the trailing peak above ∼5GeV - agree qualitatively with the EGRET data of the bright gamma-ray pulsars.