Letter to the Editor

Angular beaming and giant subpulses in the Crab pulsar

¹ Institute of Astronomy, University of Zielona Góra, Lubuska 2, 65-265, Zielona Góra, Poland e-mail: jag@astro.ia.uz.zgora.pl
² Department of Physics, University of Nevada Las Vegas, Las Vegas, NV 89154, USA
³ Abastumani Astrophysical Observatory, Al. Kazbegi ave. 2a, Tbilisi 0160, Georgia

Received: 13 December 2004
Accepted: 1 February 2005

Abstract

We propose that the extremely high brightness of the giant ultra-short subpulses observed in the Crab pulsar is consistent with the angular beaming due to relativistic motion of radiating sources along dipolar magnetic field lines. We argue that the effect of kinematic boosting inherently associated with localized relativistic sources results in apparent shortening and, in consequence, brightening of the emitted impulses. Thus we suggest that the giant subpulses are intrinsically many orders of magnitude less bright and powerful than they appear when interpreted within a temporal modulation model.