The pulse shape and the spectrum of PSR B0531+21 (Crab pulsar) in the low-energy rays observed with FIGARO II

The FIGARO II experiment observed the Crab pulsar in the energy range 0.15-4 MeV during two transmediterranean flights, on 1990 July 9 and on 1986 July 11. A detailed analysis of the pulse profiles shows that the profile in the energy band 0.37-0.51 MeV is characterized, in addition to the main ones, by the presence in the Interpeak region of two other peaks, which could be associated with the 0.44 MeV line reported by Massaro et al. (1991). Spectral analysis confirms that the Ip spectrum, harder than those of P1 and P2, should progressively steepen with increasing energy. We conclude that the observed Crab emission can be due to the superposition of two components and that the one dominant in the Ip is associated with the pair production in the magnetosphere.