TeV lightcurve of PSR B1259-63/SS2883

The inverse Compton scattering of ultrarelativistic electrons accelerated at the pulsar wind termination shock is believed to be responsible for TeV gamma-ray signal recently reported from the binary system PSR B1259-63/SS2883. While this process can explain the energy spectrum of the observed TeV emission, the detected gamma-ray fluxes do not agree with the published theoretical predictions of the TeV lightcurve. The main objective of this paper is to show that the HESS results can be explained, under certain reasonable assumptions, by inverse Compton scenarios of gamma-ray production in the system. In this paper we study evolution of the energy spectra of relativistic electrons under different assumptions about the acceleration and energy-loss rates of electrons, and the impact of these processes on the lightcurve of IC gamma-rays. We demonstrate that the observed TeV lightcurve can be explained (i) by adiabatic losses which dominate over the entire trajectory of the pulsar with a significant increase towards the periastron, or (ii) by the sub-TeV cutoffs in the energy spectra of electrons due to the enhanced rate of Compton losses close to the periastron. The Compton deceleration of the pulsar wind contributes to the decrease of the nonthermal power released in the accelerated electrons, and thus to the reduction of the IC and synchrotron components of radiation close to the periastron. Although this effect alone cannot explain the observed lightcurves, the Comptonization of the pulsar wind leads to the formation of gamma-radiation with a line-type energy spectrum. While the HESS data already constrain the Lorentz factor of the wind, $\Gamma \le 10^6$, future observations of this object with GLAST should allow a deep probe of the wind Lorentz factor in the range between $10^4$ and $10^6$.