Exploring physics of rotation powered pulsars with sub-10 GeV imaging atmospheric Cherenkov telescopes

Abstract We discuss the potential of future sub-10 GeV threshold imaging atmospheric Cherenkov telescope arrays for exploring the physics of rotation powered pulsars and their interactions with the ambient medium through relativistic winds and termination shocks. One such telescope is the high-altitude concept called ‘5@5’ recently suggested by Aharonian [APh 5 (2001) 335]. 5@5, with its enormous detection area exceeding 10 4 m 2 at the threshold energy of about 5 GeV, combines two distinct features of the current satellite-borne (large photon fluxes at GeV energies) and ground-based (large detection areas at TeV energies) γ-ray astronomies. Such an instrument would allow comprehensive studies of temporal and spectral characteristics of γ-ray pulsars in the crucial 5 to 30 GeV energy interval. An equally important topic in the program of pulsar studies by 5@5 would be the search for GeV γ-radiation from other radio pulsars at a few mVela level. Finally, the searches for pulsed radiation components in the spectra of a large fraction of unidentified EGRET sources (suspected to be pulsars) without invoking information from lower (radio, optical, X-ray) frequency domains, seems to be another important issue, because the periodic signals at lower energies could be significantly suppressed in many cases. The detection rate of γ-rays from ‘standard’ EGRET sources by 5@5 is expected to exceed ten events per one second. This should provide an adequate photon statistics for the search for periodic signals at the flux level of 3 mVela within the observation time of 3 h or so (a time resolution below which any change of a signal’s phase can be ignored). The spectral coverage by 5@5 and its flux sensitivity are nicely suited for studying other aspects of pulsar physics and astrophysics, in particular for detecting unshocked relativistic pulsar winds, as well as for quantifying characteristics of pulsar driven synchrotron nebulae through the inverse Compton radiation at energies between several GeV and several 100 GeV. The Vela pulsar, the brightest γ-ray source on the sky, is an ideal laboratory for practical realization of these unique observational possibilities.