Pulsar observations above 1 GeV with future ground-based gamma-ray telescopes

Abstract

This paper explores the potential of present and future ground based gamma-ray telescopes to detect GeV to multi-GeV pulsed emission from EGRET pulsars. Five types of telescopes can in principle detect such emission: The two most promising are (1) the "5@5" stereo array (5 telescopes, each with a diameter of 20 m; proposed site: Chile, 5 km a.s.l.); (2) a single 30 meter dish at a conventional altitude (e.g. 2.2 km). These two detectors (in the conceptual phase) should be able to detect pulsed GeV emission with a few seconds, but may not realize before the launch of GLAST. Pre-GLAST results are however expected from experiments under construction: (3) MAGIC (17 m single dish, La Palma) and (4) H.E.S.S. (four 11 m diameter dishes, Namibia). (5) Existing solar type arrays: CELESTE (France - in operation) and STACEE (USA - in operation). To date no confirmed pulsed gamma-ray emission from radio pulsars has been seen from any ground-based gamma-ray telescope. In the case of the solar-type arrays, a clever triggering technique may reveal the spectral tail of the pulsed gamma-ray emission from pulsars such as Crab and PSR B1951+32, but more luck is expected from the MAGIC and H.E.S.S. type arrays. This paper compares the pulsed rates and detection times required for MAGIC, H.E.S.S., and "5@5" given the trigger studies performed upto date. The performance of any of these telescopes is conservatively optimized if we employ the polar cap model for pulsed emission showing super exponential cutoffs between 5 GeV (Vela and Geminga) and 40 GeV (no cutoff was seen by EGRET up to 30 GeV for PSR B1951+32 and PSR B1706+44.