A search for VHE gamma rays from the Crab Pulsar-Nebula at the Haleakala Gamma Ray Observatory
Abstract
The Haleakala Gamma Ray Observatory, a fast-timing air shower detector utilizing the Atmospheric Cerenkov Technique to search for High Energy Gamma Rays from point sources, observed the Crab Pulsar-Nebula for $\sim$240 hours from August, 1989 through January, 1991. This data has been analyzed for long-term and burst steady-state (DC) emission, and for both continuous and sporadic pulsed emission at the 33 ms frequency of the Crab pulsar, both prior to and after data selection. It was discovered that half of the data should be rejected as a result of systematic problems on one of the two instruments. The remaining data comprised two operating modes, one of which was less sensitive to ambient light and had greater sensitivity to air showers than the other. After allowing for effects due to possible accidental triggers, analysis yielded a 6.4$\sigma$ excess of continuous nonpulsed emission for the instrument when operated in the more sensitive mode. The steady-state flux is estimated to be $Flux \approx (2.5 \pm 0.4) \times 10\sp{-10}\ \gamma\ {\rm cm\sp{-2}s\sp{-1}}$ above 300 GeV. This flux is a factor of $\sim$2 greater than that expected using the spectrum above 400 GeV obtained by the Whipple collaboration. DC analysis after data reduction failed to improve the signal to background, as was predicted by simulations. No conclusive evidence for emission at the Crab pulsar frequency was found in this data set.
Degree
Ph.D.
Advisors
Gaidos, Purdue University.
Subject Area
Astronomy|Astrophysics|Particle physics
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