A search for radio-quiet gamma-ray pulsars in the EGRET data

We are searching for radio-quiet gamma-ray pulsars among the brightest unidentified EGRET point sources. This investigation utilizes the computational resources of the Center for Advanced Computing Research at Caltech to compute Gigapoint power spectra. Multiple frequency derivatives are searched by accelerating event times before computing the Fourier transform. We demonstrate that such a search detects the pulsation of radio-quiet Geminga with 10^-12 significance directly from 6 days of EGRET data. The remaining unidentified EGRET sources have substantially less signal to noise to support a periodicity search, but can be detected with ∼3 weeks of exposure if the pulsar lightcurve has sufficient harmonic content. Only upper limits have been obtained to date. We demonstrate that the error in transforming EGRET event times to the solar system barycenter caused by the inaccuracy of the EGRET position results in a detection at a frequency and frequency derivative different from the true values, but harmonic power is not lost.