A Search for Radio-quiet Gamma-ray Pulsars

Most Galactic point sources of gamma rays remain unidentiÐed. The few (extrasolar) sources that have been identiÐed are all young, rotation-powered pulsars, all but one of which were identiÐed using radio ephemerides. The radio-quiet Geminga pulsar was identiÐed only after pulsations were discovered in a coincident X-ray source. Observational evidence indicates that many of the unidentiÐed Galactic sources are likely to be pulsars, and some theoretical models predict a potentially large population of radio-quiet gamma-ray pulsars. We present a new method for performing sensitive gamma-ray pulsar searches. We used this method to search several of the strongest EGRET sources for pulsations. This was a blind search for new pulsars, covering a frequency and a frequency-derivative phase space large enough to detect Crab-like pulsars as well as lower frequency, high magnetic Ðeld ““ magnetars.ÏÏ No new pulsars were discovered, and we report upper limits constraining the characteristics of any signals contained in the data sets searched. Subject headings : gamma rays : observations È pulsars : general