SIMBAD references

We present a method which can be used to reduce greatly the otherwise prohibitive computation effort needed for gamma-ray pulsar searches. A pulsar's frequency has never been discovered from γ-ray data because of the sparse data and long observation times. The excellent sensitivity of the EGRET instrument on the Compton Gamma Ray Observatory offers a solution. For strong sources, it is possible to split an observation into smaller time intervals and retain a detectable signal. Frequency searches on the separate intervals accumulate fewer trials because the need to search for a frequency derivative can be eliminated. We suggest an `evolutionary' method in which the trials are further reduced by testing data only at those frequencies which have given some indication of periodicity in all previous data intervals. For a typical two-week EGRET dataset, the method reduces the total number of trials by a factor of more than 10² and the computation time by a factor of 10³. The evolutionary technique is applied to the now known X-ray and γ-ray pulsar Geminga and is shown to identify the correct spin parameters.