The Use of Gamma‐Ray Bursts as Direction and Time Markers in SETI Strategies

When transmitting a signal over a large distance it is more efficient to senda brief beamed signal than a continuous omni-directional transmission but thisrequires that the receiver knows where and when to look for the transmission.For SETI, the use of various natural phenomena has previously been suggested toachieve the desired synchronization. Here it is proposed that gamma-ray burstsmay well the best ``synchronizers'' of all currently known phenomena due totheir large intrinsic luminosities, high occurrence rate, isotropic skydistribution, large distance from the Galaxy, short duration, and easydetectability. For targeted searches, precise positions for gamma-ray burstsare required together with precise distance measurements to a target star. Therequired burst position determinations are now starting to be obtained, aidedin large part by the discovery of optical afterglows. Good distancemeasurements are currently available from Hipparcos and even bettermeasurements should be provided by spacecraft now being developed. Fornon-targeted searches, positional accuracies simply better than a detector'sfield of view may suffice but the time delay between the detection of agamma-ray burst and the reception of the transmitted signal cannot be predictedin an obvious way.Comment: 8 pages, accepted for publication in PAS