Fortuitous Observations of Potential Stellar Relay Probe Positions with GBT

Recent theoretical and observational works have investigated the possibility that extraterrestrial intelligence could use the Sun as a gravitational lens in order to aid communication across interstellar distances. Unlike other targeted SETI searches where the drift rate of any artificial extraterrestrial signals may be unknown up to some large upper limit, the drift rates of any solar system relay probes would be known and set only by the motion of the Earth. One recent work used purpose-designed Green Bank Telescope (GBT) observations to search for signals from a hypothetical communications probe several hundred astronomical unit from the Sun at the antipode of the α Centauri AB system. To further aid in the advancement of relay-probe searches, we present a table of 1764 archival GBT observations which fortuitously fall near the positions of hypothetical probes communicating with stars within 100 pc and compute the drift rates for these probes.