"Signal" search for intelligence in the galactic nucleus with the array of the Lowlands

In August, 1981, the Westerbork Synthesis Radio Telescope was used for 4 h to search for narrowband pulsing radio beacons in the direction of the Galactic Center. By using both the spatial discrimination and temporal stability available to an interferometric measurement, weak intermittent signals can be detected even in the face of the strong, naturally caused radiation from this region. A radio beacon within our bandwidth, centered on the 21 cm neutral hydrogen line, would be recognizable if it had a repetition period between 40 sec and 1/2 h. The rms sensitivity to point sources was approximately 50 mJy/cycle, and the detection limit was 500 mJy/cycle. The limit degrades for pulse widths < 0.02s. No repetitive signals were found. For a swept, narrow-band radio beacon constrained to the Galactic Disk (beamwidth = 0.02 rad), our detection limit corresponds to a transmitter power of 10(11) MW at the Galactic Center.