A Search for Periodic Emissions at the Wow Locale

The Ohio State University Radio Observatory recorded a strong, narrowband emission near the 21 cm hydrogen line in 1977 during a search for extraterrestrial intelligence, an event known as the ‘‘Wow ’’ signal. The few independent attempts to replicate the detection have failed. We have investigated the possibility of a periodic source—perhaps rotating and illuminating us once each cycle of many hours, like a lighthouse— which prior observations would have been unlikely to detect. We used the University of Tasmania Hobart 26 m radio telescope to search for intermittent and possibly periodic emissions at the Wow locale by tracking the apparent source positions for nearly 14 hr continuously on multiple days. No emissions resembling the Wow were detected over a bandwidth of 2.5 MHz to a flux density limit of about 18 Jy, with a detection threshold of 5.9 and rms noise of 3 Jy. We conclude that the Wow was not due to a source within our flux density limits and repeating more often than every 14 hr, although the possibility of a longer period or nonperiodic source cannot be ruled out. Subject headings: extraterrestrial intelligence — radio lines: general