Megachannel Extraterrestrial Assay Candidates: No Transmissions from Intrinsically Steady Sources

Abstract

This paper reports new, more sensitive observations of nine of the eleven extrastatistical signals in the Megachannel Extraterrestrial Assay (META). These extrastatistical signals had all of the expected characteristics of extraterrestrial transmissions, except that they did not repeat. Cordes, Lazio, & Sagan (1997) showed that this lack of repeatability could be explained by interstellar scintillation of intrinsically steady sources. We use their methodology and our observations to exclude the scintillation hypothesis at a confidence level of at least 97.8% (for the case of an intrinsically weak source) to a level in excess of 99% (if the source strengths are comparable to that favored by Cordes, Lazio, & Sagan 1997). We also demonstrate that gravitational microlensing cannot account for the initial detection of these candidates nor is microlensing likely to play a role in future SETI programs. We conclude that the META candidates do not reflect a large population of powerful beacons.