A Technosignature Follow-Up Search for Two Kepler Planets with the Allen Telescope Array
Abstract
One strategy in the search for life beyond Earth is to look for narrowband radio technosignatures from extraterrestrial intelligences (ETIs). If we assume that these radio signals are being intentionally broadcasted, they might be found in astronomical "Schelling Points": for example, in unique places in the galaxy, timed with astronomical events, or at "magic" frequencies. As periodic signals detectable at interstellar distances, planetary transits may be a good Schelling Point for signal coordination. In Sheikh et al. 2022 (in prep), 12 Kepler planets were observed during their transits with the Green Bank Telescope and analyzed for potential technosignatures. No technosignatures were found, but two signals-of-interest had a degeneracy between transience and localization, which warranted follow-up. In this project, we re-observed these two Kepler planets (Kepler-1332b and Kepler-842b) during their transits. Observations were performed with the Allen Telescope Array (ATA) beamformer during the transit times obtained from the NASA Exoplanet Archive Transit Prediction tool. We obtained 2-beam (one on-target, one a few beamwidths away) high spectral-resolution filterbank data (~1 Hz, ~15 seconds) for 30 minutes including the exoplanet's mid-transit point, at central frequencies of 1.5 and 8 GHz simultaneously. So far, we have obtained two observations of Kepler-842b, but have not yet observed Kepler-1332b. We used the Breakthrough Listen turboSETI pipeline to do a narrowband signal search using a signal-to-noise ratio of 5 and a minimum drift rate of 4 Hz/s, which revealed 7340 and 4376 hits, respectively. We then filtered the hits to exclude any signal which appeared in both the on- and the off-beam, and obtained a total of 2385 events from the first observations and 1221 events for the second. We then visually inspected all 3606 events as waterfall plots and found that all of them could be explained by radio frequency interference (RFI). Given our null results from Kepler-842b, we conclude that there were no technosignature detections from Kepler-842b in the observed frequency range, for a transmitter Effective Isotropic Radiated Power (EIRP) ~51 times Arecibo's capabilities. We will perform the same analysis for Kepler-1332b during its upcoming transit. Even though no technosignatures were discovered, this project provides a proof-of-concept for signal follow-up with the ATA, and shows the strength of beamforming as an RFI-rejection method.
- Publication:
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American Astronomical Society Meeting Abstracts
- Pub Date:
- January 2023
- Bibcode:
- 2023AAS...24136302A