The Breakthrough Listen Search for Intelligent Life: Searching for Technosignatures in Observations of TESS Targets of Interest

Abstract

Exoplanetary systems are prime targets for the Search for Extraterrestrial Intelligence (SETI). With the recent uptick in the identification of candidate and confirmed exoplanets through the work of missions like the Transiting Exoplanet Survey Satellite (TESS), we are beginning to understand that Earth-like planets are common. In this work, we extend the Breakthrough Listen (BL) search for extraterrestrial intelligence to include targeted searches of stars identified by TESS as potential exoplanet hosts. We report on 30 minute cadence observations collected for 28 targets selected from the TESS Input Catalog from among those identified as containing signatures of transiting planets. The targets were searched for narrowband signals from 1 to 11 GHz using the turboSETI pipeline architecture modified for compatibility with the Google Cloud environment. Data were searched for drift rates of ±4 Hz s−1 above a minimum signal-to-noise threshold of 10, following the parameters of previous searches conducted by Price et al. and Enriquez et al. The observations presented in this work establish some of the deepest limits to date over such a wide band (1–11 GHz) for life beyond Earth. We determine that fewer than 12.72% of the observed targets possess transmitters operating at these frequencies with an equivalent isotropic radiated power greater than our derived threshold of .

The Breakthrough Listen Search for Intelligent Life: Technosignature Search of Transiting TESS Targets of Interest

“…Given our lack of detection of any signal-of-interest, we can calculate the transmitter limit, or maximum percentage of TESS TOIs at each band that possess a detectable transmitter based on our search parameters. Price et al (2020), Traas et al (2021, and other authors, calculate this limit using a one sided 95% Poisson confidence interval with a 50% probability of actually observing a signal if the transmitter is present (Gehrels 1986). Given the small number of cadences observed at L-band, a binomial confidence interval is a better estimate for the transmitter limit in our case.…”

“…First, FindDoppler identifies narrow-band Doppler-drifting signals in the filterbank files. Following from Price et al (2020) and Traas et al (2021), we adopt a minimum 2 S/N threshold of 10, across a drift rate range of ±4 Hz s −1 . To maximize efficiency, we parallelized the processing across all 64 compute nodes available to BL at GBT, greatly reducing runtime for large amounts of data.…”

“…As of 2021 June, TESS has found 4,190 new exoplanets, including confirmed exoplanets and candidates, some of which may have suitable conditions for life. Traas et al (2021) recently performed a technosignature search of 28 TESS targets of interest (TOIs) using the L, S, C, and X-band receivers at the GBT. Transiting systems are prioritized because Earth is in the ecliptic for these systems.…”

“…Transiting systems are prioritized because Earth is in the ecliptic for these systems. An ETI may be more likely to send bright signals out in the direction of their ecliptic, either to intentionally signal observers who can see their transits, or for purposes such as interplanetary radar (Traas et al 2021).…”

“…We refine the search of Traas et al (2021) by selecting systems that were observed with the GBT during transits of candidate exoplanets, which may further improve the chance of receiving an extraterrestrial signal. An ETI may choose to broadcast signals towards their antistellar point, knowing that observers may be monitoring their system during a transit, so there is a higher likelihood of a transmission being received.…”