Michael A. Garrett - SETI: Near & Far with Breakthrough Listen and the GBT

Abstract: The Breakthrough Listen (BL) Initiative has embarked on a comprehensive SETI survey of nearby stars in the Milky Way that is vastly superior to previous efforts as measured by a wide range of different metrics. However, SETI surveys using large radio telescopes such as the GBT, traditionally ignore the fact that single-dishes are sensitive to many other objects in the field of view - these include, both foreground and background galactic stars but also relatively nearby galaxies, galaxy groups and galaxy clusters, not to mention many different types of astrophysical exotica. In short, SETI surveys often place stronger limits on the prevalence of extraterrestrial than is often fully recognised. Taking this onboard, I will present an extended analysis of the GBT BL survey data, to place much tighter constraints on (i) the prevalence of powerful, high-duty cycle extraterrestrial radio transmitters in the Milky Way (Wlodarczyk-Sroka, Garrett, & Siemion 2020) and (ii) the luminosity function of potential extragalactic extraterrestrial radio transmitters (Garrett & Siemion 2022).