A Search for Radio Technosignatures from Interstellar Object 3I/ATLAS with the Allen Telescope Array (2512.18142v1)

Abstract: In 2025 July, the third-ever interstellar object, 3I/ATLAS, was discovered on its ingress into the Solar System. Similar to the NASA Voyager missions sent in 1977, science probes by extraterrestrial life (artifact ``technosignatures'') could be sent to explore other stellar systems like our own. In this campaign, we used the SETI Institute's Allen Telescope Array to observe 3I/ATLAS from 1--9~GHz. We detected nearly 74 million narrowband hits in 7.25~hr of data using the newly-developed search pipeline \texttt{bliss}. We then applied blanking in frequency and drift rate to mitigate Radio Frequency Interference (RFI) in our dataset, narrowing the dataset down to $\sim$2 million hits. These hits were further filtered by the localization code \texttt{NBeamAnalysis}, and the remaining 211 hits were visually inspected in the time-frequency domain. We did not find any signals worthy of additional follow-up. Accounting for the Doppler drift correction and given the non-detection, we are able to set an Effective Isotropic Radiated Power (EIRP) upper limit of $10-110$~W on radio technosignatures from 3I/ATLAS across the frequency and drift rate ranges covered by our survey.