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

TL;DR

This study used the Allen Telescope Array to search for extraterrestrial radio technosignatures from interstellar object 3I/ATLAS, resulting in no detections but setting upper limits on possible signals.

Contribution

First comprehensive radio technosignature search targeting 3I/ATLAS with a new pipeline, establishing upper limits on potential alien signals.

Findings

Detected nearly 74 million narrowband signals but none of extraterrestrial origin.

Filtered data to 211 candidate signals, all of which were false positives.

Set upper limits of 10-110 W on radio technosignatures from 3I/ATLAS.

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 bliss. We then blanked hits by frequency and drift rate to mitigate radio frequency interference in our dataset, narrowing the dataset down to ~2 million hits. These hits were further filtered by the localization code 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 upper limit of 10-110 W on radio technosignatures from 3I/ATLAS across the frequency and drift rate ranges covered by our survey.