BLC1 (Breakthrough Listen Candidate 1).
documentedscientific_anomalySETI & Technosignatures
Narrowband ~982 MHz signal toward Proxima Centauri (Parkes 2019, reported 2020); after ~2 years attributed to terrestrial radio-frequency interference.
Detected during 2019 Parkes observations of Proxima Centauri and reported Dec 2020, BLC1 was a pure narrowband tone with a drifting frequency — superficially technosignature-like. A technosignature verification framework (Nature Astronomy, 2021) found dozens of similar RFI signals at frequencies harmonically related to clock oscillators and concluded it was an intermodulation product of local interferers, not ETI. A textbook example of SETI's discipline that alien origin is the hypothesis of last resort.