We’ve completed our analysis of 8 hours of Green Bank Telescope observations of “interstellar visitor” ‘Oumuamua. Billions of channels, covering the frequency range 1 – 12 GHz, were scanned, over an entire rotation of the object.
A search for narrow-band signals ruled out transmitters ten times as faint as a typical cellphone — an impressive demonstration of Listen’s capabilities, given that ‘Oumuamua was 350 million kilometers from Earth at the time of the observations! You can read the paper at https://arxiv.org/abs/1801.02814.