Radio SETI Observations of the Interstellar Object ‘Oumuamua

Motivated by the hypothesis that ‘Oumuamua could conceivably be an interstellar probe, we used the Allen Telescope Array to search for radio transmissions that would indicate a non-natural origin for this object. Observations were made at radio frequencies between 1-10 GHz using the Array’s correlator receiver with a channel bandwidth of 100 kHz. In frequency regions not corrupted by man-made interference, we find no signal flux with frequency-dependent lower limits of 0.01 Jy at 1 GHz and 0.1 Jy at 7 GHz. For a putative isotropic transmitter on the object, these limits correspond to transmitter powers of 30 mW and 300 mW, respectively.

In frequency ranges that are heavily utilized for satellite communications, our sensitivity to weak signals is badly impinged, but we can still place an upper limit of 10 W for a transmitter on the asteroid. For comparison and validation should a transmitter be discovered, contemporaneous measurements were made on the solar system asteroids uz2017 and wc2017 with comparable sensitivities. Because they are closer to Earth, we place upper limits on transmitter power to be 0.1 and 0.001 times the limits for ‘Oumuamua.

A concurrent set of observations over the same frequency range were made with a narrow-band (1 Hz) beamformer/spectrometer. Setting a 6.5 sigma threshold, the (frequency dependent) sensitivity limits on ‘Oumuamua were in the range 175 +/- 25 Jy into a 1 Hz bin. This rules out 1 Hz transmitters on ‘Oumuamua, 2017uz, and 2017wc to less than 500 mW, 50 mW, and 0.5 mW respectively over the frequency range from 1-10 GHz.

G. R. Harp, Jon Richards, Peter Jenniskens, Seth Shostak, J. C. Tarter
(Submitted on 28 Aug 2018)

Comments:    10 pages, 5 figures, submitted to Astrophysical Journal
Subjects:    Earth and Planetary Astrophysics (astro-ph.EP)
Cite as:    arXiv:1808.09355 [astro-ph.EP](or arXiv:1808.09355v1 [astro-ph.EP] for this version)
Submission history
From: Gerald Harp Ph.D.
[v1] Tue, 28 Aug 2018 15:24:16 GMT (645kb)
https://arxiv.org/abs/1808.09355
Astrobiology
SETI