Drift Rates of Narrowband Signals in Long-term SETI Observations for Exoplanets

The Doppler shift of a radio signal is caused by the relative motion between the transmitter and receiver. The change in frequency of the signal over time is called the drift rate. In the studies of radio search for extraterrestrial intelligence (SETI), extraterrestrial narrowband signals are expect...

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Bibliographic Details
Published in:The Astrophysical journal 2022-10, Vol.938 (1), p.1
Main Authors: Li, Jian-Kang, Zhao, Hai-Chen, Tao, Zhen-Zhao, Zhang, Tong-Jie, Xiao-Hui, Sun
Format: Article
Language:English
Subjects:
Astrophysics
Celestial mechanics
Doppler effect
Drift rate
Earth
Earth rotation
Extrasolar planets
Extraterrestrial intelligence
Extraterrestrial life
Narrowband
Orbits
Planetary rotation
Project SETI
Radio signals
Receivers & amplifiers
Red shift
Search for extraterrestrial intelligence
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Summary:The Doppler shift of a radio signal is caused by the relative motion between the transmitter and receiver. The change in frequency of the signal over time is called the drift rate. In the studies of radio search for extraterrestrial intelligence (SETI), extraterrestrial narrowband signals are expected to appear “chirped” since both the exoplanet and Earth are moving. Such planet rotation and orbital revolution around the central star can cause a nonzero drift rate. Other relative motions between the transmitter and receiver, such as the gravitational redshift and galactic potential, are negligible. In this paper, we mainly consider the common cases in which the drift rate is contributed by the rotations and orbits of Earth and the exoplanet in the celestial mechanics perspective, and we briefly discuss other cases different from the Earth–exoplanet one. We can obtain the expected pseudosinusoidal drifting result with long-term observations and shorter orbital periods of exoplanets. Exoplanets with higher orbital eccentricities can cause asymmetric drifting. The expected result should be intermittent pseudosinusoidal curves in long-term observations. The characteristics of pseudosinusoidal curves, as another new criterion for extraterrestrial signals, can be applied to long-term SETI reobservations in future research.
ISSN:0004-637X
1538-4357
DOI:10.3847/1538-4357/ac90bd