Guang-Yuan Song

The Five-hundred-meter Aperture Spherical Telescope (FAST) is the world’s largest single-dish radio telescope, and the search for extraterrestrial intelligence (SETI) is one of its five key science objectives. We conducted a targeted search for unresolved narrowband radio technosignatures toward the TRAPPIST-1 system using FAST. The observations consisted of five independent L -band pointings, each with a 20 minute integration, for a total on-source time of 1.67 hr. The frequency coverage spanned 1.05–1.45 GHz with a spectral resolution of ∼7.5 Hz. We searched Stokes I (total intensity) data for drifting signals with Doppler drift rates within ±20 Hz s ⁻¹ and a signal-to-noise ratio threshold of S/N = 10. For unresolved, minimally drifting narrowband signals, the nominal minimum detectable equivalent isotropic radiated power is EIRP min ≈ 1.44 × 1 0 10 W . We explicitly quantify how this limit degrades at high drift rates because of tree de-Doppler power smearing, reaching ≈3.84 × 10 ¹¹ W at ∣ ν ̇ ∣ = 20 Hz s − 1 under a conservative peak-channel sensitivity correction. No credible technosignature candidates attributable to the TRAPPIST-1 system were identified within the searched parameter space. Nevertheless, TRAPPIST-1 remains a compelling target for future SETI efforts. We plan to extend our search to other signal types, such as periodic, transient, broadband, and propagation-broadened transmitters, and to carry out broader surveys of nearby exoplanetary systems with FAST.

The Five-hundred-meter Aperture Spherical Telescope (FAST) is the world's largest single-dish radio telescope, and the search for extraterrestrial intelligence (SETI) is one of its five key science objectives. We conducted a targeted narrowband search toward the TRAPPIST-1 system using FAST. The observations consisted of five independent L-band pointings, each with a 20-minute integration, for a total on-source time of 1.67h. The frequency coverage spanned 1.05--1.45GHz with a spectral resolution of ~7.5Hz. We searched for narrowband drifting signals with Doppler drift rates within +_4Hz/s and a signal-to-noise ratio threshold of S/N>10 in two orthogonal linear polarizations separately.Based on the system parameters adopted in this work, we estimate a minimum detectable equivalent isotropic radiated power of 2.04x10^10W, placing one of the most stringent constraints to date on persistent or high-duty-cycle narrowband transmitters in this system. No credible technosignature candidates were identified within the searched parameter space. Nevertheless,TRAPPIST-1 remains a compelling target for future SETI efforts. We plan to extend our search to other signal types, such as periodic or transient transmitters, and to carry out broader surveys of nearby exoplanetary systems with FAST.