Dual-backend Multibeam Position-switching Targeted SETI Observations toward Nearby Active Planet-hosting Systems with FAST

Abstract The Five-hundred-meter Aperture Spherical Telescope (FAST), the world’s largest single-dish radio telescope, lists the search for extraterrestrial intelligence (SETI) as one of its key scientific objectives. In this work, we present a targeted SETI observation for seven nearby active stars utilizing the FAST L-band multibeam receiver, employing an observational strategy that combines position switching with multibeam tracking to balance on-source integration time with the accuracy of the beam response. Using both pulsar and SETI backends, we perform a comprehensive search for narrowband drifting signals with Doppler drift rates within diversified ranges and channel-width periodic signals with periods between 0.12 and 100 s and duty cycles between 10% and 50%. No credible radio technosignatures were detected from any of the target systems. Based on this null result, we place constraints on the presence of transmitters at a 95% confidence level, ruling out narrowband transmitters with EIRP above 3.98 × 10 8 W and periodic transmitters with EIRP above 1.80 × 10 10 W within the observation band.