Orateur
Description
The search for extraterrestrial intelligence (SETI) is to search for technosignatures associated with extraterrestrial life, such as engineered radio signals. In this paper, we apply the multibeam coincidence matching (MBCM) strategy (see for more details: https://iopscience.iop.org/article/10.3847/1538-3881/ac8bd5, AJ, 164 (2022) 4, 160) and propose a new search mode based on the MBCM which we call the MBCM blind search mode (see for more details: https://iopscience.iop.org/article/10.3847/1538-3881/acb706, AJ, 165 (2023) 3, 132). In our targeted SETI research, 33 exoplanet systems are observed by the Five-hundred-meter Aperture Spherical radio Telescope (FAST). With this blind search mode, we search for narrowband drifting signals across 1.05–1.45 GHz in two orthogonal linear polarization directions separately. There are two special signals, one of which can only be detected by the blind search mode while the other can be found by both blind and targeted search modes. This result reveals huge advantages of the new blind search mode. However, we eliminate the possibility of the special signals being ETI signals based on much evidence, such as the polarization, drift, frequency, and beam coverage characteristics. Our observations achieve an unprecedented sensitivity because the minimum equivalent isotropic radiated power we are able to detect reaches 1.48 × 109 W. In addition, our work provides a deeper understanding of the polarization strategy for analyzing extraterrestrial signals. The polarization strategy involves, on the one hand, analyzing the intensity of the polarization channels of the signals, and on the other hand, studying the variation of the intensity over time, so as to determine the origin of the signals (see for more details: https://iopscience.iop.org/article/10.3847/1538-3881/ad0be8, AJ, 167 (2023) 1, 8). As the most sensitive single-dish radio telescope in the L-band, FAST will conduct more SETI observations in the future, including targeted searches and commensal sky surveys. Although SETI with FAST is challenged by more types of weak RFI, we will identify and classify more types of RFI and discover new search methods to remove RFIs effectively.
