分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiao-Hang Luan
Zhen-Zhao Tao
Hai-Chen Zhao
Bo-Lun Huang
Shi-Yu Li
Cong Liu
Hong-Feng Wang
Wen-Fei Liu
Tong-Jie Zhang
Vishal Gajjar
Dan Werthimer
摘要： 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, and propose a new search mode based on the MBCM which we call MBCM blind search mode. In our recent 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 and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Xiao-Hang Luan
Zhen-Zhao Tao
Hai-Chen Zhao
Bo-Lun Huang
Shi-Yu Li
Cong Liu
Hong-Feng Wang
Wen-Fei Liu
Tong-Jie Zhang
Vishal Gajjar
Dan Werthimer
摘要： 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, and propose a new search mode based on the MBCM which we call MBCM blind search mode. In our recent 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 and our work provides a deeper understanding to the polarization analysis of extraterrestrial signals.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Jérôme Maire
Shelley A. Wright
Jamie Holder
David Anderson
Wystan Benbow
Aaron Brown
Maren Cosens
Gregory Foote
William F. Hanlon
Olivier Hervet
Paul Horowitz
Andrew W. Howard
Ryan Lee
Wei Liu
Rick Raffanti
Nicolas Rault-Wang
Remington P. S. Stone
Dan Werthimer
James Wiley
David A. Williams
摘要： Optical SETI (Search for Extraterrestrial Intelligence) instruments that can explore the very fast time domain, especially with large sky coverage, offer an opportunity for new discoveries that can complement multimessenger and time domain astrophysics. The Panoramic SETI experiment (PANOSETI) aims to observe optical transients with nanosecond to second duration over a wide field-of-view ($\thicksim$2,500 sq.deg.) by using two assemblies of tens of telescopes to reject spurious signals by coincidence detection. Three PANOSETI telescopes, connected to a White Rabbit timing network used to synchronize clocks at the nanosecond level, have been deployed at Lick Observatory on two sites separated by a distance of 677 meters to distinguish nearby light sources (such as Cherenkov light from particle showers in the Earth's atmosphere) from astrophysical sources at large distances. In parallel to this deployment, we present results obtained during four nights of simultaneous observations with the four 12-meter VERITAS gamma-ray telescopes and two PANOSETI telescopes at the Fred Lawrence Whipple Observatory. We report PANOSETI's first detection of astrophysical gamma rays, comprising three events with energies in the range between $\thicksim$15 TeV and $\thicksim$50 TeV. These were emitted by the Crab Nebula, and identified as gamma rays using joint VERITAS observations.
分类： 天文学 >> 天文学 提交时间： 2023-02-19
Wei Liu
Dan Werthimer
Ryan Lee
Franklin Antonio
Michael Aronson
Aaron Brown
Frank Drake
Andrew Howard
Paul Horowitz
Jerome Maire
Rick Raffanti
Remington Stone
Richard Treffers
Shelley A. Wright
摘要： The PANOSETI experiment is an all-sky, all-the-time visible search for nanosecond to millisecond time-scale transients. The experiment will deploy observatory domes at several sites, each dome containing ~45 telescopes and covering ~4,440 square degrees. Here we describe the focal-plane electronics for the visible wavelength telescopes, each of which contains a Mother Board and four Quadrant Boards. On each quadrant board, 256 silicon photomultiplier (SiPM) photon detectors are arranged to measure pulse heights to search for nanosecond time-scale pulses. To simultaneously examine pulse widths over a large range of time scales (nanoseconds to milliseconds), the instrument implements both a Continuous Imaging Mode (CI-Mode) and a Pulse Height Mode (PH-Mode). Precise timing is implemented in the gateware with the White Rabbit protocol.
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