A 4–8 GHz Galactic Center Search for Periodic Technosignatures

Abstract

Radio searches for extraterrestrial intelligence have mainly targeted the discovery of narrowband continuous-wave beacons and artificially dispersed broadband bursts. Periodic pulse trains, in comparison to the above technosignature morphologies, offer an energetically efficient means of interstellar transmission. A rotating beacon at the Galactic Center (GC), in particular, would be highly advantageous for galaxy-wide communications. Here, we present blipss, a CPU-based open-source software that uses a fast folding algorithm (FFA) to uncover channel-wide periodic signals in radio dynamic spectra. Running blipss on 4.5 hr of 4–8 GHz data gathered with the Robert C. Byrd Green Bank Telescope, we searched the central 6 ′ of our galaxy for kHz-wide signals with periods between 11 and 100 s and duty cycles (δ) between 10% and 50%. Our searches, to our knowledge, constitute the first FFA exploration for periodic alien technosignatures. We report a nondetection of channel-wide periodic signals in our data. Thus, we constrain the abundance of 4–8 GHz extraterrestrial transmitters of kHz-wide periodic pulsed signals to fewer than one in about 600,000 stars at the GC above a 7σ equivalent isotropic radiated power of ≈2 × 1018 W at δ ≃ 10%. From an astrophysics standpoint, blipss, with its utilization of a per-channel FFA, can enable the discovery of signals with exotic radio frequency sweeps departing from the standard cold plasma dispersion law.

The Most Sensitive SETI Observations Toward Barnard's Star with FAST

“…This EIRP min is 7 times smaller than Green Bank Telescope observations of Barnard's star and 4.4 times smaller than Parkes Telescope observations of the closest star, Prox Cen (Smith et al 2021). Although, our observations find no solid evidence for 100%-duty cycle radio transmitters emitting between 1.05 and 1.45 GHz with an EIRP above 4.36 × 10 8 W. Barnard's star remains an interesting target for technosignature searches, and in the future, we will continue to observe it and search for more types of technical features such as periodic signals (Suresh et al 2023). And we will conduct SETI surveys of more nearby stars as well as exoplanetary magnitude systems with FAST.…”

A Proposal for Enhancing Technosignature Search toward the Galactic Center

“…The Galactic center is a cynosure place in the Milky Way, and the surface density of stars is highly enhanced around its sky position (Binney & Merrifield 1998). In consideration of these aspects, ETI signals have been searched around the direction of the Galactic center (Shostak & Tarter 1985;Worden et al 2017;Gajjar et al 2021;Tremblay et al 2022;Suresh et al 2023). Notably, in relation to the concurrent signaling scheme, the distance to the Galactic center (more preciously Sgr A * ) is measured at an exceptional accuracy despite its remoteness (GRAVITY Collaboration et al 2019, 2021.…”

“…Meanwhile, the Galactic center is a salient place in our island Universe (see, e.g., Binney & Merrifield 1998). Partly motivated by its specialty, ETI signals have indeed been searched around the direction of the Galactic center (Shostak & Tarter 1985;Worden et al 2017;Gajjar et al 2021;Tremblay et al 2022;Suresh et al 2023). Importantly, by observing nearly regular orbital motions of stars around the massive black hole there, we can determine the distance l H to the Galactic center at an exceptional precision, in spite of its remoteness ∼8.3 kpc (GRAVITY Collaboration et al 2019, 2021.…”

COSMIC: An Ethernet-based Commensal, Multimode Digital Backend on the Karl G. Jansky Very Large Array for the Search for Extraterrestrial Intelligence

“…Each signal form requires a different search approach, and multiple methodologies have been explored over the years. Many of these approaches and signal forms were discussed in Ekers et al (2002), but other techniques have been discussed since that time (i.e., Houston et al 2021;Luan et al 2023;Suresh et al 2023). However, publications on SETI have thus far placed a strong focus on drifting narrow frequency band (Hz-wide) signals (e.g., Enriquez et al 2017;Price et al 2020;Sheikh et al 2021;Ma et al 2023).…”

“…Since the launch of the Breakthrough Initiatives, 14 in particular Breakthrough Listen in 2015 (Isaacson et al 2017;Worden et al 2017), dedicated observations with the Parkes 64 m telescope (Murriyang) and the GBT have yielded improved sensitivities (approximately an order of magnitude over Project Phoenix) but on a similar order of 1000-2000 stars (i.e., Enriquez et al 2017;Price et al 2020;Gajjar et al 2022;Ma et al 2023). These programs were also initially limited in frequency coverage; however, in the last 3 yr, the search has broadened to cover the range of ∼800 MHz to 12 GHz (e.g., Suresh et al 2023), although few results have yet been published at the newly covered frequencies. Additionally, low-Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence.…”