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Abstract The search for extraterrestrial intelligence at radio frequencies has focused on spatial filtering as a primary discriminant from terrestrial interference. Individual search campaigns further choose targets or frequencies based on criteria that theoretically maximize the likelihood of detection, serving as high-level filters for interesting targets. Most filters for technosignatures do not rely on intrinsic signal properties, as the radio-frequency interference (RFI) environment is difficult to characterize. In B. Brzycki et al. (2023), we proposed that the effects of interstellar medium (ISM) scintillation on narrowband technosignatures may be detectable under certain conditions. In this work, we perform a dedicated survey for scintillated technosignatures toward the Galactic center and Galactic plane at theCband (3.95–8.0 GHz) using the Robert C. Byrd Green Bank Telescope (GBT) as part of the Breakthrough Listen program. We conduct a Doppler drift search and directional filter to identify potential candidates and analyze results for evidence of scintillation. We characterize theC-band RFI environment at the GBT across multiple observing sessions spread over months and detect RFI signals with confounding scintillation-like intensity modulation. We do not find evidence of putative narrowband transmitters with drift rates between ±10 Hz s⁻¹toward the Galactic center, ISM-scintillated or otherwise, above an equivalent isotropic radiated power of 1.9 × 10¹⁷W up to 8.5 kpc. 

Abstract To date, the search for radio technosignatures has focused on sky location as a primary discriminant between technosignature candidates and anthropogenic radio frequency interference (RFI). In this work, we investigate the possibility of searching for technosignatures by identifying the presence and nature of intensity scintillations arising from the turbulent, ionized plasma of the interstellar medium. Past works have detailed how interstellar scattering can both enhance and diminish the detectability of narrowband radio signals. We use the NE2001 Galactic free electron density model to estimate scintillation timescales to which narrowband signal searches would be sensitive, and discuss ways in which we might practically detect strong intensity scintillations in detected signals. We further analyze the RFI environment of the Robert C. Byrd Green Bank Telescope with the proposed methodology and comment on the feasibility of using scintillation as a filter for technosignature candidates. 

Abstract The Breakthrough Listen search for intelligent life is, to date, the most extensive technosignature search of nearby celestial objects. We present a radio technosignature search of the centers of 97 nearby galaxies, observed by Breakthrough Listen at the Robert C. Byrd Green Bank Telescope. We performed a narrowband Doppler drift search using theturboSETIpipeline with a minimum signal-to-noise parameter threshold of 10, across a drift rate range of ±4 Hz s⁻¹, with a spectral resolution of 3 Hz and a time resolution of ∼18.25 s. We removed radio frequency interference (RFI) by using an on-source/off-source cadence pattern of six observations and discarding signals with Doppler drift rates of 0. We assess factors affecting the sensitivity of the Breakthrough Listen data reduction and search pipeline using signal injection and recovery techniques and apply new methods for the investigation of the RFI environment. We present results in four frequency bands covering 1–11 GHz, and place constraints on the presence of transmitters with equivalent isotropic radiated power on the order of 10²⁶W, corresponding to the theoretical power consumption of Kardashev Type II civilizations. 

The goal of the search for extraterrestrial intelligence (SETI) is the detection of nonhuman technosignatures, such as technology-produced emission in radio observations. While many have speculated about the character of such technosignatures, radio SETI fundamentally involves searching for signals that not only have never been detected, but also have a vast range of potential morphologies. Given that we have not yet detected a radio SETI signal, we must make assumptions about their form to develop search algorithms. The lack of positive detections also makes it difficult to test these algorithms’ inherent efficacy. To address these challenges, we present setigen, a Python-based, open-source library for heuristic-based signal synthesis and injection for both spectrograms (dynamic spectra) and raw voltage data. setigen facilitates the production of synthetic radio observations, interfaces with standard data products used extensively by the Breakthrough Listen project, and focuses on providing a physically motivated synthesis framework compatible with real observational data and associated search methods. We discuss the core routines of setigen and present existing and future use cases in the development and evaluation of SETI search algorithms. 

Caballero identified the star 2MASS 19281982-2640123 as a potential Sun-like star from which the WOW! signal could have originated. We conducted a search for artificial narrowband (2.79 Hz/1.91 Hz), drifting (±4 Hz s^−1) technosignatures from this source using the turboSETI pipeline, from 1–2 GHz, using simultaneous multi-telescope observations with both the Robert C. Byrd Green Bank Telescope and the newly refurbished Allen Telescope Array on 2022 May 21. Both telescope observations had an overlap of 580 s. While blind searches using radio telescopes have been conducted in the general field of view in which the WOW! signal was first detected, this is the first time a targeted search has been done. No technosignature candidates were detected. 

Abstract We present a multiband study of FRB 20180916B, a repeating source with a 16.3 day periodicity. We report the detection of four, one, and seven bursts from observations spanning 3 days using the upgraded Giant Metrewave Radio Telescope (300–500 MHz), the Canadian Hydrogen Intensity Mapping Experiment (400–800 MHz) and the Green Bank Telescope (600–1000 MHz), respectively. We report the first ever detection of the source in the 800–1000 MHz range along with one of the widest instantaneous bandwidth detections (200 MHz) at lower frequencies. We identify 30 μ s wide structures in one of the bursts at 800 MHz, making it the lowest frequency detection of such structures for this fast radio burst thus far. There is also a clear indication of high activity of the source at a higher frequency during earlier phases of the activity cycle. We identify a gradual decrease in the rotation measure over two years and no significant variations in the dispersion measure. We derive useful conclusions about progenitor scenarios, energy distribution, emission mechanisms, and variation of the downward drift rate of emission with frequency. Our results reinforce that multiband observations are an effective approach to study repeaters, and even one-off events, to better understand their varying activity and spectral anomalies. 

The search for extraterrestrial intelligence at radio frequencies has largely been focused on continuous-wave narrowband signals. We demonstrate that broadband pulsed beacons are energetically efficient compared to narrowband beacons over longer operational timescales. Here, we report the first extensive survey searching for such broadband pulsed beacons toward 1883 stars as a part of the Breakthrough Listen’s search for advanced intelligent life. We conducted 233 hr of deep observations across 4–8 GHz using the Robert C. Byrd Green Bank Telescope and searched for three different classes of signals with artificial (or negative) dispersion. We report a detailed search—leveraging a convolutional neural network classifier on high-performance GPUs—deployed for the very first time in a large-scale search for signals from extraterrestrial intelligence. Due to the absence of any signal-of-interest from our survey, we place a constraint on the existence of broadband pulsed beacons in our solar neighborhood: ≲1 in 1000 stars have transmitter power densities ≳10^5 W Hz^−1 repeating ≤500 s at these frequencies. 

Abstract The Breakthrough Listen (BL) Initiative, as part of its larger mission, is performing the most thorough technosignature search of nearby stars. Additionally, BL is collaborating with scientists working on NASA’s Transiting Exoplanet Survey Satellite (TESS) to examine TESS Targets of Interest (TOIs) for technosignatures. Here, we present a 1–11 GHz radio technosignature search of 61 TESS TOIs that were in transit during their BL observation at the Robert C. Byrd Green Bank Telescope. We performed a narrowband Doppler drift search with a minimum S/N threshold of 10 across a drift rate range of ±4 Hz s⁻¹with a resolution of 3 Hz. We removed radio frequency interference by comparing signals across cadences of target sources. After interference removal, there are no remaining events in our survey, and therefore no technosignature signals of interest detected in this work. This null result implies that atL,S,C, andXbands, fewer than 52%, 20%, 16%, and 15%, respectively, of TESS TOIs possess a transmitter with an equivalent isotropic radiated power greater than a few times 10¹⁴W. 

A line of sight toward the Galactic Center (GC) offers the largest number of potentially habitable systems of any direction in the sky. The Breakthrough Listen program is undertaking the most sensitive and deepest targeted SETI surveys toward the GC. Here, we outline our observing strategies with Robert C. Byrd Green Bank Telescope (GBT) and Parkes telescope to conduct 600 hr of deep observations across 0.7–93 GHz. We report preliminary results from our survey for extraterrestrial intelligence (ETI) beacons across 1–8 GHz with 7.0 and 11.2 hr of observations with Parkes and GBT, respectively. With our narrowband drifting signal search, we were able to place meaningful constraints on ETI transmitters across 1–4 GHz and 3.9–8 GHz with EIRP limits of ≥4 × 10^18 W among 60 million stars and ≥5 × 10^17 W among half a million stars, respectively. For the first time, we were able to constrain the existence of artificially dispersed transient signals across 3.9–8 GHz with EIRP ≥1 × 10^14 W/Hz with a repetition period ≤4.3 hr. We also searched our 11.2 hr of deep observations of the GC and its surrounding region for Fast Radio Burst–like magnetars with the DM up to 5000 pc cm^−3 with maximum pulse widths up to 90 ms at 6 GHz. We detected several hundred transient bursts from SGR J1745−2900, but did not detect any new transient bursts with the peak luminosity limit across our observed band of ≥10^31 erg s^−1 and burst rate of ≥0.23 burst hr^−1. These limits are comparable to bright transient emission seen from other Galactic radio-loud magnetars, constraining their presence at the GC.