The FAST-SETI Milky Way Globular Cluster Survey. I. A Pilot Multibeam On-the-fly Search of Five Globular Clusters at the L Band
Year: 2025
Type: article
Abstract: We report a narrowband technosignature search toward five Milky Way globular clusters—NGC 6171, NGC 6218, NGC 6254, NGC 6838, and IC 1276—using Five-hundred-meter Aperture Spherical radio Telescope (FAST)’s 19 beam L -band receiver (1.05–1.45 GHz). We adapted MultiBeam Point-source Scanning (MBPS) to extended targets by gating detections to generalized on-target windows (gOTWs), i.e., the time intervals when a beam’s main lobe intersects a buffered cluster mask, and by enforcing the deterministic multibeam illumination sequence as a geometry test. Spectra at Δ ν ≈ 7.5 Hz resolution and Δ t ≈ 10 s cadence were searched with turboSETI over ∣ ν ̇ ∣ ≤ 4 Hz s − 1 at S/N ≥ 10. From 2.75 × 10 5 raw hits across both linear polarizations, none survived the gOTW gating, array-wide simultaneity veto, in-stripe ordering, and single-drift coherence checks, yielding a robust null result. With SEFD ≈ 1.5 Jy and an effective ∼60 s per illuminated crossing, our per-crossing flux density threshold is S min ≈ 0.50 Jy, corresponding to EIRP min ≈ ( 0.72 – 1.8 ) × 1 0 16 W for cluster distances of 4–6.5 kpc; when multiple illuminated crossings occur, noncoherent stacking improves sensitivity by up to N . To our knowledge, this is the first FAST technosignature survey dedicated to globular clusters and the first to use MBPS as the primary observing strategy. These limits disfavour bright, persistent, isotropic L -band beacons above the stated thresholds during our epochs and establish a scalable blueprint—geometry-aware gating and verification—for multiepoch MBPS campaigns that expand signal morphologies and combine passes to deepen constraints on transmitters in dense stellar systems.
Source: The Astronomical Journal
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $4,499
OpenAlex ID: W4416784167