2024AJ....168..284B

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 the C band (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 the C-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^–1 toward the Galactic center, ISM-scintillated or otherwise, above an equivalent isotropic radiated power of 1.9 × 10¹⁷ W up to 8.5 kpc.