First Fast Radio Burst Search Campaign at the Argentine Institute of Radio Astronomy

Fast radio bursts (FRBs) are intense millisecond-duration radio transients of extragalactic origin whose physical nature remains under investigation, and which also probe the intergalactic medium. We report on the first FRB search campaign carried out at the Argentine Institute of Radio Astronomy (IAR), between 2024 December and 2026 March, targeting nearby galaxy superclusters in the southern sky. We observed fields in the Ophiuchus, Shapley, and Sculptor/Phoenix supercluster regions with one of the two 30 m antennas of the IAR, using a ROACH-based backend with 400 MHz of bandwidth centered at 1400 MHz and a time resolution of 41–82 μ s, for a total net observing time of 212 hr. The data were searched for dispersed single pulses with PRESTO in the dispersion measure (DM) range of 100 ≤ DM ≤ 500 pc cm −3 , and candidates were classified with the FETCH machine learning classifier, validated on archival Parkes data containing known FRBs and on synthetic bursts injected into IAR observations. One FRB candidate, FRB 20251018, was identified on 2025 October 18 in an observation pointed toward the galaxy cluster A2870, in the Phoenix supercluster, with a DM of 243 ± 20 pc cm −3 , a signal-to-noise ratio of 8.2, and a FETCH score of p = 0.99. To the best of our knowledge, it would, if confirmed, be the first FRB detected from South America. A set of more marginal candidates is also presented. These results demonstrate the capability of the IAR antennas to detect FRBs and support extending the monitoring campaign to coincident dual-antenna observations and crossmatches with gravitational-wave events and electromagnetic transients.