TITLE: GCN CIRCULAR NUMBER: 46031 SUBJECT: GRB 261024A: NuSTAR detection of prompt emission DATE: 26/10/26 06:39:29 GMT FROM: Gaurav Waratkar at Caltech G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 261024A in both the NuSTAR CsI anti-coincidence shields. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2026-10-24T16:23:00.790 UTC shows a detection of GRB 261024A, also detected by Fermi-GBM (GCN 46019). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single-peaked burst lasting for about 10-s. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We also see a faint detection in the signal above 100 keV in the CZT detectors. The Fermi-GBM localization (GCN 46019) at RA = 317.0, Dec = 63.1 implies an offset from the NuSTAR boresight of 62-deg and an offset from the geocenter of 76-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261024A Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington.