TITLE: GCN CIRCULAR NUMBER: 46051 SUBJECT: GRB 261024D: NuSTAR detection of prompt emission DATE: 26/10/26 21:58:49 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 261024D 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 2026-10-24T21:33:05.000 UTC shows a detection of GRB 261024D, also detected by SVOM-GRM (GCN Notices), KONUS-Wind (GCN Notices), and AstroSat-CZTI (GCN 46040). 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 do not see any evidence in the signal above 100 keV in the CZT detectors. The SVOM-GRM localization at RA = 209.99, Dec = -47.33 implies an offset from the NuSTAR boresight of 100-deg and an offset from the geocenter of 102-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261024D 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.