GCN Circular 45732
Subject
GRB 260924A: NuSTAR detection of prompt emission
Event
Date
2026-09-24T19:26:01Z (a day ago)
From
Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>
Via
Web form
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 260924A 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 2026-09-24T01:13:23.56 UTC shows a detection of GRB 260924A, also detected by Fermi-GBM (GCN 45712), Swift-BAT (GCN 45713), and AstroSat-CZTI (GCN 45720).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a multi-peaked burst lasting for about 150-s, consistent with the GBM, BAT and CZTI lightcurves. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We also see a detection in the signal above 100 keV in the CZT detectors.
The Swift-XRT localization (GCN 45713) at RA = 133.7620, Dec = 12.0455 implies an offset from the NuSTAR boresight of 130-deg and an offset from the geocenter of 158-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260924A
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.