GCN Circular 46052
Subject
GRB 261026B: NuSTAR detection of prompt emission
Event
Date
2026-10-26T22:01:21Z (3 days 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 261026B 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 2026-10-26T07:21:12.380 UTC shows a detection of GRB 261026B, also detected by Fermi-GBM (GCN 46032), SVOM-GRM (GCN notices), and KONUS-Wind (GCN notices).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single-peaked burst lasting for about 20-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 Fermi-GBM localization (GCN 46032) at RA = 61.8, Dec = -1.7 implies an offset from the NuSTAR boresight of 38-deg and an offset from the geocenter of 140-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/261026B
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.