GCN Circular 44555
Subject
GRB 260511A: NuSTAR detection of prompt emission
Event
Date
2026-05-11T16:06:48Z (2 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 260511A in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper.
The NuSTAR SINGS algorithm, triggered at 2026-05-11T06:13:30.0 UTC, shows a detection of GRB 260511A, also detected by Fermi/GBM (Fermi GBM Team, GCN 44529) and SVOM (Godet et al., GCN 44532).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a ~10-s burst consistent with Fermi/GBM. The peak count rate is ~3500-cps with a baseline rate of ~1000-cps during this time period. We do not see evidence in the signal above 100 keV in the CZT detectors.
The optical counterpart candidate (Akl et al., GCN 44534) at RA = 197.8996, Dec = -33.80446 implies an offset from the NuSTAR boresight of 57-deg and an offset from the geocenter of 144-deg.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260511A
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.