GCN Circular 44591

Subject

GRB 260512A: NuSTAR detection of prompt emission

Event

GRB 260512A

Date

2026-05-12T23:53:06Z (3 days ago)

Edited On

2026-05-13T14:52:27Z (3 days ago)

From

Gaurav Waratkar at Caltech <gauravwaratkar@iitb.ac.in>

Edited By

Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of 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 260512A 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 2026-05-12T16:56:43.530 UTC, shows a detection of GRB 260512A, also detected by Fermi/GBM (Fermi GBM Team, GCN 44587Loading...
 
 ).

The NuSTAR CsI shield data are recorded at 1 Hz. We detect a 10-s long burst consistent with the Fermi/GBM lightcurve. The peak count rate is ~2500-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 Fermi/GBM localization (GCN 44587Loading...
 
 ) at RA = 153.56, Dec = -82.64 implies an offset from the NuSTAR boresight of 15-deg (i.e. near the boresight) and an offset from the geocenter of 96-deg.

Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260512A  

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.