GCN 44198: GRB 260402C: NuSTAR detection of prompt emission
2026-04-03T07:28:44.522Z | rev 0
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 260402C 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 2026-04-02 13:13:00 UTC, shows a detection of GRB 260402C, consistent with AstroSat/CZTI (Tembhurnikar et al., GCN Circ. 44197).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a ~10-s burst consistent with the first bright peak in the AstroSat/CZTI light curve, with marginal evidence of a second peak consistent with the CZTI light curve. The peak count rate is ~2000-cps with a baseline rate of ~1000-cps during this time period. We do see marginal evidence in the signal above 100 keV in the CZT detectors.
Lightcurves and analysis for this GRB can be found here:
https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260402C/
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.
GCN 44197: GRB 260402C: AstroSat CZTI detection of a long burst
2026-04-03T07:19:42.689Z | rev 0
M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), S. Salunke (IUCAA), A. Arya (IITB), A. Goyal (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 260402C.
The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-04-02 13:13:05.78 UTC. The measured peak count rate associated with the burst is 254 (+34, -26) counts/s above the background in the combined data of three quadrants (out of four), with a total of 1786 (+230, -307) counts. The local mean background count rate was 210 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 27 (+4, -3) s.
The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-04-02 13:13:05.08 UTC. The measured peak count rate associated with the burst is 570 (+82, -42) counts/s above the background in the combined data of all quadrants, with a total of 3647 (+569, -635) counts. The local mean background count rate was 1405 (+6, -7) counts/s. We measure a T90 of 25 (+4, -1) s from the cumulative Veto light curve.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb