GRB 260506B

S. Salunke (IUCAA), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), A. Goyal (IITB), A. Arya (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 CIFT2 framework showed the detection of GRB 260506B which is also detected by the Fermi/GBM (Fermi GBM team, GCN Circ. 44484
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 ).

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 2026-05-06 13:07:41.9 UTC. The measured peak count rate associated with the burst is 129 (+37, -17) counts/s above the background in the combined data of all  four quadrants, with a total of 899 (+239, -328) counts. The local mean background count rate was 289 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 22 (+12, -15) s. We caution that there is a 0.3 s dead time in the CZTI data in the burst, hence the actual T90 may be slightly longer.

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 2026-05-06 13:07:42.0 UTC. The measured peak count rate associated with the burst is 440 (+67, -69) counts/s above the background in the combined data of all quadrants, with a total of 3325 (+520, -551) counts. The local mean background count rate was 1313 (+4, -4) counts/s. We measure a T90 of 36 (+3, -7) 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 data products like interactive and downloadable light curves for this GRB can be found at:
https://astrosat.iucaa.in/cift/cift_products/515768858.51/S515768858.51_details.html

CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb

T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:

The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
799765648 at 13:07:23 on 06 May 2026 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).

The best-fit position is:
RA(2000.0) = 280.7 deg
Decl.(2000.0) = -6.1 deg
The 1 sigma statistical error radius is 1.5 deg.
We estimate an additional systematic error of 1 deg.

Further details are available at:
https://grb.mpe.mpg.de/grb/GRB260506547/

The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB260506547/healpix

The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB260506547/json

                        

The Fermi GBM team reports the detection of a likely LONG GRB

At 13:07:23 UT on 6 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260506B (trigger 799765648.964258 / 260506547).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 280.5, Dec = -0.5 (J2000 degrees, equivalent to J2000 18h 41m, 0d 30'), with a statistical uncertainty of 1.8 degrees.

The angle from the Fermi LAT boresight is 44.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260506547/quicklook/glg_skymap_all_bn260506547.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260506547/quicklook/glg_healpix_all_bn260506547.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260506547/quicklook/glg_lc_medres34_bn260506547.gif