GRB 250813A
GCN Circular 41365
Subject
GRB 250813A: AstroSat CZTI detection
Date
2025-08-14T10:31:51Z (12 days ago)
From
Gaurav Waratkar at IIT Bombay <gauravwaratkar@iitb.ac.in>
Via
Web form
M. Tembhurnikar (IUCAA), G. Waratkar (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 GRB 250813A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 41343).
The source was faintly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-08-13 01:46:01.50 UTC. The measured peak count rate associated with the burst is 72 (+35, -16) counts/s above the background in the combined data of all quadrants, with a total of 485 (+199, -228) counts. The local mean background count rate was 249 (+5, -6) counts/s. Using cumulative rates, we measure a T90 of 12 (+1, -6) s.
The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-08-13 01:46:00.12 UTC. The measured peak count rate associated with the burst is 117 (+70, -10) counts/s above the background in the combined data of all quadrants, with a total of 1002 (+403, -457) counts. The local mean background count rate was 1144 (+8, -8) counts/s. We measure a T90 of 13 (+2, -4) 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
GCN Circular 41343
Subject
GRB 250813A: Fermi GBM Final Localization
Date
2025-08-13T13:54:08Z (13 days ago)
From
eliza.neights@gmail.com
Via
Web form
The Fermi GBM team reports the detection of a likely LONG GRB
"At 01:46:03.86 UT on 13 August 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250813A (trigger 776742368/250813074).
The on-ground calculated location, using the Fermi GBM trigger data,
is RA = 355.90, Dec = 57.28 (J2000 degrees, equivalent to J2000 23h 43m, +57d 16'),
with a statistical uncertainty of 3.06 degrees.
The angle from the Fermi LAT boresight is 19 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250813074/quicklook/glg_skymap_all_bn250813074.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250813074/quicklook/glg_healpix_all_bn250813074.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250813074/quicklook/glg_lc_medres34_bn250813074.gif"