GRB 260730B
GCN Circular 45293
Subject
GRB 260730B: Glowbug gamma-ray detection
Date
2026-08-05T22:36:31Z (21 days ago)
From
C.C. Cheung at Naval Research Lab <Teddy.Cheung@nrl.navy.mil>
Via
Web form
C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260730B, which was also detected by NuSTAR (GCN 45262), AstroSat (GCN 45265), and CALET (GCN 45284).
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-07-30 13:13:49.456 with a duration of 8.2 s and a total significance of about 21.8 sigma. The light curve comprises a multi-peaked structure corresponding to the brightest portion of the burst seen in the CALET light curve (GCN 45284).
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12.
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108
Distribution Statement A: Approved for public release. Distribution is unlimited.
GCN Circular 45284
Subject
GRB 260730B: CALET Gamma-Ray Burst Monitor detection
Date
2026-08-04T09:55:59Z (23 days ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
Y. Shimizu (Kanagawa U), A. Yoshida, T. Sakamoto, S. Sugita,
Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA),
Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU),
S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260730B
at 13:13:50.13 UTC on 30 July 2026 (trigger #1469452426;
https://cgbm.calet.jp/cgbm_trigger/flight/1469452426/index.html).
No real-time CGBM GCN notice was distributed about this trigger because
the real-time communication from the ISS was off (loss of signal).
This event was also reported by NuSTAR (Waratkar et al., GCN #45262) and
AstroSat CZTI (Goyal et al., GCN #45265).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure starting
at T-5.5 s, peaking at T+5.9 s, and ending at T+22.1 s.
The T90 and T50 durations measured with the SGM data are 17.1 +/- 0.9 s
and 6.1 +/- 0.9 s in the 40-1000 keV band, respectively.
The ground-processed light curve is available at:
https://cgbm.calet.jp/cgbm_trigger/ground/1469452426/
The CALET data used in this analysis were provided by
the Waseda CALET Operation Center located at Waseda University.
GCN Circular 45265
Subject
GRB 260730B: AstroSat CZTI detection
Date
2026-07-31T10:25:34Z (a month ago)
From
Anuraag Arya at IIT Bombay <aryaanuraag910@gmail.com>
Via
Web form
A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), 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 Bright, long GRB 260730B which was also detected by NuSTAR (G. Waratkar, GCN Circ. 45262).
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 2026-07-30 13:13:56.216 UTC. The measured peak count rate associated with the burst is 1201 (+58, -66) counts/s above the background in the combined data of three quadrants (out of four), with a total of 8451 (+206, -277) counts. The local mean background count rate was 243(+3, -3) counts/s. We measure a T90 of 16.0 (+0.3, -0.3) s from the cumulative CZT light curve.
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 2026-07-30 13:13:55.471 UTC. The measured peak count rate associated with the burst is 2594 (+88, -100) counts/s above the background in the combined data of all quadrants, with a total of 15878(+327, -466) counts. The local mean background count rate was 715 (+5, -5) counts/s. We measure a T90 of 15.6 (+0.4, -0.3) s from the cumulative Veto light curve.
CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260730T131406/ET20260730T131406_details.html
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 45262
Subject
GRB 260730B: NuSTAR detection of prompt emission
Date
2026-07-31T02:58:15Z (a month 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 260730B 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 2026-07-30T13:13:45.0 UTC, shows a detection of GRB 260730B, also detected by SVOM-GRM (GCN notices).
The NuSTAR CsI shield data are recorded at 1 Hz. We detect a single episode with two peaks lasting for about 25-s. The peak count rate is ~3500-cps with a baseline rate of ~1000-cps during this time period. We also see a 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/2026/260730B
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.