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[vsnet-grb-info 42223] GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44102 SUBJECT: GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions DATE: 26/03/24 12:34:17 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Fredd Sánchez Álvarez (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) SVOM BA1 and SVOM BA2 report: We imaged the field of the SVOM GRB 260321A (Brunet et al., GCN Circ. 44071) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-03-22 06:35:41 to 09:32:17 UTC (from 12.39 to 15.34 hours after the trigger) and obtained 128 minutes of exposure in the r and z filters. A second comparison epoch was observed from 2026-03-24 06:16:18 to 09:07:59 UTC (from 60.07 to 62.93 hours after the trigger) again in r and z with 128 min of exposure. The data were reduced and coadded with the ASU pipeline, and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the comparison and subtraction of the two epochs, we do not detect any credible new source at any of the FXT source positions (Zou et al., GCN Circ. 44086) down to the following 3-sigma limit: r > 24.7 z > 23.6 These upper limits supersede the ones reported by de Ugarte Postigo et al. (GCN Circ. 44078). We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/44102. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42222] EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44101 SUBJECT: EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7 DATE: 26/03/24 10:20:29 GMT FROM: I. Perez-Garcia at Instituto de Astrofísica de Andalucía <ipg(a)iaa.es> I. Perez-Garcia, S.-Y. Wu, A. J. Castro-Tirado, E. J. Fernandez-Garcia, M.D. Caballero-Garcia, S. Guziy, G. Garcia-Segura, R. Sanchez-Ramirez (IAA-CSIC), Y.-D. Hu (INAF-OAB), C. Perez del Pulgar, A. Castellon, I. Carrasco (Univ. de Malaga), L. Hernandez-Garcia (Univ. de Valparaiso), M. Gritsevich (Univ. of Helsinki), S. Jeong (ADD, Daejeon), D. Hiriart (IA-UNAM, Ensenada), W. H. Lee (UNAM, Mexico DF), D.-R. Xiong (Yunnan Observatories of CAS), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report: Following the detection of trigger 01709259112 by EP-WXT (Tang et al. GCN 44099), both the 0.6m robotic telescopes BOOTES-5/JGU robotic telescope at San Pedro Martir Observatory (Mexico) and BOOTES-7 at San Pedro de Atacama (Chile) responded to the alert on March 24, 5:17 UT (i.e. 1 min after notification and 26 min after the trigger). Within the reported EP-FXT error circle we find the star SCOCENSUS 132-087992 decreasing 2.3, 1.9 and 1.6 mag in g, r and i filters during a 3.5 hours time interval, confirming EP-WXT trigger 01709259112 as due to a stellar flare. We thank the staff at San Pedro de Atacama Celestial Observations and San Pedro Martir Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/44101. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42221] GRB 260316B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44100 SUBJECT: GRB 260316B: CALET Gamma-Ray Burst Monitor detection DATE: 26/03/24 07:55:16 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> T. Tamura (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), Y. Shimizu (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The GRB 260316B (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN Circ. 44031; AstroSat CZTI detection: Harsha et al., GCN Circ. 44035; SVOM/GRM observation: Wang et al., GCN Circ. 44039; GECAM-B observation: Wang et al., GCN Circ. 44040) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 17:12:52.15 UTC on 16 March 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1457716347/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a single pulse that starts at T+0.38 sec, peaks at T+1.25 sec, and ends at T+2.37 sec. The T90 and T50 durations measured by the SGM data are 1.75 +/- 0.18 sec and 0.75 +/- 0.13 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1457716347/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44100. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42220] The EP-WXT trigger 01709259112 is likely a flaring star
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44099 SUBJECT: The EP-WXT trigger 01709259112 is likely a flaring star DATE: 26/03/24 06:03:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. H. Tang, C. Y. Wang (THU), A. Li (BNU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709259112 at the time of 2026-03-24T04:51:45, is likely a stellar flare associated with Young stellar object SCOCENSUS 132-087992. The estimated flux of the flare is around 1.8×10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.8×10^32 erg/s. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/44099. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42219] Fermi GRB 260323A: Global MASTER-Net observations report
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44098 SUBJECT: Fermi GRB 260323A: Global MASTER-Net observations report DATE: 26/03/24 00:15:25 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260323A ( Fermi GBM team, GCN 44097) errorbox 143 sec after notice time and 173 sec after trigger time at 2026-03-23 23:54:21 UT, with upper limit up to 20.1 mag. Observations started at twilight. The observations began at zenith distance = 43 deg. The sun altitude is -16.3 deg. The galactic latitude b = -27 deg., longitude l = 289 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3206970 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 188 | 2026-03-23 23:54:21 | MASTER-OAFA | (06h 02m 40.77s , -72d 38m 38.2s) | C | 30 | 18.8 | 229 | 2026-03-23 23:54:57 | MASTER-OAFA | (06h 02m 40.97s , -72d 38m 38.5s) | C | 40 | 18.9 | 280 | 2026-03-23 23:55:43 | MASTER-OAFA | (06h 02m 41.22s , -72d 38m 38.9s) | C | 50 | 19.2 | 341 | 2026-03-23 23:56:39 | MASTER-OAFA | (06h 02m 41.55s , -72d 38m 39.0s) | C | 60 | 19.3 | 650 | 2026-03-24 00:01:17 | MASTER-OAFA | (06h 42m 20.00s , -76d 51m 39.3s) | C | 120 | 20.1 | 786 | 2026-03-24 00:03:23 | MASTER-OAFA | (06h 42m 20.80s , -76d 51m 40.5s) | C | 140 | 20.1 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/44098. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42218] GRB 260323A: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Mar '26

24 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44097 SUBJECT: GRB 260323A: Fermi GBM Final Real-time Localization DATE: 26/03/24 00:02:09 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 23:51:27 UT on 23 Mar 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260323A (trigger 796002692.989066 / 260323994). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 100.1, Dec = -77.1 (J2000 degrees, equivalent to J2000 06h 40m, -77d 05'), with a statistical uncertainty of 5.5 degrees. The angle from the Fermi LAT boresight is 149.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260323994/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260323994/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260323994/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44097. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42217] GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44096 SUBJECT: GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days DATE: 26/03/23 22:07:59 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days D. A. Perley (LJMU), Y. Wagh (LJMU), R. Jayaraman (Cornell), J. Sollerman (Stockholm), A. Y. Q. Ho (Cornell), K.-R. Hinds (Caltech), and A. Bochenek (LJMU) report: We used the SED Machine Rainbow Camera optical imager mounted on the Palomar 60-inch telescope to obtain observations of AT2026fgk (Hinds et al., TNS AstroNote 2026-65), the optical counterpart (Konno et al., GCN 43974) of the Fermi/GBM gamma-ray burst GRB260310A (Fermi GBM Team, GCN 43951; Hamburg & Meegan, GCN 43975). Observations began on the night of 2026-03-12 at 06:03 UT and have continued every night since in the SDSS g, r, and i filters; u-band imaging was also taken on certain nights. Photometry was performed following image subtraction of template images taken from Pan-STARRS survey imaging. For the first seven days after the GRB, the fading is generally consistent with a power-law evolution with a shallow temporal index of approximately -0.6. Beginning at around 7-8 days, the afterglow begins falling more sharply, with a decay index closer to -1.35. (A break in the X-ray light curve was seen at a similar time; Jayaraman et al., GCN 44095 ). Select photometry (AB, not corrected for extinction) is provided below: | UT date | dt (d) | filter | mag +/- unc | |---------------------|--------|--------|----------------| | 2026-03-12 06:03:41 | 2.047 | r | 18.14 +/- 0.04 | | 2026-03-13 06:33:38 | 3.067 | r | 18.19 +/- 0.03 | | 2026-03-15 06:08:19 | 5.050 | r | 18.59 +/- 0.03 | | 2026-03-18 06:01:43 | 8.045 | r | 18.83 +/- 0.03 | | 2026-03-23 05:20:09 | 13.016 | r | 19.58 +/- 0.04 | The behavior is consistent with other recent reports noting the continuation of the optical decay with no SN-like rebrightening yet (e.g., Volnova et al., GCN 44060; Bussman et al., GCN 44061). Accounting for Galactic extinction and converting to the equivalent host-frame bandpass, the absolute magnitude of the optical transient as of the most recent observation is M_V ~ -19.7. The fact that the light curve is still decaying steeply suggests that any associated supernova is likely to be significantly dimmer than the benchmark SN1998bw, which peaked at a similar magnitude and phase (e.g., Galama et al. 1998, Nature, 395, 670). The color of the afterglow indicates only modest dust extinction in the host galaxy, so the subluminous nature of the SN is likely intrinsic. A fainter SN comparable to SN2006aj is not yet ruled out, but will be tightly constrained by observations during the next 1-2 weeks. Additionally, we note that the optical afterglow is both extremely bright and very luminous at late times. To our knowledge only one[1] previous GRB (GRB030329 at z=0.168) has remained brighter than r=20 mag more than 10 observer-frame days after the event, excluding events dominated by the rebrightening of the SN on this timescale (see e.g., Kann et al. 2023, ApJL, 948, 12). The luminosity is also notable: despite its relatively weak prompt emission (E_iso ~ 10^51 erg: Minaev et al., GCN 44053), the afterglow luminosity of GRB260310A at the current time is at the upper end of the afterglow luminosity distribution at this time post-burst, comparable to many high-luminosity (E_iso ~ 10^54 erg) GRBs such as 080319B, 130427A, and 221009A. We encourage continued monitoring of this exceptional GRB afterglow (and any potential associated SN), which is likely to remain accessible to small- to medium-size optical facilities for many more weeks and possibly months. [1] GRB221009A would have been observed to have a similar apparent magnitude at this time but was heavily obscured by Galactic dust. Based on observations obtained with the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan, and the German Center for Astrophysics (DZA), Germany. Operations are conducted by Caltech's Optical Observatory (COO), Caltech/IPAC, and the University of Washington at Seattle, USA. DAP acknowledges the work, legacy, and friendship of D. Alexander Kann, who doubtless would have been tremendously excited by this GRB afterglow. View this GCN Circular online at https://gcn.nasa.gov/circulars/44096. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42216] GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44095 SUBJECT: GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data DATE: 26/03/23 21:59:34 GMT FROM: Rahul Jayaraman at Cornell University <rj438(a)cornell.edu> Rahul Jayaraman (Cornell), Gaurav Waratkar (Caltech), K-Ryan Hinds (Caltech), Yogesh Wagh (LJMU), Daniel Perley (LJMU), Anna Y. Q. Ho (Cornell), S. Y. Fu (HUST), R. D. Liang, M. J. Liu, Z. X. Ling, Hui Sun, Weimin Yuan (NAO, CAS), Genevieve Schroeder (Cornell), Xander J. Hall (CMU), Michael Coughlin (UMN), Aleksandra Bochenek (LJMU), and Jesper Sollerman (Stockholm) report: The Follow-up X-ray Telescope on board the Einstein Probe has continued to monitor the X-ray afterglow of GRB 260310A (Fermi GBM team, GCN 43951; Arya et al., GCN 43958; Jayaraman et al., GCN 43994), which is associated with the optical transient AT2026fgk (Konno et al., GCN 43974; Hinds et al., AstroNote 2026-65). Observations with duration ~3 ks were taken at intervals of roughly every 2 days after the initial detection of this source in X-rays (Jayaraman et al., GCN 43994). With four further epochs of data since the initial detection, we find evidence for a steepening in the X-ray light curve at around 8 ± 2 days after the burst, with the decay slope steepening from roughly –0.3 to –1.6. The photon index measured by EP remains at roughly 1.5 throughout these observations. This steepening appears contemporaneous with an observed steepening at a similar epoch post-burst in r-band photometric data taken by the SED Machine on the Palomar P60 telescope, which will be reported in a forthcoming Circular. Launched on January 9, 2024, the Einstein Probe is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). EP is supported by the Strategic Priority Program on Space Sciénce of the Chinese Academy of Sciences, in collaboration with the European Space Agency, the Max-Planck-Institute for Extraterrestrial Physics (Germany), and the Centre National d'études Spatiales (France). View this GCN Circular online at https://gcn.nasa.gov/circulars/44095. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42215] GRB 260322A: Fermi GBM Final Localization
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44094 SUBJECT: GRB 260322A: Fermi GBM Final Localization DATE: 26/03/23 17:56:30 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> The Fermi GBM team reports the detection of a likely SHORT GRB "At 10:45:40 UT on 22 March 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260322A (trigger 795869144/260322448). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 301.0, Dec = -61.8 (J2000 degrees, equivalent to J2000 20h 3m, -61d 46'), with a statistical uncertainty of 7.9 degrees. The angle from the Fermi LAT boresight is 59.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260322448/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260322448/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260322448/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44094. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42214] GRB 260320A: Glowbug gamma-ray detection
by GCN Circulars 23 Mar '26

23 Mar '26

TITLE: GCN CIRCULAR NUMBER: 44093 SUBJECT: GRB 260320A: Glowbug gamma-ray detection DATE: 26/03/23 17:34:44 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> 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, confirms the detection of GRB 260320A, which was detected by NuSTAR (GCN 44064), SVOM/GRM (sb26032003), Insight-HXMT/HE (GCN 44077), and Konus-Wind (Trig_Time 19:40:01.257). The burst onset is at 2026-03-20 19:40:02, with a peak at ~T0+1.5s, and a burst duration of ~7s. Note that data throughout the detection interval suffered from deadtime in various detectors. 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/44093. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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