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[vsnet-grb-info 40594] GRB 251028B: Fermi/GBM observation
by GCN Circulars 29 Oct '25

29 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42509 SUBJECT: GRB 251028B: Fermi/GBM observation DATE: 25/10/29 11:59:34 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> C. Malacaria (INAF-OAR) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:48:06.71 UT on 28 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251028B (trigger 783330491/251028325), which was also detected by the Glowbug (Woolf et al. 2025, GCN 42507) and Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 42508). A final Fermi/GBM localization correction was issued in GCN 42502. The GBM light curve consists of two main pulses with a duration (T90) of about 14 s (50-300 keV). The time-averaged spectrum from T0-0.3 s to T0+12.0 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.77 +/- 0.10 and the cutoff energy, parameterized as Epeak, is 125 +/- 8 keV. The event fluence (10-1000 keV) in this time interval is (3.9 +/- 0.2)E-06 erg/cm^2. The 1.024-sec peak photon flux measured starting from T0+8.9 s in the 10-1000 keV band is 6.4 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 113 +/- 11 keV, alpha = -0.68 +/- 0.14 and beta = -2.8 +/- 0.4. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog." View this GCN Circular online at https://gcn.nasa.gov/circulars/42509. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40593] GRB 251028B: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42508 SUBJECT: GRB 251028B: Swift/BAT-GUANO localization skymap of a burst DATE: 25/10/28 18:52:40 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251028B onboard (T0: 2025-10-28T07:48:06.71 UTC, Fermi Trig 783330491, CALET Trig 1445672396, Glowbug GCN 42507) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 12.3 in a 1.024 s analysis time bin, starting at T0 + 8.704 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 6,959 deg2 and the 50% credible area is 1,123 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 42502). The combined Fermi/GBM+NITRATES 90% credible area is 436 deg2 and the 50% credible area is 92 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=783330523/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/783330523/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/783330523/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=783330523 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/42508. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40592] GRB 251028B: Glowbug gamma-ray detection
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42507 SUBJECT: GRB 251028B: Glowbug gamma-ray detection DATE: 25/10/28 18:24:36 GMT FROM: richard.s.woolf.civ(a)us.navy.mil R. Woolf, C.C. Cheung, 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 251028B, which was also detected by Fermi GBM (GCN 42502) and CALET (GCN 42505). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-10-28 07:48:04.672 with a duration of 22.5 s and a total significance of about 30.5 sigma. The light curve comprises two primary peaks. 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/42507. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40591] GRB 251028A: Glowbug gamma-ray detection
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42506 SUBJECT: GRB 251028A: Glowbug gamma-ray detection DATE: 25/10/28 17:54:20 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, reports the detection of GRB 251028A, which was also detected by Fermi/GBM (GCN 42497, 42499) and MAXI/GSC (GCN 42498). Using an adaptive window with a resolution of 32-ms, and taking the GBM-reported T0 (2025-10-28 03:26:31 UT), the burst onset is determined to be T0+22.48s with a duration of 2.0 s and a total significance of about 7.5 sigma. The single peak observed by Glowbug corresponds to the maximum in the Fermi/GBM light curve (GCN 42497). Additional lower-level emission from ~T0+5s to T0+20s may be present in the Glowbug light curve at low significance. 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/42506. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40590] GRB 251028B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42505 SUBJECT: GRB 251028B: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/28 16:08:21 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> Y. Akaike (Waseda U), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (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 long GRB 251028B (Fermi GBM Final Localization Correction: Fermi GBM team, GCN Circ. 42502) triggered the CALET Gamma-ray Burst Monitor (CGBM) at 07:48:06.24 UTC on 28 October 2025 (https://cgbm.calet.jp/cgbm_trigger/flight/1445672396/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure that starts at T-0.5 sec, peaks at T+9.9 sec, and ends at T+11.5 sec. The T90 and T50 durations measured by the SGM data are 11.3 +/- 0.4 sec and 8.5 +/- 0.3 sec (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1445672396/ 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/42505. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40589] Fermi GRB 251028B: Global MASTER-Net observations report
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42504 SUBJECT: Fermi GRB 251028B: Global MASTER-Net observations report DATE: 25/10/28 14:00:39 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 251028B ( Fermi GBM team, GCN 42502) errorbox 19936 sec after notice time and 19967 sec after trigger time at 2025-10-28 13:20:54 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 6 deg. The sun altitude is -33.5 deg. The galactic latitude b = -10 deg., longitude l = 99 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3025691 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 19998 | 2025-10-28 13:20:54 | MASTER-Tunka | (22h 31m 44.47s , +45d 04m 55.7s) | C | 60 | 18.6 | 19998 | 2025-10-28 13:20:54 | MASTER- | (22h 30m 56.32s , +45d 13m 01.0s) | C | 60 | 18.3 | 20070 | 2025-10-28 13:22:06 | MASTER-Tunka | (22h 34m 25.03s , +46d 58m 00.3s) | C | 60 | 17.5 | 20070 | 2025-10-28 13:22:06 | MASTER- | (22h 33m 35.14s , +47d 06m 10.6s) | C | 60 | 17.3 | 20146 | 2025-10-28 13:23:22 | MASTER-Tunka | (22h 30m 48.12s , +43d 08m 44.4s) | C | 60 | 13.9 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42504. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40588] GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42503 SUBJECT: GRB 251025B: GROWTH-India Telescope continued multiband optical observations and rebrightening DATE: 25/10/28 12:33:26 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan, V. Swain, S. Patil, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of SVOM GRB 251025B (Hussein et al., GCN 42437), with 0.7m GROWTH-India Telescope (GIT). Our second epoch started at 2025-10-25 22:07:53 UT, i.e. about 7.73 hours after the SVOM trigger. Multiple exposures were obtained in the r′ and i' filters, and we detect the optical afterglow in our stacked images. The photometry result follows as: | MJD (mid) | tmid - t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | | --------- | ----------------- | ------ | ------------ | -------------- | |60973.93279| 7.99 | r' | 5 x 360 | 19.97 +- 0.08 | |60973.95429| 8.5 | i' | 5 x 360 | 19.82 +- 0.16 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The optical counterpart has rebrightened by ~0.4 mag over a period of about 5.8 hours since our earlier observation (Mohan et al., GCN 42447), consistent with other reports by Li et al., GCN 42453; Pereyra et al., GCN 42452; Freeberg et al., GCN 42474. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42503. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40587] GRB 251028B: Fermi GBM Final Localization Correction
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42502 SUBJECT: GRB 251028B: Fermi GBM Final Localization Correction DATE: 25/10/28 10:12:02 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> The Fermi GBM team reports the detection of a likely LONG GRB "At 07:48:06.71 UT on 28 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251028B (trigger 783330491/251028325). This trigger was initially classified as Distant Particles by the flight software, but is in fact a GRB. The on-ground calculated location, using the Fermi GBM trigger data, is RA = 337.82, Dec = 45.75 (J2000 degrees, equivalent to J2000 22h 31m, +45d 45'), with a statistical uncertainty of 3.69 degrees. The angle from the Fermi LAT boresight is 119 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251028325/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251028325/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251028325/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42502. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40586] GRB251026B: PRIME H-band upper limit
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42501 SUBJECT: GRB251026B: PRIME H-band upper limit DATE: 25/10/28 10:04:28 GMT FROM: Massine El Kabir <m.elkabir(a)campus.unimib.it> M. El Kabir (U Rome), N. Passaleva (U Rome), J. Durbak (UMD), O. Guiffreda (UMD), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) Following the detection of a candidate optical counterpart (Belkin et al., GCN 42470), we observed the field of GOTO GOTO25jgl/AT2025absf in the H filter with PRIME. Observations started ~ 2 d after the initial Fermi trigger (Dafčíková et al., GCN 42455). At the GOTO position (Belkin et al., GCN 42470), no obvious counterpart is detected on the top of the bright nearby galaxy. Due to the bright galaxy background, it is hard to assess the presence of a faint transient source without a template. Using GALFIT, we modelled the galaxy with a single Sersic profile and, after subtraction, derive a 3-sigma upper limit of H > 19 AB mag PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42501. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40585] GRB251025B: 3.6m DOT Optical Observations
by GCN Circulars 28 Oct '25

28 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42500 SUBJECT: GRB251025B: 3.6m DOT Optical Observations DATE: 25/10/28 07:35:28 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kumar Pranshu, Dhruv Jain, Debolina Kar, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB 251025B detected by SVOM/ECLAIRs (Hussein et al. 2025; GCN 42437) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-10-27 at 04:20:49.73 UT, i.e., ~1.58 days after the SVOM trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect an optical counterpart in our stacked image within the error box of SVOM telescope (Hussein et al. 2025; GCN 42437) and Swift-XRT (Beardmore et al. 2025; GCN 42445). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================== 2025-10-27 04:20:49.73 ~1.58 ~ R 300s*8 20.866 +/-0.007 Our detection is consistent with Wu et al. 2025 (GCN 42438); Gress et al. 2025 (GCN 42439); Wu et al. 2025 (GCN 42440); Beardmore et al. 2025 (GCN 42445); Mohan et al. 2025 (GCN 42447); Hernández Fung et al. 2025 (GCN 42450); Pereyra et al. 2025 (GCN 42452); Li et al. 2025 (GCN 42453); Mo et al. 2025 (GCN 42459); Rakotondrainibe et al. 2025 (GCN 42460); Rajabov et al. 2025 (GCN 42466); Saccardi et al. 2025 (GCN 42472); Freeberg et al. 2025 (GCN 42474); Volnova et al. 2025 (GCN 42475). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42500. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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