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[vsnet-grb-info 40943] GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42874 SUBJECT: GRB 251128A: Swift/BAT-GUANO localization skymap of a burst DATE: 25/11/28 21:14:53 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (GSSI), Aaron Tohuvavohu (Cosmic Frontier), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (Northwestern) report: Swift/BAT did not localize GRB 251128A onboard (T0: 2025-11-28T04:22:21.61 UTC, Fermi Trig 785996546) 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 21.2 in a 4.096 s analysis time bin, starting at T0 - 1.024 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 550 deg2 and the 50% credible area is 74 deg2 The integrated probability inside the coded field of view is <1%. The NITRATES skymap is consistent with the Ferm/GBM localization reported in the final position notice (GCN 42865). The combined Fermi/GBM+NITRATES 90% credible area is 49 deg2 and the 50% credible area is 14 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=785996578/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/785996578/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/785996578/0_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=785996578 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/42874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40942] Fermi GRB 251128A: Global MASTER-Net observations report
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42873 SUBJECT: Fermi GRB 251128A: Global MASTER-Net observations report DATE: 25/11/28 15:15:24 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251128A ( Fermi GBM team, GCN 42865) errorbox 36273 sec after notice time and 36305 sec after trigger time at 2025-11-28 14:27:27 UT, with upper limit up to 16.6 mag. Observations started at twilight. The observations began at zenith distance = 80 deg. The sun altitude is -9.0 deg. The galactic latitude b = 30 deg., longitude l = 166 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3053740 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 36336 | 2025-11-28 14:27:27 | MASTER-Kislovodsk | (07h 48m 24.78s , +54d 16m 19.6s) | C | 60 | 12.8 | 36336 | 2025-11-28 14:27:27 | MASTER-Kislovodsk | (07h 55m 11.13s , +53d 52m 14.4s) | C | 60 | 15.7 | 36496 | 2025-11-28 14:30:07 | MASTER-Kislovodsk | (07h 27m 49.20s , +52d 20m 52.7s) | C | 60 | 13.1 | 36496 | 2025-11-28 14:30:07 | MASTER-Kislovodsk | (07h 34m 27.48s , +51d 56m 56.6s) | C | 60 | 16.0 | 36575 | 2025-11-28 14:31:27 | MASTER-Kislovodsk | (07h 44m 12.06s , +56d 08m 56.4s) | C | 60 | 13.4 | 36575 | 2025-11-28 14:31:27 | MASTER-Kislovodsk | (07h 51m 27.99s , +55d 44m 39.4s) | C | 60 | 16.3 | 36655 | 2025-11-28 14:32:46 | MASTER-Kislovodsk | (07h 29m 20.17s , +53d 53m 04.8s) | C | 60 | 16.6 | 37136 | 2025-11-28 14:40:47 | MASTER-Kislovodsk | (07h 59m 24.43s , +51d 57m 45.1s) | C | 60 | 16.3 | 37136 | 2025-11-28 14:40:47 | MASTER-Kislovodsk | (07h 52m 49.54s , +52d 22m 11.6s) | C | 60 | 13.5 | 37608 | 2025-11-28 14:48:39 | MASTER-Kislovodsk | (07h 39m 46.04s , +50d 04m 30.2s) | C | 60 | 16.5 | 37608 | 2025-11-28 14:48:39 | MASTER-Kislovodsk | (07h 33m 24.33s , +50d 28m 49.0s) | C | 60 | 14.3 | 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/42873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40941] GRB 251127A: Glowbug gamma-ray detection
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42872 SUBJECT: GRB 251127A: Glowbug gamma-ray detection DATE: 25/11/28 14:57:16 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 251127A, which was also detected by Fermi/GBM (GCN 42852). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-27 03:17:42.528 with a duration of 14.8 s and a total significance of about 16.1 sigma. The light curve comprises a bright peak at ~T0 followed by a fainter multi-peaked structure. Note that data from ~T0+7s to +11s 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/42872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40940] GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42871 SUBJECT: GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift DATE: 25/11/28 14:22:37 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), A. Saccardi (CEA/Irfu), B. Schneider (LAM), M. Dennefeld (IAP), E. Le Floc'h (CEA-Saclay) report on behalf of the MISTRAL GRB collaboration: We carried out observations of the Swift GRB 251126A (Caputo et al., GCN 42843) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 3 exposures of 3 min in the r-band at a midtime of 2025-11-26 22:58 UT corresponding to T-T0 = 3.79 hours. The afterglow reported by Swain et al. (GCN 42844), Lipunov et al. (GCN 42847), Fu et al. (GCN 42848), Reguitti et al. (GCN 42849), Broens et al. (GCN Circ. 42850), Angulo et al. (GCN 42855), Pulido-Torres et al. (GCN 42856), Gupta et al. (GCN 42857), Cotter et al. (GCN 42858), Seki et al. (GCN 42859), Volnova et al. (GCN 42861), Breeveld and Caputo (GCN 42863), Gupta et al. (GCN 42864), Burkhonov et al. (GCN 42866), Maksut et al. (GCN 42868) and Moskvitin et al. (GCN 42870) is very well detected in r’ with a preliminary magnitude of : r’ = 20.1 +/- 0.13 We also obtained 1 exposure of 600s in the g-band at a midtime of 2025-11-27 00:38 UT. The afterglow is only barely visible with an upper magnitude limit of : g’ > 21.9 (S/N=3) The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the STDWeb/STDPipe tools (Karpov 2025), is in the AB system, and is not corrected for Galactic extinction. In addition, a spectrum covering the wavelength range 4200-8000 AA was secured with the MISTRAL spectroscopic blue setting, starting at 23:10 UT (midtime = T0+4.5h) with a total exposure time of 2x1800 s. In a preliminary reduction of the spectrum, a faint trace is detected down to ~5600 AA (in the flux calibrated spectrum), where a spectral break is observed despite the low S/N. If due to Lyman alpha, this would correspond to a redshift of z~3.6. Our spectroscopic value is in agreement with the photometric redshift reported by Angulo et al. (GCN 42855). Given the low S/N over the continuum, we caution that this redshift solution should be considered tentative. We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Stephane Favard, and the SOPHIE observer Felix Savoure. View this GCN Circular online at https://gcn.nasa.gov/circulars/42871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40939] GRB 251126A: further SAO RAS optical observations
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42870 SUBJECT: GRB 251126A: further SAO RAS optical observations DATE: 25/11/28 12:46:09 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), V. S. Shergin (SAO RAS), A. A. Volnova (IKI), A. S. Pozanenko (IKI) report on behalf of IKI-GRB-FuN and GRB follow-up team. We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851; Page et al., GCN 42860) with the Zeiss-1000 1m telescope of the SAO RAS on November 27/28 night. We obtained two series of 300 sec. images in Rc band under a good weather conditions and seeing (FWHM) ~1".5. The optical afterglow (Swain, GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Anguloet al., GCN 42855; Pulido-Torres et al; GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859; Volnova et al., GCN 42861; Breeveld and Caputo, GCN 42863; Gupta et al., GCN 42864; Burkhonov et al., GCN 42866; Maksut et al., GCN 42868) is clearly detected in the stacked frames. The preliminary results are as following. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-11-27 20:20:22 1.07076 11*300 Rc 22.02 0.04 24.1 2025-11-27 23:31:00 1.19809 8*300 Rc 22.24 0.07 23.8 The photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes)and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40938] GRB 250702B: detection of the compact radio counterpart 139 days after the burst
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42869 SUBJECT: GRB 250702B: detection of the compact radio counterpart 139 days after the burst DATE: 25/11/28 12:16:56 GMT FROM: ailing.wang.wal(a)gmail.com Ailing Wang (IHEP), Tao An, Yuanqi Liu (SHAO), Jinjun Geng, Songbo Zhang, Xuefeng Wu (PMO), Xinwen Shu (ANU) et al. report: We are conducting a multi-telescope, multi-epoch, multi-frequency radio campaign on GRB 250702BCD to trace its long-term afterglow evolution. Previous radio observations from other facilities have been reported by independent groups (e.g. GCNs 40983, 40985, 41053, 41059, 41061). Here we report results from Karl G. Jansky Very Large Array (VLA) observations on 2025 November 18 in B-array configuration. The data were calibrated and imaged with standard procedures in CASA. At C band (the central frequency of 6 GHz), we detect a radio source at the position of the known counterpart to GRB 250702B. The source is unresolved with a synthesized beam of 1.42 arcsec × 2.40 arcsec (PA = 28 deg) and has a peak flux density of ≈ 200 μJy beam⁻¹. The measured peak position is RA (J2000) = 18:58:45.5648 Dec (J2000) = -07:52:26.235 which is consistent with previously reported radio positions of the counterpart (GCN 41053). Complementary observations with eMERLIN and the European VLBI Network (EVN) in September yield flux densities consistent with the VLA measurement. This agreement indicates that the bulk of the radio emission, arising from long-lived synchrotron radiation (Levan et al. 2025, O'Connor et al. 2025), remains confined to a compact component on milliarcsecond to sub-arcsecond scales. This late-time detection at approximately 139 days after the 2025 July 2 trigger provides an important additional point on the radio light curve and confirms the persistence of a compact radio source. The full multi-epoch, multi-resolution dataset will be used to characterize the long-lived synchrotron emission and continued long-term monitoring is scheduled. We thank the TACs and operations staff of the VLA, eMERLIN, EVN, and ATCA for approving and supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40937] GRB 251126A NUTTelA-TAO Early Measurements
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42868 SUBJECT: GRB 251126A NUTTelA-TAO Early Measurements DATE: 25/11/28 10:49:00 GMT FROM: Zhanat Maksut at Nazarbayev University <zhanat.maksut(a)nu.edu.kz> Z. Maksut (NU), B. Grossan (UCB, NU), T. Komesh (NU), E. Abdikamalov (NU), M. Krugov (FAI) and D. Berdikhan (NU) The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) pointed at GRB 251126A on receipt of an automated GCN / BAT position alert, observing in Sloan g' and i' bands with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14). Observations started at UT 2025 November 26, 19:11:32, 52 s after the SWIFT/BAT trigger (Caputo et al., GCN 42843). Weather conditions were good within the first 1 hour of observation, but gradually deteriorated to cloudy over the course of the night. A new optical counterpart reported by Swain et al., GCN 42844; Fu et al., GCN 42848; Reguitti et al., GCN 42849; Broens et al., GCN 42850; Angulo et al., GCN 42855; Pulido-Torres et al., GCN 42856; Gupta et al., GCN 42857; Cotter et al., GCN 42858; Seki et al., GCN 42859, was detected. We report the following preliminary, uncorrected, selected photometric values for the optical transient: tc-t0(s) t_exp i'(mag) err(mag) g’(mag) err(mag) -------- ------ ------- -------- 76 48.0 18.12 0.08 19.49 0.06 142 30.0 17.38 0.07 18.96 0.06 322 30.0 17.62 0.08 19.03 0.09 502 30.0 17.88 0.09 19.31 0.08 tc-t0 = trigger time minus image center time. Calibration was done with 5 bright Pan-STARRS catalog stars on our images (see Komesh, T. et al. 2023, MNRAS 520, 6104). We caution the reader that these are preliminary results, without color or other corrections, and will likely change. Please also note that times are approximate. Systematic errors are estimated from previous measurements. We welcome requests for additional data. ---------------------------------- NU = Nazarbayev University, Astana, Kazakhstan UCB = University of California, Berkeley, USA FAI = Fesenkov Astrophysical Institute, Kazakhstan This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP26103591). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan. View this GCN Circular online at https://gcn.nasa.gov/circulars/42868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40936] LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42867 SUBJECT: LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates DATE: 25/11/28 08:15:18 GMT FROM: Mankeun Jeong <jmk5040(a)gmail.com> Mankeun Jeong, Myungshin Im, Seo-Won Chang, Hyeonho Choi (SNU/SNU ARC), Gregory S.-H. Paek (IfA), and Chung-Uk Lee (KASI), on behalf of the GECKO team We observed the S251112cm sky localization region (Updated; GCN 42690) following the LIGO/Virgo/KAGRA trigger. Optical imaging was obtained with the three 1.6-m Korea Microlensing Telescope Network (KMTNet) telescopes at CTIO, SAAO, and SSO, with most of the data taken from SSO. We surveyed the southern portion (decl. < -10 deg) of the S251112cm 90% localization region, covering ~1,012 deg^2 from 2025-11-13 to 2025-11-27. During the first three nights, we obtained R and I imaging with 480 sec total exposure per field (four dithered 120 sec exposures) over ~180 deg^2. For the remainder of the run, observations were conducted in R-band only with the same 480 sec per-field exposure. A fraction of the surveyed area overlaps with regions having KMTNet Synoptic Survey of the Southern Sky (KS4) reference images. Difference image analysis has been completed for ~60 deg^2, with additional processing ongoing. Below we list transient candidates re-identified from TNS and new GECKO sources detected in our imaging. Redshifts are adopted from the GLADE+ host-galaxy associations. Name | RA (deg) | Dec (deg) | R (AB mag) | I (AB mag) | Date-Obs (UTC) | Redshift -----|----------|-----------|------------|------------|-------------------|--------- AT2025aebs | 354.16948 | -33.01666 | 20.42 ± 0.05 | 20.66 ± 0.07 | 2025-11-16T12:24:50 | 0.1642 AT2025adbw | 3.31215 | -36.40843 | 19.07 ± 0.02 | — | 2025-11-14T14:23:37 | — AT2025abnc | 7.50565 | -34.96515 | 19.95 ± 0.05 | 20.54 ± 0.08 | 2025-11-14T12:40:10 | 0.1067 GECKO25dryb | 1.69517 | -33.38614 | 18.95 ± 0.01 | 19.05 ± 0.05 | 2025-11-14T13:39:42 | 0.2094 GECKO25drxk | 1.53192 | -35.03043 | 18.89 ± 0.01 | 18.86 ± 0.03 | 2025-11-14T13:39:42 | 0.2408 GECKO25dulp | 358.59508 | -35.91373 | 19.58 ± 0.06 | 18.65 ± 0.03 | 2025-11-16T13:40:59 | 0.0859 GECKO25dukb | 356.10091 | -34.07094 | 18.37 ± 0.01 | 18.13 ± 0.01 | 2025-11-16T12:24:50 | 0.1269 All newly identified GECKO candidates lie close to the center of the host galaxy, whose redshifts exceed the estimated distance of S251112cm, indicating they are unrelated to the GW event's physical origin. Further difference imaging and transient vetting across the remaining fields are underway. The GECKO network (Im et al. 2023; Paek et al. 2024) operates 0.5–1 m class telescopes worldwide for EM follow-up of gravitational-wave events. KMTNet is operated by the Korea Astronomy and Space Science Institute. We thank the KMTNet staff for their support during these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40935] GRB251126A: MAO/AZT-22 optical observations
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42866 SUBJECT: GRB251126A: MAO/AZT-22 optical observations DATE: 25/11/28 05:08:59 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> O. Burkhonov, Y. Rajabov, B.Abidkhanov, S. Ehgamberdiev, Y. Tillayev (UBAI), T. Boyqobilov, A. Shaymanov (Maidanak Observatory/UBAI) report on behalf of UBAI team. We observed the field of GRB 251126A detected by Swift (Caputo et al. 2025, GCN 42843) ), with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2025-11-27 at 22:17:50 UT, i.e, ~1.13 days after the Swift trigger. In total we obtained 6x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). We stacked the images after the alignment. We detect the optical counterpart in our stacked image within the error box of GIT (Swain et al. 2025, GCN 42844). Our detection is consistent with Swain et al. 2025 (GCN 42844); Lipunov et al. 2025 (GCN 42847); Fu et al. 2025 (GCN 42848); Reguitti et al. 2025 (GCN 42849); Broens et al. 2025 (GCN 42850); Angulo et al. 2025 (GCN 42855); and Torres et al. 2025 (GCN 42856); Gupta et al. 2025 (GCN 42857); Cotter et al. 2025 (GCN 42858); Seki et al. 2025 (GCN 42859); Volnova et al. 2025 (GCN 42861); Breeveld et al. 2025 (GCN 42863); Gupta et al. 2025 (GCN 42864). Preliminary photometry is as follows: Date UTstart Exptime t-T0 Filter OT Err. UL Site/Telescope (nxs) (mid, days) 2025-11-27 22:37:36 6x300 1.144 R 22.14 0.11 22.93 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. The data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) View this GCN Circular online at https://gcn.nasa.gov/circulars/42866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40934] GRB 251128A: Fermi GBM Final Real-time Localization
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42865 SUBJECT: GRB 251128A: Fermi GBM Final Real-time Localization DATE: 25/11/28 04:33:00 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 04:22:21 UT on 28 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251128A (trigger 785996546.612178 / 251128182). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 117.5, Dec = 52.2 (J2000 degrees, equivalent to J2000 07h 49m, 52d 12'), with a statistical uncertainty of 2.0 degrees. The angle from the Fermi LAT boresight is 114.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251128182/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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