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[vsnet-grb-info 41213] GRB 251214B: VLT/X-shooter observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43131 SUBJECT: GRB 251214B: VLT/X-shooter observations DATE: 25/12/15 17:56:34 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> A. de Ugarte Postigo (LAM), D. B. Malesani (DAWN/NBI and Radboud), M. Garnichey (LUX-Paris Obs.), J. An (NAOC), G. Corcoran (UCD), L. Izzo (INAF/OACn & DARK/NBI), A. Martin-Carrillo (UCD), A. Saccardi (CEA/Irfu), A. L. Thakur (INAF/IAPS), A. Torralba (ISTA) and Y. Ma (Princeton U.) report on behalf of the Stargate collaboration: We observed the optical counterpart of GRB 251214B detected by Fermi (Fermi GBM team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089) and GECAM-B (Luo et al., GCN 43113) with X-shooter mounted on the UT3 (Melipal) of ESO’s Very Large Telescope (Paranal Observatory, Chile). Observations were conducted in twilight and at large airmass. The acquisition images, which started at 00:46:54 UT of 15 Dec 2025 (15.74 hr after the burst onset) show the counterpart with the following photometry (AB magnitudes), as compared to field stars from the SDSS catalogue: g = 23.15 +/- 0.06 r = 22.19 +/- 0.04 z = 20.76 +/- 0.05 A 2x600 s spectrum followed, covering the spectral range between 3000 and 21000 AA. The spectrum shows a red continuum, consistent with the photometry, only detectable above 6000 AA, and more prominent at infrared wavelengths. We do not detect clear emission features from the underlying host galaxy (mentioned by Gress et al., GCN 43095 and Watson et al., GCN 43103), which prevents us from measuring its redshift. We note that the Legacy Survey reveals that the source underlying the afterglow is composed of two blobs, a fainter one right under the GRB and a brighter one towards the North East, at a distance of 1". The slight difference between our photometry and the one of COLIBRÍ (Watson et al., GCN 43103) could be due to the different contribution of these underlying sources within the photometric aperture. We acknowledge expert support from the ESO observing staff in Paranal, in particular Claudia Paladini, Célia Desgrange, Cecila Bustos, and Ana Jimenez-Gallardo. View this GCN Circular online at https://gcn.nasa.gov/circulars/43131. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41212] GRB 251213A: GRID-10B observation
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43130 SUBJECT: GRB 251213A: GRID-10B observation DATE: 25/12/15 16:43:28 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> Xiao-Fan Pan, Long-Hao Li, Chen-Yu Wang, Zi-Rui Yang report on behalf of the GRID Collaboration: GRID reports the detection of GRB 251213A, a long-duration gamma-ray burst. The event triggered GRID-10B at T0 = 2025-12-13 12:30:04 UTC. The measured burst duration (10B) is T90 = 35.5 ± 3.2 s in the 30–2000 keV energy range. The event was also detected by GRID-11B (GCN #43116), GECAM-B (GCN #43106), SVOM/GRM (GCN $43111), and AstroSat CZTI (GCN #43108). The GRID light curves for this event are available at https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB251213A/GRID_GRB…. GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43130. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41211] GRB 251214B: Swift-BAT refined analysis
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43129 SUBJECT: GRB 251214B: Swift-BAT refined analysis DATE: 25/12/15 16:41:36 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), R. A. J. Eyles-Ferris (U Leicester), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 251214B (trigger #1423875) (Eyles-Ferris, et al., GCN Circ. 43089). The BAT ground-calculated position is RA, Dec = 330.222, -9.155 deg which is RA(J2000) = 22h 00m 53.4s Dec(J2000) = -09d 09' 17.3" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 99%. The mask-weighted BAT light curve shows a double-peaked structure with a duration of about 10 sec T90 (15-350 keV) is 9.38 +- 0.73 sec (estimated error including systematics). The time-averaged spectrum from T-0.19 to T+9.97 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.79 +- 0.12. The fluence in the 15-150 keV band is 5.0 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T-0.13 sec in the 15-150 keV band is 2.0 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1423875 View this GCN Circular online at https://gcn.nasa.gov/circulars/43129. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41210] GRB 251202A: radio detection with the VLA
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43128 SUBJECT: GRB 251202A: radio detection with the VLA DATE: 25/12/15 16:38:56 GMT FROM: Stefano Giarratana at INAF-OAB <s.giarratana(a)ira.inaf.it> S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA), G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.), N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB), L. Nava (INAF-OAB) At 12:00:00 UT on 2025 December 5 (T_mid = 3.45 days post-burst) the Karl G. Jansky VLA observed the field of GRB 251202A / EP251202A (Fermi GBM team, GCN 42933, 42957; Einstein Probe team, GCN 42937, GCN 42946; AstroSat CZTI collaboration, GCN 42967; Insight-HXMT team, GCN 42970; SVOM team, GCN 42997) in three bands, with central frequencies of 6, 10 and 15 GHz. The standard 3C286 was used as bandpass and flux density calibrator, while J0818+4222 was used as phase calibrator. From a preliminary analysis, an unresolved radio source is detected at a position (J2000): RA: 08:08:27.466 +- 0.001 Dec: +40:36:44.70 +- 0.01 consistent with the X-ray (Einstein Probe team, GCN 42937; Swift-XRT team, GCN 42943) and optical (GOTO collaboration, GCN 42947; Quirola-Vasquez, GCN 42948; Swift/UVOT team, GCN 42956; KAIT GRB team, GCN 42964; SVOM/VT team, GCN 42966; Bochenek et al., GCN 42977; Contreras et al., GCN 42999) position of the transient. The preliminary analysis yields the following results: ================================================================ T_mid Freq Peak r.m.s. Beam PA [days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg] ================================================================ 3.45 6 111 10 1.08x1.02 57 3.45 10 169 7 0.71x0.60 59 3.45 15 310 8 0.45x0.42 34 ================================================================ No source is detected with a >3sigma confidence level at the aforementioned position in the VLASS. However, the r.m.s. noise level of the survey at the GRB location is approximately 130 uJy/b. We would like to thank the staff of the VLA for approving, executing, and processing the observations. The National Radio Astronomy Observatory is a facility of the National Science Foundation operated under cooperative agreement by Associated Universities, Inc. These observations were carried out as part of project SF181027, approved in the framework of the Fermi - NRAO joint program agreement. View this GCN Circular online at https://gcn.nasa.gov/circulars/43128. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41209] EP251214b: Global MASTER-Net observations report
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43127 SUBJECT: EP251214b: Global MASTER-Net observations report DATE: 25/12/15 16:09:37 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) was pointed to the EP251214b ( EP Team et al., GCN 43125) errorbox 1777 sec after trigger time at 2025-12-14 07:49:59 UT, with upper limit up to 20.5 mag. The observations began at zenith distance = 14 deg. The sun altitude is -17.5 deg. The galactic latitude b = 22 deg., longitude l = 256 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3071744 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1807 | 2025-12-14 07:49:59 | MASTER-OAFA | (09h 37m 50.45s , -22d 35m 38.5s) | C | 60 | 20.5 | 1873 | 2025-12-14 07:51:04 | MASTER-OAFA | (09h 37m 50.56s , -22d 35m 35.8s) | C | 60 | 20.5 | 1939 | 2025-12-14 07:52:10 | MASTER-OAFA | (09h 37m 50.68s , -22d 35m 33.3s) | C | 60 | 20.5 | 2004 | 2025-12-14 07:53:16 | MASTER-OAFA | (09h 37m 50.79s , -22d 35m 30.8s) | C | 60 | 20.4 | 2070 | 2025-12-14 07:54:22 | MASTER-OAFA | (09h 37m 50.91s , -22d 35m 28.4s) | C | 60 | 20.4 | 2137 | 2025-12-14 07:55:28 | MASTER-OAFA | (09h 37m 51.00s , -22d 35m 26.1s) | C | 60 | 20.5 | 2202 | 2025-12-14 07:56:34 | MASTER-OAFA | (09h 37m 51.12s , -22d 35m 23.9s) | C | 60 | 20.4 | 2268 | 2025-12-14 07:57:39 | MASTER-OAFA | (09h 37m 51.21s , -22d 35m 21.8s) | C | 60 | 20.5 | 2334 | 2025-12-14 07:58:45 | MASTER-OAFA | (09h 37m 51.29s , -22d 35m 19.7s) | C | 60 | 20.5 | 2399 | 2025-12-14 07:59:51 | MASTER-OAFA | (09h 37m 51.36s , -22d 35m 17.2s) | C | 60 | 20.4 | 2465 | 2025-12-14 08:00:57 | MASTER-OAFA | (09h 37m 51.42s , -22d 35m 15.1s) | C | 60 | 20.5 | 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/43127. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41208] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43126 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:57:54 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. 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/43126. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41207] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43125 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:56:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. 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/43125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41206] EP251214b : Einstein Probe detection of a fast X-ray transient
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43125 SUBJECT: EP251214b : Einstein Probe detection of a fast X-ray transient DATE: 25/12/15 15:56:40 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. H. Jiang (NJU), Y.-H. I. Yin (HKU), Y. Q. Zhao (PRIC,USTC), W. F. Wen (SZTU), H. Q. Cheng, and H. Sun (NAOC) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251214b. The transient triggered EP-WXT (ID: 01709250023) at 2025-12-14T07:20:22 (UTC), and followed by COLIBRÍ telescope and LCO (GCN 43090, GCN 43117). Ground analysis shows that the WXT position of the source is R.A. = 144.358 deg, DEC = -22.884 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). Due to the earth occultation, the WXT data only shows the decay of a flare starting from 2025-12-14T07:19:13.9 and lasts for around 120 s, with a peak flux of ~2 x 10^-9 erg/s/cm^2. The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 4.02 x 10^20 cm^-2 and a photon index of 1.5 (-/+0.3). The derived average absorbed 0.5-4 keV flux is 1.1 (-/+0.2) x 10^-9 erg/s/cm^2. We also note that EP251214b was only detected from ground analysis after restoring the data during the period of earth occultation, which leads to some delays in the analysis as well as the issuing. 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/43125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41205] GRB 251214B: AbAO optical observations
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43124 SUBJECT: GRB 251214B: AbAO optical observations DATE: 25/12/15 14:54:17 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), R. Ya. Inasaridze (AbAO), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the long GRB 251214B detected by Fermi (Fermi team, GCN 43088), Swift (Eyles-Ferris et al., GCN 43089; Evans et al., GCN 43098; Kuin and Eyles-Ferris, GCN 43105; Burrows et al., GCN 43112), and GECAM-B (Luo et al., GCN 43113) with the AS-32 0.7m telescope of Abastumani Observatory (AbAO) taking several frames in R-band. The observations started on Dec. 14 at 15:00 UT, i.e., ~ 6 hours after the Swift/BAT trigger. In the stacked image we detect the optical afterglow reported previously (Eyles-Ferris et al., GCN 43089; Kang et al., GCN 43093; Gress et al., GCN 43095; Fu et al., GCN 43097; Gupta et al., GCN 43100; Watson et al., GCN 43103; Kuin and Eyles-Ferris, GCN 43105; Pérez-Fournon et al., GCN 43123). Preliminary photometry and observational details are the following: Date UT start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2025-12-14 15:00:25 0.27325 51*60 R 20.6 0.2 20.7 AbAO/AS-32 The photometry is based on several 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/43124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41204] GRB 251214B: LCO detection of the optical counterpart
by GCN Circulars 15 Dec '25

15 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43123 SUBJECT: GRB 251214B: LCO detection of the optical counterpart DATE: 25/12/15 14:21:49 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon (IAC and ULL), F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia, E. Lekaroz-Urriza, M. Quintana-Ansaldo (all ULL), and A. López-Oramas (IAC and ULL) Following the detection of the long GRB 251214B, detected by Fermi GBM (Fermi GBM team, GCN #43088), Swift BAT, XRT, and UVOT (Eyles-Ferris et al., GCN #43089; Evans et al., GCN #43098; Kuin and Eyles-Ferris, GCN #43105; and Burrows et al., GCN #43112), and GECAM-B (Luo et al., GCN #43113), we observed the field with one of the two Las Cumbres Observatory (LCO) 1-m telescopes equipped with Sinistro cameras located at the LCO node at Siding Spring Observatory near Coonabarabran, New South Wales, Australia. The observation, a single exposure of 60 sec in the SDSS r' filter, started on 2025-12-14 at 10:26:57 UT, about 1.41 hours after the Fermi, Swift, and GECAM-B triggers. The optical counterpart first detected by Swift UVOT (Eyles-Ferris et al., GCN #43089) is clearly detected in our image with a preliminary magnitude of r' = 19.18 +/- 0.10, calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical and UV detections (Eyles-Ferris et al., GCN 43089; Kang et al., GCN #43093; Gress et al., GCN #43095; Fu et al., GCN #43097; Gupta et al., GCN #43100; Watson et al., GCN #43103; and Kuin and Eyles-Ferris, GCN #43105). Our preliminary photometry is not corrected for the light of the likely host galaxy discussed by Gress et al. (GCN #43095), and Watson et al. (GCN #43103) at a photometric redshift of z = 0.709 +/- 0.078 (Duncan, 2022). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-008, SGLF and Superluminous Supernovae surveys). This work made use of the Astro-COLIBRI platform (P. Reichherzer et al. 2021, ApJS, 256, 5). View this GCN Circular online at https://gcn.nasa.gov/circulars/43123. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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