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[vsnet-grb-info 40933] GRB251126A: Continued optical observation from 1.3m DFOT
by GCN Circulars 28 Nov '25

28 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42864 SUBJECT: GRB251126A: Continued optical observation from 1.3m DFOT DATE: 25/11/28 01:22:33 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Debalina Kar, Pankaj Pawar, and Kuntal Misra (ARIES) report: We observed the field of GRB 251126A detected by Swift (Caputo et al. 2025, GCN 42843) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-11-27 at 18:10:19 UT, i.e., ~22.99 hours after the Swift trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. 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). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-27 18:10:19 ~22.99 R 300*12 21.62+/- 0.02 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). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40932] GRB 251126A: Swift/UVOT Detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42863 SUBJECT: GRB 251126A: Swift/UVOT Detection DATE: 25/11/27 14:51:12 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and R. Caputo (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251126A 86s after the BAT trigger (Caputo et al., GCN Circ. 42843). The fading optical afterglow (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 and Volnova et al., GCN 42861) is clearly detected in the initial UVOT exposures. The non detection in the U and UV filters is consistent with the redshift of z=3.5 found by Angulo et al., (GCN Circ. 42855). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposures and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 86 236 147 20.0 ± 0.1 white 579 772 39 20.3 ± 0.3 white 880 1377 186 20.5 ± 0.2 u_FC 299 548 246 >20.4 v 629 1080 58 18.7 ± 0.3 b 1159 1352 39 19.4 ± 0.3 uvw1 853 1467 35 >18.32 uvm2 653 847 39 >18.00 uvw2 778 1402 58 >18.70 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.063 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40931] EP251124a: Pan-STARRS ri-band imaging and photometry
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42862 SUBJECT: EP251124a: Pan-STARRS ri-band imaging and photometry DATE: 25/11/27 13:50:26 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> J. H. Gillanders (Oxford), M. Huber, K. C. Chambers (IfA, Univ. Hawaii), S. J. Smartt, K. W. Smith (Oxford/QUB), S. Srivastav (Oxford), M. Nicholl, D. Young, M. Fulton (QUB), T.-W. Chen (NCU, Taiwan) A. S. B. Schultz, T. de Boer, J. Fairlamb, G. Paek, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii). We observed the optical counterpart of EP251124a (Zhou et al., GCN 42816), using the Pan-STARRS telescope system (Chambers et al., 2016, arXiv e-prints, 1612.05560) on MJD 61004.36 (2025-11-25 08:38:24 UTC), 0.90 days after the EP-WXT detection (Zhou et al., GCN 42816). The Pan-STARRS system consists of 2x1.8m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy, and a broad w filter, which is a composite of the gri filters. Our observation consisted of 6x150s exposures in both the r and i filters with Pan-STARRS1. The images were processed with the Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target stacked images (Magnier et al., 2020a, ApJS, 251, 3; Magnier et al., 2020b, ApJS, 251, 6; Waters et al., 2020, ApJS, 251, 4). From these difference images, we do not detect any optical counterpart down to 3.5-sigma limiting AB magnitudes of r~22.3 and i~22.3. Our upper limits are in agreement with previously reported limits from Mohan et al. (GCN 42817), Wang et al. (GCN 42824), Lipunov et al. (GCN 42828), van Hoof et al. (GCN 42829), and Ma et al. (GCN 42833). View this GCN Circular online at https://gcn.nasa.gov/circulars/42862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40930] GRB 251126A: Mondy and SAO RAS optical observations
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42861 SUBJECT: GRB 251126A: Mondy and SAO RAS optical observations DATE: 25/11/27 13:38:15 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. S. Moskvitin (SAO RAS), V. P. Goranskij (SAI MSU, SAO RAS), E. Klunko (ISTP), V. S. Shergin (SAO RAS), N. Pankov (HSE, IKI), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the Swift GRB 251126A (Caputo et al., GCN 42843; Evans, GCN 42845; Goad et al., GCN 42851) with the AZT-33IK 1.5m telescope of the Sayan Solar Observatory (Mondy) in R-band and the Zeiss-1000 1m telescope of the SAO RAS in Rc-band on November 26/27 night. Observations with the AZT-33IK started at 20:35:11 UT (1.4097 hours after the trigger), observations with the Zeiss-1000 started at 21:31:39 UT (2.3508 hours after the trigger). 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) is clearly detected in individual frames. Preliminary photometry is given below. Date UT start t-T0 Exp. Filter OT Err. UL Seeing" Site/Instrum (mid,days) (n*s) (3sigma) 2025-11-26 20:35:11 0.06221 5*120 R 19.99 0.08 21.1 5.0 Mondy/AZT-33IK 2025-11-26 20:45:12 0.07125 8*120 R 19.84 0.07 21.4 5.0 Mondy/AZT-33IK 2025-11-26 21:01:12 0.08584 13*120 R 19.89 0.06 21.7 5.0 Mondy/AZT-33IK 2025-11-26 21:31:39 0.10164 2*300 Rc 19.81 0.08 21.2 2.2 SAO/Zeiss-1000 2025-11-26 21:58:22 0.12230 3*300 Rc 19.95 0.03 22.7 2.0 SAO/Zeiss-1000 2025-11-27 01:14:02 0.25960 2*600 Rc 20.63 0.04 23.2 1.6 SAO/Zeiss-1000 2025-11-27 01:57:56 0.29372 3*600 Rc 20.62 0.03 23.4 1.6 SAO/Zeiss-1000 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/42861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40929] GRB 251126A: Swift-XRT refined Analysis
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42860 SUBJECT: GRB 251126A: Swift-XRT refined Analysis DATE: 25/11/27 13:02:50 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> K.L. Page (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.2 ks of XRT data for GRB 251126A, from 66 s to 56.7 ks after the trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.5 (+0.6, -0.5). At T+210 s the decay flattens to an alpha of -0.50 (+0.00, -0.17) before breaking again at T+1954 s to a final decay with index alpha=1.13 (+0.21, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.11 (+0.25, -0.24). The best-fitting absorption column is 1.7 (+0.8, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 9.5 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.3 x 10^-11 (4.6 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 9.5 x 10^20 cm^-2 Excess significance: 1.8 sigma Photon index: 2.11 (+0.25, -0.24) If the light curve continues to decay with a power-law decay index of 1.13, the count rate at T+24 hours will be 8.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-13 (3.9 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/01417793. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40928] GRB 251126A : MITSuME Akeno optical afterglow candidate detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42859 SUBJECT: GRB 251126A : MITSuME Akeno optical afterglow candidate detection DATE: 25/11/27 12:08:00 GMT FROM: seki(a)hp.phys.titech.ac.jp H. Seki, I. Takahashi, M. Sasada, Y. Kubo, H. Hagio, A. Ochi, R. Kato, S. Joshima, Y. Yatsu and N. Kawai (Science Tokyo) report on behalf of the MITSuME collaboration: We observed the field of GRB 251126A detected by Swift (Caputo et al., GCN 42843) with the optical three-color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50-cm telescope Akeno. The observation started at 2025-11-26 19:11:15 UT (39 seconds after the trigger). We stacked the images taken under good conditions. We detected a point source in the g'-, Rc- and Ic-band images at a position of the reported optical candidate (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). Here we report the magnitudes of the source as follows. T0+[sec] | MID-UT | T-EXP[sec] | magnitudes --------------------------------------------------------------------------------------------------------------- 1310 | 2025-11-26 19:32:26 | 1560 | g'=20.5+/-0.3, Rc=18.7+/-0.1, Ic=18.2+/-0.1 --------------------------------------------------------------------------------------------------------------- T0+ : Elapsed time after the trigger T-EXP: Total exposure time We used the PS1 catalog for flux calibration. The catalog magnitudes in PS1 g, r and i bands were converted to our g', Rc and Ic band magnitudes following Tonry et al. (2012), Table 6. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ; https://github.com/MNiwano/Eclaire) View this GCN Circular online at https://gcn.nasa.gov/circulars/42859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40927] GRB 251126A: NOT optical observations
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42858 SUBJECT: GRB 251126A: NOT optical observations DATE: 25/11/27 11:11:11 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> L. Cotter (UCD), A. Martin-Carrillo (UCD), S.Y. Fu (HUST), J. An (NAOC), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), T. Pursimo (NOT) report on behalf of a larger collaboration: We observed the optical afterglow of GRB 251126A (Caputo et al., GCN 42843) with the Nordic Telescope (NOT) equipped with the ALFOSC Camera. We obtained 3x300s r-band images with observations starting on 2025-11-26 at 23:31:36 UTC, under good seeing (~1”). However, unfortunately, observations had to be interrupted due to adverse weather conditions. The optical counterpart 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 42850), Angulo et al. (GCN 42855), Torres et al. (GCN 42856) and Gupta et al. (GCN 42857) is well detected in our stacked image with an AB magnitude of r = 20.72 ± 0.05 at a mid epoch of 2025-11-26 23:34:06.554 (4.4 hr after the Swift/BAT trigger). This magnitude was calibrated against nearby objects from the Pan-STARRS catalog and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40926] GRB 251126A: 1.3m DFOT optical afterglow detection
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42857 SUBJECT: GRB 251126A: 1.3m DFOT optical afterglow detection DATE: 25/11/27 08:14:19 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Dhruv Jain, Pankaj Pawar, Debalina kar and Kuntal Misra (ARIES) report: We observed the field of GRB 251126A detected by Swift (Caputo et al. 2025, GCN 42843) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-11-26 at 22:17:19 UT, i.e., ~3.11 hour after the Swift trigger. We have taken multiple frames with an exposure time of 300s in the I filter. 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). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude ====================================================================== 2025-11-26 22:17:19 ~3.11 I 300*12 19.41+/- 0.01 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). 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 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40925] GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42856 SUBJECT: GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory DATE: 25/11/27 06:40:21 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> M. Pulido-Torres, J. Basurto Merino, P.G. Berdayes, A. Caballero-Almagro, A. Cerón, M. Contreras, F. Díaz-Segado, T. Ferrer-Laviña, B. Gandolfi, V. Ghiraldo, J. Hernández Fung, L. Juliá-Maroto, E. Lekaroz-Urriza, M. Manzano García, E. Mejía-Martínez, J. Prieto Polo, M. Quintana-Ansaldo, A. Schenone-Zanuzzi, A. Selezneva, T. Tundidor Rodríguez, E. Urquijo-Rodríguez (all ULL), M. Abdul-Masih (IAC and ULL), and I. Pérez-Fournon (IAC and ULL). Following the detection of the Swift GRB 251126A (Caputo et al., GCN Circ. 42843; Evans et al., GCN Circ. 42845; and Goad et al., GCN Circ. 42851), 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 McDonald Observatory, Texas. The observation, a single exposure of 300 sec in the SDSS r' filter, started on 2025-11-27 at 04:41:19 UT, about 9.51 hours after the Swift trigger. The optical counterpart first detected by the GROWTH-India Telescope (GIT) (Swain et al., GCN Circ. 42844) is clearly detected in our image with a magnitude of r' = 20.86 +/- 0.13 (AB), calibrated against PanSTARRS-1 DR2 stars and not corrected for Galactic extinction. Our result is consistent with other optical observations: Swain et al. (GCN Circ. 42844), Lipunov et al. (GCN Circ. 42847), Fu et al. (GCN Circ. 42848), Reguitti et al. (GCN Circ. 42849), Broens et al. (GCN Circ. 42850), and Angulo et al. (GCN Circ. 42855). This work makes use of observations from the Las Cumbres Observatory global telescope network (LCO program IAC2025B-010). These observations are part of a course in Astrophysical Techniques of the Master in Astrophysics of the Astrophysics Department of the University of La Laguna in collaboration with the Instituto de Astrofísica de Canarias (La Laguna, Tenerife, Canary Islands, Spain). 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/42856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40924] GRB 251126A: COLIBRÍ photometric redshift z = 3.5
by GCN Circulars 27 Nov '25

27 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42855 SUBJECT: GRB 251126A: COLIBRÍ photometric redshift z = 3.5 DATE: 25/11/27 04:57:59 GMT FROM: Camila Angulo Valdez at UNAM <camiangulo(a)astro.unam.mx> Camila Angulo (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), 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), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Swift GRB 251126A (Caputo et al., GCN Circ. 42843) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-11-27 02:49 to 04:14 UTC (from 7.6 to 9.1 hours after the trigger) and obtained, respectively, 10, 27, 11, 23, and 23 minutes of exposure in the g, r, i, z, and y filters. The data were reduced, coadded, and analyzed with the ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Swain et al. (GCN Circ. 42844), Lipunov et al. (GCN Circ. 42847), Fu et al. (GCN Circ. 42848), Reguitti et al. (GCN Circ. 42849), and Broens et al. (GCN Circ. 42850) at preliminary magnitudes of: r = 20.62 +/- 0.05 z = 19.86 +/- 0.07 In our data, we see a clear break in the spectrum in g. After correcting for the Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.063 mag (Schlafly & Finkbeiner 2011) and fitting a power-law model to the grizy-bands with SMC extinction, we derive a photometric redshift of z = 3.52 (+0.18, -0.20, 1-sigma confidence interval). Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. 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/42855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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