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[vsnet-grb-info 42868] EP260527a/GRB 260527A: optical upper limit with Kinder observations
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44739 SUBJECT: EP260527a/GRB 260527A: optical upper limit with Kinder observations DATE: 26/05/29 15:40:44 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> K. N.-T. Ho, A. Aryan, T.-W. Chen, W.-J. Hou, H.-Y. Hsiao (all NCU), A. K. H. Kong (NTHU), S. J. Smartt, J. Gillanders (both Oxford), S. Yang(HNAS), Y.-H. Lee, A. Sankar.K, M.-H. Lee, A. Dutta, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, C.-S. Lin, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, K. W. Smith, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP260527a (Yang et al., GCN 44718, GCN 44725; Svinkin, GCN 44722; Yu et al., GCN 44724; Kawakubo et al., GCN 44726; Wang et al., GCN 44735) using the 1m LOT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86). The first SLT epoch of observations started at 16:02 UTC on 28th May 2026 (MJD 61188.6683), 33.71 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. Neither in the individual frames nor in the stacked frame did we detect the reported optical/NIR counterpart candidate (Aguilar-Ruiz et al., GCN 44719; Li et al., GCN 44720; Mo et al., GCN 44727; Busmann et al., GCN 44728; Corcoran et al., GCN 44729; Kabir et al., GCN 44730; O'Connor et al., GCN 44731; Yang et al., GCN 44736). The details of the observations and measured PSF magnitude with template subtraction (in the AB system) of the possible counterpart of EP260507a are as follows: -------------------------------------------------------------------------------------------------- Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61188.6683 | 33.71 | 120 * 15 | >21.1 | 1".24 | 2.02 The presented magnitudes are calibrated using the field stars from the Pan-STARRS catalogue. The reported upper limit is not corrected for an expected galactic extinction of A_r = 0.04 mag, in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/44739. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42867] GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44738 SUBJECT: GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate DATE: 26/05/29 15:17:32 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Enrique Moreno Méndez (UNAM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), 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), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We reimaged the field of GRB 260429B / EP260429a (Wang et al., GCN Circ. 44426, Arya et al., GCN Circ. 44443) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-05-27 06:34 to 08:42 UTC (from 27.7 to 27.8 days after the trigger) and obtained 1.57 hours of exposure in the r and z filters. The data were reduced and coadded with the ASU COLIBRÍ pipeline and analysed 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. By comparing these observations with our first epoch reported by Fortin et al. (GCN Circ. 44434), we found that an uncatalogued optical source located at: RA (J2000) = 240.58812 (16:02:21.15) Dec (J2000) = -9.60116 (-09:36:04.2) and with an uncertainty of 0.5”, is no longer detected in this second epoch down to the following (3-sigma) limits: r > 23.90 z > 23.07 In our first epoch, for this source, we measured: r = 21.95 +/- 0.05 z = 21.08 +/- 0.04 Given the fading nature of the source, the spatial coincidence with the source EPF J160221.2-093607 reported in by the EP team (Wang et al., GCN Circ. 44445), and the absence of any known minor planet at this position, we suggest this is the optical counterpart of GRB 260429B / EP260429a. 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/44738. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42866] GRB 260529A: GOTO tentative optical afterglow candidate
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44737 SUBJECT: GRB 260529A: GOTO tentative optical afterglow candidate DATE: 26/05/29 12:21:36 GMT FROM: Nusrin Habeeb at University of Leicester <nh312(a)leicester.ac.uk> N. Habeeb, A. Kumar, D. O’Neill, R. Starling, B. Gompertz, G. Ramsay, S. Belkin, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, M. Pursiainen, on behalf of the GOTO collaboration We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the Fermi/GBM detected GRB 260529A (fermi_801715802, Fermi GBM team, GCN 44733). Observations covering the GBM localization began at 2026-05-29 03:00:27 UT (+0.18h post trigger) and continued through to 2026-05-29 04:55:50 UT(+2.10 h post trigger). Images consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline (Lyman et al. 2026) and difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. A new optical transient, GOTO26fez (AT 2026nuz), is identified within the 90% localization region of the Fermi/GBM trigger. The source was detected in the GOTO L-band with magnitudes of 17.85 ± 0.06 and 17.90 ± 0.04 AB mag at +0.23 h and +1.3 h post-trigger, respectively. We would like to caution that, given the source location close to the Galactic plane, we cannot exclude the possibility that the transient is of Galactic origin, such as a stellar flare or a CV. We find no evidence of this source prior to the GRB trigger time in previous GOTO observations, in the archival ATLAS forced photometry server (Shingles et al. 2021) to a magnitude limit of m_o > 18.06 AB mag ~26.3h prior to the trigger, nor in archival ZTF observations provided by the Lasair broker (Smith et al. 2019). We note, however, that the most recent pre-trigger observations from GOTO were obtained approximately one month prior to the burst, and therefore do not provide constraints on shorter-timescale pre-burst variability. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44737. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42865] GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44736 SUBJECT: GRB 260527A/EP260527a: VLT/X-shooter tentative redshift DATE: 26/05/29 10:15:04 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Y.-H. Yang, E. Troja, M. El Kabir (U Rome) report on behalf of the ERC BHianca team: We observed the field of EP260527a (Yang et al., GCN 44718), likely associated with the short GRB 260527A (Svinkin et al., GCN 44722, Yu et al., GCN 44724; Kawakubo et al., GCN 44726, Wang et al., GCN 44735) with the X-shooter spectrograph on the ESO Very Large Telescope (VLT). Observations were performed beginning at 41 hours after the GRB trigger, at an average airmass of 1.3 and in excellent conditions. Our spectra cover the wavelength range 3000-25000 AA, and consist of 4x600 s exposures. Using a nearby bright star for blind offsets, we placed the 1 arcsec slit at the position of the optical counterpart (Aguilar-Ruiz et al., GCN 44719; Li et al., GCN 44720; Busmann et al.44728; Corcoran et al. GCN 44729, El Kabir et al. GCN 44730, O’Connor et al. GCN 44731). Based on a preliminary analysis, we report the identification of weak emission features consistent with the [OII] 3727 doublet at z ~ 0.80, which we propose as the tentative redshift of the EP transient and its underlying host galaxy. Further observations to confirm this value are planned. We thank the staff at the VLT for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44736. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42864] GRB 260527A/EP260527a: Insight-HXMT detection
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44735 SUBJECT: GRB 260527A/EP260527a: Insight-HXMT detection DATE: 26/05/29 03:21:07 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Zheng-Hang Yu, Shao-Lin Xiong, Cheng-Kui Li, and Chao Zheng report on behalf of the Insight-HXMT team: At 2026-05-27T06:16:10.000 (T0), Insight-HXMT/HE detected the short burst GRB 260527A/EP260527a, which is also detected by Konus-Wind (D. Svinkin et al., GCN#44722), GECAM-B (Yu et al., GCN #44724), and EP (Yang et al., GCN # 44718). The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 0.50 +0.30/-0.11 s. The total counts from this burst is 721 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260527A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/44735. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42863] Fermi GRB 260529A: Global MASTER-Net observations report
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44734 SUBJECT: Fermi GRB 260529A: Global MASTER-Net observations report DATE: 26/05/29 03:17:39 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), M. Segura, 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 260529A ( Fermi GBM team, GCN 44733) errorbox 564 sec after notice time and 606 sec after trigger time at 2026-05-29 03:00:04 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 74 deg. The sun altitude is -66.9 deg. The galactic latitude b = -25 deg., longitude l = 28 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3345808 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 666 | 2026-05-29 03:00:04 | MASTER-OAFA | (20h 10m 08.98s , -15d 23m 33.3s) | C | 120 | 17.3 | 807 | 2026-05-29 03:02:10 | MASTER-OAFA | (20h 10m 09.05s , -15d 23m 24.1s) | C | 150 | 17.5 | 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/44734. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42862] GRB 260529A: Fermi GBM Final Real-time Localization
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44733 SUBJECT: GRB 260529A: Fermi GBM Final Real-time Localization DATE: 26/05/29 03:00:37 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 02:49:57 UT on 29 May 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260529A (trigger 801715802.916756 / 260529118). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 302.8, Dec = -15.3 (J2000 degrees, equivalent to J2000 20h 11m, -15d 18'), with a statistical uncertainty of 4.2 degrees. The angle from the Fermi LAT boresight is 90.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260529118/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260529118/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260529118/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44733. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42861] EP250526a: SVOM/VT optical upper limits
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44732 SUBJECT: EP250526a: SVOM/VT optical upper limits DATE: 26/05/29 02:52:08 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> J. R. Xu, H. L. Li, C. Wu, Y. L. Qiu, L. P. Xin, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC) and J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations to the field of EP260526a triggered by Einstein Probe (Yang et al., GCN 44712). The observation started at 2026-05-27T05:44:54 UTC, 20.022 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No uncatalogued sources were detected in stacked images within the error box of EP-FXT (Yang et al, GCN 44721) and EP-WXT (Yang et al, GCN 44712), compared to the Legacy Survey. The 3 sigma limit magnitudes are derived as follows: Mid time | Band | Exposure Time | 3 sigma upper limit 21.53 h VT_B 57*50 s > 23.5 mag 21.53 h VT_R 57*50 s > 23.3 mag Our non-detection is consistent with the observations from COLIBRÍ (Becerra et al., GCN 44710) and LCO (van Hoof et al., GCN 44713). The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/44732. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42860] GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44731 SUBJECT: GRB 260527A/EP260527a: Gemini GMOS-S Optical Observations DATE: 26/05/29 02:17:48 GMT FROM: Brendan O'Connor at Carnegie Mellon University <boconno2(a)andrew.cmu.edu> Brendan O'Connor (CMU), Malte Busmann (LMU), Julius Gassert (LMU/CMU), Daniel Gruen (LMU), Xander Hall (CMU), and Antonella Palmese (CMU) report: We observed the counterpart of GRB 260527A/EP260527a (Yang et al., GCN 44718; Aguilar-Ruiz et al., GCN 44719; Li et al., GCN 44720; Svinkin et al., GCN 44722; Yu et al., GCN 44724; Yang et al., GCN 44725; Kawakubo et al., GCN 44726; Mo et al., GCN 44727) using the GMOS-S instrument mounted on the Gemini-South telescope. Our observations were carried out in the r and i filters for 10x90 s exposure in each band. At the location of the optical counterpart (Aguilar-Ruiz et al., GCN 44719), we detect a source with magnitude i = 23.2 +/- 0.1 AB mag, consistent with recent reports (Busmann et al., GCN 44728; Corcoran et al., GCN 44729; El Kabir et al., GCN 44730). The photometry is calibrated against the PS1 catalog and is not corrected for the minimal Galactic extinction along the line of sight. We thank the Gemini staff, in particular Aleksandar Cikota, for the rapid scheduling and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44731. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42859] EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart
by GCN Circulars 29 May '26

29 May '26

TITLE: GCN CIRCULAR NUMBER: 44730 SUBJECT: EP260527a / GRB 260527A: VLT detection of the optical and nIR counterpart DATE: 26/05/29 02:09:56 GMT FROM: Massine El Kabir <m.elkabir(a)campus.unimib.it> M. El Kabir, Y. Yang and E. Troja (U Rome) report on behalf of the ERC BHianca team: We observed the field of EP260527a (Yang et al., GCN 44718), likely associated with the short GRB 260527A (Svinkin et al., GCN 44722, Yu et al., GCN 44724; Kawakubo et al., GCN 44726), with the FORS2 and HAWK-I on the ESO Very Large Telescope (VLT). Observations started about 41.4 hrs after the GRB trigger and were performed at an airmass of ~1.2 in excellent conditions. The field was imaged using the r, z, J and K filters. Photometric calibration was performed using nearby stars from the Pan-STARRS and 2MASS catalogues. Magnitudes are reported in the AB system and are not corrected for Galactic extinction. At the position of the optical counterpart (Aguilar-Ruiz et al., GCN 44719; Li et al., GCN 44720; Busmann et al.44728; Corcoran et al. GCN 44729 ), we detect a source with the following preliminary magnitude: z = 23.1 +/- 0.1 J = 23.0 +/- 0.1 Compared to earlier observations (Aguilar-Ruiz et al., GCN 44719), our measurements suggest a rapid fading of the afterglow, consistent with the observed X-ray behavior (Yang et al. GCN, 44725). We thank the staff at the VLT for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44730. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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