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[vsnet-grb-info 41129] GRB 251208D: LAST optical upper limit
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43049 SUBJECT: GRB 251208D: LAST optical upper limit DATE: 25/12/09 13:50:40 GMT FROM: Ruslan Konno at Weizmann Institute of Science <ruslankonno(a)gmail.com> R. Konno (WIS), S. Garrappa (WIS), E. A. Zimmerman (WIS), A. Horowicz (WIS), E. O. Ofek (WIS), S. Ben-Ami (WIS), D. Polishook (WIS), O. Yaron (WIS), S. Fainer (WIS), A. Krassilchtchikov (WIS), Y. M. Shani (WIS), E. Segre (WIS), A. Gal-Yam (WIS), and S. Spitzer (WIS) report on behalf of the LAST Collaboration. We report observations of GRB 251208D, detected by SVOM (Lin et al., GCN 43032). Observations were conducted with the Large Array Survey Telescope (LAST; Ofek et al. 2023, PASP 135, 5001; Ben-Ami et al. 2023, PASP 135, 5002). We observed the field of GRB 251208D using 4 divergent telescopes (each with a 7.4 deg^2 FoV) in clear band (similar to the Gaia Bp band) over 5 sequential epochs. Each epoch consists of 20x20s exposures. We began observations at 2025-12-08 17:22:15 UTC (T-T0 = 0.53h). We coadd a total of 100x20s exposure images and perform image subtraction using a reference image of the field. We do not detect any new optical source up to a limiting magnitude of 20.33 (AB) within the error region reported in Lin et al., GCN 43032. LAST is a survey telescope array of the Weizmann Astrophysical Observatory (https://www.weizmann.ac.il/wao/). View this GCN Circular online at https://gcn.nasa.gov/circulars/43049. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41128] GRB 251209A: Fermi GBM Final Real-time Localization
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43048 SUBJECT: GRB 251209A: Fermi GBM Final Real-time Localization DATE: 25/12/09 13:34:44 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 13:24:03 UT on 9 Dec 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251209A (trigger 786979448.987734 / 251209558). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 214.2, Dec = 43.1 (J2000 degrees, equivalent to J2000 14h 16m, 43d 06'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 52.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251209558/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43048. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41127] GRB 251208D: LCO analysis of the XRT sources
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43047 SUBJECT: GRB 251208D: LCO analysis of the XRT sources DATE: 25/12/09 12:07:14 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. B. Malesani (DAWN/NBI and Radboud), D. Turpin, A. Saccardi (CEA/Irfu), Z.-Y. Lin, F. Cangemi (APC), report on behalf of the SVOM mission team: Following the report of two X-ray sources detected by Swift/XRT (Evans et al., GCN 43043), we inspected again our images taken with LCO (Turpin et al., GCN 43037) of the field of the SVOM GRB 251208A (Lin et al., GCN 43032). * XRT source #1 matches the high proper-motion star TYC 5226-156-1 (distance ~500 pc). We measure a magnitude of r = 11.34 +- 0.02, consistent with the APASS archival value r = 11.34 +- 0.06. * XRT source #2 is consistent with SDSS J223038.66-003108.3, a known QSO at z = 1.32 with magnitude r = 20.34 (from SDSS) and r = 20.65 (from Pan-STARRS), possibly indicating some long-term variability. We measure r = 20.73 +- 0.12, indicating that the object is not in a particularly active state. Our observations suggest that neither sources are likely related to the high-energy emission observed by SVOM. This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43047. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41126] GRB 251208B: Fermi GBM Observation
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43046 SUBJECT: GRB 251208B: Fermi GBM Observation DATE: 25/12/09 11:51:58 GMT FROM: Andreas von Kienlin at MPE <azk(a)mpe.mpg.de> A. von Kienlin (MPE) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 10:17:17.29 UT on 08 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251208B (trigger 786881842/251208429). which was also detected by Fermi-LAT (E. Bissaldi et al. 2025, GCN 43034) and Swift/BAT-GUANO (GCN #43033). The Fermi GBM on-ground location was reported by the Fermi-GBM team in GCN 43028 and is consistent with the Fermi-LAT and Swift/BAT positions. The GBM light curve shows a structured emission episode with a duration (T90) of about 62.5 s (50-300 keV). The time-averaged spectrum from T0-4.1 to T0+61.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.67 +/- 0.08 and the cutoff energy, parameterized as Epeak, is 250 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (9.5 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+55 s in the 10-1000 keV band is 2 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/43046. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41125] GRB 251208B: GROWTH-India Telescope optical upper limits
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43045 SUBJECT: GRB 251208B: GROWTH-India Telescope optical upper limits DATE: 25/12/09 09:02:28 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> A. Kumar, T. Mohan, V.Swain, S. Patil, A.P. Saikia, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of Fermi GBM transient (Fermi GBM Team, GCN 43028), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-12-08T23:43:57 UT, i.e., about 13.4 hours after the Fermi GBM Trigger. Exposures were obtained in r' and i' filters. We did not detect any transient in our images within the Fermi-LAT on-ground localization region (Bissaldi et al., GCN 43034). Additionally, we checked the source 1 and 5 of Swift-XRT ToO observations (Evans at al., GCN 43035), and did not detect any optical counterpart at their respective position and uncertainty. The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (hrs) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | ------------- | ------------------- | ---------------- | | 61018.007928 | r' | 13.90 | 3 x 360 | 20.6 | | 61018.020746 | i' | 14.21 | 2 x 360 | 17.4 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/43045. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41124] GRB 251205A: J-band detection with WINTER
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43044 SUBJECT: GRB 251205A: J-band detection with WINTER DATE: 25/12/09 02:23:58 GMT FROM: Geoffrey Mo at Caltech / Carnegie Observatories <gmo(a)mit.edu> Geoffrey Mo (Caltech/Carnegie), Tomas Ahumada (NOIRLab), Benjamin Schneider (LAM), Viraj Karambelkar (Columbia), Robert Stein (UMD), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 251205A (Lanava et al., GCN 43005; Beardmore et al., GCN 43007; Dichiara et al., GCN 43017; Krimm et al., GCN 43018) in the near-infrared J band with the Palomar 1-m telescope, equipped with the 1.2-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations began at 2025-12-06T10:27:54 UTC in the J band (~10.8 hours after the GRB trigger), consisting of 15 x 120 s exposures.The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565). We detect a source at the optical counterpart location (Lipunov et al., GCN 43004; Lanava et al., GCN 43005; Lipunov et al., GCN 43006; de Ugarte Postigo et al., GCN 43008; Malesani et al., GCN 43009; O’Neill et al., GCN 43010; Mandarakas et al., GCN 43011; Pankov et al., GCN 43012; Bochenek et al., GCN 43015; Klinger et al., GCN 43016; Patil et al., GCN 43019; Pérez-Fournon et al., GCN 43020; Bochenek et al., GCN 43024; Busmann et al., GCN 43026; Hagio et al., GCN 43029; Bochenek et al., GCN 43038), with magnitude J = 17.9 ± 0.1 mag (AB). WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/43044. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41123] GRB 251208D: Swift-XRT observations
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43043 SUBJECT: GRB 251208D: Swift-XRT observations DATE: 25/12/09 02:01:30 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source sb25120806 (GCN 43032), collecting 2.4 ks of Photon Counting (PC) mode data between T0+5.2 ks and T0+11 ks after the trigger. We have detected 2 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 1 uncatalogued X-ray source * 1 known X-ray source Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J223038.6-003107): ================================== RA (J2000.0): 337.6610 = 22 30 38.64 Dec (J2000.0): -0.5186 = -00 31 07.0 Error: 5.8 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 10.7 arcmin from the SVOM/ECLAIRs position. Mean rate: (4.6 [+2.2, -1.7])e-3 ct s^-1 Mean flux: (4.6 [+2.2, -1.7])e-13 erg cm^-2 s^-1 Peak rate: (4.6 [+2.2, -1.7])e-3 ct s^-1 Peak flux: (4.6 [+2.2, -1.7])e-13 erg cm^-2 s^-1 ECF: 1.02e-10 erg cm^-2 ct^-1 assuming NH=3.34e+21 cm^-2, gamma=0.47 determined from a spectral fit. RASS UL: 1.6e-01 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `SDSS J223038.66-003108.3' is 1.2" away. Known X-ray sources ------------------- Source 1 (SWIFT J222951.0-001338): ================================== RA (J2000.0): 337.4626 = 22 29 51.02 Dec (J2000.0): -0.2273 = -00 13 38.3 Error: 5.2 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 10.8 arcmin from the SVOM/ECLAIRs position. Mean rate: (5.6 [+2.4, -1.9])e-3 ct s^-1 Mean flux: (2.41 [+1.05, -0.81])e-13 erg cm^-2 s^-1 Peak rate: (5.6 [+2.4, -1.9])e-3 ct s^-1 Peak flux: (2.41 [+1.05, -0.81])e-13 erg cm^-2 s^-1 This matches a catalogued X-ray source 4XMM J222950.9-001339 in the XMM-NEWTON/XMMSSC catalogue. Details: Separation: 2.0" from the XRT source Cat Rate: 5.9e-02 +/- 8.2e-03 ct s^-1 Cat Flux: 6.0e-13 +/- 8.3e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. A SIMBAD object `TYC 5226-156-1' is 1" away. There is 1 2MASS object within the source's 3-sigma error radius. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM/SVOM_FIELD00056. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/43043. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41122] GRB 251208A: SVOM/GRM observation of a short burst
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43042 SUBJECT: GRB 251208A: SVOM/GRM observation of a short burst DATE: 25/12/09 01:54:54 GMT FROM: Yue Wang <m18509381757(a)163.com> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Wen-Jun Tan, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 251208A (SVOM trigger reference: sb25120804) at 2025-12-08T09:25:58.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43027). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 2.2 +0.9/-0.5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251208A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 32.8, Dec = -66.7, position uncertainty = 3.9, GCN #43027), is located at about 61 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-1 to T0+2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.20 +0.19/-0.18 and the cutoff energy, parameterized as Epeak, is 135 +51/-27 keV. The event fluence (10-1000 keV) in this time interval is (1.29 +0.19/-0.14)E-06 erg/cm^2. The 1s peak spectrum, measured from T0-0.6 to T0+0.4 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -0.98 +0.17/-0.18 and the cutoff energy, parameterized as Epeak, is 139 +33/-21 keV. The flux (10-1000 keV) in this time interval is (7.79 +0.91/-0.72)E-07 erg/cm^2/s. The localization of GRB 251208A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251208A_amati.png The localization of GRB 251201A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251208A_yonetoku.png In the absence of a measured redshift, the duration, soft spectrum, and position in the Amati diagram do not allow us to determine whether this burst is type I or type II. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43042. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41121] GRB 251208C: SVOM/GRM observation of a short burst
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43041 SUBJECT: GRB 251208C: SVOM/GRM observation of a short burst DATE: 25/12/09 01:00:49 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Yue Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 251208C (SVOM trigger reference: sb25120805) at 2025-12-08T12:52:32.600 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43030). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 0.36 +0.06/-0.08 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251208C.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 312.8 deg, Dec = -30.7 deg, Error=4.8 deg, GCN #43030), is located at about 84 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-0.12 to T0+0.04 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.54 +0.22/-0.19 and the cutoff energy, parameterized as Epeak, is 617 +241/-151 keV. The event fluence (10-1000 keV) in this time interval is (1.18 +0.09/-0.12)E-06 erg/cm^2. The localization of GRB 251208C in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251208C_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/43041. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41120] GRB 251129A: e-MERLIN C-band observations
by GCN Circulars 09 Dec '25

09 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43040 SUBJECT: GRB 251129A: e-MERLIN C-band observations DATE: 25/12/09 00:50:36 GMT FROM: Tao An at SHAO, CAS <antao(a)shao.ac.cn> Tao An (SHAO), Ailing Wang (IHEP), Emmanuel Bempong-Manful (UoM), Zigao Dai (USTC), and collaborators report on e-MERLIN observations of GRB 251129A. We observed GRB 251129A (GCN 42877, 42879, 42880, 42882, 42884, 42887, 42888, 42891, 42897, 42900, 42902, 42959, 42972, 42985) with the e-MERLIN array in the C band between 2025 December 3, 17:40 UT and December 5, 04:19 UT (project RR20009). Four antennas, Pickmere (Pi), Darnhall (Da), Knockin (Kn), and Cambridge (Cm), participated in the observation. Observing setup: - Frequency coverage: 4.82–5.33 GHz (C band), total bandwidth 512 MHz - Antennas: Pi, Da, Kn, Cm - Polarizations: Right and left circular - Spectral setup: 4 × 128 MHz spectral windows, 128 × 1 MHz channels per window (post-averaging) - Observation span: 2025-12-03 17:40 UT to 2025-12-05 04:19 UT The data were processed using the standard e-MERLIN pipeline followed by calibration and imaging in CASA. No significant radio emission was detected at the position of GRB 251129A. We place a 3σ upper limit of 0.066 mJy beam⁻¹ on the flux density. We encourage coordinated and continued radio follow-up to further constrain the flux density and probe potential variability at C band and complementary frequencies. We thank the e-MERLIN TAG and operations teams for their support. View this GCN Circular online at https://gcn.nasa.gov/circulars/43040. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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