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[vsnet-grb-info 40856] Fermi trigger No 785388351: Global MASTER-Net observations report
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42788 SUBJECT: Fermi trigger No 785388351: Global MASTER-Net observations report DATE: 25/11/21 14:45:55 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 GRB251121.14 (trigger No 785388351,21h 39m 12.00s , +42d 06m 36.0s, R=11.36) errorbox 39901 sec after notice time and 39938 sec after trigger time at 2025-11-21 14:31:24 UT, with upper limit up to 16.5 mag. Observations started at twilight. The observations began at zenith distance = 2 deg. The sun altitude is -9.1 deg. The galactic latitude b = -8 deg., longitude l = 90 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3048278 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 39968 | 2025-11-21 14:31:24 | MASTER-Kislovodsk | (21h 28m 33.86s , +41d 27m 00.7s) | C | 60 | 15.6 | 39968 | 2025-11-21 14:31:24 | MASTER-Kislovodsk | (21h 34m 49.78s , +41d 04m 07.6s) | C | 60 | 14.0 | 40048 | 2025-11-21 14:32:44 | MASTER-Kislovodsk | (21h 47m 06.83s , +43d 20m 11.1s) | C | 60 | 16.0 | 40048 | 2025-11-21 14:32:44 | MASTER-Kislovodsk | (21h 53m 30.83s , +42d 57m 01.9s) | C | 60 | 13.4 | 40227 | 2025-11-21 14:35:43 | MASTER-Kislovodsk | (21h 49m 03.50s , +41d 25m 22.5s) | C | 60 | 16.1 | 40227 | 2025-11-21 14:35:44 | MASTER-Kislovodsk | (21h 55m 10.89s , +41d 02m 46.0s) | C | 60 | 14.1 | 40308 | 2025-11-21 14:37:04 | MASTER-Kislovodsk | (21h 32m 22.61s , +39d 32m 55.4s) | C | 60 | 16.1 | 40308 | 2025-11-21 14:37:04 | MASTER-Kislovodsk | (21h 38m 18.31s , +39d 09m 16.6s) | C | 60 | 13.7 | 40388 | 2025-11-21 14:38:24 | MASTER-Kislovodsk | (21h 52m 03.41s , +39d 31m 14.7s) | C | 60 | 16.5 | 40388 | 2025-11-21 14:38:24 | MASTER-Kislovodsk | (21h 58m 00.63s , +39d 07m 52.4s) | C | 60 | 14.0 | 40474 | 2025-11-21 14:39:50 | MASTER-Kislovodsk | (21h 30m 34.79s , +41d 17m 12.7s) | C | 60 | 16.2 | 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/42788. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40855] EP251118A: 1.3m DFOT optical afterglow detection
by GCN Circulars 21 Nov '25

21 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42787 SUBJECT: EP251118A: 1.3m DFOT optical afterglow detection DATE: 25/11/21 12:03:39 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Debolina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of EP251118A detected by the Einstein Probe (Jiang et al. 2025, GCN 42749) 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 2025-11-20 at 20:16:13 UT, i.e., ~ 2.14 days after the Einstein Probe 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 NOT (Malesani et al. 2025, GCN 42751). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ====================================================================== 2025-11-20 20:16:13 ~2.14 R 250s*18 21.15 +/- 0.25 Our detection is consistent with Malesani et al. 2025 (GCN 42751); Belkin et al. 2025 (GCN 42758);Yadav et al. 2025 (GCN 42760); Busmann et al. 2025 (GCN 42763); Francile et al. 2025 (GCN 42767); Rodríguez et al. 2025 (GCN 42773); Li et al. 2025 (GCN 42776); Lee et al. 2025 (GCN 42780); Moskvitin et al. 2025 (GCN 42785). 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 Gaia catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/42787. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40854] GRB 251118A: Swift/UVOT Detection
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42786 SUBJECT: GRB 251118A: Swift/UVOT Detection DATE: 25/11/20 22:23:37 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 251118A 31.3 ks after the Fermi trigger (GCN Circ. 42743). A fading source consistent with the XRT position (Osbourne et al., GCN Circ. 42782) is detected in the UVOT exposures. The preliminary UVOT position is: RA (J2000) = 10:14:01.01 = 160.00422 (deg.) Dec (J2000) = -34:31:21.1 = -34.52254 (deg.) with an estimated uncertainty of 0.42 arc sec. (radius, 90% confidence). Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white 31521 52651 885 18.79+/-0.05 white 108251 159027 1113 20.11+/-0.10 v 31678 42929 845 18.60+/-0.19 v 108564 147691 662 >19.73 u 31363 52627 2489 18.41+/-0.05 u 107942 158555 1113 19.61+/-0.15 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.057 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/42786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40853] EP251118a / GRB 251118C: SAO RAS optical observations
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42785 SUBJECT: EP251118a / GRB 251118C: SAO RAS optical observations DATE: 25/11/20 21:15:01 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin and O. Spiridonova (SAO RAS), report on behalf of GRB follow-up team We observed the field of the EP251118a discovered by Einstein Probe (Jiang et al., GCN 42749; Shi et al., GCN 42754, also detected with the other space observatories, Frederiks et al., GCN 42765; Wang et al., GCN 42766; DeLaunay et al., GCN 42770; Woolf et al., GCN 42771) with the 1-m SAO RAS telescope Zeiss-1000 equipped with the CCD-photometer. We obtained 9 x 300 sec. images Rc band on 2025.11.19T23:26:31--2025.11.20T03:08:31 (t_mid - T0 = 1.35766 d). The OT (Malesani et al., GCN 42751; An et al., GCN 42756; Belkin et al., GCN 42758; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773; Lee et al., GCN 42780; also detected in NIR; Yadav et al., GCN 42760) is clearly visible in our stacked image with the brightness of R = 21.24 +/- 0.07. Preliminary photometry is based on the nearby objects from SDSS (magnitudes converted with Lupton 2005 equations) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42785. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40852] GRB 251118A: Glowbug gamma-ray detection
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42784 SUBJECT: GRB 251118A: Glowbug gamma-ray detection DATE: 25/11/20 20:44:33 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 251118A, which was also detected by Fermi/GBM (GCN 42743, 42745, 42783), Fermi/LAT (GCN 42752), NuSTAR (GCN 42774), and GECAM-B (GCN 42779). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2025-11-18 20:31:43.57 with a duration of 47.1 s and a total significance of over 360 sigma. The light curve comprises two peaks at ~T0+1.5s and +37s, matching the two brightest peaks in the Fermi/GBM and GECAM-B lightcurves. The initial faint emission at the GBM trigger time (20:31:30) may be present in the Glowbug light curve at low significance. The GRB was detected despite the elevated background due to Glowbug being in and exiting the Southern polar region at the time of the burst. Note that data throughout the burst interval 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/42784. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40851] GRB 251118A: Fermi GBM Observation
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42783 SUBJECT: GRB 251118A: Fermi GBM Observation DATE: 25/11/20 19:37:15 GMT FROM: Eva MP <eva.palafox(a)gmail.com> Eva Palafox (INAOE) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 20:31:30.09 UT on 18 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251118A (trigger 785190695/251118855), which was also detected by Fermi-LAT (R. Gupta et al. 2025, GCN 42752), Swift/XRT (J.P. Osborne et al. 2025, GCN 42782), GECAM-B (Yang-Zhao Ren et al., 2025, GCN 42779) and NuSTAR (G. Waratkar et al. 2025, GCN 42774). The Fermi GBM final real-time localization (GCN 42743) is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 69 degrees. The GBM light curve consists of a faint emission episode, followed by very bright emission episodes, with a total duration (T90) of about 46.6 s (50-300 keV). The time-averaged spectrum from T0-2.8 to T0+87.3 s is best fit by a Comptonized function with Epeak = 149.3 +/- 2.0 keV, and alpha = -1.40 +/- 0.01. A Band function fits equally well with Epeak = 134.0 +/- 2.7, alpha = -1.36 +/- 0.01, and beta = -2.56 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (1.03 +/- 0.01)E-04 erg/cm^2. The 1-sec peak photon flux measured starting from T0+52 s in the 10-1000 keV band is 96 +/- 0.7 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/42783. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40850] GRB 251118A: Swift-XRT afterglow detection
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42782 SUBJECT: GRB 251118A: Swift-XRT afterglow detection DATE: 25/11/20 13:53:24 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), D.N. Burrows (PSU), S. Lanava (PSU), S. Dichiara (PSU) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 251118A. We searched for X-ray sources in 3.0 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 5.4 ks, obtained between T0+31.3 ks and T0+108.8 ks. Two uncatalogued X-ray sources are detected, of which one ("Source 1") is above the RASS 3-sigma upper limit at this position, and is therefore likely the GRB afterglow. Using 3939 s of PC mode data and 7 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 160.00418, -34.52259 which is equivalent to: RA (J2000): 10h 40m 01.00s Dec(J2000): -34d 31' 21.3" with an uncertainty of 2.0 arcsec (radius, 90% confidence). This position is 5.0 arcmin from the Fermi/LAT position. The light curve can be modelled with a power-law decay with a decay index of alpha=1.08 (+0.18, -0.16). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.73 (+0.16, -0.15). The best-fitting absorption column is 2.2 (+0.7, -0.6) x 10^21 cm^-2, in excess of the Galactic value of 8.3 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 4.1 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.2 (+0.7, -0.6) x 10^21 cm^-2 Galactic foreground: 8.3 x 10^20 cm^-2 Excess significance: 3.9 sigma Photon index: 1.73 (+0.16, -0.15) The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/xrt_products/00021890. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021890. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42782. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40849] GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42781 SUBJECT: GRB 251103A: SVOM/ECLAIRs and SVOM/GRM joint refined analysis DATE: 25/11/20 09:43:04 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> N. Dagoneau, B. Hubert, S. Schanne (CEA), J.-L. Atteia (IRAP), C.-W. Wang (IHEP) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs and SVOM/GRM observations of GRB 251103A (SVOM burst-id sb25110301, GCN 42534, GCN 42552), which was also detected by NOT (GCN 42535), Fermi/GBM (GCN 42536), LCO (GCN 42538), BOOTES-2/TELMA (GCN 42539), GOTO (GCN 42543), SVOM/COLIBRI (GCN 42549), Swift-XRT (GCN 42551), Fermi/GBM (GCN 42553), Swift/UVOT (GCN 42554), Kilonova-Catcher (GCN 42559), WINTER (GCN 42562), Global MASTER-Net (GCN 42565), Swift/BAT-GUANO (GCN 42568), KAIT (GCN 42571), Insight-HXMT (GCN 42572), Xinglong 2.16m (GCN 42573), OHP/T193 (GCN 42574), WFST (GCN 42577), ZTF (GCN 42579) The burst that triggered ECLAIRs shows a light-curve consisting of two peaks: a soft precursor occurring from T0-4s to T0+2s mainly in the 4-30 keV energy band (T0=2025-11-03T04:46:21 UTC), and a main peak occurring from T0+2s to T0+16s in the 4-120 keV energy band. The event has a total duration of 20s (T90 is not a good measure in this case, because it covers incompletely both peaks). ECLAIRs triggered onboard on both peaks, GRM only detected the main peak. Using an analysis of the ECLAIRs data alone, the time-averaged spectrum of the precursor (from T0-4 s to T0+2 s) in the 8-20 keV energy band is best fitted by a power-law model with a photon index of -3.01 -0.2/+0.3, indicating a very soft spectrum (while a simple black-body model does not provide a good fit). With this model, the mean energy fluence in 4-120 keV is (4.97 +/- 2.73)E-08 erg/cm^2. The time-averaged spectrum of the main peak (from T0+2 s to T0+16 s) in the 8-120 keV energy band is best fitted by a cutoff power-law model with a photon index of -1.18 -0.02/+0.12 and a cutoff energy parametrized as Epeak of 122 +/- 26 keV. With this model, the mean energy fluence in 4-120 keV is (4.14 +/- 0.19)E-06 erg/cm^2. Using a joint analysis of ECLAIRs and GRM data, the time-averaged spectrum of the main peak (T0+2 s to T0+16 s) in the 8-1000 keV energy band is best fitted by a Band model with a low-energy photon index of -1.12 +/-0.04, a high-energy photon index of -2.04 -0.11/+0.08 and a cutoff energy parametrized as Epeak of 116 +/- 23 keV. With this model, the mean energy fluence in 10-1000 keV is (8.33 +/- 0.58)E-06 erg/cm^2. With a redshift of z = 0.76 (GCN 42540), the isotropic equivalent energy of this burst Eiso (from 1 keV to 10 MeV in its rest frame) is 2.01 +/- 0.14 10^52 erg, which makes this GRB consistent with type II GRBs in the 'Amati' relation diagram (Amati et al. 2002). All the quoted errors are at the 68% confidence level. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM point of contact for this burst is: Nicolas Dagoneau (nicolas.dagoneau AT cea.fr) View this GCN Circular online at https://gcn.nasa.gov/circulars/42781. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40848] EP251118a: Optical detection with Kinder observations
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42780 SUBJECT: EP251118a: Optical detection with Kinder observations DATE: 25/11/20 09:35:57 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> Y.-H. Lee, A. Aryan, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), T.-W. Chen (NCU), J. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP251118a (Jiang et al., GCN 42749) using the 1m LOT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2025, ApJ, 983, 86). The first LOT epoch of observations started at 16:21 UTC on the 19th of November 2025 (MJD 60998.681), 23.64 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. We utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'hotpants' (Becker A., 2015, ascl.soft. ascl:1504.004) algorithm. In the difference image, we clearly detected the optical counterpart candidate proposed by Malesani et al. (GCN 42751) at a spectroscopic redshift of z = 1.216 (An et al., GCN 42756), and confirmed by Belkin et al. (GCN 42758); Yadav et al. (GCN 42760); Busmann et al. (GCN 42763); Francile et al. (GCN 42767); and Urquijo-Rodríguez et al. (GCN 42773). Moreover, we further utilized AutoPhOT to perform the PSF photometry. The details of the observations and the measured magnitude(in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 60998.681 | 23.64 | 300 * 6 | 21.136 +/- 0.049 | 1".47 | 1.67 The presented magnitude is calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry J. L. et al. 2018, ApJ, 867, 105) and is not corrected for the expected Galactic foreground extinction of A_r = 0.034 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 can be found 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/42780. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40847] GRB 251118A: GECAM-B detection
by GCN Circulars 20 Nov '25

20 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42779 SUBJECT: GRB 251118A: GECAM-B detection DATE: 25/11/20 08:32:34 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst, GRB 251118A, at 2025-11-18T20:31:30.089 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #42743), Fermi/LAT (Gupta et. al., GCN #42752), and NuSTAR (Waratkar et. al., GCN #42774). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 46.2 +0.2/-0.3 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251118A.png The time-averaged spectrum from T0-1.9 s to T0+71.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.54 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 99.8 +4.4/-4.5 keV. The event fluence (10-1000 keV) in this time interval is (1.01 +0.04/-0.04)E-04 erg/cm^2. The 'Amati' relation diagram of GRB 251118A is shown at: https://www.bursthub.cn//admin/static/gecambgrb251118A_amati.png Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/42779. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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