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[vsnet-grb-info 41313] GRB 251222A: Continued 1.3m DFOT optical observation
by GCN Circulars 24 Dec '25

24 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43224 SUBJECT: GRB 251222A: Continued 1.3m DFOT optical observation DATE: 25/12/24 07:40:06 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kuntal Misra, Pankaj Pawar, Dhruv Jain, and Debalina Kar (ARIES) report: We observed the field of GRB 251222A detected by Fermi/GBM (Fermi GBM team, GCN 43186) and SVOM (Yang et al. 2025, GCN 43188) 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 2025-12-23 at 18:56:19 UT, i.e., ~ 25.84 hours after the Fermi/GBM trigger. We have taken multiple frames with an exposure time of 200s in the I filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image within the error box of SVOM (Palmerio et al. 2025, GCN 43189). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hour) Filter Exp time (s) Magnitude =============================================================== 2025-12-23 18:56:19 ~25.84 I 200s*8 19.55 +/-0.02 The optical detection of the burst is consistent with Palmerio et al. 2025, (GCN 43189); An et al. 2025 (GCN 43194); Calapai et al. 2025 (GCN 43195); Durbak et al. 2025 (GCN 43197); Li et al. 2025 (GCN 43203); Saccardi et al. 2025 (GCN 43204); Gupta et al. 2025 (GCN 43207); Saccardi et al. 2025 (GCN 43208); Kumar et al. 2025 (GCN 43209); Pérez-Fournon et al. 2025 (GCN 43212). 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-B1.0 catalogue. View this GCN Circular online at https://gcn.nasa.gov/circulars/43224. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41312] EP251220a: 3.6m DOT optical afterglow detection
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43223 SUBJECT: EP251220a: 3.6m DOT optical afterglow detection DATE: 25/12/23 19:45:40 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kuntal Misra, Divyanshu Janghel, Debalina Kar, Dhruv Jain, and Pankaj Pawar (ARIES) report: We observed the field of EP251220a detected by EP/WXT (Liu et al. 2025; GCN 43162) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-12-21 at 17:13:18 UT, i.e., ~1.36 days after the EP/WXT trigger. We have taken multiple frames with an exposure time of 300s in the r filter. We stacked the images after the alignment. We detect a optical counterpart in our stacked image within the error box of COLIBRÍ telescope (Sánchez Álvarez et al. 2025; GCN 43167). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================== 2025-12-21 17:13:18 ~1.36 r 300s*8 21.64 +/-0.02 Our detection is consistent with Lipunov et al. 2025 (GCN 43163); Sánchez Álvarez et al. 2025 (GCN 43167); Kumar et al. 2025 (GCN 43169); Rakotondrainibe et al. 2025 (GCN 43170); Busmann et al. 2025 (GCN 43181); van Hoof et al. 2025 (GCN 43182); An et al. 2025 (GCN 43184); Passaleva et al. 2025 (GCN 43185); Volnova et al. 2025 (GCN 43221). 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 PanSTARRS DR1 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/43223. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41311] EP251220a: 3.6m DOT optical afterglow detection
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43223 SUBJECT: EP251220a: 3.6m DOT optical afterglow detection DATE: 25/12/23 19:45:40 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Kuntal Misra, Divyanshu Janghel, Debalina Kar, Dhruv Jain, and Pankaj Pawar (ARIES) report: We observed the field of EP251220a detected by EP/WXT (Liu et al. 2025; GCN 43162) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2025-12-21 at 17:13:18 UT, i.e., ~1.36 days after the EP/WXT trigger. We have taken multiple frames with an exposure time of 300s in the r filter. We stacked the images after the alignment. We detect a optical counterpart in our stacked image within the error box of COLIBRÍ telescope (Sánchez Álvarez et al. 2025; GCN 43167). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================== 2025-12-21 17:13:18 ~1.36 r 300s*8 21.64 +/-0.02 Our detection is consistent with Lipunov et al. 2025 (GCN 43163); Sánchez Álvarez et al. 2025 (GCN 43167); Kumar et al. 2025 (GCN 43169); Rakotondrainibe et al. 2025 (GCN 43170); Busmann et al. 2025 (GCN 43181); van Hoof et al. 2025 (GCN 43182); An et al. 2025 (GCN 43184); Passaleva et al. 2025 (GCN 43185); Volnova et al. 2025 (GCN 43221). 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 PanSTARRS DR1 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/43223. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41310] GRB 251222A: Fermi GBM Observation
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43222 SUBJECT: GRB 251222A: Fermi GBM Observation DATE: 25/12/23 18:39:59 GMT FROM: eliza.neights(a)gmail.com Eliza Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 17:05:51.27 UT on 22 December 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251222A (trigger 788115956/251222712). which was also detected by SVOM ECLAIRs, GRM, and MXT (H. Yang et al. 2025, GCN 43188), SVOM VT (J. T. Palmerio et al. 2025, GCN 43189), NOT (J. An et al. 2025, GCN 43194), Calapai Observatory (G. Calapai et al. 2025, GCN 43195), PRIME (J. Durbak et al. 2025, GCN 43197), EP WXT (C.-L. Guo et al. 2025, GCN 43201), DFOT (A. Gupta et al. 2025, GCN 43207), LCO (A. Saccardi et al. 2025, GCN 43208; I. Pérez-Fournon et al. 2025, GCN 43212), GOTO (A. Kumar et al. 2025, GCN 43209), Swift XRT (A.P. Beardmore et al. 2025, GCN 43213), and Konus Wind (D. Frederiks et al. 2025, GCN 43214). The spectroscopic redshift of GRB 251222A is found to be 3.171 by VLT/X-shooter (A. Saccardi et al. 2025, GCN 43204). The Fermi GBM on-ground location is consistent with the position reported by other instruments. The angle from the Fermi LAT boresight is 83 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 83 s (50-300 keV). The time-averaged spectrum from T0-2.2 to T0+91.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.26 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 118 +/- 1 keV. The event fluence (10-1000 keV) in this time interval is (1.09 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+54 s in the 10-1000 keV band is 9.5 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 64.9 +/- 0.8 keV, alpha = -0.84 +/- 0.01 and beta = -2.0 +/- 0.02. 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/43222. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41309] EP251220a: CrAO ZTSh optical observations
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43221 SUBJECT: EP251220a: CrAO ZTSh optical observations DATE: 25/12/23 18:19:15 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. A. Volnova (IKI), V. V. Rumyantsev (CrAO), A. S. Pozanenko (IKI), N. S. Pankov (HSE, IKI) report on behalf of IKI-GRB-FuN: We observed the field of the fast X-ray transient EP251220a detected by EP/WXT (Liu et al., GCN 43162) with the ZTSh 2.6m telescope of CrAO taking several 120-second frames in R-band. The observations started on Dec. 22 at UT 20:32:36, i.e., ~ 2.5 days after the EP/WXT trigger. In the stacked image we detect the optical counterpart reported previously (Sánchez Álvarez et al., GCN 43167; Kumar et al., GCN 43169; Rakotondrainibe et al., GCN 43170; Busmann et al., GCN 43181; van Hoof et al., GCN 43182; An et al., GCN 43184; Passaleva et al., GCN 43185). 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) 2025-12-22 20:32:36 2.51642 17*120 R 22.55 0.20 22.9 CrAO/ZTSh 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/43221. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41308] EP251221a: PRIME upper limit
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43220 SUBJECT: EP251221a: PRIME upper limit DATE: 25/12/23 17:54:25 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> N. Passaleva (U Rome), O. Guiffreda (UMD), M. El Kabir (U Rome), J. Durbak (UMD), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC) We observed the field of the fast x-ray transient EP251221a detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Dai et al. GCN 43178) in J and H filters with PRIME. Observations started ~24h after the trigger. Using Two Micron All Sky Survey (2MASS) nearby stars for preliminary calibration we do not detect any uncatalogued source down to J>21 AB (3-sigma) not corrected for galactic extinction in the WXT error region. PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024). We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43220. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41307] EP251222a: Global MASTER-Net observations report
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43219 SUBJECT: EP251222a: Global MASTER-Net observations report DATE: 25/12/23 15:36:29 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP251222a ( EP Team et al., GCN 43200) errorbox 25213 sec after notice time and 69548 sec after trigger time at 2025-12-23 10:37:14 UT, with upper limit up to 16.4 mag. Observations started at twilight. The observations began at zenith distance = 78 deg. The sun altitude is -13.8 deg. MASTER-Kislovodsk robotic telescope located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251222a errorbox 39747 sec after notice time and 84082 sec after trigger time at 2025-12-23 14:39:28 UT, with upper limit up to 16.9 mag. Observations started at twilight. The observations began at zenith distance = 75 deg. The sun altitude is -10.5 deg. The galactic latitude b = -35 deg., longitude l = 194 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3081644 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 66002 | 2025-12-23 09:36:37 | MASTER- | (04h 15m 01.67s , -00d 43m 08.5s) | C | 180 | 16.3 | 69578 | 2025-12-23 10:37:14 | MASTER-Tunka | (04h 09m 44.57s , -01d 55m 17.1s) | C | 60 | 16.4 | 69578 | 2025-12-23 10:37:14 | MASTER-Tunka | (04h 09m 58.83s , -02d 01m 41.0s) | C | 60 | 16.1 | 69649 | 2025-12-23 10:38:24 | MASTER-Tunka | (04h 09m 58.86s , -02d 01m 41.4s) | C | 60 | 15.7 | 69649 | 2025-12-23 10:38:25 | MASTER-Tunka | (04h 09m 44.41s , -01d 55m 16.5s) | C | 60 | 16.1 | 84112 | 2025-12-23 14:39:28 | MASTER-Kislovodsk | (04h 07m 57.86s , -01d 42m 13.8s) | C | 60 | 16.9 | 84112 | 2025-12-23 14:39:28 | MASTER-Kislovodsk | (04h 07m 58.58s , -01d 19m 40.7s) | C | 60 | 15.8 | 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/43219. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41306] GRB 251222A / EP251222b: GECAM-B observation
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43218 SUBJECT: GRB 251222A / EP251222b: GECAM-B observation DATE: 25/12/23 15:23:20 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Yue Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst GRB 251222A at 2025-12-22T17:05:52.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43186), SVOM (H. Yang et al., GCN #43188, Chen-Wei Wang et al., GCN #43202), Einstein Probe (C.-L. Guo et al., GCN #43201) and Konus-Wind (D. Frederiks et al., GCN #43214). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses main emission with a duration (T90) of 55.8 +1.4/-9.6 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251222A.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/43218. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41305] GRB 251222A / EP251222b: GECAM-B observation
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43218 SUBJECT: GRB 251222A / EP251222b: GECAM-B observation DATE: 25/12/23 15:23:20 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Yue Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by a long burst GRB 251222A at 2025-12-22T17:05:52.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43186), SVOM (H. Yang et al., GCN #43188, Chen-Wei Wang et al., GCN #43202), Einstein Probe (C.-L. Guo et al., GCN #43201) and Konus-Wind (D. Frederiks et al., GCN #43214). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses main emission with a duration (T90) of 55.8 +1.4/-9.6 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb251222A.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/43218. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41304] EP251221a: Liverpool Telescope upper limits
by GCN Circulars 23 Dec '25

23 Dec '25

TITLE: GCN CIRCULAR NUMBER: 43217 SUBJECT: EP251221a: Liverpool Telescope upper limits DATE: 25/12/23 15:21:03 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of the fast X-ray transient EP251221a (Dai et al., GCN 43178) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 3x120s exposures in SDSS r and i filters starting at 2025-12-22 23:12:54 UT, approximately 25.6 hours after the trigger. We perform image subtraction of the stacked images against Pan-STARRS using PSF matching with the help of PSFEx. We do not detect any new objects within the EP/WXT error region of the transient (Dai et al., GCN 43178). We note the i-band Pan-STARRS reference image is affected by a small number of artefacts, covering in total less than 1% of the error region. The 3-sigma limiting magnitudes on the stacked images are r > 22.6 and i > 22.5. View this GCN Circular online at https://gcn.nasa.gov/circulars/43217. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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