October 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 40474] GRB 251022A: COLIBRÍ optical observations
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42397 SUBJECT: GRB 251022A: COLIBRÍ optical observations DATE: 25/10/23 14:12:44 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Nikos Mandarakas (LAM), Ramandeep Gill (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the Fermi GRB 251022A (Di Lalla et al., GCN Circ. 42384) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-23 06:12:44 to 07:32:34 UTC (from 7.64 to 8.97 hours after the trigger) and obtained 16 and 3 minutes of exposure in the r and z filters respectively. The data were reduced and coadded with the 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. We detected the optical counterpart reported by O’Neill et al. (GCN Circ. 42386), Becerra et al. (GCN Circ. 42394), and Lipunov et al. (GCN Circ. 42395) at preliminary magnitudes of: r = 18.97 +/- 0.01 z = 18.54 +/- 0.04 Further observations are planned. 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/42397. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40473] GRB 251013C: ISON-Castelgrande observatory optical observations
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42396 SUBJECT: GRB 251013C: ISON-Castelgrande observatory optical observations DATE: 25/10/23 12:56:23 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), S. Schmalz (KIAM), A. Schmalz (KIAM), A. Pozanenko (IKI), N. Pankov (IKI, HSE), F. Graziani (GAUSS Srl) report on behalf of IKI GRB-FuN: We observed field of the GRB 251013C (Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) with ORI-22 telescope of ISON-Castelgrande observatory. Observation started on 2025-10-13 (UT) 21:40:38, i.e. ~2 hours after the GRB trigger. The series consists of 165 images with an exposure of 60 s in a Clear filter. The optical afterglow (Palmerio et al., GCN 42223; Perez-Garcia et al., GCN 42225; Konno et al., GCN 42226; Martin-Carrillo et al., GCN 42227; Masi, GCN 42228; Palmerio et al., GCN 42229; Moskvitin et al., GCN 42230; Gompertz et al., GCN 42231; Lipunov et al., GCN 42235; Garnavich, GCN 42240; Watson et al., GCN 42241; López-Cámara et al., GCN 42242; Brosio et al., GCN 42251; Reguitti, GCN 42253; Quintana-Ansaldo et al., GCN 42254; Maksut et al., GCN 42256; Ghosh et al., GCN 42261; Quadri et al., GCN 42262; Adami et al., GCNs 42266, 42276, 42338; Peretto et al., GCN 42267; Ruocco et al., GCN 42269; Calapai, GCN 42275; Globus et al., GCN 42279; Evans, GCN 42281; Abidkhanov et al., GCN 42283; Siegel, GCN 42298; Leonini et al, GCN 42301; Méndez et al., GCN 42318; He et al., GCN 42319; Pavoni et al., GCN 42333; Bochenek and Perley, GCN 42334) is clearly detected, and the preliminary photometry of the stacked frames is the following: Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2025-10-13 21:40:38 0.17290 15*60 Clear 16.75 0.10 18.0 2025-10-13 21:56:47 0.18487 15*60 Clear 16.86 0.08 18.0 2025-10-13 22:15:08 0.19875 20*60 Clear 17.00 0.10 18.1 2025-10-13 22:37:50 0.21452 20*60 Clear 17.19 0.11 18.1 2025-10-13 22:59:27 0.23325 30*60 Clear 17.47 0.12 18.3 2025-10-13 23:31:46 0.25573 30*60 Clear 17.35 0.13 18.1 2025-10-14 00:04:13 0.28013 35*60 Clear 17.54 0.19 17.9 The photometry is based on several nearby SDSS stars (R-magnitudes Lupton's transformation) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42396. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40472] GRB 251022A: MASTER OT detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42395 SUBJECT: GRB 251022A: MASTER OT detection DATE: 25/10/23 12:43:30 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V. Lipunov, I.Panchenko, A.Kuznetsov, O.Gress, G.Antipov, P.Balanutsa, E.Gorbovskoy, K.Zhirkov, N.Tiurina, A.Sankovich, Ya.Kechin, A.Chasovnikov, V.Topolev, D.Vlasenko, V.Senik, D.Vlasenko, V.Shumkov, K.Vetrov, Yu. Tselik, M.Shilova(Lomonosov MSU, SAI, Moscow), R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni.,Argentina); D.Buckley (SAAO, South Africa), N.Budnev (ISU, Irkutsk), A.Sosnovskij (CrAO RAS), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella,L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) MASTER Global Robotic Net [1-4] started Fermi GRB 251022A (GCNC 42380, Ttrigger=2025-10-22 22:34:15.26 ,GBM_notice=2025-10-22 22:43:43, LAT_notice=2025-10-23 03:04:17UT, LAT_center=04 21 31.18 -19 18 35.6 +-0.32deg (Di Lalla et al. GCN 42384) at MASTER-SAAO and MASTER-OAFA (Lipunov et al. GCNC 42381) 13s after LAT_notice_time (16215s after trigger time) There is MASTER OT J042159.34-185510.4 since 2025-10-23 03:04:54UT with unfiltered m_OT=18.0. This OT can be on MASTER very wide field images at earlier images in MASTER-Tunka, that started GBM error-filed observations in alert mode, the reduction will be continued. This OT was discovered by GOTO (O'Neill et al. GCNC 42386) and also observed by DDOTI (Becerra et al. GCNC 42394) We analyzed SWIFT XRT candidates (Evans et al. GCNC42382, https://www.swift.ac.uk/xrt_products/TILED_GRB00139/ ) The first one ( 04h 20m 03.25s -19° 19′ 50.1″) coincides with QSO (UV/GALEX, xray/eROSITA detection) in 2.8" from center of SWIFT error-box. The second one (04 20 23.62 -19 15 45.2) coincides with second QSO (see VIZIER for full information) in 2.5" from the center of Swift error-box. Both has complicated light curves without significant details at 23 oct 2025. Observation and reduction will be continued. [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov V., Kornilov V., Gorbovskoy E., Tiurina N., Kuznetsov A. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/42395. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40471] GRB 251022A: DDOTI Optical Detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42394 SUBJECT: GRB 251022A: DDOTI Optical Detection DATE: 25/10/23 11:09:52 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (U Roma), Simone Dichiara (Penn State University), Eleonora Troja (U Roma), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report: We observed the field of GRB 251022A detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 42380) and Fermi/LAT (Di Lalla et al., GCN Circ. 42384) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2025-10-23 UTC. DDOTI covered the entire Fermi/GBM error region from 07:00 UTC to 10:16 UTC (from T+8.4 h to T+ 11.7 h after the trigger), obtaining a total exposure of 80 minutes, alternating with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, our system automatically identified the fading nature of the optical candidate previously reported by GOTO (O’Neill et al., GCN Circ. 42386) with a preliminary AB magnitude of: w = 19.45 +/- 0.04. Further observations and analysis are on going. This value is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/42394. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40470] EP251021b/GRB 251021A: SVOM/VT optical candidate
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42393 SUBJECT: EP251021b/GRB 251021A: SVOM/VT optical candidate DATE: 25/10/23 10:18:34 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H.L. Li , L.P. Xin, Y. L. Qiu, C. Wu, 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, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observation to the field of EP251021b/GRB 251021A (Dai et al., GCN 42377; Ravasio et al., GCN 42379). The observation stared at 2025-10-22T20:09:33 UTC, I.e., 29.69 hours post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. Within the error box of EP-FXT (Dai et al., GCN 42377), an uncatalogued source was detected, compared to the Legacy survey DR9 catalog. The position is at R.A., Dec. = 306.745094, -38.3034732 degrees, equivalent to: R.A. (J2000) = 20:26:58.82 Dec. (J2000) = -38:18:12.50 with an uncertainty of 0.5 arcsec. The candidate's magnitudes are given below: Mid_time Band Exposure Time Magnitude (AB) 30.75 hour VT_B 45*70 sec 23.62+/-0.25 mag 30.75 hour VT_R 54*70 sec 22.80+/-0.20 mag Our photometry was derived in AB magnitude and not corrected for Galactic extinction. 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/42393. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40469] GRB 251023B / MAXI J0451+122: MAXI/GSC detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42392 SUBJECT: GRB 251023B / MAXI J0451+122: MAXI/GSC detection DATE: 25/10/23 10:08:49 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> C. Kang (Ehime U.), M. Nakajima (Nihon U.), Y. Kawakubo (AGU), H. Negoro, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, Y. Kondo, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima, Y. Ishihara (Chuo U.), M. Shidatsu, T. Nakamoto (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 08:49:03 UT on October 23, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (72.930 deg, 12.205 deg) = (04 51 43, +12 12 18) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.15 deg and 0.13 deg, respectively. The roll angle of long axis from the north direction is 71.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 341 +- 36 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (72.360, 11.893) deg = (04 49 26, +11 53 34) (J2000) (72.539, 11.711) deg = (04 50 09, +11 42 39) (J2000) (73.436, 12.551) deg = (04 53 44, +12 33 03) (J2000) (73.256, 12.734) deg = (04 53 01, +12 44 02) (J2000) There was no significant excess flux in the previous transit at 07:16 UT with an upper limit of 20 mCrab for each. View this GCN Circular online at https://gcn.nasa.gov/circulars/42392. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40468] EP251023a: NOT optical counterpart detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42391 SUBJECT: EP251023a: NOT optical counterpart detection DATE: 25/10/23 10:01:31 GMT FROM: liuxing(a)nao.cas.cn X. Liu, Z.P. Zhu, L.B. He, J. An, S.Q. Jiang, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), Niko Pyykkinen (NOT) report on behalf of a large collaboration: We observed the field of the EP251023a (Wu et al., GCN 42388) using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 05:55:11 UTC on 2025-10-23, i.e., 3.4 hours after the EP trigger, and a series of frames were obtained in the Sloan r- and z- bands. Within the EP/FXT localization error region (Wu et al., GCN 42388), the optical counterpart (Wortley et al., GCN 42387; Li et al., GCN 42389) is also clearly detected in both r- and z- bands with magnitudes as follows: T-mid (hr) | Filter | Exposure | Mag 3.49 | r | 3x200s | 18.57 +- 0.01 3.72 | z | 5x150s | 18.36 +- 0.01 calibrated against nearby Pan-STARRS stars and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/42391. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40467] Fermi GRB 251023A: Global MASTER-Net observations report
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42390 SUBJECT: Fermi GRB 251023A: Global MASTER-Net observations report DATE: 25/10/23 09:15:24 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 251023A ( Fermi GBM team, GCN 42385) errorbox 665 sec after notice time and 686 sec after trigger time at 2025-10-23 06:09:10 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 29 deg. The sun altitude is -40.0 deg. The galactic latitude b = -56 deg., longitude l = 180 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3021658 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 717 | 2025-10-23 06:09:10 | MASTER-OAFA | (02h 36m 41.44s , -06d 42m 24.3s) | C | 60 | 20.6 | 792 | 2025-10-23 06:10:25 | MASTER-OAFA | (02h 36m 48.65s , -06d 42m 09.1s) | C | 60 | 20.6 | 880 | 2025-10-23 06:11:53 | MASTER-OAFA | (02h 51m 27.06s , -04d 47m 02.9s) | C | 60 | 20.4 | 956 | 2025-10-23 06:13:09 | MASTER-OAFA | (02h 51m 25.90s , -04d 46m 08.3s) | C | 60 | 20.4 | 1045 | 2025-10-23 06:14:38 | MASTER-OAFA | (02h 29m 25.20s , -08d 34m 50.8s) | C | 60 | 20.3 | 1120 | 2025-10-23 06:15:53 | MASTER-OAFA | (02h 37m 24.96s , -08d 34m 57.2s) | C | 60 | 20.4 | 1197 | 2025-10-23 06:17:10 | MASTER-OAFA | (02h 29m 18.79s , -08d 34m 44.5s) | C | 60 | 20.3 | 1272 | 2025-10-23 06:18:25 | MASTER-OAFA | (02h 37m 30.89s , -08d 35m 06.2s) | C | 60 | 20.4 | 1353 | 2025-10-23 06:19:46 | MASTER-OAFA | (02h 44m 42.03s , -08d 34m 33.8s) | C | 60 | 20.6 | 1429 | 2025-10-23 06:21:02 | MASTER-OAFA | (02h 52m 48.50s , -08d 32m 57.2s) | C | 60 | 20.5 | 1503 | 2025-10-23 06:22:16 | MASTER-OAFA | (02h 44m 48.52s , -08d 34m 42.6s) | C | 60 | 20.7 | 1579 | 2025-10-23 06:23:32 | MASTER-OAFA | (02h 52m 49.17s , -08d 35m 05.7s) | C | 60 | 20.4 | 1654 | 2025-10-23 06:24:47 | MASTER-OAFA | (02h 44m 47.30s , -08d 35m 42.7s) | C | 60 | 20.6 | 1733 | 2025-10-23 06:26:07 | MASTER-OAFA | (02h 52m 04.95s , -06d 40m 17.4s) | C | 60 | 20.2 | 1895 | 2025-10-23 06:28:48 | MASTER-OAFA | (02h 51m 58.29s , -06d 40m 20.1s) | C | 60 | 20.2 | 1981 | 2025-10-23 06:30:14 | MASTER-OAFA | (02h 30m 14.33s , -10d 30m 32.8s) | C | 60 | 20.2 | 2057 | 2025-10-23 06:31:30 | MASTER-OAFA | (02h 38m 20.88s , -10d 28m 16.3s) | C | 60 | 20.5 | 2132 | 2025-10-23 06:32:45 | MASTER-OAFA | (02h 38m 22.92s , -10d 28m 22.0s) | C | 60 | 20.4 | 2215 | 2025-10-23 06:34:08 | MASTER-OAFA | (02h 59m 21.23s , -06d 41m 00.5s) | C | 60 | 20.0 | 2369 | 2025-10-23 06:36:42 | MASTER-OAFA | (02h 59m 20.42s , -06d 42m 09.2s) | C | 60 | 20.1 | 3339 | 2025-10-23 06:52:52 | MASTER-OAFA | (02h 39m 52.78s , -06d 23m 46.0s) | C | 60 | 19.5 | 3405 | 2025-10-23 06:53:58 | MASTER-OAFA | (02h 39m 52.75s , -06d 23m 44.1s) | C | 60 | 19.5 | 3470 | 2025-10-23 06:55:03 | MASTER-OAFA | (02h 39m 52.71s , -06d 23m 42.5s) | C | 60 | 19.6 | 3536 | 2025-10-23 06:56:09 | MASTER-OAFA | (02h 39m 52.68s , -06d 23m 41.2s) | C | 60 | 20.6 | 3601 | 2025-10-23 06:57:15 | MASTER-OAFA | (02h 39m 52.66s , -06d 23m 39.7s) | C | 60 | 20.6 | 3667 | 2025-10-23 06:58:20 | MASTER-OAFA | (02h 39m 52.65s , -06d 23m 38.5s) | C | 60 | 20.6 | 3734 | 2025-10-23 06:59:27 | MASTER-OAFA | (02h 39m 52.64s , -06d 23m 37.5s) | C | 60 | 20.6 | 3800 | 2025-10-23 07:00:33 | MASTER-OAFA | (02h 39m 52.62s , -06d 23m 36.4s) | C | 60 | 20.5 | 3865 | 2025-10-23 07:01:38 | MASTER-OAFA | (02h 39m 52.61s , -06d 23m 35.4s) | C | 60 | 20.5 | 3931 | 2025-10-23 07:02:44 | MASTER-OAFA | (02h 39m 52.60s , -06d 23m 34.4s) | C | 60 | 20.4 | 3997 | 2025-10-23 07:03:50 | MASTER-OAFA | (02h 39m 52.60s , -06d 23m 33.5s) | C | 60 | 20.5 | 4063 | 2025-10-23 07:04:56 | MASTER-OAFA | (02h 39m 52.59s , -06d 23m 32.6s) | C | 60 | 20.6 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/42390. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40466] EP251023a: GSP Optical Counterpart Detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42389 SUBJECT: EP251023a: GSP Optical Counterpart Detection DATE: 25/10/23 09:13:54 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> W. X. Li, S. J. Xue (NAOC); M. Andrews, J. Farah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report optical follow-up observations of EP251023a (Wu et al. GCN 42388) obtained with a Las Cumbres Observatory (LCO) 1-m telescope at Teide Observatory, Tenerife, ~3.6 hours after the EP-WXT trigger. We acquired 2 × 300 s exposures using the broad optical w band. The optical counterpart reported by Wortley et al. (GCN 42387) is detected. Preliminary photometry, calibrated to the r band, yields r ≈ 18.5 mag (not corrected for Galactic extinction). No known source is found at this position in the MPC or other major catalogs. These observations were taken as part of the Global Supernova Project (GSP). View this GCN Circular online at https://gcn.nasa.gov/circulars/42389. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40465] EP251023a: Einstein Probe detection of an X-ray transient
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42388 SUBJECT: EP251023a: Einstein Probe detection of an X-ray transient DATE: 25/10/23 09:11:35 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wu (NJU), D. F. Hu (PMO, CAS), H. N. Yang, T. Zhao, W. D. Zhang (NAO, CAS), on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP251023a. The transient triggered EP-WXT (ID: 01709247295) at 2025-10-23T02:31:09 (UTC). The WXT position of the source is R.A. = 127.151 deg, Dec. = 20.871 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). We performed a Target-of-Opportunity observation with the Follow-up X-ray Telescope on board EP. The observation began at 2025-10-23T07:44:08 (UTC).An uncatalogued X-ray source was detected within the WXT error circle at R.A. = 127.1368 deg, Dec. = 20.8634 deg (J2000), with a positional uncertainty of 20 arcsec in radius (90% confidence level, including both statistical and systematic uncertainties). The source is spatially consistent with the counterpart reported in optical bands (Wortley et al. GCN 42387). Further information will be updated when the telemetry data is received. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics). View this GCN Circular online at https://gcn.nasa.gov/circulars/42388. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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