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

[vsnet-grb-info 40480] IPN triangulation of GRB 251016B
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42403 SUBJECT: IPN triangulation of GRB 251016B DATE: 25/10/23 16:17:46 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo and HEND/Mars Odyssey teams, J. Benkhoff on behalf of the BepiColombo team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi-GBM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 251016B (Ferm-GBM detection: The Fermi GBM team, GCN 42316; Godwin et al., GCN 42383; CALET-GBM detection: Yamaoka et al., GCN 42320; AstroSat-CZTI detection: Harsha et al., GCN 42324) was detected by Fermi (GBM trigger 782351945), CALET (GBM), AstroSat (CZTI), Konus-Wind, Swift (BAT), Mars-Odyssey (HEND), and BepiColombo (MGNS), at about 86340 s UT (23:59:00). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 180.582 (12h 02m 20s) +57.856 (+57d 51' 21") Corners: 173.603 (11h 34m 25s) +54.048 (+54d 02' 53") 182.331 (12h 09m 19s) +58.703 (+58d 42' 09") 191.445 (12h 45m 47s) +61.827 (+61d 49' 37") 178.988 (11h 55m 57s) +57.018 (+57d 01' 07") --------------------------------------------- The error box area is 2295 sq. arcmin, and its maximum dimension is 12.186 deg (the minimum one is 5 arcmin). The Sun distance was 69 deg. This localization may be improved. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB251016_T86340/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/42403. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40479] GRB 251023B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42402 SUBJECT: GRB 251023B: CALET Gamma-Ray Burst Monitor detection DATE: 25/10/23 16:16:02 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Nakahira (JAXA), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The long GRB 251023B (MAXI/GSC Detection: Kang et al., GCN Circ 42392) was detected in the ground analysis of the CALET Gamma-ray Burst Monitor (CGBM) data around 08:49:03 on 23 October 2025 (referenced to the MAXI detection: GCN Circ. 42392). (https://cgbm.calet.jp/cgbm_trigger/flight/1445244062/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure that starts at T-31.7 sec and ends at T+8.2 sec. The T90 and T50 durations measured by the HXM2 data are 34.9 +/- 4.2 sec and 16.7 +/- 2.2 sec (7-100 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1445244062/ The CALET data used in this analysis are provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/42402. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40478] EP#01709247298: Swift-XRT counterpart detection
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42401 SUBJECT: EP#01709247298: Swift-XRT counterpart detection DATE: 25/10/23 15:35:42 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 Einstein Probe/WXT-detected source EP#01709247298, collecting 1.6 ks of Photon Counting (PC) mode data between T0+6.6 ks and T0+8.3 ks after the trigger. A likely counterpart has been found. This source is 43 arcmin from the position of the MAXI-detected transient GRB 251023B / MAXI J0451+122 (Kang et al., GCN Circ. 42392), well outside their error region, thus its association, while likely on temporal grounds, remains unconfirmed. The details of this source are: Source 1 (SWIFT J045400.4+123929): ================================== RA (J2000.0): 73.5018 = 04 54 00.43 Dec (J2000.0): +12.6583 = +12 39 29.9 Error: 3.7 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 22 arcsec from the Einstein Probe/WXT position. Mean rate: 0.152 +/- 0.011 ct s^-1 Mean flux: (5.94 +/- 0.44)e-12 erg cm^-2 s^-1 Peak rate: 0.221 +/- 0.049 ct s^-1 Peak flux: (8.6 +/- 1.9)e-12 erg cm^-2 s^-1 ECF: 3.91e-11 erg cm^-2 ct^-1 assuming NH=3.15e+21 cm^-2, gamma=1.97 determined from a spectral fit. XMM UL: 2.3e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 3.2-sigma above this 3-sigma upper limit. 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/EP/EP_FIELD00077. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42401. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40477] EP251023a: COLIBRÍ optical observations
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42400 SUBJECT: EP251023a: COLIBRÍ optical observations DATE: 25/10/23 15:22:43 GMT FROM: nikos.mandarakas(a)lam.fr 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 (UNAM), 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 EP251023a (Wu et al., GCN Circ. 42388) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-23 09:29 to 10:57 UTC (from 7.0 to 8.4 hours after the trigger) and obtained 32 minutes of simultaneous exposure in the r and z filters, alternating with other observations. 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 firstly identified by GOTO (Wortley et al., GCN Circ. 42387) and subsequently reported by Las Cumbres Observatory (Li et al., GCN Circ. 42389) and NOT (Liu et al., GCN Circ. 42391) at preliminary magnitudes of: r = 18.82 +/- 0.01 z = 18.52 +/- 0.01 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/42400. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40476] GRB 251013C: further SAO RAS optical observations
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42399 SUBJECT: GRB 251013C: further SAO RAS optical observations DATE: 25/10/23 14:44:06 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova, V. V. Vlasyuk (SAO RAS) report on behalf of GRB follow-up collaboration. We observed the field of the GRB 251013C (The Fermi GBM team, GCN 42221; Rakotondrainibe et al., GCN 42222) with the 1-m SAO RAS telescope Zeiss-1000 equipped with the CCD-photometer on October 20 and 21 nights. 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; Volnova et al., GCN 42396) is clearly detected in the stacked images with the following brightness. Date UT start t-T0 Exp. Filter OT Err. UL (mid, d) (s) 2025.10.20 19:59:38 7.12682 13 x 300 Rc 21.61 +/- 0.11 22.7 2025.10.21 17:02:31 8.01103 19 x 300 Rc 21.80 +/- 0.10 23.0 Preliminary photometry is based on the nearby SDSS objects (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/42399. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40475] EP251023a: Keck/LRIS spectroscopic redshift z=2.232
by GCN Circulars 23 Oct '25

23 Oct '25

TITLE: GCN CIRCULAR NUMBER: 42398 SUBJECT: EP251023a: Keck/LRIS spectroscopic redshift z=2.232 DATE: 25/10/23 14:39:53 GMT FROM: Ryan Chornock at UC Berkeley <chornock(a)berkeley.edu> R. Chornock (UC Berkeley) reports: We observed the optical afterglow (Wortley et al., GCN 42387; Li et al., GCN 42389; Liu et al. GCN 42391) of the X-ray transient EP251023a (Wu et al., GCN 42388) using the Low-Resolution Imaging Spectrometer on the Keck-I telescope at a mean time of 13:26UT on 2025 October 23 (~10.9 hours after the EP trigger). Observations covered the range 3100-10300 Angstroms. The afterglow remains bright and the continuum is well detected across the full spectral range. Multiple absorption systems are present, but the highest redshift absorber has many absorption lines (including Lyman-alpha, Si II, Si II*, O I, O I*, C II, Si IV, C IV, Fe II, Mg I and Mg II) present at a common redshift of z=2.232+/-0.001. View this GCN Circular online at https://gcn.nasa.gov/circulars/42398. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[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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