February 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41929] GRB 260223A: SVOM/VT optical observation
by GCN Circulars 24 Feb '26

24 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43816 SUBJECT: GRB 260223A: SVOM/VT optical observation DATE: 26/02/24 03:00:50 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of GRB 260223A detected by Fermi (Fermi GBM team et al., GCN 43808; Preis et al., GCN 43810) and SVOM/GRM (sb26022301, Wang et al., GCN 43815). The observation started on 2026-02-23T15:26:24 UTC, i.e. about 11.26 hours after the trigger time of GBM, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Becerra et al., GCN 43811; Postigo et al., GCN 43812; Postigo et al., GCN 43814) were detected in both channels. The measurements in AB magnitude are derived as follows: Mid time | Band | Exposure Time | Magnitude (AB) 14.893 hours VT_R 27*70 sec 19.66 +/- 0.06 mag 14.864 hours VT_B 28*70 sec 20.50 +/- 0.08 mag The counterpart showed a power-law decay with the index of -1.1 during our observation from 11.40 hours to 15.14 hours. Our photometry was 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/43816. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41928] GRB 260223A: SVOM/GRM observation
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43815 SUBJECT: GRB 260223A: SVOM/GRM observation DATE: 26/02/23 17:10:56 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260223A (SVOM trigger reference: sb26022301) at 2026-02-23T04:11:28.000 (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #43808). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 26 +8/-4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260223A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 110.5, Dec = -29.4, Error = 1.7, GCN #43808), is located at about 96 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. ECLAIRs was not collecting data at the time of this burst. With this localization, the time-averaged spectrum from T0-23 to T0+15 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.29 +0.10/-0.11 and the cutoff energy, parameterized as Epeak, is 194 +33/-25 keV. The event fluence (10-1000 keV) in this time interval is (2.27 +0.13/-0.13)E-05 erg/cm^2. The 1s peak spectrum, measured from T0-0 to T0+1 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.39 +0.10/-0.11 and the cutoff energy, parameterized as Epeak, is 741 +456/-228 keV. The flux (10-1000 keV) in this time interval is (3.03 +0.18/-0.18)E-06 erg/cm^2/s. The localization of GRB 260223A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260223A_amati.png The localization of GRB 260223A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260223A_yonetoku.png The SVOM/VT ToO has been performed. 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/43815. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41927] GRB 260223A: COLIBRÍ further optical observations and a brightening
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43814 SUBJECT: GRB 260223A: COLIBRÍ further optical observations and a brightening DATE: 26/02/23 14:15:07 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Antonio de Ugarte Postigo (LAM), Leonardo García García (UNAM), Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Camila Angulo (UNAM), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Benjamin Schneider (LAM) report: We continued to observe the field of the Fermi GRB 260223A (Fermi GBM team et al., GCN Circ. 43808) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-23 06:16 to 07:48 UTC (from 2.08 to 3.67 hours after the trigger) and obtained near-continuous, alternating 60-second exposures in the grizy filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR2, is in the AB system, and is not corrected for Galactic extinction (A_V = 0.68, Schlafly et al. 2011). The optical counterpart reported by Becerra et al. (GCN Circ. 43811) and confirmed by our earlier observations (de Ugarte Postiga et al. GCN Circ 43812) is observed to brighten continuously during our extended observations, rising from i = 18.55 at the start of our observations to i = 18.15 at the end. Similar behaviour is seen in the other bands. 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/43814. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41926] EP260221a: Optical upper limit with Kinder observations
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43813 SUBJECT: EP260221a: Optical upper limit with Kinder observations DATE: 26/02/23 09:42:06 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> Y.-H. Lee, A. Aryan, H.-Y. Hsiao, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, M.-H. Lee, C.-H. Lai, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, C.-S. Lin, H.-C. Lin, 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 EP260221a (Zhang et al., GCN 43791 and Liu et al., GCN 43802) using the 40cm SLT at the Lulin observatory, as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations in r-band started at 13:51 UTC on 21st of February 2026 (MJD 61092.577), 2.13 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 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. Neither in the stacked frame nor in the difference image do we detect the optical counterpart candidate proposed by Watson et al. (GCN 43806) and confirmed by Eyles-Ferris et al. (GCN 43807). Clearly, our non-detection is attributable to the shallower detection limits in our observations. Moreover, we used AutoPhOT to perform PSF photometry. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61092.577 | 2.13 | 300 * 24 | >20.7 | 3".42 | 2.11 The non-detection in our observations is consistent with the reports by Mandarakas et al. (GCN 43793), Kumar et al. (GCN 43794), and Min-He et al. (GCN 43798). 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 = 0.075 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 are presented 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/43813. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41925] GRB 260223A: COLIBRÍ optical observations
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43812 SUBJECT: GRB 260223A: COLIBRÍ optical observations DATE: 26/02/23 08:22:07 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> Antonio de Ugarte Postigo (LAM), Leonardo García García (UNAM), Rosa L. Becerra (UNAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Benjamin Schneider (LAM) report: We imaged the field of the Fermi GRB 260223A (Fermi GBM team et al., GCN Circ. 43808) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-23 06:16:02 to 06:26:30 UTC (from 2.081 to 2.256 hours after the trigger) and obtained 3x60 s of simultaneous exposure in the grizy filters. The data were reduced, coadded and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR2, is in the AB system, and is not corrected for Galactic extinction (A_V = 0.68, Schlafly et al. 2011). We detected the optical counterpart reported by Becerra et al., GCN Circ. 43811, at preliminary magnitudes of: g = 19.44 +/- 0.06 r = 18.92 +/- 0.04 i = 18.52 +/- 0.05 z = 18.27 +/- 0.04 y = 18.23 +/- 0.07 Further observations are ongoing. 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/43812. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41924] GRB 260223A: DDOTI Optical Candidate
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43811 SUBJECT: GRB 260223A: DDOTI Optical Candidate DATE: 26/02/23 05:44:22 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observe the field of GRB 260223A (Fermi Team, GCN Circ. 43808) 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 2026-02-23 UTC. DDOTI observed from 04:26 UTC to 04:36 UTC (T+14.9 minutes to T+25.3 minutes after the trigger), with a total exposure time of 8 minutes. Comparing our observations with the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect an uncatalogued fading source at: RA = 07:24:21.20 (111.0883 deg) DEC = -29:25:04.4 (-29.4179 deg) at a preliminary AB magnitude of: w = 18.30 +/- 0.13 at T + 14.9 minutes. From our observations, we estimate a temporal decay of approximately −0.6. We suggest that this source is the optical counterpart of GRB 260223A and encourage follow-up observations. 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/43811. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41923] GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43810 SUBJECT: GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174) DATE: 26/02/23 05:37:50 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 793512674 at 04:11:09 on 23 Feb. 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 109.5 deg Decl.(2000.0) = -28.9 deg The 1 sigma statistical error radius is 1.7 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260223174/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260223174/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260223174/json View this GCN Circular online at https://gcn.nasa.gov/circulars/43810. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41922] Fermi GRB 260223A: Global MASTER-Net observations report
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43809 SUBJECT: Fermi GRB 260223A: Global MASTER-Net observations report DATE: 26/02/23 05:15:25 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 [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260223A ( Fermi GBM team, GCN 43808) errorbox 123 sec after notice time and 154 sec after trigger time at 2026-02-23 04:13:44 UT, with upper limit up to 19.8 mag. The observations began at zenith distance = 32 deg. The sun altitude is -48.2 deg. The galactic latitude b = -7 deg., longitude l = 243 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3152151 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 170 | 2026-02-23 04:13:44 | MASTER-OAFA | (07h 21m 14.73s , -29d 00m 58.9s) | C | 30 | 19.3 | 210 | 2026-02-23 04:14:20 | MASTER-OAFA | (07h 21m 14.73s , -29d 00m 58.0s) | C | 40 | 19.5 | 262 | 2026-02-23 04:15:07 | MASTER-OAFA | (07h 21m 14.77s , -29d 00m 57.4s) | C | 50 | 19.6 | 324 | 2026-02-23 04:16:03 | MASTER-OAFA | (07h 21m 14.79s , -29d 00m 56.9s) | C | 60 | 18.9 | 395 | 2026-02-23 04:17:09 | MASTER-OAFA | (07h 21m 14.83s , -29d 00m 56.3s) | C | 70 | 19.8 | 603 | 2026-02-23 04:20:17 | MASTER-OAFA | (07h 22m 38.12s , -29d 04m 33.0s) | C | 110 | 19.3 | 730 | 2026-02-23 04:22:15 | MASTER-OAFA | (07h 22m 38.17s , -29d 04m 33.2s) | C | 130 | 19.4 | 882 | 2026-02-23 04:24:31 | MASTER-OAFA | (07h 22m 38.28s , -29d 04m 33.1s) | C | 160 | 19.5 | 998 | 2026-02-23 04:27:17 | MASTER-OAFA | (07h 22m 38.38s , -29d 04m 32.8s) | C | 60 | 18.9 | 1063 | 2026-02-23 04:28:23 | MASTER-OAFA | (07h 22m 38.43s , -29d 04m 32.7s) | C | 60 | 19.2 | 1129 | 2026-02-23 04:29:29 | MASTER-OAFA | (07h 22m 38.49s , -29d 04m 32.7s) | C | 60 | 19.1 | 1196 | 2026-02-23 04:30:35 | MASTER-OAFA | (07h 22m 38.53s , -29d 04m 32.7s) | C | 60 | 19.1 | 1261 | 2026-02-23 04:31:40 | MASTER-OAFA | (07h 22m 38.57s , -29d 04m 32.8s) | C | 60 | 18.9 | 1326 | 2026-02-23 04:32:46 | MASTER-OAFA | (07h 22m 38.61s , -29d 04m 33.1s) | C | 60 | 18.9 | 1393 | 2026-02-23 04:33:52 | MASTER-OAFA | (07h 22m 38.66s , -29d 04m 33.1s) | C | 60 | 19.0 | 1458 | 2026-02-23 04:34:58 | MASTER-OAFA | (07h 22m 38.71s , -29d 04m 33.0s) | C | 60 | 18.8 | 1524 | 2026-02-23 04:36:04 | MASTER-OAFA | (07h 22m 38.76s , -29d 04m 33.3s) | C | 60 | 19.2 | 1591 | 2026-02-23 04:37:10 | MASTER-OAFA | (07h 22m 38.81s , -29d 04m 33.5s) | C | 60 | 19.2 | 1656 | 2026-02-23 04:38:15 | MASTER-OAFA | (07h 22m 38.85s , -29d 04m 33.5s) | C | 60 | 19.2 | 1721 | 2026-02-23 04:39:21 | MASTER-OAFA | (07h 22m 38.89s , -29d 04m 33.7s) | C | 60 | 19.1 | 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/43809. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41921] GRB 260223A: Fermi GBM Final Real-time Localization
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43808 SUBJECT: GRB 260223A: Fermi GBM Final Real-time Localization DATE: 26/02/23 04:20:24 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 04:11:09 UT on 23 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260223A (trigger 793512674.810552 / 260223174). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 110.5, Dec = -29.4 (J2000 degrees, equivalent to J2000 07h 21m, -29d 23'), with a statistical uncertainty of 1.7 degrees. The angle from the Fermi LAT boresight is 33.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260223174/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260223174/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260223174/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43808. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41920] EP260221a: COLIBRÍ optical counterpart candidate
by GCN Circulars 23 Feb '26

23 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43806 SUBJECT: EP260221a: COLIBRÍ optical counterpart candidate DATE: 26/02/22 17:22:21 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Antonio de Ugarte Postigo (LAM), Rosa L. Becerra (UNAM), Benjamin Schneider (LAM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Fredd Sánchez Álvarez (UNAM) report: We reobserved the field of the EP260221a (Zhang et al., GCN Circ. 43791) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-22 05:55 to 10:54 UTC (from 18.20 to 23.20 hours after the trigger) and obtained 71 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. When we subtract the r-band image from our second epoch from the one from our first (Mandarakas et al., GCN Circ. 43793), we detect a residual source with a SNR of about 5 at: RA (J2000) = 11:55:01.22 = 178.7551 deg Dec (J2000) = -20:58:57.6 = -20.9827 deg The uncertainty on this position is 0.5 arcsec. The source is also seen in subtractions against PS1 images, but at a lower significance, and lies within the enhanced FXT uncertainty region (Liu et al., GCN Circ. 43802). We suggest it is the optical counterpart of the EP source. We notice that these coordinates are consistent with the position of a galaxy present in the Legacy Survey catalog (Dey et al., 2019) with magnitudes g = 23.68 +/- 0.17, r = 23.29 +/- 0.18, i = 22.41 +/- 0.12, and z = 21.90 +/- 0.15 and with a photo-z = 1.22 +/- 0.55. In the r band, the total magnitude of the galaxy and the candidate counterpart faded from 22.54 +/- 0.08 in our first epoch to 23.39 +/- 0.15 in our second epoch (a difference of 0.85 +/- 0.17) and in the z band it faded from 22.03 +/- 0.17 to 22.69 +/- 0.16 (a difference of 0.66 +/- 0.23). These fadings have significances of 5.0- and 2.8-sigma, respectively. The detection of this candidate in r as well as z is consistent with the photo-z of the coincident galaxy Therefore, we suggest that this galaxy might be the host. The non-detection of this source in deep imaging by Levan et al. (GCN Circ. 43805) suggests that it faded very quickly. This is perhaps consistent with temporal decay estimated from the two values reported in X-rays by (Liu et al., GCN Circ. 43802) alpha of approximately 2.2 and suggests the presence of an early jet break. 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/43806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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