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

[vsnet-grb-info 41909] EP-WXT01709258519: Xinglong optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43799 SUBJECT: EP-WXT01709258519: Xinglong optical upper limit DATE: 26/02/21 21:25:15 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration: Following the detection of EP-WXT01709258519, we observed the field of EP-WXT01709258519 ( +11:05:00.96 +38:12:32.40 ) using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s clear-band frames with a median time of 2026-02-21T19:28:39, 11 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (WXT01709258519), down to 3-sigma limiting magnitudes of 21.01 mag for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43799. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41908] EP260221a: Xinglong optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43798 SUBJECT: EP260221a: Xinglong optical upper limit DATE: 26/02/21 20:39:37 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Yuguang-Sun (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration: Following the detection of EP260221a (WXT01709258521; Zhang et al., GCN 43791), we observed the field of EP260221a using the 0.8-m and 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x600s g-band frames by using 0.8-m with a median time of 2026-02-21T17:18:37.349, 4 hrs after the EP trigger and 3x600s clear-band frames by using 2.16-m with a median time of 2026-02-21T19:09:10, 6 hrs after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 20 arcsec EP/FXT error circle (Zhang et al., GCN 43791), down to 3-sigma limiting magnitudes of g-band ~15.48 mag for 0.8-m and clear-band 20.71 mag for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43798. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41907] Fermi GRB 260221A: Global MASTER-Net observations report
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43797 SUBJECT: Fermi GRB 260221A: Global MASTER-Net observations report DATE: 26/02/21 19:00:32 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 260221A ( Fermi GBM team, GCN 43795) errorbox 1055 sec after notice time and 1088 sec after trigger time at 2026-02-21 16:41:00 UT, with upper limit up to 12.4 mag. The observations began at zenith distance = 74 deg. The sun altitude is -21.2 deg. MASTER-Tunka robotic telescope located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 260221A errorbox 5336 sec after notice time and 5369 sec after trigger time at 2026-02-21 17:52:21 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 30 deg. The sun altitude is -49.0 deg. The galactic latitude b = 61 deg., longitude l = 96 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3149550 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1118 | 2026-02-21 16:41:00 | MASTER-Kislovodsk | (13h 44m 40.23s , +50d 10m 34.6s) | C | 60 | 12.4 | 1657 | 2026-02-21 16:49:59 | MASTER-Kislovodsk | (13h 49m 30.45s , +48d 15m 50.3s) | C | 60 | 12.0 | 5399 | 2026-02-21 17:52:21 | MASTER-Tunka | (14h 07m 03.52s , +53d 13m 43.3s) | C | 60 | 15.9 | 5399 | 2026-02-21 17:52:21 | MASTER-Tunka | (14h 07m 59.88s , +53d 08m 17.6s) | C | 60 | 16.0 | 5473 | 2026-02-21 17:53:35 | MASTER-Tunka | (14h 20m 10.09s , +51d 18m 47.8s) | C | 60 | 15.9 | 5473 | 2026-02-21 17:53:35 | MASTER-Tunka | (14h 21m 02.69s , +51d 13m 17.9s) | C | 60 | 15.9 | 5547 | 2026-02-21 17:54:48 | MASTER-Tunka | (14h 19m 45.21s , +55d 07m 57.6s) | C | 60 | 15.6 | 5547 | 2026-02-21 17:54:48 | MASTER-Tunka | (14h 20m 44.18s , +55d 02m 30.8s) | C | 60 | 15.5 | 5621 | 2026-02-21 17:56:03 | MASTER-Tunka | (14h 10m 13.14s , +49d 24m 43.5s) | C | 60 | 15.2 | 5621 | 2026-02-21 17:56:03 | MASTER-Tunka | (14h 11m 03.71s , +49d 19m 11.0s) | C | 60 | 15.1 | 5695 | 2026-02-21 17:57:17 | MASTER-Tunka | (14h 32m 57.97s , +53d 06m 17.2s) | C | 60 | 14.4 | 5696 | 2026-02-21 17:57:17 | MASTER-Tunka | (14h 32m 03.19s , +53d 11m 49.2s) | C | 60 | 14.5 | 5770 | 2026-02-21 17:58:31 | MASTER-Tunka | (13h 56m 11.18s , +51d 17m 55.4s) | C | 60 | 15.6 | 5770 | 2026-02-21 17:58:31 | MASTER-Tunka | (13h 57m 05.52s , +51d 12m 26.1s) | C | 60 | 15.5 | 5844 | 2026-02-21 17:59:46 | MASTER-Tunka | (13h 53m 32.03s , +55d 08m 06.5s) | C | 60 | 15.3 | 5844 | 2026-02-21 17:59:46 | MASTER-Tunka | (13h 54m 33.24s , +55d 02m 18.8s) | C | 60 | 15.2 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43797. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41906] ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43796 SUBJECT: ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations DATE: 26/02/21 17:13:45 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Nikos Mandarakas (LAM), Asuka Kuwata (UNAM), Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Noémie Globus (UNAM), Benjamin Schneider (LAM), 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), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM) report: We observed the field of AT2026dbl discovered by ZTF (Pérez-Fournon et al., TNSTR No. 291251) and identified as a LFBOT candidate by Einstein Probe (Jayaraman et al., TNSAN No. 2026-38) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir. We observed from 2026-02-21 06:00:34 to 07:13:21 UTC (from 6.90 to 6.95 days after discovery date) and obtained 20, 20, 19 and 60 minutes of exposure time in the g, r, i and z filters, respectively. The data were reduced, calibrated and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and was not corrected for Galactic extinction. In our images, we detect AT2026dbl at the position reported by Pérez-Fournon et al. (TNSTR No. 291251) about 2” away from a bright galaxy (with reported magnitudes of g = 21.11 +/- 0.03, r = 20.52 +/- 0.04, i= 20.37 +/- 0.04, z = 20.31 +/- 0.05 in the Legacy Survey DR10; Dey et al. 2019). At the reported redshift of z = 0.19 (Wise et al., TNSCR No. 22993), this corresponds to an offset of about 6 kpc from the center of the galaxy. Subsequently, after the subtraction against PanSTARRS images, we measure preliminary magnitudes of: g = 20.62 +/ - 0.03 r = 20.96 +/ - 0.03 i = 21.21 +/ - 0.06 z = 21.41 +/ - 0.16 Considering the redshift (z=0.19) reported by Wise et al. (TNSCR No. 22993), we find that these magnitudes are brighter than expected for the prototypical LFBOT AT2018cow at this redshift. 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/43796. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41905] GRB 260221A: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43795 SUBJECT: GRB 260221A: Fermi GBM Final Real-time Localization DATE: 26/02/21 16:33:30 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 16:22:52 UT on 21 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260221A (trigger 793383777.240036 / 260221683). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 213.3, Dec = 51.9 (J2000 degrees, equivalent to J2000 14h 13m, 51d 53'), with a statistical uncertainty of 6.6 degrees. The angle from the Fermi LAT boresight is 128.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221683/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221683/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221683/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43795. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41904] EP260221a: GOTO optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43794 SUBJECT: EP260221a: GOTO optical upper limit DATE: 26/02/21 14:41:25 GMT FROM: Amit Kumar at The Open University, UK <amitkundu515(a)gmail.com> A. Kumar, G. Ramsay, D. O’Neill, K. Ulaczyk, S. Moran, B. P. Gompertz, R. Starling, M. Wortley, M. Kennedy, K. Ackley, M. Dyer, J. Lyman, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, M. Pursiainen, on behalf of GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) that serendipitously covered the field of EP/WXT detected EP260221a (WXT01709258521; Zhang et al., GCN 43791). Observations covering the localisation area were taken at 2026-02-21 13:15:35 UT (+1.54h post trigger) utilising GOTO-South. Each observation consisted of 4x45s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. No new transients that could be credibly associated with EP260221a were detected down to a 3-sigma depth of 20.9 mag (AB); see also Mandarakas et al., GCN 43793. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/43794. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41903] EP260221a: COLIBRÍ optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43793 SUBJECT: EP260221a: COLIBRÍ optical upper limit DATE: 26/02/21 14:25:23 GMT FROM: nikos.mandarakas(a)lam.fr EP260221a: COLIBRÍ optical upper limit Nikos Mandarakas (LAM), Asuka Kuwata (UNAM), Benjamin Schneider (LAM), 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), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM) and Antonio de Ugarte Postigo (LAM) report: We imaged 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 2026-02-21T12:22:07 to 2026-02-21T13:05:02 UTC (from 38.87 to 81.80 minutes after the trigger, 30 seconds after the GCN notice) and obtained 32 minutes of simultaneous exposure in the r and z filters. 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 Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the FXT source position (Zhang et al., GCN Circ. 43791) down to the following 5-sigma limit: r > 23.1 z > 21.8 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/43793. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41902] SVOM alert sb26021801: LCO optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43792 SUBJECT: SVOM alert sb26021801: LCO optical upper limit DATE: 26/02/21 14:13:23 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), L.P. Xin (NAOC), and X.H. Han (NAOC) report on behalf of the SVOM mission team: We observed the field of sb26021801 (TAN et al., GCN 43778) with the LCO 1-m telescope, equipped with the Sinistro instrument, at both the Cerro Tololo Interamerican Observatory and the Teide Observatory (Tenerife). Our observation started on 2026-02-18 at 06:33:39 UT (about 78.35 min after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters. In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box, in agreement with Fortin et al. (GCN 43783) and Konno et al.(GCN 43784). We measure the following upper limit calibrated against the PanSTARSS DR1 catalog, and not corrected for Galactic extinction: r > 22.1 AB (5-sigma, mid-time 83.35 min after the trigger) z > 20.2 AB (5-sigma, mid-time 85.38 min after the trigger). This project is funded by the SVOM collaboration. View this GCN Circular online at https://gcn.nasa.gov/circulars/43792. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41901] EP260221a: Einstein Probe detection of an X-ray transient
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43791 SUBJECT: EP260221a: Einstein Probe detection of an X-ray transient DATE: 26/02/21 13:34:01 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.-H. Zhang, X. X. Sun, Tian-Yu Liu, Y. Liu (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 EP260221a. The transient triggered EP-WXT (ID: 01709258521) at 2026-02-21T11:43:14 (UTC). The WXT position of the source is R.A. = 178.749 deg, DEC = -20.978 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed at 2026-02-21T12:44:34 (UTC). Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 178.7568 deg, DEC = -20.9847 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). 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/43791. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41900] The EP-WXT trigger 01709258519 is likely caused by Mrk 421
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43790 SUBJECT: The EP-WXT trigger 01709258519 is likely caused by Mrk 421 DATE: 26/02/21 10:01:16 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> M.-H. Zhang, X. X. Sun, Tian-Yu Liu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709258519 at the time of 2026-02-21T08:28:55 is likely associated with the known source Mrk 421. 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/43790. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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