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[vsnet-grb-info 41994] EP260227a: Thai National Telescope observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43877 SUBJECT: EP260227a: Thai National Telescope observations DATE: 26/02/28 12:41:42 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), S. Littlefair (Sheffield), V. Dhillon (Sheffield), I. Pelisoli (Warwick), J. van Dalen (Radboud), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), D. Mata-Sanchez (IAC and ULL), report on behalf of a larger collaboration: We observed the position of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the 2.4m Thai National Telescope equipped with the ULTRASPEC instrument. Observations were conducted in the KG5 wideband filter which approximately covers the wavebands of the SDSS ugr filters (https://tinyurl.com/kg5filter; Hardy et al. 2017). The total exposure time was 62 minutes with a mid time of 2026-02-27 22:28:00 UT (2.52 hr after trigger). We clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876) at a magnitude m_KG5 = 23.57 +/- 0.07 (AB) calibrated to Pan-STARRS and not corrected for Galactic extinction. The faint magnitude compared to other photometry is likely attributable to the peak response of the adopted filter in the blue and the red colour of the source, broadly consistent with the DLA suggested by Malesani et al (GCN 43876). View this GCN Circular online at https://gcn.nasa.gov/circulars/43877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41993] EP260227a: likely GTC/OSIRIS+ redshift z = 2.714
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43876 SUBJECT: EP260227a: likely GTC/OSIRIS+ redshift z = 2.714 DATE: 26/02/28 12:12:32 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), R. A. J. Eyles-Ferris (Leicester), J. van Dalen (Radboud), D. Mata-Sanchez (IAC and ULL), A. de Ugarte Postigo (LAM), N. Castro Rodríguez (GTC), A. L. Cabrera Lavers (GTC) report on behalf of a larger collaboration: We observed the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875) of EP260227a (Wang et al., GCN 43869) using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ spectrograph. Our observations consisted of 4 exposures of 900 s each, using grism R1000B which covers the wavelength range 3670 - 7700 Å. The observation start time was 2026-02-28 at 03:16 UT (~7.1 hr after the trigger). In the acquisition magnitude, we measure r = 21.55 +/- 0.07 AB at mid time 6.89 hr after trigger (consistent with the NOT measurement; Fu et al., GCN 43873). This value is calibrated against nearby objects from the Pan-STARRS catalog and not corrected for Galactic extinction. A faint trace is detected down to ~4000 Å, with an apparent spectral break around 4500 Å which is interpreted as due to H I and the onset of the Lyman forest. A few weak, narrow features, due to Si II 1259, Si II 1304, C II 1334, C IV 1548/1550, allow us to measure a redshift z = 2.714. View this GCN Circular online at https://gcn.nasa.gov/circulars/43876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41992] EP260227a: Liverpool Telescope observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43875 SUBJECT: EP260227a: Liverpool Telescope observations DATE: 26/02/28 10:29:52 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and N. R. Tanvir (Leicester) report on behalf of a larger collaboration: We observed the field of EP260227a (Wang et al., GCN 43869) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x150s exposures in each of the SDSS g’ r’ i’ z’ filters starting at 2026-02-28 04:25:03 UT, approximately 8.21 hours after the X-ray detection. We detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874) in the r’, i’ and z’ bands. We measure the following magnitudes calibrated to Pan-STARRS and not corrected for Galactic extinction. | t_mid (hours) | Filter | AB magnitude | | ------------- | ------ | ---------------- | | 8.35 | g’ | >22.28 (3-sigma) | | 8.63 | i’ | 21.12 +/- 0.08 | | 8.92 | r’ | 21.61 +/- 0.22 | | 9.21 | z’ | 20.74 +/- 0.11 | Compared to the photometry tabulated by Fu et al. (GCN 43873) and Mandarakas et al. (GCN 43874), our observations suggest the source has not faded significantly between these three epochs. View this GCN Circular online at https://gcn.nasa.gov/circulars/43875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41991] EP260227a: COLIBRÍ optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43874 SUBJECT: EP260227a: COLIBRÍ optical observations DATE: 26/02/28 09:50:46 GMT FROM: nikos.mandarakas(a)lam.fr Nikos Mandarakas (LAM), Camila Angulo (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (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) report: We imaged the field of the EP260227a (Wang et al., GCN Circ. 43869) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-28 07:51:00 to 08:49:14 UTC (from 11.64 to 12.61 hours after the trigger) and obtained 44 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 PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Eyles-Ferris et al. (GCN 43867), Li et al. (GCN 43868), Fu et al. (GCN 43873), at a preliminary magnitude of: r = 21.4644 +/- 0.0680 z = 20.8905 +/- 0.0745 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/43874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41990] EP260227a: NOT optical observations
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43873 SUBJECT: EP260227a: NOT optical observations DATE: 26/02/28 06:51:11 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> S.Y. Fu (HUST), L.B. He, Z.P. Zhu, J. An, X. Liu, S.Q. Jiang, D. Xu (NAOC), J. P. U. Fynbo (DAWN/NBI), A. L. Bouquin (NOT) report on behalf of a large collaboration: We observed the field of EP260227a (Wang et al., GCN 43869) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. The observations started at 02:20:46 UT, 2026-02-28, i.e. 6.14 hrs after the trigger, and we obtained 3x120 s frames each in Sloan g', r' and i' bands. The previously reported optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868) was detected in our stacked frames with the following AB magnitudes: | t-mid (hrs) | filter | mag | | ----------- |--------| ------------ | | 6.21 | g' | 21.40 ± 0.20 | | 6.33 | r' | 21.50 ± 0.20 | | 6.46 | i | 21.37 ± 0.12 | calibrated using nearby Pan-STARRS1 dr2 catalog, and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/43873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41989] GRB 260225A: SVOM/VT optical continued observations and upper limit
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43872 SUBJECT: GRB 260225A: SVOM/VT optical continued observations and upper limit DATE: 26/02/28 05:02:37 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, Z. H. Yao, H. L. Li, Y. L. Qiu, C. Wu, L. P. Xin, 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), L. Zhang (IHEP) report on behalf of the SVOM/VT team. SVOM/VT continued observations of GRB 260225A (sb26022501) triggered by SVOM/ECLAIRs (Ma et al., GCN 43829). With X-band data available, the optical counterpart (Ducoin et al., GCN 43837; Li et al., GCN 43838; Schneider et al., GCN 43861) within EP/FXT error box (Yang et al., GCN 43839) was detected in VT_B band. The magnitudes are: mid time (h) | exposure time (s) | band | mag (AB) -------------|-------------------|------|------------ 35.08 | 37*70 | VT_B | 23.6+/-0.3 35.04 | 27*70 | VT_R | >23.3 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/43872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41988] GRID detection of GRB 260223A
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43871 SUBJECT: GRID detection of GRB 260223A DATE: 26/02/28 04:46:33 GMT FROM: GRID Student Team at Tsinghua University <grid(a)tsinghua.edu.cn> GRID detection of GRB 260223A Longhao Li, Xinyu Liu, Chenyu Wang report on behalf of the GRID Collaboration: GRID-11B reports the detection of the long-duration GRB 260223A, which was also detected by Fermi GBM (GCN Circular 43808), MASTER-OAFA (GCN Circular 43809), BALROG (GCN Circular 43810), DDOTI (GCN Circular 43811), COLIBRÍ(GCN Circular 43812), SVOM (GCN Circular 43815), Glowbug (GCN Circular 43824) The event was triggered with GRID on 2026-02-23 at 04:11:09 UTC. The measured burst duration (T90) in the 30-2000 keV range is approximately 22.2 +/- 3.0 seconds. The GRID light curve of this event can be found at [GRID_GRB260223A_ltcv.pdf](https://mirrors.tuna.tsinghua.edu.cn/GRID/data/GRID-GCN/GRB260223A/GRID_GRB260223A_ltcv.pdf). GRID is a student-led project to monitor the transient gamma-ray sky with multiple detectors onboard different nanosatellites in the era of multi-messenger astronomy. For more information about GRID, please refer to the following references: https://doi.org/10.1007/s10686-019-09636-w and https://doi.org/10.1007/s10686-021-09819-4. View this GCN Circular online at https://gcn.nasa.gov/circulars/43871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41987] EP260227a: Global MASTER-Net observations report
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43870 SUBJECT: EP260227a: Global MASTER-Net observations report DATE: 26/02/28 04:45:41 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-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP260227a ( EP Team et al., GCN 43869) errorbox 14883 sec after trigger time at 2026-02-28 00:20:32 UT, with upper limit up to 21.0 mag. The observations began at zenith distance = 42 deg. The sun altitude is -44.5 deg. The galactic latitude b = 41 deg., longitude l = 345 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3160292 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.27s , -11d 34m 27.7s) | C | 60 | 19.3 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 420 | 20.1 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 50m 11.26s , -11d 34m 27.7s) | C | 1620 | 21.0 | 14913 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 60 | 19.2 | 14973 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 45.9s) | C | 180 | 19.8 | 15093 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 18.09s , -11d 18m 46.0s) | C | 420 | 20.0 | 15693 | 2026-02-28 00:20:32 | MASTER-SAAO | (14h 48m 17.70s , -11d 18m 51.8s) | C | 1620 | 20.7 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 50m 17.85s , -11d 34m 01.7s) | C | 60 | 19.3 | 15005 | 2026-02-28 00:22:04 | MASTER-SAAO | (14h 48m 24.61s , -11d 18m 21.0s) | C | 60 | 19.2 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 50m 14.69s , -11d 32m 38.3s) | C | 60 | 19.3 | 15097 | 2026-02-28 00:23:36 | MASTER-SAAO | (14h 48m 21.41s , -11d 16m 58.1s) | C | 60 | 19.2 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 50m 10.29s , -11d 34m 21.4s) | C | 120 | 19.7 | 15688 | 2026-02-28 00:32:56 | MASTER-SAAO | (14h 48m 17.24s , -11d 18m 39.5s) | C | 120 | 19.6 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 50m 16.17s , -11d 34m 15.7s) | C | 120 | 19.7 | 15840 | 2026-02-28 00:35:28 | MASTER-SAAO | (14h 48m 23.05s , -11d 18m 34.8s) | C | 120 | 19.6 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 120 | 19.8 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 50m 14.08s , -11d 32m 35.0s) | C | 360 | 20.2 | 15991 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 120 | 19.7 | 16111 | 2026-02-28 00:38:00 | MASTER-SAAO | (14h 48m 20.90s , -11d 16m 54.7s) | C | 360 | 20.1 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 50m 14.08s , -11d 33m 59.3s) | C | 120 | 19.8 | 16144 | 2026-02-28 00:40:32 | MASTER-SAAO | (14h 48m 20.83s , -11d 18m 19.0s) | C | 120 | 19.6 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 50m 18.07s , -11d 32m 38.9s) | C | 120 | 19.8 | 16296 | 2026-02-28 00:43:04 | MASTER-SAAO | (14h 48m 24.76s , -11d 16m 58.8s) | C | 120 | 19.7 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 120 | 19.8 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 50m 11.21s , -11d 33m 12.8s) | C | 600 | 20.2 | 16448 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.5s) | C | 120 | 19.7 | 16688 | 2026-02-28 00:45:36 | MASTER-SAAO | (14h 48m 17.86s , -11d 17m 32.4s) | C | 600 | 20.2 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 50m 10.14s , -11d 32m 11.3s) | C | 120 | 19.8 | 16600 | 2026-02-28 00:48:08 | MASTER-SAAO | (14h 48m 16.73s , -11d 16m 31.1s) | C | 120 | 19.7 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 50m 17.32s , -11d 33m 09.5s) | C | 840 | 20.2 | 16752 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 120 | 19.8 | 17112 | 2026-02-28 00:50:41 | MASTER-SAAO | (14h 48m 23.83s , -11d 17m 29.0s) | C | 840 | 20.2 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 50m 11.91s , -11d 34m 07.5s) | C | 120 | 19.8 | 16904 | 2026-02-28 00:53:13 | MASTER-SAAO | (14h 48m 18.35s , -11d 18m 26.9s) | C | 120 | 19.8 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 50m 17.31s , -11d 34m 04.1s) | C | 360 | 20.2 | 17056 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 120 | 19.8 | 17176 | 2026-02-28 00:55:45 | MASTER-SAAO | (14h 48m 23.70s , -11d 18m 23.5s) | C | 360 | 20.1 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 50m 14.06s , -11d 32m 19.1s) | C | 120 | 19.8 | 17208 | 2026-02-28 00:58:17 | MASTER-SAAO | (14h 48m 20.45s , -11d 16m 38.4s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 50m 14.01s , -11d 33m 49.8s) | C | 120 | 19.8 | 17360 | 2026-02-28 01:00:49 | MASTER-SAAO | (14h 48m 20.41s , -11d 18m 08.7s) | C | 120 | 19.8 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 50m 17.60s , -11d 32m 08.9s) | C | 360 | 20.2 | 17512 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.04s , -11d 16m 28.0s) | C | 120 | 19.8 | 17632 | 2026-02-28 01:03:21 | MASTER-SAAO | (14h 48m 24.05s , -11d 16m 27.9s) | C | 360 | 20.2 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 50m 10.38s , -11d 32m 57.2s) | C | 120 | 19.9 | 17664 | 2026-02-28 01:05:53 | MASTER-SAAO | (14h 48m 16.83s , -11d 17m 15.8s) | C | 120 | 19.8 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 48m 18.27s , -11d 16m 14.0s) | C | 120 | 19.9 | 17816 | 2026-02-28 01:08:25 | MASTER-SAAO | (14h 50m 11.81s , -11d 31m 55.4s) | C | 120 | 19.8 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 120 | 19.9 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 48m 22.89s , -11d 17m 11.4s) | C | 600 | 20.2 | 17968 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.2s) | C | 120 | 19.8 | 18208 | 2026-02-28 01:10:57 | MASTER-SAAO | (14h 50m 16.48s , -11d 32m 53.1s) | C | 600 | 20.3 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 48m 16.38s , -11d 18m 08.8s) | C | 120 | 19.9 | 18121 | 2026-02-28 01:13:29 | MASTER-SAAO | (14h 50m 10.00s , -11d 33m 50.7s) | C | 120 | 19.9 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 48m 23.93s , -11d 17m 39.4s) | C | 120 | 19.8 | 18273 | 2026-02-28 01:16:01 | MASTER-SAAO | (14h 50m 17.58s , -11d 33m 21.1s) | C | 120 | 19.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http : // www.pereplet.ru/lipunov/625.html View this GCN Circular online at https://gcn.nasa.gov/circulars/43870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41986] EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43869 SUBJECT: EP260227a: Einstein Probe detection of an X-ray transient and refined analysis DATE: 26/02/28 04:28:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO), H. C. Ding, T, Wu, Y. J. Yi (BNU), W. F. Wen (SZTU), Z. X. Ling(NAOC) 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 EP260227a. The transient triggered EP-WXT (ID: 01709258681) at 2026-02-27T20:12:29 (UTC). The WXT position of the source is R.A. = 223.101 deg, DEC = -11.408 deg (J2000) with an uncertainty of 2.586 arcmin in radius (90% C.L. statistical and systematic). The refined analysis of the WXT data shows that the event started at T0=2026-02-27T19:58:52 (UTC), and lasted for approximately 250 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 9.3×10^20 cm^-2 and a photon index of 0.8 (-0.6/+0.6). The derived average unabsorbed 0.5-4 keV flux is 4.1 (-1.3/+1.7) × 10^(-10) erg/s/cm^2. A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 223.1002 deg, DEC = -11.386 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.8 (-0.1/+0.1) × 10^21 cm^-2, and a photon index of 1.5 (-0.3/+0.3). The derived average unabsorbed 0.5-10 keV flux is 8.3 (-0.9/+1.2) ×10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. The optical counterpart was reported by Eyles-Ferris et al. (GCN 43867) and Li et al. (GCN 43868). 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/43869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41985] The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
by GCN Circulars 28 Feb '26

28 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43868 SUBJECT: The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart DATE: 26/02/28 02:12:37 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992(a)gmail.com> Wenxiong Li (NAOC), Iair Arcavi (TAU), Ido Keinan (TAU), Runduo Liang (NAOC), David Sand (U of Arizona) We observed the position of the EP-WXT trigger 01709258681 (EP260227a?) with a Las Cumbres 1m telescope at Siding Spring Observatory 2.6 hours after the Einstein Probe WXT trigger and again 4 hours after the trigger. We took 2x300s exposures in each visit in the broad optical w band. We find a rapidly fading source consistent with the position reported by Eyles-Ferris et al. (GCN 43867) and measure the following preliminary photometry calibrated to the r band: Epoch 1: MJD 61098.954 Mag 20.28 ± 0.09 Epoch 2: MJD 61099.011 Mag 21.08 ± 0.10 View this GCN Circular online at https://gcn.nasa.gov/circulars/43868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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