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May 2026

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[vsnet-grb-info 42560] EP260429a: Global MASTER-Net observations report
by GCN Circulars 01 May '26

01 May '26

TITLE: GCN CIRCULAR NUMBER: 44437 SUBJECT: EP260429a: Global MASTER-Net observations report DATE: 26/05/01 10:09:31 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-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the EP260429a ( EP Team et al., GCN 44426) errorbox 1 days 24768 sec after notice time and 1 days 69627 sec after trigger time at 2026-05-01 10:01:38 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 44 deg. The sun altitude is -29.1 deg. The galactic latitude b = 30 deg., longitude l = 2 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3281864 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 156117 | 2026-05-01 10:01:38 | MASTER-OAGH | (16h 00m 56.52s , -09d 05m 48.0s) | C | 180 | 18.6 | 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/44437. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42559] EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
by GCN Circulars 01 May '26

01 May '26

TITLE: GCN CIRCULAR NUMBER: 44436 SUBJECT: EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations DATE: 26/05/01 07:13:34 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Wang (PMO, CAS; UCB), Y. L. Wang (NAO, CAS; ICE, CSIC), G. J. Yang, C.C Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260430a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 44427) at 2026-04-30T02:32:47 (UTC). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 0.3× 10^21 cm^-2, and a photon index of 0.84 (+0.19/-0.18). The derived average unabsorbed 0.5-4 keV flux is 4.63 (+2.54/-1.56) × 10^(-10) erg/s/cm^2. Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-04-30T02:34:41 (UTC). The exposure time of the observation is around 3 ks. The on-ground analysis of the FXT data found an uncatalogued source at R.A. = 178.3355, DEC = -10.2146 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT light curve shows a raipd decay. The average FXT 0.5-10 keV spectra can be fitted with an absorbed power-law with a fixed Galactic hydrogen column density of 0.3× 10^21 cm^-2, and a photon index of 4.61 (+/-0.20). The derived average unabsorbed 0.5-10 keV flux is 1.27 (-0.16/+0.17) × 10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. We note that follow-up observations were carried out by Lipunov et al. (GCN 44428), Fortin et al. (GCN 44431) and Chácon et al. (GCN 44432), but no optical counterpart was detected in these observation. 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/44436. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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