EP260429a
GCN Circular 44437
Subject
EP260429a: Global MASTER-Net observations report
Date
2026-05-01T10:09:31Z (2 days ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
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
GCN Circular 44433
Subject
EP260429a: LCO optical upper limits
Date
2026-04-30T11:20:40Z (3 days ago)
From
Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk>
Via
Web form
R. A. J. Eyles-Ferris (Leicester), J. A. Chácon (PUC), F. E. Bauer (SSI and UTA), J. Quirola-Vasquez (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. J. Levan (Radboud & Warwick), P. G. Jonker (Radboud), report on behalf of a larger collaboration:
We observed the field of the fast X-ray transient EP26029a (Wang et al., GCN 44426) using LCO 1m telescopes located at the Cerro Tololo Inter-American Observatory (Chile) equipped with the SINISTRO instrument. A series of 6x300 s exposures were taken in each of the SDSS-r and SDSS-z filters, starting at 2026-04-30 08:23:54 UT (~18.0 hr after the trigger).
No new source is detected within or at the border of the EP/WXT uncertainty region (Wang et al., GCN 44426) nor do we identify any significant residuals in subtractions using PanSTARRS DR1 templates. From the stacked images, we obtain the following 3-sigma upper limits:
r > 22.5
z > 20.9
These upper limits are in AB magnitudes, calibrated using nearby stars from the Pan-STARRS catalogue, and are not corrected for Galactic extinction.
GCN Circular 44426
Subject
EP260429a: EP-WXT detection of a fast X-ray transient
Date
2026-04-30T03:05:55Z (3 days ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. Wang (PMO), Y. L. Wang (NAO, CAS; ICE, CSIC), C.C Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team:
We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260429a. The WXT light curve shows a single pulse with a duration of about 250 s. The transient started at 2026-04-29 14:41:11 UTC. The WXT position of the source is R.A. = 240.629 deg, DEC = -9.588 deg (J2000) with an uncertainty of 1.9 arcmin in radius (90% C.L. statistical and systematic).
The average WXT 0.5 - 4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 4.31 (-0.08/+0.09) x 10^21 cm^-2 and a photon index of 1.44 (-0.04/+0.04). The derived average unabsorbed 0.5-4 keV flux is 3.96 (-0.32/+0.37) x 10^-9 erg/s/cm^2.
Follow-up observation with the Follow-up X-ray Telescope on board EP has been scheduled. Further information will be updated when the telemetry data is received.
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).