EP261111a
GCN Circular 46230
Subject
EP261111a: Global MASTER-Net observations report
Date
2026-11-11T21:09:30Z (14 minutes ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Via
email
D.Buckley (SAAO),
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 (Lomonosov MSU)
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity)
A.Sosnovskij (Lomonosov MSU)
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory)
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
R.Rebolo (The Instituto de Astrofisica de Canarias)
O.Gress, N.Budnev(ISU)
M. Segura, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA)
MASTER-SAAO robotic telescope [1] located in South Africa (South African Astronomical Observatory) was pointed to the EP261111a ( EP Team at NAOC/CAS <ep_ta@bao.ac.cn> et al., GCN 46226) errorbox 25131 sec after notice time and 25446 sec after trigger time at 2026-11-11 20:29:16 UT, with upper limit up to 17.8 mag. The observations began at zenith distance = 79 deg. The sun altitude is -33.6 deg.
The galactic latitude b = -13 deg., longitude l = 145 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3532562
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
25477 | 2026-11-11 20:29:16 | MASTER-SAAO | (02h 50m 17.51s , +44d 06m 21.7s) | C | 60 | 17.6 |
25477 | 2026-11-11 20:29:16 | MASTER-SAAO | (02h 47m 56.22s , +44d 22m 23.8s) | C | 60 | 17.2 |
25571 | 2026-11-11 20:30:50 | MASTER-SAAO | (02h 50m 17.70s , +44d 04m 58.3s) | C | 60 | 17.7 |
25571 | 2026-11-11 20:30:50 | MASTER-SAAO | (02h 47m 56.63s , +44d 21m 02.2s) | C | 60 | 17.1 |
25665 | 2026-11-11 20:32:24 | MASTER-SAAO | (02h 50m 20.39s , +44d 06m 06.3s) | C | 60 | 17.6 |
25665 | 2026-11-11 20:32:24 | MASTER-SAAO | (02h 47m 59.41s , +44d 22m 10.9s) | C | 60 | 17.1 |
25758 | 2026-11-11 20:33:57 | MASTER-SAAO | (02h 50m 15.64s , +44d 05m 36.6s) | C | 60 | 17.8 |
25758 | 2026-11-11 20:33:57 | MASTER-SAAO | (02h 47m 54.73s , +44d 21m 42.2s) | C | 60 | 17.2 |
25850 | 2026-11-11 20:35:30 | MASTER-SAAO | (02h 50m 15.34s , +44d 06m 39.1s) | C | 60 | 17.7 |
25850 | 2026-11-11 20:35:30 | MASTER-SAAO | (02h 47m 54.41s , +44d 22m 45.1s) | C | 60 | 17.1 |
25944 | 2026-11-11 20:37:04 | MASTER-SAAO | (02h 50m 20.97s , +44d 05m 41.0s) | C | 60 | 17.7 |
25944 | 2026-11-11 20:37:04 | MASTER-SAAO | (02h 48m 00.22s , +44d 21m 47.7s) | C | 60 | 17.1 |
26037 | 2026-11-11 20:38:37 | MASTER-SAAO | (02h 50m 15.43s , +44d 04m 42.8s) | C | 60 | 17.7 |
26037 | 2026-11-11 20:38:37 | MASTER-SAAO | (02h 47m 54.78s , +44d 20m 49.9s) | C | 60 | 17.0 |
26130 | 2026-11-11 20:40:10 | MASTER-SAAO | (02h 50m 22.09s , +44d 04m 57.4s) | C | 60 | 17.8 |
26130 | 2026-11-11 20:40:10 | MASTER-SAAO | (02h 48m 01.41s , +44d 21m 05.0s) | C | 60 | 17.0 |
26224 | 2026-11-11 20:41:43 | MASTER-SAAO | (02h 50m 19.54s , +44d 06m 25.2s) | C | 60 | 17.7 |
26224 | 2026-11-11 20:41:43 | MASTER-SAAO | (02h 47m 58.82s , +44d 22m 33.1s) | C | 60 | 17.1 |
26316 | 2026-11-11 20:43:16 | MASTER-SAAO | (02h 50m 19.87s , +44d 05m 17.1s) | C | 60 | 17.7 |
26316 | 2026-11-11 20:43:16 | MASTER-SAAO | (02h 47m 59.19s , +44d 21m 25.6s) | C | 60 | 16.9 |
26410 | 2026-11-11 20:44:49 | MASTER-SAAO | (02h 50m 23.15s , +44d 06m 29.1s) | C | 60 | 17.7 |
26410 | 2026-11-11 20:44:49 | MASTER-SAAO | (02h 48m 02.51s , +44d 22m 37.8s) | C | 60 | 17.0 |
26503 | 2026-11-11 20:46:23 | MASTER-SAAO | (02h 50m 16.81s , +44d 05m 52.1s) | C | 60 | 17.7 |
26503 | 2026-11-11 20:46:23 | MASTER-SAAO | (02h 47m 56.21s , +44d 22m 01.3s) | C | 60 | 16.9 |
26596 | 2026-11-11 20:47:56 | MASTER-SAAO | (02h 50m 17.38s , +44d 06m 54.2s) | C | 60 | 17.7 |
26596 | 2026-11-11 20:47:56 | MASTER-SAAO | (02h 47m 56.82s , +44d 23m 03.8s) | C | 60 | 16.9 |
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 46227
Subject
EP261111a: Xinglong optical upper limit
Date
2026-11-11T15:54:58Z (5 hours ago)
From
Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong@nao.cas.cn>
Via
Web form
Junjie-Jin (NAOC), Qi-Zhao (NAOC), Dong-Xu (NAOC), Yue-Sun (NAOC), Haiyang-Mu (NAOC), Yu-Zhang (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration:
The Wide-field X-ray Telescope on Einstein Probe detected the X-ray transient EP261111a (Huang et al., GCN 46226).
We performed optical observations of the field of EP261111a at Xinglong Observatory. Our measurements are summarized below.
Inspection of the stacked science images and the archival-image comparison revealed no candidate optical counterpart within the EP/WXT localization region (3 arcmin radius). The representative 5-sigma point-source limiting magnitudes are listed below.
Time offsets are measured from the EP/WXT trigger at 2026-11-11T13:25:10Z (GCN 46226).
Mid-time (UTC) | Hours after trigger | Exposure (s) | Filter | 5-sigma limiting magnitude | System | Telescope 2026-11-11T13:48:38.264 | 0.391 | 6 x 300 | g | > 20.955 | PS1-AB-calibrated | Tsinghua-NAOC 0.8-m telescope (TNT)
The tabulated times are exposure-weighted mid-times in UTC. The representative depths were estimated from the background noise in the observed stacked images.
Photometry was calibrated using field stars from the BEST catalog (Xiao et al. 2026) on the PS1 photometric system.
References: GCN 46226 · EP261111a: Einstein Probe detection of an X-ray transient — https://gcn.nasa.gov/circulars/46226
GCN Circular 46226
Subject
EP261111a: Einstein Probe detection of an X-ray transient
Date
2026-11-11T14:03:15Z (7 hours ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
G. L. Huang, Z. X. Li (IHEP, CAS), Y. J. Zhang (THU), W. D. Zhang (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 EP261111a. The transient triggered EP-WXT (ID: 01709322401) at 2026-11-11T13:25:10 (UTC). The WXT position of the source is R.A. = 43.118 deg, DEC = 44.444 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 automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 43.1202 deg, DEC = 44.4365 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic).
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).