EP260209a
GCN Circular 43700
Subject
EP260209a: COLIBRÍ optical upper limit
Date
2026-02-11T16:49:52Z (a month ago)
From
Jean-Luc Atteia at IRAP <jean-luc.atteia@irap.omp.eu>
Via
Web form
Jean-Luc Atteia (IRAP), Fredd Sánchez Álvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Camila Angulo (UNAM), 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), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the EP transient EP260209a (Zhang et al., GCN Circ. 43693) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-11 12:43 to 13:02 UTC ( 47.0 to 47.4 hours after the trigger) and obtained 960 seconds of simultaneous exposure in the r and z filters.
The data were reduced, coadded, calibrated and analyzed 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.
In the stacked image, we do not detect any new source at the FXT source position (Zhang et al., GCN Circ. 43693) down to the following 5-sigma limit:
r > 20.4,
z > 18.8.
These limits are compatible with those of LCO (Corcoran et al. GCN Circ. 43698)
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.
GCN Circular 43698
Subject
EP260209a: LCO optical upper limits
Date
2026-02-11T16:41:01Z (a month ago)
From
Gregory Corcoran at University College Dublin <gregory.corcoran@ucdconnect.ie>
Via
Web form
G. Corcoran (UCD) and J. A. Quirola-Vasquez (Radboud) report on behalf of a larger collaboration:
We observed the field of the fast X-ray transient EP260209a (Zhang et al., GCN 43693) using the LCO 1m telescope located at the McDonald Observatory (Texas, USA) equipped with the SINISTRO instrument. Our observations consisted of a sequence of 4x300 s exposures in the SDSS r-band starting on 2026-02-11 at 12:22:56 UT (~1.44 days after the WXT trigger).
We do not detect any sources within the EP/FXT uncertainty region (Zhang et al., GCN 43693). From the stacked image, we obtain the following 3-sigma upper limiting magnitude:
r > 22.5
This limit is in the AB system, calibrated using nearby stars from the Pan-STARRS catalog, and not corrected for Galactic extinction.
GCN Circular 43695
Subject
EP260209a: Global MASTER-Net observations report
Date
2026-02-11T12:45:25Z (a month 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-Tunka robotic telescope [1] located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the EP260209a ( EP Team et al., GCN 43693) errorbox 105 sec after notice time and 1 days 79337 sec after trigger time at 2026-02-11 11:46:23 UT, with upper limit up to 19.1 mag. Observations started at twilight. The observations began at zenith distance = 73 deg. The sun altitude is -14.9 deg.
The galactic latitude b = 61 deg., longitude l = 203 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3129906
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
165768 | 2026-02-11 11:46:23 | MASTER-Tunka | (10h 36m 50.32s , +28d 07m 55.2s) | C | 60 | 18.9 |
165768 | 2026-02-11 11:46:23 | MASTER-Tunka | (10h 37m 06.41s , +28d 01m 58.3s) | C | 60 | 19.1 |
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 43693
Subject
EP260209a: Einstein Probe detection of a fast X-ray transient
Date
2026-02-11T11:43:58Z (a month ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y.J. Zhang (THU), R. Shi (PMO), Z. H. Yang, Q. C. Zhao (IHEP), G. Y. Zhao (SYSU) and Z. X. Ling (NAOC) 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 EP260209a. The EP-WXT observation started at 2026-02-09T13:44:06 (UTC). The WXT position of the source is R.A. = 159.683 deg, DEC = 28.312 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). The light curve exhibits a flare in the first 50 seconds of the WXT observation, with a 0.5--4 keV flux of approximately 7.4 × 10^-10 erg s^-1 cm^-2. The delayed report of the transient is due to its relatively low detection significance.
We performed a follow-up observation with the Follow-up X-ray Telescope (FXT), starting at 2026-02-10T07:02:41 (UTC), about 17 hours after the detection. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 159.6834 deg, DEC = 28.3078 deg (J2000) with an uncertainty of 10 arcsec in radius (90% C.L. statistical and systematic). The uncatalogued X-ray source has a 0.5--10 keV flux of 1.1 x 10^-13 erg s^-1 cm^-2, with a powerlaw index of 1.3 and a fixed galactic NH value (1.6 x 10^20 cm^-2).
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).