EP260214a
GCN Circular 43862
Subject
EP260214a: VLT/FORS2 optical observations
Date
2026-02-27T09:53:25Z (7 months ago)
From
N. Passaleva at Sapienza University of Rome <niccolo.passaleva@uniroma1.it>
Via
Web form
N. Passaleva, H. Waseem, Yu-Han Yang, and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team:
We observed the field of EP260214a (Li et al., GCN 43742) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 11.3 days after the EP/WXT trigger and were carried out at an average airmass ~1.3 and with an average seeing ~0.45 arcsec in the R filter.
At the position of the candidate radio counterpart reported by Ricci et al. (GCN 43845) we detect a faint source (r~26 AB mag). Assuming our observations are dominated by the host galaxy light, we compute a chance alignment of Pcc~1%.
We thank the staff at the VLT for the rapid execution of these observations.
GCN Circular 43845
Subject
EP260214a: VLA 6 GHz detection
Date
2026-02-26T14:15:11Z (7 months ago)
From
Roberto Ricci at INAF-IRA <ricci@ira.inaf.it>
Via
Web form
R. Ricci, M. Yadav, Y.-H. Yang, N. Passaleva and E. Troja (U Rome) report:
We observed the Einstein Probe event EP260214a detected by EP/WXT (A. Li et al. GCN 43742) with Very Large Array in C-band at the centre frequency of 6 GHz with a bandwidth of 4 GHz on Feb 21st 2026, 6.6 days after the trigger.
Within the EP/FXT error circle (A. Li et al., GCN 43751) we detect a possible radio counterpart at RA, Dec (J2000) = 13:24:55.401, -29:02:32.97 with a flux density of about 60 uJy.
No source is visible at this position in our deep VLT/HAWKI image (N. Passaleva et al. GCN 43756). However, we note that the candidate counterpart lies 8.8” away from a bright galaxy (r=19.62 AB mag), corresponding to a chance alignment of Pcc~4% (Bloom et al. 2002). Assuming a photometric redshift of z=0.18±0.15 (PRLS, Zhou et al. 2021), this corresponds to a projected physical offset of 27 (+15, -22) kpc.
Further observations to assess the variability of the candidate radio counterpart are planned.
We thank the VLA staff for executing the observations
GCN Circular 43761
Subject
EP260214a: Optical upper limits with Kinder observations
Date
2026-02-16T10:22:14Z (7 months ago)
From
Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941@gmail.com>
Via
Web form
A. Aryan, C.-S. Lin, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, M.-H. Lee, C.-H. Lai, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz, and M. Huber (both IfA, Hawaii) report:
We observed the field of the fast X-ray transient EP260214a (Li et al., GCN 43742 & GCN 43751) using the 40cm SLT at the Lulin observatory, as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The FXT was found to be coincident with GRB 260214A (Ravasio et al., GCN 43759). The first SLT epoch of observations in r-band started at 20:46 UTC on 14th of February 2026 (MJD 61085.865), 0.13 hr after the EP-WXT trigger.
We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We used the Python-based AutoPhOT package (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. Either in the stacked frame or in the difference image, we do not detect any new or uncataloged sources within the 10" refined EP-FXT localization circle (Li et al. GCN 43751).
Moreover, we used AutoPhOT to perform PSF photometry. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows:
Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass
SLT | r | 61085.865 | 0.13 | 300 * 6 | >20.6 | 2".62 | 1.79
The non-detection in our observations is consistent with those reported by Lipunov et al. (GCN 43743), Li et al. (GCN 43746), Watson et al. (GCN 43753), and He et al. (GCN 43754).
The presented magnitude is calibrated using the field stars from the Pan-Starrs catalog and is not corrected for the expected Galactic foreground extinction of A_r = 0.16 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission are presented in Aryan et al. 2025, ApJS, 281, 20, doi:10.3847/1538-4365/adfc69.
GCN Circular 43759
Subject
EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
Date
2026-02-15T20:20:37Z (7 months ago)
From
mariaedvige.ravasio@ru.nl
Via
Web form
M. E. Ravasio (Radboud Univ.), P.G. Jonker (Radboud Univ.)
and
E. Burns (LSU), R. Hamburg (USRA)
report on behalf of the Fermi-GBM Team:
Fermi-GBM had full spatial and temporal coverage of the transient EP260214a detected by EP-WXT (Li et al., GCN 43742, Li et al., GCN 43751). There was no Fermi-GBM onboard trigger around the EP refined starting time T0=2026-02-14T20:37:00 (UTC).
The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from the EP T0. A weak transient signal was found most significantly at ~T0+35 s on a 16 s timescale, with a false alarm rate of 2.27e-04 Hz. The localisation is consistent with the EP one, with a spatial association probability of 87.4%. Among the three spectral templates tested, the transient was best-fit with a "soft" spectrum (i.e., a Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB.
[1] Goldstein et al. 2019 arXiv:1903.12597
GCN Circular 43756
Subject
EP260214a: VLT near-infrared observation
Date
2026-02-15T18:04:57Z (7 months ago)
Edited On
2026-02-17T14:37:09Z (7 months ago)
From
N. Passaleva at Sapienza University of Rome <niccolo.passaleva@uniroma1.it>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of N. Passaleva at Sapienza University of Rome <niccolo.passaleva@uniroma1.it>
Via
Web form
Niccolò Passaleva, Massine El Kabir, Narges Shahamat, Eleonora Troja (U Rome) on behalf of the ERC BHianca team:
We observed the field of EP260214a (Li et al., GCN 43742) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations began at ~11.9 hr after the EP/WXT trigger and were carried out at an average airmass of about 1.0 in the J filter.
Several extended sources are visible close to or within the EP/FXT error region (Li et al., GCN 43751), however no uncatalogued source is clearly identified in our observations down to a 3 sigma limiting magnitude J~25 AB mag calibrated using nearby stars in the 2MASS Catalogue (Skrutskie et al. 2006) and not corrected for Galactic extinction.
We thank the staff at the VLT, for the rapid execution of these observations.
GCN Circular 43754
Subject
EP260214a: NOT optical upper limits
Date
2026-02-15T15:07:18Z (7 months ago)
From
L. B. He at NAOC <helb@bao.ac.cn>
Via
Web form
L.B. He (NAOC), S.Y. Fu (HUST), J. An, X. Liu, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), K. Valeckas (NOT) report on behalf of a large collaboration:
We observed the field of EP260214a (Li et al., GCN 43742) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 03:39:29.978 UT on 2026-02-15, i.e., 7.02 hrs after the EP trigger, and we obtained 3x300 s frames in the Sloan r-band and 5 x 200 s frames in the Sloan z- band.
No new optical source is detected within the EP/FXT error circle (Li et al., GCN 43751), down to 5-sigma upper limits of r ~ 23.1 and z ~ 21.8, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction.
These upper limits are consistent with the ones previously reported (Li et al., GCN 43746; Watson et al. GCN 43753).
GCN Circular 43753
Subject
EP260214a: COLIBRÍ optical upper limits
Date
2026-02-15T14:43:58Z (7 months ago)
Edited On
2026-02-16T15:24:03Z (7 months ago)
From
Rosa L. Becerra at Instituto de Astronomía, UNAM <rbecerra@astro.unam.mx>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Alan Watson at UNAM <alan@astro.unam.mx>
Via
Web form
Damien Dornic (CPPM), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), 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), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of EP260214a (Li et al., GCN Circ. 43742) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-15 10:20 to 11:32 UTC (from 13.70 to 14.92 hours after the trigger) and obtained 53 minutes of exposure, in r and z filters.
The data were reduced, 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.
In the stacked images, we do not detect any new source at the refined FXT position (Li et al., GCN Circ. 43751) down to the following 5-sigma limits:
r > 23.1
z > 21.7
These upper limits are consistent with the ones reported by SVOM/VT (Li et al. GCN Circ. 43746).
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 43751
Subject
EP260214a: refined analysis of the EP-FXT observation
Date
2026-02-15T13:22:15Z (7 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
A. Li (BNU), J. Yang (ZZU), Y. H. Jiang (NJU), Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team:
The fast X-ray transient EP260214a triggered the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Li et al., GCN 43742). It was followed by Global MASTER-Net (Lipunov et al., GCN 43743) and SVOM-VT (Li et al., GCN 43746). The refined analysis of the WXT data shows that the event started at T0=2026-02-14T20:37:00 (UTC), and lasted for approximately 60 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 4.6×10^20 cm^-2 and a photon index of 0.8 (-0.6/+0.7). The derived average unabsorbed 0.5-4 keV flux is 9.7 (-0.3/+0.4) × 10^(-11) erg/s/cm^2.
The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2026-02-14T20:39:31 (UTC), 2.5 minutes after T0. The effective exposure time of the observation is around 3.3 ks. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 201.2305, DEC = -29.0431 (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 fixed Galactic hydrogen column density of 1.6 × 10^20 cm^-2, and a photon index of 2.3 (-0.3/+0.3). The derived average unabsorbed 0.5-10 keV flux is 1.4 (-0.1/+0.2) ×10^(-11) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters.
Further FXT follow-up observations have been arranged.
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).
GCN Circular 43746
Subject
EP260214a: SVOM/VT optical upper limits
Date
2026-02-15T06:31:32Z (7 months ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, 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) report on behalf of the SVOM/VT team.
SVOM/VT performed a Target of Opportunity observation of EP260214a detected by Einstein Probe (Li et al., GCN 43742). The observation started on 2026-02-14T23:12:55 UTC, 2.58 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
No uncatalogued sources were detected in stacked images within the error box of EP-FXT (Li et al., GCN 43742). The 3 sigma limit magnitudes are derived as follows:
Mid time | Band | Exposure Time | 3 sigma limit magnitude
3.60 hours VT_B 56*50 sec > 23.6 mag
3.60 hours VT_R 50*50 sec > 23.3 mag
Our photometry was in AB magnitude and was not corrected for Galactic extinction.
The nondetection is consistent with the result from MASTER (Lipunov et al., GCN 43743).
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.
GCN Circular 43743
Subject
EP260214a: Global MASTER-Net observations report
Date
2026-02-15T03:18:24Z (7 months 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP260214a ( EP Team et al., GCN 43742) errorbox 268 sec after notice time and 21982 sec after trigger time at 2026-02-15 02:44:26 UT, with upper limit up to 17.3 mag. Observations started at twilight. The observations began at zenith distance = 76 deg. The sun altitude is -16.0 deg.
The galactic latitude b = 33 deg., longitude l = 312 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3136874
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
22012 | 2026-02-15 02:44:26 | MASTER-Kislovodsk | (13h 24m 58.40s , -28d 29m 17.5s) | C | 60 | 17.3 |
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 43742
Subject
EP260214a: Einstein Probe detection of an X-ray transient
Date
2026-02-15T02:39:30Z (7 months ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
A. Li (BNU), J. Yang (ZZU), Y. H. Jiang (NJU) and Y. Liu (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 EP260214a. The transient triggered EP-WXT (ID: 01709258386) at 2026-02-14T20:38:04 (UTC). The WXT position of the source is R.A. = 201.250 deg, DEC = -29.040 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. = 201.2326 deg, DEC = -29.0457 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).