Fast X-ray transient EP260227a detected at z=2.714 with rapid optical fading

AI Summary

Einstein Probe WXT detected a bright X-ray transient (01709258681) on 2026-02-27 lasting ~250 seconds with 0.5-4 keV flux of 4.1×10⁻¹⁰ erg/s/cm². Rapid multi-wavelength follow-up identified an optical counterpart that faded from r≈20.2 mag to r≈24.8 mag over 4 days. Spectroscopic observations with GTC measured redshift z=2.714, revealing absorption features consistent with a damped Lyman-alpha system. The event represents a rare high-redshift fast X-ray transient with well-characterized optical evolution.

Notices (1)

Einstein Probe WXT — GRB · Fri, 27 Feb 2026 20:12:29 GMT

GCN Circulars (18)

GCN-43905 — EP260227a · Tue, 03 Mar 2026 10:58:44 GMT
Astronomers led by R. A. J. Eyles-Ferris (University of Leicester) and J. Quirola-Vasquez (Radboud) report the detection of optical emission from the fast X-ray transient EP260227a using the Gemini-South telescope. The team obtained 12 exposures in the r band and measured a preliminary magnitude of r = 24.80 +/- 0.33. The significance of this detection is that it provides further evidence for the optical counterpart of this transient event, which was first detected in X-rays. The nature of the emission, whether it is continued transient activity or the underlying host galaxy, remains unclear.

GCN-43894 — EP260227a · Mon, 02 Mar 2026 13:09:06 GMT
The IKI-GRB-FuN team observed the optical counterpart of the fast X-ray transient EP260227a using the AZT-33IK 1.5m telescope at Mondy observatory. The team reported that the optical counterpart was barely detected in a stacked frame, with a preliminary magnitude of 21.8 (3σ) and an exposure time of 40x90 seconds in the R band.

GCN-43891 — EP260227a · Sun, 01 Mar 2026 14:58:50 GMT
Astronomers at Yunnan University using the Mephisto telescope detected a new optical source at the position of a previously reported transient event. The preliminary magnitudes in u/g/i bands were measured, with the brightest being in the g-band at 20.58 mag. Mephisto is a unique 1.6-m wide-field multi-channel telescope capable of simultaneous imaging in three optical bands.

GCN-43888 — EP260227a · Sun, 01 Mar 2026 10:25:41 GMT
Astronomers led by R. A. J. Eyles-Ferris at the University of Leicester observed the optical counterpart of a fast X-ray transient, EP260227a, using the LCO 1m telescope at Cerro Tololo Inter-American Observatory. They detected the counterpart and measured an AB magnitude of r = 22.82 ± 0.28, finding no significant evolution since previous observations. The team includes collaborators from various institutions.

GCN-43887 — EP260227a · Sun, 01 Mar 2026 09:51:54 GMT
The Space Variable Objects Monitor (SVOM) team reported a Target of Opportunity observation of transient event EP260227a, detected by EP/WXT. SVOM observed the event in the VT_B and VT_R bands 11.14 hours after the trigger, and detected the optical counterpart with magnitudes of 21.9+-0.1 in VT_B and 21.3+-0.1 in VT_R. The SVOM is a China-France joint mission dedicated to observing gamma-ray bursts and other transient phenomena.

GCN-43884 — EP260227A · Sun, 01 Mar 2026 07:52:34 GMT
Astronomers at ARIES using the 3.6m Devasthal Optical Telescope (DOT) detected an optical afterglow of a cosmic event (EP260227A) approximately 25 hours after its initial detection by the Einstein Probe WXT. The preliminary magnitude measurement is 22.92 +/- 0.06 in the R filter.

GCN-43881 — EP260227a · Sat, 28 Feb 2026 20:17:24 GMT
A team of astronomers led by Julius Gassert at Ludwig-Maximilians-Universität München and Malte Busmann observed the optical counterpart of a transient event, EP 20260227a, using the Three Channel Imager at the Fraunhofer Telescope at Wendelstein Observatory. They detected the counterpart in the r, i, and J bands and measured an r-band magnitude of 21.69 ± 0.10 AB mag, which is calibrated against the PS1 catalog but not corrected for Galactic extinction.

GCN-43880 — EP260227a · Sat, 28 Feb 2026 20:05:03 GMT
The Liverpool Telescope at Liverpool John Moores University observed the optical counterpart of a transient event, EP260227a, using its IO:O optical camera. The team obtained magnitudes in the r, i, and z filters and reported detections in all filters at the previously reported position. The magnitudes show a slower fading trend compared to previous observations. The team used nearby PanSTARRS secondary standards for photometry without extinction correction.

GCN-43879 — EP260227a · Sat, 28 Feb 2026 17:33:05 GMT
On February 28, 2023, a team of astronomers led by R. Strausbaugh from Eastern Illinois University and A. Cucchiara from NASA observed the EP260227a field using the LCOGT 1-meter Sinistro instrument at Cerro Tololo Interamerican Observatory. They detected an uncatalogued source in both the r and i bands, with preliminary magnitudes of r = 20.78 ± 0.58 and i = 21.47 ± 0.52. These measurements are consistent with other recent optical detections of this transient event.

GCN-43877 — EP260227a · Sat, 28 Feb 2026 12:41:42 GMT
Astronomers led by R. A. J. Eyles-Ferris at the University of Leicester observed the fast X-ray transient EP260227a using the 2.4m Thai National Telescope and the ULTRASPEC instrument. They detected the optical counterpart of the transient, which had a magnitude of 23.57 in the KG5 filter. The faint magnitude is likely due to the peak response of the filter in the blue and the red color of the source.

GCN-43876 — EP260227a · Sat, 28 Feb 2026 12:12:32 GMT
Astronomers using the Gran Telescopio Canarias (GTC) equipped with the OSIRIS+ spectrograph have measured a redshift of 2.714 for the optical counterpart of EP260227a, detected in previous alerts. The observation consisted of four exposures of 900 seconds each, revealing faint traces of the spectrum and several emission lines.

GCN-43875 — EP260227a · Sat, 28 Feb 2026 10:29:52 GMT
Astronomers using the 2m Liverpool Telescope on La Palma observed the optical counterpart of a newly discovered X-ray source, EP260227a, in the g', r', i', and z' bands. The team, led by R. A. J. Eyles-Ferris and N. R. Tanvir from the University of Leicester, measured the source's magnitudes and found that it had not significantly faded since previous observations. The detected magnitudes are: g' > 22.28 (3-sigma), i' = 21.12 ± 0.08, r' = 21.61 ± 0.22, and z' = 20.74 ± 0.11.

GCN-43874 — EP260227a · Sat, 28 Feb 2026 09:50:46 GMT
A group of astronomers led by Nikos Mandarakas from LAM, in collaboration with UNAM, IRAP, CPPM, NYUAD, IJCLAB, and other institutions, observed the optical counterpart of the recently discovered transient EP260227a using the DDRAGO imager on the COLIBRÍ telescope. They obtained 44 minutes of simultaneous exposure in the r and z filters and detected the transient at preliminary magnitudes of r = 21.4644 ± 0.0680 and z = 20.8905 ± 0.0745.

GCN-43873 — EP260227a · Sat, 28 Feb 2026 06:51:11 GMT
Astronomers using the 2.56-m Nordic Optical Telescope (NOT) reported non-optical observations of the transient EP260227a, which was previously detected in optical wavelengths. They obtained magnitudes of 21.40 ± 0.20 in g', 21.50 ± 0.20 in r', and 21.37 ± 0.12 in i' bands, 6.14 hours after the trigger.

GCN-43870 — EP260227a · Sat, 28 Feb 2026 04:45:41 GMT
The MASTER-Net network of robotic telescopes, including the MASTER-SAAO telescope in South Africa, have begun observing the astronomical object EP260227a following a trigger from the Global MASTER-Net system. The observations are being carried out with various exposure times and filters, with the latest upper limit reported at 19.8 mag. The object's coordinates are given by the galactic latitude b = 41 deg., longitude l = 345 deg.

GCN-43869 — EP260227a · Sat, 28 Feb 2026 04:28:28 GMT
Astronomical alert: EP260227a: Einstein Probe detection of an X-ray transient and refined analysis

GCN-43868 — EP260227a · Sat, 28 Feb 2026 02:12:37 GMT
Astronomers at NAOC, TAU, and U of Arizona observed a rapidly fading source using the Las Cumbres 1m telescope at Siding Spring Observatory following an Einstein Probe WXT trigger. The source, located at the position reported by Eyles-Ferris et al., had preliminary magnitudes of 20.28 ± 0.09 and 21.08 ± 0.10 at two different epochs.

GCN-43867 — EP260227a · Fri, 27 Feb 2026 23:33:12 GMT
Astronomers using the Sinistro instrument on the 1-m telescope in South Africa's LCO network have identified a new optical counterpart for the EP/WXT trigger 0172958681 (EP260227a), located at RA = 14:52:19.94, Dec = -11:24:23.9, with a magnitude of 20.18. This discovery was made approximately 2.5 hours after the trigger and suggests a possible afterglow.