Einstein Probe detects bright X-ray transient with multi-wavelength counterpart at z=0.089

AI Summary

EP260806a is an X-ray transient detected by Einstein Probe WXT on 2026-08-06 at RA=12.278°, Dec=35.588° with a 0.5-4 keV flux of 1.65×10⁻¹⁰ erg/s/cm². The optical counterpart at z=0.089 shows blue colors consistent with an AGN outburst or tidal disruption event. Extensive multi-wavelength follow-up includes radio detections (VLA: 5.5 mJy at 10 GHz; ALMA: 50 mJy at 104.5 GHz) indicating a relativistic jetted transient, plus optical observations across multiple facilities confirming a brightening source with peak luminosity ~3.8×10⁴⁵ erg/s in X-rays.

Measurements

Notices (1)

Einstein Probe WXT — GRB · Thu, 06 Aug 2026 23:02:28 GMT

GCN Circulars (15)

GCN-45547 — EP260806a · Thu, 10 Sep 2026 14:49:26 GMT
Astronomers detected a bright radio source at the position of the Einstein Probe transient EP260806a using the VLA and ALMA telescopes, with flux densities of 5.5 mJy at 10 GHz and 50 mJy at 104.5 GHz. The source's luminosity and spectral characteristics suggest it may be a relativistic jetted transient, similar to gamma-ray bursts or tidal disruption events.

GCN-45541 — EP260806a · Thu, 10 Sep 2026 01:22:56 GMT
The NOEMA interferometer detected the afterglow of EP260806a in multiple frequency bands, approximately 4.9 days after the initial detection by the Einstein Probe, with a flux density of about 0.4 mJy. This observation provides valuable data for studying the transient event, which has been followed up by various researchers and institutions.

GCN-45396 — EP260806a · Tue, 18 Aug 2026 15:10:31 GMT
The X-ray transient EP260806a, detected by EP, was observed with the Zeiss-1000 and BTA 6-meter telescopes at SAO RAS over six epochs. The optical counterpart was clearly detected, and the photometry and light curve analysis suggest an AGN outburst, consistent with previous observations.

GCN-45390 — EP260806a · Mon, 17 Aug 2026 20:11:23 GMT
The SVOM/ECLAIRs telescope detected a transient event, EP260806a, starting at 2026-08-06T20:02:00 UTC, which was later confirmed by EP-WXT. The event was detected in two time windows, with the best detection having a signal-to-noise ratio of 6.7 in the 4-20 keV energy range.

GCN-45389 — EP260806a · Mon, 17 Aug 2026 10:35:31 GMT
The NUTTELA-TAO 0.7 m telescope at the Assy-Turgen Observatory detected the optical counterpart of EP260806a in both Sloan g’ and i’ bands, reporting magnitudes of 18.25 and 18.45 respectively. This detection is part of ongoing observations and follows multiple previous detections by other teams.

GCN-45385 — EP260806a · Sat, 15 Aug 2026 07:23:12 GMT
The Wide Field Survey Telescope (WFST) detected the optical counterpart of EP260806a, initially identified by the Einstein Probe, approximately 184.89 hours after the trigger. The optical counterpart was confirmed in the g-band with a magnitude of 18.312 ± 0.008 AB, and no other sources were detected within the error region.

GCN-45354 — EP260806a · Tue, 11 Aug 2026 10:04:26 GMT
The Maidanak Observatory in Uzbekistan detected an optical counterpart to the event EP260806a using the AZT-22 telescope, with a magnitude of 18.16 in the R-band. This detection was part of a collaborative effort involving multiple institutions and the GRANDMA telescope network, contributing to the multi-messenger astrophysics study of transients.

GCN-45312 — EP260806a · Fri, 07 Aug 2026 20:52:13 GMT
Astronomers detected an optical counterpart, ZTF26abmjjnm/AT 2026yeh, to the X-ray transient EP260806a using the Zwicky Transient Facility. The source was observed 12 hours after the initial detection and appeared blue with magnitudes g = 18.69 +/- 0.09 AB and r = 18.93 +/- 0.09 AB.

GCN-45306 — EP260806a · Fri, 07 Aug 2026 10:01:00 GMT
The COLIBRÍ telescope detected the optical counterpart of EP260806a with a preliminary magnitude of 19.44 in the z filter, confirming previous observations. The detection was made using the DDRAGO imager and involved a collaborative effort by researchers from multiple institutions.

GCN-45305 — EP260806a · Fri, 07 Aug 2026 09:57:42 GMT
The X-ray transient EP260806a was detected by the Einstein Probe (EP) mission and followed up by several ground-based telescopes. The source showed a declining flux during the follow-up observation, with an estimated peak luminosity of 3.8 × 10^45 erg s^-1 in the 0.5-10 keV energy band, and further observations are planned.

GCN-45304 — EP260806a · Fri, 07 Aug 2026 09:39:44 GMT
The SVOM/VT telescope observed the optical counterpart of EP260806a, a transient event detected by EP/WXT, and found a brightening of approximately 0.1 magnitude in both VT_B and VT_R bands over a period of 3.127 hours. The observation began 43.667 minutes after the initial trigger, and no uncatalogued sources were found within the error circle, but a bright cataloged galaxy was detected at the optical counterpart position.

GCN-45303 — EP260806a · Fri, 07 Aug 2026 09:33:18 GMT
The Liverpool Telescope detected an optical counterpart to the fast X-ray transient EP260806a with a blue color, consistent with an AGN outburst or a tidal disruption event. Observations were conducted using the IO:O instrument with SDSS r’ and z’ filters, revealing magnitudes of 19.22 and 19.53 respectively, and no other sources were detected within the error region.

GCN-45302 — EP260806a · Fri, 07 Aug 2026 08:25:50 GMT
Astronomers observed the optical counterpart of the event EP260806a using the Gran Telescopio Canarias (GTC) and detected a brightening of 0.27+/-0.04 mag in the r-band, consistent with the core of an underlying galaxy. The spectra revealed strong emission lines at a common redshift of z = 0.089, suggesting this is the redshift of the event, which could be indicative of an active galactic nucleus.

GCN-45300 — EP260806a · Fri, 07 Aug 2026 02:28:30 GMT
An optical counterpart to the event EP260806a, detected by EP, has been identified in a brightened galaxy with a redshift of ~0.136. The source, observed using the LCO 1m telescope at the Teide Observatory, has a magnitude of 19.32 in the SDSS-r filter and is considered a likely optical counterpart to the event.

GCN-45299 — EP260806a · Fri, 07 Aug 2026 00:18:42 GMT
The Einstein Probe (EP) mission detected an X-ray transient, designated EP260806a, on August 6, 2026. The event was initially detected by the Wide-field X-ray Telescope (WXT) and subsequently confirmed by the Follow-up X-ray Telescope (FXT).