X-ray transient detected by Einstein Probe with no optical counterpart identified

AI Summary

An X-ray transient event (EP261023a) was detected by the Einstein Probe's Wide-field X-ray Telescope (WXT) on Oct 23, 2026. Follow-up observations failed to identify an optical counterpart, establishing significant upper limits in various bands.

Measurements

Notices (1)

Einstein Probe WXT — GRB · Fri, 23 Oct 2026 04:03:19 GMT

GCN Circulars (5)

GCN-46027 — EP261023a · Sun, 25 Oct 2026 17:22:22 GMT
Astronomers observed the field of EP261023a in the near-infrared J band using the Palomar 1-m telescope equipped with the WINTER camera, but did not detect the optical counterpart, establishing a 5-sigma upper limit of J = 19.14 mag (AB). This non-detection is significant as it provides constraints on the properties of the transient event.

GCN-46023 — EP261023a · Sun, 25 Oct 2026 09:05:37 GMT
The SYSU 80cm infrared telescope observed the field of EP261023a, detected by the Einstein Probe, and did not find any new source within the optical afterglow localization, setting a 5-sigma upper limit of J = 19.1 mag. Observations by Mondy started approximately 9.8 hours after the trigger and yielded a 3-sigma upper limit of R = 22.2 mag.

GCN-46018 — EP261023a · Sat, 24 Oct 2026 09:07:49 GMT
The Einstein Probe fast X-ray transient EP261023a was observed with the 1.5-m AZT-33IK telescope at the Sayan Solar Observatory, but no optical counterpart was detected, with an upper limit magnitude of 22.2 in the R filter. This non-detection provides constraints on the optical brightness of the transient approximately 0.41 days after the initial trigger.

GCN-46015 — EP261023a · Fri, 23 Oct 2026 15:42:14 GMT
An optical source, potentially the counterpart of EP261023a, was detected within the error circle of the event using the Nordic Optical Telescope. The source has a magnitude of r = 22.71 and is consistent with an early-type galaxy, suggesting it may be the host galaxy.

GCN-46014 — EP261023a · Fri, 23 Oct 2026 14:56:22 GMT
The Einstein Probe mission detected an X-ray transient, EP261023a, on October 23, 2026, using the Wide-field X-ray Telescope (WXT). The transient was bright for approximately 64 seconds and was followed up by the Follow-up X-ray Telescope (FXT), which detected an uncatalogued X-ray source within the WXT error circle.