Transient Alerts — HabitableZone

Transient Alerts » in reply to EP261006a — X-ray Transient

In plain words Notable

On 6 October 2026 the Einstein Probe, a space X-ray telescope, spotted a sudden flash of X-rays at the position of a galaxy, with a measured redshift of 0.1853 (very roughly 2-3 billion light-years away). Optical telescopes then found a bright, blue, new light source right at the galaxy's centre that was not there two days earlier and has brightened to about 18th magnitude over several days. Its blue colour and central location fit a tidal disruption event, where a black hole tears apart a passing star, but the spectra show no clear features to confirm this, and a fast-fading exploding star remains possible. The X-rays faded by about a factor of 300 within a day, while the visible light kept rising, so the two may not come from the same process. Radio telescopes (VLA and MeerKAT) detected nothing.

How unusual is it? A measured distance, an optical counterpart at the galaxy's centre and a rising blue light curve make this a well-characterised fast X-ray transient, with a likely tidal disruption event, which is more than the typical alert. It is not exceptional, since such events are being found regularly, and the classification is still unconfirmed; clear emission lines or radio emission would settle the nature, and a different type of explosion would change the picture.

Written by an AI model (claude-sonnet-5-5) from the official reports in this thread, and rewritten as new reports arrived (version 7); last updated . It may contain mistakes: the reports themselves are the authority.

EP261006a: Liverpool Telescope optical observations
GCN Circulars —

GCN Circular 45853
EP261006a: Liverpool Telescope optical observations
From: Daniel Perley at Liverpool JMU
Issued: 2026-10-08 09:08 UTC
Type: X-ray Transient, Optical Transient

A. Bochenek and D. A. Perley (LJMU) report:

We observed the field of EP261006a (Lao et al., GCN 45826) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 3x100s exposures in SDSS g filter and 4x100s in SDSS r, starting at 2026-10-07 21:33:20 UT, approximately 27.7 hours after trigger.

Image subtraction is performed against reference imaging from the Pan-STARRS survey. We detect a source in the subtracted images at the counterpart position reported by Eyles-Ferris et al. (GCN 45831) and Jiang et al. (GCN 45833), inside the galaxy Gaia DR3 2587044864659595392. The source remains blue, and has brightened significantly since the observations of Eyles-Ferris et al. (GCN 45831) and Wu et al. (GCN 45852).

| MJD (mid) | T_mid-T_0 | Filter | Mag. (AB) |
| ------------ | ---------- | ------ | ------------ |
| 61320.90009 | 27.8 h | sdss-g | 18.53 ± 0.07 |
| 61320.90500 | 27.9 h | sdss-r | 18.73 ± 0.07 |

The observations were taken in very poor seeing (3-5 arcsec), and the values above should be treated as preliminary. Further observations are scheduled. The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.

Filter: only the top 10% of the past year's X-ray transients are posted, ranked by the number of GCN Circulars written about them (now ≥ 11). Thresholds are recalculated monthly. Only events first reported within the past 7 days can start a thread.
Relayed automatically from NASA's General Coordinates Network.

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