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 / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
GCN Circulars —

GCN Circular 45966
EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
From: unknown
Issued: 2026-10-16 18:38 UTC
Type: X-ray Transient, Optical Transient

Pankaj Pawar, Sarvesh Yadav, Dhruv Jain, Anshika Gupta, Debalina kar and Kuntal Misra (ARIES, Nainital, India) report:

We observed the field of EP261006a (Lao et al., GCN 45826) and its optical
counterpart AT 2026aetp (Eyles-Ferris et al., GCN 45831) with the 1.3-m
Devasthal Fast Optical Telescope (DFOT), India, on 2026 October 15.
Observations started at 18:03:52 UT. We obtained six 300-s exposures in each
of the V, R and I filters.

We detect the optical counterpart in the stacked difference images, using
archival Pan-STARRS and Legacy Survey images as references. Our preliminary
PSF photometry is:

Mid-time (UT) Tmid-T0 (d) Filter Exposure (s) Mag (Vega)
2026-10-15 18:19:04 9.02022 R 6 x 300 18.68 +/- 0.13
2026-10-15 18:50:59 9.04239 I 6 x 300 18.96 +/- 0.18
2026-10-15 19:33:34 9.07196 V 6 x 300 18.53 +/- 0.15

T0 is 2026-10-06 17:49:57 UT (Lao et al., GCN 45826). Photometry was
calibrated against nearby Pan-STARRS stars transformed to approximate Johnson
V and Cousins R/I magnitudes on the Vega system. The uncertainties include
estimated subtraction systematics. Magnitudes are not corrected for Galactic
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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