GCN Circular 45892
EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
From: Chenxi Bao at Peking University
Issued: 2026-10-11 04:00 UTC
Type: X-ray Transient, Optical Transient
Chenxi Bao (PKU), Zhuokai Liu (PKU), Yacheng Kang (PKU), and Yuhan Yao (PKU) report on behalf of the Interestar Collaboration and the PKU HiTF (High-energy Transients Follow-up) group:
We observed the field of EP261006a (Lao et al., GCN 45826; T0 = 2026-10-06T17:49:57) following its discovery and tentative classification as a TDE candidate (Eyles-Ferris et al., GCN 45831; Jiang et al., GCN 45833). Our observations were performed using two 28cm optical telescope operated by the Interestar Collaboration, one located in Chengde, China, and the other in Castillejar, Spain. Multiple epochs of Luminance-band imaging were obtained on 2026 October 7 and 9.
In our stacked difference images, we clearly detect the optical counterpart at a position consistent with that of AT 2026aetp (Eyles-Ferris et al., GCN 45831; Jiang et al., GCN 45833; Wu et al. GCN 45852; Bochenek et al., GCN 45853; Chen et al. GCN 45854; Zhang et al., GCN 45877; Bochenek et al., GCN 45883; Kang et al., GCN 45885). Reference images for the subtraction were constructed from Pan-STARRS g- and r-band imaging. Preliminary photometry was calibrated against nearby Pan-STARRS field stars and is reported on an approximate AB magnitude scale, without correction for Galactic extinction.
The Luminance-band observation log is summarized below:
| Date | Start_UT | T_mid - T0 (days) | Site | Exposure (s) | Magnitude (AB) |
| :--------: | :------: | :---------------: | :---------: | :----------: | :------------: |
| 2026-10-07 | 13:29:53 | 0.84 | Chengde | 2400 | 18.82 +/- 0.08 |
| 2026-10-07 | 14:17:18 | 0.88 | Chengde | 2700 | 18.83 +/- 0.07 |
| 2026-10-07 | 17:24:09 | 1.00 | Chengde | 2700 | 18.79 +/- 0.06 |
| 2026-10-07 | 18:18:05 | 1.04 | Chengde | 3000 | 18.78 +/- 0.06 |
| 2026-10-07 | 19:24:18 | 1.09 | Chengde | 3000 | 18.74 +/- 0.07 |
| 2026-10-09 | 20:33:05 | 3.13 | Castillejar | 3000 | 18.59 +/- 0.06 |
| 2026-10-09 | 21:30:35 | 3.17 | Castillejar | 2700 | 18.48 +/- 0.06 |
| 2026-10-09 | 22:18:08 | 3.20 | Castillejar | 3000 | 18.54 +/- 0.06 |
Our measurements indicate that the optical counterpart remained at approximately 18.8 mag on October 7 and appeared brighter on October 9. Further analysis and follow-up observations are ongoing.
As part of the PKU HiTF group, the Interestar Collaboration contributes to the rapid follow-up of high-energy transients.
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.
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: Luminance-band optical follow-up with small-aperture telescopes
The whole thread (20 posts)
- EP261006a — X-ray Transient
- EP261006a / AT 2026aetp: Optical follow-up with the 1.3-m DFOT
- EP261006a : MeerKAT radio observations.
- EP261006a: 10 GHz VLA observations
- EP261006a / AT 2026aetp: Luminance-band optical follow-up with small-aperture telescopes
- EP261006a: Kilonova-Catcher optical follow-up and detection
- Updated explainer: what the latest reports add (AI-written)
- EP261006a / AT 2026aetp: Multiband optical follow-up with the PKU 60cm Telescope
- EP261006a: Liverpool Telescope optical follow-up
- Explainer: what this is and why it matters (AI-written)
- EP261006a: Xinglong 2.16m/BFOSC optical follow-up observations
- EP261006a: Optical follow-up observations with MATCH
- EP261006a / AT 2026aetp: VLT/X-shooter spectroscopic redshift z = 0.1853
- EP261006a: Swift/XRT detection of the fading X-ray counterpart
- EP261006a: Optical follow-up observations with Kinder
- EP261006a: Liverpool Telescope optical observations
- EP261006a: Early Optical Observations by WFST
- EP261006a: NOT spectroscopy of a blue continuum
- EP261006a: LT and NOT discovery of an optical counterpart
- EP261006a: SVOM/VT optical upper limits