TITLE:   GCN CIRCULAR
NUMBER:  38337
SUBJECT: EP241126a: TRT optical counterpart detection
DATE:    24/11/27 08:39:43 GMT
FROM:    Dong Xu at NAOC/CAS <dxu@nao.cas.cn>

S.Y. Fu, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang, D. Xu (NAOC) report on behalf of a large collaboration:

We observed the field of EP241126a detected by Einstein Probe (EP, Hu et al., GCN 38335), using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 02:29:48 UT on 2024-11-27, i.e., 6.84 hr after the EP trigger, and 10 x 300 s frames were obtained in the R-band.

An uncatalogued optical source is detected in the stacked frame within the EP/FXT error circle (Hu et al., GCN 38335) and localized at coordinates

R.A. (J2000) = 02:14:57.96
Dec. (J2000) = +11:42:04.76

with an uncertainty of ~ 0.8 arcsec. The source has R ~ 22.0 mag at a median time of 7.59 hr after the EP trigger, calibrated with PanSTARRS and not corrected for Galactic extinction. In the Legacy Survey there is no source at the above position, down to limiting magnitude r ~ 24.0.

We thus conclude that the source is the optical counterpart of EP241126a.