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GCN Circular 40260

Subject

EP250427a: TRT optical counterpart detection

Event

EP250427a

Date

2025-04-27T10:13:08Z (2 months ago)

From

Dong Xu at NAOC/CAS <dxu@nao.cas.cn>

Via

Web form

X. Liu, Z.P. Zhu, S.Q. Jiang (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), S.Y. Fu (HUST), J. An, 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 EP250427a (Wang et al., GCN 40257Loading...
 
 ), using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Cerro Tololo Inter-American Observatory, Chile. Observations started at 07:24:25.019 UTC on 2025-04-27, i.e., ~3.67 hr after the EP/WXT trigger and 6x200 s frames in the Sloan r-band were obtained. 

An uncatalogued and varying optical source is detected within the EP/FXT error circle (Wang et al., GCN 40257Loading...
 
 ) at coordinates

R.A. (J2000) = 18:29:05.73
Dec. (J2000) = +7:33:46.27

with an uncertainty of ~ 0.5 arcsec. Preliminary photometry shows that the source has r ~ 17.9 mag at 3.96 hr post-trigger, calibrated with Pan-STARRS DR2 catalog and not corrected for Galactic extinction.

We think that this source is the optical counterpart of the event.