TITLE: GCN CIRCULAR NUMBER: 40193 SUBJECT: EP250421a: JinShan likely optical counterpart DATE: 25/04/21 18:54:51 GMT FROM: Dong Xu at NAOC/CAS dxu@nao.cas.cn
S.Y. Fu (HUST), S.Q. Jiang, J. An, Z.P. Zhu, X. Liu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of EP250421a (ID: 01709135179) detected by EP/WXT, using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 16:25:07.32 UT on 2025-04-21, i.e., 8.64 min after the EP/WXT trigger, and a series of frames were obtained in the Sloan r-bands.
An uncatalogued optical source is detected within the EP/WXT error circle at coordinates
R.A.(J2000) = 11:29:40.80 Dec.(J2000) = -24:40:31.84
with an uncertainty of ~0.6 arcsec. The source has r ~ 20.6 mag, calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction. We think the source is likely the optical counterpart of EP250421a.
We acknowledge the excellent support from T.Q. Chen and Z.K. Feng for enabling these observations.
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