TITLE:   GCN CIRCULAR
NUMBER:  41732
SUBJECT: EP250905a: JinShan likely optical counterpart detection
DATE:    25/09/06 01:19:57 GMT
FROM:    Dong Xu at NAOC/CAS <dxu@nao.cas.cn>


L.B. He, X. Liu, J. An, D. Xu, S.Q. Jiang, Z.P. Zhu (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:

We observed the field of EP250905a detected by Einstein Probe (Cheng et al., GCN 41725), using the 100C telescope of the JinShan project, located at Altay, Xinjiang, China. We obtained 40 x 180 s Sloan i-band frames, starting from  2025-09-05 13:56:23 UT, i.e., 2.74 hrs since the EP trigger.

A new source is detected positionally in a known GLADE galaxy (GLADE+ #2980788) via image subtraction, which is within the EP-FXT 20-arcsec error circle , at coordinates

R.A. (J2000) = 0:17:48.01
Dec. (J2000) = +37:28:19.44

with an uncertainty of ~ 0.6 arcsec. The source has i ~ 22.9 mag, calibrated with PanSTARRS. 

We think the source is very likely the counterpart of EP250905a. In this case, the galaxy is the host with a redshfit of z ~ 0.28 from GLADE.

Further observations are planned and encouraged.