TITLE:   GCN CIRCULAR
NUMBER:  39476
SUBJECT: EP250223a: GMG Optical Observation
DATE:    25/02/26 04:26:24 GMT
FROM:    Boting Wang at Yunnan Observatories, CAS <wangbaiting@ynao.ac.cn>

B.-T. Wang, R.-Z. Li, F.-F. Song, J. Mao, D.-Q. Wang, and J.-M. Bai (YNAO, CAS) report:

We observed the field of EP250223a (Lian et al., GCN 39429, T0 at 2025-02-23T15:04:35.749) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2025-02-25T12:45:36.92, about 45.68 hours after the trigger. The optical counterpart of EP250223a (Hauptmann et al., GCN 39436; Wu et al., GCN 39439; Pérez-Fournon et al., GCN 39440; Izzo et al., GCN 39441; Xin et al., GCN 39445; Guo et al., GCN 39447; An et al., GCN 39449; Ducoin et al., GCN 39453; O’Neill et al., GCN 39455; Aryan et al., GCN 39464; Saikia et al., GCN 39472), with a redshift of 2.756 (Levan et al., GCN 39438), was detected within the error box of EP/FXT (Lian et al., GCN 39429).

The preliminary analysis results are shown as follows:
| tmid-t0 (hours) | Filter | Exposure (s) | Magnitude (AB) | 5-sigma U.L. |
| ----------- |------- | ------------------ | -------------- | ------ |
|    45.85    |   sdssr   |      1200         | 20.82 +/- 0.08 | 21.9 |

The given magnitudes are derived based on calibration against Pan-STARRS1 field stars and are not corrected for the expected Galactic foreground extinction.

We warmly thank the staff at the Lijiang Observatory for their efforts in conducting the observation.