TITLE:   GCN CIRCULAR
NUMBER:  37544
SUBJECT: EP240918a: GMG Optical Upper Limit
DATE:    24/09/18 15:44:35 GMT
FROM:    wangbaiting@ynao.ac.cn

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

We observed the field of EP240918a (Zhang et al., GCN 37541, T0 at 2024-09-18T11:24:37) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2024-09-18T14:02:51, about 2.64 hours after the trigger.

No new credible optical counterpart of EP240918a was detected within the EP-FXT error circle (GCN 37541).

The preliminary analysis results are shown as follows:
+----------------+------------+----------+----------------+
|  Tmid-T0 [hr]  |  Exp. [s]  |  Filter  |  5-sigma U.L.  |
+================+============+==========+================+
|      2.72      |    600     |    R     |      20.5      |
+----------------+------------+----------+----------------+
The given magnitudes are derived based on calibrating against Pan-STARRS1 field stars.

We acknowledge the staff at the Lijiang Observatory for conducting the observation.