TITLE:   GCN CIRCULAR
NUMBER:  36529
SUBJECT: EP240518a: GSP optical upper limit
DATE:    24/05/22 09:08:13 GMT
FROM:    Wenxiong Li <liwenxiong1992@gmail.com>

W. X. Li, S. J. Xue (NAOC), M. Andrews, J. Farrah, D. A. Howell, M. Newsome, E. Padilla Gonzalez, C. McCully, and G. Terreran (Las Cumbres Observatory), on behalf of a larger collaboration, report:
Following the detection of the fast X-ray transient EP240518a by the Einstein Probe (Wu et al., GCN 36512; Wu et al., GCN 36514), we initiated observations of the transient's location in the r band on May 18 at 16:46 UT, ~4 hours after the trigger. These observations were conducted using the 1-meter telescope at the Las Cumbres Observatory node located at Siding Spring Observatory in Australia.

We report that no new optical source was detected in the co-added images within the EP/FXT error box down to a limiting magnitude of ~21.5. The possible M-type dwarf star named Gaia DR3 5899529595616014848, mentioned in Wu et al. (GCN 36514), was detected without significant variation compared to archival DECam images.

These observations were taken as part of the Global Supernova Project.