TITLE: GCN CIRCULAR NUMBER: 37547 SUBJECT: EP240918a: JinShan optical upper limits DATE: 24/09/18 16:46:22 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> S.Y. Fu, X. Liu, S.Q. Jiang, J. An, Z.P. Zhu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of EP240918a detected by EP/WXT (Zhang et al., GCN 37541), using the 50cm-A/B and 100cm-C telescopes (50A, 50B and 100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 13:38:24 UT on 2024-09-18, i.e., 2.23 hr after the EP trigger, and a series of frames were obtained in the Sloan g-, r-, i- and z- bands. No new optical source is detected within the EP/FXT error circle (Zhang et al., GCN 37541), down to the following 5-sigma upper limits: T_mid (UT) | T_mid (hr) | Telescope | filter | U.L. (AB) ---------------------------------------------------- 2024-09-18T13:53:45.0 | 2.49 | 50B | z | 17.1 2024-09-18T13:55:53.5 | 2.52 | 50A | r | 19.3 2024-09-18T14:24:52.5 | 3.00 | 50B | i | 18.2 2024-09-18T14:26:51.0 | 3.04 | 50A | g | 19.2 2024-09-18T15:52:16.8 | 4.46 | 100C | r | 21.2 calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction. We acknowledge the excellent support from X. Yao, S.W. Luo, and Z.K. Feng for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/37547. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...