TITLE: GCN CIRCULAR NUMBER: 36998 SUBJECT: EP240801a: TRT optical counterpart detection DATE: 24/08/01 14:58:20 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> S.Y. Fu, J. An (NAOC), S. Tinyanont, R. Anutarawiramkul, P. Butpan (NARIT), X. Liu, S.Q. Jiang, Z.P. Zhu, D. Xu, Z. Fan, W.X. Li, N.C. Sun, Y.N. Wang (NAOC) report on behalf of a large collaboration: We observed the field of EP240801a detected by Einstein Probe (EP, Zhou et al., GCN 36997), using the 0.7-m telescope of the Thai Robotic Telescope (TRT) network, located at Sierra Remote Observatories, USA. Observations started at 11:06:18 UT on 2024-08-01, i.e. 2.24 hr after the trigger, and 6 x 300 s frames were obtained in the R-band. An uncatalogued source is detected in the individual as well as the stacked frames within the EP/FXT error circle (Zhou et al., GCN 36997) and localized at coordinates R.A. (J2000) = 23:00:39.019 Dec. (J2000) = +32:35:37.20 with an uncertainty of ~ 0.5 arcsec. The source has R = 20.32 +/- 0.16 mag, calibrated with PanSTARRS and not corrected for Galactic extinction. There is no known source at the above position by checking MPC. We thus conclude that the source is the optical counterpart of EP240801a. Further observations are planned. View this GCN Circular online at https://gcn.nasa.gov/circulars/36998. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...