TITLE: GCN CIRCULAR NUMBER: 36105 SUBJECT: EP 240414a: NOT optical counterpart confirmation DATE: 24/04/15 04:54:28 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> D. Xu (NAOC), D.B. Malesani (DAWN/NBI & Radboud), P. Jonker (Radboud), Z.P. Zhu, X. Liu, S.Y. Fu, S.Q. Jiang, J. An, T.H. Lu (NAOC), M. Turkki (U. of Helsinki, NOT) report on behalf of a large collaboration: We observed the field of the X-ray transient detected by Einstein Probe, EP 240414a, using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 22:07:38UT on 2024-04-14, i.e., 12.29 hr after the EP trigger and 5 x 300 s r-band frames were obtained. The previously reported optical counterpart candidate by LOT (Aryan et al., GCN 36094) is clearly detected in our stacked image with coordinates R.A. = 12:46:01.67 (J2000) Dec. = -09:43:08.8 (J2000) which has r = 21.9 +/- 0.1 (AB) at a median time of 0.521 day post-trigger. Comparison of the two observations shows that the source was decaying slowly. We also searched for other potential counterparts in the NOT image which covers most of the EP/WXT error region, and didn't find any other credible candidate via image subtraction. We thus confirm that the LOT candidate is the optical counterpart of EP 240414a. View this GCN Circular online at https://gcn.nasa.gov/circulars/36105. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...