{
  "bibcode": "2024GCN.36105....1X",
  "subject": "EP 240414a: NOT optical counterpart confirmation",
  "eventId": "EP240414a",
  "createdOn": 1713156868401,
  "circularId": 36105,
  "submitter": "Dong Xu at NAOC/CAS <dxu@nao.cas.cn>",
  "submittedHow": "email",
  "body": "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:\n\nWe 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.\n\nThe previously reported optical counterpart candidate by LOT (Aryan et al., GCN 36094) is clearly detected in our stacked image with coordinates\n\nR.A. = 12:46:01.67 (J2000)\nDec. = -09:43:08.8 (J2000)\n\nwhich 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.\n\nWe 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.\n\nWe thus confirm that the LOT candidate is the optical counterpart of EP 240414a.\n\n"
}