TITLE: GCN CIRCULAR NUMBER: 36681 SUBJECT: X-ray transient EP240414a: Chandra late time observation DATE: 24/06/17 06:54:06 GMT FROM: P.G. Jonker at Radboud University <p.jonker@astro.ru.nl> P.G. Jonker (Radboud Univ. & SRON), A.J. Levan (Radboud Univ. & Warwick Univ.), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. Quirola-Vásquez (Radboud Univ.), Maria E. Ravasio (Radboud Univ.), F. E. Bauer (PUC), D. Mata Sanchez (IAC), M.A.P. Torres (IAC), report on behalf of a larger collaboration: We observed the location of the X-ray counterpart of the fast X-ray transient EP240414a reported by the Einstein Probe WXT instrument and FXT (Lian et al. GCN 36091; Guan et al. GCN 36129) using the Chandra X-ray Observatory. Observations started at 2024-06-16:05:35 UT and lasted for 10.7 ksec. The VFAINT observing mode was used. In a preliminary analysis we do not detect an X-ray counterpart to the transient. Two X-ray photons are detected in a circular region with a 1" radius, centred on the position of the optical transient reported in Aryan et al. (GCN 36094). Using Kraft et al. (1991) this leads to a 90% upper limit on the source count of ~4E-4 cnt/s. Using an absorbed power law model with index 1.7 for the source (N_H=3.35E20 cm-2) following the detected parameters of Guan et al. (GCN 36129), we obtain a flux upper limit of 8E-15 erg cm-2 s-1 (0.5-10 keV). This corresponds to an upper limit on the source luminosity of L_X<5E42 erg/s for the z=0.4 redshift of the source. The AGN at the centre of the host galaxy of EP240414a with (RA, Dec)=(12:46:02.0, -09:43:09.16) is detected with a count rate of 1.7E-3 cnt/s, which, for the same spectral parameters as above, yields a luminosity of 2E43 erg/s (0.5-10 keV). Care should be taken to remove the contribution of the AGN to earlier X-ray detections of EP240414a obtained with satellites with lower spatial resolution than Chandra. We like to thank the CXC director and team for approving and executing this observation. View this GCN Circular online at https://gcn.nasa.gov/circulars/36681. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...