TITLE: GCN CIRCULAR NUMBER: 38290 SUBJECT: EP241119a: Optical upper limits with Kinder observations DATE: 24/11/21 15:34:14 GMT FROM: Janet Chen at National Central University <janetstars@gmail.com> A. Aryan, T.-W. Chen, W.-J. Hou (all NCU), A. K. H. Kong (NTHU), J. Gillanders (Oxford), S. J. Smartt (Oxford/QUB), Y. J. Yang, A. Sankar. K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, H.-C. Lin, C.-H. Lai, C.-S. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), L. L. Fan, S. Yang, Z. N. Wang, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP241119a (Zhang et al., GCN 38281; Lipunov et al., GCN 38282; Ahumada et al., GCN 38286; Saikia et al., GCN 38288) using the 40cm SLT at the Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al., 2024arXiv240609270C). The first SLT epoch of observations started at 17:07 UTC on 20th November 2024 (MJD 60634.713), 23.22 hr after the EP WXT trigger. We utilized the astroalign (Beroiz et al., 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al., 2022, ApJ, 935, 167) packages to align and stack the individual frames. We did not find any new and uncataloged optical source in the stacked frames within the 10 arcsecond error circle of the EP-FXT localization (Zhang et al., GCN 38281). However, we detected two SDSS sources within this error circle; they are both SDSS stellar sources. One is SDSS J053625.59+035023.6, reported by Ahumada et al. (GCN 38286) and the other one weakly detected is SDSS J053625.20+035021.4 with SDSS r_mag~21.97. Moreover, we utilized the Python-based package AutoPhOT (Brennan & Fraser, 2022, A&A, 667, A62) to perform aperture photometry on our stacked frames. The details of the observations and measured 3-sigma upper limit (in the AB system) are as follows: ---------------------------------------------------------------------------------------------------- Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 60634.713 | 23.22 | 300 * 21 | > 21.2 | 1".89 | 1.09 The presented magnitude was calibrated using the field stars from the Pan-STARRS1 catalog and was not corrected for the expected Galactic foreground extinction corresponding to a reddening of E(B-V) = 0.24 mag (AB) in the direction of the transient (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/38290. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...