TITLE: GCN CIRCULAR NUMBER: 43877 SUBJECT: EP260227a: Thai National Telescope observations DATE: 26/02/28 12:41:42 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), S. Littlefair (Sheffield), V. Dhillon (Sheffield), I. Pelisoli (Warwick), J. van Dalen (Radboud), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), D. Mata-Sanchez (IAC and ULL), report on behalf of a larger collaboration: We observed the position of the fast X-ray transient EP260227a (Wang et al., GCN 43869) with the 2.4m Thai National Telescope equipped with the ULTRASPEC instrument. Observations were conducted in the KG5 wideband filter which approximately covers the wavebands of the SDSS ugr filters (https://tinyurl.com/kg5filter; Hardy et al. 2017). The total exposure time was 62 minutes with a mid time of 2026-02-27 22:28:00 UT (2.52 hr after trigger). We clearly detect the optical counterpart (Eyles-Ferris et al., GCN 43867; Li et al., GCN 43868; Fu et al., GCN 43873; Mandarakas et al., GCN 43874; Eyles-Ferris & Tanvir, GCN 43875; Malesani et al., GCN 43876) at a magnitude m_KG5 = 23.57 +/- 0.07 (AB) calibrated to Pan-STARRS and not corrected for Galactic extinction. The faint magnitude compared to other photometry is likely attributable to the peak response of the adopted filter in the blue and the red colour of the source, broadly consistent with the DLA suggested by Malesani et al (GCN 43876). View this GCN Circular online at https://gcn.nasa.gov/circulars/43877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...