TITLE: GCN CIRCULAR NUMBER: 44139 SUBJECT: The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart DATE: 26/03/29 11:11:13 GMT FROM: Wenxiong Li at NAOC <liwenxiong1992@gmail.com> Wenxiong Li, Runduo Liang (NAOC), Iair Arcav, Ido Keinan (TAU), David Sand (U of Arizona) We observed the position of EP-WXT trigger 01709259209 with a Las Cumbres 1m telescope at Siding Spring Observatory, Australia, 6 mins after the Einstein Probe WXT trigger. We took 2x300s exposures in the broad optical w-band. We find an uncataloged source at RA=181.3124, Dec=4.3516 within the EP-WXT error circle and measure the following preliminary photometry calibrated to the r band: Epoch 1: MJD 61128.446 Mag 18.7 Epoch 2: MJD 61128.450 Mag 17.1 The presented magnitudes are calibrated using Pan-STARRS sources in the field and are not corrected for Galactic extinction. We identify a faint source at this position in the Legacy Survey data, with r=24.08 mag. Additional follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44139. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...