TITLE: GCN CIRCULAR NUMBER: 44546 SUBJECT: EP260509a: LCO optical upper limits DATE: 26/05/11 12:37:13 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1@leicester.ac.uk> R. A. J. Eyles-Ferris (Leicester), G. Corcoran (UCD), P. G. Jonker (Radboud), J. A. Chácon (PUC), F. E. Bauer (SSI and UTA), report on behalf of a larger collaboration: We observed the field of the X-ray transient EP260509a (Wang et al., GCN 44517; Fu et al., GCN 44539) using LCO 1m telescopes located at the Cerro Tololo Inter-American Observatory (Chile) and McDonald Observatory (USA) equipped with SINISTRO instruments. A series of 6x300 s exposures were taken in each of the SDSS-r and SDSS-z filters, starting at 2026-05-10 08:04:39 UT and 2026-05-10 06:53:47 UT respectively (~17.2 and 18.3 hr after the first X-ray detection). No new source is detected within or at the border of the EP/WXT uncertainty region (Wang et al., GCN 44517) nor do we identify any significant residuals in subtractions using PanSTARRS DR1 templates. From the stacked images, we obtain the following 3-sigma upper limits: r > 22.8 z > 21.4 These upper limits are in AB magnitudes, calibrated using nearby stars from the PanSTARRS catalogue, and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44546. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...