TITLE: GCN CIRCULAR NUMBER: 44272 SUBJECT: GRB 260411B: Ondrejov D50 optical afterglow detection DATE: 26/04/12 01:09:43 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek@asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, A. Malenakova, R. Hudec (ASU CAS Ondrejov) report: We observed the position of the optical afterglow of GRB 260411B (Fermi GBM team, GCN 44262; O'Neill et al., GCN 44265) with the D50 robotic telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We performed a series of 80x60s exposures in the SDSS r' filter. We faintly detect the optical afterglow (O'Neill et al., GCN 44265) in the 80x60s combined image with exposure mean time 11.45 h after the trigger. The AB magnitude of the object is: r' = 20.0 +/- 0.3 Photometric calibration was performed using the ATLAS REFCAT2 (Tonry et al.) catalog. The magnitude is not corrected for Galactic extinction in the direction of the burst. Comparing with the GOTO detection at t = 0.89 h (L = 17.55 +/- 0.02; O'Neill et al., GCN 44265), this would imply a temporal decay index of alpha ~ 0.9 (where F_nu ~ t^-alpha). View this GCN Circular online at https://gcn.nasa.gov/circulars/44272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...