TITLE: GCN CIRCULAR NUMBER: 44021 SUBJECT: GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations DATE: 26/03/15 16:12:58 GMT FROM: A. Brosio at ABObservatory Rosarno <antonino.brosio@gmail.com> A. Brosio (ABObservatory Rosarno), M. A. Tripodi (ABObservatory Rosarno), S. Savaglio (Università della Calabria), S. Benatti, M. G. Guarcello (INAF - Osservatorio Astronomico di Palermo), M. Basilicata, L. Cabona, M. Rainer, F. M. Zerbi (INAF - Osservatorio Astronomico di Brera), G. Bracco, P. Cianfarra, L. Sangaletti, S. Tosi, S. Zappatore (Università di Genova), A. Di Dato (INAF - Osservatorio Astronomico di Capodimonte), D. Liguori (Osservatorio "G. Galilei", Liceo Scientifico Cariati), S. Masiero, A. Nastasi (GAL Hassin, Isnello), R. Nesci (Associazione Astronomica Antares APS di Foligno), L. Betti, E. Pace, R. Stanga (Università di Firenze), D. Ricci (INAF - Osservatorio Astronomico di Padova) for the NOCTIS team report We observed the transient AT 2026fgk, proposed as the likely optical counterpart of GRB 260310A (Konno et al., GCN 43974; Hamburg & Meegan,GCN 43975). Observations were carried out on 2026-03-14.80913 UT with the 0.30-m f/4 telescope at ABObservatory in clear band The obtained photometry is: 2026-03-14.80913 UT JD 2461114.30913 m_CV = 18.50 +/- 0.04 mag The measurement was calibrated against two APASS catalog stars,selected using Aladin. The reported magnitude is in the CV system. This measurement confirms that the optical counterpart is still clearly detected about 4.6 days after the GRB trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/44021. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...