TITLE: GCN CIRCULAR NUMBER: 44981 SUBJECT: GRB 260610B/AT 2026owq: FTW optical and NIR observations DATE: 26/06/18 19:32:02 GMT FROM: Julius Gassert at Ludwig-Maximilians-Universität München <julius.gassert@campus.lmu.de> Julius Gassert (LMU/CMU), Malte Busmann (LMU), Brendan O'Connor (CMU), Daniel Gruen (LMU), Xander Hall (CMU), and Antonella Palmese (CMU) report: We observed the afterglow of GRB260610B (AT 2026owq) (Fermi/GBM; GCN 44901; O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946), with the Three Channel Imager (3KK) at the Fraunhofer Telescope at Wendelstein Observatory (FTW) in the g, r, i, z, and J bands for 8x 180s starting at 2026-06-17 22:48 UT. As previously reported (Gillanders et al., GCN 44955; Angulo et al., GCN44958; Dimple et al., GCN44959; Moksvitin et al. GCN44963; Pankov et al., GCN44977), we also detect the rebrightening/flattening in all bands, althought the i-band detection is marginal. In the r band, we detect the counterpart at: r = 21.31 +/- 0.10 AB mag The magnitude is calibrated against the PS1 catalog and not corrected for Galactic extinction. We thank Silona Wilke from the Wendelstein Observatory for obtaining these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44981. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...