TITLE: GCN CIRCULAR NUMBER: 45449 SUBJECT: GRB 260808B: SAO RAS observations of the optical rebrightening DATE: 26/08/26 16:26:53 GMT FROM: Alexander Moskvitin at SAO RAS <mosk@sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of the GRB 260808B discovered by the SVOM (Bouchet et al., GCN 45316; Brunet et al., GCN 45333), and also detected by EP-FXT (Wang et al., GCN 45322) with the Zeiss-1000, SAO RAS telescope + CCD photometer. A set of 7 x 300 sec images in Rc band were obtained on August 12, 22:44:17 -- August 13, 00:05:06 UT. The OT (Turpin et al., GCNs 45317; 45318; Li et al. GCN 45320; Adami et al., GCN 45323; Saccardi et al., GCN 45328; Schneider et al., GCN 45329; Bochenek and Perley, GCN 45330; Basa et al., GCN 45341; Burkhonov et al., GCN 45352; Li et al. GCN 45359; Moskvitin et al., GCN 45360; Guelfand et al., GCN 45364; de Ugarte Postigo et al. GCN 45379; Bochenek and Perley, GCN 45380) is clearly detected in our stacked image. Details of the observation are the following. Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-08-12 22:44:17 4.37759 7*300 Rc 21.52 +/- 0.06 23.6 In comparison with our first epoch of observations (~0.42 days, see Moskvitin et al., GCN 45360) OT became 0.9 mag brighter. We can confirm rebrightening reported by Li et al. GCN 45359 and Guelfand et al., GCN 45364. The preliminary photometry (Vega) is based on nearby SDSS stars (Lupton 2005 transformation) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/45449. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...