TITLE: GCN CIRCULAR NUMBER: 42338 SUBJECT: GRB 251013C: OHP/T193 third epoch optical observations and detected rebrightening DATE: 25/10/17 21:44:41 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> C. Adami (LAM/Pytheas/AMU), N.A. Rakotondrainibe (LAM), E. Le Floc'h (CEA/Irfu), S. Basa (Pytheas/OHP/LAM), B. Schneider (LAM), report on behalf of the MISTRAL GRB collaboration: We carried out further observations of the GRB 251013C optical, NIR, and radio afterglow (Palmerio et al., GCN 42223 ; Perez-Garcia et al., GCN 42225 ; Konno et al., GCN 42226 ; Martin-Carrillo et al., GCN 42227 ; Masi et al., GCN 42228 ; Palmerio et al., GCN 42229 ; Moskvitin et al., GCN 42230 ; Gompertz et al., GCN 42231 ; Lipunov et al., GCN 42235 ; Garnavich, GCN42240; Watson et al., GCN 42241 ; Lopez-Camara et al., GCN 42242 ; Laskar et al., GCN 42243; Zhang et al., GCN 42248; Brosio et al., GCN 42251; Reguitti et al., GCN 42253 ; Quintana-Ansaldo et al., GCN 42254; Maksut et al., GCN 42256; Ghosh et al., GCN 42261 ; Quadri et al., GCN 42262 ; Adami et al. GCN 42266 ; Peretto et al., GCN 42267 ; Ruocco et al., GCN 42269 ; Calapai, GCN 42275; Adami et al., GCN 42276; Globus et al., GCN 42279; Abidkhanov et al., 42283; Rhodes et al., GCN 42294; Siegel et al., GCN 42298; Leonini et al., GCN 42301; Christy et al., GCN 42312; Moreno Méndez et al., GCN 42318; He et al., GCN 42319; Pavoni et al., GCN 42333; Bochenek et al., GCN 42334) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 4 exposures of 10min in the r-band at a mid time of 2025-10-17 19:05:33UT, corresponding to T-T0 = 97.43 hr. The afterglow is well detected and we measured the following preliminary magnitude: r’ = 20.74+/-0.06 mag (AB) This clearly shows a rebrightening as compared to our second epoch observations (r’ = 21.29 +/- 0.07), consistently with the results of Moreno Méndez et al. (GCN 42318). The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025). We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Yoann Degot-longhi and the SOPHIE observers H. Bouy View this GCN Circular online at https://gcn.nasa.gov/circulars/42338. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...