TITLE: GCN CIRCULAR NUMBER: 43229 SUBJECT: GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection DATE: 25/12/24 11:03:12 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com> M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (OCA/IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 251222A / EP251222b detected by Fermi/GBM (Fermi GBM team, GCN 43186), SVOM (Yang et al., GCN 43188; Wang et al. GCN 43202), Einstein Probe (Guo et al., GCN 43201), Konus-WIND (Frederiks et al. GCN 43214) and Gecam-B (Guo et al., GCN 43218) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iTelescope 72 located in Chile and the TEC160FL telescope operated by M. Freeberg. Our observations started at TGRB+7.9h and were taken with Rc and sdss r and i filters. In our stacked frames, subtracted from the Pan STARRS DR2 template image, we detect the optical counterpart reported by SVOM/VT (Palmerio et al., GCN 43189, Li et al., GCN 43203), NOT (An et al., GCN 43194), Calapai Astronomical Observatory (Calapai et al., GCN 43195), PRIME (Durbak et al., GCN 43197), VLT/Xshooter (Saccardi et al., GCN 43204), DFOT (Gupta et al., GCN 43207, GCN 43224), LCO/1m (Saccardi et al., GCN 43208; Pérez-Fournon et al., GCN 43212), GOTO (Kumar et al., GCN 43209), SVOM/COLIBRÍ (FM-GFT) (Globus et al., GCN 43225) and ZTSH (Pankov et al., GCN 43226). We report our follow-up results in the table below: +---------------+-----------+------------+----------------+-------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+============+================+=============+ | 8.36 | 9 x 300s | Rc (Vega) | 19.28 +/- 0.03 | iT72 | | 9.95 | 15 x 180s | sdssr (AB) | 19.55 +/- 0.10 | TEC160FL | | 10.77 | 15 x 180s | sdssi (AB) | 19.45 +/- 0.17 | TEC160FL | | 32.8 | 12 x 300s | Rc (Vega) | 20.71 +/- 0.08 | iT72 | +---------------+-----------+------------+----------------+-------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousins filters were calibrated using the GAIA DR3 Synphot catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/43229. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...