TITLE: GCN CIRCULAR NUMBER: 42474 SUBJECT: GRB 251025B: Kilonova-Catcher optical afterglow detection DATE: 25/10/27 12:53:57 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro@hotmail.com> M. Freeberg, R. Hellot (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 251025B detected by SVOM (Hussein et al., GCN 42437) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with a TEC160FL and a 0.43m Dall-Kirkham telescopes operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+5.7hr and were taken with BRc and sdss ri filters. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we detect the optical counterpart reported by SVOM/C-GFT (Wu et al., GCN 42438), MASTER (Gress et al., GCN 42439), SVOM/VT (Wu et al., GCN 42440), Swift/XRT (Beardmore et al., GCN 42445), GROWTH (Mohan et al., GCN 42447), IAC80 (Hernández Fung et al., GCN 42450), SVOM/COLIBRÍ (FM-GFT) (Pereyra et al., GCN 42452), WINTER (Mo et al., GCN 42459), OHP/T193 (Rakotondrainibe et al., GCN 42460), the MAO/AZT-22 (Rabajov et al., GCN 42466) and VLT/MUSE (Saccardi et al., GCN 42472). We report part of our follow-up results in the table below: +---------------+-----------+-----------+----------------+---------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+===============+ | 6.28 | 20 x 180s | B (Vega) | 20.58 +/- 0.16 | 0.43/DK | | 12.46 | 12 x 300s | r (AB) | 19.93 +/- 0.10 | CDK17 AITP | | 13.37 | 40 x 180s | r (AB) | 20.37 +/- 0.13 | TEC160FL | +---------------+-----------+-----------+----------------+---------------+ 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/42474. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...