TITLE: GCN CIRCULAR NUMBER: 39096 SUBJECT: GRB 250129A: GRANDMA/TAROT optical afterglow detection DATE: 25/01/30 10:05:34 GMT FROM: Patrice Hello at IJCLAB, Orsay <patrice.hello@ijclab.in2p3.fr> S. Antier (OCA/IJCLAB), P. Hello (IJCLAB), P. Gokuldass (ERAU), A. Klotz (IRAP), C. Limonta, M. Boer, Q. Andre, A. Durroux (OCA), N. Guessoum (AUS), Haowei Peng (Tsinghua), C. Andrade, M. Coughlin (UMN), P-A Duverne (APC), S. Karpov (FZU), T. Pradier (Unistra/IPHC), D. Turpin (CEA-Saclay/Irfu) on behalf of the GRANDMA collaboration: we observed the field of GRB 250129A, detected by Swift (Beardmore et al., GCN 39066) using TAROT/TCH and TAROT/TCA. Observations began 1 min after T0 without filter, and we took a series of images with various exposure times from 1.76 min to 73 min post T0. We detected the optical afterglow candidate in he first (earliest) measurement with TAROT/TCH (5x30s exposure time) at T0+2.96min with mag=17.48 +/- 0.08 (in R band). The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), using Skymapper for reference. Processing of remaining data is ongoing. Our measurements are compatible with early measurements, GCNs 39070, 39072, 39073, 39074, 39078, 39079. 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/39096. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...