TITLE: GCN CIRCULAR NUMBER: 38500 SUBJECT: GRB 241209A: GRANDMA/TAROT upper limit DATE: 24/12/09 21:20:40 GMT FROM: marion.pillas@ligo.org M. Pillas (ULiege), S. Antier (OCA), O. Pyshna (Caltech), N. Guessoum (AUS), A. Klotz (IRAP), C. Andrade (UMN), M. Boer, C. Limonta (OCA), S. Karpov (FZU), M. Coughlin (UMN), , P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), D.Turpin (CEA-Saclay/Irfu), on behalf of the GRANDMA collaboration: We observed the field of GRB 241209A, detected by Fermi/GBM (GCN 38474) and SWIFT/BAT (GCN 38476) using TAROT,/TCA and TCH. Observations began 3.5 min after Swift/T0 for TCA and 3.7 minutes after the trigger for TCH and both without a filter and continue up to 180 min after T0. Weather was not great at TCA with an upper limit of 16 mag in r-mag of the image. We did not detect any optical afterglow candidate with TCH to an upper limit of 19 mag in r and from T0+3 min to T0+6.1min within a circle of 6 arcmin radius centered on the most updated Swift/XRT source location (GCN 38486). It is consistent with GOTO's report (GCN 38481) and VLT's report (GCN 38484). All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). 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/38500. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...