TITLE:   GCN CIRCULAR
NUMBER:  38628
SUBJECT: GRB 241217A / EP241217B: GRANDMA/T1MPicduMidi optical upperlimits
DATE:    24/12/18 21:51:30 GMT
FROM:    Thomas Hussenot-Desenonges at IJCLab <thomas.hussenot@ijclab.in2p3.fr>

T. Hussenot-Desenonges (IJCLAB), F.Colas (Obs-Paris), L. De Almeida, W. Corradi, N. Sasaki, F. Navarete (LNA), H. Peng (THU), H. Lau Jun Xian (Tsinghua Univ.), S. Antier (OCA), C. Andrade (UMN), S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), A. Klotz (IRAP), D. Turpin (CEA-Saclay/Irfu) on behalf of the GRANDMA collaboration:

We observed the field of GRB 241217A / EP241217B, detected by SVOM/ECLAIRs (GCN 38594) and Einstein Probe (GCN 38606), using T1MPicduMidi, starting 5 hours after T0.

We obtain the following optical 5-sigma upperlimit at the SVOM/VT position (GCN 38600):

| Tstart (UTC) | Telescope | Exposure | Filter | Magnitude |

| 2024-12-17T22:09:50 | T1MPicduMidi  | 126x60s | r | >21.46 (AB) | 

We also do not detect any uncatalogued sources within the SVOM/ECLAIRs error region, down to a 5-sigma upper limit of r > 21.35 (AB).

All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), and calibrated with the Pan-STARRS DR1 catalogue. 

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).