TITLE: GCN CIRCULAR NUMBER: 37412 SUBJECT: GRB 240905E: OHP/MISTRAL T193 optical upper limit DATE: 24/09/06 13:25:53 GMT FROM: Christophe Adami at LAM <christophe.adami@lam.fr> C. Adami (OSU Pytheas, LAM), M. Dennefeld (Sorbonne U., IAP/CNRS), B. Schneider (MIT), S. Basa (OSU Pytheas, LAM), F. Schüssler (CEA-Paris Saclay, DPhP), E. Le Floc'h (CEA Paris-Saclay, DAp/AIM), A. Saccardi (GEPI/Obs. de Paris) report on behalf of the MISTRAL GRB collaboration: We observed the field of GRB 240905E (Dichiara et al., GCN 37397; Zhang et al., GCN 37404) using the MISTRAL instrument at the 193cm telescope of Observatoire de Haute-Provence (France). We performed a series of 5 exposures of 600 sec plus one of 900s in the r’-band for a total of 3900 sec on September 5 from 19:34 to 21:05 UT (observation mid-time ~2h after GRB trigger). We do not detect any source within the XRT error region. This result is consistent with the optical upper limits obtained by other groups (Lipunov et al., GCN 37398; An et al., GCN 37399; Moskvitin et al., GCN 37401; Shilling et al., GCN 37402; Strausbaugh et al., GCN 37403; Brivio et al., GCN 37408; Fu et al., GCN 37409). Calibrating our data with the PanSTARRS survey, we obtain the following 3sigma lower limit on the r’ magnitude : r’ > 22.85 (AB). The magnitude is not corrected for Galactic extinction. We thank the OHP for its excellent support, in particular Jean Pierre Troncin. We also thank the SOPHIE observer Yasmin Davis. View this GCN Circular online at https://gcn.nasa.gov/circulars/37412. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...