TITLE: GCN CIRCULAR NUMBER: 37409 SUBJECT: GRB 240905E: NOT optical upper limits DATE: 24/09/06 12:14:36 GMT FROM: Dong Xu at NAOC/CAS <dxu@nao.cas.cn> S.Y. Fu (NAOC), L. Izzo (INAF-OACn & DARK/NBI), D. B. Malesani (DAWN/NBI and Radboud Univ.), D. Xu (NAOC), S.G. Sorensen, A. G. Theil, C. L. Theil, J. G. Hansen (Aarhus Univ.) report on behalf of a large collaboration: We observed the field of GRB 240905E detected by Swift/BAT (Dichiara et al., GCN 37397), and SVOM/GRM (Zhang et al., GCN 37404), using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. We obtained 3 x 300 s frames in the Sloan r-band, and 5 x 200 s as well as 5 x 300 s frames in z-band, starting at 2024-09-05T20:43:15.4, i.e., 2.29 hr after the Swift/BAT trigger. No optical source is detected in our stacked r- and z-band images within the refined Swift/XRT error circle (Ferro et al., GCN 37406). Preliminary results are as follows Tmid time | T-T0(hr) | U.L. (AB, 5 sigma) --------------------------------------- 2024-09-05T20:51:11.5 | 2.42 | 23.8 2024-09-05T22:16:31.5 | 3.84 | 22.7 calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/37409. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...