TITLE: GCN CIRCULAR NUMBER: 37074 SUBJECT: GRB 240805B: JinShan optical afterglow detection DATE: 24/08/06 15:03:47 GMT FROM: Dong Xu at NAOC/CAS dxu@nao.cas.cn

Z.P. Zhu, X. Liu, J. An, S.Y. Fu, S.Q. Jiang, L.B. He, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:

We reported JinShan optical upper limits (GCN 37050) at the Swift/XRT position of GRB 240805B (Williams et al., GCN 37043).

Later on, the Enhanced Swift-XRT position was available (Goad et al., GCN 37053), which has a quite positional shift compared to the early position (Williams et al., GCN 37043).

Checking the Enhanced Swift-XRT position in the JinShan images, we find the optical afterglow (e.g., Moskvitin et al., GCN 37055; Du et al., GCN 37062) is detected in the r-/i-/z- bands. Thus, the updated preliminary results are as follows:

Telescope Tmid-T0/hr Filter Exptime Mag(AB) MagErr 50D 1.683 g 20x180s >21.5 - 100C 0.582 r 5x200s 20.03 0.06 100C 0.868 i 5x200s 18.79 0.02 100C 1.318 z 7x300s 18.79 0.02

We acknowledge the excellent support from S.W. Luo, M.M. Yang, Z.K. Feng, Q.C. Zhao and L.F. Huo for enabling these observations.

View this GCN Circular online at https://gcn.nasa.gov/circulars/37074. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...