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.