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.