GCN Circular 12625

D. Xu (WIS) reports on behalf of a larger collaboration:

We re-processed 1x600s R-band and 3x600s z-band images (Zhao et al.,
GCN 12560
Not found
 
 
), starting 1.960 hrs post-burst,  with calibration frames
available later on. The R-band non-detection remains unchanged.

However, in the stacked z-band image an optical source was weakly
detected, with its position consistent with the NOT position (Andersen
et al., GCN 12563
Not found
 
 
), the refined XRT position (Melandri et al., GCN
12565
Not found
 
 
), as well as the refined Chandra position (Berger et al., GCN
12588
Not found
 
 
), and to the magnitude of z=22.9+/-0.3, calibrated with nearby
SDSS stars. The z-band afterglow faded and was not detected by
following GROND observation (Schmidl et al., GCN 12568
Not found
 
 
).