TITLE:   GCN CIRCULAR
NUMBER:  38111
SUBJECT: GRB 241105A: VLT/FORS2 optical afterglow rapid fading
DATE:    24/11/07 14:59:37 GMT
FROM:    Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra@roma2.infn.it>

Simone Dichiara (PSU), Eleonora Troja (U Rome), Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome)  report:

We observed the field of GRB 241105A (Fermi GBM team, GCN 38085; DeLaunay et al., GCN 38091; Konus-Wind team, GCN 38103) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 1.5 days after the trigger and were carried out in the R and z filters through good seeing conditions (0.8"). 

We detect the optical counterpart (Julakanti et al., GCN 38088) at a preliminary magnitude 
R ~22.5 AB mag calibrated using nearby stars in the Legacy Survey DR10 (Dey et al. 2019). Compared with earlier optical detections (Julakanti et al., GCN 38088; SVOM/VT team, GCN 38099; Izzo et al. GCN 38097; Hu et al., GCN 38106), our observations show a rapid decline of the afterglow brightness, consistent with a power-law of slope ~-1.7. 

Further observations are planned. 

We thank the staff at the VLT, especially Maria Jose Rain, for the rapid execution of these observations.