GCN Circular 38111

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
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; DeLaunay et al., GCN 38091
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; Konus-Wind team, GCN 38103
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) 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
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) 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
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; SVOM/VT team, GCN 38099
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; Izzo et al. GCN 38097
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; Hu et al., GCN 38106
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), 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.