TITLE:   GCN CIRCULAR
NUMBER:  40511
SUBJECT: GRB 250520A: VLT/FORS2 Optical Observation
DATE:    25/05/21 14:13:02 GMT
FROM:    Yu-Han Yang at University of Rome Tor Vergata <yyang@roma2.infn.it>

Yu-Han Yang (U Rome), Rosa L. Becerra (U Rome) and Eleonora Troja (U Rome) report on behalf of the ERC BHianca team:

We observed the field of GRB 250520A (Eyles-Ferris et al., GCN 40491) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 27.8 hours after the trigger and were carried out in the R filter with an average airmass of ~1. 

We detect the source previously reported as a candidate from SVOM/VT (Xin et al., GCN 40500) with a preliminary magnitude of R~23 AB mag, calibrated using nearby stars from the Pan-STARRS DR2 (Flewelling et al., 2020, ApJS, 251, 7), uncorrected for Galactic extinction. Compared to the magnitude reported by SVOM/VT (Xin et al., GCN 40500), we find no evidence of fading.

No other source is detected within the XRT error circle (Goad et al. GCN 40494) down to R>24.6 (3-sigma).

We thank the staff at the VLT for the rapid execution of these observations.