TITLE:   GCN CIRCULAR
NUMBER:  35749
SUBJECT: GRB 240218A: VLT/FORS2 z-band detection
DATE:    24/02/18 15:18:26 GMT
FROM:    Daniele B. Malesani at IMAPP / Radboud University <d.malesani@astro.ru.nl>

We observed the near-infrared counterpart of GRB 240218A (Page et al., GCN 35742; D'Avanzo et al., GCN 35747) using the ESO VLT UT1 (Kueyen) equipped with the FORS2 imager. Observations were carried out in the Gunn z filter.

The GRB counterpart discovered by REM (D'Avanzo et al., GCN 35747) is well detected in the coaddition of our images (1080 s exposure time), at a mean epoch Feb 18.205 UT (2.925 hr after the GRB). Calibrated against nearby stars from the Pan-STARRS catalog, we preliminarily measure a magnitude z = 23.8 +- 0.15 (AB).

We acknowledge expert support from the VLT observing staff in Paranal, in particular Thomas Szeifert, Jonathan Smoker, Martina Baratella, and Juan Carlos Olivares.