TITLE:   GCN CIRCULAR
NUMBER:  31492
SUBJECT: GRB 220117B: z-band limit
DATE:    22/01/18 21:55:44 GMT
FROM:    Daniele B Malesani at Radboud U  <d.malesani@astro.ru.nl>

A. Rossi (INAF/OAS), J. Palmerio (CNRS, GEPI - Paris Observatory), D. B. 
Malesani (Radboud Univ. and DAWN/NBI), N. R. Tanvir (Univ. Leicester), 
D. A. Kann (IAA/CSIC) report on behalf of the Stargate collaboration:

We observed the field of GRB 220117B (Melandri et al., GCN 31468) using 
the acquisition camera of the X-shooter spectrograph, mounted on the ESO 
VLT UT3 (Melipal). A single z-band image (120 s exposure time) is 
available to us, taken approximately on January 18.2 UT (about 8.3 hr 
after the GRB).

Inside the XRT position (Evans et al., GCN 31473), we detect no source 
down to a limiting magnitude z > 21.5 mag (AB, 3 sigma limit).

We acknowledge excellent support from the ESO observing staff in 
Paranal, in particular Michael Abdul-Masih, Diego Parraguez, and 
Jonathan Smoker.