TITLE:   GCN CIRCULAR
NUMBER:  40353
SUBJECT: GRB 250504A: VLT/X-shooter upper limits
DATE:    25/05/05 19:26:55 GMT
FROM:    Andrea Saccardi at CEA/Irfu <andrea.saccardi@cea.fr>

A. Saccardi (CEA/Irfu), M. Garnichey (LUX-Paris Obs.), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), A. Martin-Carrillo (UCD), B. Schneider (LAM), N. R. Tanvir (Leicester), A. de Ugarte Postigo (LAM) report on behalf of the Stargate collaboration:

We observed the field of GRB 250504A detected by Fermi/GBM (Fermi GBM team, GCN 40342; Bala et al., GCN 40346) and Swift/BAT (Moss et al., GCN 40343) using the ESO VLT UT3 (Melipal) with the X-shooter acquisition camera.

A short sequence of imaging was secured in the r (3x30 s), g (3x60 s), and z (3x40 s) bands. No afterglow is detected consistent with the optical position reported by de Wet et al. (GCN 40347) with the following 5 sigma upper limit calibrated against nearby SkyMapper stars:

r > 23.4 (AB) on 2025 May 05 at 03:21:58 UT (3.93 hr after the burst).

We acknowledge excellent support from the ESO observing staff in Paranal, in particular Abigail Frost, Florian Rodler, Marco Berton, and Rodrigo Palominos.