TITLE: GCN CIRCULAR NUMBER: 40859 SUBJECT: GRB 250628A: VLT/X-shooter upper limits DATE: 25/06/28 14:12:36 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio@inaf.it> R. Brivio (INAF-OABr), A. Martin-Carrillo (UCD), G. Corcoran (UCD), L. Izzo (INAF/OAC), A. Rossi (INAF/OAS), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (Leicester) report on behalf of the Stargate collaboration: We observed the field of GRB 250628A detected by Swift/BAT (Ferro et al., GCN 40853) using the ESO VLT UT3 (Melipal) equipped with the X-shooter acquisition camera. A short sequence of imaging was secured in the r (3x30 s), g (3x40 s), and z (3x60 s) bands. No afterglow is detected within the Swift/XRT enhanced error region (Evans et al., GCN 40854). From preliminary analysis, we measure the following 3sigma upper limits, calibrated against nearby stars from the Legacy Survey (DR9): g > 23.7 (AB) on Jun 28 at 08:51:48 UT (7.93 hr after the GRB trigger), r > 23.6 (AB) on Jun 28 at 08:45:04 UT (7.82 hr after the GRB trigger), z > 22.8 (AB) on Jun 28 at 08:48:21 UT (7.87 hr after the GRB trigger). We note the detection of significant excess absorption in the X-ray spectrum (Evans, GCN 40857; https://www.swift.ac.uk/xrt_spectra/01328546/). This argues against a high-redshift origin for GRB 250628A and likely indicates some dust extinction. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Boris Häußler. View this GCN Circular online at https://gcn.nasa.gov/circulars/40859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0LW...