TITLE: GCN CIRCULAR NUMBER: 23168 SUBJECT: GRB 180821A: VLT observations DATE: 18/08/23 16:22:15 GMT FROM: Paul Vreeswijk at Radboud U/Nijmegen Paul Vreeswijk (Radboud U. Nijmegen), Daniele Malesani, Jonatan Selsing (DAWN/NBI, DARK/NBI), Nial Tanvir (U. Leicester), Giovanna Pugliese (API/U. Amsterdam), Andrea Rossi (INAF-OAS) and Andrew Levan (U. Warwick) report on behalf of the Stargate collaboration: The Swift XRT error circle (Tohuvavohu et al., GCN 23158; Burrows et al., GCN 23164) of GRB 180821A (Krimm et al., GCN 23166) was observed with the Very Large Telescope on the night of August 21/22, 2018, using the telescope/instrument combinations Kueyen/X-shooter and Antu/FORS2. The FORS2 imaging observations started at 5:58 UT on August 22 (13.3 hours after the GRB trigger) and consisted of 8 exposures of 120 seconds in the z_Gunn filter. No object is detected in the enhanced XRT error circle (Evans et al., GCN 23162), down to a 3-sigma limiting magnitude of z(AB)=24.9 (see also Fernandez-Garcia, GCN 23159; Guidorzi et al., GCN 23163; Kong, GCNs 23160 and 23165; Marshall et al., GCN 23167). The z-band coverage of this field by the SkyMapper Southern Sky Survey (see http://skymapper.anu.edu.au) was used in the determination of the magnitude limit. The X-shooter spectroscopic observations started at 6:55 UT on August 22 (14.3 hours after the GRB). A sequence of 4 spectra of 10 minutes each was taken of the object at the Southwestern edge of the preliminary XRT error circle, at coordinates R.A.: 00:31:09.0, decl.: -38:37:39.5 (J2000). The reduced spectra show emission lines typical of a star-forming galaxy, such as [OII] 3727, Hbeta, [OIII] 4959, 5007 and Halpha, at a redshift of z=0.58. Although the location of this galaxy is consistent with the initial XRT afterglow localization, it is about 6 arcseconds to the West and well outside of the enhanced XRT error circle, and is therefore unrelated to the GRB. We acknowledge the excellent assistance of the staff at Paranal observatory, and in particular that of S. Brillant, C. Ledoux, F. Gaete, E. Sedaghati and J. Velasquez.