TITLE: GCN CIRCULAR NUMBER: 25276 SUBJECT: LIGO/Virgo S190728q: AT2019lvw 10.4m GTC spectroscopy DATE: 19/08/05 19:03:01 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC Y.-D. Hu (IAA-CSIC), A. F. Valeev and V.V. Sokolov (SAO-RAS), A. J. Castro-Tirado and E. Fernandez-Garcia (IAA-CSIC), I. Carrasco and A. Castellon (UMA) and N. Castro-Rodriguez (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of AT2019lvw (Goldstein et al., GCN 25215, Andreoni et al., GCNC 24235) within the error area of the GW event S190728q (LVC, GCNC 25187), we obtained imaging and optical spectra covering the range 3700-7500 A with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Aug 5, 04:00 UT. AT2019lvw magnitude on Aug 5, 04:30 UT was measured to be r = 22.15 +/- 0.05. The AT2019lvw 1200s spectrum displays broad lines and is consistent with a SN Ia at three-four weeks post maximum at the nearby host galaxy redshift (z = 0.270 +/- 0.001, based on the narrow emission lines from the galaxy). Therefore AT2019lvw is unrelated to the GW event S190728q.