GCN Circular 25421
A. F. Valeev (SAO-RAS), Y.-D. Hu (IAA-CSIC), A. J. Castro-Tirado and E. Fernandez-Garcia (IAA-CSIC), V. V. Sokolov (SAO-RAS), I. Carrasco and A. Castellon (UMA) and J. Font Serra (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: Following the detection of ZTF19abqanpy (Stein et al., GCN 25418 ) in the error box for the subthreshold joint Fermi GBM-LVC gravitational wave trigger Fermi GBM-190816 (GCN 25406), we obtained imaging and optical spectra covering the range 3700-10000 A with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) starting on Aug 21, 03:00 UT. ZTF19abqanpy magnitude on Aug 21, 03:45 UT was measured to be i = 18.65 +/- 0.05. The ZTF19abqanpy spectrum displays broad lines and is consistent with a SN Ia at one week before maximum located at the nearby (13 arcsec to the East) host galaxy (at redshift z = 0.043 +/- 0.001, based on the narrow emission lines from the host galaxy). The projected distance from ZTF19abqanpy to the center of the galaxy is 10.9 kpc. Therefore we conclude that ZTF19abqanpy is unrelated to the above-mentioned Fermi-GW event.