GCN Circular 25744
I. Pastor-Marazuela (API/ASTRON), G. Cannizzaro (SRON/Radboud Univ), P. Jonker (SRON/Radboud Univ), K. Maguire (TCD), M. Fraser (UCD) and M. Perez Torres (IAC) report on behalf of the GW@WHT collaboration: We obtained optical spectroscopy of Gaia19ebl/AT2019qba, Gaia19eba/AT2019qam and Gaia19eaz/AT2019qal (GCN 25740), three optical transients within the sky localisation of the gravitational wave trigger S190910h (GCN 25707) with the ACAM instrument mounted on the William Herschel Telescope located at the Roque de Los Muchachos Observatory, La Palma, Spain. We cross-correlate the transient spectra with a library of supernova template spectra using the code SNID (Blondin and Tonry, 2007). Gaia19ebl: the spectrum is dominated by the host-galaxy light and shows a strong Halpha emission line, from which we derive a redshift of z=0.02, corresponding to a distance of around 97 Mpc. This puts the galaxy outside the distance region (241+-89 Mpc) reported for S20190910h. No match with any template is found. Gaia19eba: SNID gives a good match with a type Ia supernova at redshift z=0.06 (253 Mpc). Gaia19eaz: SNID gives a good match with a type Ia supernova at redshift z=0.03 (127 Mpc). We therefore consider that these three transients are unrelated to the gravitational wave trigger S20190910h.