TITLE: GCN CIRCULAR NUMBER: 25724 SUBJECT: LIGO/Virgo S190901ap: WHT spectroscopy of Gaia19dzi DATE: 19/09/11 06:10:54 GMT FROM: Giacomo Cannizzaro at SRON G. Cannizzaro (SRON/Radboud Univ), I. Pastor-Marazuela (API/ASTRON), P. Jonker (SRON/Radboud Univ) report on behalf of the GW@WHT collaboration: We obtained optical spectroscopy of Gaia19dzi (GCN 25716), an optical transient within the LIGO/Virgo S190901ap sky localisation (GCN 25606) 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). Gaia19dzi is classified as a SNIa, with a redshift of z=0.06. [GCN OPS NOTE(11sep19): Per author's request, in the Subject-line and first sentence the "S190910ap" was changed to "S190901ap".]