V. Nascimbeni, I. Salmaso, L. Tomasella, S. Benetti (INAF Padova), P. D���Avanzo (INAF Brera), E. Cappellaro (INAF Padova), E. Brocato (INAF Teramo), on behalf of GRAWITA report:
Under the Asiago Transient Classification Program (Tomasella et al. 2014, AN, 335, 841), we observed the candidate transient found by MASTER-IAC auto-detection system (Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L), announced in Atel # 13076 and GCN 25649, which is localized in the region of the gravitational wave trigger S190901ap (LVC et al. GCN 25606, GCN 25614).
The optical spectrum was obtained with the Copernico 1.82m telescope equipped with Afosc spectrograph and grism #4 (wavelength range ~ 340-820 nm, resolution 1.4 nm). The best match is with Type Ia-91T like SNe about one week before maximum light. The redshift, as derived from SNID (Blondin and Tonry 2007, ApJ, 666, 1024), is z = 0.024, linking the transient to the host galaxy MCG+05-41-001 (z = 0.023 derived from the galaxy spectrum in SDSS, DR10). The transient is thus unrelated to the GW trigger S190901ap.