GCN Circular 25639
Kevin Burdge (Caltech), Daniel A. Perley (LJMU) and Mansi M. Kasliwal (Caltech) report on behalf of the GROWTH collaboration: We obtained a Keck I LRIS spectrum of ZTF19abvizsw (Kool et al. GCN 25616). The reduced spectrum shows a featureless continuum superimposed with a number of narrow absorption lines, including Mg II, Mg I, and Fe II at a consistent redshift of z=1.26. This is far beyond the GW distance constraints on S190901ap (LVC et al. GCN 25614, GCN 25606) and demonstrates that this source is unrelated to the LIGO/Virgo source. It could be a flaring AGN or blazar, but there is no counterpart in PS1 or WISE and only a dim, marginal object at this location in the Legacy Survey. It may also be a GRB afterglow. Our conclusions disagree with those of Salmaso et al. (GCN 25618), who reported an M- or K-dwarf spectrum for this object. We note that there is a bright, red star less than 2 arcsec away from the transient position and it is possible that the spectrum reported in GCN 25618 may correspond to that object.