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GCN Circular 26426

LIGO/Virgo S191213g: Liverpool Telescope spectroscopy of ZTF candidates
2019-12-14T21:56:23Z (4 years ago)
Daniel Perley at Liverpool JMU <>
D. A. Perley and C. M. Copperwheat (LJMU) report on behalf of the GROWTH 

We obtained spectroscopy of several of the reported ZTF optical 
transients (Andreoni et al., GCN 26424) inside the error region of 
S191213g (LVC, GCN 26402) using the Spectrograph for the Rapid 
Acquisition of Transients (SPRAT) on the 2m Liverpool 
Telescope.��Observations were conducted on 2019-12-14 between 19:16 and 
21:03 (UTC).  Spectral classifications were performed with Superfit 
(Howell et al. 2005).

The spectrum of ZTF19acykzsk (AT2019wqj) shows a broad emission feature 
consistent with H-alpha at the host redshift of z=0.0205. ��The overall 
spectrum is consistent with a Type II supernova close to maximum light.

The spectrum of ZTF19acymgzk (AT2019vtj) is an excellent match to a type 
Ia SN at z~0.05 close to maximum light.

The spectrum of ZTF19acykzsp (AT2019wne) has relatively low S/N, but is 
also a good match to a type Ia SN at maximum light at z~0.16. This is 
consistent with the photometric SDSS redshift of its probable host galaxy.

ZTF19acykwsd (AT2019wnl) was also observed, but no transient was visible 
at the reported ZTF position in the acquisition exposures (despite good 
observing conditions) to an upper limit of approximately r > 21.1, well 
below the reported initial detection magnitude.  It may be a 
short-timescale stellar flare, although no stellar counterpart is 
visible in the PS1 reference imaging.

We conclude that none of these transients are likely to be related to 
the gravitational-wave event.

Further observations of additional sources are ongoing.

We acknowledge helpful suggestions from Erik Kool on the GCN draft.

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