TITLE:   GCN CIRCULAR
NUMBER:  26492
SUBJECT: LIGO/Virgo S191213g: AT2019wnh, AT2019wnk and AT2019wrt 10.4m GTC spectroscopy
DATE:    19/12/18 22:52:16 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

A. J. Castro-Tirado, Y.-D. Hu (IAA-CSIC), A. F. Valeev and V. V. Sokolov 
(SAO-RAS), E. Fernandez-Garcia (IAA-CSIC), I. Carrasco and A. Castellon 
(UMA), M. D. Caballero-Garcia (ASU-CAS) and S. Geier (GRANTECAN, IAC, 
ULL), on behalf of a larger collaboration, report:

Following the detection of AT2019wnh/ZTF19acymaru, 
AT2019wnk/ZTF19acylvus and AT2019wrt/ZTF19acyldun (Andreoni et al.,
GCNC 26424, Stein et al. GCNC 26437) within the error area of the GW 
event S191213g (LVC, GCNC 26402), we obtained optical spectra covering 
the range 3700-7400 A with the 10.4m GTC telescope equipped with OSIRIS 
in La Palma (Spain) starting on Dec 18, 01:02 UT. Details follow:

For AT2019wnh/ZTF19acymaru, a magnitude r'= 19.97 +/- 0.02 at 01:02 UT 
is derived. The GTC spectrum is consistent with a SN Ia at redshift z = 
0.167 +/- 0.005.

For AT2019wnk/ZTF19acylvus, a magnitude r'= 19.08 +/- 0.02 at 01:22 UT 
is derived. The GTC spectrum is consistent with a SN Ia at redshift z = 
0.1036 +/- 0.005.

For AT2019wrt/ZTF19acyldun (also reported by Xu et al. GCNC 26450 and 
Oates et al. GCNC 26471), a magnitude r'= 18.45 +/- 0.01 at 01:38 UT is 
derived. It is located in the arm of the host galaxy showing a blue 
continuum and Balmer emission lines at redshift z = 0.057. Hence we 
consider it is a LBV in the nearby galaxy. The detection of the object 
on archival PanStarrs images (one taken in the g-band in Aug 2012) 
confirms the variability of the transient prior to its current LBV 
eruption.

Therefore we consider that AT2019wnh/ZTF19acymaru, 
AT2019wnk/ZTF19acylvus and AT2019wrt/ZTF19acyldun are unrelated to the 
S191213g GW alert.