TITLE:   GCN CIRCULAR
NUMBER:  26421
SUBJECT: LIGO/Virgo S191205ah: AT2019wkv, AT2019wid and AT2019wiy 10.4m GTC spectroscopy
DATE:    19/12/14 09:07:28 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

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

Following the detection of AT2019wkv/ZTF19acxpnvd, 
AT2019wid/ZTF19acxoyra and AT2019wiy/ZTF19acxpwlh (Andreoni et al. GCNC 
26416) within the error area of the GW event S191205ah (LVC, GCNC 
26350), 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 14, 4:34 UT. It is found those three transients are all 
SN Ia. Details follow:

For AT2019wkv/ZTF19acxpnvd, a magnitude r'= 19.13 +/- 0.04 at 05:43 UT 
is derived. Cross-correlating the transient spectrum (broad lines) with 
supernova template spectra in SNID (Blondin & Tonry, 2007), we find a 
good match to the spectra of SN Ia at redshift z = 0.083 +/- 0.003, 
consistent with the redshift of the host galaxy derived from the 
emission lines (z = 0.0849 +/- 0.0005).

For AT2019wid/ZTF19acxoyra, a magnitude r'= 18.61 +/- 0.04 at 05:07 UT 
is derived. The GTC spectrum is consistent with a SN Ia 5 days before 
maximum at z =  0.109 +/- 0.003, consistent with the redshift of the 
host galaxy derived from the emission lines (z = 0.0993 +/- 0.0007).

For AT2019wiy/ZTF19acxpwlh, a magnitude r'= 19.51 +/- 0.04 on 06:34 UT 
is derived. The GTC spectrum is consistent with a SN Ia after maximum at 
redshift z = 0.136 +/- 0.004, consistent with the redshift of the host 
galaxy derived from the emission lines (z = 0.1350 +/- 0.0005).

Therefore we consider that AT2019wkv/ZTF19acxpnvd, 
AT2019wid/ZTF19acxoyra and AT2019wiy/ZTF19acxpwlh are unrelated to the 
S191205ah GW alert.