TITLE:   GCN CIRCULAR
NUMBER:  27154
SUBJECT: LIGO/Virgo S200213t: AT2020clw/ZTF20aanaoyz, AT2020crd/ZTF20aanakge and AT2020cly/ZTF20aanakes 10.4m GTC spectroscopy
DATE:    20/02/20 15:31:10 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

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

Following the detection of AT2020clw/ZTF20aanaoyz, 
AT2020crd/ZTF20aanakge and AT2020cly/ZTF20aanakes (Kasliwal et al. GCNC 
27051, Coughlin et al. GCNC 27095) within the error area of the GW event 
S200213t (LVC, GCNC 27042), we obtained optical spectra covering the 
range 3700-7400 A with the 10.4m GTC telescope equipped with OSIRIS in 
La Palma (Spain). Details follow:

For AT2020clw/ZTF20aanaoyz, a magnitude r'= 21.10 +/- 0.09 at 2020-02-15 
20:11 UT is derived. The GTC spectrum is consistent with a SN Ia (near 
maximum) at z = 0.276 +/- 0.005.

For AT2020crd/ZTF20aanakge, a magnitude r'= 19.85 +/- 0.03 at 2020-02-19 
20:42 UT is derived. The GTC spectrum is consistent with a SN Ia (near 
maximum) at z = 0.1272 +/- 0.0005.

For AT2020cly/ZTF20aanakes, no optical counterpart is detected in the 
r'-band 60s exposure image (2020-02-19 20:36UT) within the reported 
position down to 24.9 mag at three-sigma confidence level, which 
confirmed the non-detection reported by Bellm et al (GCNC 27118).

Therefore we consider that AT2020clw/ZTF20aanaoyz and 
AT2020crd/ZTF20aanakge are unrelated to the S200213t GW alert.

We thank the staff at GTC for their excellent support.