A. J. Castro-Tirado, Y.-D. Hu (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) and G.
Lombardi (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report:
Following the detection of AT2020ciz/ZTF20aamvnat, 2020cjf/ZTF20aamvodd
and AT2020cjb/ZTF20aamvnth (Kasliwal et al. GCNC 27051) 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) starting on Feb 13, 20:08 UT.
For AT2020ciz/ZTF20aamvnat, a magnitude r'= 19.08 +/- 0.03 at 21:11 UT
is derived. The GTC spectrum shows double-peaked emission
lines**(H-alpha, H-beta, H-gamma, He I 5876, He II 4686) at z = 0, all
consistent with a cataclysmic variable in our Galaxy.
For AT2020cjb/ZTF20aamvnth, a magnitude r'= 20.33 +/- 0.03 at 20:13 UT
is derived. The GTC spectrum is consistent with a SN IIp (about 6 days
after the maximum) at z = 0.0612 +/- 0.0005.
For 2020cjf/ZTF20aamvodd, a magnitude r'= 24.5 + /- 0.3 at 22:42 UT is
derived, implying a decay in brightness of about 4.5 mag when comparing
to the reported ZTF value 18 h earlier (GCNC 27051). The low S/N ratio
GTC spectrum shows a H-alpha emission line at z=0 superimposed on a red
continuum starting from ~6000 A. We conclude that this object is a red
dwarf in our Galaxy.
Therefore we consider that AT2020ciz/ZTF20aamvnat,
AT2020cjb/ZTF20aamvnth and 2020cjf/ZTF20aamvodd are unrelated to the
S200213t GW alert.