TITLE: GCN CIRCULAR NUMBER: 26591 SUBJECT: LIGO/Virgo S191213g: AT2019wxt 10.4m GTC further spectroscopy DATE: 19/12/26 09:37:08 GMT FROM: Alberto J. Castro-Tirado at IAA-CSIC A. F. Valeev (SAO-RAS), A. J. Castro-Tirado, Y.-D. Hu and E. Fernandez-Garcia (IAA-CSIC), V. Sokolov (SAO-RAS), I. Carrasco and A. Castellon (UMA), S. B. Pandey (ARIES) and N. Castro-Rodriguez (GRANTECAN, IAC, ULL), on behalf of a larger collaboration, report: McBrien et al. (GCN 26485) reported the intrinsically faint optical transient PS19hgw (AT2019wxt) in the 80% probability contour of the compact binary merger event S191213g (LVC, GCN 26402) and spectroscopic observations were conducted by Izzo et al. (GCN 26491), Srivastav and Smartt (GCN 26493), Muller Bravo et al. (GCN 26494), Vogl et al. (GCN 26504), Dutta et al. (GCN 26490), Vallely et al. (GCN 26508 ) and Becerra-Gonzalez et al (GCN 26521). We performed a first epoch of spectroscopic observations on Dec 18, 21 UT with the 10.4m GTC telescope (+ OSIRIS) in La Palma (Spain) covering the range 3,700-10,000 A showing a blue continuum with broad shallow He I lines. Following the report by Hubber et al. of a rapid optical decay (GCNC 26577) a second epoch spectrum was obtained on Dec 24, 20 UT with GTC and the same set-up. The 2nd epoch spectrum shows broad features at ~4,500 A and ~5,900A (rest frame) resembling pretty much those of the SN2011fu (a type IIb SN) at about 25 days. Therefore, it seems certain the classification of AT2019wxt as a type IIb SN. See http://jet.sao.ru/~azamat/GW/PS19hgw2019-12-24T19:50.jpeg . This work can be quoted.