TITLE:   GCN CIRCULAR
NUMBER:  24092
SUBJECT: LIGO/Virgo S190408an: MASTER OT J231043.63+470956.4 BOOTES-4 and 10.4m GTC follow-up observations
DATE:    19/04/10 14:16:47 GMT
FROM:    Alberto J. Castro-Tirado at IAA-CSIC  <ajct@iaa.es>

A. F. Valeev, I. V. Sokolov and V. V. Sokolov (SAO-RAS), Y.-D. Hu, X.-Y. 
Li and A. J. Castro-Tirado (IAA-CSIC), I. Carrasco (UMA), R. 
Sanchez-Ramirez (INAF-IAPS), M. D. Caballero-Garcia (ASU-CAS) and P. 
Pessev (GRANTECAN, IAC, ULL), on behalf  of a larger collaboration, report:

Following the new optical transient MASTER OT J231043.63+470956.4 
(Lipunov et al. GCNC 24084) within the LIGO/Virgo error box (GCNC 
24069), we have followed it up with the BOOTES-4/MET 0.6m robotic 
telescope in Lijiang (China) confirming its brightness (r = 15.3 mag on 
Apr 9, 21UT). Furthermore, we have taken a 300s spectrum with the 10.4m 
GTC (+OSIRIS) telescope in La Palma (Spain). The spectrum shows a blue 
continuum with Balmer lines in absorption with the exception of H-alpha 
in emission, all at zero redshift. This is consistent with a dwarf nova 
spectrum undergoing a superoutburst, taking into account the > 7 mag 
amplitude in optical brightness with respect to the quiescence phase. 
Therefore this OT is unrelated to S190408an, in agreement with the Onori 
et al. findings (GCNC 24090).

We acknowledge the excellent support from the GTC staff.

[GCN OPS NOTE(11apr19): Per author's request, the following typos were corrected:
" Peseev" --> "Pessev"; "taking accound the" --> "taking into account".]