TITLE:   GCN CIRCULAR
NUMBER:  25731
SUBJECT: LIGO/Virgo S190910h: AT2019pxi, AT2019pxj and AT2019pxn 10.4m GTC spectroscopy
DATE:    19/09/12 04:21:13 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 R. Scarpa (GRANTECAN, IAC, ULL), on behalf of a 
larger collaboration, report:

Following the detection of AT2019pxi/ZTF19abyheza, 
AT2019pxj/ZTF19abyhhml and AT2019pxn/ZTF19abyjfiw (Stein et al., GCN 
25727) within the error area of the GW event S190910h (LVC, GCNC 25707), 
we obtained imaging and optical spectra covering the range 3700-7500 A 
with the 10.4m GTC telescope equipped with OSIRIS in La Palma (Spain) 
starting on Sep 11, 22:30 UT.

For AT2019pxi/ZTF19abyheza a magnitude r = 18.74+/-0.05 on Sep 11, 22:34 
UT is derived, significantly brighter than the one given in the 
PanSTARRS DR2 catalog (r = 22.26+/-0.01). The spectrum shows H-alpha in 
emission and H-beta in absorption, at redshift z = 0.

For AT2019pxj/ZTF19abyhhml a magnitude r = 19.26+/-0.04 on Sep 11, 22:52 
UT is derived, compared to r = 20.67 +/- 0.01 (PanSTARRS DR2). The 
spectrum shows emissions lines of He II 4686, several He I and a 
double-peaked component H-alpha line, consistent with the cataclismic 
variable in our Galaxy.

For AT2019pxn/ZTF19abyjfiw a magnitude r = 21.36+/-0.07 on Sep 12, 00:32 
UT is derived. The spectrum shows a featureless blue continuum.

Therefore we consider that two of the reported optical transients 
(AT2019pxi and AT2019pxj) lie in the Milky Way and therefore are 
unrelated to the GW event S190910h. No conclusion can be given for 
AT2019pxn.