[vsnet-grb-info 23804] LIGO/Virgo S190923y: optical spectrum of MASTER detected transient

[GCN Circulars]

TITLE:   GCN CIRCULAR
NUMBER:  25903
SUBJECT: LIGO/Virgo S190923y: optical spectrum of MASTER detected transient
DATE:    19/10/01 17:48:12 GMT
FROM:    Marina Orio at INAF-Padova and U of Wisconsin  <orio at astro.wisc.edu>

David Buckley (South African Astronomical Observatory), Stefano Ciroi (Padova University), Marina Orio (Istituto Nazionale di Astrofisica-Padova, and University of Wisconsin), Saurabh Jah  (Rutgers University) and Joanna Mikolajewska (Nicolaus Copernicus Center of the PAS) report:

 On 2019/9/27 at UT 17:48:22 we obtained an optical spectrum of the transient source MASTER OT J162250.41-482250.3  discovered by the MASTER Global Robotic Net  in the field of the gravitational wave event S190923y (see GCN 25855) , with the Robert Stobie spectrograph on the SALT telescope and the PG 300 grating, in the 3300-9800 Angstrom range and with a 22 Angstrom spectral resolution.
 The spectrum has a blue continuum and various emission lines, of which the most prominent is H-alpha. Several other emission lines of He I and He at 4686 Angstrom are also detected, and all spectral lines do not show significant red shift. We measured the following equivalent widths:

He II 4686 Angstrom:      0.71 Angstrom
Hbeta                                 0.79  Angstrom
He I 5876  Angstrom      1.02 Angstrom
Halpha                              10.12 Angstrom
He I 6678   Angstrom     1.93 Angstrom
He I 7065   Angstrom     1.73 Angstrom

 The spectrum is consistent with a Galactic source, likely to be a cataclysmic variable or  another low mass binary in outburst. This result rules out that  this transient as the optical counterpart of the gravitational wave event.