GCN Circular 25903
Subject
LIGO/Virgo S190923y: optical spectrum of MASTER detected transient
Event
Date
2019-10-01T17:48:12Z (6 years ago)
From
Marina Orio at INAF-Padova and U of Wisconsin <orio@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.