SALT optical spectrum of transient MASTER OT J162250.41-482250.3
ATel #13158; 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 Astronomical Center of the PAS)
on 2 Oct 2019; 17:50 UT
Credential Certification: Marina Orio (orio@astro.wisc.edu)
Subjects: Optical, Gravitational Waves, Transient, Variables
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 (GCN 25855), with the Robert Stobie spectrograph on the SALT telescope and the PG 300 grating, in the 3300-9800 Å range and with a 22 Å 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 II at 4686 Å are also detected, and all spectral lines do not show significant red shift. We measured the following equivalent widths:
He II at 4686 Å: 0.71 Å, Hβ: 0.79 Å, He I at 5876 Å: 1.02 Å,
Hα: 10.12 Å, He I at 6678 Å:1.93 Å, He I at 7065 Å: 1.73 Å.
As we announced in GCN 25903, this 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 is the optical counterpart of the gravitational wave event, but since it is an interesting transient in its own right, further observations are encouraged.
