Variable quasar behind the M31 disk
ATel #12250; P. Nedialkov (U Washington/U Sofia), B. F. Williams (U Washington), V. D. Ivanov (ESO), A. Valcheva (U Sofia)
on 29 Nov 2018; 20:25 UT
Credential Certification: Petko Nedialkov (japet@phys.uni-sofia.bg)
Subjects: Optical, Quasar
We report spectroscopic confirmation of quasar nature of Gaia DR2
369276756923364224 behind the disk of M31, located at RA(2000) =
00h45m28s.24, Dec(2000) = +41o29'43".9 and z=0.203. It is a PHAT (Williams
et al. 2014) optical counterpart of a color-selected mid-infrared
point-like source from the Spitzer catalog of Khan (2017). Four 1800s
exposures were taken with the Dual Imaging Spectrograph (DIS) on 3.5 m
telescope at APO on 2018 October 7.260 UT. Photometry from images
obtained with the 50/70cm Schmidt telescope at Rozhen NAO, Bulgaria
yields: R=18.96 +/- 0.06 (2018 October 06.812 UT) and V=19.38 +/- 0.07 (2018
October 06.850 UT).
Only 3'.17 apart, both Gaia DR2 369276756923364224 and another quasar Gaia
DR2 369288714109887744 at similar redshift z=0.215 (Dorn-Wallenstein et al.
2017) were misclassified as eclipsing binaries in M31 with similar periods
of ~80d by Vilardell et al (2006). Zwicky Transient Facility (ZTF) observations
showed that Gaia DR2 369276756923364224 had a short single outburst
lasting ~1d on August 2018, 29.453 UT (JD=2458359.95) when it was at 1.1 mag
brighter than its quiescent state (r=19.3 +/- 0.1).
This work was supported by short-term scholar Fulbright grant for the
academic year 2018-2019 by the US Department of States program number
G-1-00005 and in part, by the Bulgarian NSF grant DN18/2017.
