When the disc's away, the stars will play: dynamical masses in the nova-like variable KR Aur with a pinch of accretion

Abstract

We obtained time-resolved optical photometry and spectroscopy of the nova-like variable KR Aurigae in the low state. The spectrum reveals a DAB white dwarf and a mid-M dwarf companion. Using the companion star's $i$-band ellipsoidal modulation we refine the binary orbital period to be $P=3.906519\pm 0.000001$ h. The light curve and the spectra show flaring activity due to episodic accretion. One of these events produced brightness oscillations at a period of 27.4 min, that we suggest to be related with the rotation period of a possibly magnetic white dwarf at either 27.4 or 54.8 min. Spectral modelling provided a spectral type of M4-5 for the companion star and $T_1=27148\pm 496$ K, $\log g=8.90\pm 0.07$, and $\log (He/H)=-0.79_{-0.08}^{+0.07}$ for the white dwarf. By simultaneously fitting absorption- and emission-line radial velocity curves and the ellipsoidal light curve, we determined the stellar masses to be $M_1=0.94_{-0.11}^{+0.15}$ $M_{\odot }$ and $M_2=0.37_{-0.07}^{+0.07}$ $M_{\odot }$ for the white dwarf and the M-dwarf, respectively, and an orbital inclination of $47_{-2^{\mathrm{o}}}^{+1^{\mathrm{o}}}$. Finally, we analyse time-resolved spectroscopy acquired when the system was at an $i$-band magnitude of 17.1, about 1.3 mag brighter than it was in the low state. In this intermediate state the line profiles contain an emission S-wave delayed by $\simeq 0.2$ orbital cycle relative to the motion of the white dwarf, similar to what is observed in SW Sextantis stars in the high state.

arXiv comment18 pages, 17 figures, 6 tables, accepted for publication in MNRAS (2020 Feb 19)

References in corpus (33)

• emcee: The MCMC Hammer
• A new extensive library of PHOENIX stellar atmospheres and synthetic spectra
• Estimating distances from parallaxes IV: Distances to 1.33 billion stars in Gaia Data Release 2
• The NextGen Model Atmosphere grid for $3000\le \Teff \le 10000\K$
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves (Expanded Edition)
• AstroImageJ: Image Processing and Photometric Extraction for Ultra-Precise Astronomical Light Curves
• The Evolution of Cataclysmic Variables as Revealed by their Donor Stars
• Galactic Reddening in 3D from Stellar Photometry - An Improved Map
• Gaia-2MASS 3D maps of Galactic interstellar dust within 3 kpc
• The Donor Stars of Cataclysmic Variables
• An Exploration of the Paradigm for the 2-3 Hour Period Gap in Cataclysmic Variables
• SDSS unveils a population of intrinsically faint cataclysmic variables at the minimum orbital period
• Cataclysmic Variable Primary Effective Temperatures: Constraints on Binary Angular Momentum Loss
• On the evolution of ultra-massive white dwarfs
• Population Synthesis of Cataclysmic Variables: I. Inclusion of Detailed Nuclear Evolution
• Effective Temperatures of Cataclysmic Variable White Dwarfs as a Probe of their Evolution
• Statistical Properties of Quasi-Periodic Pulsations in White-Light Flares Observed With Kepler
• SW Sextantis stars: the dominant population of CVs with orbital periods between 3-4 hours
• Evolution of Cataclysmic Variables and Related Binaries Containing a White-Dwarf
• The Remote Observatories of the Southeastern Association for Research in Astronomy (SARA)
• Magnetically gated accretion in an accreting 'non-magnetic' white dwarf
• The optical light curves of XTE J2123--058: the mass of the binary components and the structure of the quiescent accretion disk
• The crowded magnetosphere of the post common envelope binary QS Virginis
• Identification of twenty-three accreting binaries in the Galactic Bulge Survey
• Properties of the redback millisecond pulsar binary 3FGL J0212.1+5320
• The spotty donor star in the X-ray transient Cen X-4
• Photometric Study of KR Aurigae during the High State in 2001
• Irradiation of the secondary star in X-ray Nova Scorpii 1994 (=GRO J1655--40)
• Roche tomography of cataclysmic variables - VIII: The irradiated and spotted dwarf nova, SS Cygni
• Roche tomography of cataclysmic variables - VI. Differential rotation of AE Aqr - Not tidally locked!
• The fight for accretion: discovery of intermittent mass transfer in BB Doradus in the low state
• Detection of superhumps in the VY Scl-type nova-like variable KR Aur
• Discovery of Halpha satellite emission in a low state of the SW Sextantis star BB Doradus

Cited by in corpus (10)

• A Catalogue of Potential Post Common Envelope Binaries
• TESS light curves of cataclysmic variables -- II: Superhumps in old novae and novalike variables
• A catalogue of 323 cataclysmic variables from LAMOST DR6
• Nova-produced Common Envelope: Source of the Non-solar Abundances and an Additional Frictional Angular Momentum Loss in Cataclysmic Variables
• Follow-up Studies of Five Cataclysmic Variable Candidates Discovered by LAMOST
• Hitting a New Low: The Unique 28 h Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)
• Tilted discs in six poorly studied cataclysmic variables
• BG Tri an example of a low inclination RW Sex-type novalike
• Search for magnetic accretion in SW Sextantis systems
• Characterising the short-orbital period X-ray transient Swift J1910.2-0546