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 } = 27 148 \pm 496 K , \log g = 8.90 \pm 0.07 , and \log ( \mathrm { He / H } ) = -0.79 ^ { +0.07 } _ { -0.08 } 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 ^ { +0.15 } _ { -0.11 } \mbox { $ \mathrm { M } _ { \odot } $ } and M _ { 2 } = 0.37 ^ { +0.07 } _ { -0.07 } \mbox { $ \mathrm { M } _ { \odot } $ } for the white dwarf and the M-dwarf , respectively , and an orbital inclination of 47 ^ { +1 ^ { o } } _ { -2 ^ { 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 .