Detalles de publicación
PP 020042
When the disc's away, the stars will play: dynamical masses in the nova-like variable KR Aur with a pinch of accretion
(1) IAC, (2) ULL, (3) SRON, (4) Univ. Warwick, (5) Mollerlyceum, Bergen op Zoom, NL, (6) Univ. Kiel, (7) Observatorio Guadarrama
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 +/- 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 T1=27148 +/- 496 K, log g=8.90 +/- 0.07, and log (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 M1 = 0.94 (+0.15 -0.11) Msun and M2 = 0.37 (+0.07 -0.07) Msun for the white dwarf and the M-dwarf, respectively, and an orbital inclination of 47 (+1º -2º). 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 ~= 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.

