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

P. Rodríguez-Gil (1,2), T. Shahbaz (1,2), M. A. P. Torres (1,2,3), B. T. Gänsicke (4), P. Izquierdo (1,2), O. Toloza (4), A. \'Alvarez-Hern\'andez (1,2), D. Steeghs (4), L. van Spaandonk (4,5), D. Koester (6), D. Rodr\'iguez (7)
(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.

 
Aceptado para publicación en MNRAS | Enviado el 2020-02-25 | Proyecto AYA2017-83383-P, AYA2017-83216-P, P/308807, P/309710