When the disc’s away, the stars will play: dynamical masses in the nova-like variable KR Aur with a pinch of accretion. (arXiv:2002.10193v1 [astro-ph.SR])
<a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_Gil_P/0/1/0/all/0/1">P. Rodríguez-Gil</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Shahbaz_T/0/1/0/all/0/1">T. Shahbaz</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Torres_M/0/1/0/all/0/1">M. A. P. Torres</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gansicke_B/0/1/0/all/0/1">B. T. Gänsicke</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Izquierdo_P/0/1/0/all/0/1">P. Izquierdo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Toloza_O/0/1/0/all/0/1">O. Toloza</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Alvarez_Hernandez_A/0/1/0/all/0/1">A. Álvarez-Hernández</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Steeghs_D/0/1/0/all/0/1">D. Steeghs</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Spaandonk_L/0/1/0/all/0/1">L. van Spaandonk</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Koester_D/0/1/0/all/0/1">D. Koester</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rodriguez_D/0/1/0/all/0/1">D. Rodríguez</a>
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 $log (mathrm{He/H})=
-0.79^{+0.07}_{-0.08}~~$ 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 $M_1 = 0.94^{+0.15}_{-0.11}~$
$M_odot$ 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 $47^{+1^{rm
o}}_{-2^{rm o}}$. 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.
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 $log (mathrm{He/H})=
-0.79^{+0.07}_{-0.08}~~$ 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 $M_1 = 0.94^{+0.15}_{-0.11}~$
$M_odot$ 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 $47^{+1^{rm
o}}_{-2^{rm o}}$. 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.
http://arxiv.org/icons/sfx.gif
