High Dispersion Absorption-line Spectroscopy of AE Aqr
release_ztzkouzphfckhcvzglfao5sdx4
by
J. Echevarria, S. Zharikov,
2008
Abstract
High-dispersion time-resolved spectroscopy of the unique magnetic cataclysmic
variable AE Aqr is presented. A radial velocity analysis of the absorption
lines yields K_2 = 168.7+/- 1 km/s. Substantial deviations of the radial
velocity curve from a sinusoid are interpreted in terms of intensity variations
over the secondary star's surface. A complex rotational velocity curve as a
function of orbital phase is detected which has a modulation frequency of twice
the orbital frequency, leading to an estimate of the binary inclination angle
that is close to 70^o. The minimum and maximum rotational velocities are used
to indirectly derive a mass ratio of q= 0.6 and a radial velocity
semi-amplitude of the white dwarf of K_1 = 101+/-3 km/s. We present an
atmospheric temperature indicator, based on the absorption line ratio of Fe I
and Cr I lines, whose variation indicates that the secondary star varies from
K0 to K4 as a function of orbital phase. The ephemeris of the system has been
revised, using more than one thousand radial velocity measurements, published
over nearly five decades. From the derived radial velocity semi-amplitudes and
the estimated inclination angle, we calculate that the masses of the stars are
M_1 = 0.63+/-0.05M_sun; M_2 = 0.37+/-0.04 M_sun, and their separation is a =
2.33+/-0.02R_sun. Our analysis indicates the presence of a late-type star whose
radius is larger, by a factor of nearly two, than the radius of a normal main
sequence star of its mass. Finally we discuss the possibility that the measured
variations in the rotational velocity, temperature, and spectral type of the
secondary star as functions of orbital phase may, like the radial velocity
variations, be attributable to regions of enhanced absorption on the star's
surface.
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