Andrej Dobrotka, Shin Mineshige, Jorge Casares
We present a study of the flickering activity in two nova like systems KR Aur
and UU Aqr. We applied a statistical model of flickering simulations in
accretion discs based on turbulent angular momentum transport between two
adjacent rings with an exponential distribution of the turbulence dimension
scale. The model is based on a steady state disc model which is satisfied in
the case of hot ionized discs of nova like cataclysmic variables. Our model
successfully fits the observed power density spectrum of KR Aur with the disc
parameter alpha = 0.10 - 0.40 and an inner disc truncation radius in the range
R_in = 0.88 - 1.67 x 10^9 cm. The exact values depend on the mass transfer rate
in the sense that alpha decreases and R_in increases with mass transfer rate.
In any case, the inner disc radius found for KR Aur is considerably smaller
than in quiescent dwarf novae, as predicted by the disc instability model. On
the other hand, our simulations fail to reproduce the power density spectrum of
UU Aqr. A tantalizing explanation involves the possible presence of spiral
waves, which are expected in UU Aqr, because of its low mass ratio, but not in
KR Aur. In general our model predicts the observed concentration of flickering
in the central disc. We explain this by the radial dependence of the angular
momentum gradient.
View original:
http://arxiv.org/abs/1111.3744
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