Wind accretion in the symbiotic binary system RW Hya
Abstract
RW Hya is a detached eclipsing symbiotic binary system with known stellar and orbital parameters, consisting of a mass-loosing M2 giant and a white dwarf. HST spectra indicate the absence of a fast wind from the white dwarf, consequently we expect the companion to accrete material from the wind of the M giant. We have done a three-dimensional wind accretion simulation which we compare with observations. IUE and HST UV observations show that out of eclipse, for a short period of \Delta \phi=0.04 there is a reduction of the white dwarf continuum by Rayleigh and dust scattering. We interpret this effect as the signature of the accretion shock cone. Accretion models predict a shock cone with enhanced density. In this cone, we expect the formation of neutral hydrogen and dust. When the white dwarf is then viewed through this structure its radiation gets obscured. We numerically solve the 3D Euler equations with a polytropical index \gamma=1, yielding the circumstellar velocity and density structure in RW Hya. The momentum of the M giant wind which is a free parameter in the simulation, is set by the observed orbital orientation of the shock cone. Based on the theoretical circumstellar structure, we can calculate nebular emission line profiles for different viewing angles. We present a time series of observed optically thin emission lines. In these observations, we aim at separating the observed line profile into two components, one originating in the accretion shock cone, the other formed in the ionized red giant wind. In RW Hya we then get the chance to compare observations of the wind accretion region with numerical simulations.
- Publication:
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Astronomische Gesellschaft Abstract Series
- Pub Date:
- 1998
- Bibcode:
- 1998AGAb...14...34D
- Keywords:
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- Symbiotic Stars: Stellar Winds;
- Symbiotic Stars: Accretion