TITLE:
EG And: H_alpha orbital variations from optical spectroscopy

AUTHOR:
Natalia Shagatova

ABSTRACT:
EG And is a quiet symbiotic system consisting of a white dwarf 
accretor ionizing a fraction of the neutral wind from a red giant 
donor star. The existence of the corresponding ionized and neutral 
region and a high inclination of the system (~80°) leads to the 
variable flux in H_alpha-line with orbital phase, as measured by 
an observer.

We use the optical spectra obtained at 60cm telescope of Stará Lesná 
Observatory and at 1.3m telescope of Skalnaté Pleso observatory, and 
those available at Astronomical Ring for Access to Spectroscopy Data 
Base to model the H_alpha line by three Gaussian components corresponding 
to the core emission, emission in the wings and absorption.
We determine variations of their fluxes and radial velocities as a function 
of the orbital phase. In this way, we probe physical properties of ionized 
and neutral wind regions in the binary.
The resulting core emission flux is highest at orbital phase ~0.4 and lowest 
at ~0.2. This suggests asymmetric density distribution of the circumstellar 
matter at the orbital plane with respect to the binary axis. Furthermore, 
the core emission has the secondary maximum of flux at orbital phase ~0.1. 
The strongest absorption in the H_alpha line at orbital phases near inferior 
conjuction of the white dwarf (~0.4) suggests that a fraction of the ionized 
region is optically thick in the H_alpha line.