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Environments of Active Close Binaries II: GK
Hydrae and TY Pyxidis
A.G. Gunn, J.G. Doyle and E.R. Houdebine
A&A, in press
High­resolution spectroscopic observations were obtained for two eclipsing active
close binary systems, GK Hydrae and TY Pyxidis. For GK Hya excess emis­
sion was observed in the Balmer lines and Mg I b lines while TY Pyx showed
excess emission in the Balmer lines and Ca II H & K lines. The emission from
GK Hya arises from a global phenomenon associated solely with the secondary
component. The lack of significant He I D 3 excess absorption and an analy­
sis of the flux ratio in the Balmer lines suggest that the emission originates in
prominence­like material seen off the limb of the star. A marginal broad excess
absorption band centered around the Balmer emission peaks may be caused by
this material absorbing the stellar continuum against the disk with high (350
km s \Gamma1 ) line­of­sight turbulent velocities. The inference that plage­like regions
and associated star­spots are not substantial on this star is in agreement with
the lack of spot modulation in the photometric light curve. For TY Pyx the
majority of the Hfi excess and a larger proportion of the Ca II core emission
could be attributed to a global phenomenon on the primary. Analysis suggests
that very large volumes are responsible for the emission, however, there is no
observational evidence for the existence of discrete extended structures around
TY Prx.
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