Study of short-period RS Canum Venaticorum and W Ursae Majoris binary systems: The global nature of H. cap alpha
I present the rotation versus emission characteristics of the H..cap alpha.. line for several short-period (P< or approx. =1/sup d/) RS CVn and W UMa binary systems. Estimates for the chromospheric emission arising from each component star were obtained by subtraction of '' nonactive'' model spectra constructed from comparison stars similar in spectral type to the component stars. Disentanglement of the emission contribution from each binary component was performed by fitting Gaussians to the subtracted profiles. Enhanced H..cap alpha.. emission compared to the nonactive comparison stars is seen on all components of the short-period RS CVn systems studied, while a similar enhancement is only typically seen on the primary components of the W-type W UMa systems. A possible correlation between L/sub Halpha//L/sub bol/ (values ranging from 3 to 16 x 10/sup -5/) and the Rossby number (the ratio between the rotational period and the convective time scale) is seen for those components showing emission. Such a correlation suggests that the H..cap alpha.. line is a good diagnostic for the study of the magnetic-related activity in late-type stellar systems. Plotting the L/sub Halpha//L/sub bol/ against a measure of the tidal amplitude of Scharlemann shows that the activity of the W UMa secondary components may be shut off by the tidal forces of the primaries. The shut-off appears in those components having a tidal amplitude > or approx. =0.02. It is, however, unclear whether the tidal damping of the differential rotation is the sole mechanism responsible for the shut-off of the H..cap alpha.. emission, as the activity damping may also be attributable to the contact nature of the W UMa systems.
- Research Organization:
- Department of Astronomy, The Pennsylvania State University
- OSTI ID:
- 5375592
- Journal Information:
- Astrophys. J.; (United States), Vol. 295:1
- Country of Publication:
- United States
- Language:
- English
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