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Excess Hα emission in chromospherically active binaries.
We study the behaviour of the excess Hα emission in a sample of 51chromospherically active binary systems (RS CVn and BY Dra classes), ofdifferent activity levels. This sample include the 27 stars analysed byFernandez-Figueroa et al. (1994) and the new observations of 24 systemsdescribed by Montes et al. (1994b). By using the spectral subtractiontechnique (subtraction of a synthesized stellar spectrum constructedfrom reference stars of similar spectral type and luminosity class) weobtain the active-chromosphere contribution to the Hα line inthese 51 systems. We have determined the excess Hα emissionequivalent widths and converted it to surface fluxes. The Hαemissions arising from each component star were obtained when it waspossible to deblend both contributions. The comparison of the excessHα emission, obtained with the spectral subtraction technique,with other Hα activity indices allows us to conclude that this isthe preferable activity indicator for binaries. The behaviour of theexcess Hα emission as a function of the rotation has beenanalyzed. A slight decline toward longer rotational periods, P_rot_, andlarger Rossby numbers, R_0_, is present in agreement with previousresults using others activity indicators. We have compared the derivedexcess Hα emission fluxes with those obtained in the Ca II K andHɛ lines finding that a good correlation exits between thesethree chromospheric activity indicators. The Hα losses seem to bemore important than Ca II K losses for cooler stars, in fact all thesystem with Hα emission above the continuum are cooler than 5000K.Correlations with other activity indicators, (C IV in the transitionregion, and X-rays in the corona) indicate that the exponents of thepower-law relations increase with the formation temperature of thespectral features.
| A Study of Activity in F-Type Main-Sequence Stars Using the D/3 Line of Hei
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1993A&A...273..482G&db_key=AST
| The Hertzsprung-Russell Diagram for F5-K2 Stars with the Most Accurate Absolute Magnitudes.
Abstract image available at:http://adsabs.harvard.edu/cgi-bin/nph-bib_query?1959ApJ...130..487O&db_key=AST
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