In this paper we present the first two-component, semi-empirical chromospheric model of the RS CVn binary system V 711 Tau based on detailed fits of Ha and Mg II h line profiles. Synthetic H alpha and ME LT h line profiles are computed by means of NLTE radiative transfer calculations. Using the observed Emission Measure distribution to constrain the transition region structure and the photospheric Next-Generation model with log(g)=3.5 and T-eff =4800 K, we have built a grid of chromospheric models for the K1 IV component of the binary system by means of spline interpolations between photospheric and transition region models. With such interpolations the free parameters are restricted to the temperature minimum and the position of an interpolation knot. We find that a mean single component model cannot satisfactorily reproduce the observed line profiles. Chromospheric Doppler Imaging is then used to consider the chromospheric emission as due to two different components of known surface coverage and emission. Extensive grids of semi-empirical chromospheric models are built separately for the two components and the weighted-combined synthetic H alpha and Mg II it profiles are compared with observations. Two-component synthetic line profiles reproduce the observed H alpha and Mg II h in detail, indicating that the broad and narrow components can be interpreted in terms of radiative transfer effects in different atmospheric structures for the active and quiet regions. From this analysis we infer information on physical properties of the active region, from which the broad component originates, with respect to the remaining chromosphere from which the narrow component originates. We show also that the variability outside flares can be reproduced considering slightly different models for the active region.
|Titolo:||Chromospheric two-component NLTE modelling of the binary system V 711 Tau = HR 1099|
|Data di pubblicazione:||2000|
|Appare nelle tipologie:||1.1 Articolo in rivista|