Far-UV Continuum as a Diagnostic for Temperature Structure in
the Atmospheres of G-type Stars
C. Morossi, M. Franchini, M.L. Malagnini, & M. A. Chavez
Institute: INAF - Osservatorio Astronomico di Trieste
Institute: Universita degli Studi di Trieste, Dipartimento
di Astronomia
Institute: Instituto National de Astrofisica Optica y Electronica
(I NAOE)
Contact Email: morossi@ts.astro.it
Abstract:
Investigations of IUE ultraviolet spectra of field G and K-type stars
(Morossi et al. 1993, Morossi et al. 1998, Franchini et al. 1998a) showed
that the spectra l energy distributions (SED's) of cool stars present a
significant excess in the UV with respect to the fluxes predicted by the
atmosphere models characterized by a monotonic decrease of temperature.
We combine HST, IUE and visual observations to construct accurate SED's
to be used for deriving empirical estimate of the temperature distribution
in the atmosphere of G-type stars. Template objects are used to compare
pure LTE model predictions with those from semi-empirical structures
designed for the solar case (Vernazza et al. 1981). Particular attention
is devoted to the determination of the position of the temperature minimum
layer by computing ``semi-empirical T_min models'' (Morossi et al. 1993
and Franchini et al. 1998b).
Index Keywords: HD 131156 ; Stellar atmosphere ; Far-UV ; Temperature Structure
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Manuscript submitted: 2001-Sep-3
"The Future of Cool-Star Astrophysics", 2003, Eds. A. Brown,
G. M. Harper, & T. R. Ayres.
Proceedings of 12th Cambridge Workshop on Cool Stars, Stellar Systems,
& The Sun,
© 2003 University of Colorado.