Computer Science
Scientific paper
Jul 1984
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984iue..prop.1836l&link_type=abstract
IUE Proposal ID #CCGJL
Computer Science
Scientific paper
Observational evidence indicates that Ca II emission, and thus perhaps all chromospheric indicators, are inversely correlated with the dust/gas ratio in luminous M stars. We propose to study the differences in chromospheric activity in a sample of cool stars with a range of dust/gas properties using the unique ultraviolet chromospheric diagnostics available to IUE. A combination of archival and new, seventh year LWR-LO observations will allow us to investigate in detail the relationships between total chromospheric activity, as indicated by lines of C II, Fe II, Mg I, and Mg II, and the dust level in the outer regions of a star. Specifically, we shall determine 1) whether the inverse Ca II-dust/gas correlation can be generalized to an inverse correlation of general chromospheric activity and dust-gas ratio, 2) whether the strength of the emission in any of the uv features correlates with the dust/gas ratio, and 3) whether the fraction of the total chromospheric flux emitted in the various lines (and thus the relative radiative cooling rates) changes with varying dust/gas ratio. In contrast to chromospheric emission lines visible from the ground, the lines visible with IUE are intrinsically strong and formed at a variety of temperatures and opacities, and thus heights in the chromosphere. Thus, these IUE data, unlike the existing ground-based data, will allow us to draw conclusions regarding the interaction between dust grains and the amount of warm chromospheric gas at various levels throughout the chromospheres of cool, luminous stars. Since the lifetime of the IUE spacecraft is limited, it is important to complete this important survey program in the near future in order to guide planning for Space Telescope observations of luminous cool stars and to provide a firm observational basis for understanding the energy balance in the atmospheres of these stars.
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