Astronomy and Astrophysics – Astrophysics
Scientific paper
Apr 1990
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1990apj...353..623d&link_type=abstract
Astrophysical Journal, Part 1 (ISSN 0004-637X), vol. 353, April 20, 1990, p. 623-635.
Astronomy and Astrophysics
Astrophysics
44
Chromosphere, Giant Stars, Iue, Metallic Stars, Stellar Mass Ejection, Ultraviolet Spectra, Energy Dissipation, High Resolution, Late Stars
Scientific paper
Observations of the 2800-A Mg II line have been obtained with IUE for a sample of 10 metal-deficient field giant stars to search for chromospheric emission and signatures of mass loss, as well as to establish the level of chromospheric radiative energy losses from these stars. Mg II emission is probably present in all stars. High-resolution spectra of three of the brightest giants show asymmetric Mg II profiles which indicate a differentially expanding atmosphere, signaling the presence of outward mass motions. Surprisingly, the stellar surface fluxes in the Mg II lines are commensurate with the values found for disk giant stars (population I) of similar color. In spite of substantially depleted Mg abundances in the target stars (by factors of 10-100 relative to the solar abundance), the radiative losses implied by the Mg II fluxes, and possibly the chromospheric heating mechanism, appear to be reasonably independent of metallicity and age.
Dupree Andrea K.
Hartmann Lee
Smith Graeme H.
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