Ultraviolet and optical observations of metal deficient red giants and chromospheric models

Details Ultraviolet and optical observations of metal deficient red giants and chromospheric models Ultraviolet and optical observations of metal deficient red giants and chromospheric models

Jul 1984

adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1984esasp.218..191d&link_type=abstract

In ESA Fourth European IUE Conf. p 191-195 (SEE N84-35135 24-88)

Astronomy and Astrophysics

Astronomy

5

Chromosphere, Interstellar Chemistry, Red Giant Stars, Stellar Models, Stellar Spectra, Iue, Stellar Evolution, Stellar Mass Ejection, Stellar Spectrophotometry, Ultraviolet Astronomy

Scientific paper

Three metal deficient field stars were observed in the ultraviolet and optical spectral regions: HD 165195, HD 110281, and HD 232078. High dispersion spectra near H alpha, and low dispersion, long wavelength IUE spectra were obtained. The H alpha profiles have strong asymmetric emission with absorption cores that are frequently asymmetric. The surface flux of Mg II lines is similar to that of luminous Pop I stars in spite of the lower metal abundance. Semi-empirical atmospheric models suggest that the characteristic emission in the wings of the H alpha line can arise within static chromospheres. Radial expansion gives an asymmetric, blue-shifted H alpha core accompanied by greater emission in the red line wing than the blue wing. Wind models with extended atmospheres suggest mass loss rates - 2 billion M/yr. Thus H alpha provides no evidence that steady mass loss is substantial enough to significantly affect the evolution of stars on the red giant branch of globular clusters.

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