Chromospheres of metal-deficient field giants

Journal Article · Sun Apr 01 04:00:00 EDT 1990 · Astrophysical Journal; (USA)

DOI:https://doi.org/10.1086/168652· OSTI ID:6770499

Dupree, A K; Hartmann, L; Smith, G H ^[1]

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1. Harvard-Smithsonian Center for Astrophysics, Cambridge, MA (USA) Mount Stromlo and Siding Spring Observatories, Canberra (Australia)

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. 94 refs.

• OSTI ID: 6770499
• Journal Information: Astrophysical Journal; (USA), Journal Name: Astrophysical Journal; (USA) Vol. 353; ISSN ASJOA; ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

640102* -- Astrophysics & Cosmology-- Stars & Quasi-Stellar
Radio & X-Ray Sources
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ABUNDANCE
AGE ESTIMATION
ATMOSPHERES
CHEMICAL COMPOSITION
ELEMENT ABUNDANCE
ENERGY LOSSES
GIANT STARS
HEATING
LOSSES
MASS TRANSFER
RESOLUTION
SPECTRA
STARS
STELLAR ATMOSPHERES
STELLAR CHROMOSPHERES
ULTRAVIOLET SPECTRA