Astronomy and Astrophysics – Astronomy
Scientific paper
Jan 1982
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1982apj...252..214h&link_type=abstract
Astrophysical Journal, Part 1, vol. 252, Jan. 1, 1982, p. 214-229.
Astronomy and Astrophysics
Astronomy
69
Chromosphere, Emission Spectra, Late Stars, Stellar Spectra, Stellar Structure, Ultraviolet Astronomy, Dwarf Stars, Hertzsprung-Russell Diagram, Iue, Line Spectra, Radiant Flux Density, Stellar Envelopes, Stellar Evolution, Stellar Gravitation, Stellar Temperature, Transition Points
Scientific paper
A survey is presented of chromospheric and transition region (TR) line emission in late-type stars obtained with the IUE satellite. A wide variation in TR emission (ions formed near T = 100,000 K) at a given position in the H-R diagram is found, contradicting theories that incorporate only acoustic energy generation and deposition. The behavior of the Hyades giants is thought to suggest that age does not uniquely determine emission levels. The data are consistent with the picture advanced by many others that rapid rotation appears to result in enhanced fluxes. Emission in TR lines is correlated with chromospheric emission; the range in observed surface fluxes from different stars increases with the temperature of line formation. It is noted that although emission measures of high temperature gas generally decline with decreasing stellar gravity, it is not possible to define a sharp division in the H-R diagram between stars with TR emitting regions and those without.
Dupree Andrea K.
Hartmann Lee
Raymond John C.
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