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Giampapa, M. S.

Publications and source records attributed to Giampapa, M. S..

23 records · Page 2
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NASA NTRS1981

Second Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, volume 1

Solar and stellar atmospheric phenomena and their fundamental physical properties such as gravity, effective temperature and rotation rate, which provides the range in parameter space required to test various theoretical models were investigated. The similarity between solar activity and stellar activity is documented. Some of the topics discussed are: atmospheric structure, magnetic fields, solar and stellar activity, and evolution.

Giampapa, M. S.↗
NASA NTRS1981

A heating mechanism for the chromospheres of M dwarf stars

The atmospheric structure of the dwarf M-stars which is especially important to the general field of stellar chromospheres and coronae was investigated. The M-dwarf stars constitute a class of objects for which the discrepancy between the predictions of the acoustic wave chromospheric/coronal heating hypothesis and the observations is most vivid. It is assumed that they represent a class of stars where alternative atmospheric heating mechanisms, presumably magnetically related, are most clearly manifested. Ascertainment of the validity of a hypothesis to account for the origin of the chromospheric and transition region line emission in M-dwarf stars is proposed.

Giampapa, M. S.↗
NASA NTRS1980

The ultraviolet spectrum of the T Tauri star RW Aurigae

Ultraviolet spectra of the T Tauri star RW Aurigae have been obtained with the International Ultraviolet Explorer. Emission lines include Mg II, Fe II, Cr II, Si I, Si II, Si III, Si IV, C II, C IV, and L alpha. The spectrum roughly resembles the solar chromospheric spectrum, but the surface fluxes are 200 times greater. N V and He II appear to be absent, a possible indication of either an extended chromosphere cooled by mass loss or an optically thick, hot shocked region. The ultraviolet excess in RW Aur is strong, consistent with Balmer continuum emission. The observed continuum may be used to set limits on the type and amount of extinction affecting the star.

Imhoff, C. L.↗
NASA NTRS1980

Emission measures derived from far ultraviolet spectra of T Tauri stars

Spectroscopic diagnostics based on UV emission line observations have been developed to study the solar chromosphere, transition region, and corona. The atmospheric properties that can be inferred from observations of total line intensities include the temperature, by identifying the ionic species present; the temperature distribution of the emission measure, from the absolute intensities; and the electron density of the source, from line intensity ratios sensitive to the electron density. In the present paper, the temperature distribution of the emission measure is estimated from observations of far UV emission line fluxes of the T Tauri stars, RW Aurigae and RU Lupi, made on the IUE. A crude estimate of the electron density of one star is obtained, using density-sensitive line ratios.

Cram, L. E.↗