IUE observations of the pre-main-sequence stars. I. Mg II and Ca II resonance line fluxes for T Tauri stars

Journal Article · Tue Dec 01 04:00:00 EST 1981 · Astrophys. J.; (United States)

DOI:https://doi.org/10.1086/159445· OSTI ID:5427106

Giampapa, M S; Calvet, N; Imhoff, C L; Kuhi, L V

We present absolute flux measurements of the Mg II and Ca II resonance lines in a sample of T Tauri stars, obtained with the International Ultraviolet Explorer satellite and the image tube scanner of the 3 m Lick reflector. We discuss the Mg II h and k line emission and the Ca II H and K line emission within the context of stellar chromospheres, and we present the corroborative evidence for the chromospheric origin of these particular resonance lines in the T Tauri stars. We derive chromospheric radiative loss rates in the Mg II and Ca II resonance lines. We find that the degree of nonradiative heating present in the outer atmospheres of the T Tauri stars generally exceeds that of the RS CVn systems, as well as the dMe stars and other active chromosphere dwarfs. We infer that the surfaces of these pre--main-sequence stars are extensively covered by regions similar to solar plages, and we estimate the relative filling factors of these active (plage) regions. We find the the chromospheric mass estimate the relative filling factors of these active (plage) regions. We find tha the chromospheric mass column density at the temperature minimum in T Tauri stars is typically an order of magnitude greater than that of the average quiet Sun, while the mean chromospheric electron density is characterized by n/sub e/ roughly-equal10/sup 11/ cm/sup -3/. We also briefly consider the relative importance of mass loss to the energy balance in the outer atmospheres of T Tauri stars by comparing the net chromospheric and coronal radiative loss rates to the stellar wind flux in the specific case of the pre--main-sequence star T Tau.

• Research Organization: Center for Astrophysics, Harvard College Observatory and Smithsonian Astrophysical Observatory
• OSTI ID: 5427106
• Journal Information: Astrophys. J.; (United States), Journal Name: Astrophys. J.; (United States) Vol. 251:1; ISSN ASJOA
• 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
ATMOSPHERES
CALCIUM IONS
CHARGED PARTICLES
EMISSION
ERUPTIVE VARIABLE STARS
IONS
MAGNESIUM IONS
MATHEMATICAL MODELS
RADIATION FLUX
SPECTRA
STAR MODELS
STARS
STELLAR ATMOSPHERES
STELLAR WINDS
T TAURI STARS
ULTRAVIOLET SPECTRA
VARIABLE STARS