Other
Scientific paper
Jan 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994phdt........21j&link_type=abstract
Thesis (PH.D.)--UNIVERSITY OF CALIFORNIA, BERKELEY, 1994.Source: Dissertation Abstracts International, Volume: 56-05, Section: B
Other
5
Line Profiles, Wind Flows, Accretion Flows, Balmer Lines
Scientific paper
A large sample of repeated high resolution echelle spectra of 8 T Tauri stars (TTS) are analyzed to study the variations in the peculiar spectra of these stars. Striking variability is evident on a nightly basis. Intense observing campaigns permit the search for periodic modulation of the emission line profiles in 6 of the stars. A key result is that 3 of the 6 stars show evidence for periodic behavior in some portion of their Balmer Line profiles. In one of the stars (SU Aur) there is clear evidence for modulation of the wind and accretion flows by the stellar rotation. Correlation analysis shows that the blue-shifted absorption component of the line profile visible in most of these stars varies on a longer timescale and is basically uncorrelated with the rest of the line profiles. It appears that TTS Hα profile variations are not due to global changes in the physical parameters of the wind and accretion flows surrounding these stars but instead represent smaller-scale stochastic variability. Over most of the profile the timescale for this tends to be less than two days. Detailed analysis of the C scA II infrared and He I 5876 A lines in two of the target stars show modest variability. Variations of the C scA II lines and the He I line are well correlated with each other, but only poorly correlated with Balmer line variability. The strength and behavior of these lines in SU Aur indicate that the chromosphere of this G2 star is qualitatively different than solar plage regions. A spherically symmetric radiative transfer code is used to calculate average line profiles for SU Aur and DF Tau. By simultaneously fitting the Balmer lines, the applicability of spherically symmetric winds is examined and the parameters of the winds are constrained. Large turbulent velocities appear to be required in the stellar magnetosphere, where the bulk of the emission is produced. The steady absorption feature seen on the blue side of the line profiles must form in the outer portions of the stellar wind, implying a terminal velocity of the wind much below the stellar escape velocity.
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