Astronomy and Astrophysics – Astronomy
Scientific paper
Dec 1992
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1992aas...18110310s&link_type=abstract
American Astronomical Society, 181st AAS Meeting, #103.10; Bulletin of the American Astronomical Society, Vol. 24, p.1288
Astronomy and Astrophysics
Astronomy
Scientific paper
We present the results of a study of variations in the narrow emission component of the He I D3 line at 5875.68 Angstroms in T Tauri Stars of spectral types K5 to M3. 20 stars with representation from the extreme, classical, and weak subclasses of TTS were observed at up to 6 different epochs between October 1986 and January 1989. Almost all of these observations contain, to some degree, narrow (average FWHM of 38 km/s), generally symmetric He I D3 emission at rest velocity with respect to the star superimposed on a broad (average FWHM of 177 km/s), asymmetric emission component apparently slightly blueshifted with respect to the star. The goal of this study is to measure line strengths representing only chromospheric radiative losses in the D3 line in order to gain insight as to the mechanisms of He I line formation in TTS. All observations are corrected for any veiling effects of excess continuum emission. Veiling measurements for this data set already exist in the literature. We adopt these values except in cases of high uncertainty estimates or apparent discrepancies which we find for the extreme TTS in our sample. In these cases, we recalculate the veiling by fitting analytic gaussians to weak absorption lines and comparing line depths to those of appropriate photospheric templates. We make the following conclusions: 1) Gaussian fits to weak absorption lines give lower veiling values than those in the literature due to enhanced stellar activity in the TTS whose effects are generally more pronounced in stronger lines. 2) The lithium line at 6707 Angstroms is not a good indicator of continuum veiling since it shows variable strengths even after correcting for veiling. We find a correlation between Li I 6707 Angstroms line strength and veiling for RW Aur suggesting that this line is enhanced by accretion processes. 3) We find a correlation between the chromospheric radiative losses in the D3 line and veiling for veilings up to approximately 1.0 suggesting that this line as well is enhanced by accretion processes.
Basri Gibor S.
Batalha C. C.
Stout N. M.
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