Astronomy and Astrophysics – Astronomy
Scientific paper
Aug 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995apj...449..341j&link_type=abstract
Astrophysical Journal v.449, p.341
Astronomy and Astrophysics
Astronomy
81
Line: Profiles, Stars: Individual Constellation Name: Su Aurigae, Stars: Pre-Main-Sequence
Scientific paper
We analyze approximately 100 echelle spectra of the T Tauri star SU Aur. The photospheric lines appear unveiled and show little variability. We find evidence for periodic intensity variations in the blue wing of Hβ between -170 < υ < -110 km s-1 from line center with a period of approximately 3 days, the rotation period of the star. Both the period and velocity are the same as previously reported for Hα in SU Aur. Furthermore, evidence for unsteady accretion is found in the presence of a variable red displaced absorption feature with a velocity of υ +100 km s-1 in Hβ. This feature is also periodic at 3 days (unlike in Hα). Several spectra indicate simultaneous mass inflow and outflow. The Ca II infrared and He 1 5876 lines show modest variability and imply that the structure of the chromosphere on SU Aur is very different than solar plage regions.
Variations of the Ca II lines and the He I line are well correlated with each other but only poorly correlated with Balmer line variability. We use spherically symmetric radiative transfer codes to calculate the line profiles for SU Aur. The equations of statistical equilibrium are solved using the general purpose program CLOUDY. By simultaneously fitting the Balmer lines in SU Aur, we determine to what extent these lines can be produced in a spherically symmetric wind and constrain the parameters of this wind. We find that large turbulent velocities are required at the base of such a wind, where the bulk of the emission is produced. The steady absorption feature seen at υ ≍ -50 km s-1 must form in the outer portions of the stellar wind, implying a terminal velocity of the wind much below the stellar escape velocity. The mass-loss rate is determined to be about 4.5 × 10-9 Msun yr-1.
Basri Gibor
Johns Christopher Michael
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