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Centro de Astrofísica da Universidade do Porto

Time-variability analysis of the Hα, He I and NA I D lines in the T Tauri star LkHα 264

M. T. V. T. Lago, J. F. Gameiro

Abstract
We present a time-series analysis of quasi-simultaneous high-resolution profiles of the H-alpha, He I (5876 A) and Na I D lines for the highly active T Tauri star LkH-alpha 264. Our data include repeated observations on time scales ranging from approximately 1 d down to less than 1 h, at two different epochs. For the three lines we have analyzed the time variability of the equivalent width and of the profile, using in this case both the normalized variance and correlation matrix analysis. The behaviors of the equivalent widths of the He I and Na I lines on time scales of the order of 1 d were found to correlate well. The correlation is more conspicuous when the level of variability of the lines is more dramatic. We conclude that there is a common region of formation for these lines, very close to the star. However, the H-alpha equivalent width follows such behavior only when the He I and Na I D lines are less variable. We conclude that the H-alpha line is formed in two distinct regions. The inner region, which is not too distinct from the one producing the He I and Na I D lines, is highly sensitive to the level of activity. The outer and more extended region dominates the contribution to the flux in H-alpha when the general level of stellar activity is high.

Monthly Notices of the Royal Astronomical Society
Volume 294, Page 272
February 1998

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