Issue |
Astron. Astrophys. Suppl. Ser.
Volume 120, Number 2, December I 1996
|
|
---|---|---|
Page(s) | 229 - 256 | |
DOI | https://doi.org/10.1051/aas:1996286 | |
Published online | 15 December 1996 |
H
emission in pre-main sequence stars.
I. An atlas of line profiles*
1
European Southern Observatory, Casilla 19001, Santiago 19, Chile
2
Centro de Astrofísica da Universidade do Porto, Rua do Campo Alegre 823, 4150 Porto, Portugal
3
Grupo da Matemática Aplicada, Universidade do Porto, Rua das Taipas 135, 4050 Porto, Portugal
Corresponding author: Send offprint request to: Bo Reipurth, e-mail: reipurth@eso.org
Received:
21
February
1996
Accepted:
16
April
1996
We present an atlas of very high resolution (R ~ 50000) Hα
line profiles of 63 pre-main sequence stars, divided among 43 T Tauri
stars, 18 Herbig Ae/Be stars, and 2 FU Orionis objects. Hα
emission is the most common and prominent spectroscopic feature of
pre-main sequence stars, and although it is optically very thick it is
still the most frequently modelled emission line in young stars. In
T Tauri stars the principal models involve magnetically driven winds,
and more recently the role of infalling magnetospheric material has
been explored. For Herbig Ae/Be stars a variety of models have been
proposed, current emphasis is directed towards obscuration by clumpy
circumstellar disk structures. In order to provide constraints on such
models, we have made a statistical analysis of the 63 high resolution
profiles. We here ignore the considerable variability of the Hα
emission, which is discussed in detail in a second paper. Most of our
observed lines show complex profiles due to an interplay between
emission and absorption features, and we suggest a two-dimensional
classification scheme to describe these line profiles, based on the
relative height of a secondary peak to the primary peak, as well as
whether the absorption is blue- or red-shifted. Among T Tauri stars,
25% have symmetric profiles, 49% have blueshifted absorption dips,
and 5% have P Cygni profiles; the remaining 21% show a variety of
redshifted absorptions. For Herbig Ae/Be stars symmetric lines are
quite rare (11%), indeed almost all of these stars have deep and
prominent central absorptions. We have measured the extent of the line
wings for all of our stars at the Imax/40 level, and find that
almost all have very extended wings, with typical extents of ±350
km/s, but in high spectra the wings can be traced to lower
intensities, and velocities as high as ±900 km/s have been
observed. Pronounced asymmetries of these extended wings are found for
many stars, suggesting the possibility that the highest velocity
material could be non-uniformly distributed. The equivalent widths of
the Hα emission in our sample of stars span two orders of
magnitude, with a distribution that increases with decreasing
equivalent width.
Key words: line: profiles / atlases / circumstellar matter / stars: emission-line / stars: pre-main sequence
© European Southern Observatory (ESO), 1996