Issue |
A&A
Volume 446, Number 3, February II 2006
|
|
---|---|---|
Page(s) | 1051 - 1070 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20053345 | |
Published online | 20 January 2006 |
Pulsational line profile variation of the roAp star HR 3831
Department of Astronomy and Space Physics, Uppsala University, 751 20 Uppsala, Sweden e-mail: oleg@astro.uu.se
Received:
30
April
2005
Accepted:
12
September
2005
We report the first comprehensive investigation of the line profile variation caused by
non-radial pulsation in an oscillating magnetic chemically peculiar star. Spectrum
variation of the well-known roAp star HR 3831 was detected using very high-resolution high
signal-to-noise spectroscopic time-series observations and was followed through the whole
rotation cycle of the star. We confirmed the outstanding diversity of pulsational
behaviour of different lines in the HR 3831 spectrum and attributed this phenomenon to an interplay
between extreme vertical chemical inhomogeneity of the HR 3831 atmosphere and a running pulsation
wave, that is propagating towards the upper photospheric layers with increasing amplitude.
The rapid profile variation of the 6145 Å line, which shows the maximum pulsational
disturbances in the studied wavelength region, is characterised by measuring changes of its
equivalent width and the first three moments. Each of these observables exhibits almost purely
sinusoidal variation through the pulsation cycle, with the amplitude and phase clearly
modulated by the stellar rotation.
In contrast to previous photometric pulsational measurements of
roAp stars, our spectroscopic observational material admits straightforward astrophysical
interpretation and, hence, opens new and exciting possibilities for direct and accurate analysis of
the roAp pulsations.
We demonstrate that rotational modulation of the radial
velocity oscillations cannot be fully explained by an oblique axisymmetric dipole (
,
) mode, implied by the classical oblique pulsator model of roAp stars.
Pulsational variation of the higher moments, in particular the line width, reveals substantial
contribution of the high-order (
) spherical harmonics that appear due to distortion of
pulsations in HR 3831 by the global magnetic field. We interpreted observations with a novel numerical
model of the pulsational variation and rotational modulation of the line profile moments in roAp
stars. Comparison of the observed and computed radial velocity
and line width variation was used to establish parameters of the oblique
pulsator model of HR 3831. Furthermore, definite detection of pulsational variation in lines of light
and iron-peak elements allows the first 3-D mapping of pulsations in a non-radially oscillating
star.
Key words: line: profiles / stars: chemically peculiar / stars: oscillations / stars: individual: HR 3831
© ESO, 2006
Current usage metrics show cumulative count of Article Views (full-text article views including HTML views, PDF and ePub downloads, according to the available data) and Abstracts Views on Vision4Press platform.
Data correspond to usage on the plateform after 2015. The current usage metrics is available 48-96 hours after online publication and is updated daily on week days.
Initial download of the metrics may take a while.