Issue |
A&A
Volume 424, Number 3, September IV 2004
|
|
---|---|---|
Page(s) | 935 - 950 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361:20040517 | |
Published online | 06 September 2004 |
Multi-element abundance Doppler imaging of the rapidly oscillating Ap star HR 3831*
1
Institut für Astronomie, Universität Wien, Türkenschanzstraße 17, 1180 Wien, Austria e-mail: kochukhov@astro.univie.ac.at
2
Observatório Nacional/MCT, Rua General Jose Cristino 77, 20921-400, Rio de Janeiro, Brazil
3
Sobolev Astronomical Institute, St. Petersburg State University, Universitetsky pr. 28, Petrodvorets, 198504, St. Petersburg, Russia
4
Department of Astronomy and Space Physics, Uppsala University, Box 515, 751 20 Uppsala, Sweden
Received:
25
March
2004
Accepted:
24
May
2004
We investigate magnetic field geometry and surface distribution of chemical elements in the rapidly oscillating Ap star HR 3831. Results of the model atmosphere analysis of the spectra of this
star are combined with the Hipparcos parallax and evolutionary models to obtain new accurate
estimates of the fundamental stellar parameters: K,
,
and an inclination angle
of the stellar axis of rotation. We find that
the variation of the longitudinal magnetic field of HR 3831 and the results of our analysis of the
magnetic intensification of
lines in the spectrum of this star are consistent with a
dipolar magnetic topology with a magnetic obliquity
and a polar strength
kG. We apply a multi-element abundance Doppler imaging inversion code for the analysis of
the spectrum variability of HR 3831, and recover surface distributions of 17 chemical elements, including Li, C, O, Na, Mg, Si, Ca, Ti, Cr, Mn, Fe, Co, Ba, Y, Pr, Nd, Eu. Our study represents the most thorough examination of the surface chemical structure in a magnetic Ap star and provides
important observational constraints for modelling radiative diffusion in magnetic stars.
The exceedingly high quality of some of our spectroscopic data allowed us to reconstruct unprecedented details of abundance distributions, demonstrating a high level of complexity in the surface structure down to the resolution limit of the Doppler maps.
The Doppler imaging analysis of HR 3831 forms a basis for subsequent detailed observational
investigations and theoretical modelling of non-radial oscillations in this star. We discuss the compound effect of the chemical nonuniformities and pulsational velocity field on the rapid line profile variations, and assess the possibility of identifying pulsation modes by using spatial
filtering produced by an inhomogeneous abundance distribution. The results of our study of the surface chemical structure suggest that differences in pulsational behaviour of lines of different
ions observed for HR 3831 are not a consequence of horizontal atmospheric inhomogeneities, but
predominantly a depth effect.
Key words: stars: chemically peculiar / stars: magnetic fields / stars: individual: HR 3831
© ESO, 2004
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