EDP Sciences
Free Access
Volume 384, Number 2, March III 2002
Page(s) 545 - 553
Section Formation, structure and evolution of stars
DOI https://doi.org/10.1051/0004-6361:20020057
Published online 15 March 2002

A&A 384, 545-553 (2002)
DOI: 10.1051/0004-6361:20020057

Abundance stratification and pulsation in the atmosphere of the roAp star $\boldmath\gamma$ Equulei

T. Ryabchikova1, 2, N. Piskunov3, O. Kochukhov3, V. Tsymbal4, P. Mittermayer2 and W. W. Weiss2

1  Institute of Astronomy, Russian Academy of Sciences, Pyatnitskaya 48, 109017 Moscow, Russia
    e-mail: ryabchik@inasan.rssi.ru
2  Institute for Astronomy, University of Vienna, Türkenschanzstrasse 17, 1180 Wien, Austria
    e-mail: last_name@astro.univie.ac.at
3  Uppsala Astronomical Observatory, Box 515, 751 20, Sweden
    e-mail: piskunov@astro.uu.se, oleg@astro.uu.se
4  Tavrian National University, Yaltinskaya 4, 330000 Simferopol, Crimea, Ukraine
    e-mail: vad@ccssu.crimea.ua

(Received 11 October 2001 / Accepted 10 January 2002 )

We present the evidence for abundance stratification in the atmosphere of the rapidly oscillating Ap star $\gamma$ Equ. Ca, Cr, Fe, Ba, Si, Na seem to be overabundant in deeper atmospheric layers, but normal to underabundant in the upper layers with a transition in the typical line forming region of $-1.5<\log\tau_{5000}<-0.5$. This stratification profile agrees well with diffusion theory for Ca and Cr, developed for cool magnetic stars with a weak mass loss of ${\approx}2.5\times10^{-15}~M_{\odot}$ yr -1. Pr and Nd from the rare earth elements have an opposite profile. Their abundance is more than 6 dex higher above $\log\tau_{5000}\,\approx\,-8.0$ than in the deeper atmospheric layers. We further discuss the implications of abundance stratification in the context of radial velocity amplitudes and phases observed by Kochukhov & Ryabchikova (2001) for a variety of spectral lines and elements using high spectral and time resolved, high S/N observations.

Key words: stars: chemically peculiar -- stars: abundances -- stars: oscillations -- stars: individual: $\gamma$ Equ

Offprint request: W. W. Weiss, weiss@astro.univie.ac.at

SIMBAD Objects

© ESO 2002

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.