Abundance analysis of roAp stars IV. HD 24712

Autor(en)

Tanya A. Ryabchikova, John Darlington Landstreet, Michael Gelbmann, G T Bolgova, Vadim Tsymbal, Werner Wolfgang Weiss

Abstrakt

We present the first abundance analysis of the rapidly oscillating chemically peculiar star HD 24712, and determine a T eff = 7250 K, log g = 4.3, and Ξ= 1 km s -1. Microturbulence seems to be entirely simulated by a magnetic field with a polar field strength of 4.4 kG and of dipolar structure, both of which are supported by our polarimetric observations. Rotation of HD 24712 and a spotty surface distribution of the elements result in different mean abundances for different (magnetic) phases. Our results do not support the hypothesis of a monotonic correlation between the amplitude of abundance variations and the atomic number Z, and we present arguments in favour of one of the rotation periods (P rot = 12. d4610) discussed in the literature. Rare earth elements are the most overabundant elements relative to the sun, and they have the largest abundance amplitude during a rotation cycle; only Mg has a larger amplitude. For HD 24712 we find a clear overabundance of Co while most of the other iron peak elements are underabundant. A comparison of the abundance pattern with the other three roAp stars analyzed so far by us concludes the paper. A systematic difference between surface gravities obtained from spectroscopy and from both asteroseismology and evolutionary tracks is found for the roAp stars HD 24712, α Cir and γEqu.

Organisation(en)

Institut für Astrophysik

Externe Organisation(en)

Russian Academy of Sciences, University of Western Ontario, Taurida National V. I. Vernadsky University

Journal

Astronomy & Astrophysics

Band

327

Seiten

1137-1146

Anzahl der Seiten

10

ISSN

0004-6361

Publikationsdatum

1997

Peer-reviewed

Ja

ÖFOS 2012

103003 Astronomie

Link zum Portal

https://ucrisportal.univie.ac.at/de/publications/abundance-analysis-of-roap-stars-iv-hd-24712(625f1eab-674f-4be1-81fd-9f67b67f3f0e).html