Issue |
A&A
Volume 590, June 2016
|
|
---|---|---|
Article Number | A117 | |
Number of page(s) | 6 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/201527920 | |
Published online | 25 May 2016 |
The fundamental parameters of the roAp star HD 24712
A rapidly oscillator at the red edge of the instability strip⋆
1
Univ. Grenoble Alpes, IPAG,
38000
Grenoble,
France
e-mail:
karine.perraut@obs.ujf-grenoble.fr
2
CNRS, IPAG, 38000
Grenoble,
France
3
Instituto de Astrofísica e Ciências do Espaço, Universidade do
Porto, CAUP, Rua das
Estrelas, 4150-762
Porto,
Portugal
4
Institute for Astrophysics, Georg-August-University,
Friedrich-Hund-Platz 1,
37077
Göttingen,
Germany
5
Laboratoire Lagrange, Université Côte d’Azur, Observatoire de la
Côte d’Azur, CNRS, Bd de l’Observatoire, CS 34229, 06304
Nice Cedex 4,
France
6
CHARA Array, Mount Wilson Observatory,
91023
Mount Wilson
CA,
USA
Received: 8 December 2015
Accepted: 24 April 2016
Context. There is still a debate about the nature of the mechanism that causes the pulsation excitation of the rapidly oscillating Ap stars that oscillate above the highest theoretically acoustic frequency. HD 24712 is a good test case for such a study because it is bright, its parallax accurately determined, and its frequency spectrum is well known.
Aims. Visible long-baseline interferometry is a unique technique for measuring accurate angular diameters of targets as small as the brightest roAp stars, and thus estimating accurate radii by a method as independent as possible of atmosphere models.
Methods. We used the visible spectrograph VEGA at the CHARA long-baseline optical array to observe HD 24712, and we derived its limb-darkened diameter. We also estimated its bolometric flux from spectroscopic data in the literature and determined its radius, luminosity, and effective temperature.
Results. We determined a limb-darkened angular diameter of 0.335 ± 0.009 mas for HD 24712 and derived a radius of R = 1.772 ± 0.057 R⊙, a luminosity of L = 7.2 ± 1.8 L⊙, and an effective temperature of Teff = 7235 ± 280 K, which is in very close agreement with the values provided by the self-consistent stratified model developed for this star. We used these fundamental parameters to set HD 24712 in the Hertzsprung-Russell diagram. Its position is marginally consistent with the region where high radial order modes are predicted to be excited by the κ-mechanism.
Conclusions. We conclude that oscillations in this star are most likely not driven by the κ-mechanism.
Key words: stars: fundamental parameters / stars: individual: HD 24712 / techniques: high angular resolution / techniques: interferometric
© ESO, 2016
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