Issue |
A&A
Volume 588, April 2016
|
|
---|---|---|
Article Number | A82 | |
Number of page(s) | 14 | |
Section | Stellar structure and evolution | |
DOI | https://doi.org/10.1051/0004-6361/201527055 | |
Published online | 22 March 2016 |
Testing the asymptotic relation for period spacings from mixed modes of red giants observed with the Kepler mission
1
Instituut voor Sterrenkunde, KU Leuven, Celestijnenlaan
200D, 3001
Leuven,
Belgium
e-mail:
bram.buysschaert@ster.kuleuven.be
2
Stellar Astrophysics Centre, Department of Physics and Astronomy,
Aarhus University, Ny Munkegade
120, 8000
Aarhus C,
Denmark
3
LESIA, Observatoire de Paris, PSL Research University, CNRS,
Sorbonne Universités, UPMC Univ.
Paris 6, Univ. Paris Diderot, Sorbonne Paris Cité, France
4
Laboratoire AIM, CEA/DSM − CNRS − Univ. Paris Diderot −
IRFU/SAp, Centre de
Saclay, 91191
Gif-sur-Yvette Cedex,
France
5
Instituto de Astrofisica de Canarias, 38205, La Laguna, Tenerife, Spain
6
Univ. de La Laguna, Dept. de Astrofisica, 38206, La
Laguna, Tenerife,
Spain
7
Dept. of Astrophysics, IMAPP, Radboud University
Nijmegen, 6500 GL
Nijmegen, The
Netherlands
8 Sydney Institute for Astronomy (SIfA), School of Physics,
University of Sydney, 2006, Australia
Received: 24 July 2015
Accepted: 3 February 2016
Context. Dipole mixed pulsation modes of consecutive radial order have been detected for thousands of low-mass red-giant stars with the NASA space telescope Kepler. These modes have the potential to reveal information on the physics of the deep stellar interior.
Aims. Different methods have been proposed to derive an observed value for the gravity-mode period spacing, the most prominent one relying on a relation derived from asymptotic pulsation theory applied to the gravity-mode character of the mixed modes. Our aim is to compare results based on this asymptotic relation with those derived from an empirical approach for three pulsating red-giant stars.
Methods. We developed a data-driven method to perform frequency extraction and mode identification. Next, we used the identified dipole mixed modes to determine the gravity-mode period spacing by means of an empirical method and by means of the asymptotic relation. In our methodology we consider the phase offset, ϵg, of the asymptotic relation as a free parameter.
Results. Using the frequencies of the identified dipole mixed modes for each star in the sample, we derived a value for the gravity-mode period spacing using the two different methods. These values differ by less than 5%. The average precision we achieved for the period spacing derived from the asymptotic relation is better than 1%, while that of our data-driven approach is 3%.
Conclusions. Good agreement is found between values for the period spacing derived from the asymptotic relation and from the empirical method. The achieved uncertainties are small, but do not support the ultra-high precision claimed in the literature. The precision from our data-driven method is mostly affected by the differing number of observed dipole mixed modes. For the asymptotic relation, the phase offset, ϵg, remains ill defined, but enables a more robust analysis of both the asymptotic period spacing and the dimensionless coupling factor. However, its estimation might still offer a valuable observational diagnostic for future theoretical modeling.
Key words: asteroseismology / stars: solar-type / stars: oscillations / stars: interiors
© ESO, 2016
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.