Modelling the pulsations of the roAp Star HR 1217

Hideyuki Saio, Tanya Ryabchikova, Mikhail Sachkov

Research output: Chapter in Book/Report/Conference proceedingConference contribution

Abstract

We have modeled the pulsations of HR 1217 (HD 24712), one of the best observed roAp (rapidly oscillating Ap) stars, by taking into account the nonadiabatic effect of radiation as well as the effect of the magnetic field assuming dipole fields. Since the observed frequencies are all above the critical frequencies of our models, a running wave outer boundary condition was imposed. All the oscillation modes examined for the observed frequency range are found to be damped; i.e, the K-mechanism excitation in the hydrogen-ionization zone is not strong enough. We probably need a new mechanism to excite p-modes in the cool roAp star HR 1217. The main pulsation frequency (2.721 mHz) is matched with a quasi-quadrapole mode (l m = 2, where l m is defined as effective latitudinal degree), and the highest frequency (2.806 mHz) obtained in a WET campaign is matched with an l m = 3 mode. Theoretical predictions for the distribution of the pulsation amplitudes and phases with respect to the optical depth agree reasonably with the results of spectroscopic analyses. We also show that the theoretical amplitude modulations with rotation phase agree qualitatively with the observed modulation.

Original languageEnglish
Title of host publicationStellar Pulsation
Subtitle of host publicationChallenges for Theory and Observation - Proceedings of the International Conference
Pages512-516
Number of pages5
DOIs
Publication statusPublished - 2009 Dec 1
EventInternational Conference on Stellar Pulsation: Challenges for Theory and Observation - Santa Fe, NM, United States
Duration: 2009 May 312009 Jun 5

Publication series

NameAIP Conference Proceedings
Volume1170
ISSN (Print)0094-243X
ISSN (Electronic)1551-7616

Other

OtherInternational Conference on Stellar Pulsation: Challenges for Theory and Observation
CountryUnited States
CitySanta Fe, NM
Period09/5/3109/6/5

Keywords

  • Ap stars
  • Magnetic fields
  • Stellar pulsations

ASJC Scopus subject areas

  • Physics and Astronomy(all)

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