Pulsation models for the roAp star HD 134214

Abstract

Precise time-series photometry with the MOST satellite has led to identification of 10 pulsation frequencies in the rapidly oscillating Ap (roAp) star HD 134214. We have fitted the observed frequencies with theoretical frequencies of axisymmetric modes in a grid of stellar models with dipole magnetic fields. We find that, among models with a standard composition of $(X,Z)=(0.70,0.02)$ and with suppressed convection, eigenfrequencies of a $1.65{\mathrm{M}}_{\odot }$ model with $\log T_{\mathrm{eff}}=3.858$ and a polar magnetic field strength of 4.1kG agree best with the observed frequencies. We identify the observed pulsation frequency with the largest amplitude as a deformed dipole ($\ell =1$) mode, and the four next-largest-amplitude frequencies as deformed $\ell =2$ modes. These modes have a radial quasi-node in the outermost atmospheric layers ($\tau \sim 10^{-3}$). Although the model frequencies agree roughly with observed ones, they are all above the acoustic cut-off frequency for the model atmosphere and hence are predicted to be damped. The excitation mechanism for the pulsations of HD 134214 is not clear, but further investigation of these modes may be a probe of the atmospheric structure in this magnetic chemically peculiar star.

9 pages, 6 figures; accepted for publication in MNRAS

References in corpus (10)

• Evolutionary state of magnetic chemically peculiar stars
• Pulsation tomography of rapidly oscillating Ap stars. Resolving the third dimension in peculiar pulsating stellar atmospheres
• Isotopic anomaly and stratification of Ca in magnetic Ap stars
• Improved pulsating models of magnetic Ap stars I: exploring different magnetic field configurations
• The first evidence for multiple pulsation axes: a new roAp star in the Kepler field, KIC 10195926
• MOST photometry and modeling of the rapidly oscillating (roAp) star gamma Equ
• MOST photometry of the roAp star 10 Aql
• On the understanding of pulsations in the atmosphere of roAp stars: phase diversity and false nodes
• MOST Photometry of the roAp Star HD 134214
• MOST observations of the roAp stars HD 9289, HD 99563, and HD 134214

Cited by in corpus (7)

• Asteroseismology Can Reveal Strong Internal Magnetic Fields in Red Giant Stars
• Testing excitation models of rapidly oscillating Ap stars with interferometry
• The fundamental parameters of the roAp star 10 Aql
• A theoretical tool for the study of radial velocities in the atmospheres of roAp stars
• Pulsation of magnetic stars
• The search for roAp stars: null results and new candidates from Stroemgren-Crawford photometry
• Unveiling the Variability and Chemical Composition of AL Col