Kavli Affiliate: Huawei Zhang
| First 5 Authors: Fangfei Shi, Donald W. Kurtz, Daniel L. Holdsworth, Hideyuki Saio, Margarida S. Cunha
| Summary:
We report the frequency analysis of a known roAp star, HD 86181 (TIC
469246567), with new inferences from TESS data. We derive the rotation
frequency to be $nu_{rot}$ = 0.48753 $pm$ 0.00001d$^{-1}$. The pulsation
frequency spectrum is rich, consisting of two doublets and one quintuplet,
which we interpret to be oblique pulsation multiplets from consecutive,
high-overtone dipole, quadrupole and dipole modes. The central frequency of the
quintuplet is 232.7701d$^{-1}$ (2.694 mHz). The phases of the sidelobes, the
pulsation phase modulation, and a spherical harmonic decomposition all show
that the quadrupole mode is distorted. Following the oblique pulsator model, we
calculate the rotation inclination, i, and magnetic obliquity, $beta$, of this
star, which provide detailed information about the pulsation geometry. The i
and $beta$ derived from the best fit of the pulsation amplitude and phase
modulation to a theoretical model, including the magnetic field effect,
slightly differ from those calculated for a pure quadrupole, indicating the
contributions from l = 4, 6, 8, … are small. Non-adiabatic models with
different envelope convection conditions and physics configurations were
considered for this star. It is shown that models with envelope convection
almost fully suppressed can explain the excitation at the observed pulsation
frequencies.
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