Indirect imaging of nonradial pulsations in a rapidly oscillating Ap star

Abstract

Many types of stars show periodic variations of radius and brightness, which are commonly referred to as `stellar pulsations'. Observed pulsational characteristics are determined by fundamental stellar parameters. Consequently, investigations of stellar pulsations provide a unique opportunity to verify and refine our understanding of the evolution and internal structure of stars. However, a key boundary condition for this analysis -- precise information about the geometry of pulsations in the outer stellar envelopes -- has been notoriously difficult to secure. Here we demonstrate that it is possible to solve this problem by constructing an `image' of the pulsation velocity field from time series observations of stellar spectra. This technique is applied to study the geometry of nonradial pulsations in a prototype magnetic oscillating (roAp) star HR 3831. Our velocity map directly demonstrates an alignment of pulsations with the axis of the global magnetic field and reveals a significant magnetically induced distortion of pulsations. This observation constitutes a long-sought solution of the problem of the pulsation geometry of roAp stars and enables very stringent tests of the recent theories of stellar magneto-acoustic oscillations.

accepted by ApJ Letters

Cited by in corpus (19)

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• The discovery of high-amplitude 10.9-minute oscillations in the cool magnetic Ap star HD 115226
• Variation of the line profile moments for stars pulsating in distorted oblique non-radial modes
• A theoretical tool for the study of radial velocities in the atmospheres of roAp stars
• Simulations of magneto-acoustic pulsations in atmospheres of rapidly oscillating Ap stars
• Pulsation of magnetic stars
• A high-precision search for magnetic field oscillations in the roAp star HD 24712