Numerical simulations of line-profile variation beyond a single-surface approximation for oscillations in roAp stars

TL;DR

This paper presents a numerical simulation method for analyzing spectroscopic line-profile variations in roAp stars, accounting for the finite thickness of the line-forming layer to better understand their atmospheric vertical structure.

Contribution

It introduces a simulation approach that goes beyond single-surface approximation by considering the finite thickness of the line-forming layer in roAp stars.

Findings

Simulation matches observed line profiles effectively

Vertical structure information can be extracted from line-profile variations

Method improves understanding of atmospheric oscillations in roAp stars

Abstract

Prior to the last decade, most observations of roAp stars have concerned the light variations. Recently some new, striking results of spectroscopic observations with high time resolution, high spectral dispersion, and a high signal-to-noise ratio became available. Since the oscillations found in roAp stars are high overtones, the vertical wavelengths of the oscillations are so short that the amplitude and phase of the variation of each spectroscopic line are highly dependent on the level of the line profile. Hence, analyses of the variation of the spectroscopic lines of roAp stars potentially provide us with new information about the vertical structure of the atmosphere of these stars. In order to extract such information, a numerical simulation of the line-profile variation beyond a single-surface approximation is necessary. We carried out a numerical simulation of line-profile variation by taking account of the finite thickness of the line forming layer. We demonstrated how effective this treatment is, by comparing the simulation with the observed line profiles.