The discovery of high-amplitude 10.9-minute oscillations in the cool magnetic Ap star HD 115226

TL;DR

This paper reports the first detection of high-amplitude pulsations in the cool magnetic Ap star HD 115226 using time-series spectroscopy, revealing a 10.86-minute oscillation with significant amplitude and atmospheric wave phenomena.

Contribution

It presents the discovery of high-amplitude pulsations in HD 115226, expanding understanding of pulsational behavior in cool magnetic Ap stars through spectroscopic analysis.

Findings

Radial velocity variations with a period of 10.86 min detected in multiple spectral lines.

Pulsational amplitudes exceed 1 km/s in Nd III lines.

Evidence of running waves in the stellar atmosphere inferred from phase shifts.

Abstract

We present the discovery of pulsational variations in the cool magnetic Ap star HD 115226 -- the first high-amplitude rapidly oscillating Ap star discovered with time-series spectroscopy. Using high-resolution spectra obtained with the HARPS instrument at the ESO 3.6-m telescope, we detect radial velocity variations with a period of 10.86 min in Pr III, Nd III, Dy III lines and in the narrow cores of hydrogen lines. Pulsational amplitudes exceed 1 km/s in individual lines of Nd III. The presence of running waves in the stellar atmosphere is inferred from a phase shift between the radial velocity maxima of rare-earth and hydrogen lines. Our abundance analysis demonstrates that HD 115226 exhibits typical roAp spectroscopic signature, notably ionization anomaly of Pr, Nd and Dy. We discuss the discovery of pulsations in HD 115226 in the context of recent spectroscopic studies of roAp stars and point to the existence of correlation between spectroscopic pulsational amplitude and the stellar rotation rate.