文章基本信息

标题：Transport of angular momentum by stochastically excited waves as an explanation for the outburst of the rapidly rotating Be star HD49330 ⋆
本地全文：下载
作者：C. Neiner ; U. Lee ; S. Mathis 等
期刊名称：Astronomy & Astrophysics
印刷版ISSN：0004-6361
电子版ISSN：1432-0746
出版年度：2020
卷号：644
页码：1-15
DOI：10.1051/0004-6361/201935858
语种：English
出版社：EDP Sciences
摘要：Context.HD 49330 is an early Be star that underwent an outburst during its five-month observation with the CoRoT satellite. An analysis of its light curve revealed several independentpandgpulsation modes, in addition to showing that the amplitude of the modes is directly correlated with the outburst.Aims.We modelled the results obtained with CoRoT to understand the link between pulsational parameters and the outburst of this Be star.Methods.We modelled the flattening of the structure of the star due to rapid rotation in two ways: Chandrasekhar-Milne’s expansion and 2D structure computed with ROTORC. We then modelledκ-driven pulsations. We also adapted the formalism of the excitation and amplitude of stochastically excited gravito-inertial modes to rapidly rotating stars, and we modelled those pulsations as well.Results.We find that while pulsationpmodes are indeed excited by theκmechanism, the observedgmodes are, rather, a result of stochastic excitation. In contrast,gandrwaves are stochastically excited in the convective core and transport angular momentum to the surface, increasing its rotation rate. This destabilises the external layers of the star, which then emits transient stochastically excitedgwaves. These transient waves produce most of the low-frequency signal detected in the CoRoT data and ignite the outburst. During this unstable phase,pmodes disappear at the surface because their cavity is broken. Following the outburst and ejection of the surface layer, relaxation occurs, making the transientgwaves disappear andpmodes reappear.Conclusions.This work includes the first coherent model of stochastically excited gravito-inertial pulsation modes in a rapidly rotating Be star. It provides an explanation for the correlation between the variation in the amplitude of frequencies detected in the CoRoT data and the occurrence of an outburst. This scenario could apply to other pulsating Be stars, providing an explanation to the long-standing questions surrounding Be outbursts and disks.
关键词：enstars: emission-line, Bestars: oscillationsstars: rotationstars: individual: HD49330