Period spacings in red giants. III. Coupling factors of mixed modes
Period spacings in red giants. III. Coupling factors of mixed modes
复制标题
红巨星的周期间隔。
DOI：
10.1051/0004-6361/201630053
复制
发表时间：
2017
影响因子：
6.5
通讯作者：
M.
中科院分区：
文献类型：
--
作者：
Mosser;B.; Pincon;C.; Belkacem;K.; Takata;M.; Vrard;M.
背景星震学的力量依赖于全球振荡来推断恒星结构的能力。对于演化的恒星，我们受益于通过探测其辐射核心的混合模式直接获得的独特信息。该系列的第三篇文章致力于红巨星的混合模式，重点关注它们的耦合因子，到目前为止，这些耦合因子在很大程度上尚未被开发。目的通过耦合因子的测量，我们打算对亚巨星和红巨星的辐射核和氢燃烧壳周围的区域给出物理约束。方法一种测量混合模式耦合因子的新方法是 已实施，该方法源自最近实施的用于测量周期间隔的方法。这种新方法是自动化的，因此可以应用于大量恒星样本。结果测量了数千个红巨星的混合模式耦合因子。它们随着质量和进化阶段而表现出特定的变化。仅在红巨星分支上最进化的恒星中观察到弱耦合；在亚巨星和红巨星之间的过渡以及红团簇中测量到大的耦合因子。结论偶极子混合模式中耦合因子的测量为演化恒星的内部结构提供了新的见解。虽然大频率间隔和渐进周期间隔分别探测包络和核心，但耦合因子对之间的中间区域直接敏感，并有助于确定其范围。据观察，耦合因子的确定是在混合模式模式的精确拟合之前确定的，现在可用于解决混合模式模式的进一步属性，例如浮力毛刺和核心旋转的特征。
ContextThe power of asteroseismology relies on the capability of global oscillations to infer the stellar structure. For evolved stars, we benefit from unique information directly carried out by mixed modes that probe their radiative cores. This third article of the series devoted to mixed modes in red giants focuses on their coupling factors, which have remained largely unexploited up to now.AimsWith the measurement of coupling factors, we intend to give physical constraints on the regions surrounding the radiative core and the hydrogen-burning shell of subgiants and red giants.MethodsA new method for measuring the coupling factor of mixed modes was implemented, which was derived from the method recently implemented for measuring period spacings. This new method was automated so that it could be applied to a large sample of stars.ResultsCoupling factors of mixed modes were measured for thousands of red giants. They show specific variation with mass and evolutionary stage. Weak coupling is observed for the most evolved stars on the red giant branch only; large coupling factors are measured at the transition between subgiants and red giants as well as in the red clump.ConclusionsThe measurement of coupling factors in dipole mixed modes provides a new insight into the inner interior structure of evolved stars. While the large frequency separation and the asymptotic period spacings probe the envelope and core, respectively, the coupling factor is directly sensitive to the intermediate region in between and helps determine its extent. Observationally, the determination of the coupling factor is a prior to precise fits of the mixed-mode pattern and can now be used to address further properties of the mixed-mode pattern, such as the signature of buoyancy glitches and core rotation.