标题： 近核对流壳层对亚矮星B脉动体KIC 10553698A的重力模式的影响 显示英文标题

标题： The effects of near-core convective shells on the gravity modes of the subdwarf B pulsator KIC 10553698A

摘要： KIC 10553698A 是一颗由开普勒卫星观测到的热脉动次矮星 B (sdB)。 它表现出偶极 (l = 1) 和四极 (l = 2) 重力模，具有清晰的周期间距结构。 KIC 10553698A 的地震特性为恒星演化模型提供了测试，并提供了一个独特的机会来确定混合过程。 我们考虑了超出氦燃烧核心边界之外的对流超射引起的混合。 非常小的超射 ( f = 10^{-6}) 导致对流核心尺寸逐渐增大。 然而，中等 ( f = 10^{-2}) 和小 ( f = 10^{-5}) 超射都会导致近核心区域出现惰性外对流壳层。 我们说明由对流壳层引起的化学分层能够显著改变 sdB 星的 g 模周期间距模式。 在中等和小核心超射模型中，平均周期间距以及重力模的捕获与 KIC 10553698A 中观察到的周期间距趋势完全一致。 应用由重力沉降以及热和化学梯度驱动的原子扩散以更好地匹配观察到的周期间距。 包含小或非常小超射以及原子扩散的模型，其极端水平分支阶段的寿命减少，并在氦燃烧阶段产生由对流壳层引起的化学分层。 除了与星震学一致外，它们计算的 R2 参数值更符合观察到的 R2 值。 显示英文摘要

摘要： KIC 10553698A is a hot pulsating subdwarf B (sdB) star observed by the Kepler satellite. It exhibits dipole (l = 1) and quadrupole (l = 2) gravity modes with a clear period spacing structure. The seismic properties of the KIC 10553698A provide a test of stellar evolution models, and offer a unique opportunity to determine mixing processes. We consider mixing due to convective overshooting beyond the boundary of the helium burning core. Very small overshooting ( f = 10^{-6} ) results in a progressive increase in the size of convective core. However, moderate ( f = 10^{-2} ) and small ( f = 10^{-5} ) overshooting both lead to the occurrence of inert outer convective shells in the near-core region. We illustrate that the chemical stratifications induced by convective shells are able to change the g-mode period spacing pattern of a sdB star appreciably. The mean period spacing and trapping of the gravity modes in the model with moderate and small core overshooting are fully consistent with the period spacing trends observed in KIC 10553698A. Atomic diffusion driven by gravitational settling as well as thermal and chemical gradients is applied to reach a better match with the observed period spacings. Models that include small or very small overshooting with atomic diffusion have a decreased lifetime of the extreme horizontal branch phase and produce chemical stratification induced by convective shells during helium burning phase. In addition of being consistent with asteroseismology, their calculated values of the R2 parameter are more compatible with the observed R2 values.