Distinguishing Core and Shell Helium-burning Subdwarf B Stars by Asteroseismology
Distinguishing Core and Shell Helium-burning Subdwarf B Stars by Asteroseismology
复制标题
DOI：
10.3847/1538-4357/aadd05
复制
发表时间：
2018-10
期刊：
影响因子：
--
通讯作者：
Jun-Jun Guo-Jun
中科院分区：
文献类型：
--
作者：
Jun-Jun Guo-Jun
亚矮星B通常被认为是核心燃烧氦的恒星。然而，大多数规范sdB模型已经表明，它们离开sdB频带（即，20，000 K ≤ Teff ≤ 40，000 K的区域和）在它们点燃壳层中的氦之后。这意味着会有一些燃烧氦的壳层恒星，它们已经耗尽了核心中的氦，但可能仍然位于sdB波段，也应该被认为是sdB恒星。但由于它们的有效温度和引力与核心燃烧氦的sdB星相近，因此我们不能仅凭大气参数来区分这两类星星。一些sdB星显示多模脉动。我们认为星震学可以提供一些区分这两类sdB星星的方法。核和壳层氦燃烧sdB星在结构和演化轨迹上存在明显的差异，导致它们的脉动性质存在明显的差异。因此，我们可以通过它们的脉动特性，如p模sdB振荡器的周期变化率、混合模的数目和g模sdB振荡器的周期间隔来区分它们。我们认为，有两个特殊的sdB星（V391飞马座和PG 1605+072），可能是壳氦燃烧sdB星。
Subdwarf B stars are generally considered to be core helium-burning stars. However, most canonical sdB models have shown that they leave the sdB band (i.e., the region with 20,000 K ≤ Teff ≤ 40,000 K and ) after they have ignited helium in the shell. This means there will be a few shell helium-burning stars that have exhausted their helium in the core yet may still be located on the sdB band and should be considered as sdB stars too. But because they have effective temperature and gravity close to those of core helium-burning sdB stars, we cannot distinguish the two kinds of star just by atmospheric parameters. Some sdB stars display multimode pulsations. We thought that asteroseismology could offer some methods to distinguish the two kinds of sdB star. Core and shell helium-burning sdB stars have some obvious differences in structure and evolutionary track, which results in some clear differences in their pulsation properties. So, we may distinguish them by their pulsation properties such as the rates of change of period of the p-mode sdB pulsators, the numbers of mixed modes, and the period spacings of the g-mode sdB pulsators. We suggest that there are two special sdB stars (V391 Pegasi and PG 1605+072) that are likely shell helium-burning sdB stars.