The distribution, kinematics, and luminosities of extreme helium stars as probes of their origin and evolution
The distribution, kinematics, and luminosities of extreme helium stars as probes of their origin and evolution
复制标题
极端氦星的分布、运动学和光度作为其起源和演化的探针
DOI：
10.1093/mnras/stad3291
复制
发表时间：
2024
影响因子：
4.8
通讯作者：
Philip Monai A
中科院分区：
文献类型：
--
作者：
Philip Monai A
贫氢恒星包括冷的R CRB变星(RCB)和从极端氦恒星(EHE)到非常热的富氦亚矮星(He- 和O(He)星)以及白矮星的贫氢巨星(HDC)。由于表面富含氦、氮和碳，它们的起源已被确定为两颗白矮星的合并。我们的目标是确定银河系的祖先种群，并检验演化模型。GaiaDR3测量和地面径向速度已经被用来计算银河轨道。每个轨道都是按人口分类的；EHE恒星存在于所有的薄盘、厚盘、晕和凸起中，RCB、HDC和He-SDO恒星也是如此。光谱能量分布是为所有EHE构造的，以提供角直径，从而提供半径和亮度。EHES分为两个发光组。这支持了EHES起源的理论，也是迄今为止在光度方面最有力的证实。较低的光度EHes与双氦白矮星合并后的演化很好地对应。同样，较高的光度EHes与合并后的碳/氧加氦白矮星双星的演化相匹配。就母星群而言，目前的模型预测双白矮星合并应该发生在所有银河系人口中，但倾向于最近恒星形成(即薄盘)产生的合并，而统计数据有利于较老的纪元(即厚盘)。
Hydrogen-deficient stars include the cool R CrB variable (RCBs) and hydrogen-deficient carbon (HdCs) giants through extreme helium stars (EHes) to the very hot helium-rich subdwarfs (He-sdO and O(He) stars) and white dwarfs. With surfaces rich in helium, nitrogen, and carbon, their origins have been identified with the merger of two white dwarfs. UsingGaiato focus on the EHes, we aim to identify progenitor populations and test the evolution models.GaiaDR3 measurements and ground-based radial velocities have been used to compute Galactic orbits usinggalpy. Each orbit has been classified by population; EHe stars are found in all of the thin disc, thick disc, halo, and bulge, as are RCB, HdC, and He-sdO stars. Spectral energy distributions were constructed for all EHes, to provide angular diameters, and hence radii and luminosities. The EHes fall into two luminosity groups divided at. This supports theory for the origin of EHes, and is the strongest confirmation so far in terms of luminosity. The lower luminosity EHes correspond well with the post-merger evolution of a double helium white dwarf binary. Likewise, the higher luminosity EHes match the post-merger evolution of a carbon/oxygen plus helium white dwarf binary. In terms of parent populations, current models predict that double white dwarf mergers should occur in all Galactic populations, but favour mergers arising from recent star formation (i.e. thin disc), whereas the statistics favour an older epoch (i.e. thick disc).