arXiv 0909.25602009-09-14astro-ph.SR

大量的热亚矮星

The masses of hot subdwarfs

X. Zhang, X. Chen, Z. Han

备注：: 5 pages, 6 figures, accepted for publication in A&A Letters
发表信息：: A&A 504, L13?CL16 (2009)
DOI：: 10.1051/0004-6361/200912336

摘要：

质量是一个基本的参数，但对于大多数热亚矮星来说，它们并不为人所知。一般来说，热亚矮星的质量是通过星震学或动力学方法推导出来的，这通常很难从观测中获得必要的数据。我们打算找到一种方法，从文献中的观测数据推导出热亚矮星的质量。我们提出了一个完整的演化计算热次矮星在一个广泛的质量范围内（0.33 $M_\odot$至1.4 $M_\odot$）的第一人口的金属丰度$Z$ =0.02，并获得了$M_{\rm p}$和$\log (\frac{T_{\rm eff}^4}{g})$之间的关系，其中$M_{\rm p}$，$T_{\rm eff}$，和$g$是最可几的质量，有效温度和重力。这个关系被用来研究一些观测到的热亚矮星的质量。我们提出了一种确定热次矮星质量的方法。利用这种方法，我们研究了来自ESO Ia超新星前身巡天和汉堡类星体巡天的热次矮星的质量。研究表明，大多数亚矮星B的质量在0.42 - 0.54 $M_\odot$之间，而大多数sdO星的质量在0.40 - 0.55 $\sim$之间。与Han等人（2003）的理论质量分布比较，我们发现质量小于$\sim$ 0.5 $M_\odot$的sdO星可能是由sdB星演化而来，而大多数高质量（$>$ 0.5 $M_\odot$）sdO星则是由合并直接产生的。

英文摘要：

Masses are a fundamental parameter, but they are not well known for most hot subdwarfs. In general, the mass of a hot subdwarf is derived with asteroseismology or dynamical methods, for which it is often difficult to obtain the necessary data from observations. We intend to find an approach to deriving the masses of hot subdwarfs from observational data in the literature. We presented full evolutionary calculations for hot subdwarfs in a wide mass range (0.33 $M_\odot$ to 1.4 $M_\odot$) for a Population I metallicity of $Z$=0.02, and obtained a relation between $M_{\rm p}$ and $\log (\frac{T_{\rm eff}^4}{g})$, where $M_{\rm p}$, $T_{\rm eff}$, and $g$ are the most probable mass, effective temperature, and gravity. This relation is used to study the masses of some observed hot subdwarfs. We proposed a method of determining the masses of hot subdwarfs. Using this method, we studied the masses of hot subdwarfs from the ESO supernova Ia progenitor survey and Hamburg quasar survey. The study shows that most of subdwarf B stars have masses between 0.42 and 0.54 $M_\odot$, whilst most sdO stars are in the range 0.40 $\sim$ 0.55 $M_\odot$. Comparing our study to the theoretical mass distributions of Han et al. (2003), we found that sdO stars with mass less than $\sim$ 0.5 $M_\odot$ may evolve from sdB stars, whilst most high-mass($>$ 0.5 $M_\odot$) sdO stars result from mergers directly.

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