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arXiv 0812.2424astro-ph
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低质谱双星中的孪生子

Twins Among the Low Mass Spectroscopic Binaries

M. Simon, R. C. Obbie

摘要:

本文报道了对光谱型为F或F以后的第9个光谱双星表(SB 9)中的一对孪生子的分析。双星是质量比在1.0的2%以内的双星的组成部分,在F和G光谱型的双星中发现。它们在周期小于43天的双星中最为突出,这是露西首先发现的。在P<43天的双星子样本中,孪生双星在周期(中位数P~ 7 d)、质量或轨道偏心率的分布上与其他双星没有区别。将SB 9在0.6 ~ 0.85 Msun质量范围内的质量比分布与Mazeh等人在Latham高自行巡天中测量的双星质量比分布相结合,我们估计在大样本的光谱双星中双胞胎的频率约为3%。目前的理论理解表明,原双星吸积高比角动量物质往往会使其质量相等。我们推测,多余的双胞胎是在那些恒星形成区域的吸积过程能够进行到少数原双星完成。这预示着年轻双星的组成部分可能在年龄上有所不同,并且在恒星形成区的光谱双星样本中,平均而言,双胞胎比质量比远小于1的双星更老。

英文摘要:

We report an analysis of twins of spectral types F or later in the 9th Catalog of Spectroscopic Binaries (SB9). Twins, the components of binaries with mass ratio within 2% of 1.0, are found among the binaries with primaries of F and G spectral type. They are most prominent among the binaries with periods less than 43 days, a cutoff first identified by Lucy. Within the subsample of binaries with P<43 days, the twins do not differ from the other binaries in their distributions of periods (median P~7d), masses, or orbital eccentricities. Combining the mass ratio distribution in the SB9 in the mass range 0.6 to 0.85 Msun with that measured by Mazeh et al. for binaries in the Carney-Latham high proper motion survey, we estimate that the frequency of twins in a large sample of spectroscopic binaries is about 3%. Current theoretical understanding indicates that accretion of high specific angular momentum material by a protobinary tends to equalize its masses. We speculate that the excess of twins is produced in those star forming regions where the accretion processes were able to proceed to completion for a minority of protobinaries. This predicts that the components of a young twin may appear to differ in age and that, in a sample of spectroscopic binaries in a star formation region, the twins are, on average, older than the binaries with mass ratios much smaller than 1.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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