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arXiv 1202.0686astro-ph.SR
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在明亮的食双星中发现剥离的红巨星核心

Discovery of a stripped red giant core in a bright eclipsing binary star

P. F. L. Maxted, D. R. Anderson, M. R. Burleigh, A. Collier-Cameron, U. Heber, B. T. Gänsicke, S. Geier, T. Kupfer, T. R. Marsh, G. Nelemans, S. J. O'Toole, R. … 展开作者

P. F. L. Maxted, D. R. Anderson, M. R. Burleigh, A. Collier-Cameron, U. Heber, B. T. Gänsicke, S. Geier, T. Kupfer, T. R. Marsh, G. Nelemans, S. J. O'Toole, R. H. Østensen, B. Smalley, R. G. West, S. Bloemen

摘要:

我们报告了从WASP档案测光中偶然发现的一颗双星,其中一颗明显正常的A型星(J 0247 - 25 A)遮蔽了一颗较小,较热的亚矮星(J 0247 - 25 B)。J 0247 - 25 A的运动学表明它是银河系厚盘的蓝离散星成员。我们提出了后续的光度学和光谱学,从中我们得出的质量,半径和光度的近似值J 0247 - 25 B假设J 0247 - 25 A具有适当的质量正常厚盘星。我们发现J 0247 - 25 B的性质与一个剥除外层的红巨星模型很好地匹配,目前处于壳层氢燃烧阶段。在这种情况下,J 0247 - 25 B将继续成为一个低质量的白矮星(M~0.25太阳质量),主要由氦组成。J 0247 - 25 B的研究比迄今为止发现的少数前氦白矮星(前He-WD)要详细得多。这些结果已由Maxted等人发表,2011.我们还提出了一个初步的分析,最近的观测J 0247 -25的UVES光谱仪,从中我们得到了大大改善的质量为两颗恒星的二进制。我们发现这两颗恒星的质量都比预期的大,并且J 0247 - 25 A的旋转速度是次同步的2倍。我们还提出了5个新的日食前的He-WD随后确定从WASP档案测光,其中4个有质量估计的亚矮星同伴的基础上对径向速度测量的光变曲线。

英文摘要:

We report the serendipitous discovery from WASP archive photometry of a binary star in which an apparently normal A-type star (J0247-25A) eclipses a smaller, hotter subdwarf star (J0247-25B). The kinematics of J0247-25A show that it is a blue-straggler member of the Galactic thick-disk. We present follow-up photometry and spectroscopy from which we derive approximate values for the mass, radius and luminosity for J0247-25B assuming that J0247-25A has the mass appropriate for a normal thick-disk star. We find that the properties of J0247-25B are well matched by models for a red giant stripped of its outer layers and currently in a shell hydrogen-burning stage. In this scenario, J0247-25B will go on to become a low mass white dwarf (M~0.25 solar masses) composed mostly of helium. J0247-25B can be studied in much greater detail than the handful of pre helium white dwarfs (pre-He-WD) identified to-date. These results have been published by Maxted et al., 2011. We also present a preliminary analysis of more recent observations of J0247-25 with the UVES spectrograph, from which we derive much improved masses for both stars in the binary. We find that both stars are more massive than expected and that J0247-25A rotates sub-synchronously by a factor of about 2. We also present lightcurves for 5 new eclipsing pre-He-WD subsequently identified from the WASP archive photometry, 4 of which have mass estimates for the subdwarf companion based on a pair of radial velocity measurements.

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