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arXiv 0704.0059astro-ph
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单线双星HAT-TR-205-013中不可见M矮星伴星的质量和半径

The Mass and Radius of the Unseen M-Dwarf Companion in the Single-Lined Eclipsing Binary HAT-TR-205-013

T. G. Beatty, J. M. Fernandez, D. W. Latham, G. A. Bakos, G. Kovacs, R. W. Noyes, R. P. Stefanik, G. Torres, M. E. Everett, C. W. Hergenrother

备注：
18 pages, 9 tables and 6 figures; accepted by ApJ. Added a reference and corrected a typo
发表信息：
Astrophys.J.663:573-582,2007
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摘要：

我们推导了单线食双星HAT-TR-205-013中两个分量的质量和半径，该双星由F7 V主星和晚M矮星次级星组成。该系统的周期很短，为$P=2.230736 \pm 0.000010$天，轨道与圆形$e=0.012 \pm 0.021$难以区分。一般地，我们证明了在经历日全食的单线双星中，次级星的表面重力可以从光变曲线和分光轨道的特征中导出。这会将次级线圈约束为质量-半径图中的唯一线，其中$M/R^2$ =常数。对于HAT-TR-205-013，我们假设轨道已经潮汐圆形化，并且主旋转已经同步并与轨道轴对齐。我们观察到的谱线增宽，$V_{\rm rot} \sin i_{\rm rot} = 28.9 \pm 1.0$ \kms，给出了$R_{\rm A} = 1.28 \pm 0.04$ \rsun的主半径。我们的光变曲线分析得出了次级行星的半径$R_{\rm B} = 0.167 \pm 0.006$ \rsun和轨道的半长轴$a = 7.54 \pm 0.30 \rsun = 0.0351 \pm 0.0014$ AU。我们的单线光谱轨道和半长轴然后产生单独的质量，$M_{\rm B} = 0.124 \pm 0.010$ \msun和$M_{\rm A} = 1.04 \pm 0.13$ \msun。我们对HAT-TR-205-013 B的结果高于里昂群的理论质量半径模型，与双线食双星的结果一致。我们描述的方法提供了一个机会，研究非常低端的恒星质量半径关系。

英文摘要：

We derive masses and radii for both components in the single-lined eclipsing binary HAT-TR-205-013, which consists of a F7V primary and a late M-dwarf secondary. The system's period is short, $P=2.230736 \pm 0.000010$ days, with an orbit indistinguishable from circular, $e=0.012 \pm 0.021$. We demonstrate generally that the surface gravity of the secondary star in a single-lined binary undergoing total eclipses can be derived from characteristics of the light curve and spectroscopic orbit. This constrains the secondary to a unique line in the mass-radius diagram with $M/R^2$ = constant. For HAT-TR-205-013, we assume the orbit has been tidally circularized, and that the primary's rotation has been synchronized and aligned with the orbital axis. Our observed line broadening, $V_{\rm rot} \sin i_{\rm rot} = 28.9 \pm 1.0$ \kms, gives a primary radius of $R_{\rm A} = 1.28 \pm 0.04$ \rsun. Our light curve analysis leads to the radius of the secondary, $R_{\rm B} = 0.167 \pm 0.006$ \rsun, and the semimajor axis of the orbit, $a = 7.54 \pm 0.30 \rsun = 0.0351 \pm 0.0014$ AU. Our single-lined spectroscopic orbit and the semimajor axis then yield the individual masses, $M_{\rm B} = 0.124 \pm 0.010$ \msun and $M_{\rm A} = 1.04 \pm 0.13$ \msun. Our result for HAT-TR-205-013 B lies above the theoretical mass-radius models from the Lyon group, consistent with results from double-lined eclipsing binaries. The method we describe offers the opportunity to study the very low end of the stellar mass-radius relation.

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