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高偏心前主序列光谱双星RX J0529 .3+1210

The Highly Eccentric Pre-Main Sequence Spectroscopic Binary RX J0529.3+1210

G. N. Mace, L. Prato, L. H. Wasserman, G. H. Schaefer, O. G. Franz, M. Simon

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摘要：

年轻的系统RX J0529.3+1210最初被确认为单线光谱双星。使用高分辨率的红外光谱，获得与NIRSPEC凯克II，我们测量了径向速度的次级。利用红外区将单线光谱转换为双线光谱，并导出双星系统质量比的方法，已成功地用于一些年轻的低质量双星。对于长周期（462天）、高偏心率（0.88）的双星系统RX J 0529.3 +1210，在全轨道解中，我们仅用红外双线速度数据确定其质量比为0.78 ± 0.05，结合可见光和红外数据确定其质量比为0.73 ± 0.23。后者的不确定性很大是由于红外线的稀疏采样和高离心率：恒星在其大约1.3年的轨道上的大部分时间里没有大的速度分离。接近1的质量比（与该质量比值的一西格玛不确定度的高端一致）与缺乏次要成分的可见光检测不一致。我们概述了几个场景中的两颗恒星的颜色差异，如一个严重的斑点组件，高阶多重性，或一个独特的演化阶段，有利于检测只有主星在可见光，即使在质量比~1系统。然而，有证据表明比率较低。虽然RX J0529.3+1210在近红外波长下没有表现出过量，但检测到24微米的小过量，与环双星尘埃一致。讨论了这一双星的性质及其在λ Ori中的成员资格与附近一个新的恒星运动群在~90 pc。我们推测这个不寻常的系统的起源，以及这种高离心率对行星形成的可能性的影响。

英文摘要：

The young system RX J0529.3+1210 was initially identified as a single-lined spectroscopic binary. Using high-resolution infrared spectra, acquired with NIRSPEC on Keck II, we measured radial velocities for the secondary. The method of using the infrared regime to convert single-lined spectra into double-lined spectra, and derive the mass ratio for the binary system, has been successfully used for a number of young, low-mass binaries. For RX J0529.3+1210, a long- period(462 days) and highly eccentric(0.88) binary system, we determine the mass ratio to be 0.78+/-0.05 using the infrared double-lined velocity data alone, and 0.73+/-0.23 combining visible light and infrared data in a full orbital solution. The large uncertainty in the latter is the result of the sparse sampling in the infrared and the high eccentricity: the stars do not have a large velocity separation during most of their ~1.3 year orbit. A mass ratio close to unity, consistent with the high end of the one sigma uncertainty for this mass ratio value, is inconsistent with the lack of a visible light detection of the secondary component. We outline several scenarios for a color difference in the two stars, such as one heavily spotted component, higher order multiplicity, or a unique evolutionary stage, favoring detection of only the primary star in visible light, even in a mass ratio ~1 system. However, the evidence points to a lower ratio. Although RX J0529.3+1210 exhibits no excess at near-infrared wavelengths, a small 24 micron excess is detected, consistent with circumbinary dust. The properties of this binary and its membership in Lambda Ori versus a new nearby stellar moving group at ~90 pc are discussed. We speculate on the origin of this unusual system and on the impact of such high eccentricity on the potential for planet formation.

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