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arXiv 0910.5571astro-ph.SR
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NP Aqr是新的近接触双星吗?

Is NP Aqr a new near-contact binary?

C. Ibanoglu, O. Cakirli, A. Dervisoglu

摘要:

我们提出的径向速度的双线光谱二进制NP Aqr。分别对依巴谷和ASAS-3的径向速度和光学光变曲线进行了分析。已发现一级和二级组分的质量分别为1.65 $\pm$ 0.09和0.99 $\pm$ 0.05 M $_{\odot}$。交叉关联函数显示出三个峰,表明存在第三恒星.这个附加成分的光谱特性类似于主星。对光变曲线的分析表明,质量更大的主星充满了相应的洛希瓣。第二分量位于洛希瓣或其附近,表明是一个新的$β$天琴座型近接触双星。轨道倾角约为40 $^{\circ}$,因此,观测到的光变化仅由邻近效应产生。由于没有日食,因此无法精确测定副星的有效温度和各组成部分的半径。我们认为NP Aqr是一颗距离约为134 $\pm$ 7 pc的非食双线分光双星。还将各组分的绝对参数与演化模型进行了比较。虽然主星的位置在赫兹-罗素图中的质量似乎是合适的,但副恒星的位置就好像是一颗质量小于0.6 M $_{\odot}$的恒星。这种差异源于非常低的有效温度,仅由邻近效应产生的光变曲线确定。它与第三颗恒星的距离似乎非常接近于近距离双星,这表明它可能是动态地被束缚在双星系统中。

英文摘要:

We present radial velocities of the double-lined spectroscopic binary NP Aqr. The radial velocities and the optical light curves obtained by Hipparcos and ASAS-3 are analyzed separately. The masses of the primary and secondary components have been found to be 1.65$\pm$0.09 and 0.99$\pm$0.05 M$_{\odot}$, respectively. The cross-correlation functions indicate triple peaks which show presence of a tertiary star. The spectroscopic properties of this additional component resemble to that of the primary star. The analysis of the light curves yielded that the more massive primary star fills its corresponding Roche lobe. The secondary component is at or near Roche lobe indicating a new $β$ Lyrae-type near-contact binary. The orbital inclination is about 40$^{\circ}$ and, therefore, the observed light variations are produced only by the proximity effects. Due to the absence of eclipses, the effective temperature of the secondary star and the radii of the components could not be determined accurately. We conclude that NP Aqr is a non-eclipsing double-lined spectroscopic binary with a distance of about 134$\pm$7 pc. The absolute parameters of the components are also compared with the evolutionary models. While the location of the primary star seems to be suitable with respect to its mass in the Hertzsprung-Russell diagram, the secondary component is located as if a star having a mass less than 0.6 M$_{\odot}$. This discrepancy is originated from very low effective temperature determined only from the light curve produced by proximity effects. The distance to the third star appears to be very close to that of the close binary which indicates that it may be dynamically bounded to the binary.

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