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arXiv 1003.5796astro-ph.SR
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利用星震学确定HR8799行星系统的年龄

Age determination of the HR8799 planetary system using asteroseismology

A. Moya, P. J. Amado, D. Barrado, A. García Hernández, M. Aberasturi, B. Montesinos, F. Aceituno

摘要:

在HR8799周围直接成像发现了第一个行星系统,这使得确定主恒星的年龄成为一项非常重要的任务。这一确定是获得行星精确质量和研究系统动力学稳定性的关键。这颗恒星的年龄是用不同的方法估算出来的。在这项工作中,我们表明,这些程序中的一些问题和较大的不确定性,这颗恒星的真实年龄仍然是未知的,需要更多的观测约束。因此,我们已经开发了一个全面的建模HR8799,并利用其伽马剑鱼座型脉动,我们估计了恒星的年龄使用asteroseismology。年龄测定的精度取决于恒星的自转速度,因此需要一个准确的倾角值来解决这个问题。尽管如此,我们发现先前在文献中发表的这颗恒星的年龄估计([30,160] Myr)是不可能的,更准确的值可能更接近Gyr。这一确定对绕HR 8799轨道运行的物体的质量值有着深刻的影响。年龄在$\approx$ 1 Gyr左右意味着这些天体是棕矮星。

英文摘要:

Discovery of the first planetary system by direct imaging around HR8799 has made the age determination of the host star a very important task. This determination is the key to derive accurate masses of the planets and to study the dynamical stability of the system. The age of this star has been estimated using different procedures. In this work we show that some of these procedures have problems and large uncertainties, and the real age of this star is still unknown, needing more observational constraints. Therefore, we have developed a comprehensive modeling of HR8799, and taking advantage of its gamma Doradus-type pulsations, we have estimated the age of the star using asteroseismology. The accuracy in the age determination depends on the rotation velocity of the star, and therefore an accurate value of the inclination angle is required to solve the problem. Nevertheless, we find that the age estimate for this star previously published in the literature ([30,160] Myr) is unlikely, and a more accurate value might be closer to the Gyr. This determination has deep implications on the value of the mass of the objects orbiting HR8799. An age around $\approx$ 1 Gyr implies that these objects are brown dwarfs.

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