关于β-Picture星协中磁活性WW Psa和TX Psa成员的年龄
On the age of the magnetically active WW Psa and TX Psa members of the beta Pictoris association
摘要:
有各种不同的技术可用于估计前主序星的年龄。物理对的组成部分,由于其严格的coevality和质量差,如本文分析的二元系统,最适合测试这些不同技术的有效性。我们认为系统WW Psa + TX Psa的成员25百万年的beta Picasso协会已经很好地建立了早期的作品。我们调查的年龄测定技术提供了最好的协议之间的年龄的系统和协会。我们对WW Psa和TX Psa进行了光度监测,测得它们的自转周期分别为P = 2.37d和P = 1.086d。我们从文献中检索了它们的Li等效宽度,并测量了它们的有效温度和光度。我们调查是否这些恒星的年龄使用三个独立的技术得出的β Picasso协会的年龄是一致的。我们发现这两颗星的自转周期和Li含量与星团中其他真正成员的分布是一致的。相反,等时线拟合结果显示两颗恒星的年龄相似,但比星协的年龄年轻约4倍,如果将磁场的影响计算在内,则年轻约30%。我们探讨的起源不一致的年龄推断等时拟合,包括可能性,无论是两个组件可能是未解决的双星或两个组件的基本恒星参数被改变增强的磁活动。后者被认为是更合理的原因,这表明锂含量的基础上的年龄估计是更可靠的比等时线拟合前主序星具有明显的磁活动。
英文摘要:
There are a variety of different techniques available to estimate the ages of pre-main-sequence stars. Components of physical pairs, thanks to their strict coevality and the mass difference, such as the binary system analysed in this paper, are best suited to test the effectiveness of these different techniques. We consider the system WW Psa + TX Psa whose membership of the 25-Myr beta Pictoris association has been well established by earlier works. We investigate which age dating technique provides the best agreement between the age of the system and that of the association. We have photometrically monitored WW Psa and TX Psa and measured their rotation periods as P = 2.37d and P = 1.086d, respectively. We have retrieved from the literature their Li equivalent widths and measured their effective temperatures and luminosities. We investigate whether the ages of these stars derived using three independent techniques are consistent with the age of the beta Pictoris association. We find that the rotation periods and the Li contents of both stars are consistent with the distribution of other bona fide members of the cluster. On the contrary, the isochronal fitting provides similar ages for both stars, but a factor of about four younger than the quoted age of the association, or about 30% younger when the effects of magnetic fields are included. We explore the origin of the discrepant age inferred from isochronal fitting, including the possibilities that either the two components may be unresolved binaries or that the basic stellar parameters of both components are altered by enhanced magnetic activity. The latter is found to be the more reasonable cause, suggesting that age estimates based on the Li content is more reliable than isochronal fitting for pre-main-sequence stars with pronounced magnetic activity.
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