Behavior of Li abundances in solar-analog stars - II. Evidence of the connection with rotation and stellar activity
Behavior of Li abundances in solar-analog stars - II. Evidence of the connection with rotation and stellar activity
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DOI：
10.1051/0004-6361/200913897
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发表时间：
2010-03
影响因子：
6.5
通讯作者：
Yoichi Takeda;S. Honda;S. Kawanomoto;H. Ando;Takashi Sakurai
中科院分区：
文献类型：
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作者：
Yoichi Takeda;S. Honda;S. Kawanomoto;H. Ando;Takashi Sakurai
语境。我们之前试图确定为什么类太阳恒星的 Li i 6708 线强度差异如此之大，尽管恒星参数表面上相似。我们对118个太阳类似物进行了综合分析，发现Li丰度（ALi）与线展宽宽度（vr+m；主要由旋转效应贡献）之间存在密切联系，这使我们得出结论，恒星旋转可能是表面Li含量的主要控制因素。目标。为了更详细地检验我们的主张，我们研究了恒星活动程度是否与锂丰度表现出类似的相关性，这是预期的，因为人们普遍认为自转和活动之间存在密切联系。方法。我们使用该近红外区域新获取的光谱测量了强 Ca ii 8542 线 r0(8542) 线中心的残余通量，r0(8542) 已知是恒星活动的有用指标。预计旋转速度 (ve sini )w 是通过从我们已经建立的 vr+m 中减去宏湍流贡献来估计的。结果。正如预期的那样，在 ALi 与（vs.）r0(8542) 图以及 r0(8542) 与 ve sini 和 ALi 与 ve sini 图中发现了显着的（正）相关性。随着旋转依赖性恒星活动的确认，这清楚地表明这些太阳类似物的表面锂丰度随着旋转速率的降低而逐渐减少。结论。鉴于这些观测证据，我们得出的结论是，太阳型恒星表面锂的消耗，可能是由有效的包层混合引起的，随着恒星自转减速，其运行效率更高。将行星宿主 G 矮星的低 Li 趋势归因于它们在恒星角动量方面的不同性质可能是有希望的。
Context. We previously attempted to ascertain why the Li i 6708 line-strengths of Sun-like stars differ so significantly despite the superficial similarities of stellar parameters. We carried out a comprehensive analysis of 118 solar analogs and reported that a close connection exists between the Li abundance (ALi) and the line-broadening width (vr+m; mainly contributed by rotational effect), which led us to conclude that stellar rotation may be the primary control of the surface Li content. Aims. To examine our claim in more detail, we study whether the degree of stellar activity exhibits a similar correlation with the Li abundance, which is expected because of the widely believed close connection between rotation and activity. Methods. We measured the residual flux at the line center of the strong Ca ii 8542 line, r0(8542), known to be a useful index of stellar activity, for all sample stars using newly acquired spectra in this near-IR region. The projected rotational velocity (ve sini )w as estimated by subtracting the macroturbulence contribution from vr+m that we had already established. Results. A remarkable (positive) correlation was found in the ALi versus (vs.) r0(8542) diagram as well as in both the r0(8542) vs. ve sini and ALi vs. ve sini diagrams, as had been expected. With the confirmation of rotation-dependent stellar activity, this clearly shows that the surface Li abundances of these solar analogs progressively decrease as the rotation rate decreases. Conclusions. Given this observational evidence, we conclude that the depletion of surface Li in solar-type stars, probably caused by effective envelope mixing, operates more efficiently as stellar rotation decelerates. It may be promising to attribute the low-Li tendency of planet-host G dwarfs to their different nature in the stellar angular momentum.