High dispersion spectroscopy of solar-type superflare stars. III. Lithium abundances
High dispersion spectroscopy of solar-type superflare stars. III. Lithium abundances
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太阳型超耀斑恒星的高色散光谱。
DOI：
10.1093/pasj/psv054
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发表时间：
2015
影响因子：
2.3
通讯作者：
Kazunari
中科院分区：
文献类型：
--
作者：
Honda;Satoshi; Notsu;Yuta; Maehara;Hiroyuki; Notsu;Shota; Shibayama;Takuya; Nogami;Daisaku; Shibata;Kazunari
本文报道了利用开普勒测光资料分析发现的太阳型（G型主序星）超耀斑中Li的丰度。Li是理解恒星对流带演化的关键元素，它反映了太阳型恒星的年龄。我们利用Subaru/High Dispersion摄谱仪对太阳型超耀斑恒星进行了高色散光谱研究，确认了34颗恒星在我们之前的研究中没有双星的证据。在这项研究中，我们得出了这34个对象的锂丰度。我们研究了Li丰度与恒星大气参数、旋转速度和超级耀斑活动的相关性，以了解超级耀斑恒星的性质以及超级耀斑核合成Li的可能性。我们证实了大分散的锂丰度，与恒星参数的相关性是看不到的。与比太阳年轻的毕宿星团中的Li丰度相比，我们认为有一半的观测恒星比毕宿星团年轻。vsini（投影旋转速度）的测量值支持这些物体比太阳年轻。然而，也有一些对象，显示低Li丰度和缓慢旋转的基础上估计vsiniandP（亮度变化周期）。这一结果表明，超耀斑恒星不仅是年轻的恒星，也是像我们太阳一样的老恒星。在我们的观测中，我们没有发现任何由超级耀斑产生Li的证据。对超级耀斑恒星锂同位素丰度的进一步研究将澄清恒星耀斑产生锂的问题。
We report on the abundance analysis of Li in solar-type (G-type main sequence) superflare stars which were found by the analysis of Kepler photometric data. Li is a key element to understand the evolution of the stellar convection zone, which reflects the age of solar-type stars. We performed the high-dispersion spectroscopy of solar-type superflare stars with Subaru/High Dispersion Spectrograph and confirmed that 34 stars show no evidence of binarity in our previous study. In this study, we derived the Li abundances of these 34 objects. We investigate correlations of Li abundance with stellar atmospheric parameters, rotational velocity, and superflare activities to understand the nature of superflare stars and the possibility of the nucleosynthesis of Li by superflares. We confirm the large dispersion in the Li abundance, and the correlation with stellar parameters is not seen. When compared with the Li abundance in the Hyades cluster, which is younger than the Sun, it is suggested that half of the observed stars are younger than Hyades cluster. The measured value ofvsini(projected rotational velocity) supports that those objects are younger than the Sun. However, there are some objects which show the low Li abundance and slowly rotate on the basis of the estimatedvsiniandP(period of brightness variation). This result indicates that superflare stars are not only young stars but also old stars like our Sun. In our observations, we could not find any evidence of Li production by superflares. Further research on Li isotope abundances of superflare stars would clarify the issue of Li production by stellar flares.