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arXiv 1802.00537astro-ph.SR
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LAMOST巡天中恒星的UV辐射I.目录

The UV Emission of Stars in LAMOST Survey I. Catalogs

Yu Bai, JiFeng Liu, James Wicker, Song Wang, JinCheng Guo, YuXiang Qin, Lin He, JianLing Wang, Yue Wu, YiQiao Dong, Yong Zhang, Yonghui Hou, Yuefei Wang, Zihuang Cao

摘要:

我们给出了LAMOST巡天中超过300万颗恒星的紫外星等,其中有2,202,116颗恒星被$GALEX$探测到。对于889,235颗未被发现的恒星,我们开发了一种方法来估计它们的上限星等。(FUV $-$ NUV)的分布表明,在我们的样本中,对于温度高于7000 K的恒星,颜色随有效温度的增加而下降,而对于温度较低的恒星,由于来自高于光球层的高层大气的辐射,颜色随有效温度的增加而下降的趋势消失。对于具有有效恒星参数的恒星,我们用合成模型光谱计算了UV超度,发现(FUV $-$ NUV)与$R'_{\mathrm{FUV}}$之间存在线性关系,晚型矮星的UV超度更高.在FUV和NUV的$GALEX$访问曝光中,分别有87,178和1,498,103颗恒星被探测到一次以上。我们利用量化的光度误差来确定紫外变化的统计特性,包括内在的变异性和天的时间尺度上的结构函数。在我们的样本中,可能的假阳性的总体发生率低于1.3%。计算了具有有效视差的恒星的UV绝对星等,这些视差可以作为NUV中可能的参考系。我们的结论是,与UV相关的颜色提供了很好的标准来区分M巨星和M矮星,在我们的样本中的RR天琴座星的变化比其他A和F星。

英文摘要:

We present the ultraviolet magnitudes for over three million stars in the LAMOST survey, in which 2,202,116 stars are detected by $GALEX$. For 889,235 undetected stars, we develop a method to estimate their upper limit magnitudes. The distribution of (FUV $-$ NUV) shows that the color declines with increasing effective temperature for stars hotter than 7000 K in our sample, while the trend disappears for the cooler stars due to upper atmosphere emission from the regions higher than their photospheres. For stars with valid stellar parameters, we calculate the UV excesses with synthetic model spectra, and find that the (FUV $-$ NUV) vs. $R'_{\mathrm{FUV}}$ can be fitted with a linear relation and late-type dwarfs tend to have high UV excesses. There are 87,178 and 1,498,103 stars detected more than once in the visit exposures of $GALEX$ in the FUV and NUV, respectively. We make use of the quantified photometric errors to determine statistical properties of the UV variation, including intrinsic variability and the structure function on the timescale of days. The overall occurrence of possible false positives is below 1.3\% in our sample. UV absolute magnitudes are calculated for stars with valid parallaxes, which could serve as a possible reference frame in the NUV. We conclude that the colors related to UV provide good criteria to distinguish between M giants and M dwarfs, and the variability of RR Lyrae stars in our sample is stronger than that of other A and F stars.

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