发现962颗超冷矮星，揭示其磁活动与自转关系。
Magnetic activity of ultracool dwarfs in the LAMOST DR11
- 用自编码器半监督学习识别超冷矮星，模拟未来巡天能力。
- 82颗矮星测得自转周期，磁活动在罗斯比数0.12处饱和。
- 为理解低质量恒星磁生成机制提供新样本和观测依据。
超冷矮星包括质量最低的恒星和棕矮星，其内部完全对流，与部分对流的太阳类恒星不同，其磁场生成机制仍不明确。为显著扩充活跃超冷矮星样本，我们利用最新的LAMOST数据发布（DR11）识别出962颗超冷矮星。通过降采样LAMOST光谱模拟中国空间站巡天望远镜（CSST）低分辨率无狭缝光谱，构建基于自编码器的半监督机器学习方法，验证了CSST全天空无狭缝光谱巡天探测超冷矮星的能力。以Hα发射线作为磁活动代理，研究其磁活动特性；基于开普勒/K2光变曲线，推导出82颗超冷矮星的自转周期，获得其活动-自转关系，表明该关系在罗斯比数约0.12处达到饱和。
原文摘要 · Abstract (English)
Ultracool dwarfs consist of lowest-mass stars and brown dwarfs. Their interior is fully convective, different from that of the partly-convective Sun-like stars. Magnetic field generation process beneath the surface of ultracool dwarfs is still poorly understood and controversial. To increase samples of active ultracool dwarfs significantly, we have identified 962 ultracool dwarfs in the latest LAMOST data release, DR11. We also simulate the Chinese Space Station Survey Telescope (CSST) low-resolution slitless spectra by degrading the LAMOST spectra. A semi-supervised machine learning approach with an autoencoder model is built to identify ultracool dwarfs with the simulated CSST spectra, which demonstrates the capability of the CSST all-sky slitless spectroscopic survey on the detection of ultracool dwarfs. Magnetic activity of the ultracool dwarfs is investigated by using the H$α$ line emission as a proxy. The rotational periods of 82 ultracool dwarfs are derived based on the Kepler/K2 light curves. We also derive the activity-rotation relation of the ultracool dwarfs, which is saturated around a Rossby number of 0.12.
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