分类： 天文学 >> 天体物理学 提交时间： 2020-03-09
摘要： We present spectroscopy of stars in the immediate vicinity of the dwarf nova (DN) KZ Gem to confirm its identification, which had been ambiguous in the literature. Analysis of 73 radial velocities spanning from 2014 to 2019 provides a high-precision orbital period of 0.2224628(2) d (~5.34 hr) and shows KZ Gem to be a double-lined DN. Time series photometry taken from 2016 to 2018 shows a variable double-hump modulation with a full amplitude of ~0.3 mag, along with five Gaussian-like transient events lasting ~30 min or more. Using the light curve code XRBinary and nonlinear fitting code NMfit, we obtain an optimized binary model of the dwarf nova (DN) KZ Gem, from time series photometry, consisting of a Roche-lobe-filling K type dwarf with a mass transfer rate of 2.7 - 7.9 x 10^{-10} solar mass per yr to a large, cool and thick disk surrounding a white dwarf, in an orbit with an inclination of 51.6(+/-1.4) degree. Two hotspots on the disk are demonstrated to cause the observed variations in the ellipsoidal modulations from the secondary star. This physical model is compatible with the Gaia distance of KZ Gem.
分类： 天文学 >> 天文学 提交时间： 2020-03-07 合作期刊: 《天文研究与技术》
摘要： 通过添加太阳黑子周期长度构建长短期记忆网络（Long Short-Term Memory，LSTM)的多变量输入数据，在多时间步长上预测未来10年的太阳黑子变化。将数据集以训练数据长度为标准划分出两组时间序列片段，分别是分片11和分片6，并在分片上分别对比了单变量和多变量在单时间步长和多时间步长上的预测效果。最后，得出以下主要结论：(1)比起分片6，分片11的采样方式有更低的均方根误差(Root mean squared error,RMSE)；(2)最优多步长的预测效果比单步长的要好；(3)通过图例上周期的起始点、结束点和最大振幅位置三个点的准确度证明了多变量的多步长方法确实有更好的预测效果。
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