标题： 甲醇和水脉泽在G107.298+5.639中的周期性和交替爆发的发现 显示英文标题

标题： Discovery of periodic and alternating flares of the methanol and water masers in G107.298+5.639

摘要： 甲醇和水蒸气脉泽是大质量恒星形成早期阶段的标志，但通常认为由于不同的激发过程，它们探测的是恒星环境的不同部分。 在这里，我们展示了中间质量年轻恒星天体G107.298+5.639的观测结果，首次揭示了6.7 GHz甲醇脉泽发射的34.4天爆发与22 GHz水脉泽个别特征的爆发交替出现。 高角分辨率数据表明，两种脉泽物种的几个显示周期性行为的组分在位置和速度上一致，所有周期性的水脉泽组分都出现在大小为360 au的甲醇脉泽区域。 脉泽爆发可能是由围绕恒星或原双星盘中的周期性吸积不稳定性引起的红外辐射场变化造成的。 观测结果不支持恒星脉动或种子光子通量变化作为该源周期性的潜在机制。 显示英文摘要

摘要： Methanol and water vapour masers are signposts of early stages of high-mass star formation but it is generally thought that due to different excitation processes they probe distinct parts of stellar environments. Here we present observations of the intermediate-mass young stellar object G107.298+5.639, revealing for the first time that 34.4 d flares of the 6.7 GHz methanol maser emission alternate with flares of individual features of the 22 GHz water maser. High angular resolution data reveal that a few components of both maser species showing periodic behaviour coincide in position and velocity and all the periodic water maser components appear in the methanol maser region of size of 360 au. The maser flares could be caused by variations in the infrared radiation field induced by cyclic accretion instabilities in a circumstellar or protobinary disc. The observations do not support either the stellar pulsations or the seed photon flux variations as the underlying mechanisms of the periodicity in the source.