【丝路天文”讲坛第七十三讲】Transient events in star formation: phenomenology, physics and chemistry
时 间：2024年12月19日 11：00(星期四）
会议地点：台本部南楼210会议室
主 讲 嘉 宾： Andrey Sobolev 教授（俄罗斯乌拉尔联邦大学）
报 告 摘 要:
Surveys in the optics and near infrared have established the ubiquity of variability in the young stars visible in these ranges. However, objects at the earliest stages of protostellar growth are normally deeply embedded and can be observed only in the far infrared, submillimeter and millimeter ranges. Another advantage of the variability studies in these ranges is that such studies provide information on the luminosity changes rather than opacity effects. Monitoring of the low-mass-star forming regions within JCMT Transient Survey at 850 mkm have established that there are ubiquitous changes on the time scales of months and years which are attributed to the changes in accretion rates. Stochastic accretion variability is also detected. This is very valuable information for the studies of accretion phenomena. JCMT Transient Survey has also discovered a very short-term non-thermal variability event which was associated with magnetic field reconnection. Studies of such events are potential tool to study physical and chemical processes in the scale of the inner accretion disk to the stellar surface. Last few years are marked by exciting discoveries of the bright accretion bursts in the high-mass young stellar objects in S255IR, NGC6334I and G358.931-0.030. Remarkably, these events were accompanied by the maser emission. Maser Monitoring Organisation (M2O) plays a big role in these complex studies. These are some of obtained results: Observations show that the structure of the circumstellar disks of massive young stellar objects is significantly inhomogeneous. These disks contain coherent structures up to 1000 AU in size. Accretion of matter onto a young star occurs along some structures; these structures can be in the form of spirals. The material of accretion structures consists of clumps, the fallout of which on a young star leads to accretion bursts of various intensities A large amount of high density material is present in the structure of the disc, leading to a significant slowing-down in the propagation of light. After an accretion burst, the physico-chemical state of the disk matter changes and does not return to its previous state. Chemical changes are the most prominent in this case, just because characteristic times of chemical relaxation are much longer than those of the physical ones.
主讲嘉宾简介：
Andrey Sobolev，俄罗斯天文学家， 1984年获得苏联科学院天文学会博士学位。他致力于天体脉泽和恒星形成的研究。在脉泽理论研究领域，他创立了被广泛应用的甲醇脉泽抽运模型，该模型是第一个能够解释6.7 GHz和12.2 GHz极高亮温度甲醇脉泽的数值模型，也解释了强甲醇和羟基脉泽共存的现象，同时给出了不同甲醇脉泽跃迁亮度之间的普遍关系，以及预测了新的脉泽跃迁。另一个重要理论研究方向是对存在湍流速度场的介质中形成脉泽图像和光谱的数值模型，这些方法解释了脉泽变化的一些主要特征和脉泽图像的细微结构。他在国际著名学术期刊已发表200多篇科研论文。他在天体脉泽抽运模型、脉泽时变研究、分子云和恒星形成、天体化学等多个领域取得了重要成就。