POWRE: Direct Impact Accretion in Interacting Binary Star Systems

恒星的直接撞击吸积发生在相互作用的双星系统中，即algol型双星。这些系统包含一颗B-A型主序星和一颗充满罗氏叶的F-K型巨星或亚巨星伴星。在短周期的大羊座恒星中，来自低温部分的气体流与伴星表面直接接触。这种影响不会发生在长周期藻双星中，因为与双星的分离相比，它们更宽，质量增益器的半径相对较小。直接撞击产生的吸积结构范围从恒星表面的热点到被称为吸积环的近乎稳定的吸积盘。利用多普勒断层成像观察这些双星的数据显示了沿着预测的质量传递流的引力路径的氢- α吸积的证据。这种独特的图像在整个相互作用的双星中是独一无二的，因为algol处于传质的缓慢阶段，因此提供了一个捕捉传质过程的机会。一些短周期藻藻具有稳定的吸积结构，而另一些则非常多变，它们在一个轨道周期内从流状分布转变为类似经典吸积盘的分布。理查兹博士通过氢α (h - α)波长和紫外光谱观察、多普勒断层扫描和流体动力学模拟研究了这些吸积结构。最近，理查兹博士完成了一项对18个大耳蛇型恒星系统的h - α光谱形态的重大研究。理查兹博士将从弗吉尼亚大学休学术假，到高级研究所进行休假访问。在休假期间，理查兹博士将能够利用类似紫外光谱研究的数据，以及在光学和紫外波长产生的多普勒断层图的比较，来加强以前研究的结果。本项目由数学和物理科学理事会天文科学司和多学科活动办公室资助

AST-0074586RichardsDirect impact accretion in stars occurs in the class of interacting binary star systems known as the Algol-type binary stars. These systems contain a type B-A main sequence star and a cool type F-K giant star or subgiant companion that fills its Roche lobe. In the short-period Algol stars, the gas flow from the cool component makes contact with the surface of the companion in a direct impact. This impact does not occur in the long-period Algols because they are wider and the radius of the mass gainer is relatively small when compared to the separation of the stars in the binary. The accretion structures produced by the direct impact range from a hot spot on the surface of the star to nearly stable accretion disks called accretion annuli. Data using Doppler tomogram observations of these binaries show evidence of Hydrogen-alpha accretion along the predicted gravitational path of the mass transfer stream. Such distinct images are unique among the entire class of interacting binaries because the Algols are in the slow phase of mass transfer and hence provide an opportunity to capture the process of mass transfer in action. Some short-period Algols have stable accretion structures while others are quite variable and they change within an orbital cycle from a stream-like distribution to one which resembles a classical accretion disk. Dr. Richards has studied these accretion structures by means of Hydrogen-alpha (H-alpha) wavelength and ultraviolet spectroscopy observations, Doppler tomography, and hydrodynamic simulations. Recently, Dr. Richards completed a major study of the H-alpha spectroscopic morphologies of 18 Algol-type star systems. Dr. Richards will take academic leave from the University of Virginia to go to the Institute of Advanced Studies for a sabbatical visit. Dr. Richards will be able to work on enhancing the results from the previous research, during the sabbatical period, by using data from similar studies of ultraviolet spectra and the comparison of Doppler tomograms generated at both optical and ultraviolet wavelengths.This project is funded by the Division of Astronomical Sciences and the Office of Multidisciplinary Activities in the Mathematical and Physical Sciences Directorate.***