High-resolution observational constraints on the astrophysics of near-circumstellar AGB environments

近周星 AGB 环境天体物理学的高分辨率观测约束

• 批准号: 0507473
• 负责人: Athol Kemball
• 金额: $ 28.77万
• 依托单位: University of Illinois at Urbana-Champaign
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2005
• 资助国家: 美国
• 起止时间: 2005-08-15 至 2009-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=0507473&HistoricalAwards=false
• 关键词: resolution; observational; constraints; astrophysics; near

AST-0507473Athol KemballUniversity of Illinois at Urbana-ChampaignHigh-resolution observational constraints on the astrophysics of nearcircumstellarAGB environmentsABSTRACTRecent instrumental advances on the Very Long Baseline Array, combined with new techniques formillimeter-wavelength polarimetry over the past decade, have opened a science window on thenear-circumstellar environment of evolved stars unmatched by any contemporary telescope. Thetechnique employed here allows the astrophysics of this region to be probed by the polarizationproperties of the silicon monoxide maser components located in the extended atmospheres viasynoptic imaging campaigns across complete pulsation periods of the central star. Here Very LongBaseline Array observations of maser emissions in the near-circumstellar regions of asymptoticgiant branch (evolved) stars will be carried out. The goal is to provide constraints on variousastrophysical models by: 1) measuring the magnitudes and orientation of magnetic fields in theextended atmospheres, 2) determining whether asymmetric mass loss begins at an early phase ofasymptotic giant branch evolution, and 3) exploring the possible connection between the centralstars and their close circumstellar environments. A series of specific research tasks (and associatedsub-tasks) are outlined which employ synoptic maser observations over entire pulsation cycles to(among other goals) map kinematics and shocks, to use polarization and population inversion toinfer magnetic fields and turbulence, and to discriminate between various models for polarizedmaser propagation and silicon oxide maser pumping. The latter studies are vital in order to provideunambiguous estimates of the surface magnetic fields in these stars. The results of this work areexpected to have an impact on studies of the physics of maser polarization, models of evolved starsand the process of planetary nebula formation.This work will help to train graduate students in the data reduction methods and analysis. Inaddition, the animated movies of maser emission toward late-type stars which are a by-product ofthis research, will be disseminated to the public through various outreach efforts. The final stepsnecessary to automate fully the existing calibration and imaging pipeline, which will be developedhere, will also be available to the community. This will sharply lower access barriers to the VeryLong Baseline Array.

AST-0507473 Athol Kemball伊利诺伊大学厄巴纳-香槟分校对近拱星AGB环境天体物理学的高分辨率观测约束摘要最近在甚长基线阵列上的仪器进展，结合过去十年中毫米波长偏振测量的新技术，为任何当代望远镜都无法比拟的演化恒星的近拱星环境打开了一扇科学窗口。这里采用的技术允许这个区域的天体物理学被探测的一氧化硅脉泽组件的偏振特性，位于扩展的大气层中，通过在整个中央星星的脉动周期的综合成像活动。在这里，甚长基线阵列将对渐近巨星分支（演化）星的近拱星区域的脉泽辐射进行观测。其目标是通过以下方式对各种天体物理模型提供约束：1）测量扩展大气中磁场的大小和方向，2）确定不对称质量损失是否始于渐近巨星分支演化的早期阶段，3）探索中心恒星与其周围环境之间的可能联系。概述了一系列具体的研究任务（和相关的子任务），其中采用天气脉泽观测整个脉动周期（除其他目标）映射运动学和冲击，使用偏振和人口反转推断磁场和湍流，并区分各种模型的polarizedmaser传播和氧化硅脉泽泵浦。后者的研究是至关重要的，以提供明确的估计，在这些恒星的表面磁场。这一工作将对脉泽偏振物理、演化恒星模型和行星状星云形成过程等方面的研究产生重要影响，有助于培养研究生掌握数据处理方法和分析能力。此外，作为这项研究的副产品，将制作向晚型恒星发射脉泽的动画电影，通过各种外联工作向公众传播。将在此处开发的现有校准和成像管道完全自动化所需的最后步骤也将提供给社区。这将大大降低进入超长基线阵列的障碍。