Imaging Convective Patterns On AGB Stars

即使没有大气层造成的扭曲，我们分辨遥远物体空间结构的能力也受到望远镜反射镜直径的限制。 光学干涉仪，如格鲁吉亚州立大学的高角分辨率天文学中心（CHARA），通过将相距较远的小型望远镜接收到的信号结合起来，绕过了这一限制。 我们现在能够测量明亮恒星的大小和形状，我们开始能够拍摄它们的表面。 该团队将研究巨星表面的亮度变化，这是由表面下方的对流引起的。 反过来，这将使我们更好地了解这些恒星的“风”如何使星际介质变得更加丰富，从而形成未来的恒星（和行星）。该项目将用于培训格鲁吉亚州立大学的天文学、光学和计算机科学本科生。本计划的目标是利用CHARA对一组化学成分多样的渐近巨星分支（AGB）星进行长基线近红外干涉测量。 研究人员将在该项目的三年期间监测AGB对流模式的寿命、大小和变化。 然后，他们的表面有效温度图将与最先进的3D辐射流体动力学模型的预测进行比较，以确定高质量损失的区域，并确定质量如何通过恒星风分布回星际介质。 对不同类型的亚毫弧秒分辨率的AGB成像将有助于量化对流，脉动，多重性和磁性在可变性和质量损失过程中的作用。 PI还将举办讲习班，旨在帮助扩大能够获得和分析干涉观测的天文学家群体。 他们还将开发开放源代码，从干涉测量数据中生成各种恒星的图像。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

Even in the absence of distortions caused by our atmosphere, our ability to the resolve spatial structure of distant objects is limited by the diameter of telescope mirrors. Optical Interferometers, such as Georgia State University's Center for High Angular Resolution Astronomy (CHARA), get around this limitation by combining the signals received by smaller telescopes placed a long distance apart. We are now able to measure the sizes and shapes of bright stars, and we are beginning to be able to image their surfaces. This team will study the brightness variations on the surface of giant stars, which is caused by convection just beneath the surfaces. In turn, this will enable a better understanding of how the "winds" from these stars replenishes and enriches the interstellar medium, from which future generations of stars (and planets) are formed. This project will be used to train Georgia State University's undergraduate students in astronomy, optics, and computer science. The goal of this proposal is to image the surfaces of a group of chemically-diverse asymptotic giant branch (AGB) stars via long baseline near-IR interferometry using CHARA. The investigators will monitor the lifetime, size, and variability of the AGB convection patterns over the three-year duration of the project. Their maps of the surface effective temperatures will then be compared to predictions made by state-of-the-art 3D radiative-hydrodynamics models to determine regions of high mass-loss and to determine how that mass is distributed back into the interstellar medium via stellar winds. Imaging different types of AGBs with sub-milliarcsecond resolution will help quantify the roles of convection, pulsation, multiplicity and magnetism in the variability and mass-loss processes. The PI will also conduct workshops designed to help broaden the community of astronomers capable of obtaining and analyzing interferometric observations. They will also develop open source codes to produce images of a wide variety of stars from interferometric data.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.