Imaging the Dynamic Atmospheres of Evolved Stars at Radio Wavelengths

老化的中低质量恒星将其质量的80%回收回星际介质。这是银河系中尘埃和重金属富集的主要来源，但对恒星质量损失过程的细节知之甚少。首席研究员（PI）马修斯和秋山将研究动态，质量损失的演变恒星的大气与卡尔G。Jansky甚大阵列（VLA）和阿塔卡马大型毫米/亚毫米阵列（阿尔马）。PI将开发和测试新的计算机算法，以提高图像分辨率，以便他们可以“看到”恒星无线电光球的新细节。PI将调查光球在数周到数月的时间尺度上的变化，以及发射恒星风的物理过程。新软件将发布给更广泛的天文学界，用于从原恒星盘和喷流到黑洞事件视界的成像研究。PI将与科学媒体专家合作，制作和分发三个关于“广播之星”的公共播客。这项工作的一个关键组成部分将是开发和测试基于正规化最大似然方法的新的高分辨率成像技术。由此产生的连续图像将能够测量基本的恒星参数（包括光球直径，形状和亮度温度），以及恒星表面特征的分辨成像和无线电光球长期变化的探索。同时观测邻近大气区域的光谱线将提供化学、密度、温度和气体运动学的补充诊断。这些结果将与模型预测进行比较，以提供新的见解对流，冲击和脉动的作用，在驱动演变的星星风。新的成像算法将在通用天文学软件应用程序（CASA）包中提供。为了让公众参与并扩大参与范围，该团队将在他们的播客中包括无线电数据的声音化。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。

Aging low-to-intermediate mass stars recycle up to 80% of their mass back to the interstellar medium. This is a primary source of dust and heavy metal enrichment in the Galaxy, yet the details of the stellar mass loss process are poorly understood. Principal Investigators (PIs) Matthews and Akiyama will study the dynamic, mass-losing atmospheres of evolved stars with the Karl G. Jansky Very Large Array (VLA) and the Atacama Large Millimeter/submillimeter Array (ALMA). The PIs will develop and test new computer algorithms to improve the image resolution so that they can “see” new details of the stellar radio photospheres. The PIs will investigate changes in the photospheres on timescales of weeks to months as well as the physical processes that launch the stellar wind. The new software will be released to the broader astronomical community for use in imaging studies ranging from protostellar disks and jets to black hole event horizons. The PIs will collaborate with science media specialists to produce and distribute three public podcasts about “Radio Stars”. A key component of this work will be the development and testing of new high-resolution imaging techniques based on regularized maximum likelihood methods. The resulting continuum images will enable measurements of fundamental stellar parameters (including photospheric diameters, shapes, and brightness temperatures), as well as resolved imaging of stellar surface features and the exploration of secular changes in the radio photospheres. Contemporaneous observations of spectral lines from adjacent atmospheric regions will provide complementary diagnostics of chemistry, density, temperature, and gas kinematics. These results will be compared with model predictions to provide new insights into the roles of convection, shocks, and pulsation in driving evolved star winds. The new imaging algorithms will be made available in the Common Astronomy Software Applications (CASA) package. To engage the public and broaden participation the team will include sonification of radio data in their podcasts.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.