发表机构
ESO/ALMA; Jodrell Bank Centre for Astrophysics, University of Manchester; Center for Astrophysics and Space Astronomy, University of Colorado; Massachusetts Institute of Technology Haystack Observatory; Dublin Institute for Advanced Studies（欧洲南方天文台/阿塔卡马大型毫米波/亚毫米波阵列; 曼彻斯特大学乔德雷尔银行天体物理学中心; 科罗拉多大学天体物理学与空间天文中心; 麻省理工学院海斯塔克天文台; 都柏林高等研究院）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究借助ALMA高分辨率观测参宿四内部大气，发现其存在持久的热结构，推测与极区对流相关，气体发射结构较2015年显著变化，未观测到明确的恒星自转证据。
AI 中文摘要
红超巨星（RSG）的延伸大气是质量损失过程及后续星际介质增丰的重要环节，学界认为大尺度对流在此过程中发挥关键作用，可能导致恒星表面出现不规则结构。参宿四是距离地球最近的红超巨星之一，本研究利用ALMA最长基线配置获取其内部1-2R★大气结构及时间稳定性的高分辨率、高对比度亚毫米图像，观测覆盖λ0.6-1.4毫米波段的连续谱发射，以及SiO、CO及其同位素分子的谱线，最短波长处的波束宽度可达7毫角秒。研究将本次观测结果与约7年前（2015年）0.9毫米波段的同类观测进行对比。观测到的连续谱发射主要来自半径为1.1-1.3R★的光学厚毫米/亚毫米光球，其温度相对恒定，约2300K，但在东北和西南方向存在两个较热区域，其中最亮的热区域温度提升约800K，且其位置和强度自2015年观测以来相对未发生明显变化。亚毫米光球的半径偏差最高达±6%，较弱的连续谱发射延伸至约2.5R★，与SiO和CO的团块状发射范围相似。这些热气体区域及径向对称性偏差被认为与底层对流胞驱动的活跃激波相关，不过其寿命长于模型预测；它们位于恒星推测的极区附近，可能意味着极区对流增强且相对稳定。本次数据未在延伸谱线发射或光球吸收中发现恒星自转的明确证据，但气体发射结构自2015年以来已发生显著变化。
英文摘要
The extended atmosphere of red supergiants (RSGs) forms an important link in the process of mass loss and the subsequent enrichment of the interstellar medium. Large-scale convection is thought to play a significant role, which is likely to result in irregularities in the surface. High resolution, high contrast sub-mm images of Betelgeuse - one of the closest RSGs - are used to probe the structure and temporal stability of the inner 1-2$R_\star$ of its atmosphere. Using ALMA in the longest baseline configuration, continuum emission and lines of SiO and CO and their isotopomers were observed at $λ$0.6-1.4mm, giving beamwidths down to 7mas at the shortest wavelengths. These were compared with a similar observation taken at 0.9mm approximately 7 years earlier. The observed continuum emission arises mostly from an optically-thick mm/sub-mm photosphere of radius 1.1-1.3$R_\star$ with a relatively constant temperature of $\sim$2300K, but with two hotter patches to the NE and SW. The brightest of these has a temperature enhancement of $\sim$800K, and its location and intensity appears relatively unchanged since the 2015 observation. The sub-mm photosphere shows deviations of up to $\pm$ 6% in radius, with weaker continuum extending out to $\sim$2.5$R_\star$ - similar to the extent of clumpy emission in SiO and CO. The hot regions of gas and deviations from radial symmetry are thought to be associated with active shocks driven by underlying convective cells, although their lifetimes appear longer than model predictions. They lie near the proposed poles of the star, which might suggest enhanced and relatively stable polar convection. The present data show no clear evidence for stellar rotation in the extended line emission or absorption against the photosphere, although the structure of the gas emission has changed significantly since 2015.
Comments13 pages, 9 figure. Plus 6 pages appendices. Astronomy & Astrophysics, accepted
