Studying Wolf-Rayet Stars Using Their Wind Structure and Circumstellar Nebula

利用风结构和星周星云研究沃尔夫拉叶星

• 批准号: RGPIN-2018-05034
• 负责人: StLouis, Nicole
• 金额: $ 3.5万
• 依托单位: Université de Montréal
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=763440
• 关键词: Studying; Wolf; Rayet; Stars; Using

The most massive stars in the Universe live only a few million years but have a strong impact on their surrounding medium. These luminous and hot stars are born deep in molecular clouds and, even before being fully formed, develop a strong wind, which persists in all phases of their evolution. Through these outflows, they chemically enrich the gas and impart to it a large amount of energy and momentum. This leaves in the surrounding medium information-rich imprints in the form of ejected nebula and wind-blown bubbles, which trace the mass-loss history of the star as it undergoes its various evolutionary phases before ending its life in a spectacular supernova explosion. These winds enable massive stars to play a pivotal role in governing the evolution of gas, dust and ultimately of stellar populations composing galaxies. I work principally on Wolf-Rayet (WR) stars, which are massive stars that have reached the core helium-burning phase. I am particularly interested in large-scale structures that form in the winds of ~20% of them, called Corotating Interaction Regions (CIRs). These form in radiation driven flows when a perturbation at their base generates regions of different velocities that collide when the star rotates, producing a large spiral-like structure encompassing zones of higher and lower densities and velocities compared to the ambient wind. In addition to the fact that the source of the perturbations is unknown (magnetic, pulsations), these structures have an impact on the angular momentum of the star, which affects its evolution. My goal is to identify more WR stars with CIRs (only three are confirmed) using intense monitoring campaigns, from which I will also characterize their properties. To do this, I work on theoretical aspects that enable me to more accurately interpret the observations. Once more WR stars with CIRs are identified, I will search for links between various physical stellar parameters and their presence and properties to gain knowledge on the mechanisms from which they originate. I will also use the wide-field optical imaging Fourier-Transform Spectrograph, SITELLE, on the Canada-France-Hawaii Telescope to characterize with high spatial extent and resolution, the circumstellar medium (CSM) around 10 WR stars. This state-of-the-art instrument is ideal to obtain maps of the extinction, density, temperature and abundances of the CSM, which can be used to characterize the chemical enrichment, asymmetries and kinematics of the mass ejections that occurred in the intermediate phases between the main sequence and WR stages. The surface abundances of massive stars and thus their CSM are affected by various processes during their evolution and by binary effects such as tidally induced mixing or mergers. By comparing the CSM characteristics with models of single and binary stars, I will gain insight into massive-star evolution for which many aspects still remain misunderstood.

宇宙中质量最大的恒星寿命只有几百万年，但对周围的介质有很大的影响。这些明亮而炽热的恒星诞生于分子云深处，甚至在完全形成之前，就形成了强风，这种强风在它们演化的各个阶段都存在。通过这些流出，它们以化学方式富集气体，并赋予其大量的能量和动量。这在周围的介质中留下了以喷射星云和风吹气泡形式存在的信息丰富的印记，这些印记追踪了星星在以壮观的超新星爆炸结束其生命之前经历的各个演化阶段的质量损失历史。这些风使大质量恒星在控制气体、尘埃以及最终组成星系的恒星群的演化方面发挥着关键作用。我主要研究沃尔夫-拉叶星（WR），这是已经达到核心氦燃烧阶段的大质量恒星。我特别感兴趣的是在其中20%的风中形成的大型结构，称为共转相互作用区（CIR）。当它们底部的扰动产生不同速度的区域时，这些区域在辐射驱动的气流中形成，当星星旋转时碰撞，产生一个大的螺旋状结构，包括与环境风相比密度和速度较高和较低的区域。除了扰动来源未知（磁、脉动）之外，这些结构还会影响星星的角动量，从而影响其演化。我的目标是使用密集的监测活动来识别更多具有CIR的WR星（只有三个被确认），从中我也将描述它们的属性。为了做到这一点，我在理论方面的工作，使我能够更准确地解释观察。一旦更多的WR星与CIR被确定，我将寻找各种物理恒星参数和它们的存在和属性之间的联系，以获得有关它们起源的机制的知识。我还将使用宽视场光学成像傅里叶变换摄谱仪，SITELLE，在加拿大-法国-夏威夷望远镜的特点与高空间范围和分辨率，拱星介质（CSM）周围的10个WR星。这种最先进的仪器非常适合获得CSM的消光、密度、温度和丰度的地图，这些地图可用于表征在主层序和WR阶段之间的中间阶段发生的质量喷射的化学富集、不对称性和运动学。 大质量恒星的表面丰度以及它们的CSM受到演化过程中各种过程的影响，也受到潮汐引起的混合或合并等双星效应的影响。通过比较CSM的特点与单星和双星模型，我将深入了解恒星演化的许多方面仍然存在误解。