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: $ 1.75万
• 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: 2019
• 资助国家: 加拿大
• 起止时间: 2019-01-01 至 2020-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=680003
• 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.**

宇宙中最大质量的恒星只有几百万年的寿命，但却对周围的介质产生了强烈的影响。这些明亮而炽热的恒星在分子云深处诞生，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所有阶段都持续存在。通过这些外流，它们在化学上丰富了气体，并为其提供了大量的能量和动量。这在周围的介质中留下了以喷出的星云和被风吹起的气泡形式的丰富信息印记，这些印记追溯了恒星在经历各种演化阶段后在壮观的超新星爆炸中结束生命之前的质量损失历史。这些风使大质量恒星能够在控制气体、尘埃以及最终组成星系的恒星群的演化中发挥关键作用。*我主要研究Wolf-Rayet(WR)恒星，这是一种已经达到核心氦燃烧阶段的大质量恒星。我对其中约20%的风中形成的大型结构特别感兴趣，这种结构被称为协旋相互作用区(CIR)。当它们底部的扰动产生不同速度的区域时，恒星旋转时会发生碰撞，形成一个巨大的螺旋状结构，与周围的风相比，这些区域的密度和速度分别较高和较低，从而形成辐射驱动的流动。除了扰动的来源未知(磁性、脉动)之外，这些结构还对恒星的角动量产生影响，从而影响其演化。我的目标是通过密集的监控活动识别出更多具有CIRS的WR明星(只有三个得到确认)，我也将从这些活动中描述他们的特征。为了做到这一点，我致力于理论方面的工作，使我能够更准确地解释观察结果。一旦发现更多具有CIR的WR恒星，我将搜索各种物理恒星参数与它们的存在和性质之间的联系，以获得关于它们起源机制的知识。*我还将使用加拿大-法国-夏威夷望远镜上的广视场光学成像傅里叶变换光谱仪SITELLE来表征围绕10个WR恒星的星周介质(CSM)，具有高空间范围和高分辨率。这一最先进的仪器是获得CSM消光、密度、温度和丰度的理想地图，可以用来表征在主序列期和WR期之间的中间阶段发生的物质抛射的化学富集性、不对称性和运动学。大质量恒星及其CSM的表面丰度受其演化过程中的各种过程以及潮汐诱导的混合或合并等二元效应的影响。通过将CSM的特征与单星和双星的模型进行比较，我将深入了解大质量恒星的演化，其中许多方面仍然存在误解。