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: 2018
• 资助国家: 加拿大
• 起止时间: 2018-01-01 至 2019-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=665998
• 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的寿命只有几百万年，但却对其周围介质产生强烈影响。这些发光而炽热的恒星诞生于分子云深处，甚至在完全形成之前，就产生了一股强风，这种风持续存在于它们演化的所有阶段。通过这些流出物，它们对气体进行化学富集，并赋予其大量的能量和动量。这会在周围的介质中留下喷射星云和风吹气泡形式的信息丰富的印记，这些印记追踪了恒星在经历各种演化阶段，然后以壮观的超新星爆炸结束其生命时的质量损失历史。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中发挥关键作用。 ******我主要研究沃尔夫拉叶（WR）恒星，这些恒星是已经达到核心氦燃烧阶段的大质量恒星。我对约 20% 的大型结构在风中形成的结构特别感兴趣，这些结构被称为“共旋转相互作用区域”(CIR)。当其底部的扰动产生不同速度的区域时，这些区域在辐射驱动流中形成，这些区域在恒星旋转时发生碰撞，产生一个大型螺旋状结构，其中包含与周围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，这些结构还会影响恒星的角动量，从而影响其演化。我的目标是通过密集的监测活动来识别更多具有 CIR 的 WR 恒星（仅确认了三颗），我还将从中描述它们的特性。为此，我致力于理论方面的研究，使我能够更准确地解释观察结果。一旦识别出更多具有 CIR 的 WR 恒星，我将寻找各种物理恒星参数与其存在和属性之间的联系，以获取有关它们起源机制的知识。 ******我还将使用加拿大-法国-夏威夷望远镜上的宽视场光学成像傅里叶变换摄谱仪 SITELLE，以高空间范围和分辨率来表征 10 WR 恒星周围的星周介质 (CSM)。这种最先进的仪器非常适合获取 CSM 的灭绝、密度、温度和丰度图，可用于表征主层序和 WR 阶段之间的中间阶段发生的物质抛射的化学富集、不对称性和运动学特征。 大质量恒星的表面丰度及其 CSM 受到其演化过程中各种过程以及潮汐引起的混合或合并等二元效应的影响。通过将 CSM 特征与单星和双星模型进行比较，我将深入了解大质量恒星的演化，而对此许多方面仍然存在误解。**