Collaborative Research: The Importance of Binarity on the Origin of Wolf-Rayet Stars

这个项目旨在演示大质量恒星如何失去其最外层，暴露出它们的核心。这样的天体被称为沃尔夫-瑞叶(WR)恒星。它们的大部分氢都消失了，它们由核燃烧的产物组成，如氦、碳和氧。WR恒星的寿命即将结束，它们注定会以壮观的超新星的形式爆炸。有两种方法可以形成这些WR。在第一个过程中，外层被“恒星风”移除，在恒星风中，物质被其强光的压力推离恒星。在第二种方法中，在一颗轨道上运行的伴星的引力作用下，物质被拉离恒星。很可能一些WR恒星以一种方式形成，而另一些则以另一种方式形成。这个项目的目标是找出每种方法形成的WR恒星的比例。这一结果将具有重要的科学意义，因为这些大质量恒星在宇宙生态中扮演着至关重要的角色，制造构成我们星球和地球上生命的元素。它们在生命末期的强烈爆炸将这些元素释放到太空中，触发了下一代恒星和行星的形成。这些观察还将为本科生提供暑期实习项目。该项目包括建造和免费分发大学级天文习题。调查组将使用三种互补的方法。首先，他们将测量富含氮的沃尔夫-瑞耶星(WN)的代表性样本的光度和化学成分，并将这些结果与进化模型预测的结果进行比较。其次，将研究神秘的“WN3/O3”恒星的性质。它们要么是剥离双星的原型，要么是O星和WR之间缺失的一环。第三，他们将对大小麦哲伦星云中的O型恒星进行系统调查。O星和WR星的相对数量是质量(光度)的函数，这是对WR起源的最基本的诊断之一。这三个程序加在一起，将对每种机制形成的二进制文件的比例进行编号和不确定性。作者还将构建一份包含1000颗明亮恒星的高分辨率光谱地图集，涵盖广泛的光谱类型和光度等级。这本地图集是一个启发式资源，不仅可供天文学家使用，也可供天文学专业学生使用。它将用于北亚利桑那大学的本科生实验室练习。这些光谱和教学单元将通过网站免费提供给每个人。这一奖项反映了NSF的法定使命，并通过使用基金会的智力优势和更广泛的影响审查标准进行评估，被认为值得支持。

This project is designed to demonstrate how high-mass stars lose their outermost layers, exposing their cores. Such objects are known as Wolf-Rayet (WR) stars. Most of their hydrogen is gone, and they are made up of the products of nuclear burning such as helium, carbon, and oxygen. WR stars are near the ends of their lives and are destined to explode as spectacular supernovae. There are two methods by which these WRs might form. In the first of these, the outer layers are removed by "stellar winds," in which matter is pushed off the star by the pressure of their intense light. In the second method, material is pulled off the star by the gravity of an orbiting companion star. It is likely that some WR stars form one way, while others form the other. The goal of this project is to find what fraction of WR stars is formed by each method. This result will be important scientifically, because these high-mass stars play a vital role in the ecology of the Universe, manufacturing the elements that make up our planet and the life on it. Their intense explosions at the ends of their lives release these elements into space, triggering the formation of the next generation of stars and planets. These observations will also provide summer internship projects for undergraduates. The project includes the construction and free distribution of college-level exercises in astronomy. The investigator team will use three complementary approaches. First, they will measure the luminosities and chemical composition of representative samples of nitrogen-rich Wolf-Rayet stars (WN) and compare these to those predicted by the evolutionary models. Second, the nature of the enigmatic "WN3/O3" stars will be investigated. These are either archetypes of stripped binaries or a missing link between O stars and WRs. Third, they will conduct a systematic survey for O-type stars in the Large and Small Magellanic Clouds. The relative number of O and WR stars as a function of mass (luminosity) is one of the most fundamental diagnostics of the origins of WRs. Together these three programs will put numbers and uncertainties on the fraction of binaries formed by each mechanism. The authors will also construct a high-resolution spectral atlas of 1000 bright stars covering a wide range of spectral types and luminosity classes. This atlas is intended as a heuristic resource available not only for astronomers but also for astronomy students. It will be used in undergraduate lab exercises at Northern Arizona University. These spectra and teaching units will then be made freely available to everyone through a website.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.