Massive Stars as Cosmic Engines

作为宇宙引擎的大质量恒星

• 批准号: RGPIN-2016-04385
• 负责人: Moffat, Anthony
• 金额: $ 1.97万
• 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=681891
• 关键词: Massive; Stars; Cosmic; Engines

My research is directed to the determination of the properties of massive stars. Such stars have initial masses above 8 times solar. They eventually fuse elements in successively smaller shells in their cores right through to iron, leading to sudden collapse accompanied by explosion of matter outside the core in the form of a supernova (SN). Although rare, massive stars deliver back to their surroundings far more than their share of radiation and enriched nuclear material for most of their relatively short lifetimes, both from their strong winds and their final SN. This makes them major contributors to the ecology and energetics of the Universe. In this proposal, I will concentrate on the following specific GOALS : *** (1) Search for and quantify pulsation and rotation properties in luminous massive stars using the recently launched international array of nanosatellites, BRITE-Constellation - a Canadian-driven first in astronomy. Despite their small 30 mm telescopes, all of the five functioning car-battery size BRITE nanosats can obtain precision dual-band photometric time-series (1 mmag rms) of all stars in the sky down to 4-6th magnitude on an hourly basis for up to 6 months. First results from BRITE are already beginning to revolutionize what we know about the properties of massive stars.*** (2) Recent evidence has revealed that virtually all massive stars form in binaries. In the closer systems, gravitational tidal effects lead to Roche-lobe overflow (RLOF) from one star to the other, actively seen in only a handful of systems. I will carry out a more systematic test of RLOF by quantifying the rotation speeds of O companions in WR+O binaries: the closest systems should have spun-up O-stars from the RLOF process. This effective test will have repercussions in all of stellar astrophysics.*** (3) Resolve an outstanding fundamental puzzle: dust formation in the hostile radiation fields of hot-star winds. This will be approached in various ways, including zeroing in on the WC9d star WR112 with ALMA in the sub-mm range, and following the Rosetta stone colliding-wind and episodic dust-forming binary WR140 using the CHARA interferometer in the NIR K-band.*** (4) Continue to search for and quantify the fundamental properties of the most massive stars in the local Universe. This must be done using Kepler's laws in binaries as the only viable method with minimum assumptions. Masses over 100 solar have already been found for the first time in some cases, with more to be examined. Such information is needed to constrain star formation both locally and in the early Universe, where massive stars are believed to dominate.*** (5) Continue large-scale surveys to locate large numbers of cWR stars (direct descendants of massive H-burning main-sequence stars above 25 solar masses) as immediate progenitors of type Ib/c SNe. Such a direct link has never been made before, yet is required to make progress in understanding the most exotic stellar deaths.**

我的研究方向是确定大质量恒星的性质。这类恒星的初始质量超过8倍太阳质量。它们最终将核心中不断变小的壳层中的元素融合成铁，导致突然坍塌，伴随着核心外物质的爆炸，形成超新星（SN）。 虽然罕见，但大质量恒星在其相对较短的寿命中，从强风和最终SN中返回到周围环境的辐射和浓缩核材料远远超过其份额。 这使它们成为宇宙生态学和能量学的主要贡献者。在本提案中，我将集中讨论以下具体目标：***（1）利用最近发射的国际纳米卫星阵列----英国星座----在天文学领域率先由英国人驱动，对发光大质量恒星的脉动和旋转特性进行搜索和量化。 尽管他们的小型30毫米望远镜，所有五个功能汽车电池大小的BRITE纳米卫星都可以获得精确的双波段光度时间序列（1 mmag rms）的所有恒星在天空中每小时下降到4- 6等，长达6个月。 BRITE的第一个结果已经开始彻底改变我们对大质量恒星性质的认识。(2)最近的证据显示，几乎所有的大质量恒星都是以双星的形式形成的。在较近的系统中，引力潮汐效应导致从一颗星星到另一颗恒星的罗氏瓣溢出（RLOF），这种现象只在少数系统中出现。我将通过量化WR+O双星中O伴星的旋转速度来对RLOF进行更系统的测试：最接近的系统应该有来自RLOF过程的旋转O星。这个有效的测试将对所有恒星天体物理学产生影响。(3)解决了一个突出的基本难题：热星风的有害辐射场中的尘埃形成。 这将以各种方式进行，包括使用亚毫米范围的阿尔马对WC 9d星星WR 112进行归零，以及使用近红外K波段的CHARA干涉仪跟踪罗塞塔石碑碰撞风和偶发尘埃形成双星WR 140。 (4)继续寻找和量化本地宇宙中最大质量恒星的基本性质。 这必须使用开普勒定律在二进制作为唯一可行的方法与最小的假设。在某些情况下，已经首次发现了超过100个太阳的质量，还有更多的有待检查。需要这些信息来限制星星的形成，无论是在局部还是在早期宇宙中，大质量恒星被认为占主导地位。 (5)继续进行大规模的巡天，以定位大量cWR星（大于25太阳质量的大质量H燃烧主序星的直接后代）作为Ib/c SNe的直接祖先。这种直接的联系以前从未被发现过，但在理解最奇特的恒星死亡方面取得进展是必要的。