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: 2016
• 资助国家: 加拿大
• 起止时间: 2016-01-01 至 2017-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=615029
• 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特性。这些恒星的初始质量超过太阳的 8 倍。它们最终将其核心中逐渐变小的壳层中的元素融合成铁，导致突然塌缩，并伴随着核心外物质以超新星（SN）的形式爆炸。尽管罕见，但大质量恒星在其相对较短的生命周期的大部分时间里，通过其强风和最终的超临界状态，向周围环境释放出的辐射和浓缩核材料远远超过其所占份额。这使它们成为宇宙生态和能量学的主要贡献者。在本提案中，我将重点关注以下具体目标： (1) 使用最近发射的国际纳米卫星阵列 BRITE-Constellation 搜索并量化发光大质量恒星的脉动和旋转特性，这是加拿大主导的天文学首创。尽管它们的望远镜只有 30 毫米小，但所有五个功能正常的汽车电池大小的 BRITE 纳米卫星都可以每小时获得天空中低至 4-6 等星的所有恒星的精确双波段光度时间序列 (1 mmag rms)，持续时间长达 6 个月。 BRITE 的初步结果已经开始彻底改变我们对大质量恒星特性的了解。 (2) 最近的证据表明，几乎所有大质量恒星都是在双星中形成的。在距离较近的系统中，引力潮汐效应会导致从一颗恒星到另一颗恒星的洛希瓣溢出（RLOF），这种现象仅在少数系统中活跃可见。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：最近的系统应该有来自 RLOF 过程的旋转的 O 星。这项有效的测试将对所有恒星天体物理学产生影响。 （3）解决一个突出的基本难题：热星风的不利辐射场中尘埃的形成。我们将通过多种方式来实现这一目标，包括使用亚毫米范围内的 ALMA 瞄准 WC9d 恒星 WR112，以及使用近红外 K 波段的 CHARA 干涉仪追踪罗塞塔石碑碰撞风和偶发性尘埃形成双星 WR140。 （4）继续寻找并量化本地宇宙中最大质量恒星的基本特性。这必须使用双星中的开普勒定律作为唯一可行的方法和最少的假设来完成。在某些情况下，首次发现了超过 100 个太阳质量的质量，还有更多质量有待检查。需要这些信息来限制局部和早期宇宙中的恒星形成，人们认为早期宇宙中大质量恒星占主导地位。 (5) 继续进行大规模调查，以定位大量 cWR 恒星（25 个太阳质量以上的大质量 H 燃烧主序星的直系后代），作为 Ib/c 型超新星的直接前身。这种直接联系以前从未建立过，但需要在理解最奇异的恒星死亡方面取得进展。