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Pulsating white dwarfs: new insights
The Astronomy and Astrophysics Review ( IF 27.8 ) Pub Date : 2019-09-03 , DOI: 10.1007/s00159-019-0118-4
Alejandro H. Córsico , Leandro G. Althaus , Marcelo M. Miller Bertolami , S. O. Kepler

Stars are extremely important astronomical objects that constitute the pillars on which the Universe is built, and as such, their study has gained increasing interest over the years. White dwarf stars are not the exception. Indeed, these stars constitute the final evolutionary stage for more than 95% of all stars. The Galactic population of white dwarfs conveys a wealth of information about several fundamental issues and are of vital importance to study the structure, evolution and chemical enrichment of our Galaxy and its components—including the star formation history of the Milky Way. Several important studies have emphasized the advantage of using white dwarfs as reliable clocks to date a variety of stellar populations in the solar neighborhood and in the nearest stellar clusters, including the thin and thick disks, the Galactic spheroid and the system of globular and open clusters. In addition, white dwarfs are tracers of the evolution of planetary systems along several phases of stellar evolution. Not less relevant than these applications, the study of matter at high densities has benefited from our detailed knowledge about evolutionary and observational properties of white dwarfs. In this sense, white dwarfs are used as laboratories for astro-particle physics, being their interest focused on physics beyond the standard model, that is, neutrino physics, axion physics and also radiation from “extra dimensions”, and even crystallization. The last decade has witnessed a great progress in the study of white dwarfs. In particular, a wealth of information of these stars from different surveys has allowed us to make meaningful comparison of evolutionary models with observations. While some information like surface chemical composition, temperature and gravity of isolated white dwarfs can be inferred from spectroscopy, and the total mass and radius can be derived as well when they are in binaries, the internal structure of these compact stars can be unveiled only by means of asteroseismology, an approach based on the comparison between the observed pulsation periods of variable stars and the periods predicted by appropriate theoretical models. The asteroseismological techniques allow us to infer details of the internal chemical stratification, the total mass, and even the stellar rotation profile. In this review, we first revise the evolutionary channels currently accepted that lead to the formation of white-dwarf stars, and then, we give a detailed account of the different sub-types of pulsating white dwarfs known so far, emphasizing the recent observational and theoretical advancements in the study of these fascinating variable stars.



中文翻译:


脉动白矮星:新见解



恒星是极其重要的天体,它们构成了宇宙的支柱,因此,它们的研究多年来引起了越来越多的兴趣。白矮星也不例外。事实上,这些恒星构成了95%以上的所有恒星的最终进化阶段。银河系的白矮星群传达了有关几个基本问​​题的丰富信息,对于研究银河系及其组成部分的结构、演化和化学富集(包括银河系的恒星形成历史)至关重要。几项重要的研究强调了使用白矮星作为可靠时钟来测定太阳附近和最近的星团中各种恒星种群的优势,包括薄盘和厚盘、银河椭球体以及球状和疏散星团系统。此外,白矮星是沿着恒星演化的几个阶段的行星系统演化的示踪物。与这些应用一样重要的是,对高密度物质的研究受益于我们对白矮星演化和观测特性的详细了解。从这个意义上说,白矮星被用作天体粒子物理的实验室,因为它们的兴趣集中在标准模型之外的物理,即中微子物理、轴子物理以及来自“额外维度”的辐射,甚至结晶。过去十年见证了白矮星研究的巨大进展。特别是,来自不同调查的这些恒星的大量信息使我们能够对进化模型与观测结果进行有意义的比较。 虽然孤立白矮星的表面化学成分、温度和重力等一些信息可以通过光谱学推断出来,并且当它们处于双星状态时也可以推导出它们的总质量和半径,但这些致密恒星的内部结构只能通过以下方法来揭示:星震学手段,一种基于观测到的变星脉动周期与适当的理论模型预测的周期之间的比较的方法。星震学技术使我们能够推断出内部化学分层、总质量、甚至恒星旋转轮廓的细节。在这篇综述中,我们首先修改了目前公认的导致白矮星形成的演化通道,然后,我们详细描述了迄今为止已知的脉动白矮星的不同亚型,强调了最近的观测和研究这些迷人的变星研究的理论进展。

更新日期:2019-09-03
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