Carbon neutron star atmospheres

中子星核心中超致密物质的物理性质是现代物理学中最有趣的问题之一。也被称为NS状态方程问题，它不能用理论考虑或实验室实验来解决单独的重离子碰撞。解决这个问题的一个直接的方法是用x射线光谱学同时测定NSs的质量和半径。尽管在过去十年中取得了很大的进展，但这种测量仍然不够精确，无法得出确切的结论。两个主要的障碍是通常未知的NSs距离和NSs大气的化学成分，然而，精确的NSs模型大气的出现光谱（具有适当的成分）对于中子星基本参数的测量至关重要。我们建议使用一个特定的NSs子类来克服这些障碍。超新星残骸中的NSs（所谓的中央致密天体，CCOs）特别有趣，因为其中一些的距离（和年龄）是众所周知的。此外，没有证据表明这些天体上有持续的吸积，因此它们的上层气体层没有受到干扰，可以用模型恒星大气方法来描述。最近，从x射线光谱学中发现的证据表明，一些cco有由碳组成的大气。如果能够以足够高的精度计算模式大气和紧急光谱，那么知道CCOs的距离和包络组成可以得到更精确的NS参数。本项目提案的直接目的是研究可能显著影响现有理论碳NS大气光谱的潜在最重要的物理过程。作为最终结果，我们计划计算新的精确模型光谱网格，并将其用于分析可能存在碳大气的NSs的档案x射线光谱。这些网格将被公布，以便将来的观测可以用它们进行分析。将获得对核态方程和中微子冷却物理的新的、严格的约束。

The physical properties of super-dense matter in neutron-star (NS) cores is one of the most intriguing problems of modern physics. Also known as the NS equation-of-state problem, it cannot be resolved using theoretical considerations or laboratory experiments with heavy-ion collisions alone. A straightforward way for attacking this problem is the simultaneous mass and radius determination of NSs from X-ray spectroscopy. Despite of great progress in the last decade, this kind of measurements is still not sufficiently accurate to draw firm conclusions. Two of the main obstacles are generally unknown distances to NSs and unknown chemical compositions of NS atmospheres, however, accurate emergent spectra of NS model atmospheres (with appropriate composition) are crucially necessary for the measurement of basic neutron star parameters. We propose to use a particular subclass of NSs that allow to overcome this obstacles.NSs in supernova remnants (so-called Central Compact Objects, CCOs) are particularly interesting because for some of them distances (and ages) are sufficiently well known. In addition, there is no evidence for on-going accretion onto these objects so their gaseous upper layers are undisturbed and can be described by model stellar atmosphere methods. Recently, evidence was found from X-ray spectroscopy that some of the CCOs have atmospheres composed of carbon. Knowing distance and envelope composition of CCOs enables us to derive more precise NS parameters, provided the model atmospheres and emergent spectra can be computed with sufficiently high accuracy. The immediate aim of this project proposal is to investigate the potentially most important physical processes that can significantly affect existing theoretical carbon NS atmosphere spectra. As a final result we plan to compute new grids of accurate model spectra and use them for analyses of archival X-ray spectra of NSs with possible carbon atmospheres. These grids will be published so that future observations can be analysed with them. New, tight constraints on the equation-of-state in NS cores and also on neutrino-cooling physics will be obtained.