Carbon neutron star atmospheres

中子星（NS）核中超致密物质的物理性质是现代物理学最有趣的问题之一。也被称为NS状态方程问题，它不能单独使用理论考虑或重离子碰撞实验来解决。解决这个问题的一个直接方法是同时从X射线光谱测定NS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准确，无法得出确切的结论。两个主要的障碍是未知的距离NS和未知的NS大气的化学成分，然而，准确的出射光谱的NS模型大气（具有适当的组成）是至关重要的基本中子星星参数的测量。我们建议使用一个特殊的子类的NS，允许克服这一障碍。NS在超新星遗迹（所谓的中央紧凑型对象，CCO）是特别有趣的，因为其中一些距离（和年龄）是足够众所周知的。此外，没有证据表明这些天体上有持续的吸积，因此它们的气体上层未受干扰，可以用恒星大气模型方法描述。最近，从X射线光谱学中发现的证据表明，一些CCO的大气层由碳组成。知道CCO的距离和包络成分使我们能够得到更精确的NS参数，提供的模型大气和紧急光谱可以计算具有足够高的精度。该项目提案的直接目标是调查可能会显着影响现有理论碳NS大气光谱的潜在最重要的物理过程。作为最后的结果，我们计划计算新的网格精确的模型光谱，并使用它们来分析档案X射线光谱的NS与可能的碳气氛。这些网格将予以公布，以便今后可以用它们来分析观测结果。新的，严格的约束NS核心的状态方程，也对中微子冷却物理将获得。

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.