Carbon neutron star atmospheres

中子星(NS)核中超稠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，不能仅用理论考虑或实验室实验来解决重离子碰撞。解决这个问题的一个直接方法是从X射线光谱学中同时确定NSS的质量和半径。尽管在过去的十年里取得了很大的进步，但这种测量仍然不够准确，不足以得出确定的结论。两个主要障碍通常是到NSS的未知距离和NS大气的化学成分未知，然而准确的NS模型大气的出射光谱(具有适当的成分)对于测量基本的中子星参数是至关重要的。我们建议使用一个特定的NSS子类来克服这个障碍。超新星遗迹(所谓的中央致密天体，CCO)中的NSS特别有趣，因为对它们中的一些来说，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正在进行吸积，因此它们的气体上层不受干扰，可以用模型恒星大气方法来描述。最近，从X射线光谱中发现的证据表明，一些CCO的大气层由碳组成。如果我们能以足够高的精度计算模式大气和出射光谱，已知CCOS的距离和包络组成使我们能够得到更精确的NS参数。该项目提案的直接目的是调查可能对现有理论碳氮大气光谱有重大影响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，并将它们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，以便未来的观测可以用它们来分析。对NS核中的状态方程和中微子冷却物理都将得到新的、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.