Collaborative Research: Theoretical Studies of the Atmospheres of Highly Magnetized Neutron Stars

磁星是一种中子星星，或密度极高的星星，它拥有非常大的磁场。 磁星，其中大约30个已经被发现，是宇宙中最有趣的紧凑物体。 威廉·马什·赖斯大学、霍普学院和美国航天局戈达德空间飞行中心合作开展的一项研究方案将导致发展磁星大气排放的最先进理论模型。其主要目标是提供一套可观测的信号预测，以增强对X射线望远镜数据的解释，从而更好地了解中子星，磁性和基本量子物理学。将对X射线通过具有任意磁场方向的磁星大气层的传播进行计算机模拟，包括中子星星表面从磁极到赤道的所有位置。 这项研究包括重要的研究生和本科生培训。莱斯大学的一名博士生将参与这项工作，其结果将导致博士论文。几名本科生将从事研究的独立部分，并将他们的发现展示给资深科学家和同行。 研究人员将向公众阐明这项工作的各个方面，以及中子星这一令人兴奋的领域的亮点。磁星为测试目前在陆地实验室无法访问的基础物理提供了一个独特的论坛。 更好地理解磁星是将它们用作代理量子电动力学（QED）物理实验室的核心。研究人员将通过对磁星大气层的发射进行全面的理论研究，计算表面任何位置的偏振相关和角度相关发射率的预期来帮助实现这一目标。偏振特征的产生将允许区分几何源信息和强场QED物理的特征，如双折射真空偏振。这项工作将升级光球回旋吸收线物理和光子传播，为天体物理学家提供新的工具，用于其他中子星星问题。该计划的结果将提高X射线波段偏振望远镜的潜在科学产量。 与磁星有关的四个悬而未决的问题将受到研究的重大影响。这些是（i）磁星本质上不同于正常的磁星？，(ii)自转体的磁倾角是否随磁星年龄的变化而变化，我们是否可以测量它，以便更精确地校准恒星的场强？(iii)其中，相对于磁极，是磁星表面产生准热辐射的加热点？以及（iv）我们是否可以利用广义相对论来确定磁星的质量半径比，从而探索它们的状态方程？该奖项反映了NSF的法定使命，并被认为是值得通过使用基金会的知识价值和更广泛的影响审查标准进行评估的支持。

A magnetar is a neutron star, or extremely dense star, which possesses an extraordinarily large magnetic field. Magnetars, of which around 30 have been discovered, are some of the most intriguing compact objects in the Universe. A research program, which is a collaboration between William Marsh Rice University, Hope College and NASA's Goddard Space Flight Center, will lead to the development of state of the art theoretical models for the atmospheric emission of magnetars. The prime objective is to deliver a suite of observable signal predictions to enhance interpretation of data from X-ray telescopes, leading to a better understanding of neutron stars, magnetism and fundamental quantum physics. Computer simulations will be developed for the propagation of X-rays through magnetar atmospheres with arbitrary magnetic field orientations, including all locations on the neutron star surface, from magnetic pole to equator. The research includes significant graduate and undergraduate training. A PhD student at Rice University will be integral to the work, with the results leading to a doctoral thesis. Several undergraduates will work on self-contained portions of the research and present their discoveries to senior scientists and peers. The investigators will elucidate aspects of this work, and highlights of the exciting field of neutron stars, to the general public.Magnetars present a unique forum for testing fundamental physics that is not presently accessible in terrestrial laboratories. Better understanding of magnetars is central to using them as a proxy quantum electrodynamics (QED) physics laboratory. The researchers will help enable this by developing a comprehensive theoretical study of the emission from magnetar atmospheres, computing expectations for the polarization- dependent and angle-dependent emissivities at any position on the surface. The generation of polarization signatures will allow discrimination between the geometrical source information and the signatures of strong-field QED physics, like birefringent vacuum polarization. The work will feature upgrades of photospheric cyclotron absorption line physics and photon propagation, providing new tools for astrophysicists to employ in other neutron star problems. The results of this program will enhance potential science yields from polarimetric telescopes in the X-ray band. Four outstanding questions pertaining to magnetars will be significantly impacted by the research. These are (i) are magnetars inherently different from normal pulsars?, (ii) does the magnetic inclination angle of the rotator evolve with magnetar age, and can we measure it so as to more precisely calibrate the stellar field strength?, (iii) where, relative to the magnetic pole, is the site of heating in the surface that seeds quasi- thermal radiation in magnetars?, and (iv) can we use general relativity to determine the mass-to-radius ratio for magnetars, and thereby probe their equations of state?This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.