Comprehensive modelling of pulse shape formation in binary X-ray pulsars

X射线双星脉冲星的高能辐射来自于强磁化旋转中子星上的电离气体的吸积。如果磁轴和旋转轴不对齐，就会观察到脉冲发射。吸积的X射线脉冲星显示出各种不同的脉冲形状，这是每个源的特点。近年来，由于几颗卫星的出色观测，获得了越来越丰富的关于光谱和脉冲形状的高质量观测数据。然而，经过近40年的研究，仍然没有令人信服的模型可以用来从脉冲形状推断X射线脉冲星的几何和物理参数。在这个项目中，我们的目的是更好地理解脉冲波形的形成机制。我们将开发和研究一套全面的唯象模型，并将它们与宽带观测数据进行比较。这些模型将充分考虑相对论光偏转，并将包括一些重要的影响，这些效应到目前为止已被包括在少数几个模型中(然后单独)，或仅以定性的方式讨论：晕形成、吸积流食、晕辐射的再处理以及不同的吸积流几何形状。最终，我们不仅希望对与吸积脉冲星发射相关的机制有深入的了解，而且还将对这类系统的关键物理参数设置限制，如中子星的质量、半径、磁矩和磁场组态、吸积率、磁轴和旋转轴之间的偏移量、吸积丘几何形状。

High energy radiation from X-ray binary pulsars originates from the accretion of ionized gas onto strongly magnetized rotating neutron stars. If the magnetic and rotation axes are disaligned, pulsed emission is observed. Accreting X-ray pulsars display a large variety of pulse shapes, that are characteristic for each source. In recent years an increasing wealth of high quality observational data on spectra and pulse shapes has been obtained thanks to the outstanding observations of several satellites. However, after almost four decades of research, there is still no compelling model that one could apply to infer the geometric and physical parameters of X-ray pulsars from their pulse shapes. In this project we aim at a better understanding of the mechanisms of pulse shape formation. We will develop and study a set of comprehensive phenomenological models and compare them to broadband observational data. These models will take full account of relativistic light deflection and will include a number of important effects that have so far been included in few models (and then separately) or have been discussed only in a qualitative way: halo formation, accretion stream eclipses, reprocessing of halo radiation, and different accretion stream geometries. Eventually we expect not only to reach a deep understanding of the mechanisms relevant to accreting pulsar emission but also to set constraints on key physical parameters of such systems like mass, radius, magnetic moment and magnetic field configuration of the neutron star, accretion rate, offset between magnetic and rotation axes, accretion mound geometry.