Differentiating Neutron Star Models by X-Ray Polarimetry
LU Ji-Guang1, XU Ren-Xin1**, FENG Hua2
1School of Physics and State Key Laboratory of Nuclear Physics and Technology, Peking University, Beijing 100871 2Department of Engineering Physics and Center for Astrophysics, Tsinghua University, Beijing 100084
Abstract：The nature of pulsars is still unknown because of the non-perturbative effects of the fundamental strong interaction, so various models of pulsar inner structures are suggested, either for conventional neutron stars or quark stars. Additionally, a quark-cluster matter state is conjectured for cold matter at supranuclear density, and as a result pulsars can be quark-cluster stars. Besides understanding the different manifestations, the most important issue is to find an effective way to observationally differentiate these models. X-ray polarimetry plays an important role here. The thermal x-ray polarization of quark/quark-cluster stars is focused on, and while the thermal x-ray linear polarization percentage is typically higher than ～10% in normal neutron star models, the percentage of quark/quark-cluster stars is almost zero. This could then be an effective method to identify quark/quark-cluster stars by soft x-ray polarimetry. We are therefore expecting to detect thermal x-ray polarization in the coming decades.
2013, Vol. 30 
