标题： 理解RX J1856.5-3754的紫外-光学超量 显示英文标题

标题： To Understand the UV-optical Excess of RX J1856.5-3754

摘要： RX J1856.5-3754 是所谓的暗弱热中子星之一，它有两个谜团：（1）观测到的X射线能谱完全无特征；（2）紫外-光学强度比由X射线数据得出的黑体模型外推值大约高七倍。如果RX J1856.5-3754是一个低质量裸奇异夸克星，并且处于低吸积率的螺旋桨阶段，那么这两个谜团将不再存在。文中建议并模拟了RX J1856.5-3754的一个边界层，从该边界层辐射出紫外-光学发射。自由-自由吸收主导了边界层的opacity，这导致在紫外-光学波段opacity较高而在X射线波段较低。通过观测限制了这颗星的磁场强度、自转周期以及吸积率。 显示英文摘要

摘要： The enigma source, RX J1856.5-3754, is one of the so-called dim thermal neutron stars. Two puzzles of RXJ1856.5-3754 exist: (1) the observational X-ray spectrum is completely featureless; (2) the UV-optical intensity is about seven times larger than that given by the continuation of the blackbody model yielded by the X-ray data. Both the puzzles would not exist anymore if RX J1856.5-3754 is a low mass bare strange quark star, which is in a propeller phase with a low accretion rate. A boundary layer of RX J1856.5-3754 is suggested and modelled, from which the UV-optical emission is radiated. Free-free absorption dominates the opacity of the boundary layer, which results in the opacity to be high in UV-optical but low in X-ray bands. The star's magnetic field, spin period, as well as the accretion rate are constrained by observations.