标题： 利用钱德拉和XMM-牛顿卫星观测到的孤立中子星RX J1856.5-3754的热辐射 显示英文标题

标题： The thermal radiation of the isolated neutron star RX J1856.5-3754 observed with Chandra and XMM-Newton

摘要： 我们展示了分析来自57 ks XMM-Newton和505 ks Chandra对附近约120 pc的孤立中子星RX J1856.5-3754的观测数据的结果。我们确认了Burwitz等人（2001）提出的大部分关于原始55 ks Chandra数据的论述。详细的联合X射线和光学光谱分析排除了目前可用的无磁场轻元素和重元素中子星大气模型（LTE），包括氢、氦、铁以及太阳成分的大气模型。我们发现强磁场大气模型也无法很好地拟合数据。 X射线和光学数据没有显示出光谱特征，并且最适配于一个双组分黑体模型，其中热X射线发射区域的参数为：kT_{bb，X}^{\infty } ~= 63.5 eV 和 R_{bb，X}^{\infty } ~= 4.4(d/120 pc) 千米；而剩余中子星表面负责光学通量的部分参数为：kT_{bb,opt}^{\infty }< 33 eV 和 R_{bb,opt}^{\infty }> 17(d/120 pc) 千米。 利用XMM-Newton收集到的大数量计数，我们能够将X射线范围内周期性变化的上限降低至1.3%（在2\sigma 置信水平下）的10^{-3}-50 Hz 频率范围。 为了尝试解释这种微小的变化，我们讨论了一个单组分模型，其中kT_{bb}^{\infty }约为63 eV，R_{bb}^{\infty }约等于12.3(d/120 pc)千米。 该模型需要在X射线波段具有较低的辐射效率，如果中子星表面存在凝聚态物质，则可以预期这一点。 显示英文摘要

摘要： We present results of the analysis of data collected in 57-ks XMM-Newton and 505-ks Chandra observations of the nearby ~= 120 pc isolated neutron star RX J1856.5-3754. We confirm most of the statements made by Burwitz et al. (2001) who discussed the original 55-ks Chandra data. Detailed spectral analysis of the combined X-ray and optical data rules out the currently available nonmagnetic light and heavy element neutron star atmosphere (LTE) models with hydrogen, helium, iron and solar compositions. We find that strongly magnetized atmosphere models also are unable to represent the data. The X-ray and optical data show no spectral features and are best fitted with a two-component blackbody model with kT_{bb,X}^{\infty} ~= 63.5 eV and R_{bb,X}^{\infty} ~= 4.4(d/120 pc) km for the hot X-ray emitting region, and kT_{bb,opt}^{\infty}<33 eV and R_{bb,opt}^{\infty}>17(d/120 pc) km for the rest of the neutron star surface responsible for the optical flux. The large number of counts collected with XMM-Newton allows us to reduce the upper limit on periodic variation in the X-ray range down to 1.3% (at a 2\sigma confidence level) in the 10^{-3}-50 Hz frequency range. In an attempt to explain this small variability, we discuss an one-component model with kT_{bb}^{\infty} ~= 63 eV and R_{bb}^{\infty} ~= 12.3(d/120 pc) km. This model requires a low radiative efficiency in the X-ray domain, which may be expected if the neutron star has a condensed matter surface.