标题： 2015年出现明亮爆发后，X射线脉冲星V0332+53的磁场意外下降 显示英文标题

标题： An unexpected drop in the magnetic field of the X-ray pulsar V0332+53 after the bright outburst occurred in 2015

摘要： 吸积物质落在中子星表面如何影响磁场的拓扑结构，以及双星系统的长期演化如何依赖于磁场的变化，仍然是一个未解的问题。 我们报告了吸积脉冲星V0332+53在经历了一次明亮的持续3个月的X射线爆发后，观测到的磁场出现了明显的下降。 我们通过X射线能谱中基本回旋谐振吸收线的位置确定磁场，并将其与光度联系起来。 对于相同水平的光度，在衰减阶段我们测量到的回旋谐振吸收线能量系统性地低于上升阶段。 这导致爆发开始和结束时观测到的磁场强度下降了约1.7×10^11高斯。 落向极冠的吸积等离子体似乎会诱导磁力线发生扭曲，从而削弱沿吸积柱的磁力线强度。 因此，磁场的耗散率可能比之前估计的要快得多，除非磁场能够在与爆发重复周期相当的时间尺度上恢复其原始构型。 显示英文摘要

摘要： How the accreted mass settling on the surface of a neutron star affects the topology of the magnetic field and how the secular evolution of the binary system depends on the magnetic field change is still an open issue. We report evidence for a clear drop in the observed magnetic field in the accreting pulsar V0332+53 after undergoing a bright 3-month long X-ray outburst. We determine the field from the position of the fundamental cyclotron line in its X-ray spectrum and relate it to the luminosity. For equal levels of luminosity, in the declining phase we measure a systematically lower value of the cyclotron line energy with respect to the rising phase. This results in a drop of ~1.7 x 10^11 G of the observed field between the onset and the end of the outburst. The settling of the accreted plasma onto the polar cap seems to induce a distortion of the magnetic field lines weakening their intensity along the accretion columns. Therefore the dissipation rate of the magnetic field could be much faster than previously estimated, unless the field is able to restore its original configuration on a time-scale comparable with the outbursts recurrence time.