标题： X射线暗弱孤立中子星RX J0720.4-3125中快速磁场衰减的迹象 显示英文标题

标题： Indication of rapid magnetic field decay in X-ray Dim Isolated Neutron Star RX J0720.4-3125

摘要： 中子星的磁场演化是一个长期存在的争论。 孤立且不吸积的中子星的磁场衰减率可以通过测量自转周期的负二阶导数来量化。 或者，可以通过观察相对于标准冷却的热辐射过量来估计这一速率，而无需涉及额外的加热机制。 其中一颗附近的冷却孤立中子星——RX J0720.4-3125——提供了一个独特的机会来探测磁场衰减，因为对于这个天体，有独立的表面X射线光度、二阶自转周期导数和磁场的测量。 我们证明，自转周期导数的演化速率与偶极磁场的磁能耗散速率是一致的，如果释放的能量的很大一部分以X射线形式发射的话。 磁场衰减的瞬时时间尺度是$\sim 10^4$年。 显示英文摘要

摘要： Magnetic field evolution of neutron stars is a long-standing debate. The rate of magnetic field decay for isolated, non-accreting neutron stars can be quantified by measuring the negative second derivative of the spin period. Alternatively, this rate can be estimated by observing an excess of thermal emission with respect to the standard cooling without additional heating mechanisms involved. One of the nearby cooling isolated neutron stars -- RX J0720.4-3125, -- offers a unique opportunity to probe the field decay as for this source there are independent measurements of the surface X-ray luminosity, the second spin period derivative, and magnetic field. We demonstrate that the evolution rate of the spin period derivative is in correspondence with the rate of dissipation of magnetic energy of the dipolar field if a significant part of the released energy is emitted in X-rays. The instantaneous time scale for the magnetic field decay is $\sim 10^4$ years.