Version with small modifications in the abstract and in caption of Figure 1, 3 pages including 1 figure; to appear in the Proceedings of 13th Marcel Grossmann Meeting (MG13), Stockholm, Sweden, 1-7 July 2012; based on the talk given at the Parallel Session SO4 "White Dwarf Pulsars and Rotating White Dwarf Theory"
SGRs/AXPs are assumed to be a class of neutron stars (NS) powered by magnetic energy and not by rotation, as normal radio pulsars. However, the recent discovery of radio-pulsed emission in four of this class of sources, where the spin-down rotational energy lost $\dot{E}_{\rm rot}$ is larger than the X-ray luminosity $L_X$ during the quiescent state - as in normal pulsars - opens the question of the nature of these radio AXPs in comparison to the others of this class. In this work, we show that the radio AXPs obey a linear log-log relation between $L_X$ and $\dot{E}_{\rm rot}$, very similar to the one of normal X-ray pulsars, a correlation not seen for the others SGRs/AXPs. This result suggests a different nature between the radio AXPs comparing to the others SGRs/AXPs.
The Broad-band Noise Characteristics of Selected Anomalous X-Ray Pulsars and Soft Gamma-ray Repeaters
本文给出了2-60 keV能区反常X射线脉冲星（AXP）和软γ重复源（SGR）的宽带噪声结构。我们已经分析了罗西X射线定时探测器正比计数器阵列档案光曲线的四个AXP和一个SGR。我们检测到，这些源的持续发射显示在0.005-0.05 Hz的范围内的低频带限噪声变化从2.5%到70%的综合均方根时间的长时间的静止和以下爆发。我们在1 E 2259+586中发现了仅在2002年大爆发后$\sim$ 2年的限带红噪声。除此之外，系统没有显示出宽带噪声。虽然1 E 2259+586中的噪声上升发生在包括旋转毛刺的爆发之后，但其他毛刺AXP显示宽带噪声没有明显变化，因此该噪声似乎与毛刺无关。唯一显示出宽带噪声显著变化的源是1 E 1048.1-5937，其中噪声以每年$\sim$ 3.6%的速率逐渐上升1.95年。对于这个源的宽带噪声的增加是不相关的持续性和脉冲流量的大幅增加，或其两个短SGR样的爆发。这种噪声的上升确实是在一个长脉冲群之后开始的，但是考虑到该事件的稀疏性，以及类似脉冲群未被注意到的可能性，1 E 1048.1-5937中的噪声上升触发因素不像1 E 2259+586那样明确。其他三个源表明，相比之下，持续的低电平带限噪声。
