SGRs and AXPs as massive fast rotating highly magnetized white dwarfs: the case of SGR 0418+5729
Kuantay Boshkayev, Jorge A. Rueda, Remo Ruffini
备注:
6 pages, 1 figure, 1 table. The Thirteenth Marcel Grossmann Meeting: On Recent Developments in Theoretical and Experimental General Relativity, Astrophysics and Relativistic Field Theories - Proceedings of the MG13 Meeting on General Relativity (in 3 Volumes). Edited by Rosquist Kjell et. al
发表信息:
World Scientific Publishing Co. Pte. Ltd., 2015. ISBN #9789814623995, pp. 2295-2300
We describe one of the so-called low magnetic field magnetars SGR 0418+5729, as a massive fast rotating highly magnetized white dwarf following Malheiro et. al. 2012. We give bounds for the mass, radius, moment of inertia, and magnetic field for these sources, by requesting the stability of realistic general relativistic uniformly rotating configurations. Based on these parameters, we improve the theoretical prediction of the lower limit of the spin-down rate of SGR 0418+5729. In addition, we compute the electron cyclotron frequencies corresponding to the predicted surface magnetic fields.
A Magnetar Strength Surface Magnetic Field for the Slowly Spinning Down SGR 0418+5729
观测到的典型软伽马射线中继站SGR 0418+5729的自旋下降速率上限对将该源解释为具有超强磁场的中子星提出了挑战。电流限值意味着偶极磁场强度小于7.5 x 10^{12} G(Rea等人,2010年),明显小于典型SGR。中子星的X射线光谱不依赖于从X射线计时推断出的性质,而允许测量它们的磁场强度,因为它们在辐射平衡大气中由于存在磁场而从纯黑体中失真。在本文中,我们模拟SGR 0418+5729的高信噪比XMM牛顿谱,以限制中子星表面的磁场强度。我们的分析表明,具有中等磁场强度(10^{12-13} G)的中子星大气模型不能拟合X射线谱,而具有较强磁场的模型能够解释观测结果。我们发现表面的磁场强度为1.0 x 10^{14} G。这个值虽然低于迄今为止分析的所有其他SGR,但仍然足够高,可以从源产生观测到的X射线爆发。关于自旋下降极限,它还意味着磁场的显著非偶极结构。我们讨论了我们的光谱建模的结果,并与其他SGRs进行比较。