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arXiv 1804.09899astro-ph.HE
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IGR J14257-6117,具有非常强的X射线轨道调制的磁吸积白矮星

IGR J14257-6117, a magnetic accreting white dwarf with a very strong X-ray orbital modulation

F. Bernardini, D. de Martino, K. Mukai, M. Falanga

摘要:

IGR J14257-6117是硬X射线目录中的未分类源。光学跟踪显示它可能是一颗磁性的激变变星。我们提出了第一个高S/N X射线观测\XMM \在0.3- 10 keV,补充了10- 80 keV覆盖的\Swift /BAT,旨在揭示源的性质。我们首次探测到了509.5s的快周期变率和4.05h的长周期变率,分别归因于白矮星(WD)的自旋和双星轨道周期.这些明确地将IGR J14257-6117识别为中间极性(IP)类型的磁性CV。在两个周期的能量分辨光变曲线显示振幅随能量增加而减小,轨道调制在最软的带中达到$\sim100\%$。能谱显示在铁络合物处过量的光学薄热发射,被两种致密介质(${\rm N_{H}\sim10^{22-23}\,cm^{-2}}$)吸收,部分覆盖X射线源。这些可能是本地化的磁约束吸积流以上的WD表面和盘边缘,产生的能量依赖的自旋和轨道的变化,分别。IGR J14257-6117,加入了最强轨道调制IP组,现在有四个系统。与显示轨道倾角的低质量X射线双星相似,这些IP应该在大的轨道倾角处被看到,允许固定在双星框架中的方位角扩展吸收材料拦截视线。对于IGR J14257-6117,我们估计($50^o\,\lesssim\,i\,\lesssim\,70^o$)。质量吸积率是否也在IPs的大轨道调制中起作用,不能用现有的数据来确定。

英文摘要:

IGR J14257-6117 is an unclassified source in the hard X-ray catalogues. Optical follow-ups suggest it could be a Cataclysmic Variable of the magnetic type. We present the first high S/N X-ray observation performed by \XMM\ at 0.3--10 keV, complemented with 10--80 keV coverage by \Swift/BAT, aimed at revealing the source nature. We detected for the first time a fast periodic variability at 509.5\,s and a longer periodic variability at 4.05\,h, ascribed to the white dwarf (WD) spin and binary orbital periods, respectively. These unambiguously identify IGR J14257-6117 as a magnetic CV of the Intermediate Polar (IP) type. The energy resolved light curves at both periods reveal amplitudes decreasing with increasing energy, with the orbital modulation reaching $\sim100\%$ in the softest band. The energy spectrum shows optically thin thermal emission with an excess at the iron complex, absorbed by two dense media (${\rm N_{H}\sim10^{22-23}\,cm^{-2}}$), partially covering the X-ray source. These are likely localised in the magnetically confined accretion flow above the WD surface and at the disc rim, producing the energy dependent spin and orbital variabilities, respectively. IGR J14257-6117, joins the group of strongest orbitally modulated IPs now counting four systems. Drawing similarities with low-mass X-ray binaries displaying orbital dips, these IPs should be seen at large orbital inclinations allowing azimuthally extended absorbing material fixed in the binary frame to intercept the line of sight. For IGR J14257-6117, we estimate ($50^o\,\lesssim\,i\,\lesssim\,70^o$). Whether also the mass accretion rate plays a role in the large orbital modulations in IPs cannot be established with the present data.

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