Continued cooling of the accretion-heated neutron star crust in the X-ray transient IGR J17480–2446 located in the globular cluster Terzan 5
Continued cooling of the accretion-heated neutron star crust in the X-ray transient IGR J17480–2446 located in the globular cluster Terzan 5
复制标题
DOI：
10.1093/mnras/stz1406
复制
发表时间：
2018-05
影响因子：
4.8
通讯作者：
L. Ootes;S. Vats;D. Page;R. Wijnands;A. Parikh;N. Degenaar;M. Wijngaarden;D. Altamirano;A. Bahramian;E. Cackett;C. Heinke;J. Homan;J. Miller
中科院分区：
文献类型：
--
作者：
L. Ootes;S. Vats;D. Page;R. Wijnands;A. Parikh;N. Degenaar;M. Wijngaarden;D. Altamirano;A. Bahramian;E. Cackett;C. Heinke;J. Homan;J. Miller
我们提出了一个新的钱德拉观测（在2016年7月进行）的中子星星X射线瞬态IGR J17480-2446，位于球状星团泰山5。我们研究了这个系统中中子星星地壳的持续冷却，该系统在2010年爆发时被加热。在IGR J17480-2446的最后一次观察后2年进行了这项新的观察，因此，显著延长了冷却基线。我们重新分析了源的所有可用的钱德拉观测（但不包括Terzan 5中已知瞬变之一处于爆发状态的观测），并用我们的冷却代码NSCOOL拟合了获得的冷却曲线，这使得建模比以前对源进行的建模有了很大的改进。数据和我们的拟合模型表明，地壳仍在冷却爆发结束后约5.5年。中子星星的地壳可能还没有达到壳核热平衡，预计会进一步冷却（这可以通过钱德拉在>5年内的额外观测来证实）。有趣的是，我们发现的迹象表明，热导率可能是相对较低的部分地壳相比，已推断为其他地壳冷却源，并初步建议，这一层可能位于周围的中子滴。这种差异的原因尚不清楚，但可能与IGR J17480-2446拥有一个相对缓慢旋转的中子星星（自旋为11 Hz），与已知或通常假设的其他冷却源相比，它具有相对较强的表面磁场（109−10高斯）。
We present a new Chandra observation (performed in 2016 July) of the neutron star X-ray transient IGR J17480–2446, located in the globular cluster Terzan 5. We study the continued cooling of the neutron star crust in this system that was heated during the 2010 outburst of the source. This new observation was performed 2 yr after the last observation of IGR J17480–2446, hence, significantly extending the cooling baseline. We reanalysed all available Chandra observations of the source (but excluding observations during which one of the known transients in Terzan 5 was in outburst) and fitted the obtained cooling curve with our cooling code NSCOOL, which allows for much improved modelling than what was previously performed for the source. The data and our fit models indicate that the crust was still cooling ∼5.5 yr after the outburst ended. The neutron star crust has likely not reached crust-core thermal equilibrium yet, and further cooling is predicted (which can be confirmed with additional Chandra observations in >5 yr). Intriguingly, we find indications that the thermal conductivity might be relatively low in part of the crust compared to what has been inferred for other crust-cooling sources and tentatively suggest that this layer might be located around the neutron drip. The reason for this difference is unclear, but might be related to the fact that IGR J17480–2446 harbours a relatively slowly rotating neutron star (with a spin of 11 Hz) that has a relatively strong inferred surface magnetic field (109−10 Gauss) compared to what is known or typically assumed for other cooling sources.