THE THERMAL STATE OF KS 1731−260 AFTER 14.5 YEARS IN QUIESCENCE
THE THERMAL STATE OF KS 1731−260 AFTER 14.5 YEARS IN QUIESCENCE
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静止 14.5 年后 KS 1731−260 的热状态
DOI：
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发表时间：
2016
期刊：
影响因子：
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通讯作者：
R. Wijnands
中科院分区：
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作者：
R. L. Merritt;E. Cackett;E. Brown;D. Page;A. Cumming;N. Degenaar;Alex Deibel;J. Homan;Jonathan M. Miller;R. Wijnands
吸积加热中子星的地壳冷却提供了对中子星内部的深入了解。中子星星X射线瞬变，KS 1731−260，在2001年恢复平静之前爆发了12.5年。从那时起，我们通过钱德拉和XMM-牛顿观测监测了这个源的冷却。在这里，我们展示了2015年8月拍摄的KS 1731−260的150 ks钱德拉观测，大约14.5年进入平静期，距离上次观测6年。我们发现中子星星表面温度与先前的观测结果一致，这表明地壳冷却可能已经停止，地壳已经与内核达到热平衡。利用理论地壳热演化程序，拟合了观测到的冷却曲线，并限定了核心温度（Tc = 9.35 ± 0.25 × 107 K）、成分（Q）和所需的超浅层加热水平（Qsh = 1.36 ± 0.18MeV/核子）。我们发现，低导热系数层的存在下，预期从核面食，不需要拟合的冷却曲线，但也不能排除。
Crustal cooling of accretion-heated neutron stars provides insight into the stellar interior of neutron stars. The neutron star X-ray transient, KS 1731−260, was in outburst for 12.5 years before returning to quiescence in 2001. We have monitored the cooling of this source since then through Chandra and XMM-Newton observations. Here we present a 150 ks Chandra observation of KS 1731−260 taken in 2015 August, about 14.5 years into quiescence and 6 years after the previous observation. We find that the neutron star surface temperature is consistent with the previous observation, suggesting that crustal cooling has likely stopped and the crust has reached thermal equilibrium with the core. Using a theoretical crust thermal evolution code, we fit the observed cooling curves and constrain the core temperature (Tc = 9.35 ± 0.25 × 107 K), composition (Q ), and level of extra shallow heating required (Qsh = 1.36 ± 0.18 MeV/nucleon). We find that the presence of a low thermal conductivity layer, as expected from nuclear pasta, is not required to fit the cooling curve well, but cannot be excluded either.