间歇吸积毫秒X射线脉冲星Aql X-1在脉冲开启和关闭阶段的光谱详细研究
A Detailed Spectral Study of Intermittent-Accreting Millisecond X-ray Pulsar Aql X-1 during Pulse-on and Pulse-off Stages
AI总结：
该研究利用RXTE数据对间歇吸积毫秒X射线脉冲星Aql X-1在脉冲开启和关闭阶段进行光谱分析，发现额外黑体成分表明中子星表面存在热点，半径为1.65±0.74 km，温度为1.65 keV。
摘要：
我们利用RXTE档案数据，对间歇性吸积毫秒X射线脉冲星（intermittent-AMXP）Aql X-1在脉冲开启（pulse-on）和脉冲关闭（pulse-off）阶段进行了详细的光谱研究。首先，我们使用Z$_n^2$技术对RXTE数据最后128秒时间片段（包含脉冲开启区域）在三个不同能段（3.0–13.0 keV、13.0–23.0 keV和23.0–33.0 keV）进行了时间分析。我们表明，脉冲在最软能段最为显著。然后，我们证明光谱由吸收黑体（absorbed blackbody）、盘黑体（disk blackbody）和高斯线（gaussian line）的组合表示最佳。我们对数据30188-03-05-00的最后四个片段进行了建模，以更好地比较脉冲开启和关闭阶段。我们在脉冲开启片段的$\tilde$3.0–13.0 keV能段发现了一个模糊的残差，这与时间分析的结果一致。我们表明，该残差可以用一个额外的黑体成分来表示，其温度为1.75 keV，半径为0.75$\tilde$0.49 km。为了更深入的分析，我们对最后128秒的脉冲开启片段进行了相位分辨光谱分析。我们获得了自旋相位范围0.75–0.25（脉冲高）和0.25–0.75（脉冲低）的两个独立光谱，并遵循了相同的程序。我们显示，与脉冲低相比，脉冲高的残差变得更加清晰。我们报告，模拟残差的额外黑体成分表明中子星表面存在一个热点，其半径为1.65$\tilde$0.74 km，温度为1.65 keV。
英文摘要：
We present a detailed spectral study of an intermittent-AMXP Aql X-1 during the pulse-on and pulse-off stages by using the archival RXTE data. We first perform temporal analysis by using Z$_n^2$ technique in three different energy bands, 3.0 -- 13.0 keV, 13.0 -- 23.0 keV and 23.0 -- 33.0 keV, for the last 128 s time segment of the RXTE data including pulse-on region. We show that the pulse is the most significant in the softest band. We, then, show that the spectrum is represented the best via combination of absorbed blackbody, disk blackbody and a gaussian line. We modeled the last four segments of the data 30188-03-05-00 to better compare pulse-on and pulse-off stages. We found a vague residual in the spectral fit of the pulse-on segment between $\sim$3.0 -- 13.0 keV which agrees with the result of temporal analysis. We show that the residual may be represented with an extra blackbody component with the temperature of 1.75 keV and the radius of 0.75$\pm$0.49 km. For deeper analysis, we performed phase-resolved spectroscopy to the last 128 s, pulse-on, segment. We obtain two separate spectra for the spin phase range of 0.75 -- 0.25, pulse-high and 0.25 -- 0.75, pulse-low and followed the same procedure. We display that the residual becomes more clear for pulse-high compared to the pulse-low. We report that the additional blackbody component, which models the residual, indicates a hotspot from the surface of the neutron star with the radius of 1.65$\pm$0.74 km whose temperature is 1.65 keV.
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