A soft X-ray lag detected in Centaurus A
A soft X-ray lag detected in Centaurus A
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在半人马座 A 中检测到软 X 射线滞后
DOI：
10.1093/pasj/psw001
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发表时间：
2016
影响因子：
2.3
通讯作者：
N Kawai
中科院分区：
文献类型：
--
作者：
Y Tachibana;T Kawamuro;Y Ueda;M Shidatsu;M Arimoto;Ti Yoshii;Y Yatsu;Y Saito;S Pike;N Kawai
对全天X射线成像仪(MAXI)上的气体狭缝相机(GSC)在2-4keV、4-10keV和10-20keV三个能区(2-4keV、4-10keV和10-20keV)获得的半人马座A(Cen A)X射线光曲线进行了时滞分析。利用离散相关函数(DCF)和z变换离散相关函数(ZDCF)方法，我们发现了耀斑过程中相对于较高能量的软X射线滞后(软滞后)。在这一事件中，在2-4keV和4-10keV和4-10keV和10-20keV的∼ 5 d和∼ 10 d的软滞后处观察到了DCF和ZDCF中的一个峰值和质心，在2-4keV和10-20keV的软滞后处观察到了一个峰值和质心。我们发现用单区同步加速器自康普顿(SSC)模型很难解释单次能量注入观测到的X射线变化，在该模型中，这三个能带的软滞后反映了相对论电子冷却时间的不同，假设磁场和根据宽带谱能量分布估计的最小洛伦兹因子。或者，如果将这一现象解释为覆盖吸积盘的日冕中康普顿电子的冷却，则产生可变X射线的日冕的温度应为∼ 10keV，以便与2-20keV能量范围内的软滞后相协调。
We performed time-lag analysis on the X-ray light curves of Centaurus A (Cen A) obtained by the Gas Slit Camera (GSC) aboard the Monitor of All-sky X-ray Image (MAXI) in three energy bands (2–4 keV, 4–10 keV, and 10–20 keV). We discovered a soft X-ray lag relative to higher energies (soft lag) on a timescale of days in a flaring episode by employing the discrete correlation function (DCF) and thez-transformed discrete correlation function (ZDCF) method. In the episode, a peak and a centroid in the DCF and the ZDCF was observed at a soft lag of ∼ 5 d in 2–4 keV versus 4–10 keV and in 4–10 keV versus 10–20 keV, and ∼ 10 d in 2–4 keV versus 10–20 keV. We found it difficult to explain the observed X-ray variation by a single energy injection with the one-zone synchrotron self-Compton (SSC) model, in which the soft lags in these three energy bands reflect the different cooling times of the relativistic electrons, by assuming the magnetic field and minimum Lorentz factor estimated from a broad-band spectral energy distribution. Alternatively, if the phenomenon is interpreted as cooling of Comptonizing electrons in a corona covering the accretion disk, the temperature of the corona producing the variable X-rays should be ∼ 10 keV for reconciliation with the soft lag in the energy range of 2–20 keV.