GX 340+0沿其Z型轨迹的光谱与时变演化
Spectral and Timing evolution of GX 340+0 along its Z-track
AI总结：
本文利用AstroSat数据研究Z型源GX 340+0，发现其Z型轨迹由黑体成分的非单调变化驱动，而康普顿化流量单调递减，并揭示了不同分支上约50 Hz和约6 Hz的QPO及其能量依赖和软滞后特性。
摘要：
我们利用AstroSat的SXT和LAXPC数据，对Z型源GX 340+0进行了光谱与时变研究。在观测期间，该源描绘出完整的Z型轨迹，从而能够对水平支、正常支和闪耀支（HB、NB和FB）以及硬顶点和软顶点（HA和SA）进行光谱演化研究。与包含盘成分的模型相比，由黑体成分和具有变化覆盖分数的热康普顿化冕组成的模型能更好且更物理地描述光谱。沿轨迹，康普顿化流量（以及覆盖分数）单调递减。正是黑体成分（温度和半径）发生非单调变化，从而导致了Z型轨迹行为。快速时变研究揭示，在HB、HA和NB上部存在约50 Hz的显著准周期振荡（QPO），而在其他分支则观测到约6 Hz的QPO。QPO的分数均方根随能量增加而增大，并在除SA和FB外的所有分支中表现出软滞后。
英文摘要：
We present the results from spectral and timing study of the Z source GX 340+0 using AstroSat's SXT and LAXPC data. During the observation the source traced out the complete Z-track, allowing for the spectral evolution study of the Horizontal, Normal and Flaring branches (HB, NB and FB) as well as the hard and soft apexes (HA and SA). The spectra are better and more physically described by a blackbody component and a hot Comptonizing corona with a varying covering fraction, rather than one having a disc component. Along the track, the Comptonized flux (as well as the covering fraction) monotonically decreases. It is the blackbody component (both the temperature and radius) which varies non-monotonically and hence gives rise to the Z-track behaviour. Rapid timing study reveals a prominent Quasi-periodic Oscillation (QPO) at ~ 50 Hz at the HB, HA and upper NB, while a QPO at ~ 6 Hz is seen for the other branches. The fractional r.m.s of the QPOs increase with energy and exhibit soft lags in all branches except SA and FB.
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