4U 1608–52 is a soft X-ray transient. The analysis presented here of a particular part of its X-ray activity uses observations of RXTE/ASM and Swift/BAT. We show a time segment (MJD 54262–MJD 55090) (828 d) in which 4U 1608–52 behaved as a quasi-persistent X-ray source with a series of bumps, with a complicated relation between the evolution of fluxes in the soft (1.5–12 keV) and the hard (15–50 keV) X-ray regions. We ascribe these bumps to a series of propagations of heating and cooling fronts over the inner disk region without any transitions to the true quiescence. 4U 1608–52 oscillated around the boundary between the dominance of the Comptonized component and the dominance of the multicolor accretion disk in its luminosity. Only some of the bumps in this series were accompanied by a transition from the hard to the soft state; if it occurred, it displayed a strong hysteresis effect. The hard-band emission with the dominant Comptonized component was present for most of this active state and showed a cycle of about 40 d. We argue that the cyclic variations of flux come from the inner disk region, not, e.g., from a jet. We also discuss the observed behavior of 4U 1608–52 in the context of other quasi-persistent low-mass X-ray binaries.

中文翻译：

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4U 1608–52作为准持久X射线源

4U 1608–52是软X射线瞬变。此处介绍的有关其X射线活动的特定部分的分析使用了RXTE / ASM和Swift / BAT的观测结果。我们显示了一个时间段（MJD 54262–MJD 55090）（828 d），其中4U 1608–52表现为具有一系列凸点的准持久X射线源，并且在软磁通量的演化之间存在复杂的关系（1.5–12 keV）和硬（15–50 keV）X射线区域。我们将这些隆起归因于一系列加热和冷却前沿在内部磁盘区域上的传播，而没有任何转变为真正的静止状态。4U 1608–52在色度分量的占优与多色吸积盘的亮度之间的边界附近振荡。这个系列中只有一些颠簸伴随着从硬状态到软状态的转变。如果发生的话 它显示出很强的磁滞效应。在大多数这种活性状态中都存在具有主要Comptonized成分的硬带发射，并显示出约40 d的周期。我们认为通量的周期性变化来自内盘区域，而不是来自射流。我们还讨论了在其他准持久性低质量X射线双星环境下4U 1608–52的行为。