标题： CH Cygni II：不稳定盘的光学闪烁 显示英文标题

标题： CH Cygni II: Optical Flickering from an Unstable Disk

摘要： CH Cygni自1963年共生活动开始时开始产生快速的随机光学变化。 我们利用1997年至2000年间这种闪烁的变化来诊断这段时间内吸积盘的状态。 在1998年的高态期间，B波段闪烁成分的亮度通常比1997年和2000年的低态高出20倍以上。 因此，产生闪烁的物理过程或区域也是导致1998年高态期间大光学流量增加的主要原因。 假设CH Cygni的快速随机光学变化与新星爆发变星一样来自吸积盘，那么通过盘的吸积率的变化导致了1998年的明亮状态。 根据Hinkle等人和Eyres等人的星历表和解释，在1999年所有闪烁现象消失，当时正在吸积的白矮星被一颗以大约14年周期运行的红巨星遮挡。 我们没有发现CH Cygni光学发射中存在周期性或准周期振荡的证据，并讨论了这对该系统的磁力螺旋模型的影响。 作为螺旋模型的一个替代方案，我们提出CH Cygni的活动是由通过具有热黏性不稳定性盘的吸积驱动的，类似于被认为存在于矮新星中的不稳定性，并且被认为是为FU Orionis主序前星和软X射线暂现源所建议的。 显示英文摘要

摘要： CH Cygni began producing rapid, stochastic optical variations with the onset of symbiotic activity in 1963. We use changes in this flickering between 1997 and 2000 to diagnose the state of the accretion disk during this time. In the 1998 high state, the luminosity of the B-band flickering component was typically more than 20 times higher than in the 1997 and 2000 low states. Therefore, the physical process or region that produces the flickering was also primarily responsible for the large optical flux increase in the 1998 high state. Assuming that the rapid, stochastic optical variations in CH Cygni come from the accretion disk, as in cataclysmic variable stars, a change in the accretion rate through the disk led to the 1998 bright state. All flickering disappeared in 1999, when the accreting WD was eclipsed by the red giant orbiting with a period of approximately 14 yr, according to the ephemeris of Hinkle et al. and the interpretation of Eyres et al. We did not find any evidence for periodic or quasi-periodic oscillations in the optical emission from CH Cygni in either the high or low state, and we discuss the implications for magnetic propeller models of this system. As one alternative to propeller models, we propose that the activity in CH Cygni is driven by accretion through a disk with a thermal-viscous instability, similar to the instabilities believed to exist in dwarf novae and suggested for FU Ori pre-main-sequence stars and soft X-ray transients.