SU UMa型矮新星Z Cha的食特征与超驼峰演化
Eclipse Properties and Superhump Evolution in the SU UMa-Type Dwarf Nova Z Cha
- Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）
- University of Chinese Academy of Sciences（中国科学院大学）
- Department of Astronomy, School of Physics and Astronomy, Yunnan University（云南大学物理与天文学院天文学系）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
利用TESS高节奏测光研究矮新星Z Cha，通过食深、O--C和正超驼峰振幅揭示偏心进动盘演化，并在静默期发现可能与负超驼峰共存的信号。
AI中文摘要：
大规模时域巡天的出现为理解激变变星（CVs）中吸积盘的演化带来了机遇与挑战。利用凌日系外行星勘测卫星（TESS）的高节奏测光数据，我们研究了食双星SU UMa型矮新星Z Cha。利用食作为天然探针，我们通过食深、食极小时间的O--C以及正超驼峰（PSH）振幅的变化来考察吸积盘的演化。在超级爆发期间，这三个量均表现出周期约为2天的准周期调制，与偏心盘的进动周期一致。我们将这些相关变化解释为偏心进动盘的证据：O--C追踪系统亮度中心的周期性位移，而食深和PSH振幅则随盘凸起相对于视线的取向而变化。在静默期（第13和93扇区），周期约为0.0762天的PSH显示出线性递减的振幅和周期，表明偏心盘逐渐收缩且进动减慢。值得注意的是，在相同的静默区间内出现了一个周期约为0.0729天（ε⁻≈-0.02）的相干信号。该信号可能代表与PSH共存的负超驼峰（NSHs），尽管目前的数据尚不能排除其为PSH的轨道边带。若确认为NSHs，其与PSH的共存将对经典的倾斜盘模型提出挑战，并可通过偏心盘的逆行拱线进动来解释，其中内盘逆行进动（产生NSHs）而外盘顺行进动（产生PSHs）；这一解释有待进一步观测验证。
英文摘要：
The advent of large-scale time-domain surveys provides both opportunities and challenges for understanding accretion disk evolution in cataclysmic variables (CVs). Using high-cadence photometry from the Transiting Exoplanet Survey Satellite (TESS), we investigate the eclipsing SU UMa-type dwarf nova Z Cha. Leveraging eclipses as a natural probe, we examine the evolution of the accretion disk through variations in eclipse depth, O--C of eclipse minima, and positive superhump (PSH) amplitude. During superoutbursts, all three quantities exhibit quasi-periodic modulations with a common period of $\sim$2 days, consistent with the precession period of an eccentric disk. We interpret these correlated variations as evidence of an eccentric, precessing disk: O--C traces the periodic shift of the system's brightness center, while eclipse depth and PSH amplitude vary with the orientation of the disk bulge relative to the line of sight. In quiescence (Sectors 13 and 93), PSHs with periods of $\sim$0.0762 days show linearly decreasing amplitudes and periods, indicating gradual shrinkage of the eccentric disk and a slowing precession. Remarkably, a coherent signal with a period of $\sim$0.0729~days ($ε^{-}\approx-0.02$) appears in the same quiescent intervals. This signal may represent negative superhumps (NSHs) coexisting with PSHs, although an orbital sideband of the PSH cannot presently be excluded with the available data. If confirmed as NSHs, their coexistence with PSHs would challenge the classical tilted-disk model, and could be explained by retrograde apsidal precession of an eccentric disk, where the inner disk precesses retrogradely (NSHs) and the outer disk progradely (PSHs); this interpretation remains to be tested by further observations.
