近周期间隙矮新星YZ Cancri中与阶段相关的超驼峰波形演化与非平稳正超驼峰计时
Stage-dependent superhump waveform evolution and non-stationary positive-superhump timing in the near-period-gap dwarf nova YZ Cancri
- Yunnan Observatories, Chinese Academy of Sciences（中国科学院云南天文台）
- International Centre of Supernovae (ICESUN), Yunnan Key Laboratory of Supernova Research, Yunnan Observatories, CAS（超新星国际中心，云南省超新星研究重点实验室，中国科学院云南天文台）
- Key Laboratory for the Structure and Evolution of Celestial Objects, CAS（天体结构与演化重点实验室，中国科学院）
机构由 AI 辅助整理，请以论文原文为准。
AI总结：
本研究通过TESS和地面观测，发现矮新星YZ Cnc在超级爆发中正超驼峰波形按ST-DHd-DHs阶段演化，并测得周期和质量比，揭示吸积盘演化。
AI中文摘要：
我们基于几乎连续的凌日系外行星巡天卫星（TESS）测光和长基线地面观测，对近周期间隙的SU UMa型矮新星YZ Cancri进行了测光和计时研究。我们的主要观测结果是，正超驼峰（SH）波形在超级爆发（SOs）期间遵循可重复的、与阶段相关的序列。在两次覆盖良好的TESS超级爆发中，以及在长基线地面超级爆发样本中一致地，平台期波形从早期的锯齿状轮廓（ST），经过具有不等极大值的双峰轮廓（DHd），演变为具有几乎相似极大值的更对称的双峰轮廓（DHs）。全局和时间分辨的Lomb-Scargle周期图显示，正超驼峰时间尺度及其谐波附近的功率在超级爆发期间集中，而静默期和正常爆发期间缺乏可比较的持续超驼峰带信号。密集的TESS极大-极小计时序列在不同波形阶段显示出不同的时钟稳定性：前兆调制具有稍长的局部周期，中后期DHs平台是最规则的计时区间，而平台后演化受到相位切换和可能的次级/晚期超驼峰污染的影响。TESS数据还揭示了轮廓-时钟耦合，超驼峰振幅和上升/衰减持续时间与计时残差共同演化。作为次要计时约束，我们获得了基于TESS计时的平均正超驼峰周期$P'_{\rm sh}=0.09043(27)$天，对应于超驼峰过剩$4.03(31)\%$和近似质量比$q=0.175(11)$。可重复的ST-DHd-DHs序列使YZ Cnc成为周期间隙下边缘附近的一个有用系统，并且可能追踪与超级爆发期间偏心、进动吸积盘相关的光源的生长、重新分布、稳定和衰减。
英文摘要：
We present a photometric and timing study of the near-period-gap SU~UMa-type dwarf nova YZ~Cancri, based on nearly continuous Transiting Exoplanet Survey Satellite (TESS) photometry and long-baseline ground-based observations. Our main observational result is that the positive-superhump (SH) waveform follows a repeatable, stage-dependent sequence during superoutbursts (SOs). In the two well-covered TESS SOs, and consistently in the long-baseline ground-based SO sample, the plateau waveform evolves from an early saw-tooth profile (ST), through a double-humped profile with unequal maxima (DHd), to a more symmetric double-humped profile with nearly similar maxima (DHs). The global and time-resolved Lomb--Scargle periodograms show that power near the positive-SH time scale and its harmonics is concentrated during SOs, whereas quiescent and normal-outburst intervals lack a comparably persistent SH-band signal. The dense TESS maxima--minima timing sequence shows different clock stability in different waveform stages: precursor modulations have slightly longer local periods, the middle-to-late DHs plateau is the most regular timing interval, and the post-plateau evolution is affected by phase switching and possible secondary/late-SH contamination. The TESS data also reveal profile-clock coupling, with SH amplitude and rise/decay durations evolving together with the timing residuals. As a secondary timing constraint, we obtain a common TESS-timing-based mean positive-SH period of $P'_{\rm sh}=0.09043(27)$~d, corresponding to a SH excess of $4.03(31)\%$ and an approximate mass ratio of $q=0.175(11)$. The repeatable ST--DHd--DHs sequence makes YZ~Cnc a useful system near the lower edge of the period gap, and may trace the growth, redistribution, stabilization, and decay of the light source associated with an eccentric, precessing accretion disk during SOs.
