Eclipse Properties and Superhump Evolution in the SU UMa-type Dwarf Nova Z Cha
4 affiliations
- 1Chinese Academy of Sciences
- 2University of Chinese Academy of Sciences
- 3Yunnan University
- 4Astrofísica de La Plata (CCT La Plata - CONICET/UNLP)
Abstract
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 quasiperiodic modulations with a common period of ∼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 ∼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 ∼0.0729 days ( ϵ ⁻ ≈ −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.
Versions
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BibTeX
@article{sun2026eclipse,
title = {{Eclipse Properties and Superhump Evolution in the SU UMa-type Dwarf Nova Z Cha}},
author = {Qi-Bin Sun and Sheng-Bang Qian and Li-Ying Zhu and Qin-Mei Li and Wen-Ping Liao and Fu-Xing Li and Wen-Xu Lin and Min-Yu Li and Ping Li and Zi-Mo Li and Tao Wang and Mao-Han Zhang and Eduardo Fernández Lajús},
journal = {The Astrophysical Journal},
year = {2026},
month = oct,
doi = {10.3847/1538-4357/aeaa54},
url = {https://iopscience.iop.org/article/10.3847/1538-4357/aeaa54},
note = {CC BY 4.0},
}
RIS
TY - JOUR
TI - Eclipse Properties and Superhump Evolution in the SU UMa-type Dwarf Nova Z Cha
AU - Qi-Bin Sun
AU - Sheng-Bang Qian
AU - Li-Ying Zhu
AU - Qin-Mei Li
AU - Wen-Ping Liao
AU - Fu-Xing Li
AU - Wen-Xu Lin
AU - Min-Yu Li
AU - Ping Li
AU - Zi-Mo Li
AU - Tao Wang
AU - Mao-Han Zhang
AU - Eduardo Fernández Lajús
PY - 2026
DA - 2026/10/27
JO - The Astrophysical Journal
DO - 10.3847/1538-4357/aeaa54
UR - https://iopscience.iop.org/article/10.3847/1538-4357/aeaa54
AB - 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 quasiperiodic modulations with a common period of ∼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 ∼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 ∼0.0729 days ( ϵ ⁻ ≈ −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.
SN - 1538-4357
SN - 0004-637X
ER -