Researchers Discover Special Eclipsing Dwarf Nova (Cosmology)

In a study published in The Astronomical Journal, Dr. HAN Zhongtao and Prof. QIAN Shengbang from Yunnan Observatories of the Chinese Academy of Sciences, Prof. Boonrucksar Soonthornthum from National Astronomical Research Institute of Thailand, and the collaborators, identified an eclipsing Z Cam-type dwarf nova, IPHAS J051814.34+294113.2 (IPHAS J0518). They found that IPHAS J0518 has a bimodal distribution of the outbursts, and that the complex behavior of accretion disk during outburst is a combined effect of the varying disc size and radial temperature gradient.Dwarf novae are a subtype of cataclysmic variables (CVs), and typically exhibit multiple optical outbursts. Z Cam-type stars are believed to share properties of both thermally unstable dwarf novae and thermally stable nova-like variables.

Eclipsing dwarf nova allows people to measure accurate parameters of the binary components and their orbital period changes, which is crucial for improving the understanding on CV evolution. The number of dwarf novae has been growing rapidly due to modern astronomical surveys. However, only a few eclipsing Z Cam stars have been known. The study of new eclipsing dwarf novae is important to test the theoretical models of the outburst.

The long-term light curves of IPHAS J0518 from Transiting Exoplanet Survey Satellite (TESS) and Zwicky Transient Facility (ZTF) telescope showed the alternation of long outbursts and short outbursts. Meanwhile, TESS data displayed two outbursts, as well as the striking eclipsing light curve.

Using the generalized Lomb-Scargle method and the weighted wavelet transform, the researchers obtained precise orbital period and the recurrence time of long and short outbursts.

By combining the derived outburst parameters and Large Sky Area Multi-Object Fiber Spectroscopy Telescope (LAMOST) spectra, the researchers discovered and identified IPHAS J0518 to be an eclipsing Z Cam-type dwarf nova. These data were also used to constrain the binary parameters.

Besides, the researchers analyzed the accretion disc eclipse and found that the total disc eclipse is possible during quiescence, whereas during outburst the disc would be only partially obscured. Further studies showed that the complex behavior of accretion disk during outburst appears more complicated than the single mechanism driven, and should be a combined effect of the varying disc size and radial temperature gradient.

The discovery of IPHAS J0518 is expected to reveal its disk structure and the brightness distribution, and allows people to trace the disk evolution with time during outburst.

Reference

TESS and ZTF Observations of an Eclipsing Z Cam-type Dwarf Nova IPHAS J051814.34+294113.2


Provided by Chinese Academy of Sciences

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