On November 5,  the Astrophysical Journal Supplement Series published the latest research results of Yunnan Observatories’ Binary and Variable Group. This group has monitored a dwarf nova V2051 Oph in Southern District for more than 7 years, and they found a Jovian giant planet orbiting around it, which reveals that cataclysmic variables are also planetary hosting stars. This finding also enriches people’s understanding about the diversified exoplanets.  

Normally, a dwarf nova is a close binary star system consisting of a white dwarf and a red dwarf. After capturing substances from its companion star, a white dwarf forms an accretion disk. One distinguishing feature of such cataclysmic binary is that due to the instability of the accretion disk, it would have quasi-periodic outbreaks. Its luminosity suddenly increases several even more than ten times before gradually decreasing. Its average outbreak period ranges from about 10 to 200 days. V2051 Oph is one of few dwarf novae which occur total eclipse. B band eclipsing depth is about 2.5 magnitudes. Its period is about 90 minutes, namely, the white dwarf and the red dwarf companion orbiting around each other in 90 minutes. As in the Southern District (declination: -25°48′30″), it is difficult for most international telescopes to observe V2051 Oph.

From June 2008, Researcher Qian Shengbang, Dr. Han Zhongtao and other research staff have photometrically observed V2051 Oph for more than 7 years using the 2.4-m Telescope, the 1.0-m reflecting telescope at Yunnan Observatories and the 2.15-m Jorge Sahade telescope (JST) at Complejo Astronómico El Leoncito (CASLEO), San Juan, Argentina. They found that the occultation light signal observed presents cyclical changes: the period of the cyclic oscillation and the amplitude are about 21.64 years and 28.4 s, respectively. This result reveals that there exists a Jovian giant planet orbiting around V2051 Oph at an orbital separation of about 9 astronomical units (1 AU is defined as the average distance between the Sun and the Earth). Detailed calculations show that this Jovian giant planet’s minimum mass is 7.3 times Jupiter mass, and its orbital eccentricity is 0.37 (see the figure below). Astronomical spectacles such as the cataclysmic binary’s beautiful accretion disk and its magnificent outbursts—which cannot be easily observed from earth—can be effortlessly and closely witnessed from this Jovian giant planet!  

This work is supported by Chinese Natural Science Foundation (No.11133007 and No. 11325315) and other programs. Information regarding the paper: Qian S.-B., Han Z. T., Fernández Lajús, E., Zhu L. Y., Li L. J., Liao, W. P., and Zhao, E. G., Long-term Decrease and Cyclic Variation in the Orbital Period of the Eclipsing Dwarf Nova V2051 Oph, 2015, ApJS 221, 17.