Thursday, May 26, 2016

A Super-Jupiter in an Extreme Planetary System

Figure 1: Artist's impression of a gas giant planet.

Santos et al. (2016) present the discovery of a super-Jupiter in a very eccentric long-period orbit around a host star that also has a hot-Neptune in a close-in orbit around it. The super-Jupiter is identified as HD 219828 c. Its orbital period is 13.1 years and it is estimated to have at least 15.1 times the mass of Jupiter. It also has a highly eccentric orbit with eccentricity 0.81. In the same planetary system, but much close to the host star, lies the hot-Neptune HD 219828 b. The orbital period of HD 219828 b is 3.83 days and it is estimated to have at least 21 times the mass of Earth.

The host star in this planetary system is a G0IV star that has evolved slightly beyond the main sequence. It has 3.08 times the Sun's luminosity, 1.23 ± 0.10 times the Sun's mass, 1.69 times the Sun's radius and an estimated effective temperature of 5891 ± 18 K. This extreme planetary system is estimated to be ~250 light years away. Dynamical simulations show that the orbits of HD 219828 b and HD 219828 c are both stable in the long run. Additionally, the large mass of HD 219828 c places it at the mass boundary between gas giant planets and brown dwarfs.

Figure 2: Top and middle plots: phase-folded radial-velocity curves and data for the planets HD 219828 b and HD 219828 c, respectively. Santos et al. (2016)


Santos et al. (2016), "An extreme planetary system around HD219828. One long-period super Jupiter to a hot-neptune host star", arXiv:1605.06942 [astro-ph.EP]