Friday, January 1, 2016

Red Dwarf Star Exciting a Massive Planet

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

HD 7449A is a Sun-like star with a massive planet identified as HD 7449Ab in orbit around it. Radial velocity measurements indicate that HD 7449Ab has at least ~7.8 times the mass of Jupiter and the plant is in a highly-elongated orbit around its host star. The minimum and maximum distance of HD 7449Ab from its host star is ~0.47 AU and ~4.19 AU, respectively. Furthermore, the orbital period of HD 7449Ab is ~1270 days.

More recent radial velocity measurements and dynamical analysis indicate that HD 7449A has a companion star identified as HD 7449B. HD 7449B is most likely a low-mass red dwarf star with ~0.2 times the Sun’s mass and it orbits HD 7449A at ~18 AU, with an orbital period of roughly 65 years. The orbit of HD 7449B is expected to be only mildly elongated. Dynamical studies show that HD 7449B may be exciting the orbit of HD 7449Ab, resulting in the planet’s highly-elongated orbit.

Figure 2: Radial velocity curve indicating the presence of HD 7449Ab. Rodigas et al. (2015)

Figure 3: Radial velocity curve indicating the presence of HD 7449B. Rodigas et al. (2015)

Rodigas et al. (2015), “MagAO Imaging of Long-period Objects (MILO). I. A Benchmark M Dwarf Companion Exciting a Massive Planet around the Sun-like Star HD 7449”, arXiv:1512.04540 [astro-ph.EP]