Two Super-Earth-Sized Planets Transiting HD 3167

HD 3167 is a Sun-like star with ~0.88 times the mass and ~0.83 times the radius of the Sun. It is located ~150 light years away and its effective temperature is 5367 ± 50 K. Using data from the K2 mission, Vanderburg et al. (2016) present the discovery of two super-Earth-sized planets transiting HD 3167. The two planets are identified as HD 3167b and HD 3167c.

Figure 1: Artist's impression of an exoplanet.

Figure 2: Light curves indicating the presence of HD 3167b and HD 3167c. Vanderburg et al. (2016)

The inner planet, HD 3167b, has 1.595 ± 0.084 times the radius of Earth and its orbital period is only 23 hours. HD 3167b is an example of an ultra short period planet. Its equilibrium temperature is estimated to be 1560 ± 130 K. HD 3167b is expected to be predominantly rocky as the intense radiation from the host star is likely to have stripped away any thick gaseous envelope. The outer planet, HD 3167c, has 2.89 ± 0.20 times the radius of Earth and its orbital period is 29.845 days. The planet's equilibrium temperature is estimated to be 500 ± 40 K.

HD 3167 is one of the closest and brightest stars with multiple transiting planets, making it a good target for follow-up observations such as transmission spectroscopy and radial velocity observations. The two planets around HD 3167 have widely separated orbital periods. The orbital period of HD 3167c is more than 30 times larger than the orbital period of HD 3167b. This could indicate the presence of additional, non-transiting planets between HD 3167b and HD 3167c.

Reference: Vanderburg et al. (2016), "Two Small Planets Transiting HD 3167", arXiv:1607.05248 [astro-ph.EP]