Detection and characterization of an ultra-dense sub-Neptunian planet orbiting the Sun-like star K2-292

We present the discovery and characterization of a new transiting planet from Campaign 17 of the Kepler extended mission K2. The planet K2-292 b is a warm sub-Neptune on a 17 day orbit around a bright (V = 9.9 mag) solar-like G3 V star with a mass and radius of M_⋆ = 1.00 ± 0.03 M_⊙ and R_⋆ = 1.09 ± 0.03 R_⊙, respectively. We modeled simultaneously the K2 photometry and CARMENES spectroscopic data and derived a radius of R_p=2.63_-0.10^+0.12 R_⊕ and mass of M_p=24.5_-4.4^+4.4 M_⊕, yielding a mean density of ρ_p=7.4_-1.5^+1.6 g cm^-3, which makes it one of the densest sub-Neptunian planets known to date. We also detected a linear trend in the radial velocities of K2-292 (γ˙_RV = -0.40_-0.07^+0.07 m s^-1 d^-1) that suggests a long-period companion with a minimum mass on the order of 33 M_⊕. If confirmed, it would support a formation scenario of K2-292 b by migration caused by Kozai-Lidov oscillations.

The light curve is only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/623/A114