K2-161b: a low-density super-Neptune on an eccentric orbit
Abstract
We report the discovery of K2-161b, which was first identified as a planetary candidate from Kepler K2 photometry of Campaign 14, and whose planetary nature and orbital parameters were then confirmed with precision radial velocities. K2-161b is half as massive as Saturn (M_P= 0.179 ± 0.021 MJ), and has a radius of R_P= 0.840 ± 0.011 R_J, which translates into a bulk density of {ρ _P}=0.37 ± 0.05 g cm^{-3}. K2-161b transits its slightly evolved G-type host star (M_{\star }= 1.105 ± 0.019 M_{⊙ }, R_{\star }= 1.669 ± 0.022 R_{⊙ }) every 11.633 64 ± 0.000 10 d and presents a significantly eccentric orbit (e = 0.420 ± 0.034). We estimate a relatively short circularization time-scale of 1.8 Gyr for the planet, but given the advanced age of the system we expect the planet to be engulfed by its evolving host star in ∼1 Gyr before the orbit circularizes. The low density of the planet coupled to the brightness of the host star (J = 9.4) makes this system one of the best candidates known to date in the super-Neptune regime for atmospheric characterization via transmission spectroscopy, and to further study the transition region between ice and gas giant planets.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- February 2019
- DOI:
- 10.1093/mnras/sty3230
- arXiv:
- arXiv:1806.04073
- Bibcode:
- 2019MNRAS.483.1970B
- Keywords:
-
- techniques: photometric;
- techniques: radial velocities;
- planets and satellites: fundamental parameters;
- stars: fundamental parameters;
- stars: individual: K2-161;
- Astrophysics - Earth and Planetary Astrophysics;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- submitted to MNRAS, 11 pages, 10 figures