Using HARPSN to characterize the longperiod planets in the PH2 and Kepler103 systems
Abstract
We present confirmation of the planetary nature of PH2b, as well as the first mass estimates for the two planets in the Kepler103 system. PH2b and Kepler103c are both longperiod and transiting, a sparsely populated category of exoplanets. We use Kepler lightcurve data to estimate a radius, and then use HARPSN radial velocities to determine the semiamplitude of the stellar reflex motion and, hence, the planet mass. For PH2b we recover a 3.5σ mass estimate of M_ p = 109^{+30}_{32} M_{⊕} and a radius of R_{p} = 9.49 ± 0.16 R_{⊕}. This means that PH2b has a Saturnlike bulk density and is the only planet of this type with an orbital period P > 200 d that orbits a single star. We find that Kepler103b has a mass of M_{p,b} = 11.7^{+4.31}_{4.72} M_{⊕} and Kepler103c has a mass of M_{p,c} = 58.5^{+11.2}_{11.4} M_{⊕}. These are 2.5σ and 5σ results, respectively. With radii of R_{p,b} = 3.49^{+0.06}_{0.05} R_{⊕} and R_{p,c} = 5.45^{+0.18}_{0.17} R_{⊕}, these results suggest that Kepler103b has a Neptunelike density, while Kepler103c is one of the highest density planets with a period P > 100 d. By providing highprecision estimates for the masses of the longperiod, intermediatemass planets PH2b and Kepler103c, we increase the sample of longperiod planets with known masses and radii, which will improve our understanding of the massradius relation across the full range of exoplanet masses and radii.
 Publication:

Monthly Notices of the Royal Astronomical Society
 Pub Date:
 December 2019
 DOI:
 10.1093/mnras/stz2856
 arXiv:
 arXiv:1910.03518
 Bibcode:
 2019MNRAS.490.5103D
 Keywords:

 techniques: photometric;
 techniques: radial velocities;
 techniques: spectroscopic;
 planets and satellites: composition;
 Astrophysics  Earth and Planetary Astrophysics
 EPrint:
 Accepted for publication in MNRAS