Using HARPS-N to characterise the long-period planets in the PH-2 and Kepler-103 systems

Sophie C. Dubber, Annelies Mortier, Ken Rice, Chantanelle Nava, Luca Malavolta, Helen Giles, Adrien Coffinet, David Charbonneau, Andrew Vanderburg, Aldo S. Bonomo, Walter Boschin, Lars A. Buchhave, Andrew Collier Cameron, Rosario Cosentino, Xavier Dumusque, Adriano Ghedina, Avet Harutyunyan, Raphaelle D. Haywood, David Latham, Mercedes Lopez-MoralesGiusi Micela, Emilio Molinari, Francesco A. Pepe, David Phillips, Giampaolo Piotto, Ennio Poretti, Dimitar Sasselov, Alessandro Sozzetti, Stephane Udry

Research output: Contribution to journalArticlepeer-review


 We present confirmation of the planetary nature of PH-2b, as well as the first mass estimates for the two planets in the Kepler-103 system. PH-2b and Kepler-103c are both long-period and transiting, a sparsely-populated category of exoplanet. We use {\it Kepler} light-curve data to estimate a radius, and then use HARPS-N radial velocities to determine the semi-amplitude of the stellar reflex motion and, hence, the planet mass. For PH-2b we recover a 3.5-σ mass estimate of Mp=109+30−32 M⊕ and a radius of Rp=9.49±0.16 R⊕. This means that PH-2b has a Saturn-like bulk density and is the only planet of this type with an orbital period P>200 days that orbits a single star. We find that Kepler-103b has a mass of Mp,b=11.7+4.31−4.72 M⊕ and Kepler-103c has a mass of Mp,c=58.5+11.2−11.4 M⊕. These are 2.5σ and 5σ results, respectively. With radii of Rp,b=3.49+0.06−0.05 R⊕, and Rp,c=5.45+0.18−0.17 R⊕, these results suggest that Kepler-103b has a Neptune-like density, while Kepler-103c is one of the highest density planets with a period P>100 days. By providing high-precision estimates for the masses of the long-period, intermediate-mass planets PH-2b and Kepler-103c, we increase the sample of long-period planets with known masses and radii, which will improve our understanding of the mass-radius relation across the full range of exoplanet masses and radii.

Original languageEnglish
JournalMonthly Notices of the Royal Astronomical Society
Publication statusPublished - 12 Oct 2019


  • astro-ph.EP


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