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Oxford University Press, Monthly Notices of the Royal Astronomical Society, 4(490), p. 5103-5121, 2019

DOI: 10.1093/mnras/stz2856

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

This paper is made freely available by the publisher.
This paper is made freely available by the publisher.

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Data provided by SHERPA/RoMEO

Abstract

ABSTRACT 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 exoplanets. We use 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 3.5σ mass estimate of $M_\mathrm{ p} = 109^{+30}_{-32}$ 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 d that orbits a single star. We find that Kepler-103b has a mass of $M_{\text{p,b}} = 11.7^{+4.31}_{-4.72}$ M⊕ and Kepler-103c has a mass of $M_{\text{p,c}} = 58.5^{+11.2}_{-11.4}$ M⊕. These are 2.5σ and 5σ results, respectively. With radii of $R_{\text{p,b}} = 3.49^{+0.06}_{-0.05}$ R⊕ and $R_{\text{p,c}} = 5.45^{+0.18}_{-0.17}$ 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 d. 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.