Status Report

he Mass of Kepler-93b and The Composition of Terrestrial Planets

By SpaceRef Editor
January 23, 2015
Filed under , , ,

Courtney D. Dressing, David Charbonneau, Xavier Dumusque, Sara Gettel, Francesco Pepe, Andrew Collier Cameron, David W. Latham, Emilio Molinari, Stephane Udry, Laura Affer, Aldo S. Bonomo, Lars A. Buchhave, Rosario Cosentino, Pedro Figueira, Aldo F. M. Fiorenzano, Avet Harutyunyan, Raphaelle D. Haywood, John Asher Johnson, Mercedes Lopez-Morales, Christophe Lovis, Luca Malavolta, Michel Mayor, Giusi Micela, Fatemeh Motalebi, Valerio Nascimbeni, David F. Phillips, Giampaolo Piotto, Don Pollacco, Didier Queloz, Ken Rice, Dimitar Sasselov, Damien Segransan, Alessandro Sozzetti, Andrew Szentgyorgyi, Chris Watson

(Submitted on 30 Dec 2014)

Kepler-93b is a 1.478 +/- 0.019 Earth radius planet with a 4.7 day period around a bright (V=10.2), astroseismically-characterized host star with a mass of 0.911+/-0.033 solar masses and a radius of 0.919+/-0.011 solar radii. Based on 86 radial velocity observations obtained with the HARPS-N spectrograph on the Telescopio Nazionale Galileo and 32 archival Keck/HIRES observations, we present a precise mass estimate of 4.02+/-0.68 Earth masses. The corresponding high density of 6.88+/-1.18 g/cc is consistent with a rocky composition of primarily iron and magnesium silicate. We compare Kepler-93b to other dense planets with well-constrained parameters and find that between 1-6 Earth masses, all dense planets including the Earth and Venus are well-described by the same fixed ratio of iron to magnesium silicate. There are as of yet no examples of such planets with masses > 6 Earth masses: All known planets in this mass regime have lower densities requiring significant fractions of volatiles or H/He gas. We also constrain the mass and period of the outer companion in the Kepler-93 system from the long-term radial velocity trend and archival adaptive optics images. As the sample of dense planets with well-constrained masses and radii continues to grow, we will be able to test whether the fixed compositional model found for the seven dense planets considered in this paper extends to the full population of 1-6 Earth mass planets.

Comments: 8 pages, 4 figures. Accepted for publication in ApJ

Subjects: Earth and Planetary Astrophysics (astro-ph.EP); Solar and Stellar Astrophysics (astro-ph.SR)

Cite as: arXiv:1412.8687 [astro-ph.EP] (or arXiv:1412.8687v1 [astro-ph.EP] for this version)

Submission history

From: Courtney Dressing 

[v1] Tue, 30 Dec 2014 17:02:41 GMT (124kb)

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