K2-291b: A rocky super-Earth in a 2.2 day orbit

Molly R. Kosiarek, Sarah Blunt, Mercedes Lopez-Morales, Ian J. M. Crossfield, Evan Sinukoff, Erik A. Petigura, Erica J. Gonzales, Ennio Poretti, Luca Malavolta, Andrew W. Howard, Howard Isaacson, Raphaelle D. Haywood, David R. Ciardi, Makennah Bristow, Andrew Collier Cameron, David Charbonneau, Courtney D. Dressing, Pedro Figueira, Benjamin J. Fulton, Bronwen J. HardeeLea A. Hirsch, David W. Latham, Annelies Mortier, Chantanelle Nava, Joshua E. Schlieder, Andrew Vanderburg, Lauren Weiss, Aldo S. Bonomo, Francois Bouchy, Lars A. Buchhave, Adrien Coffinet, Mario Damasso, Xavier Dumusque, Christophe Lovis, Michel Mayor, Giusi Micela, Emilio Molinari, Francesco Pepe, David Phillips, Giampaolo Piotto, Ken Rice, Dimitar Sasselov, Damien Segransan, Alessandro Sozzetti, Stephane Udry, Chris Watson

Research output: Contribution to journalArticlepeer-review


EPIC 247418783 is a solar-type star with a radius of R_star = 0.899 $\pm$ 0.034 R_sun and mass of M_star=0.934 $\pm$ 0.038 M_sun. From K2 C13 data, we found one super-Earth planet (R_p = 1.589+0.095-0.072 R_Earth) transiting this star on a short period orbit (P = 2.225177 +6.6e-5 -6.8e-5 days). We followed this system up with adaptive-optic imaging and spectroscopy to derive stellar parameters, search for stellar companions, and determine a planet mass. From our 75 radial velocity measurements using HIRES on Keck I and HARPS-N on Telescopio Nazionale Galileo, we constrained the mass of EPIC 247418783b to M_p = 6.49 $\pm$ 1.16 M_Earth. We found it necessary to model correlated stellar activity radial velocity signals with a Gaussian process in order to more accurately model the effect of stellar noise on our data; the addition of the Gaussian process also improved the precision of this mass measurement. With a bulk density of 8.84+2.50-2.03 g cm-3, the planet is consistent with an Earth-like rock/iron composition and no substantial gaseous envelope. Such an envelope, if it existed in the past, was likely eroded away by photo-evaporation during the first billion years of the star's lifetime.
Original languageEnglish
Number of pages15
JournalAstronomical Journal
Publication statusPublished - 13 Feb 2019


  • astro-ph.EP


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