K2-291 b: A rocky super-Earth in a 2.2 day orbit. (arXiv:1901.04558v2 [astro-ph.EP] UPDATED)

K2-291 b: A rocky super-Earth in a 2.2 day orbit. (arXiv:1901.04558v2 [astro-ph.EP] UPDATED)
<a href="http://arxiv.org/find/astro-ph/1/au:+Kosiarek_M/0/1/0/all/0/1">Molly R. Kosiarek</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Blunt_S/0/1/0/all/0/1">Sarah Blunt</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lopez_Morales_M/0/1/0/all/0/1">Mercedes Lopez-Morales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Crossfield_I/0/1/0/all/0/1">Ian J.M. Crossfield</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sinukoff_E/0/1/0/all/0/1">Evan Sinukoff</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Petigura_E/0/1/0/all/0/1">Erik A. Petigura</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Gonzales_E/0/1/0/all/0/1">Erica J. Gonzales</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Poretti_E/0/1/0/all/0/1">Ennio Poretti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Malavolta_L/0/1/0/all/0/1">Luca Malavolta</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Howard_A/0/1/0/all/0/1">Andrew W. Howard</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Isaacson_H/0/1/0/all/0/1">Howard Isaacson</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Haywood_R/0/1/0/all/0/1">Raphaelle D. Haywood</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Ciardi_D/0/1/0/all/0/1">David R. Ciardi</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bristow_M/0/1/0/all/0/1">Makennah Bristow</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Cameron_A/0/1/0/all/0/1">Andrew Collier Cameron</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Charbonneau_D/0/1/0/all/0/1">David Charbonneau</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dressing_C/0/1/0/all/0/1">Courtney D. Dressing</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Figueira_P/0/1/0/all/0/1">Pedro Figueira</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Fulton_B/0/1/0/all/0/1">Benjamin J. Fulton</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hardee_B/0/1/0/all/0/1">Bronwen J.Hardee</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Hirsch_L/0/1/0/all/0/1">Lea A. Hirsch</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Latham_D/0/1/0/all/0/1">David W. Latham</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mortier_A/0/1/0/all/0/1">Annelies Mortier</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Nava_C/0/1/0/all/0/1">Chantanelle Nava</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Schlieder_J/0/1/0/all/0/1">Joshua E. Schlieder</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Vanderburg_A/0/1/0/all/0/1">Andrew Vanderburg</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Weiss_L/0/1/0/all/0/1">Lauren Weiss</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bonomo_A/0/1/0/all/0/1">Aldo S. Bonomo</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Bouchy_F/0/1/0/all/0/1">Francois Bouchy</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Buchhave_L/0/1/0/all/0/1">Lars A. Buchhave</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Coffinet_A/0/1/0/all/0/1">Adrien Coffinet</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Damasso_M/0/1/0/all/0/1">Mario Damasso</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Dumusque_X/0/1/0/all/0/1">Xavier Dumusque</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Lovis_C/0/1/0/all/0/1">Christophe Lovis</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Mayor_M/0/1/0/all/0/1">Michel Mayor</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Micela_G/0/1/0/all/0/1">Giusi Micela</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Molinari_E/0/1/0/all/0/1">Emilio Molinari</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Pepe_F/0/1/0/all/0/1">Francesco Pepe</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Phillips_D/0/1/0/all/0/1">David Phillips</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Piotto_G/0/1/0/all/0/1">Giampaolo Piotto</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Rice_K/0/1/0/all/0/1">Ken Rice</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sasselov_D/0/1/0/all/0/1">Dimitar Sasselov</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Segransan_D/0/1/0/all/0/1">Damien Segransan</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Sozzetti_A/0/1/0/all/0/1">Alessandro Sozzetti</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Udry_S/0/1/0/all/0/1">Stephane Udry</a>, <a href="http://arxiv.org/find/astro-ph/1/au:+Watson_C/0/1/0/all/0/1">Chris Watson</a>

K2-291 (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.

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