J/AJ/155/173 K2 light curve for K2-231 (Curtis+, 2018)
K2-231 b: a sub-Neptune exoplanet transiting a solar twin in Ruprecht 147.
Curtis J.L., Vanderburg A., Torres G., Kraus A.L., Huber D., Mann A.W.,
Rizzuto A.C., Isaacson H., Howard A.W., Henze C.E., Fulton B.J.,
Wright J.T.
<Astron. J., 155, 173-173 (2018)>
=2018AJ....155..173C 2018AJ....155..173C (SIMBAD/NED BibCode)
ADC_Keywords: Photometry; Optical; Exoplanets
Keywords: open clusters and associations: individual: (Ruprecht 147, NGC 6774);
planets and satellites: detection;
planets and satellites: gaseous planets;
stars: individual: (K2-231, EPIC 21980081, CWW 93,
2MASS J19162203-1546159)
Abstract:
We identify a sub-Neptune exoplanet (Rp=2.5±0.2R⊕)
transiting a solar twin in the Ruprecht 147 star cluster (3Gyr, 300pc,
[Fe/H]=+0.1dex). The ∼81 day light curve for EPIC 219800881 (V=12.71)
from K2 Campaign 7 shows six transits with a period of 13.84 days, a
depth of ∼0.06%, and a duration of ∼4hr. Based on our analysis of
high-resolution MIKE spectra, broadband optical and NIR photometry,
the cluster parallax and interstellar reddening, and isochrone models
from PARSEC, Dartmouth, and MIST, we estimate the following properties
for the host star: M*=1.01±0.03M☉, R*=0.95±0.03R☉,
and Teff=5695±50K. This star appears to be single based on our
modeling of the photometry, the low radial velocity (RV) variability
measured over nearly 10yr, and Keck/NIRC2 adaptive optics imaging and
aperture-masking interferometry. Applying a probabilistic mass-radius
relation, we estimate that the mass of this planet is Mp=7+5-3M⊕,
which would cause an RV semi-amplitude of K=2±1m/s that may be
measurable with existing precise RV facilities. After statistically
validating this planet with BLENDER, we now designate it K2-231b,
making it the second substellar object to be discovered in Ruprecht
147 and the first planet; it joins the small but growing ranks of 22
other planets and three candidates found in open clusters.
Description:
We downloaded the calibrated pixel-level data from the Barbara A.
Mikulski Archive for Space Telescopes (MAST), extracted a light
curve, and corrected for K2 systematic effects following Vanderburg &
Johnson (2014PASP..126..948V 2014PASP..126..948V). See section 2 for further explanations.
On 2016 July 15, we used the MIKE spectrograph on the 6.5m Magellan
Clay Telescope at Las Campanas Observatory in Chile to acquire a
spectrum of K2-231 with the 0.70" slit, corresponding to a spectral
resolution of R=42000.
We also acquired natural guide star AO imaging in K' (λ=2.124um)
with NIRC2 on the Keck II telescope. The observations were acquired,
reduced, and analyzed following Kraus+ (2016, J/AJ/152/8).
EPIC 219800881 was also targeted by the following programs:
"Statistics of Variability in Main-Sequence Stars of Kepler 2 Fields 6
and 7" (PI: Guzik; GO 7016), "The Masses and Prevalence of Small
Planets with K2--Cycle 2" (PI: Howard; GO 7030), and "K2 follow-up of
the nearby, old open cluster Ruprecht 147" (PI: Nascimbeni; GO 7056).
Objects:
------------------------------------------------------
RA (ICRS) DE Designation(s)
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19 16 22.04 -15 46 16.0 EPIC 219800881 = K2-231
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File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
fig1.dat 31 3675 K2 light curve for EPIC 219800881
(Data behind Figure 1)
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See also:
II/336 : AAVSO Photometric All Sky Survey (APASS) DR9 (Henden+, 2016)
I/339 : Hot Stuff for One Year (HSOY) (Altmann+, 2017)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
J/ApJS/152/261 : Ca II emission in nearby stars (Wright+, 2004)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/ApJ/687/1264 : Age estimation for solar-type dwarfs (Mamajek+, 2008)
J/A+A/512/A54 : Teff and Fbol from Infrared Flux Method (Casagrande+, 2010)
J/ApJS/190/1 : A survey of stellar families (Raghavan+, 2010)
J/ApJ/725/331 : Astrometry in the Galactic Center (Yelda+, 2010)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/ApJ/731/8 : Multiple star formation in Taurus-Auriga (Kraus+, 2011)
J/A+A/529/A75 : Limb-darkening coefficients (Claret+, 2011)
J/ApJ/733/L9 : Stellar rotation for 71 NGC 6811 members (Meibom+, 2011)
J/ApJ/756/L33 : RVs of 2 hot Jupiters in Praesepe (Quinn+, 2012)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/AJ/145/134 : RVs of 108 stars in Ruprecht 147 (Curtis+, 2013)
J/ApJS/208/9 : Intrinsic colors & temp. of PMS stars (Pecaut+, 2013)
J/ApJS/210/20 : Small Kepler planets radial velocities (Marcy+, 2014)
J/A+A/564/A125 : AGN Torus model comparison of AGN in CDFS (Buchner+, 2014)
J/AJ/150/97 : RVs in M67. I. 1278 candidate members (Geller+, 2015)
J/ApJS/222/14 : Planetary cand. from 1st yr K2 mission (Vanderburg+, 2016)
J/A+A/588/A118 : Pr0211 RVs, photom. & activity indexes (Malavolta+, 2016)
J/ApJS/224/2 : K2 EPIC stellar data for 138600 targets (Huber+, 2016)
J/AJ/152/8 : Stellar mult. impact on planetary syst. I. (Kraus+, 2016)
J/ApJ/825/19 : Mass-radius relationship for planets (Wolfgang+, 2016)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/A+A/594/A100 : K2 new planetary and EB candidates (Barros+, 2016)
J/MNRAS/463/1780 : Exoplanet candidates in Praesepe (M 44) (Libralato+, 2016)
J/MNRAS/463/1831 : M67 Kepler/K2 variable stars (Nardiello+, 2016)
J/ApJ/834/17 : Mass+rad. of planets, moons, low mass stars (Chen+, 2017)
J/ApJ/835/25 : Calibrated solar S-index time series (Egeland+, 2017)
J/A+A/603/A85 : M67 stars radial velocities (Brucalassi+, 2017)
J/ApJ/844/102 : KIC star plx from asteroseismology vs Gaia (Huber+, 2017)
J/AJ/154/109 : California-Kepler Survey (CKS). III. Radii (Fulton+, 2017)
Byte-by-byte Description of file: fig1.dat
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Bytes Format Units Label Explanations
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1- 9 F9.4 d BJD Observation date, BJD-2454833
11- 20 F10.8 --- Flux-Norm [0.98/1.02] Normalized flux (1)
22- 31 F10.8 --- Flux-Detr [0.99/1.01] Detrended flux (2)
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Note (1): Flux extracted using a circular moving aperture to exclude nearby
stars with an aperture of 2.3207943 pixels = 9 arcseconds. Normalized to 1.
Note (2): Flattened flux using the best-fit low-frequency model.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 28-Jan-2020