Two Hot Jupiters from K2 Campaign 4

1.3 MB·

by  Marshall C. Johnson

Accepted for Publicationin AJ
PreprinttypesetusingLATEXstyleemulateapjv.5/2/11
TWO HOT JUPITERS FROM K2 CAMPAIGN 4
Marshall C. Johnson1, Davide Gandolfi2,3, Malcolm Fridlund4,5,6, Szilard Csizmadia7, Michael Endl1,
Juan Cabrera7, William D. Cochran1, Hans J. Deeg8,9, Sascha Grziwa10, Ivan Ram´ırez1, Artie P. Hatzes11,
Philipp Eigmu¨ller7, Oscar Barraga´n2, Anders Erikson7, Eike W. Guenther11, Judith Korth10, Teet Kuutma12,
David Nespral8,9, Martin Pa¨tzold10, Enric Palle8,9, Jorge Prieto-Arranz8,9, Heike Rauer7,13,
and Joonas Saario12
Accepted forPublication inAJ
6
1
ABSTRACT
0
2 WeconfirmtheplanetarynatureoftwotransitinghotJupitersdiscoveredbytheKepler spacecraft’s
K2extendedmissioninitsCampaign4,usingpreciseradialvelocitymeasurementsfromFIES@NOT,
r
p HARPS-N@TNG,andthecoud´espectrographontheMcDonaldObservatory2.7mtelescope. K2-29b
A (EPIC211089792b)transitsaK1Vstarwithaperiodof3.2589263±0.0000015days;itsorbitisslightly
eccentric (e =0.084+0.032). It has a radius of R = 1.000+0.071 R and a mass of M = 0.613+0.027
−0.023 P −0.067 J P −0.026
0 M . Its host star exhibits significant rotational variability, and we measure a rotation period of
J
1 P = 10.777 ± 0.031 days. K2-30 b (EPIC 210957318b) transits a G6V star with a period of
rot
] 4.098503±0.000011 days. It has a radius of RP = 1.039+−00..005501 RJ and a mass of MP = 0.579+−00..002287
P MJ. The star has a low metallicity for a hot Jupiter host, [Fe/H]=−0.15±0.05.
E Subject headings: planets and satellites: detection — planets and satellites: individual: EPIC
. 211089792b, EPIC 210957318b — stars: fundamental parameters — stars: ro-
h
tation
p
-
o
r 1. INTRODUCTION Database14 (Han et al. 2014) lists more than 200 known
t hot Jupiters (P < 10 days, 0.3M < M < 13M ) as
s Morethantwodecadeshavenowelapsedsincethedis- J P J
a covery of the first exoplanet orbiting a main sequence of January 2016. Expanding this sample will allow ever
[ morefine-grainedexplorationsofcorrelationsamongpa-
star(Mayor & Queloz1995). Overthattimetremendous

technological advances have been made, allowing the rameters for this class of planets (mass, radius, orbital
2
period, temperature, stellar properties, etc.), as well as
v detection of Earth-size and approximately Earth-mass
the discovery of rare systems. A recent example of this
4 planets with both transits (e.g., Jontof-Hutter et al.
latter class is the WASP-47 system, which is unique in
4 2015) or radial velocities (RVs; e.g., Wright et al. 2016).
having two small planets orbiting in close proximity to
8 Nonetheless, hot Jupiters remain the easiest planets to
the hot Jupiter (Becker et al. 2015).
7 detect with both techniques, due to their largeradiiand
An expanded population of known hot Jupiters, and
0 masses and short orbital periods. The Exoplanet Orbit
thestatisticalexplorationsandfurtherobservationsthat
.
1 thiswillenable,canhelptoansweranumberofunsolved
0 problems regarding hot Jupiters. One such outstanding
6 1DepartmentofAstronomyandMcDonaldObservatory,Uni-
problem involves the origins of hot Jupiters. Ever since
versityofTexasatAustin,2515Speedway,StopC1400,Austin,
1
TX78712,USA;[email protected] the discovery of the first hot Jupiter, 51 Peg b, it has
v: 2Dipartimento di Fisica, Universit´a di Torino, via P. Giuria beenrecognizedthatformingtheseplanetsin situwould
1,10125Torino,Italy
Xi 3Landessternwarte K¨onigstuhl, Zentrum fu¨r Astronomie der be verydifficult (Mayor & Queloz1995). A wide variety
Universit¨at Heidelberg, K¨onigstuhl 12, 69117 Heidelberg, Ger- ofmechanisms havebeen proposedto bring hotJupiters
r many in from their formation locations outside the snow line
a 4Max-Planck-Institut fu¨r Astronomie, K¨onigstuhl 17, 69117 to where they are observed today (e.g., Lin et al. 1996;
Heidelberg,Germany
5Leiden Observatory, University of Leiden, PO Box 9513, Rasio & Ford 1996; Fabrycky & Tremaine 2007), and a
2300RA,Leiden,TheNetherlands great deal of work has been devoted to determining
6DepartmentofEarthandSpaceSciences,ChalmersUniver- which mechanisms actually produce hot Jupiters (e.g.,
sity of Technology, Onsala Space Observatory, 439 92 Onsala, Naoz et al.2012;Dawson & Murray-Clay2013). Despite
Sweden
7Institute ofPlanetaryResearch, GermanAerospace Center, this,thecontributionsofdifferentmigrationmechanisms
Rutherfordstrasse2,12489Berlin,Germany tothehotJupiterpopulation,andevenwhichisthedom-
8Instituto de Astrof´ısica de Canarias, 38205 La Laguna, inant migration mechanism, is still a matter of debate.
Tenerife,Spain There have even been recent suggestions that some hot
9Departamento de Astrof´ısica, Universidad de La Laguna,
and warm Jupiters (i.e., Jovian planets with periods of
38206LaLaguna, Spain
10Rheinisches Institut fu¨r Umweltforschung an der Univer- greater than approximately 10 days but interior to the
sit¨atzuK¨oln,AachenerStrasse209,50931K¨oln,Germany habitable zone–exact values depend upon the stellar pa-
11Thu¨ringer Landessternwarte Tautenburg, Sternwarte 5, D- rameters)mightformin situratherthanmigratingfrom
07778Tautenberg, Germany
12NordicOpticalTelescope,Apartado474,38700SantaCruz furtherout(Batygin et al.2015;Huang et al.2016). The
deLaPalma,Spain
13Center forAstronomyandAstrophysics, TUBerlin,Hard-
enbergstr. 36,10623Berlin,Germany 14 http://exoplanets.org/
2 Johnson et al.
expansion of the population of hot Jupiters, enabling lightcurvesweredecorrelatedusingthemovementofthe
more follow-up observations and the discovery of rare centroid as described in Vanderburg & Johnson (2014).
objects like WASP-47, can help to solve this problem. We also analyzed the light curves produced using their
The most prolific planet hunter to date is the Ke- methodology, which are publicly available16. We used
pler mission (Borucki et al. 2010), which has produced aperture sizes of approximately60 pixels to produce our
thousands of planet candidates (Coughlin et al. 2015) ownlightcurves,whiletheVanderburg & Johnson(2014)
and hundreds of validated or confirmed planets (e.g. lightcurves utilize aperture sizes of 29 and 18 pixels for
Rowe et al. 2014). After the failure of a second reaction K2-29 and K2-30, respectively.
wheel,however,theKeplerspacecraftwasnolongerable After extraction of the light curves, we searched for
to keep pointing at the original Kepler field, and was transit signals using the DST algorithm (Cabrera et al.
repurposed for the K2 extended mission (Howell et al. 2012) and the EXOTRANS pipeline (Grziwa et al.
2014). During this extended mission it is surveying a 2012). DST and EXOTRANS have been applied
series of fields around the ecliptic; each campaign (ob- extensively to both CoRoT (Carpano et al. 2009;
servations of a specific field) has a duration of ∼75−80 Cabrera et al. 2009; Erikson et al. 2012; Carone et al.
days. K2hasalreadyproducedhundredsofplanetcandi- 2012; Cavarroc et al. 2012) and Kepler (Cabrera et al.
dates (Vanderburg et al. 2016), but, like any other tran- 2014, Grziwa et al. 2016, submitted) data. All tran-
sit survey, further observations are typically needed to sit detection algorithms search for a pattern in the data
confirm or validate planet candidates as bona fide plan- and use a statistic to decide if a signal is present in the
ets. Thisis particularlytrue forgiantplanetcandidates, data or not. When compared to widely used algorithms
as this population suffers from high false positive rates like Box Least Squares (BLS; Kov´acs et al. 2002), DST
(Fressin et al. 2013; Santerne et al. 2016). Conversely, uses an optimized transit shape, with the same number
however, giant planet candidates are the easiest popu- offreeparametersasBLS,andanoptimizedstatisticfor
lation to confirm with RV measurements of the stellar signaldetection. EXOTRANSusesa combinationofthe
reflex motion due to the large RV semi-amplitude varia- wavelet based filter technique VARLET (Grziwa et al.
tions induced by the planets. 2015) and BLS. VARLET was developed to reduce stel-
HerewepresentK2photometryfortwolate-typedwarf lar variability and discontinuities in light curves.
stars, EPIC 211089792 (K2-29) and EPIC 210957318 We identified periodic transit-like signals associated
(K2-30), for which we identified periodic transit signals, with two K2 Campaign 4 targets, EPIC 211089792
and our follow-up spectroscopic observations. These and EPIC 210957318; both signals were detected in
have allowed us to confirm both transiting objects as the lightcurves produced by all three methods, and us-
bona fide hot Jupiters, and to measure the stellar and ing both DST and EXOTRANS for transit detection.
planetary parameters. EPIC211089792wasselectedforK2observationsbypro-
gram GO4007 (P.I. Winn), while EPIC 210957318 was
2. K2PHOTOMETRY also proposed by program GO4007 as well as programs
ObservationsforK2Campaign4beganon2015Febru- GO4020 (P.I. Stello) and GO4060 (P.I. Coughlin). For
ary 7 UT and lasted until 2015 April 23 UT15; during brevity we will hereafter refer to these targets as K2-29
these observations the boresight of the Kepler space- and K2-30, respectively. K2-29 was located on module
craft was pointed at coordinates of α = 03h56m18s, δ = 4,channel10ofthe Kepler focalplane, while K2-30 was
+18◦39′38′′. A total of 15,847 long cadence (30 minute located on module 20, channel 71. Both targets passed
integration time) and 122 short cadence (1 minute inte- all of the tests that we used to identify likely false posi-
gration time) targets were observed. tives(includinglackofodd-eventransitdepthvariations,
We utilized two different methods to produce light absenceofadeepsecondaryeclipse,andlackoflargepho-
curves for all 15,969 targets from the K2 pixel data. tometric variations in phase with the candidate orbital
The first technique followed the methodology outlined period), and so we proceeded to more detailed fitting
in Grziwa et al. (2015). The K2 target pixel files were of the light curve as well as reconnaissance spectroscopy
analyzed for stellar targets and a mask for each tar- andthenRVobservations(see§3formoreontheselatter
get was calculated. After light curve extraction, dis- points). We also searched for additional transit signals
turbances produced by the drift of the telescope were in the lightcurves of these stars, but none were found.
corrected by calculating the rotation of the telescope’s The identifiers, magnitudes, colors, and proper motions
CCD. This drift is caused by the fact that the Kepler of these stars are listed in Table 1.
spacecraftis now operatingon only two reactionwheels, K2-29 has a nearby star that is 4” northeast of the
and is using the combination of carefully balanced solar targetand1.9±0.1magfainter,andwhosefluxcontam-
radiation pressure and periodic thruster firings for sta- inatesthemeasuredlightcurve. Giventhattheaperture-
bilization about the third axis; this results in a periodic mask that was used to extract the light curve is several
rotationofthe spacecraftaboutthe axisofthe telescope times wider than the star-contaminator separation (1.0
(Howell et al. 2014). In the second method, the photo- pixels in the Kepler plate scale), we estimated that the
metric time-series data extraction was based on circu- fraction of the PSF from both target and contamina-
lar apertures. For each target, we selected an optimal tor that was included in the aperture mask is the same
aperture size to minimize the noise in the light curve to within 20%. We therefore used the contaminator-to-
and estimated the background by calculating the me- target brightness ratio as an estimate of the fraction of
dian value of the stamp after excluding all bright pixels contaminating flux in the target light curve, obtaining
which might belong to potential sources. The resulting 15±4%,andcorrectedthelightcurveaccordingly. There
15 http://keplerscience.arc.nasa.gov/k2-fields.html 16 https://www.cfa.harvard.edu/avanderb/allk2c4obs.html
Two New Hot Jupiters 3
arenosourcescloseto K2-30 thatcouldcontaminateits In addition to measuring the RVs, we also used our
light curve. high-resolution spectra to derive stellar parameters for
In order to fit the K2 photometry and extract our target stars. We stacked all of our FIES spectra
the transit parameters, we used the EXOFAST package for each target, and then analyzed these data adopting
(Eastman et al. 2013) to simultaneously fit the K2 pho- two independent procedures. The first method used a
tometry as extracted by Vanderburg & Johnson (2014) gridoftheoreticalmodelsfromCastelli & Kurucz(2004),
and our radial velocity observations. We modified the Coelho et al. (2005), and Gustafsson et al. (2008) to fit
original code to account for RV data-sets from different spectral features that are sensitive to different photo-
spectrographs. Our results for K2-29b and K2-30b are spheric parameters. We adopted the calibration equa-
discussed in §4 and §5, respectively. tions from Bruntt et al. (2010) and Doyle et al. (2014)
to estimate the microturbulent (v ) and macroturbu-
mic
3. HIGH-RESOLUTIONSPECTROSCOPY lent(v )velocities. Wesimultaneouslyfittedthespec-
mac
We obtained high-resolution spectroscopic observa- tralprofilesofseveralcleanandunblendedmetallinesto
tions ofK2-29 andK2-30 usingthree differentfacilities. estimate the projected rotational velocity (vsini⋆).
WeusedtheRobertG.Tullcoud´espectrograph(TS23; The second method relied on the Spectroscopy Made
Tull et al. 1995) on the 2.7m HarlanJ. Smith Telescope Easy(SME)package(Valenti & Piskunov1996). Weused
at McDonald Observatory,Texas (USA), to obtain both ATLAS12 model grids for the derivation of the stellar
reconnaissance spectroscopy (for initial vetting of stel- parameters, and again estimated the micro- and macro-
lar parameters) and RV observations. TS23 is a cross- turbulentvelocitiesusingthesamemethodasabove. We
dispersedslit-fed´echellespectrographwithaspectralre- primarilyusedthe wings ofthe Balmerlines(mostly Hα
solving power of R = 60,000. It has spectral coverage and Hβ) to determine Teff, and the Mgi λ5167, λ5173,
from 3750 ˚A to 10200 ˚A, which is complete blueward of andλ5184˚A,theCaiλ6162andλ6439˚A,andtheNaiD
5691˚A.WeusedanI2cellfortheRVobservations. These (λ5890 and λ5896 ˚A) lines to estimate logg∗. In order
observations occurred between November 2015 and Jan- to verify the accuracy of this method, we analyzeda So-
uary 2016. lar spectrum from Wallace et al. (2011). Following the
We also obtained both reconnaissance spectroscopy discussion given in Barklem et al. (2002), we found the
andRVobservationswiththeFIbre-fedE´chelleSpectro- errorsquoted to be representative of what can currently
graph (FIES; Frandsen & Lindberg 1999; Telting et al. be achieved when calculating synthetic spectra in order
2014) on the 2.56m Nordic Optical Telescope at the to fit observations. Our final adopted values for Teff,
Observatorio del Roque de los Muchachos, La Palma logg⋆, [Fe/H], andvsini⋆ arethe weightedmeans of the
(Spain). The observations were carried out between values produced by the two methods.
November2015andJanuary2016,aspartofthe observ- Wederivedthestellarmassandradiususing EXOFAST,
ingprogramsOPTICON15B/064andCAT15B/035,us- utilizing our values for Teff, logg⋆ and [Fe/H], the
ingthehigh-res mode(R=67,000). Thissetupprovides transit-derived stellar mean density, and the relation-
spectral coverage from 3640 ˚A to 7360 ˚A. Following the ship between these parameters and M⋆, R⋆ found by
Torres et al. (2010). In order to measure the age and
same observing strategy as in Gandolfi et al. (2015), we
distance of our targets, we used the isochrones pack-
traced the RV drift of the instrument by acquiring long-
age (Morton 2015) to derive these parameters from our
exposed (T ∼35 seconds) ThAr spectra immediately
exp values of T , logg , and [Fe/H] plus the available stel-
before and after each observation. We removed cosmic eff ⋆
lar magnitudes (we used the value of logg derivedfrom
ray hits by combining 3 consecutive 1200 second sub- ⋆
globalmodeling of the system, including the stellar den-
exposures per observation epoch.
sity derived fromthe transitlight curve,rather than the
Finally, we obtained RV observations with the
value of logg derived purely from spectroscopy). We
HARPS-N spectrograph (R = 115,000, with wave- ⋆
note, however, that the isochrone age uncertainties we
length coverage from 3830 to 6900 ˚A; Cosentino et al.
report in Table 3 are formal, i.e., roughly proportional
2012)onthe3.58mTelescopioNazionaleGalileo,alsoat
to the 1σ errors of the stellar parameters used as input,
La Palma, between December 2015 and January 2016.
which do not include an estimate of systematic uncer-
These observationswere partof the same observingpro-
tainties. Thus, these isochrone age error bars could be
grams as on FIES. Two consecutive exposures of 1800
severely underestimated. For K2-29 we also used the
seconds were acquired per observation epoch but were
relationspresentedbyBarnes(2007)to calculatethe gy-
not combined.
rochronologicalage of the star, as described in the next
We collected seven RV observations of K2-29 with
section.
TS23, seven with FIES, and four with HARPS-N. For
K2-30, we obtained four RVs each with FIES and
4. K2-29b
HARPS-N. At V = 13.53 mag, this star is too faint for
TS23 iodine-cell RVs. All of our RVs, along with the bi- The full andphase-foldedlightcurvesand the RVs for
sector span measurements of the cross-correlation func- K2-29 are shown in Fig. 1 (clear outliers have been re-
tion(CCF)andthe signal-to-noiseratio(SNR)perpixel moved by visual inspection of the lightcurve). We used
at 5500 ˚A, are listed in Table 2. We did not calculate all21transitsobservedbyK2duringCampaign4 to ob-
CCFbisectorspansfortheTS23dataduetothepresence tain the best-fit parameters for the system. The param-
ofthe iodine lines inthe spectra. The RVmeasurements eters that we have measured and calculated for K2-29
show no significant correlation with the CCF bisector and K2-29b are listed in Table 3.
spans, indicating that the observed Doppler shifts are K2-29b is a sub-Jupiter-mass (0.613+−00..002276MJ),
induced by the orbital motion of the companions. Jupiter-radius (1.000+0.071R ) planet orbiting a solar-
−0.067 J
4 Johnson et al.
Table 1
StellarIdentifiers, Magnitudes,andColors
Parameter K2-29 K2-30 Source
Identifiers
EPIC 211089792 210957318 EPIC
TYC 1818-1428-1 ... EPIC
UCAC 573-010529 562-007074 EPIC
2MASS 04104086+2424061 03292204+2217577 EPIC
WISE J041040.88+242405.9 J032922.08+221757.7 AllWISE
α(J2000.0) 04h10m40s.955 03h29m22.071s EPIC
δ (J2000.0) +24◦24′07′′.35 +22◦17′57′′.86 EPIC
Magnitudes
B 13.16±0.36 14.506±0.030 EPIC
V 12.56±0.26 13.530±0.040 EPIC
g 12.928±0.020 13.979±0.034 EPIC
r 11.918±0.040 13.189±0.040 EPIC
i 12.908±0.900 12.825±0.050 EPIC
Kp 12.914 13.171 EPIC
J 10.622±0.035 11.632±0.019 2MASS
H 10.168±0.041a 11.190±0.016 2MASS
K 10.062±0.034a 11.088±0.020 2MASS
W1 10.095±0.037 11.016±0.023 AllWISE
W2 10.142±0.037 11.058±0.021 AllWISE
W3 9.991±0.082 11.067±0.161 AllWISE
W4 >7.549 >9.003 AllWISE
Colors
B−V 0.60±0.44b 0.976±0.050 calculated
J−K 0.560±0.049 0.544±0.028 calculated
Proper Motions
µαcosδ (masyr−1) 10.8±5.3 25.9±2.3 UCAC4
µδ (masyr−1) −29.6±5.9 −13.6±2.4 UCAC4
Note. — Stellar identifiers, magnitudes, and colors. Values of fields
marked EPIC were taken from the Ecliptic Plane Input Catalog, available
at http://archive.stsci.edu/k2/epic/search.php. Values marked 2MASS are from
Skrutskieetal. (2006), those markedAllWISEarefrom Cutrietal. (2014), and those
markedUCAC4fromZachariasetal.(2013).
a The 2MASS catalog notesthat the H- and K-band magnitudesfor K2-29 are “low
qualityresults(upperlimitsorverypoorphotometry).”
b TheB−V colorthatwecalculatedforK2-29 ismuchbluerthanexpectedforaK1V
star;however,duetothepoor-qualityBandV photometryfromEPICtheuncertainties
onthecolorareverylarge. Asnotedinthetext,theisochronescodepredictsacolor
ofB−V =0.890+−00..002265 (whichisstillconsistenttowithin1σwiththatcalculatedfrom
thephotometry).
metallicity ([Fe/H] = 0.00±0.05) K1V star. It is per- caused by active regions at opposite longitudes of the
haps most notable for its slightly eccentric orbit (e = star.
0.084+0.032); its eccentricity is larger than that of most
−0.023
knownhot Jupiters with similar orbitalsemi-majoraxes 4.1. Stellar Age
(Fig. 2). We also fit a model with the eccentricity fixed
Our values of the stellar age inferred from the
to zero; we stress that imposing a circular orbit had a
isochrones (2.6+2.5 Gyr) and gyrochronology (367±45
negligible effect (within 1σ) on the values of the other −1.1
Myr) are discrepant with each other. We used a stellar
planetary parameters.
As can be seen from the K2 light curve (top panel of colorof B−V =0.890+−00..002265 derivedfromisochronesus-
Fig 1), K2-29 exhibits significant rotational variability. ingonly ourspectroscopically-derivedstellar parameters
The trough-to-peak amplitude is ∼ 1−2%. The over- in order to calculate an age using the gyrochronological
allshape ofthe lightcurvechangessignificantlyoverthe relation of Barnes (2007); we used this rather than the
courseof the K2 observations,indicating the presenceof photometricvalueofB−V =0.60±0.44duetothelatter
spot evolutionand/or differentialrotation. We analyzed value’sinconsistencywiththespectraltypeofK2-29 and
therotationalvariabilityusingtheauto-correlationfunc- its large uncertainty. Discrepancies between stellar ages
tion (ACF) of the light curve (see e.g., McQuillan et al. inferred from isochrones and gyrochronology, however,
2013). Using this methodology, we found a rotation pe- arecommonforhotJupiterhoststars;thesestarstendto
riodofP =10.777±0.031days. Periodogramanalysis rotate more quickly than expected given their isochrone
rot
of the light curve gives a broadly consistent rotation pe- ages and thus appear younger gyrochronologically (e.g.,
riod, although it also contains significant power at the Pont 2009; Maxted et al. 2015). This is thought to be
first harmonic near 5.4 days. The ACF also displays a due to interactions between the planet and the star–
secondary correlation peak at ∼5.4 days that is likely either through tidal spin-up of the star, or through the
planet altering the star’s magnetic field structure and
Two New Hot Jupiters 5
Table 2
RadialVelocityandActivityMeasurements
BJDTDB−2450000 RV(kms−1) σRV (kms−1) BS(kms−1)a Phase SNRb Instrument
K2-29
7339.88236 28.1533 0.0258 ... 0.52 31 TS23
7343.60425 32.7989 0.0119 −0.0050 0.66 33 FIES
7345.54925 32.6233 0.0290 −0.0091 0.26 13 FIES
7347.67108 32.7908 0.0214 −0.0066 0.91 22 FIES
7371.41031 32.9069 0.0122 0.0230 0.20 14 HARPS-N
7371.43422 32.8797 0.0115 0.0389 0.20 14 HARPS-N
7373.68822 28.2024 0.0455 ... 0.90 18 TS23
7374.59449 28.0655 0.0389 ... 0.17 20 TS23
7375.60615 28.1338 0.0310 ... 0.48 24 TS23
7375.91120 28.1926 0.0384 ... 0.58 22 TS23
7392.44628 32.7970 0.0121 0.0155 0.65 32 FIES
7394.52107 32.6462 0.0121 0.0233 0.29 32 FIES
7395.55871 32.7770 0.0123 0.0062 0.61 31 FIES
7399.34590 33.0677 0.0080 0.0094 0.77 19 HARPS-N
7399.36609 33.0736 0.0071 0.0187 0.77 20 HARPS-N
7400.64452 28.1062 0.0348 ... 0.17 20 TS23
7402.66084 28.3081 0.0411 ... 0.79 20 TS23
7418.36906 32.7771 0.0240 0.0481 0.61 19 FIES
K2-30
7343.46426 35.3591 0.0116 −0.0052 0.23 27 FIES
7345.65414 35.5187 0.0651 −0.0702 0.77 5 FIES
7370.63631 35.7079 0.0148 −0.0280 0.86 10 HARPS-N
7372.47940 35.5156 0.0296 −0.0521 0.31 6 HARPS-N
7394.46817 35.4922 0.0194 −0.0275 0.68 21 FIES
7395.41003 35.4697 0.0153 −0.0107 0.91 24 FIES
7399.43817 35.6695 0.0090 −0.0356 0.89 15 HARPS-N
7399.45999 35.6698 0.0094 −0.0222 0.90 14 HARPS-N
Note. —RadialvelocitiesandCCFbisectorspanmeasurementsforourspectroscopicobservations. The
TS23RVsaredifferential,notabsolute,resultinginaverydifferentvalueoftheRV.TheRVoffsetbetween
theTS23andFIESdatais∆RVTS23−FIES=−4.5646±0.0031kms−1.
a For the CCF bisector spans we assumed an uncertainty twice that of the RV from the corresponding
spectrum. WedidnotcalculatebisectorspansfortheTS23dataduetothepresenceofiodinelinesinthe
spectra.
b Signal-to-noiseratioperpixel,measuredat5500˚A.
thus reducing spin-down(Ferraz-Mello et al. 2015). The Sestito & Randich(2005)showgreaterdepletion,andfor
latter mechanism, however, is thought to be most ef- theclustersmostsimilarin[Fe/H] toK2-29 wewouldbe
ficient for F-type stars (Lanza 2010). We therefore able to detect the expected A(Li) level. K2-29 therefore
adopted the isochrone age. likelyhasanageof>600Myr,whichwouldruleoutthe
Despite the relatively old isochrone age, K2-29 main- gyrochronologicalvalue of 367±45 Myr.
tains sufficient spot coverageto result in rotationalvari- WealsosoughttodeterminewhetherK2-29 couldbea
ability at a level of ∼1−2%. We also detected chromo- memberofeitherofthe youngopenclustersinthe Cam-
spheric emission in the cores of the Ca ii H and K lines; paign4 field of view, the Hyadesand Pleiades. We com-
the spectra are too noisy at these wavelengths to obtain puted the space velocities of the star using the gal uvw
a quantitative measurement of the emission level, how- IDL routine17, finding U = −30.9 km s−1, V = −18.0
ever. The presenceof significantstellaractivity suggests km s−1, and W = −20.4 km s−1. Using Eqn. 2 of
that either the star is relatively young (ages as young as Klutsch et al. (2014) and the cluster UVW values pre-
1.5Gyrarestillwithin1σ oftheisochroneage,usingthe sentedinthatwork,weestimatedthatK2-29 hasa10%
formal uncertainties), or that tidal spin-up has allowed probability of being a member of the Hyades Superclus-
it to remain active despite its age. ter, but only a 0.01% probability of belonging to the
InordertofurtherconstraintheagewesearchedforLi Pleiades Moving Group. Our calculated metallicity for
absorption, which is an indicator of youth; GKM stars’ K2-29, [Fe/H] = 0.00±0.05, is also lower than that of
primordialLiabundancesaretypicallydestroyedoverthe the Hyades, which has [Fe/H] ∼ 0.15 (Perrymanet al.
firstfewhundredMyroftheirlives(seee.g. thereviewof 1998). We thus conclude that K2-29 is unlikely to have
Soderblom et al.2014). WedidnotdetectanyLiabsorp- originated as part of either the Pleiades or the Hyades.
tion,andsetaconservativeupper limitofA(Li)<1.3by
fitting synthetic spectra to our stacked FIES spectrum. 4.2. Tidal Evolution
Our stacked HARPS-N spectrum is also consistent with
Inordertoquantitativelyassesstheimplicationsofthe
thislimit. UsingtheresultsofSestito & Randich(2005),
eccentricplanetaryorbitandthetidalspin-upofthehost
who measuredLiabundancesinyoungopen clusters,we
star for the past evolution of the system, we calculated
can easily rule out ages of < 250 Myr for K2-29. Fur-
the tidal timescales of the system using the model of
thermore, we can likely rule out ages as great as ∼ 600
Myr; the more metal-rich clusters at this age studied by
17 http://idlastro.gsfc.nasa.gov/ftp/pro/astro/gal uvw.pro
6 Johnson et al.
Leconte et al. (2010). We assumed values for the tidal measurementofanRVtrend,orhigh-resolutionimaging
quality factors Q′ of the star and planet of 106 and 105, to find a distant stellar companion which could induce
respectively,andused ourother measuredparametersof Kozai-Lidov oscillations. Measurement of the spin-orbit
the system. We found that the semi-major axis tidal misalignment of K2-29b would also be useful on this
interaction timescale is [(da/dt)/a]−1 = 1.77 Gyr, and front; a misaligned orbit would point towards migration
the eccentricity timescale is [(de/dt)/e]−1 =0.027 Gyr. through either planet-planet scattering or Kozai-Lidov.
These results indicate that the planet is indeed do- Our measured rotational period and calculated stel-
nating angular momentum to the star, and as a result lar radius predict an equatorial rotational velocity of
its semi-major axis is shrinking. The timescale for the veq = 3.51±0.22 km s−1. This deviates from the value
star’s rotational evolution with these tides, however, is of vsini⋆ = 3.8± 0.1 km s−1 that we measured from
∼60−70Gyr,indicatingthatthe planetcouldnothave our spectra by only ∼ 1.2σ, suggesting that the star is
spun up the star through tides alone. The star’s fast viewed close to equator-on. This also suggests that the
spin must therefore have been caused by another mech- spin-orbit misalignment might be small, although large
anism, for instance suppressed magnetic braking or the spin-orbit misalignments can exist even for stars with
ingestion of another planetary body. i⋆ ∼ 90◦. Only direct measurement of the spin-orbit
A value of the eccentricity tidal interaction timescale misalignment can solve this issue.
of0.027Gyr is muchshorterthan the ageof the system,
whichhasconsequencesforitspastevolution. Ingeneral, 5. K2-30b
eccentricorbitsofhotJupitersmightbegeneratedintwo The full andphase-foldedlightcurvesand the RVs for
different manners: either the eccentricity is primordial, K2-30 are shown in Fig. 3. A total of 16 transits were
a relic of high-eccentricity migration that emplaced the observed by K2 during Campaign 4. We removed clear
planetonashort-periodorbit,ortheeccentricityisbeing outliersbyvisualinspectionandexcludedthe10thtransit
excited by an external perturber. The short tidal eccen- from our analysis because of photometric discontinuities
tricity timescale suggests three possibilities for K2-29b: occurringimmediatelybeforeandduringthetransit. We
1)itmigratedrecentlyviahigh-eccentricitymigration;2) list the parameters for the star and planet in Table 3.
its eccentricityis currentlybeing excitedby aperturber; K2-30b is a 0.579+0.028M planet with an orbital pe-
or 3) we have underestimated the tidal quality factor of riod of 4.098503 ± 0−.00.00207011J days. It has a radius of
the planetand/orstar,resultinginamuchlongereccen- 1.039+0.050R . We do not have sufficient RV data to
tricitytimescale,inwhichcasetheplanetcouldhavemi- −0.051 J
constrain the planet’s eccentricity, and so we fixed it to
grated via high-eccentricity migration when the system
zero in our fits.
was much younger. For instance, a value of Q′ = 107
P The star has a slightly sub-solar metal content
wouldresultinaneccentricitytimescaleof2.24Gyr,con-
([Fe/H]=−0.15±0.05). Ametallicitythislowisunusual
sistent with the system age. All of these scenarios are
for a hot Jupiter host, though by no means unprece-
testable with further data.
dented; there are currently hot Jupiters known around
IftheorbitaleccentricityofK2-29b isbeingexcitedby
starswith metallicities as low as [Fe/H]=−0.6 (WASP-
an external perturber, the presence of such a perturber
98; Hellier et al. 2014).
could be detected through long-term radial velocity ob-
Using isochrones, we found an age of 3.9+2.1 Gyr for
servations, or through transit timing variations (TTVs). −1.9
K2-30. No significant rotational modulation is evident
AsonlylongcadenceK2dataareavailableforK2-29,and
in the K2 light curve (top panel of Fig. 3), and so we
the ∼ 80 days of K2 observations are insufficient to be
could not measure the rotation period and calculate the
sensitivetoTTVsduetoamuchlonger-periodperturber,
gyrochronological age for this star as we did for K2-29.
we do not pursue this line of investigation. Future high-
We also calculated the space velocity of K2-30, finding
cadence transit observations could, however, be used to U = −43.9 km s−1, V = −27.0 km s−1, and W = −9.3
search for TTVs. km s−1. Again using the methodology of Klutsch et al.
High-eccentricity migration mechanisms include
(2014), we find that K2-30’s kinematics give it a 7%
planet-planet scattering (e.g., Rasio & Ford 1996;
membershipprobabilityinthe HyadesSupercluster,and
Chatterjee et al. 2008), the Kozai-Lidov mechanism an 8 × 10−8% membership probability in the Pleiades
(e.g.,Fabrycky & Tremaine2007;Naoz et al.2012),and
Moving Group. As is also the case for K2-29, K2-30’s
coplanar high-eccentricity migration (Petrovich 2015b).
low metallicity is inconsistent with the bulk metallicity
Planet-planet scattering and coplanar high-eccentricity
oftheHyades,andsoweconcludethatK2-30 isalsoun-
migration are both expected to take place during the
likely to have formed as part of either of these clusters.
first tens to hundreds of Myr of a system’s lifetime,
whereas Kozai-Lidov cycles can cause migration result-
6. CONCLUSIONS
ing in the emplacement of hot Jupiters on short-period
orbits even Gyrs after the system formed (Petrovich We have identified two hot Jupiter candidates in data
2015a). If K2-29b migrated recently, then it likely from K2 Campaign 4, and confirmed the planetary na-
did so via the Kozai-Lidov mechanism, but if the tidal ture of these objects, K2-29b and K2-30b, by using ra-
quality factor is higher than expected and it migrated dial velocity observations to detect the reflex motion of
early in the system’s history, it could have done so via their host stars. K2-29b was discovered independently
any of these mechanisms. Further observations could bySanterne et al.(2016);theyadditionallygaveitasec-
help to distinguish between these mechanisms. All three ond name, WASP-152b, as they also detected it in Su-
mechanisms require the presence of an additional object perWASP data. K2-30b was discovered independently
in the system, which could be detected either through by both Lillo-Box et al. (2016) and Brahm et al. (2016).
All of these works found stellar and planetary param-
Two New Hot Jupiters 7
Table 3
StellarandPlanetaryParameters
Parameter Explanation K2-29 K2-30 Source
Measured stellar parameters
SpT spectral typea K1V G6V spectroscopy
Teff effective temperature(K) 5222±40 5425±40 spectroscopy
logg∗ surfacegravity(cgs)b 4.54±0.07 4.53±0.07 spectroscopy
[Fe/H] metallicity 0.00±0.05 −0.15±0.05 spectroscopy
vmic microturbulentvelocityc (kms−1) 0.85±0.09 0.91±0.09 spectroscopy
vmac macroturbulentvelocityc (kms−1) 2.33±0.52 2.46±0.53 spectroscopy
vsini⋆ projectedrotational velocity(kms−1) 3.8±0.1 1.4±0.3 spectroscopy
γFIES systemicRV(kms−1) 32.7319±0.0029 35.4314±0.0021 spectroscopy
γHARPS systemicRV(kms−1) 32.9736±0.0034 35.6238±0.0031 spectroscopy
∆RVTS23−FIES TS23−FIESRVoffsetc (kms−1) −4.5686±0.0031 ... spectroscopy
Prot rotationperiod(days) 10.777±0.031 ... photometry
u1 linearlimbdarkeningcoeff.e 0.484+−00..003480 0.451±0.044 photometry
u2 quadraticlimbdarkeningcoeff.e 0.173+−00..005409 0.231+−00..004498 photometry
ρ⋆ density(gcm−3) 2.90+−00..5414 2.11+−00..2129 photometry
Derivedstellar parameters
M⋆ mass(M⊙) 0.864+−00..004319 0.900+−00..004432 spectroscopy+ρ⋆+T10f
R⋆ radius(R⊙) 0.748+−00..004452 0.844±0.032 spectroscopy+ρ⋆+T10f
L⋆ luminosity(L⊙) 0.374+−00..005403 0.554+−00..004486 spectroscopy+ρ⋆+T10f
logg∗ surfacegravity(cgs)g 4.626+−00..004467 4.540+−00..002297 spectroscopy+ρ⋆+T10f
age age(Gyr)h 2.6+2.5 3.9+2.1 isochrones
−1.1 −1.9
d distance(pc) 167.1+3.8 278.0±7.6 isochrones
−4.0
Measured planetary parameters
Porb orbitalperiod(days) 3.2589263±0.0000015 4.098503±0.000011 photometry
T0 transitepoch(BJDTDB−2450000) 7383.80546±0.00013 7063.80714±0.00010 photometry
τ14 transitduration(days) 0.08875±0.00100 0.09670±0.00100 photometry
τ12=τ34 ingress/egressduration(days) 0.0126±0.0015 0.0181+−00..00001165 photometry
a/R⋆ scaledsemi-majoraxis 11.77+−00..6652 12.34+−00..4328 photometry
Rp/R⋆ radiusratio 0.1373+−00..00002246 0.1266+−00..00001156 photometry
δ transitdepth(%) 1.884+0.066 1.603+0.037 photometry
−0.070 −0.041
b impactparameter 0.452+0.096 0.662+0.030 photometry
−0.15 −0.036
ip orbitalinclination(◦) 87.89+−00..7555 86.92+−00..2264 photometry
K RVsemi-amplitude(ms−1) 93.0±2.9 78.7+2.9 radialvelocities
−2.8
e orbitaleccentricity 0.084+0.032 0(fixed) radialvelocities
−0.023
ω argumentofperiastron(◦) 41+23 ... radialvelocities
−34
esinω 0.052+0.047 ... radialvelocities
−0.044
ecosω 0.058+0.019 ... radialvelocities
−0.021
Tperi epochofperiastron(BJDTDB−2450000) 7383.43+−00..1390 ... radialvelocities
Derivedplanetary parameters
MP mass(MJ) 0.613+−00..002276 0.579+−00..002287 calculated
RP radius(RJ) 1.000+−00..007617 1.039+−00..005501 calculated
ρP density(gcm−3) 0.76+−00..1174 0.640+−00..009880 calculated
loggP surfacegravity(cgs) 3.181+−00..005598 3.123+−00..004420 calculated
a semi-majoraxis(AU) 0.04097±0.00064 0.04839±0.00076 calculated
Teq equilibriumtemperature(K) 1076+−3310 1092+−1290 calculated
Note. —Stellarandplanetaryparametersforourtargets.
a Basedonthespectraltypevs. effectivetemperaturecalibrationofStraizys&Kuriliene(1981).
b logg⋆ asmeasuredfromstellarspectra.
c MicroandmacroturbulentvelocityarederivedusingthecalibrationequationfromBrunttetal.(2010)andDoyleetal.(2014),respectively.
d TS23producesiodinecellRVs,whicharedifferentialRVs,notabsolutelikethoseproducedbyFIESandHARPS-N.ThisistheRVoffsetneeded
tobringtheTS23dataintothesameframeastheFIESdata,whichisnotthesameframeastheHARPS-Ndata. Thequotedγ valuescanthen
beusedtobringallthreedatasetsintothesameframe.
e LimbdarkeningcoefficientsaremeasuredintheKeplerbandpass.
f T10referstotherelationsamongTeff,logg∗,[Fe/H],M⋆,andR⋆ foundbyTorresetal.(2010).
g logg⋆ asderivedfromglobalmodelingofthesystem.
h Theuncertaintiesontheseisochroneagesarederivedsolelyfromtheformaluncertaintiesonthestellarparametersanddonottakesystematic
uncertaintiesintoaccount. Theuncertaintiesintheagesmaythusbeseverelyunderestimated.
8 Johnson et al.
1.03
1.02
1.01
x
u
d fl 1.00
e
z
mali0.99
r
o
n0.98
0.97
0.96
7070 7080 7090 7100 7110 7120 7130
BJD-2450000
1.005
1.000
0.995
x
u
d fl
e
aliz0.990
m
or
n0.985
0.980
0.975
−0.03 −0.02 −0.01 0.00 0.01 0.02 0.03 0.04
phase
Figure 1. Top: light curve for K2-29, produced using the pipeline of Vanderburg&Johnson (2014). Times of transits are marked by
verticalredbars. Notethelargevariabilityduetothestellarrotation. Bottomleft: phase-foldedlightcurveforK2-29. Thebest-fitmodelis
overplottedinred. Theclusteringinthephase-foldeddataisduetothefactthattheplanetaryorbitalperiod(3.2589265±0.0000015days)
isverycloseto156Kepler30minutelongcadenceperiods(3.25days). Boththefullandphase-foldedlightcurveshavebeencorrectedfor
thecontaminatingfluxofthenearbysource,asdescribedinthetext. Bottomright: phase-foldedRVsforK2-29,followingthesubtraction
ofthe systemicvelocity andFIES-TS23RV offsetlistedinTable3. HARPS-Ndataareshownwithredsquares,FIESwithgreencircles,
andMcDonaldwithbluetriangles.
Two New Hot Jupiters 9
chos (ORM) of the Instituto de Astrofisica de Canarias
0.6 (IAC); b) with the Italian Telescopio Nazionale Galileo
(TNG) also operated at the ORM (IAC) on the island
0.5 of La Palma by the INAF - Fundacion Galileo Galilei.
The research leading to these results has received fund-
0.4 ing from the European Union Seventh Framework Pro-
gramme (FP7/2013-2016) under grant agreement No.
e0.3 312430(OPTICON) and from the NASA K2 Guest Ob-
server Cycle 1 program under grant NNX15AV58G to
0.2 The University of Texas at Austin. This research has
made use of the Exoplanet Orbit Database and the Ex-
0.1 oplanet Data Explorer at exoplanets.org. This publica-
tionmakesuseofdataproductsfromtheTwoMicronAll
0.00.01 0.02 0.03 0.04 0.05 0.06 0.07 0.08 0.09 0.10 Sky Survey, which is a joint project of the University of
a (AU) Massachusettsand the InfraredProcessingand Analysis
Figure 2. DistributionofeversusaforknownhotJupiters(P < Center/CaliforniaInstituteofTechnology,fundedbythe
10 days, 0.3MJ < MP < 13MJ). K2-29b is marked in blue and NationalAeronauticsandSpace Administrationandthe
K2-30b in red. Note that due to its circular orbit, K2-30b is
National Science Foundation. This publication makes
shown at the bottom of the plot. The literature data are taken
from the Exoplanets Orbit Database (Hanetal. 2014) as of 2016 use of data products from the Wide-field Infrared Sur-
Jan. 8. vey Explorer, which is a joint project of the University
ofCalifornia,LosAngeles,andthe JetPropulsionLabo-
eters which are broadly consistent with ours. Coinci-
ratory/CaliforniaInstitute of Technology,funded by the
dentally, the physicalparameters of the planets are very
National Aeronautics and Space Administration.
similar to each other; their masses, radii, and equilib-
riumtemperatures(assumingperfectheatredistribution
and an albedo of zero) are identical to within 1σ. Both REFERENCES
planets have radii typical for their masses and equilib-
rium temperatures. K2-29b orbits a V = 12.56 mag Barklem,P.S.,Stempels,H.C.,AllendePrieto,C.,etal.2002,
star, whereas K2-30b orbits a relatively faint star with A&A,385,951
V = 13.53 mag. Although neither is among the bright- Barnes,S.A.2007,ApJ,669,1167
Batygin,K.,Bodenheimer,P.H.,&Laughlin,G.P.2015,
est stars to host transiting exoplanets, these stars are
arXiv:1511.09157
nonetheless bright enough to be amenable to ground-
Becker,J.C.,Vanderburg,A.,Adams,F.C.,Rappaport,S.A.,&
based transit observations. We encourage such obser- Schwengeler, H.M.2015,ApJ,812,L18
vations, particularly for K2-29, where the higher spatial Borucki,W.J.,Koch,D.,Basri,G.,etal.2010,Science,327,977
resolution of ground-based photometry can easily sepa- Brahm,R.,Jones,M.,Espinoza,N.,etal.2016, arXiv:1603.01721
Bruntt,H.,Bedding,T.R.,Quirion,P.-O.,etal.2010,MNRAS,
rate K2-29 from the nearby contaminating source and
405,1907
thereby eliminate the uncertainties caused by the con- Cabrera,J.,Csizmadia,S.,Erikson,A.,Rauer,H.,&Kirste,S.
tamination in the K2 lightcurve. 2012,A&A,548,A44
Somewhat unusually, the orbit of K2-29b is slightly Cabrera,J.,Csizmadia,S.,Lehmann,H.,etal.2014,ApJ,781,18
eccentric(e=0.084+0.032),whileK2-30 isslightlymetal- Cabrera,J.,Fridlund,M.,Ollivier,M.,etal.2009,A&A,506,501
−0.023 Carone,L.,Gandolfi,D.,Cabrera,J.,etal.2012,A&A,538,A112
poor ([Fe/H] = −0.15±0.05). The relatively short ro- Carpano,S.,Cabrera,J.,Alonso,R.,etal.2009,A&A,506,491
tation period (10.777±0.031 days), high-amplitude ro- Castelli,F.&Kurucz,R.L.2004,eprintarXiv:astro-ph/0405087
tational variability (∼1-2%), and presence of chromo- Cavarroc,C.,Moutou,C.,Gandolfi,D.,etal.2012,Ap&SS,337,
spheric Ca ii H & K emission suggest that K2-29 may 511
Chatterjee,S.,Ford,E.B.,Matsumura,S.,&Rasio,F.A.2008,
be relatively young, though the lack of detectable Lii
ApJ,686,580
λ6708˚Aabsorptionline indicates thatit is not asyoung Coelho,P.,Barbuy,B.,Mel´endez,J.,etal.2005,A&A,443,735
as the ∼ 360 Myr value indicated by gyrochronology. Cosentino,R.,Lovis,C.,Pepe, F.,etal.2012,Proc.SPIE,8446,
84461V
Additionally,theeccentricorbitofK2-29b suggeststhat
Coughlin,J.L.,Mullally,F.,Thompson,S.E.,etal.2015,
either K2-29b migratedto its currentlocation via high-
arXiv:1512.06149
eccentricity migration, or that there is an additional Cutri,R.M.,&etal.2014,VizieROnlineDataCatalog,2328,
planet in the system exciting the eccentricity. These Dawson,R.I.,&Murray-Clay,R.A.2013,ApJ,767,L24
possibilities could be distinguished using long-term RV Doyle,A.P.,Davies,G.R.,Smalley,B.,etal.2014,MNRAS,444,
3592
and/or TTV monitoring to detect an additional com-
Eastman,J.,Gaudi,B.S.,&Agol,E.2013,PASP,125,83
panion.
Erikson,A.,Santerne, A.,Renner,S.,etal.2012, A&A,539,A14
Fabrycky,D.,&Tremaine,S.2007,ApJ,669,1298
We thank Nuccio Lanza for assisting with the calcula- Ferraz-Mello,S.,TadeudosSantos, M.,Folonier,H.,etal.2015,
ApJ,807,78
tion of the tidal timescales for K2-29b, and Avi Shporer
Frandsen,S.&Lindberg,B.1999,in“Astrophysicswiththe
for useful discussions.
NOT”,proceedings Eds:Karttunen, H.&Piirola,V.,anot.
This paper includes data taken at The McDonald Ob- conf,71
servatoryofTheUniversityofTexasatAustin. Basedon Fressin,F.,Torres,G.,Charbonneau,D.,etal.2013,ApJ,766,81
observations obtained a) with the Nordic Optical Tele- Gandolfi,D.,Parvianinen,H.,Deeg,H.J.,etal.2015, A&A,576,
A11
scope(NOT),operatedontheislandofLaPalmajointly
Grziwa,S.,P¨atzold,M.,&Carone,L.2012,MNRAS,420,1045
by Denmark, Finland, Iceland, Norway, and Sweden,
Grziwa,S.,Gandolfi,D.,Csizmadia,S.,etal.2015,
in the Spanish Observatorio del Roque de los Mucha- arXiv:1510.09149
10 Johnson et al.
1.010
1.005
1.000
x
u
d fl0.995
e
z
mali0.990
r
o
n0.985
0.980
0.975
7070 7080 7090 7100 7110 7120 7130
BJD-2450000
1.005
1.000
x
d flu0.995
e
aliz
m
or0.990
n
0.985
0.980
−0.03 −0.02 −0.01 0.00 0.01 0.02 0.03
phase
Figure 3. Top: light curve for K2-30, produced using the pipeline of Vanderburg&Johnson (2014). Times of transits are marked by
verticalredbars. Severaldiscontinuitiesinthelightcurveduetoinstrumentalsystematicsarevisible. Bottomleft: phase-foldedlightcurve
forK2-30. Thebest-fitmodelisoverplotted inred. Weexcludedthedatafromthe10th transitfromthisfigure(andfromthefit)dueto
highnoiseand systematics. Bottom right: phase-foldedRVsforK2-30, followingthesubtraction ofthe systemicvelocityandFIES-TS23
RVoffsetlistedinTable3. HARPS-NdataareshownwithredsquaresandFIESwithgreencircles.
Gustafsson,B.,Edvardsson,B.,Eriksson,K.,etal.2008,A&A, Petrovich,C.2015a,ApJ,799,27
486,951 Petrovich,C.2015b,ApJ,805,75
Han,E.,Wang, S.X.,Wright,J.T.,etal.2014,PASP,126,827 Pont,F.2009,MNRAS,396,1789
Hellier,C.,Anderson,D.R.,Cameron,A.C.,etal.2014, Rasio,F.A.,&Ford,E.B.1996, Science,274,954
MNRAS,440,1982 Rowe,J.F.,Bryson,S.T.,Marcy,G.W.,etal.2014,ApJ,784,
Howell,S.B.,Sobeck, C.,Haas,M.,etal.2014, PASP,126,398 45
Huang,C.X.,Wu,Y.,&Triaud,A.H.M.J.2016, Santerne,A.,H´ebrard,G.,Lillo-Box,J.,etal.2016,
arXiv:1601.05095 arXiv:1601.07680
Jontof-Hutter,D.,Rowe,J.F.,Lissauer,J.J.,Fabrycky,D.C.,& Santerne,A.,Moutou,C.,Tsantaki,M.,etal.2016,A&A,587,
Ford,E.B.2015,Nature,522,321 A64
Klutsch,A.,FreireFerrero,R.,Guillout,P.,etal.2014,A&A, Sestito,P.,&Randich,S.2005, A&A,442,615
567,A52 Skrutskie,M.F.,Cutri,R.M.,Stiening,R.,etal.2006,AJ,131,
Kova´cs,G.,Zucker,S.,&Mazeh,T.2002, A&A,391,369 1163
Lanza,A.F.2010, A&A,512,A77 Soderblom,D.R.,Hillenbrand,L.A.,Jeffries,R.D.,Mamajek,
Leconte, J.,Chabrier,G.,Baraffe,I.,&Levrard,B.2010,A&A, E.E.,&Naylor,T.2014, ProtostarsandPlanetsVI,219
516,A64 Straizys,V.&Kuriliene,G.1981, Ap&SS,80,353
Lillo-Box,J.,Demangeon, O.,Santerne,A.,etal.2016, Telting,J.H.,Avila,G.,Buchhave,L.,etal.2014,Astronomische
arXiv:1601.07635 Nachrichten, 335,41
Lin,D.N.C.,Bodenheimer,P.,&Richardson,D.C.1996, Torres,G.,Andersen,J.,&Gim´enez, A.2010,A&ARev.,18,67
Nature,380,606 Tull,R.G.,MacQueen,P.J.,Sneden,C.,&Lambert,D.L.1995,
Maxted,P.F.L.,Serenelli,A.M.,&Southworth, J.2015, A&A, PASP,107,251
577,A90 Valenti,J.A.,&Piskunov,N.1996, A&AS,118,595
Mayor,M.,&Queloz,D.1995,Nature,378,355 Vanderburg,A.,&Johnson, J.A.2014,PASP,126,948
McQuillan,A.,Aigrain,S.,&Mazeh,T.2013,MNRAS,432,1203 Vanderburg,A.,Latham,D.W.,Buchhave, L.A.,etal.2016,
Morton,T.D.2015, AstrophysicsSourceCodeLibrary, ApJS,222,14
ascl:1503.010 Wallace,L.,Hinkle,K.H.,Livingston,W.C.,&Davis,S.P.
Naoz,S.,Farr,W.M.,&Rasio,F.A.2012,ApJ,754,L36 2011,ApJS,195,6
Perryman,M.A.C.,Brown,A.G.A.,Lebreton, Y.,etal.1998, Wright,D.J.,Wittenmyer,R.A.,Tinney,C.G.,Bentley,J.S.,&
A&A,331,81 Zhao,J.2016,ApJ,817,L20