J/ApJS/226/7 Planet candidates discovered using K2's 1st yr (Crossfield+, 2016)
197 candidates and 104 validated planets in K2's first five fields.
Crossfield I.J.M., Ciardi D.R., Petigura E.A., Sinukoff E., Schlieder J.E.,
Howard A.W., Beichman C.A., Isaacson H., Dressing C.D., Christiansen J.L.,
Fulton B.J., Lepine S., Weiss L., Hirsch L., Livingston J., Baranec C.,
Law N.M., Riddle R., Ziegler C., Howell S.B., Horch E., Everett M.,
Teske J., Martinez A.O., Obermeier C., Benneke B., Scott N., Deacon N.,
Aller K.M., Hansen B.M.S., Mancini L., Ciceri S., Brahm R., Jordan A.,
Knutson H.A., Henning T., Bonnefoy M., Liu M.C., Crepp J.R., Lothringer J.,
Hinz P., Bailey V., Skemer A., Defrere D.
<Astrophys. J. Suppl. Ser., 226, 7-7 (2016)>
=2016ApJS..226....7C 2016ApJS..226....7C (SIMBAD/NED BibCode)
ADC_Keywords: Stars, double and multiple ; Planets ; Radial velocities ;
Stars, diameters ; Stars, masses
Keywords: catalogs; planets and satellites: fundamental parameters;
planets and satellites: general; techniques: high angular resolution;
techniques: photometric; techniques: spectroscopic
Abstract:
We present 197 planet candidates discovered using data from the first
year of the NASA K2 mission (Campaigns 0-4), along with the results of
an intensive program of photometric analyses, stellar spectroscopy,
high-resolution imaging, and statistical validation. We distill these
candidates into sets of 104 validated planets (57 in multi-planet
systems), 30 false positives, and 63 remaining candidates. Our
validated systems span a range of properties, with median values of
RP=2.3R⊕, P=8.6 days, Teff=5300K, and Kp=12.7mag. Stellar
spectroscopy provides precise stellar and planetary parameters for
most of these systems. We show that K2 has increased by 30% the number
of small planets known to orbit moderately bright stars
(1-4R⊕, Kp=9-13mag). Of particular interest are 76 planets
smaller than 2R⊕, 15 orbiting stars brighter than Kp=11.5mag,
5 receiving Earth-like irradiation levels, and several multi-planet
systems-including 4 planets orbiting the M dwarf K2-72 near
mean-motion resonances. By quantifying the likelihood that each
candidate is a planet we demonstrate that our candidate sample has an
overall false positive rate of 15%-30%, with rates substantially lower
for small candidates (<2R⊕) and larger for candidates with
radii >8R⊕ and/or with P<3days. Extrapolation of the current
planetary yield suggests that K2 will discover between 500 and 1000
planets in its planned four-year mission, assuming sufficient
follow-up resources are available. Efficient observing and analysis,
together with an organized and coherent follow-up strategy, are
essential for maximizing the efficacy of planet-validation efforts for
K2, TESS, and future large-scale surveys.
Description:
We select our FGK stellar sample from the all-sky Transiting Exoplanet
Survey Satellite (TESS) Dwarf Catalog (TDC; Stassun et al. 2014,
1410.6379). We extract time-series photometry from the target
pixel files provided by the K2 project using circular, stationary,
soft-edged apertures. See section 2 for further explanations.
We obtained high-resolution optical spectra of 83 planet candidate
hosts using the HIRES echelle spectrometer on the 10m Keck I telescope
(R=55000).
We obtained spectra of 27 candidate host stars using the Levy
high-resolution optical spectrograph mounted at the Automated Planet
Finder (APF; R∼80000 or 100000).
We obtained spectra of a small number of candidate stellar hosts using
the FEROS fiber-fed echelle spectrograph at the 2.2m MPG telescope
(R∼48000).
See section 3.1 for further details.
We obtained high-resolution imaging (HRI) for 164 of our candidate
systems. Our primary instrument for this work was NIRC2 at the 10m
Keck II telescope, with which we observed 110 systems. As part of
multi-semester program GN-2015B-LP-5 (PI Crossfield) at Gemini
Observatory, we observed 40 systems with the NIRI camera in the
K-band. We also observed 33 stars with PHARO/PALM-3000 at the 5m Hale
Telescope and 14 systems with LMIRCam at LBT, all at the K-band. We
observed 39 stars at visible wavelengths using the automated Robo-AO
laser adaptive optics system at the Palomar 1.5m telescope.
Through our Long-Term Gemini program we also acquired high-resolution
speckle imaging of 32 systems in narrowband filters centered at 692
and 880nm using the DSSI camera at the Gemini North telescope.
See section 3.3 for further explanations.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table3.dat 59 112 HIRES follow-up observations
table4.dat 49 80 FEROS radial velocities
table5.dat 42 104 HRI-detected stellar companions
table7.dat 71 167 Stellar parameters
table8.dat 169 197 Planet candidate parameters
table9.dat 78 51 Unvalidated candidate false positive likelihoods
table10.dat 30 265 High-resolution imaging
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See also:
J/A+A/594/A50 : K2-30 b and K2-34 b K2 light curves (Lillo-Box+, 2016)
J/ApJS/224/12 : Kepler planetary candidates. VII. 48-month (Coughlin+, 2016)
J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)
J/ApJ/822/86 : False positive proba. for Q1-Q17 DR24 KOIs (Morton+, 2016)
J/A+A/587/A64 : Physical properties of giant exoplanets (Santerne+, 2016)
J/MNRAS/456/2260 : K2 Variability Catalogue II (Armstrong+, 2016)
J/ApJS/222/14 : Planetary candidates from 1st yr K2 mission (Vanderburg+, 2016)
J/ApJ/814/130 : Planet occurrence rates calculated for KOIs (Mulders+, 2015)
J/MNRAS/452/3561 : Kepler EB stars. K2 Campaign 0 (LaCourse+, 2015)
J/A+A/582/A33 : K2-19b light curve (Armstrong+, 2015)
J/ApJ/810/95 : Kepler pipeline S/N studies II. 2011 data (Christiansen+, 2015)
J/ApJ/807/45 : Potentially habitable planets around M dwarfs (Dressing+, 2015)
J/A+A/577/A132 : Stellar parameters of early M dwarfs (Maldonado+, 2015)
J/ApJ/784/45 : Kepler's multiple planet candidates. III. (Rowe+, 2014)
J/ApJ/770/69 : Kepler planet candidates radii (Petigura+, 2013)
J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)
J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)
J/AJ/144/42 : Infrared photometry of 90 KOIs (Adams+, 2012)
J/other/Sci/330.653 : Detected planets in the Eta-Earth Survey (Howard+, 2010)
http://archive.stsci.edu/k2/catalogs.html : MAST K2 catalogs
Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
2- 10 I9 --- EPIC Ecliptic Plane Input Catalog (EPIC) number for K2
12 I1 --- Flag Flag (1)
14- 59 A46 --- Note Notes on Object
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Note (1): HIRES Flags as follows:
1 = No detection of second spectrum at noted flux ratio;
2 = Star is unfit for ReaMatch: Teff below 3500 K;
3 = Star is unfit for ReaMatch: vsin(i) above 10 km/s;
4 = Ambiguous detection;
5 = Obvious detection.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC Ecliptic Plane Input Catalog (EPIC) number for K2
11- 26 F16.8 d BJD Barycentric Julian Date
28- 35 F8.3 km/s RV [-130.2/93.4] Radial Velocity
37- 41 F5.3 km/s e_RV [0.01/7] Uncertainty in RV
43- 46 I4 s Tint [420/1800] Integration time
48- 49 I2 --- S/N [3/97] Signal-to-noise of spectra
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC Ecliptic Plane Input Catalog (EPIC) number for K2
11- 16 F6.3 arcsec Aper [5.5/20]? Aperture radius used for photometry
18- 23 F6.3 arcsec rho [0.06/18.5] Stellar companion separation
25- 29 F5.2 mag dmag [-2.2/9.6] Target/Companion magnitude difference
31 A1 --- Filt [Kabi] Filter (76 "K", 23 "i", 3 "b" and 2 "a")
33- 42 A10 --- Tel Telescope (GemN-NIRI, GemN-Spk, GemS-GNIRS, Keck2,
LBT, Palomar or Robo-AO)
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Byte-by-byte Description of file: table7.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC Ecliptic Plane Input Catalog (EPIC) number
for K2
11- 16 F6.3 mag Kpmag [8.7/18.7] Kp magnitude
18- 24 F7.4 Rsun Rstar [0.1/10] Stellar radius (1)
26- 31 F6.4 Rsun e_Rstar [0.007/4] Uncertainty in Rstar (1)
33- 38 F6.4 Msun Mstar [0.15/1.8] Stellar mass
40- 45 F6.4 Msun e_Mstar [0.007/0.4] Uncertainty in Mstar
47- 50 I4 K Teff [3252/7747] Stellar effective temperature
52- 54 I3 K e_Teff [0/787] Uncertainty in Teff
56- 61 F6.4 [cm/s2] logg [2.3/5.2] log10 surface gravity
63- 69 F7.5 [cm/s2] e_logg [0.004/1] Uncertainty in logg
71- 71 I1 --- Ref Source (2)
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Note (1): Stellar radii from Huber et al. (2016, J/ApJS/224/2) tend to
systematically underestimate the sizes of the smallest stars (<0.6 Rsun)
Note (2): Source as follows:
1 = Huber et al. (2016, J/ApJS/224/2);
2 = SpecMatch, Petigura (2015PhDT........82P 2015PhDT........82P);
3 = isochrones Python package, Morton (2015ascl.soft03010M).
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Byte-by-byte Description of file: table8.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Kepler Kepler Planet Name
11- 22 F12.2 --- EPIC Ecliptic Plane Input Catalog (EPIC) number for K2
24- 33 F10.7 d Per [0.36/80] Orbital period
35- 43 F9.7 d e_Per [0/0.02] Uncertainty in Period
45- 55 F11.6 d T0 T0, BJDTDB-2454833
57- 64 F8.6 d e_T0 Uncertainty in T0, BJDTDB-2454833
66- 72 F7.4 h T14 [0/15.1] T14 time
74- 79 F6.4 h e_T14 [0/2.4] Uncertainty in T14
81- 86 F6.3 --- Rp/R* [1/76] Ratio Planet to Star radius, Rp/R*
88- 93 F6.3 --- e_Rp/R* [0.03/35] Uncertainty in Rp/R*
95-101 F7.5 AU a [0.01/0.3] Orbital semi-major axis
103-109 F7.5 AU e_a [0/0.02] Uncertainty in a
111-117 F7.3 Rgeo Rp [0.6/256] Planet Radius
119-125 F7.3 Rgeo e_Rp [0/101] Uncertainty in Rp
127-134 F8.2 Earth Sinc [0.7/56139] Incident irradiation (Sinc)
136-143 F8.2 Earth e_Sinc [0.2/15807] Uncertainty in Sinc
145-151 E7.2 --- FPP False Positive Probability
153-166 A14 --- Disp Disposition (110 "Planet", 62 "Candidate" and
25 "False Positive")
168-169 I2 --- Flag ? Disposition flag (1)
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Note (1): Disposition flag as follows:
1 = candidate has large radius;
2 = see discussion of previous confirmations, Section 7.2.2;
3 = see discussion of previous detections, Section 7.2.3;
5 = see HRI data and spec. companion analysis, Tables 6 and 3;
6 = see FEROS and HRI data, Tables 1 and 6;
7 = see FEROS data and spec. companion analysis, Tables 1 and 3;
8 = see HRI data, Table 6;
9 = see FEROS data, Table 1;
10 = see spec. companion analysis, Table 3;
11 = Validated by Sanchis-Ojeda et al. (2015ApJ...812..112S 2015ApJ...812..112S).
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Byte-by-byte Description of file: table9.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 12 F12.2 --- EPIC Target
14- 21 E8.6 --- Lheb [0/5.3] Vespa (2015ascl.soft03011M) likelihood,
hierarchical eclipsing binary at orbital
period
23- 30 E8.6 --- Lheb-Px2 [0/5.2] Vespa (2015ascl.soft03011M) likelihood,
hierarchical eclipsing binary at twice orbital
period
32- 38 A7 --- Leb Vespa (2015ascl.soft03011M) likelihood,
eclipsing binary at orbital period
40- 46 A7 --- Leb-Px2 Vespa (2015ascl.soft03011M) likelihood,
eclipsing binary at twice orbital period
48- 54 E7.5 --- Lbeb [0/1.3] Vespa (2015ascl.soft03011M) likelihood,
background eclipsing binary at orbital period
56- 62 E7.5 --- Lbeb-Px2 [0/5.6] Vespa (2015ascl.soft03011M) likelihood,
background eclipsing binary at twice orbital
period
64- 70 E7.5 --- Lpl [0/36] Vespa (2015ascl.soft03011M) likelihood,
planet
72- 78 E7.5 --- FPP False Positive Probability
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Byte-by-byte Description of file: table10.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC Ecliptic Plane Input Catalog (EPIC) number for K2
11- 15 A5 --- Filt Filter (J, K, LP600, 692 or 880)
17- 22 F6.1 s Tint [7.5/2141] Integration Time
24- 30 A7 --- Inst Instrument (NIRC2, NIRI, PHARO, DSSI, Robo-AO,
LMIRCam or GNIRS)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 24-Oct-2016