J/AJ/155/136 Planets orbiting bright stars in K2 campaigns 0-10 (Mayo+, 2018)
275 candidates and 149 validated planets orbiting bright stars in
K2 campaigns 0-10.
Mayo A.W., Vanderburg A., Latham D.W., Bieryla A., Morton T.D.,
Buchhave L.A., Dressing C.D., Beichman C., Berlind P., Calkins M.L.,
Ciardi D.R., Crossfield I.J.M., Esquerdo G.A., Everett M.E., Gonzales E.J.,
Hirsch L.A., Horch E.P., Howard A.W., Howell S.B., Livingston J., Patel R.,
Petigura E.A., Schlieder J.E., Scott N.J., Schumer C.F., Sinukoff E.,
Teske J., Winters J.G.
<Astron. J., 155, 136 (2018)>
=2018AJ....155..136M 2018AJ....155..136M (SIMBAD/NED BibCode)
ADC_Keywords: Stars, bright ; Exoplanets ; Photometry ; Optical ;
Photometry, infrared ; Stars, diameters ; Stars, masses ;
Effective temperatures ; Abundances ; Stars, double and multiple
Keywords: methods: data analysis ; planets and satellites: detection ;
techniques: photometric
Abstract:
Since 2014, NASA's K2 mission has observed large portions of the ecliptic
plane in search of transiting planets and has detected hundreds of
planet candidates. With observations planned until at least early 2018,
K2 will continue to identify more planet candidates. We present here
275 planet candidates observed during Campaigns 0-10 of the K2 mission
that are orbiting stars brighter than 13 mag (in Kepler band) and for
which we have obtained high-resolution spectra (R=44000). These candidates
are analyzed using the vespa package in order to calculate their
false-positive probabilities (FPP). We find that 149 candidates are
validated with an FPP lower than 0.1%, 39 of which were previously only
candidates and 56 of which were previously undetected. The processes
of data reduction, candidate identification, and statistical validation
are described, and the demographics of the candidates and newly validated
planets are explored. We show tentative evidence of a gap in the planet
radius distribution of our candidate sample. Comparing our sample to
the Kepler candidate sample investigated by Fulton et al. (2017,
J/AJ/154/109), we conclude that more planets are required to quantitatively
confirm the gap with K2 candidates or validated planets. This work, in
addition to increasing the population of validated K2 planets by nearly 50%
and providing new targets for follow-up observations, will also serve
as a framework for validating candidates from upcoming K2 campaigns and
the Transiting Exoplanet Survey Satellite, expected to launch in 2018.
Description:
All of the spectra used in this work were obtained with TRES, a
spectrograph with a resolving power of R=44000 and one of two spectrographs
for the 1.5 m Tillinghast telescope at the Whipple Observatory on
Mt. Hopkins in Arizona.
We observed many of our planet candidates with speckle imaging from either
the 3.5 m WIYN telescope, the Gemini-South 8.1 m telescope, or the
Gemini-North 8.1 m telescope. Together, the three telescopes collected 162
speckle images of 73 stars with DSSI (Horch et al. 2009AJ....137.5057H 2009AJ....137.5057H).
In addition to speckle imaging, we also observed many of our planet
candidate host stars with AO imaging. We collected 47 AO images for 45
stars on the Keck II 10 m telescope in K filter with the Near Infra Red
Camera 2 (NIRC2); 5 of these stars were also imaged using NIRC2 in J band.
All of these observations were made during 2015 April, July, August, and
October and in 2016 January and February. We collected 27 AO images for
27 stars on the Palomar 5.1 m Hale telescope in K filter with the Palomar
High Angular Resolution Observer (PHARO, Hayward et al. 2001); 6 of these
stars were also imaged using PHARO in J band. All of these observations
were made during 2015 February, May, and August and in 2016 June,
September, and October. We collected 19 AO images for 18 stars on the
Gemini-North 8.1 m telescope in K band with the Near InfraRed Imager and
spectrograph (NIRI, Hodapp et al. 2003SPIE.4841..869H 2003SPIE.4841..869H). These observations
were made during 2015 October and November and in 2016 June and October.
We collected a single AO image on the Large Binocular Telescope in K filter
with the L/M-band mid-infraRed Camera (LMIRCam, Leisenring et al.
2012SPIE.8446E..4FL). This observation was made in 2015 January.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 21 428 High-resolution imaging
table2.dat 245 275 Planet candidate parameters
table3.dat 91 233 Stellar parameters
table4.dat 42 28 Stellar SHK activity index
table5.dat 129 275 Detailed FPP table
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See also:
V/50 : Bright Star Catalogue, 5th Revised Ed. (Hoffleit+, 1991)
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/A+A/579/A19 : K2 Variable Catalogue (Armstrong+, 2015)
J/ApJ/809/25 : Stellar and planet properties for K2 candidates
(Montet+, 2015)
J/ApJ/809/77 : Transiting Exoplanet Survey Satellite (TESS)
(Sullivan+, 2015)
J/MNRAS/452/3561 : Kepler eclipsing binary stars. K2 Campaign 0
(LaCourse+, 2015)
J/A+A/586/A94 : Exoplanetary parameters for 18 bright stars (Ligi+, 2016)
J/A+A/594/A100 : K2 new planetary and EB candidates (Barros+, 2016)
J/ApJ/829/L9 : K2 LC of HD 3167 and Robo-AO image (Vanderburg+, 2016)
J/ApJS/222/14 : Planetary candidates from 1st yr K2 mission
(Vanderburg+, 2016)
J/ApJS/224/2 : K2 EPIC stellar properties for 138600 targets (Huber+, 2016)
J/ApJS/224/12 : Kepler planetary candidates. VII. 48-month (Coughlin+, 2016)
J/ApJS/226/7 : Planet candidates discovered using K2's 1st yr
(Crossfield+, 2016)
J/AJ/153/66 : Robo-AO Kepler Planetary Candidate Survey. III.
(Ziegler+, 2017)
J/AJ/154/109 : California-Kepler Survey (CKS). III. Planet radii
(Fulton+, 2017)
J/AJ/155/21 : Planet candidates from K2 campaigns 5-8 (Petigura+, 2018)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC [201110617/229133720] EPIC number (EPIC NNNNNNNNN)
11- 13 A3 --- Filter Filter used (1)
15- 21 A7 --- Inst Instrument
--------------------------------------------------------------------------------
Note (1): A number gives the central wavelength of the filter in nm.
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Byte-by-byte Description of file: table2.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- K2 K2 identifier (K2-NNNa)
10- 21 A12 --- EPIC EPIC number (EPIC NNNNNNNNN.NN)
23- 33 F11.6 d T0 [1939.7758/2800.07702] Mid-transit time
(BJD-2454833)
35- 42 F8.6 d E_T0 [9e-05/0.021] Upper uncertainty in T0
44- 51 F8.6 d e_T0 [8.8e-05/0.019] Lower uncertainty in T0
53- 62 F10.7 d Per [0.251647/59.84857] Period
64- 72 F9.7 d E_Per [1e-06/0.015] Upper uncertainty in Per
74- 82 F9.7 d e_Per [1e-06/0.016] Lower uncertainty in Per
84- 90 F7.3 --- a/R* [1.4/114.7] Semi-major axis relative to stellar
radius
92- 97 F6.3 --- E_a/R* [0.05/33] Upper uncertainty in a/R*
99-104 F6.3 --- e_a/R* [0.048/39] Lower uncertainty in a/R*
106-111 F6.3 deg Inc [25/89.854] Inclination
113-118 F6.3 deg E_Inc [0.024/56] Upper uncertainty in Inc
120-125 F6.3 deg e_Inc [0.021/34] Lower uncertainty in Inc
127-133 F7.5 --- Rp/R* [0.0062/0.31] Planetary radius relative to
stellar radius
135-141 F7.5 --- E_Rp/R* [0.00056/0.38] Upper uncertainty in Rp/R*
143-149 F7.5 --- e_Rp/R* [0/0.11] Lower uncertainty in Rp/R*
151-157 F7.3 --- Rp/Re [0.58/317] Planetary radius relative to Earth
radius Rp/R⊕
159-165 F7.3 --- E_Rp/Re [0.089/371] Upper uncertainty in Rp/Re
167-173 F7.3 --- e_Rp/Re [0.057/179] Lower uncertainty in Rp/Re
175-180 F6.3 Rsun R* [0.589/16] Stellar radius
182-186 F5.3 Rsun E_R* [0.015/4.6] Upper uncertainty in R*
188-192 F5.3 Rsun e_R* [0.013/2.7] Lower uncertainty in R*
194-198 F5.3 Msun M* [0.61/2.02] Stellar mass
200-204 F5.3 Msun E_M* [0.019/0.47] Upper uncertainty in M*
206-210 F5.3 Msun e_M* [0.01/0.18] Lower uncertainty in M*
212-217 F6.3 mag Kpmag [7.218/13.5] Kepler apparent magnitude
219 A1 --- l_FPP Limit flag on FPP
220-227 E8.3 --- FPP [0/0.996]? False Positive Probability (1)
229-237 A9 --- Disp Disposition (Planet or Candidate)
239-245 A7 --- Notes Note code(s) (G1)
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Note (1): The probability that a candidate is an astrophysical false positive
rather than a true positive (i.e., a planet).
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Byte-by-byte Description of file: table3.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- EPIC EPIC number (EPIC NNNNNNNNN)
11- 16 F6.1 K Teff [4315/6398] Effective temperature
18- 22 F5.1 K e_Teff [50/101] Uncertainty in Teff
24- 28 F5.2 [Sun] [M/H] [-1.1/0.48] Metallicity
30- 34 F5.3 [Sun] e_[M/H] [0.08/0.095] Uncertainty in [M/H]
36- 39 F4.2 [cm/s2] log(g) [2.07/4.74] Log surface gravity
41- 45 F5.3 [cm/s2] e_log(g) [0.1/0.166] Uncertainty in log(g)
47- 52 F6.3 Rsun R* [0.589/16] Stellar radius
54- 58 F5.3 Rsun E_R* [0.015/4.6] Upper uncertainty in R*
60- 64 F5.3 Rsun e_R* [0.013/2.7] Lower uncertainty in R*
66- 70 F5.3 Msun M* [0.61/2.02] Stellar mass
72- 76 F5.3 Msun E_M* [0.019/0.47] Upper uncertainty in M*
78- 82 F5.3 Msun e_M* [0.01/0.18] Lower uncertainty in M*
84- 89 F6.3 mag Kpmag [7.218/13.5] Kepler apparent magnitude
91 A1 --- n_EPIC [ab] Note on EPIC (1)
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Note (1): Note as follows:
a = Stellar parameters for this star are derived from a single spectrum with
a cross correlation function peak height <0.9 (but >0.8). We have decided
the resulting stellar parameters are trustworthy for this analysis, but
provide a note for the reader's discretion;
b = SHK values have been determined for this star and can be found in
Table 4.
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Byte-by-byte Description of file: table4.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 I9 --- EPIC [201437844/211993818] EPIC number
(EPIC NNNNNNNNN)
11- 21 A11 "date" Date Date of observation
23- 28 F6.4 --- SHK [0.1453/0.4189] SHK stellar activity index (1)
30- 35 F6.4 --- e_SHK [0.0027/0.0045] Lower uncertainty in SHK
37- 42 F6.4 --- E_SHK [0.0027/0.0044] Upper uncertainty in SHK
--------------------------------------------------------------------------------
Note (1): SHK is a ratio between the flux in the cores of the calcium II H and
K spectral features (at 3933.66±1.09 and 3968.47±1.09 Å) and the flux
in two nearby continuum regions (one slightly redward of the Ca II lines,
called R, and one slightly blueward, called V). SHK is commonly used as a
proxy for a star's chromospheric activity (Isaacson & Fischer 2010,
J/ApJ/725/875).
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 8 A8 --- K2 K2 identifier (K2-NNNa)
10- 21 A12 --- EPIC EPIC number (EPIC NNNNNNNNN.NN)
23- 25 I3 ppm Thres [5/945] Secondary eclipse threshold
27- 30 F4.1 arcsec ApRad [12.4/42.2] Aperture radius
32 A1 --- AO-Speck [Y/N] AO or Speckle observation?
34 A1 --- l_PEB [<] Limit flag on PEB
35- 42 E8.2 --- PEB [0/0.866]? Probability of eclipsing binary
44 A1 --- l_PEBx2 [<] Limit flag on PEBx2
45- 52 E8.2 --- PEBx2 [0/0.988]? Probability of eclipsing binary
at twice the period
54 A1 --- l_PBEB [<] Limit flag on PBEB
55- 62 E8.2 --- PBEB [0.0001/0.231]? Probability of background
eclipsing binary
64 A1 --- l_PBEBx2 [<] Limit flag on PBEBx2
65- 72 E8.2 --- PBEBx2 [0.0001/1.0]? Probability of background
eclipsing binary at twice the period
74 A1 --- l_PHEB [<] Limit flag on PHEB
75- 82 E8.2 --- PHEB [0.0001/0.375]? Probability of hierarchical
eclipsing binary
84 A1 --- l_PHEBx2 [<] Limit flag on PHEBx2
85- 92 E8.2 --- PHEBx2 [0.0001/0.0176]? Probability of hierarchical
eclipsing binary at twice the period
94 A1 --- RVMLim [Y/N] Radial velocity mass limit?
96-104 E9.2 --- VFPP [-0.000276/1]? Vespa False Positive
Probability
106-107 I2 --- Multi [25/50]? Multiplicity boost (1)
109 A1 --- l_AFPP [<] Limit flag on AFPP
110-117 E8.2 --- AFPP [0.0001/0.996]? Adopted False Positive
Probability
119-127 A9 --- Disp Disposition (Planet or Candidate)
129 A1 --- Note Note code (G1)
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Note (1): Systems with multiple planet candidates are more likely to be hosting
multiple planets than multiple false-positive signals. In fact, the likelihood
of the planet scenario for each individual candidate is consequently boosted
relative to false-positive scenarios in multiplanet candidate systems
(Latham et al. 2011ApJ...732L..24L 2011ApJ...732L..24L). To account for this effect, we apply a
"multiplicity boost" to the planet scenario prior in such systems, deflating
the FPP by the multiplicity boost factor to account for the nature of these
systems. We choose a boost factor of 25 for double-candidate systems and a
boost factor of 50 for systems with three or more candidates based on the
values used by Lissauer et al. (2012ApJ...750..112L 2012ApJ...750..112L), Vanderburg et al.
(2016, J/ApJ/829/L9), and Sinukoff et al. (2016ApJ...827...78S 2016ApJ...827...78S).
--------------------------------------------------------------------------------
Global notes:
Note (G1): Note as follows:
a = Unless there is a deep secondary eclipse or ellipsoidal variations in the
light curve, VESPA cannot distinguish between a planet-sized star and a
planet. In this case, Rp>8 R⊕ and RV measurements cannot rule
out the foreground eclipsing binary scenario. Therefore, a FPP value
is not reported;
b = Companion in aperture, therefore a FPP is not reported;
c = AO/Speckle companion, therefore a FPP is not reported;
d = Composite spectrum, therefore a FPP is not reported;
e = Large RV amplitude variations confirm a binary in the system, therefore
a FPP is not reported;
f = VESPA failed to find a FPP;
g = HD 106315;
h = K2-51 is a false positive (see Shporer et al. 2017ApJ...847L..18S 2017ApJ...847L..18S and
Section 6.2);
i = WASP-152;
j = WASP-157;
k = HATS-12;
l = HD 3167.
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History:
From electronic version of the journal
(End) Prepared by [AAS], Tiphaine Pouvreau [CDS] 08-Nov-2018