J/ApJS/278/52 Planet masses, radii, and orbits from K2 mission (Howard+, 2025)
Planet masses, radii, and orbits from NASA's K2 mission.
Howard A.W., Sinukoff E., Blunt S., Petigura E.A., Crossfield I.J.M.,
Isaacson H., Kosiarek M., Rubenzahl R.A., Brewer J.M., Fulton B.J.,
Dressing C.D., Hirsch L.A., Knutson H., Livingston J.H., Mills S.M.,
Roy A., Weiss L.M., Benneke B., Ciardi D.R., Christiansen J.L.,
Cochran W.D., Crepp J.R., Gonzales E., Hansen B.M.S., Hardegree-Ullman K.,
Howell S.B., Lepine S., Martinez A.O., Rogers L.A., Schlieder J.E.,
Werner M., Polanski A.S., Angelo I., Beard C., Behmard A., Bouma L.G.,
Brinkman C.L., Chontos A., Dai F., Dalba P.A., Giacalone S.,
Grunblatt S.K., Hill M.L., Kane S.R., Lubin J., Mayo A.W., Mocnik T.,
Murphy J.M.A., Rice M., Rosenthal L.J., Tyler D., Van Zandt J., Yee S.W.
<Astrophys. J. Suppl. Ser., 278, 52 (2025)>
=2025ApJS..278...52H 2025ApJS..278...52H
ADC_Keywords: Exoplanets; Stars, diameters; Stars, masses; Abundances, [Fe/H];
Rotational velocities; Radial velocities; Photometry;
Spectra, optical
Keywords: Exoplanet catalogs ; Exoplanet astronomy ; Radial velocity ;
Transit photometry
Abstract:
We report the masses, sizes, and orbital properties of 86 planets
orbiting 55 stars observed by NASA's K2 Mission with follow-up Doppler
measurements by the HIRES spectrometer at the W. M. Keck Observatory
and the Automated Planet Finder at Lick Observatory. Eighty-one of the
planets were discovered from their transits in the K2 photometry,
while five were found based on subsequent Doppler measurements of
transiting planet-host stars. The sizes of the transiting planets
range from Earth-size to larger than Jupiter (1-3R⊕ is
typical), while the orbital periods range from less than a day to a
few months. For 32 of the planets, the Doppler signal was detected
with significance greater than 5σ (51 were detected with
>3σ significance). An important characteristic of this catalog
is the use of uniform analysis procedures to determine stellar and
planetary properties. This includes the transit search and fitting
procedures applied to the K2 photometry, the Doppler fitting
techniques applied to the radial velocities (RVs), and the spectral
modeling to determine bulk stellar parameters. Such a uniform
treatment will make the catalog useful for statistical studies of the
masses, densities, and system architectures of exoplanetary systems.
This work also serves as a data release for all previously unpublished
RVs and associated stellar activity indicators obtained by our team
for these systems, along with derived stellar and planet parameters.
Description:
We conducted a search for planets orbiting stars observed by the K2
mission (Howell+ 2014PASP..126..398H 2014PASP..126..398H). The K2 mission followed the
Kepler mission using the same spacecraft, telescope, and photometer.
K2 operated during 2014-2018 with 20 pointings along the ecliptic,
each lasting about 80 days. Each of these "Campaigns" produced time
series photometry for bright stars in the ∼100deg2 fields.
Our K2 search began with sets of proposals to observe FGK dwarfs and
M dwarfs. We selected ∼10,000 FGK dwarfs per K2 Field from the TESS
Dwarf Catalog (TDC; Ricker+ 2015JATIS...1a4003R 2015JATIS...1a4003R).
The targets selected for observation in our Keck/HIRES RV program were
taken from our K2 transit light curve transit search efforts described
in Section 2.2. Table 1 lists the stars observed for our HIRES program.
We used the HIRES spectrometer on the Keck I telescope at the W. M.
Keck Observatory to measure optical spectra of all targets presented
in this paper. These spectra span 3640-7990Å and most have a
resolution of R=60000. See Section 3.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 89 56 Host star parameters
table2.dat 110 56 Host star properties
table3.dat 206 87 Derived properties of planets orbiting target stars
table4.dat 60 3364 Radial velocity measurements
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See also:
IV/34 : K2 Ecliptic Plane Input Catalog (EPIC) (Huber+, 2017)
I/345 : Gaia DR2 (Gaia Collaboration, 2018)
I/355 : Gaia DR3 Part 1. Main source (Gaia Collaboration, 2022)
J/other/Sci/330.653 : Detected planets in the Eta-Earth Survey (Howard+, 2010)
J/ApJ/725/875 : Chromospheric activity for CPS stars (Isaacson+, 2010)
J/ApJ/757/112 : Stellar diameters. II. K and M-stars (Boyajian+, 2012)
J/MNRAS/426/739 : Velocities for seven transiting hot Jupiters (Hellier+, 2012)
J/A+A/582/A33 : K2-19b light curve (Armstrong+, 2015)
J/ApJ/805/175 : Keck and APF radial velocities of HD7924 (Fulton+, 2015)
J/ApJ/806/183 : Planet radii of Kepler Object of Interest (Wolfgang+, 2015)
J/A+A/594/A100 : K2 new planetary and EB candidates (Barros+, 2016)
J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016)
J/ApJS/226/7 : Planet cand. discovered using K2's 1st yr (Crossfield+, 2016)
J/ApJ/829/L9 : K2 LC of HD 3167 and Robo-AO image (Vanderburg+, 2016)
J/ApJS/222/14 : Planetary cand. from 1st yr K2 mission (Vanderburg+, 2016)
J/AJ/154/122 : RVels for the HD 3167 system (Christiansen+, 2017)
J/A+A/608/A35 : K2-18 HARPS time-series (Cloutier+, 2017)
J/ApJ/836/167 : K2 planet. syst. around low-mass stars. I. (Dressing+, 2017)
J/AJ/154/109 : California-Kepler Survey (CKS). III. Radii (Fulton+, 2017)
J/AJ/154/123 : RVel follow-up of the HD 3167 system (Gandolfi+, 2017)
J/A+A/608/A93 : K2-106 radial velocities measurements (Guenther+, 2017)
J/AJ/154/237 : HARPS-N radial velocities of WASP-47 (Vanderburg+, 2017)
J/ApJ/836/77 : A library of high-S/N optical sp. of FGKM stars (Yee+, 2017)
J/ApJS/237/38 : Extended abundance analysis of KOIs (Brewer+, 2018)
J/ApJS/239/5 : Variable stars and cand. planets from K2 (Crossfield+, 2018)
J/A+A/615/A69 : K2-3 system with HARPS-N & HARPS (Damasso+, 2018)
J/AJ/156/264 : California-Kepler Survey. VII. Radius gap (Fulton+, 2018)
J/AJ/156/22 : Planetary candidates from K2 Campaign 16 (Yu+, 2018)
J/A+A/621/A49 : K2-18 HARPS time-series (Cloutier+, 2019)
J/A+A/624/A38 : Radial velocities of K2-36 (Damasso+, 2019)
J/AJ/157/169 : Exoplanets from deep learning in K2 (Dattilo+, 2019)
J/AJ/158/87 : Cool dwarfs during K2 Campaigns 1-17 (Dressing+, 2019)
J/A+A/634/L4 : HST/STIS FUV spectra of K2-18 (dos Santos+, 2020)
J/ApJS/247/28 : K2 star param. from Gaia & LAMOST (Hardegree-Ullman+, 2020)
J/MNRAS/496/851 : Planet candidates from K2 Campaigns 1-13 (Wittenmyer+, 2020)
J/AJ/159/154 : Exoplanet cand. in Campaign 5 of the K2 mission (Zink+, 2020)
J/ApJS/254/39 : Exoplanet cand. from TESS first 2yr obs (Guerrero+, 2021)
J/AJ/162/259 : Scaling K2. IV. Campaigns 1-8 & 10-18 (Zink+, 2021)
J/A+A/668/A31 : A CHEOPS-enhanced view of the HD3167 system (Bourrier+, 2022)
J/A+A/677/A33 : 38 Kepler and K2 systems RVs (Bonomo+, 2023)
J/AJ/165/60 : TESS-Keck Survey. XIV. 2 exoplanets (Van Zandt+, 2023)
J/AJ/165/262 : Scaling K2. VI. HIRES stellar param. (Zink+, 2023)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Star name
16 A1 --- f_Name Flag on K2-19 (1)
18- 23 A6 --- Other ? Other name
25- 33 I9 --- EPIC [201357835/247418783] EPIC number
35- 38 A4 --- Field Field
40- 41 I2 h RAh [0/23] Hour of right ascension (J2000)
43- 44 I2 min RAm Minute of right ascension (J2000)
46- 50 F5.2 s RAs Second of right ascension (J2000)
52 A1 --- DE- [±] Sign of declination (J2000)
53- 54 I2 deg DEd [0/29] Degree of declination (J2000)
56- 57 I2 arcmin DEm Arcminute of declination (J2000)
59- 63 F5.2 arcsec DEs Arcsecond of declination (J2000)
66- 71 F6.3 mag Vmag [8.9/13.6]? Apparent V-band magnitude
73- 77 F5.3 mag e_Vmag [0.01/0.5]? Uncertainty in Vmag
79- 81 I3 --- HIRES [6/352] Number of RV observations from HIRES
used
83- 85 I3 --- APF [0/125] Number of RV observations from APF used
87- 89 I3 --- Lit [0/389] Number of RV observations from
literature used
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Note (1): Flag as follows:
p = The RVs mentionned in Section A.53 were published earlier in
Petigura+ 2020AJ....159....2P 2020AJ....159....2P and no additional spectra were obtained
for this star; note added by CDS.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 14 A14 --- Name Star name
16- 20 F5.3 Rsun Rs [0.46/3.1]? Stellar radius
22- 26 F5.3 Rsun e_Rs [0.015/0.2]? Uncertainty in Rs
28- 32 F5.3 Msun Ms [0.3/2.83]? Stellar mass
34- 38 F5.3 Msun e_Ms [0.018/1]? Uncertainty in Ms
40- 44 F5.2 km/s Vsini [0.1/13.3]? Projected rotational velocity
46- 48 F3.1 km/s e_Vsini [0.5/1.1]? Uncertainty in Vsini
50- 57 F8.3 K Teff [0.9/6364]? Effective temperature
59- 65 F7.3 K e_Teff [0.038/189]? Uncertainty in Teff
67- 71 F5.3 [-] logg [3.58/4.74]? Log of surface gravity
73- 77 F5.3 [-] e_logg [0.006/0.2]? Uncertainty in logg
79- 84 F6.4 --- SHK [0.1/0.78]? S index
86- 92 F7.4 [-] logRHK [-5.41/-4.4]? Log of chromospheric activity
index
94- 97 F4.2 [-] e_logRHK [0.03]? Uncertainty in logRHK
99- 104 F6.3 [-] [Fe/H] [-0.71/0.43]? Metallicity
106- 110 F5.3 [-] e_[Fe/H] [0.04/0.13]? Uncertainty in [Fe/H]
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Byte-by-byte Description of file: table3.dat
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Bytes Format Units Label Explanations
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1- 15 A15 --- Name Planet name
17- 33 F17.12 d Per [0.57/1088] Orbital period
35- 46 F12.8 d e_Per [4.3e-07/100] Lower uncertainty in Per
48- 59 F12.8 d E_Per [4.3e-07/100] Upper uncertainty in Per
61- 74 F14.6 d Time ? Mid-transit time; barycentric Julian date
76- 84 F9.6 d e_Time [3.2e-05/99]? Lower uncertainty in Time
86- 94 F9.6 d E_Time [3.2e-05/65]? Upper uncertainty in Time
96- 101 F6.3 Rgeo Rad [1.1/46]? Radius
103- 109 F7.5 Rgeo e_Rad [0.03/8]? Lower uncertainty in Rad
111- 117 F7.5 Rgeo E_Rad [0.036/8]? Upper uncertainty in Rad
119 A1 --- l_Mass Limit on Mass
121- 127 F7.2 Mgeo Mass [-4.2/1142] Mass
129- 133 F5.2 Mgeo e_Mass [0.37/45]? Lower uncertainty in Mass
135- 139 F5.2 Mgeo E_Mass [0.37/53]? Upper uncertainty in Mass
141 A1 --- l_rho Limit on rho
143- 148 F6.3 g/cm3 rho [-1.6/40]? Density
150- 155 F6.3 g/cm3 e_rho [0.013/10]? Lower uncertainty in rho
157- 162 F6.3 g/cm3 E_rho [0.016/12]? Upper uncertainty in rho
164- 169 F6.1 K Teq [186.1/2177]? Equilibrium temperature
171- 175 F5.1 K e_Teq [1/147.5]? Lower uncertainty in Teq
177- 181 F5.1 K E_Teq [3/147.5]? Upper uncertainty in Teq
183- 190 F8.3 Earth Flux [0.285/5300]? Instellation flux in units of Earth
flux
192- 198 F7.3 Earth e_Flux [0.02/600]? Lower uncertainty in Flux
200- 206 F7.3 Earth E_Flux [0.04/600]? Upper uncertainty in Flux
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Object name
16- 28 F13.5 d Time [2455198.5/2458309.1] Barycentric Julian date
30- 38 F9.2 m/s RV [-38039/76756] Radial velocity (1)
40- 44 F5.2 m/s e_RV [0.5/36] Uncertainty in RV
46- 50 F5.3 --- SHK [0/1.43]? S index (2)
52- 60 A9 --- Inst Instrument (3)
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Note (1): RV measurements from literature papers that we use in our analysis
are also given in this table. The references for each of these
points are given in the relevant subsection of Appendix A.
Note (2): Uncertainties are 0.002 for all Keck-HIRES measurements.
Note (3): Instrument as follows:
HIRES = Keck I HIRES (1988 occurrences)
APF = the Automated Planet Finder telescope (346 occurrences)
HARPS = ESO 3.6m telescope HARPS spectrograph (475 occurrences)
HARPS-N = TNG 3.6m telescope HARPS-N spectrograph (196 occurrences)
FIES = the 2.56m Nordic Optical Telescope FIbre-fed Echelle Spectrograph
(93 occurrences)
CORALIE = ESO 1.2m telescope CORALIE spectrograph (76 occurrences)
CARMENES = CAHA 3.5m telescope CARMENES spectrograph (58 occurrences)
PFS = Magellan 6.5m telescope Planet Finder Spectrograph (94 occurrences)
PARAS = the PRL optical fiber-fed high-resolution cross-dispersed echelle
spectrograph (PARAS) spectrograph mounted on a 1.2m telescope
at Gurushikhar Observatory, Mount Abu, India (19 occurrences)
CORPOST = CORALIE observations described in Section 2.1 of
Neveu-VanMalle+ 2016A&A...586A..93N 2016A&A...586A..93N (6 occurrences)
TULL = McDonald 2.7m telescope Tull Coude spectrograph (6 occurrences)
FIES-POST = (4 occurrences)
HDS = Subaru/High Dispersion Spectrograph (3 occurrences)
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History:
From electronic version of the journal
(End) Prepared by [AAS], Emmanuelle Perret [CDS] 19-Feb-2026