J/ApJ/875/29 Spectroscopic analysis of the CKS sample. I. (Martinez+, 2019) ================================================================================ A spectroscopic analysis of the California-Kepler Survey sample. I. Stellar parameters, planetary radii, and a slope in the radius gap. Martinez C.F., Cunha K., Ghezzi L., Smith V.V. =2019ApJ...875...29M ================================================================================ ADC_Keywords: Spectra, optical; Stars, diameters; Effective temperatures; Exoplanets Keywords: planetary systems ; stars: fundamental parameters ; techniques: spectroscopic Abstract: We present results from a quantitative spectroscopic analysis conducted on archival Keck/HIRES high-resolution spectra from the California-Kepler Survey (CKS) sample of transiting planetary host stars identified from the Kepler mission. The spectroscopic analysis was based on a carefully selected set of FeI and FeII lines, resulting in precise values for the stellar parameters of effective temperature (Teff) and surface gravity (logg). Combining the stellar parameters with Gaia DR2 parallaxes and precise distances, we derived both stellar and planetary radii for our sample, with a median internal uncertainty of 2.8% in the stellar radii and 3.7% in the planetary radii. An investigation into the distribution of planetary radii confirmed the bimodal nature of this distribution for the small-radius planets found in previous studies, with peaks at ~1.47+/-0.05 and ~2.72+/-0.10R_{Earth}_ with a gap at ~1.9R_{Earth}_. Previous studies that modeled planetary formation that is dominated by photoevaporation predicted this bimodal radii distribution and the presence of a radius gap, or photoevaporation valley. Our results are in overall agreement with these models, as well as core powered mass-loss models. The high internal precision achieved here in the derived planetary radii clearly reveal the presence of a slope in the photoevaporation valley for the CKS sample, indicating that the position of the radius gap decreases with orbital period; this decrease was fit by a power law of the form R_pl_{propto}P^-0.11^, which is consistent with both photoevaporation and core powered mass-loss models of planet formation, with Earth-like core compositions. Description: The high-resolution spectra analyzed in this study were obtained as part of the California-Kepler Survey (CKS; Fulton+ 2017, J/AJ/154/109; Johnson+ 2017, J/AJ/154/108; Petigura+ 2017, J/AJ/154/107), a large observational campaign targeting stars identified as Kepler objects of interest (KOIs). The CKS campaign was conducted between 2012 and 2014 using HIRES at the Keck telescope. All CKS spectra analyzed here were reduced by Petigura+ (2017, J/AJ/154/107) and are publicly available in the Keck Observatory Archive. File Summary: -------------------------------------------------------------------------------- FileName Lrecl Records Explanations -------------------------------------------------------------------------------- ReadMe 80 . This file table1.dat 57 1285 Stellar parameters and radii table2.dat 25 1633 Planetary radii -------------------------------------------------------------------------------- See also: VI/120 : High-resolution synthetic stellar library (Coelho+, 2005) V/133 : Kepler Input Catalog (Kepler Mission Team, 2009) I/347 : Distances to 1.33 billion stars in Gaia DR2 (Bailer-Jones+, 2018) I/345 : Gaia DR2 (Gaia Collaboration, 2018) J/MNRAS/384/1178 : 2MASS, SDSS and BVRI photometry for 825 stars (Bilir+, 2008) J/other/Nat/486.375 : Stellar parameters of KOI stars (Buchhave+, 2012) J/ApJ/763/41 : Kepler multiple-candidate systems radii (Ciardi+, 2013) J/ApJ/767/95 : Improved parameters of smallest KIC stars (Dressing+, 2013) J/ApJ/771/107 : Spectroscopy of faint KOI stars (Everett+, 2013) J/ApJS/210/1 : Asteroseismic study of solar-type stars (Chaplin+, 2014) J/ApJS/211/2 : Revised properties of Q1-16 Kepler targets (Huber+, 2014) J/ApJ/810/95 : Kepler pipeline S/N studies. II. 2011 (Christiansen+, 2015) J/ApJ/799/180 : Radii of KOI Earth to Neptune-sized planets (Silburt+, 2015) J/MNRAS/452/2127 : Fundamental param. of Kepler stars (Silva Aguirre+, 2015) J/ApJS/225/32 : Extended abundance analysis of cool stars (Brewer+, 2016) J/ApJ/828/99 : Kepler pipeline signal recovery. III. (Christiansen+, 2016) J/AJ/151/144 : ASPCAP weights for APOGEE chemical elements (Garcia+, 2016) J/AJ/152/187 : Stellar metallicity for KOIs (Mulders+, 2016) J/AJ/154/109 : California-Kepler Survey. III. Planet radii (Fulton+, 2017) J/ApJ/844/102 : KIC star plx from asteroseismology vs Gaia (Huber+, 2017) J/AJ/154/108 : California-Kepler Survey (CKS). II. (Johnson+, 2017) J/AJ/154/107 : California-Kepler Survey (CKS). I. (Petigura+, 2017) J/ApJS/233/23 : APOKASC cat. of KIC dwarfs and subgiants (Serenelli+, 2017) J/AJ/153/136 : Planets & host stars with Gaia parallaxes (Stassun+, 2017) J/ApJ/866/99 : Radii of KIC stars & planets using Gaia DR2 (Berger+, 2018) J/ApJS/237/38 : Extended abundance analysis of KOIs (Brewer+, 2018) J/AJ/156/264 : CKS. VII. Planet radius gap (Fulton+, 2018) J/ApJ/860/109 : Keck HIRES obs. of subgiants (Ghezzi+, 2018) J/AJ/156/126 : Stellar param. & abund. from BACCHUS (Jonsson+, 2018) J/ApJS/239/32 : APOKASC-2 cat. of Kepler evolved stars (Pinsonneault+, 2018) J/ApJS/235/38 : Kepler planetary candidates. VIII. DR25 (Thompson+, 2018) http://california-planet-search.github.io/cks-website/ : The CKS home page Byte-by-byte Description of file: table1.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Seq [1/1285] Internal index number 6- 16 A11 --- Name Kepler Object Identifer (K-NNNNN; in Simbad or KIC identifier) 18- 21 I4 K Teff [4559/6676] Effective temperature 23- 25 I3 K e_Teff [11/311] Uncertainty in Teff 27- 30 F4.2 [cm/s2] log(g) [2.5/5] log surface gravity 32- 35 F4.2 [cm/s2] e_log(g) [0.01/0.4] Uncertainty in log(g) 37- 40 F4.2 km/s Vturb [0.2/4.8] Microturbulent velocity 42- 45 F4.2 km/s e_Vturb [0.02/2.1] Uncertainty in Vtrub 47- 51 F5.2 Rsun R* [0.4/16.3]? Stellar radius 53- 57 F5.2 Rsun e_R* [0.01/35]? Uncertainty in R* -------------------------------------------------------------------------------- Byte-by-byte Description of file: table2.dat -------------------------------------------------------------------------------- Bytes Format Units Label Explanations -------------------------------------------------------------------------------- 1- 4 I4 --- Seq [1/1633] Internal index number 6- 14 A9 --- KOI Planet identifier (KNNNNN.NN; in Simbad) 16- 20 F5.2 Rgeo Rp [0.38/63] Planetary radius 22- 25 F4.2 Rgeo e_Rp [0.02/4]? Uncertainty in Rp -------------------------------------------------------------------------------- History: From electronic version of the journal ================================================================================ (End) Prepared by [AAS], Emmanuelle Perret [CDS] 02-Sep-2020