The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets BJ Fulton, Erik Petigura, Andrew Howard, Howard Isaacson, Geoffrey Marcy, Phillip Cargile, Leslie Hebb, Lauren Weiss, John Johnson, Tim Morton, Evan Sinukoff, Ian Crossfield, and Lea Hirsch Petigura, Howard, et al. (2017) CKS I: Spectroscopic Properties of 1305 Planet-Host Stars From Kepler Johnson, Petigura, Fulton et al. (2017) CKS II: Precise Physical Properties of 2025 Kepler Planets and Their Host Stars
85 Earths Super- Earths Small Neptunes Large Neptunes Giant Planets 1.0 1.4 2.0 2.8 4.0 5.7 8.0 11.3 16.0 22.6 Earth Fressin et al. (2013) Petigura et al. (2013) Features in the radius distribution smeared out due to 40% radius errors BJ Fulton Know Thy Star 2017
The California- Kepler Survey Led by Andrew Howard, Geoff Marcy, John Johnson ~50 Keck nights (2011-2015) HIRES spectra of 1305 stars hosting 2025 planet candidates Sub-samples: Magnitude limited (Kp < 14.2) (N = 960) Multis (N = 484) USPs (P < 1d) (N = 71) Number of Stars Number of Stars 250 200 150 100 50 0 1000 800 600 400 200 0 8 10 12 14 16 Kp [mag] 821 297 116 49 18 2 2 1 2 3 4 5 6 7 Planets per Star Habitable Zone (N = 127) Petigura, Howard, et al. (2017) BJ Fulton Know Thy Star 2017
High resolution: R ~ 50,000 Enables measurement of vsini All spectra and parameters are public astro.caltech.edu/~howard/cks High SNR Precision spectroscopy Searches for faint SB2 Petigura, Howard et al. (2017) BJ Fulton Know Thy Star 2017
The California-Kepler Survey σteff (Q16) = 156 K σteff (CKS) = 60 K σlogg (Q16) = 0.17 dex σlogg (CKS) = 0.07 dex σm/m (Q16) = 14% σm/m (CKS) = 5% σr/r (Q16) = 39% σr/r (CKS) = 10% BJ Fulton Know Thy Star 2017
X = RP/R R RP X = Transit Depth Q16 Stellar Radii Q16 CKS Planet Radii Q16 CKS BJ Fulton Know Thy Star 2017 Johnson, Petigura, Fulton et al. (2017); Fulton, Petigura, et al. (2017)
Owen & Wu (2013) Huber et al. (2014); Mullally et al. (2015) Johnson, Petigura, et al. (2017) BJ Fulton Know Thy Star 2017
The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017
The Radius Gap super-earths and sub-neptunes are ~equally common Super- Earths Sub- Neptunes BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017
The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017
The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017
The Radius Gap USPs (P < 1 d) BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017
Flux Dependency Hot Sub-Neptune Desert Radius Gap low completeness Fulton, Petigura, et al. (2017)
Flux Dependency n Rocky Super-Earths 3 senutpeand N-buGaseous S suoesasub-neptunes G dna shtrae-rep3us ykcor 4.0 Planet Size 3.5 3.0 2.5 2.0 Radius 1.5 Gap low completeness 1.0 1000 100 Incident Flux (Earth-units) Figure from Lopez+16; see also Owen+13, Fulton, Petigura, Lopez+13, etjin+14, al. (2017) Chen+16 10
Photo-Evaporation Causes Gap Predicted by Theory Owen & Wu (2013) Lopez & Fortney (2013) Jin et al. (2014) Chen & Rogers (2016) Explanation High energy XUV photons emitted during star s first 100 Myr erodes envelopes Most sub-neptunes are ~3% H/He by mass 3% H/He envelopes have longest mass loss timescale Planets are herded into two typical sizes Owen and Wu (2017)
XUV photons 20% H/He ~3% H/He ~3 Me Core Oewn & Wu (2017)
XUV photons ~0.3% H/He 0% H/He ~3 Me Core ~3 Me Core Oewn & Wu (2017)
Photoevaporation Owen & Wu (2017) BJ Fulton ExSoCal 2017
Photoevaporation Fulton, Petigura, et al. (2017) Observations Major Implications Maximum core size ~3 Me Earth-like composition (water-poor) Planet Size [Earth radii] 3.5 2.4 1.5 Model 1.0 0.8 0.6 0.4 0.2 Normalised Planet Density Large scale migration after 100 Myr is uncommon 1 3000 1000 300 100 Owen & Wu (2017) 30 10 0.0 BJ Fulton Know Thy Star 2017
Summary Precision spectroscopy for 2025 KOIs Fulton, Petigura, et al. (2017) Gap in the radius distribution between 1.5 2.0 Re Two size classes for small planets Small, close-in planets are composed of rocky cores with varying amounts of low-density gas BJ Fulton ExSoCal 2017
Backup Slides
Completeness Corrections m i = RP R?,i 1 w i = (p det p tr ) 2 r Tobs,i P + 1 CDPP dur,i = BJ Fulton Fulton, Petigura, et al. (submitted) Aspen 2017
Completeness Corrections w i = 1 (p det p tr ) p tr =0.7R? /a + = BJ Fulton Fulton, Petigura, et al. (submitted) Aspen 2017
Completeness Corrections w i = 1 (p det p tr ) Number of Planets per Star = f bin = 1 n X pl,bin N? i=1 w i (x) = 1 n X pl N? i=1 w i K(x x i, x,i) BJ Fulton Fulton, Petigura, et al. (submitted) Aspen 2017
Magnitude Cuts Consistent (97% confidence) Not consistent
Lopez et al. (2014) BJ Fulton Aspen 2017
Previous Occurrence Studies Howard et al. (2012) Planet Occurrence Within 0.25 AU of Solar-Type Stars from Kepler Petigura et al. (2013) Prevalence of Earth-size planets orbiting Sun-like stars Morton et al. (2014) The Radius Distribution of Planets Around Cool Stars Owen & Wu (2014) Kepler Planets: A Tale of Evaporation
The California-Kepler Survey Keck/HIRES spectra for 1305 Kepler Objects of Interest Q1-Q16 KOI Catalog California-Kepler Survey (CKS) 6263 K 6001 K 5823 K Normalized Flux 5632 K 5442 K 5236 K 4994 K 4788 K 5160 5170 5180 5190 5200 Wavelength [Ang]
Adding an Atmosphere + 20% H/He 1.0 g cm -3 Adams et al. (2008) + 2% H/He 3.4 g cm -3 + 0.2% H/He 0.3/0.7 Fe/MgSiO3 6 g cm -3 8 g cm -3 Planet inflation depends on: Mcore, Teff, internal heat sources