The California-Kepler Survey. III. A Gap in the Radius Distribution of Small Planets

Transcription

1 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

2 85 Earths Super- Earths Small Neptunes Large Neptunes Giant Planets 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

3 The California- Kepler Survey Led by Andrew Howard, Geoff Marcy, John Johnson ~50 Keck nights ( ) 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 Kp [mag] Planets per Star Habitable Zone (N = 127) Petigura, Howard, et al. (2017) BJ Fulton Know Thy Star 2017

4 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

5 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

6 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)

7 Owen & Wu (2013) Huber et al. (2014); Mullally et al. (2015) Johnson, Petigura, et al. (2017) BJ Fulton Know Thy Star 2017

8 The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017

9 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

10 The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017

11 The Radius Gap BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017

12 The Radius Gap USPs (P < 1 d) BJ Fulton Fulton, Petigura, et al. (2017) Know Thy Star 2017

13 Flux Dependency Hot Sub-Neptune Desert Radius Gap low completeness Fulton, Petigura, et al. (2017)

14 Flux Dependency n Rocky Super-Earths 3 senutpeand N-buGaseous S suoesasub-neptunes G dna shtrae-rep3us ykcor 4.0 Planet Size Radius 1.5 Gap low completeness Incident Flux (Earth-units) Figure from Lopez+16; see also Owen+13, Fulton, Petigura, Lopez+13, etjin+14, al. (2017) Chen+16 10

15 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)

16 XUV photons 20% H/He ~3% H/He ~3 Me Core Oewn & Wu (2017)

17 XUV photons ~0.3% H/He 0% H/He ~3 Me Core ~3 Me Core Oewn & Wu (2017)

18 Photoevaporation Owen & Wu (2017) BJ Fulton ExSoCal 2017

19 Photoevaporation Fulton, Petigura, et al. (2017) Observations Major Implications Maximum core size ~3 Me Earth-like composition (water-poor) Planet Size [Earth radii] Model Normalised Planet Density Large scale migration after 100 Myr is uncommon Owen & Wu (2017) BJ Fulton Know Thy Star 2017

20 Summary Precision spectroscopy for 2025 KOIs Fulton, Petigura, et al. (2017) Gap in the radius distribution between 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

21 Backup Slides

22 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

23 Completeness Corrections w i = 1 (p det p tr ) p tr =0.7R? /a + = BJ Fulton Fulton, Petigura, et al. (submitted) Aspen 2017

24 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

25 Magnitude Cuts Consistent (97% confidence) Not consistent

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27 Lopez et al. (2014) BJ Fulton Aspen 2017

28 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

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33 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 Wavelength [Ang]

34 Adding an Atmosphere + 20% H/He 1.0 g cm -3 Adams et al. (2008) + 2% H/He 3.4 g cm % 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