Chemical Composition of Planet-Host Stars Wonseok Kang Kyung Hee University Sang-Gak Lee Seoul National University

Why? : Abundances of Planet Host Stars 2 Workshop on Stars, Planets, and Life 2013 Proto-planetary Disk Disk Properties Mass Temperature …… Chemical Abundances Extrasolar Planets Planet Occurrence Planet Properties Mass Semi-major Axis …… Planet Formation Process Chemical Abundances of Planet Host atmosphere Chemical Abundances of Planet Host atmosphere Planet Occurrence Planet Properties Planet Occurrence Planet Properties Observations Theories Planet Formation Theory Candidates of Planet Search Planet Formation Theory Candidates of Planet Search

1.Planet-Host Star (PHS) is metal-rich? – Core-accretion model – Gravitational instability in disk 3 Workshop on Stars, Planets, and Life 2013 Issues on PHS Abundances Core-accretion Model Amount of planetesimals depends on metallicity Gravitational instability Gravitational instability is less sensitive to metallicity

Planet-metallicity correlation ( observationally ) – The planet detectability is exponentially increasing with increasing metallicity (Fischer & Valenti 2005) using ~ 1000 stars of SPOCS catalog – Planet occurrence is correlated with stellar mass and metallicity (Johnson et al. 2010) using the data of SPOCS (+ M dwarfs and A dwarfs) Previous Studies – Metallicity 4 Workshop on Stars, Planets, and Life 2013 Chemical abundance vs. condensation temperature photospheric vs. meteoritic abundance for the Sun Slightly positive Δ[X/H]-T C slope (Gonzalez 2006) : photospheric abundance > meteoritic abundance for refractory elements. P ( planet ) = 0.03 × 10 2 [Fe/H] Fischer & Valenti 2005 Johnson et al f (M,F)=0.07 × (M/M ⊙ ) 1.0 × [Fe/H]

1.Why metal-rich? – Primordial metal-rich nebula  make more planets in stars – Stars with planets  rocky matrial engulfed into the atmosphere 5 Workshop on Stars, Planets, and Life 2013 Issues on PHS Abundances Enhancement of Both Volatiles & Refractories Less Volatiles, More Refractories Self-enrichment (Pollution) Hypothesis Primordial Hypothesis Metal-rich Planet Host Stars Metal-rich Planet Host Stars More Planetesimals Primordial High-metallicity Composition Accretion of Metal-rich Material Normal Composition Core-accretion Model → More Planets Migration of Planets and Planetesimals

Chemical abundance of PHSs – Bondaghee et al. (2003), Gilli et al. (2006), Neves et al. (2009) Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, Na, Mg, Al ; refractories – Ecuvillon et al. (2004, 2006) C, N, O, S, Zn ; volatiles Difference between volatile and refractory (pollution?) – Abundance difference between volatiles and refractories for planet host stars (Ecuvillon et al. 2006) CNO, S, Zn / Cu, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni, / Na, Mg, Al (from 6 references) 88 planet host stars and 33 comparison stars No difference more than the error of abundance analysis and the star-to-star scatter – Volatiles and refractories in solar analog (Gonzalez et al. 2010) 14 solar analogs with super-Earths and 14 “single” solar analogs Considering the galactic chemical evolution, difference in mean abundance disappears Previous Studies – Chemical Abundance 6 Workshop on Stars, Planets, and Life 2013

Samples – Planet-Host Stars (PHSs) Butler et al. (2006) and (Jean Schneider, 2010) F, G, K type stars with planet – Comparison stars Tycho-2 spectral type catalog (Wright et al. 2003) F, G, K type stars within 20 pc from the Sun, without known planets Observations ( 2007 ~ 2010 ) – BOES with BOAO 1.8-m telescope, in uniform way High-resolution echelle spectrograph – 166 stars : 93 PHSs (67 dwarfs) / 73 Comparison stars (68 dwarfs) – S/N ratio > 100 at 6070 Å – R = 30,000 or 45,000 STARS for Abundance Analysis 7 Workshop on Stars, Planets, and Life 2013

26 elements by EW measurement – CNO, α-elements, iron-peak elements, and neutron-capture elements – Line list Fe lines (VALD) verified with BOES solar spectrum C, N, O, K, Cu, Zn, Sr, Y, Zr, Ba, Ce, Nd, Eu (Reddy et al. 2003) Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Mn, Co, Ni (Neves et al. 2009) Sulfur by synthetic spectrum – Three multiplet lines near 6757 Å in optical (Caffau et al. 2005) located in the narrow range of 0.05 Å ELEMENTS for Abundance Analysis 8 Workshop on Stars, Planets, and Life 2013

How? : Abundance Analysis 9 Workshop on Stars, Planets, and Life 2013 Using Equivalent-Widths (EWs) Using Synthetic Spectrum Model Atmosphere EWs (elemental lines) MOOG code (Sneden, 2010) Model atmosphere Abundance MOOG code (Sneden, 2010) Synthetic Spectrum Observed spectrum Abundance Line Data (log gf, E.P.) Fine Analysis EWs (Fe lines) Fine Analysis EWs (Fe lines)

EW Measurement / Synthetic Spectrum 10 Workshop on Stars, Planets, and Life 2013 Color lines Blue : dex Red : best-fit Green : dex Black circles Observed Spectrum Wavelength S I ( MOOGSY) Ni I ( MOOGEL) HD

WHICH ELEMENT IS MOST ABUNDANT IN “PLANET”-HOST STARS? Mean abundance in planet-host stars

PHS - Comparison Abundance Difference on T C 12 Workshop on Stars, Planets, and Life 2013 Na Cu Mn MgCoNi AlSc Δ Ba NdK Solid line : Δ between PHSs and comparisons Dotted line : Δ = 0.13 ± 0.23 dex Shaded region : the standard deviation of [X/H] Volatile Zr Refractory C N OS Zn Fe

Manganese 13 Workshop on Stars, Planets, and Life 2013 Mn I (4) log ε ⊙ = 5.50 dex [X/Fe] [X/H] All stars follow the Galactic chemical evolution

Barium 14 Workshop on Stars, Planets, and Life 2013 Ba II (2) log ε ⊙ = 2.40 dex [X/Fe] [X/H]

PHSs are metal-rich Chemical evolution trend in high-[Fe/H] – If an element is more abundant in metal-rich stars, [X/H] of PHS is higher than [X/H] of normal star This is nothing more than a reflection of metal-rich PHS There is no evidence for pollution! 15 Workshop on Stars, Planets, and Life 2013 The Origin of [X/H] Difference DifferenceGalactic chemical evolutionMetal-rich PHS Less  More  Decreasing at [Fe/H] > 0 Increasing at [Fe/H] > 0 71 % of PHS in [Fe/H] > 0

WHICH ELEMENT IS SENSITIVE TO “PLANET” OCCURRENCE? Kolmogorov-Smirnov Test Proportion of PHS

Not volume-limited Not covering all nearby stars Not homogeneous Therefore, we performed K-S test – Shows only the degree of difference between two distributions Our Sample is …

Kolmogorov-Smirnov Test 18 Workshop on Stars, Planets, and Life 2013 Low probability from K-S test (< 0.02%) : C, O, Na, Mg, Ca, Al, Si, Zn The probability, that [X/H] distributions of two groups belong to the same population for each element Fe : 0.02% 50% Condensation temperature (Lodders 2003)

Not volume-limited Not covering all nearby stars Not homogeneous Therefore, we performed K-S test – Shows only the degree of difference between two distributions Nevertheless, we tried to find the relation between planet occurrence and chemical abundances, [X/H] – Shows the direction Our Sample is …

Histogram of [X/H] – In each bin of [X/H] ( bin size = 0.1 dex) – For each bin, Probability function of planet occurrence Proportion of PHS for [X/H] 20 Workshop on Stars, Planets, and Life 2013 α : the proportion at the solar abundance, at [X/H] = 0 β : increasing trend coefficient

Proportion of PHS for [X/H] 21 Workshop on Stars, Planets, and Life 2013 Histogram - Planet host star - Comparison star

SiC Proportion of PHS for [X/H] 22 Workshop on Stars, Planets, and Life 2013 OMgZnCaTi Cr β [X/H] > β [Fe/H] Dotted line :  [Fe/H] = 0.77 Error bar : fitting error of  β coefficient for each element Probability more steeply increase with increasing abundances of C, O, Mg, Si, Ca, Ti, Cr, Zn, relative to [Fe/H]

No significant difference between volatiles and refractories – Considering the galactic chemical evolution The elements from K-S test – Low probability that the distributions of two groups belong to the same population >> C, O, Na, Mg, Al, Ca, Si, Zn ( < 0.02 %, Fe) The elements from the proportion of PHS – β [X/H] > β [Fe/H] >> C, O, Mg, Si, Ca, Ti, Cr, Zn Summary 23 Workshop on Stars, Planets, and Life 2013 C, O, Mg, Si, Ca, Zn Sensitive to Planet occurrence No evidence for “pollution hypothesis”

THANK YOU 감사합니다 24Workshop on Stars, Planets, and Life 2013