J/ApJ/752/72 Correlation metallicity / eclipse depth (Dodson-Robinson, 2012)
A correlation between the eclipse depths of Kepler gas giant candidates
and the metallicities of their parent stars.
Dodson-Robinson S.E.
<Astrophys. J., 752, 72 (2012)>
=2012ApJ...752...72D 2012ApJ...752...72D
ADC_Keywords: Abundances ; Stars, double and multiple ; Planets ;
Stars, diameters
Keywords: planetary systems; planets and satellites: composition;
planets and satellites: formation;
planets and satellites: fundamental parameters
Abstract:
Previous studies of the interior structure of transiting exoplanets
have shown that the heavy-element content of gas giants increases with
host star metallicity. Since metal-poor planets are less dense and
have larger radii than metal-rich planets of the same mass, one might
expect that metal-poor stars host a higher proportion of gas giants
with large radii than metal-rich stars. Here I present evidence for a
negative correlation at the 2.3σ level between eclipse depth and
stellar metallicity in the Kepler gas giant candidates. Based on
Kendall's τ statistics, the probability that eclipse depth depends
on star metallicity is 0.981. The correlation is consistent with
planets orbiting low-metallicity stars being, on average, larger in
comparison with their host stars than planets orbiting metal-rich
stars. Furthermore, since metal-rich stars have smaller radii than
metal-poor stars of the same mass and age, a uniform population of
planets should show a rise in median eclipse depth with [M/H]. The
fact that I find the opposite trend indicates that substantial changes
in the gas giant interior structure must accompany increasing [M/H]. I
investigate whether the known scarcity of giant planets orbiting
low-mass stars could masquerade as an eclipse depth-metallicity
correlation, given the degeneracy between metallicity and temperature
for cool stars in the Kepler Input Catalog. While the eclipse
depth-metallicity correlation is not yet on firm statistical footing
and will require spectroscopic [Fe/H] measurements for validation, it
is an intriguing window into how the interior structure of planets and
even the planet formation mechanism may be changing with Galactic
chemical evolution.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 37 213 Giant planet candidates used in analysis
table2.dat 73 28 Kepler discoveries used for metallicity
accuracy analysis
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See also:
V/133 : Kepler Input Catalog (Kepler Mission Team, 2009)
J/A+A/557/A70 : Evolved planet hosts - stellar parameters (Mortier+, 2013)
J/A+A/551/A112 : Metallicity-giant planet correlation (Mortier+, 2013)
J/ApJ/750/114 : Kepler TTVs. IV. 4 multiple-planet systems (Fabrycky+, 2012)
J/ApJ/750/113 : TTVs from Kepler. II. 2 multiplanet systems (Ford+, 2012)
J/MNRAS/421/2342 : 4 Kepler systems transit timing obs. (Steffen+, 2012)
J/other/Nat/481.475 : RVs of Kepler-34b + Kepler-35b (Welsh+, 2012)
J/AJ/143/39 : Analysis of hot Jupiters in Kepler Q2 (Coughlin+, 2012)
J/ApJ/738/170 : False positive Kepler planet candidates (Morton+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/ApJ/697/544 : Planets orbiting metal-poor dwarfs. II. (Sozzetti+, 2009)
J/PASJ/57/109 : Late-G giants abundances (Takeda+, 2005)
J/A+A/438/251 : Abundances in stars with giant planets (Beirao+, 2005)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [K]
2- 9 F08.2 --- KOI [5/1587.01] Planet candidate KOI number
11- 18 I8 --- KIC KIC number of the host star
20- 24 F5.3 --- Rp/R* [0.01/0.3] Planet/star radius ratio
26- 31 F6.4 --- e_Rp/R* [0/0.1]? Rp/R* uncertainty
33- 37 F5.2 [Sun] [M/H] [-1.6/0.6] Host star [M/H]
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 16 A16 --- Name Star name (Kepler, KOI, or TrES)
18- 25 I8 --- KIC KIC number (1)
27- 31 F5.2 [Sun] [Fe/H] [-0.4/0.5] Spectroscopic [Fe/H]
33- 37 F5.3 [Sun] e_[Fe/H] [0.02/0.2] [Fe/H] uncertainty
39- 53 A15 --- Aut Author's name of [Fe/H] reference
55- 73 A19 --- BibCode Bibcode of [Fe/H] reference
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Note (1): KIC number 5794249 is very likely a misprint for 5794240;
corrected at CDS.
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History:
From electronic version of the journal
(End) Emmanuelle Perret [CDS] 04-Feb-2014