J/ApJ/778/132 C and O abundances in 55 Cnc (Teske+, 2013)
Carbon and oxygen abundances in cool metal-rich exoplanet hosts: a case study
of the C/O ratio of 55 Cancri.
Teske J.K., Cunha K., Schuler S.C., Griffith C.A., Smith V.V.
<Astrophys. J., 778, 132 (2013)>
=2013ApJ...778..132T 2013ApJ...778..132T
ADC_Keywords: Abundances ; Equivalent widths ; Stars, double and multiple
Keywords: planets and satellites: formation; stars: atmospheres ;
planets and satellites: individual: 55 Cnc; stars: abundances
Abstract:
The super-Earth exoplanet 55 Cnc e, the smallest member of a
five-planet system, has recently been observed to transit its host
star. The radius estimates from transit observations, coupled with
spectroscopic determinations of mass, provide constraints on its
interior composition. The composition of exoplanetary interiors and
atmospheres are particularly sensitive to elemental C/O ratio, which
to first order can be estimated from the host stars. Results from a
recent spectroscopic study analyzing the 6300Å[OI] line and two CI
lines suggest that 55 Cnc has a carbon-rich composition
(C/O=1.12±0.09). However, oxygen abundances derived using the
6300Å[OI] line are highly sensitive to a Ni I blend, particularly
in metal-rich stars such as 55 Cnc ([Fe/H]=0.34±0.18). Here, we
further investigate 55 Cnc's composition by deriving the carbon and
oxygen abundances from these and additional C and O absorption
features. We find that the measured C/O ratio depends on the oxygen
lines used. The C/O ratio that we derive based on the 6300Å[OI]
line alone is consistent with the previous value. Yet, our
investigation of additional abundance indicators results in a mean C/O
ratio of 0.78±0.08. The lower C/O ratio of 55 Cnc determined here
may place this system at the sensitive boundary between protoplanetary
disk compositions giving rise to planets with high (>0.8) versus low
(<0.8) C/O ratios. This study illustrates the caution that must
applied when determining planet host star C/O ratios, particularly in
cool, metal-rich stars.
Description:
We analyze Keck/HIRES archive spectra of 55 Cnc (PID H32bH; PI:
Shkolnik) taken across four nights in 2006 January, covering the
wavelength range 3360-8100Å. The 35 spectra combined yield a S/N of
∼1270 around the 6300Å[OI] line.
To enable differential abundance determinations relative to the Sun,
we also analyze three solar spectra of reflected light from Vesta (PID
N014Hr; PI: Marcy). These data were taken in 2006 April with the same
filter.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 54 1 *Derived stellar parameters and elemental
abundances for 55 Cnc
table2.dat 48 84 Lines Measured, Equivalent Widths, and Abundances
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Note on table1.dat: Adopted solar parameters: Teff=5777K, logg=4.44, and
ξ=1.38km/s.
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See also:
J/A+A/561/A36 : The LickX Spectra library (Worthey+, 2014)
J/ApJ/764/78 : Oxygen abundances in nearby FGK stars (Ramirez+, 2013)
J/A+A/547/A91 : Spectroscopic analysis of 348 red giants (Zielinski+, 2012)
J/A+A/545/A97 : 0.8-6µm calibrated spectrum of 55 Cnc (Crossfield, 2012)
J/A+A/539/A28 : New transit photometry for super-Earth 55Cnc e (Gillon+, 2012)
J/ApJ/759/19 : Precise radial velocities of ρ1 Cancri (Endl+, 2012)
J/ApJ/757/161 : Spectroscopy of 56 exoplanet host stars (Torres+, 2012)
J/A+A/533/A114 : Transit of super-Earth 55 Cnc e (Demory+, 2011)
J/A+A/525/A90 : Thick disc vertical properties (Katz+, 2011)
J/ApJ/736/87 : Abundances in G-type stars with exoplanets (Kang+, 2011)
J/ApJ/736/19 : Kepler planetary candidates. II. (Borucki+, 2011)
J/ApJ/735/41 : Carbon and oxygen abundances in FGK stars (Petigura+, 2011)
J/ApJ/732/55 : Abundances of stars with planets (Schuler+, 2011)
J/ApJ/725/2349 : C/O vs Mg/Si of planetary systems (Delgado Mena+, 2010)
J/ApJ/715/1050 : Predicted abundances for extrasolar planets. I. (Bond+, 2010)
J/A+A/508/1403 : Oxygen lines in solar granulation. II. (Pereira+, 2009)
J/ApJS/168/297 : Stellar parameters of nearby cool stars (Takeda+, 2007)
J/A+A/465/271 : Oxygen abundances in nearby stars (Ramirez+, 2007)
J/ApJ/646/505 : Catalog of nearby exoplanets (Butler+, 2006)
J/ApJ/634/1319 : Synthetic Lick indices (Franchini+ 2005)
J/ApJ/626/446 : Effective temperature scale of FGK stars (Ramirez+, 2005)
J/ApJ/622/1102 : The planet-metallicity correlation. (Fischer+, 2005)
J/A+A/433/185 : Detailed abundance analysis of F and G dwarfs (Bensby+, 2005)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/PASJ/57/65 : CNO abundances of solar-type stars (Takeda+, 2005)
J/A+A/420/183 : Spectroscopy in solar neighborhood (Allende Prieto+ 2004)
J/A+A/415/155 : Oxygen abundances in the Galactic disk (Bensby+, 2004)
J/A+A/414/351 : ELODIE survey for northern exoplanets III (Naef+, 2004)
J/A+A/402/343 : IR OI triplet, [O I] lines in F-K dwarfs/giants (Takeda, 2003)
J/A+A/350/955 : Atmospheric param. in metal-poor stars. II (Gratton+, 1999)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 4 I4 K Teff [5350] Effective temperature
6- 8 I3 K e_Teff [102] Teff uncertainty
10- 13 F4.2 [cm/s2] logg [4.44] Surface gravity
15- 18 F4.2 [cm/s2] e_logg [0.3] logg uncertainty
20- 23 F4.2 km/s Vt [1.17] Microturbulent velocity (ξ)
25- 28 F4.2 km/s e_Vt [0.14] Vt uncertainty
30- 33 F4.2 [Sun] [Fe/H] [0.34] Abundance [Fe/H]
35- 38 F4.2 [Sun] e_[Fe/H] [0.18] [Fe/H] uncertainty
40- 43 F4.2 [Sun] [Ni/H] [0.43] Abundance [Ni/H]
45- 48 F4.2 [Sun] e_[Ni/H] [0.05] [Ni/H] uncertainty
50- 54 A5 --- Name [55Cnc] Star name
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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- 5 A5 --- Ion Ion (C I, O I, Fe I or II, Ni I, or [O I])
7- 13 F7.2 0.1nm lambda [4779/7776] Wavelength in Angstroms
15- 18 F4.2 eV ExPot [0/9.2] Excitation potential χ
20- 25 F6.2 [-] log(gf) [-10.2/0.4] Log of the oscillator strength
27- 30 F4.1 10-13m EW0 Equivalent width in solar spectrum (mÅ)
32- 35 F4.2 [-] logN0 [6.1/8.9] Log of solar number abundance
36 A1 --- f_logN0 [a] Method used (1)
38- 42 F5.1 10-13m EW55 [3.4/104.2] Equivalent width in the 55 Cnc
spectrum (mÅ)
44- 47 F4.2 [-] logN55 [6.5/9.1] Log of 55 Cnc number abundance
48 A1 --- f_logN55 [ab] Method used (1)
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Note (1): Method used as follows:
a = Abundance derived through synthesis analysis.
b = LTE abundance.
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History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Emmanuelle Perret [CDS] 27-Apr-2015