J/AJ/145/52 Abundances of late K and M dwarfs in binary systems (Mann+, 2013)
Prospecting in late-type dwarfs: a calibration of infrared and visible
spectroscopic metallicities of late K and M dwarfs spanning 1.5 dex.
Mann A.W., Brewer J.M., Gaidos E., Lepine S., Hilton E.J.
<Astron. J., 145, 52 (2013)>
=2013AJ....145...52M 2013AJ....145...52M
ADC_Keywords: Stars, F-type ; Stars, G-type ; Stars, K-type ; Stars, M-type ;
Spectral types ; Effective temperatures ; Abundances
Keywords: binaries: visual - stars: abundances - stars: fundamental parameters -
stars: late-type - techniques: spectroscopic
Abstract:
Knowledge of late K and M dwarf metallicities can be used to guide
planet searches and constrain planet formation models. However, the
determination of metallicities of late-type stars is difficult because
visible wavelength spectra of their cool atmospheres contain many
overlapping absorption lines, preventing the measurement of equivalent
widths. We present new methods, and improved calibrations of existing
methods, to determine metallicities of late K and M dwarfs from
moderate resolution (1300<R<2000) visible and infrared spectra. We
select a sample of 112 wide binary systems that contain a late-type
companion to a solar-type primary star. Our sample includes 62 primary
stars with previously published metallicities, as well as 50 stars
with metallicities determined from our own observations. We use our
sample to empirically determine which features in the spectrum of the
companion are best correlated with the metallicity of the primary. We
find ∼120 features in K and M dwarf spectra that are useful for
predicting metallicity. We derive metallicity calibrations for
different wavelength ranges, and show that it is possible to get
metallicities reliable to <0.10dex using either visible, J-, H-, or
K-band spectra. We find that the most accurate metallicities derived
from visible spectra requires the use of different calibrations for
early-type (K5.5-M2) and late-type (M2-M6) dwarfs. Our calibrations
are applicable to dwarfs with metallicities of -1.04<[Fe/H]<+0.56 and
spectral types from K7 to M5. Lastly, we use our sample of wide
binaries to test and refine existing calibrations to determine M dwarf
metallicities. We find that the ζ parameter, which measures the
ratio of TiO can CaH bands, is correlated with [Fe/H] for super-solar
metallicities, and ζ does not always correctly identify
metal-poor M dwarfs. We also find that existing calibrations in the K
and H bands are quite reliable for stars with [Fe/H]>-0.5, but are
less useful for more metal-poor stars.
Description:
Between 2011 January and 2012 April, 60 F-, G- and early K-type stars
were observed using the ESPaDOnS (Echelle SpectroPolarimetric Device
for the Observation of Stars) spectrograph attached to the
Canada-France-Hawaii Telescope (CFHT) on Mauna Kea. Observations were
taken in the star+sky mode, which gave a resolution of R∼65000 and a
wavelength range from 0.37µm to 1.05µm. All observations were
designed to achieve a signal-to-noise ratio (S/N) of >100 at
0.67µm, and typical S/N was >150 (per resolving element).
We obtained near-infrared spectra of our sample of companions using
the SpeX spectrograph attached to the NASA Infrared Telescope Facility
(IRTF) on Mauna Kea. SpeX observations were taken in the short
cross-dispersed (SXD) mode using the 0.3"*15" slit, yielding
simultaneous coverage from 0.8 to 2.4µm and a resolution of R∼2000.
We obtained a visible spectrum of each companion with the SuperNova
Integral Field Spectrograph (SNIFS) on the University of Hawaii 2.2m
telescope atop Mauna Kea. SNIFS has R∼1300 and splits the signal with
a dichroic mirror into blue (0.32-0.52µm) and red (0.52-0.95µm)
channels.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table1.dat 88 112 Wide binary sample
table2.dat 113 50 Parameters of primary stars observed at
Canada-France-Hawaii Telescope (CFHT)
table5.dat 43 111 Metal-sensitive features in the near-IR spectrum
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See also:
B/pastel : The PASTEL catalogue (Soubiran+, 2010-)
I/317 : The PPMXL Catalog (Roeser+ 2010)
I/311 : Hipparcos, the New Reduction (van Leeuwen, 2007)
I/298 : LSPM-North Catalog (Lepine+ 2005)
I/239 : The Hipparcos and Tycho Catalogues (ESA 1997)
J/AJ/144/102 : Cat. of wide companions to Hipparcos stars (Tokovinin+, 2012)
J/AJ/143/67 : SLoWPoKES. II. Properties of wide, low-mass binaries
(Dhital+, 2012)
J/ApJ/753/90 : Stellar paramet. of K5 & later type Kepler stars (Mann+, 2012)
J/ApJ/748/93 : K-band spectra for 133 nearby M dwarfs (Rojas-Ayala+, 2012)
J/AJ/142/138 : All-sky catalog of bright M dwarfs (Lepine+, 2011)
J/A+A/526/A71 : C abundances in G and K nearby stars (Da Silva+, 2011)
J/A+A/533/A141 : Stellar parameters for 582 HARPS FGK stars (Sousa+, 2011)
J/AJ/139/2566 : SLoWPoKES catalog (Dhital+, 2010)
J/PASP/121/117 : Fe & Ti abundance of 12 low-metallicity M stars (Woolf+, 2009)
J/AJ/133/889 : Faint companions of Hipparcos stars (Lepine+, 2007)
J/ApJS/169/430 : Atmospheric parame. of 1907 metal-rich stars (Robinson+, 2007)
J/ApJS/159/141 : Spectroscopic properties of cool stars. I. (Valenti+, 2005)
J/PASJ/57/27 : Atmospheric parameters of nearby F-K stars (Takeda+, 2005)
J/ApJS/150/455 : New HIP-based parallaxes for 424 faint stars (Gould+, 2004)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 14 A14 --- Name Name of the companion star (late K or M dwarf)
16- 23 F8.4 deg RAdeg Right Ascension in decimal degrees (J2000)
25- 32 F8.4 deg DEdeg Declination in decimal degrees (J2000)
34- 37 A4 --- SpT Spectral type of the companion star (1)
39- 41 A3 --- --- [HIP]
43- 56 A14 --- HIP Identifier of the primary (F, G, or K star) (G1)
58- 62 F5.2 [Sun] [Fe/H] The [Fe/H] metallicity of the primary (2)
64- 67 F4.2 [Sun] e_[Fe/H] Uncertainty in [Fe/H]
69- 72 A4 --- r_[Fe/H] Reference for [Fe/H] (3)
74- 78 F5.2 [Sun] [M/H] ? Metallicity of the primary (2)
80- 83 F4.2 [Sun] e_[M/H] ? Uncertainty in [M/H]
85- 88 A4 --- r_[M/H] Reference for [M/H] (3)
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Note (1): Derived from TiO and CaH indices (Lepine et al., 2013AJ....145..102L 2013AJ....145..102L).
Continuous spectral types (to 0.1) are used for plotting/binning/calculations,
even though spectral types are only accurate to ±0.2 (and by convention
should be rounded to the nearest 0.5).
Note (2): Includes our applied corrections (see Section 4.1).
Note (3): Note that all metallicities sources are from high-resolution spectra,
with the exception of Ro07, which uses moderate-resolution spectra, and C11,
which uses Stromgren photometry. References as follows:
C01 = Cayrel de Strobel et al. (2001, cat. III/221; obsoleted by B/pastel);
M04 = Mishenina et al. (2004, cat. J/A+A/418/551);
LH05 = Luck & Heiter (2005, cat. J/AJ/129/1063);
VF05 = Valenti & Fischer (2005, cat. J/ApJS/159/141);
T05 = Takeda et al. (2005, cat. J/PASJ/57/27);
B06 = Bean et al. (2006ApJ...652.1604B 2006ApJ...652.1604B);
Ra07 = Ramirez et al. (2007, cat. J/A+A/465/271);
Ro07 = Robinson et al. (2007, cat. J/ApJS/169/430);
F08 = Fuhrmann (2008MNRAS.384..173F 2008MNRAS.384..173F);
S11 = da Silva et al. (2011, cat. J/A+A/526/A71);
C11 = Casagrande et al. (2011, cat. J/A+A/530/A138);
N12 = Neves et al. (2012A&A...538A..25N 2012A&A...538A..25N);
TW = This work: analysis of the spectra from the ESPaDOnS (Echelle
SpectroPolarimetric Device for the Observation of Stars) spectrograph
attached to the Canada-France-Hawaii Telescope (CFHT) on Mauna Kea.
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Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 3 A3 --- --- [HIP]
5- 18 A14 --- HIP Identifier of primary (F, G, or K star) (G1)
20- 23 I4 K Teff Effective temperature
25- 26 I2 K e_Teff Error in Teff
28- 31 F4.2 [cm/s2] logg Surface gravity
33- 36 F4.2 [cm/s2] e_logg Error in logg
38- 42 F5.2 [Sun] [Fe/H] The [Fe/H] metallicity
44- 47 F4.2 [Sun] e_[Fe/H] Error in [Fe/H]
49- 53 F5.2 [Sun] [M/H] Metallicity
55- 58 F4.2 [Sun] e_[M/H] Error in [M/H]
60- 64 F5.2 [Sun] [Na/H] Abundance of Na
66- 69 F4.2 [Sun] e_[Na/H] Error in [Na/H]
71- 75 F5.2 [Sun] [Ti/H] Abundance of Ti
77- 80 F4.2 [Sun] e_[Ti/H] Error in [Ti/H]
82- 86 F5.2 [Sun] [Si/H] Abundance of Si
88- 91 F4.2 [Sun] e_[Si/H] Error in [Si/H]
93- 97 F5.2 [Sun] [Ni/H] Abundance of Ni
99-102 F4.2 [Sun] e_[Ni/H] Error in [Ni/H]
104-107 F4.1 --- chi2 Reduced χ2 (1)
109-113 A5 --- Run Run type (ITER or VESTA) (2)
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Note (1): Our final model parameters are χ2-weighted averages of 3 runs.
Note (2): Run type as follows:
ITER = parameters determined using Hipparcos parallaxes and Yonsei-Yale (Y2)
isochrones (Demarque et al., 2004ApJS..155..667D 2004ApJS..155..667D).
VESTA = parameters determined using classical SME (Spectroscopy Made Easy)
fitting (no parallax information included) with a correction using
Vesta as described in Valenti & Fischer (2005, cat. J/ApJS/159/141).
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Byte-by-byte Description of file: table5.dat
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Bytes Format Units Label Explanations
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1 A1 --- --- [F]
2- 3 I2 --- F [1/22]? Feature number (1)
5- 10 F6.4 um lambda [0.398/2.3844] Center wavelength (2)
12- 13 I2 0.1nm W [20/98] Feature width; in Å (3)
15- 18 F4.2 --- r1 [0.1/0.86]? Correlation coefficient for all
dwarfs (K5.5-M6.0), [Fe/H] (4)
20- 23 F4.2 --- r2 [0.19/0.89]? Correlation coefficient for
early-type dwarfs (K5.5-M2.0), [Fe/H] (4)
25- 28 F4.2 --- r3 [0.18/0.83]? Correlation coefficient for
late-type dwarfs (M2.0-M6.0), [Fe/H] (4)
30- 33 F4.2 --- r4 [0.1/0.78]? Correlation coefficient for all
dwarfs (K5.5-M6.0), [M/H] (4)
35- 38 F4.2 --- r5 [0.2/0.86]? Correlation coefficient for
early-type dwarfs (K5.5-M2.0), [M/H] (4)
40- 43 F4.2 --- r6 [0.18/0.68]? Correlation coefficient for
late-type dwarfs (M2.0-M6.0), [M/H] (4)
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Note (1): In total we find ∼120 features in K and M dwarf (companion star)
spectra that are statistically significant predictors of primary star
metallicity, although only ∼20 of these features are used in our final
calibrations. Some features may not correspond to any one specific element
or molecule, but simply to a region of the spectrum that undergoes overall
changes as a function of the metallicity of the star (see Section 6 for
further details).
Note (2): A center wavelength is selected, starting at the blue end of the
spectrum (∼0.33µm) and ending at the red end (∼2.4µm).
See Section 5 for more details.
Note (3): For each feature center, we select a feature width starting at 20Å.
We use an upper limit of 100Å (see Section 5 for more details).
Note (4): The adjusted square of the multiple correlation coefficient (Rap2)
as defined in Equation (6). A blank denotes that the feature did not have
an Rap2 value above the Rrand2 value (the 99.9% highest Rap2
value from the randomly assigned metallicities), and thus is not
considered a statistically significant metal-sensitive feature.
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Global notes:
Note (G1): HIP number (with the exception of three NLTT and two PM designation).
History:
From electronic version of the journal
(End) Greg Schwarz [AAS], Sylvain Guehenneux [CDS] 25-Mar-2014