J/A+A/577/A132 Stellar parameters of early M dwarfs (Maldonado+, 2015)
Stellar parameters of early M dwarfs from ratios of spectral features at
optical wavelengths.
Maldonado J., Affer L., Micela G., Scandariato G., Damasso M., Stelzer B.,
Barbieri M., Bedin L.R., Biazzo K., Bignamini A., Borsa F., Claudi R.U.,
Covino E., Desidera S., Esposito M., Gratton R., Gonzalez Hernandez J.I.,
Lanza A.F., Maggio A., Molinari E., Pagano I., Perger M., Pillitteri I.,
Piotto G., Poretti E., Prisinzano L., Rebolo R., Ribas I., Shkolnik E.,
Southworth J., Sozzetti A., Suarez Mascareno A.
<Astron. Astrophys. 577, A132 (2015)>
=2015A&A...577A.132M 2015A&A...577A.132M
ADC_Keywords: Stars, M-type ; Abundances, [Fe/H] ; Spectroscopy
Keywords: techniques: spectroscopic - stars: late-type - stars: low-mass -
stars: fundamental parameters
Abstract:
Low-mass stars have been recognised as promising targets in the search
for rocky, small planets with the potential of supporting life. As a
consequence, Doppler search programmes using high-resolution
spectrographs like HARPS or HARPS-N are providing huge quantities of
optical spectra of M dwarfs.
We aim to calibrate empirical relationships to determine accurate
stellar parameters for early M dwarfs (spectral types M0-M4.5) using
the same spectra that are used for the radial velocity determinations.
Our methodology consists in the use of ratios of pseudo equivalent
widths of spectral features. Stars with effective temperatures
obtained from interferometric estimates of their radii are used as
calibrators. Empirical calibrations for the spectral type are also
provided. Combinations of features and ratios of features are used to
derive calibrations for the stellar metallicity.
Description:
File table2 provides the coefficients of our feature ratio-temperature
relations. It gives information about the features involved in the
ratio (central wavelength and width), the coefficients of the
best-fitting relationships, their functional form, and the
corresponding standard deviation of the effective temperature
calibration.
File table4 gives the coefficients of our spectral-type calibrations.
They are expressed as third order polynomial fits. Spectral types are
given in numerical form, i.e. with value 0.0 for M0, 0.5 for M0.5 and
so on. A negative value implies that the star is late K-dwarf, being
the index value for K7 equal to -1.0.
File table6 gives the coefficients of our metallicity calibrations.
They have the analytical form: [Fe/H]=(A*EW)+(B*r)+C, where EW is the
pseudo EW of a feature showing a strong-metallicity correlation, r is
a temperature-sensitive ratio of features, and A, B, C are independent
coefficients.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 63 112 Coefficients of our feature ratio-temperature
relations
table4.dat 58 82 Coefficients of our spectral type calibrations
table6.dat 69 696 Coefficients of our metallicity calibrations.
readme.txt 100 102 ReadMe for msdlines code
mdslines.tar 1124 623957 All files of msdlines code
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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- 7 F7.2 0.1nm lambda1 Wavelength of the numerator of the
temperature-sensitive ratio λ1
9- 12 F4.2 0.1nm delta1 Width of the feature Δλ1
14- 20 F7.2 0.1nm lambda2 Wavelength of the denominator of the
temperature-sensitive ratio λ2
22- 25 F4.2 0.1nm delta2 Width of the feature Δλ2
27- 35 F9.4 --- a Coefficient "a" of the calibration (1)
37- 46 F10.4 --- b Coefficient "b" of the calibration (1)
48- 54 F7.4 --- c ? Coefficient "c" of the calibration (1)
56- 57 A2 --- func Functional form of the calibration (1)
59- 63 F5.2 K sigma [49/75] Standard deviation of the calibration
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Note (1): Functional form of the calibration of Teff
(r is the ratio EW(λ1)/EW(λ2):
H = Hoerl (TTeff = abr x rc)
MH = Modified Hoerl (TTeff = ab(1/r) x rc)
PL = Power-law (TTeff = a x rb)
E = Exponential (TTeff = a x br)
L = Logarithmic (TTeff = a + b x ln(r))
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda1 Wavelength of the numerator of the
spectral-type sensitive ratio λ1 (2)
9- 15 F7.2 0.1nm lambda2 Wavelength of the denominator of the
spectral-type sensitive ratio λ2 (2)
17- 23 F7.4 --- a0 Zero order coefficient of the calibration a0
25- 33 F9.4 --- a1 First order coefficient of the calibration a1
35- 42 F8.4 --- a2 Second order coefficient of the calibration a2
44- 51 F8.4 --- a3 Third order coefficient of the calibration a3
53- 58 F6.4 --- sigma [0.4/0.5] Standard deviation of the calibration
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Note (2): calibration of Spectral Type, as a 3rd-order polynomial
Σairi, where r is the ratio EW(λ1)/EW(λ2)
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Byte-by-byte Description of file: table6.dat
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Bytes Format Units Label Explanations
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1- 7 F7.2 0.1nm lambda1 Wavelength of the metal-sensitive feature
(λ1)
9- 15 F7.2 0.1nm lambda2 Wavelength of the numerator of the
temperature-sensitive ratio (λ2)
17- 23 F7.2 0.1nm lambda3 Wavelength of the denominator of
the temperature-sensitive ratio (λ3)
25- 36 E12.5 --- A A coefficient of the calibration (3)
38- 49 E12.5 --- B B coefficient of the calibration (3)
51- 62 E12.5 --- C C coefficient of the calibration (3)
64- 69 F6.4 [Sun] sigma [0.07/0.1] Standard deviation of the calibration
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Note (3): calibration of [Fe/H], where r = EW(λ2)/EW(λ3):
[Fe/H] = A x EW(λ1) + B x r + C
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Acknowledgements:
Jesus Maldonado, jmaldonado(at)astropa.inaf.it
(End) Jesus Maldonado [INAF-OAPa, Italy], Patricia Vannier [CDS] 13-Mar-2015