J/A+A/589/A83 PCA-based inversion of stellar parameters (Gebran+, 2016)
A new method for the inversion of atmospheric parameters of A/Am stars.
Gebran M., Farah W., Paletou F., Monier R., Watson V.
<Astron. Astrophys. 589, A83 (2016)>
=2016A&A...589A..83G 2016A&A...589A..83G (SIMBAD/NED BibCode)
ADC_Keywords: Stars, fundamental ; Stars, Am ; Stars, A-type ;
Abundances, [Fe/H] ; Effective temperatures ;
Rotational velocities
Keywords: stars: fundamental parameters - stars: early-type - methods: numerical
Abstract:
We present an automated procedure that simultaneously derives the
effective temperature Teff, surface gravity logg, metallicity [Fe/H],
and equatorial projected rotational velocity vsini for "normal" A and
Am stars. The procedure is based on the principal component analysis
(PCA) inversion method, which we published in a recent paper. A sample
of 322 high-resolution spectra of F0-B9 stars, retrieved from the
Polarbase, SOPHIE, and ELODIE databases, were used to test this
technique with real data. We selected the spectral region from
4400-5000 Ang as it contains many metallic lines and the Balmer
Hβ line.
Using three data sets at resolving powers of R=42000, 65000 and 76000,
about ∼6.6x10^6 synthetic spectra were calculated to build a large
learning database. The Online Power Iteration algorithm was applied to
these learning data sets to estimate the principal components (PC).
The projection of spectra onto the few PCs offered an efficient
comparison metric in a low-dimensional space. The spectra of the
well-known A0- and A1-type stars, Vega and Sirius A, were used as
control spectra in the three databases. Spectra of other well-known
A-type stars were also employed to characterize the accuracy of the
inversion technique. We inverted all of the observational spectra and
derived the atmospheric parameters. After removal of a few outliers,
the PCA-inversion method appeared to be very efficient in determining
Teff, [Fe/H], and vsini for A/Am stars. The derived parameters agree
very well with previous determinations. Using a statistical approach,
deviations of around 150K, 0.35dex, 0.15dex, and 2km/s were found
for Teff, logg, [Fe/H], and vsini with respect to literature values
for A-type stars. The PCA inversion proves to be a very fast,
practical, and reliable tool for estimating stellar parameters of FGK
and A stars and for deriving effective temperatures of M stars.
Description:
Inverted effective temperatures, surface gravities, projected
rotational velocities, metalicities, and radial velocities for the
selected A stars. The "closest" are the values found in Vizier
catalogues closest to our inverted parameters, while "median" are the
median of the catalogue values. Outliers are marked as "1" in the
"outliers" column (see sect. 6)
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table2.dat 108 306 Inverted effective temperatures, surface gravities,
projected equatorial rotational velocities,
metallicities, and radial velocities for the
selected A stars of PolarBase, SOPHIE, and ELODIE
databases
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See also:
III/260 : General Catalogue of Ap and Am stars (Renson+ 2009)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
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1- 10 A10 --- Star Star name or number
12 A1 --- Outliers [1] Data outlier (1)
14- 20 F7.1 K Teff Effective temperature
22- 28 F7.1 K Teffc ? Closest effective temperature
30- 36 F7.1 K Teffm ? Median effective temperature
38- 40 F3.1 [cm/s2] logg Logarithm of gravity
42- 47 F6.2 [cm/s2] loggc ? Closest logarithm of gravity
49- 54 F6.2 [cm/s2] loggm ? Median logarithm of gravity
56- 60 F5.1 km/s vsini Projected Rotational Velocity
62- 67 F6.2 km/s vsinic ? Closest projected rotational velocity
69- 74 F6.2 km/s vsinim ? Median projected rotational velocity
76- 79 F4.1 [-] [Fe/H] Iron abundance relative to the sun
81- 86 F6.2 [-] [Fe/H]c ? Closest Iron abundance
88- 93 F6.2 [-] [Fe/H]m ? Median Iron abundance
95- 99 F5.1 km/s RV Radial Velocity
101-108 A8 --- Com Comments on stars (2)
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Note (1): The outliers have been selected based on the large difference
between the inverted parameters and the values retrieved from the catalogues.
See Section 6 of the paper.
Note (2): Comments as follows:
SB = Spectroscopic binary
BS = Binary star
EB = Eclipsing binary
Ae/Be = Herbig Ae/Be star
V = Variable
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Acknowledgements:
Wael Farah, wael.a.farah(at)gmail.com
(End) Wael Farah [NDU, Lebanon], Patricia Vannier [CDS] 15-Mar-2016