J/A+A/553/A95 PCA approach to stellar effective temperatures (Bermejo+, 2013)
A PCA approach to stellar effective temperatures.
Munoz Bermejo J, Asensio Ramos A., Allende Prieto C.
<Astron. Astrophys. 553, A95 (2013)>
=2013A&A...553A..95M 2013A&A...553A..95M
ADC_Keywords: Stars, standard ; Spectroscopy ; Effective temperatures
Keywords: stars: fundamental parameters - catalogs - techniques: spectroscopic -
stars: solar-type
Abstract:
The derivation of the effective temperature of a star is a critical
first step in order to perform a detailed spectroscopic analysis.
Spectroscopic methods suffer from systematic errors related to model
simplifications. Photometric methods may be more robust, but are
exposed to distortions caused by interstellar reddening. Direct
methods are difficult to apply, since fundamental data of high
accuracy are hard to obtain.
We explore a new approach in which the spectrum is used to
characterize a star's effective temperature based on a calibration
established by a small set of standard stars. We perform Principal
Component Analysis on homogeneous libraries of stellar spectra, then
calibrate a relationship between the principal components and the
effective temperature using a set of stars with reliable effective
temperatures. We find that our procedure gives excellent consistency
when spectra from a homogeneous set of observations are used.
Systematic offsets may appear when combining observations from
different sources. Using as reference the spectra of stars with
high-quality spectroscopic temperatures in the Elodie library, we
define a temperature scale for FG-type disk dwarfs with an internal
consistency of about 50K, in excellent agreement with temperatures
from direct determinations, but distinct from widely-used scales based
in the infrared flux method.
Description:
Effective temperatures, derived for stars with observations in the
Elodie library or the Elodie archive, from a PCA-based spectroscopic
calibration.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
table2.dat 47 765 Effective temperatures for stars in the
Elodie library
table4.dat 50 18696 Effective temperatures for individual spectra in
the Elodie archive
table5.dat 45 4039 Effective temperatures for stars in the Elodie
archive, derived by averaging multiple entries
for each star
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See also:
http://atlas.obs-hp.fr/elodie/ : the ELODIE archive
http://www.obs.u-bordeaux1.fr/m2a/soubiran/elodie_library.html :
ELODIE: the stellar library Home Page
III/251 : ELODIE library V3.1 (Prugniel+ 2007)
Byte-by-byte Description of file: table2.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 10 A10 --- FILE Filename from the Elodie archive
12- 20 A9 --- ID Star identifier (typically its HD number)
22- 25 I4 K Teff Effective temperature in the Elodie catalog
27 I1 --- q_Teff [0/4] Quality flag for the Elodie Teff
(4=best) (1)
29- 32 F4.2 [cm/s2] logg log10 of the surface gravity from Elodie
34 I1 --- q_logg [0/1] Quality flag for the surface gravity
from Elodie (2)
36- 40 F5.2 --- [Fe/H] Iron abundance (log10 scale normalized to Sun)
42 I1 --- q_[Fe/H] [0/4] Quality flag for the Fe abundance from
Elodie (4=best) (3)
44- 47 I4 K PCATeff Teff from this paper's PCA analysis
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Note (1): Quality flag for Teff as follows:
1 = Poor determination -> 4 = Excellent
0 = means that we have estimated Teff from the B-V colour (Tycho2 catalogue),
assuming the empirical colour-temperature relation for a main sequence
star and neglecting the interstellar extinction
Note (2): Quality flag for loog as follows:
1 = logg is taken from the literature
0 = logg was converted from the V absolute magnitude from Hiparcos and Teff,
using a bolometric correction valid for a main sequence start and an
empirical mass-to-light relation
Note (3): Quality flag for [Fe/H] as follows:
1 = Poor determination -> 4 = Excellent
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Byte-by-byte Description of file: table4.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- ID Star identifier
33- 45 A13 --- OBSID Observation ID in the Elodie archive
47- 50 I4 K Teff Effective temperature from paper's PCA analysis
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Byte-by-byte Description of file: table5.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 31 A31 --- ID Star identifier
33- 36 I4 K Teff Effective temperature from paper's PCA
analysis
38- 41 I4 K e_Teff Standard deviation among spectra of the same
target
43- 45 I3 --- Nspec Number of spectra available for this target
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Acknowledgements:
Carlos Allende Prieto, callende(at)astro.as.utexas.edu
History:
* 25-Mar-2013: Original version (problems in table4)
* 30-Jul-2013: table4 fixed, with corrected OBSIDs in table4
(from the author)
(End) Patricia Vannier, Francois Ochsenbein [CDS] 25-Mar-2013