J/A+A/624/A10 Normalized Halpha line profiles of FGK stars (Giribaldi+, 2019)
Accurate affective temperature from Hα profiles.
Giribaldi R.E., Ubaldo-Melo M.L., Porto de Mello G.F., Pasquini L.,
Ludwig H.-G, Ulmer-Moll S., Lorenzo-Oliveira D.
<Astron. Astrophys. 624, A10 (2019)>
=2019A&A...624A..10G 2019A&A...624A..10G (SIMBAD/NED BibCode)
ADC_Keywords: Spectroscopy ; Stars, dwarfs ; Stars, F-type ; Stars, G-type ;
Stars, K-type
Keywords: line: profiles - techniques: spectroscopic - stars: atmospheres -
stars: fundamental parameters - stars: late-type - stars: solar-type
Abstract:
The determination of stellar effective temperature (Teff) in F, G,
and K stars using Halpha profile fitting is a quite remarkable and
powerful tool because it does not depend on reddening and is only
slightly sensitive to other atmospheric parameters. Nevertheless, this
technique is not frequently used because of the complex procedure
needed to recover the profile of broad lines in echelle spectra. As a
consequence, tests performed on different models have sometimes
provided ambiguous results. The main aim of this work is to test the
ability of the Halpha profile fitting technique to derive T_eff. We
also aim to improve the applicability of this technique to echelle
spectra and to test how well 1D+LTE models perform on a variety of F-K
stars. We also apply the technique to HARPS spectra and test the
reliability and the stability of the HARPS response over several years
using the Sun. We have developed a normalization method for recovering
undistorted Halpha profiles and we have first applied it to spectra
acquired with the single-order coude instrument (resolution R=45000)
at do Pico dos Dias Observatory to avoid the problem of blaze
correction. The continuum location around Halpha is optimised using an
iterative procedure, where the identification of minute telluric
features is performed. A set of spectra was acquired with the MUSICOS
echelle spectrograph (R=40000) to independently validate the
normalization method. The accuracy of the method and of the 1D+LTE
model is determined using coude/HARPS/MUSICOS spectra of the Sun and
coude-only spectra of a sample of ten Gaia Benchmark Stars with Teff
determined from interferometric measurements. HARPS, coude, and
MUSICOS spectra are used to determine Teff of 43 sample stars. We
find that a proper choice of spectral windows of fits plus the
identification of telluric features allow for a very careful
normalization of the spectra and produce reliable Hα profiles.
We also find that the most used solar atlases cannot be used as
templates for Halpha temperature diagnostics without renormalization.
The comparison with the Sun shows that Hα profiles from 1D+LTE
models underestimate the solar Teff by 28K. We find the same
agreement between Halpha and interferometry and between Halpha and
Infrared Flux Method: a shallow dependency on metallicity according to
the relation Teff=TeffHalpha-159[Fe/H]+28K within the
metallicity range -0.70 to +0.40dex. The comparison with the Infrared
Flux Method shows a scatter of 59K dominated by photometric errors
(52K). In order to investigate the origin of this dependency, we
analysed spectra from 3D models and found that they produce hotter
temperatures, and that their use largely improves the agreement with
the interferometric and Infrared Flux Method measurements. Finally, we
find HARPS spectra to be fully suitable for Halpha profile temperature
diagnostics; they are perfectly compatible with the coude spectra, and
lead to the same Teff for the Sun as that found when analysing HARPS
spectra over a timespan of more than 7 years.
Description:
Normalized observational Hα line profiles of 43 F- ,G- , and
K-type stars, including the Sun. The profiles were recorded in spectra
acquired by the single-order coude instrument at do Pico dos Dias
Observatory. The spectra are provided in .fits format, and their
observation conditions are registered in the headers of the files. For
some spectra, a version corrected from telluric contamination is also
provided but in ascii format only. These files contain three columns:
Wavelength (Angstrom), telluric-corrected flux, and non
telluric-corrected flux. Some telluric-corrected spectra may present
obvious correction errors. Some spectra may be contaminated by cosmic
rays. The names of the files indicate the Henry Draper catalog number
of the star, except for the Sun, for which the names of the solar
surrogates are indicated. The name of the stars are followed by a
number 1, 2, 3, or 4, which indicates a different spectrum of the same
star.
File Summary:
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FileName Lrecl Records Explanations
--------------------------------------------------------------------------------
ReadMe 80 . This file
list.dat 108 45 List of objects with spectra
sp/* . 51 Individual fits spectra
spc/* . 23 Individual telluric-corrected spectra
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Byte-by-byte Description of file: list.dat
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Object name
11- 12 I2 h RAh ? Right ascension (J2000)
14- 15 I2 min RAm ? Right ascension (J2000)
17- 21 F5.2 s RAs ? Right ascension (J2000)
23 A1 --- DE- Declination sign (J2000)
24- 25 I2 deg DEd ? Declination (J2000)
27- 28 I2 arcmin DEm ? Declination (J2000)
30- 33 F4.1 arcsec DEs ? Declination (J2000)
36- 50 A15 --- Sp Name of the first spectrum in fits,
in subdirectory sp
52- 67 A16 --- Spc Name of the spectrum corrected from telluric
contamination in ascii, in subdirectory spc
69- 83 A15 --- Sp2 Name of the second spectrum in fits,
in subdirectory sp
86- 96 A11 --- Sp3 Name of the third spectrum in fits,
in subdirectory sp
98-108 A11 --- Sp4 Name of the fourth spectrum in fits,
in subdirectory sp
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Byte-by-byte Description of file (#): spc/*
--------------------------------------------------------------------------------
Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 15 F15.10 0.1nm lambda Wavelength
19- 30 F12.10 --- Fluxc Telluric-corrected normalized flux
34- 45 F12.10 --- Flux Non telluric-corrected normalized flux
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Acknowledgements:
Riano Giribaldi, rescateg(at)eso.org
(End) Patricia Vannier [CDS] 04-Mar-2019