J/A+A/533/A107 SED for 7 stellar calibrators (Dehaes+, 2011)
Structure of the outer layers of cool standard stars.
Dehaes S., Bauwens E., Decin L., Eriksson K., Raskin G., Butler B.,
Dowell C.D., Ali B., Blommaert J.A.D.L.
<Astron. Astrophys. 533, A107 (2011)>
=2011A&A...533A.107D 2011A&A...533A.107D
ADC_Keywords: Stars, giant ; Models ; Spectroscopy ; Energy distributions
Keywords: stars, chromospheres - stars, late-type - stars, winds, outflows -
radio continuum: stars
Abstract:
Among late-type red giants, an interesting change occurs in the
structure of the outer atmospheric layers as one moves to later
spectral types in the Hertzsprung-Russell diagram: a chromosphere is
always present, but the coronal emission diminishes and a cool massive
wind steps in.
Where most studies have focussed on short-wavelength observations,
this article explores the influence of the chromosphere and the wind
on long-wavelength photometric measurements. The goal of this study is
to assess wether a set of standard near-infrared calibration sources
are fiducial calibrators in the far-infrared, beyond 50um.
The observational spectral energy distributions were compared with the
theoretical model predictions for a sample of nine K- and M-giants.
The discrepancies found are explained using basic models for flux
emission originating in a chromosphere or an ionised wind.
Description:
This catalogue presents the theoretical spectral energy distributions
for 7 stellar calibrators of the ESA Herschel satellite in the
wavelength range from 2 to 200 micron.
The stellar atmosphere model and theoretical spectrum are generated
using the MARCS theoretical stellar atmosphere code (Gustafsson et
al., 1975A&A....42..407G 1975A&A....42..407G and further updates; Gustafsson et al.
2003A&A...400..709D 2003A&A...400..709D) and the TURBOSPECTRUM synthetic spectrum code
(Plez et al., 1992A&A...256..551P 1992A&A...256..551P). Stellar parameters (and
uncertainties thereon) have been derived by Decin et al.
(2003A&A...400..709D 2003A&A...400..709D) and are described in the text files added to
this catalogue. The line lists used in the spectrum calculation are
discussed in Decin (2000, PhD Thesis, Leuven University) and Decin and
Eriksson (2007A&A...472.1041D 2007A&A...472.1041D).
The outermost depth point of the theoretical atmosphere model was
taken at log(taulambda)=-7.2 with lambda being 2.2 micron. The
atmosphere model was calculated with a spherically symmetric (parallel
for Sirius) geometry, under the assumption of radiative and
hydrostatic equilibrium, local thermodynamic equilibrium (LTE) and
homogeneous layers.
The original theoretical spectrum was calculated at a resolution of
Δλ=0.5Å, and then degraded to a resolution of
λ/Δλ=5000 applying a gaussian convolution. The
wavelength coverage is from 2 to 200 micron.
Uncertainties on the theoretical spectrum predictions are discussed in
depth in Decin & Eriksson (2007A&A...472.1041D 2007A&A...472.1041D).
Absolute flux calibration is based on Selby (1988A&AS...74..127S 1988A&AS...74..127S)
K-band (TCS for Sirius) photometry
Zero-point is determined on the basis of an ideal 'Vega', i.e. the
K-band photometry of Vega is corrected for a flux excess of 1.29% (cf.
Absil et al. 2006A&A...452..237A 2006A&A...452..237A). The determined Selby K-band
zeropoint is 4.0517E-10 W/m2/um. The determined TCS K-band zeropoint
is 4.4506E-10W/m2/um (for Sirius)
The estimated absolute flux uncertainty is 1%
These theoretical spectra should be referenced as Decin & Eriksson
(2007A&A...472.1041D 2007A&A...472.1041D).
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
stars.dat 127 7 Studied stars
mod/* . 7 Individual model SED
fit/* . 7 Individual model SED as fits files
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Byte-by-byte Description of file: stars.dat
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Bytes Format Units Label Explanations
--------------------------------------------------------------------------------
1- 9 A9 --- Name Name
11- 19 A9 --- OName Other name
21- 22 I2 h RAh Right ascension (J2000)
24- 25 I2 min RAm Right ascension (J2000)
27- 30 F4.1 s RAs Right ascension (J2000)
32 A1 --- DE- Declination sign (J2000)
33- 34 I2 deg DEd Declination (J2000)
36- 37 I2 arcmin DEm Declination (J2000)
39- 40 I2 arcsec DEs Declination (J2000)
42- 47 A6 --- SpType MK spectral type
49- 53 I5 K Teff Effective temperature
55- 58 F4.2 [cm/s2] logg Surface gravity
60- 63 F4.2 Msun Mass Mass
65- 67 F3.1 km/s vt Turbulent velocity ξ
69- 73 F5.2 [Sun] [Fe/H] Metallicity
75- 78 F4.2 [-] C Carbon abundance (log scale, H=12)
80- 83 F4.2 [-] N Nitrogen abundance (log scale, H=12)
85- 88 F4.2 [-] O Oxygen abundance (log scale, H=12)
90- 93 F4.2 [-] Mg ?=- Magnesium abundance (log scale, H=12)
95- 98 F4.2 [-] Si ?=- Silicon abundance (log scale, H=12) (1)
100-101 I2 --- Cr ?=- 12C/13C abundance ratio
103-108 F6.3 mag Kmag K-band magnitude
110-114 F5.2 mas Diam Derived angular diameter based on the
K-band photometry
116-127 A12 --- FileName Name of the model file in subdirectory mod
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Note (1): other atomic abundances are solar scaled with the metallicity
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Byte-by-byte Description of file: mod/*
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Bytes Format Units Label Explanations
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1- 9 F9.5 um lambda [2/198] Wavelength
11 I1 --- Weight [1] Weight
13- 23 F11.5 Jy Flux Flux density
25 I1 --- Flag [0] Flag
27 I1 --- Seg [0] Segment
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Acknowledgements:
Eva Bauwens, eva(at)ster.kuleuven.be
(End) Patricia Vannier [CDS] 01-Sep-2011