J/AJ/117/2308 Spectroscopy of hot stars in the halo (Wilhelm+, 1999)
Spectroscopy of hot stars in the galactic halo. II. The identification and
classification of horizontal-branch and other A-type stars
Wilhelm R., Beers T.C., Gray R.O.
<Astron. J. 117, 2308 (1999)>
=1999AJ....117.2308W 1999AJ....117.2308W
ADC_Keywords: Abundances, [Fe/H] ; Colors ; Equivalent widths ;
Models, atmosphere ; Stars, halo ; Stars, horizontal branch
Keywords: Galaxy: halo - stars: horizontal-branch - stars: Population II
Abstract:
We discuss a spectroscopic and photometric technique that enables the
identification and classification of field horizontal-branch (FHB) and
other A-type stars, even from relatively low signal-to-noise ratio
medium-resolution spectra. This technique makes use of broadband UBV
colors predicted from model atmosphere calculations and Balmer line
profiles and Ca II K equivalent widths determined from synthetic
spectra to estimate the physical parameters Teff, log(g), and [Fe/H]
for stars in the effective temperature range 6000 - 10,000 K.
Description:
We have computed a total of 833 synthetic spectra, using the ATLAS9
model atmospheres from Kurucz CD-ROM 13 (R. L. Kurucz 1993, private
communication) and the PC-based spectral synthesis routine SPECTRUM
(Gray & Corbally 1994). The parameter space we explore covers the
ranges 6000 K ≤ Teff ≤ 10,000 K, in increments of 250 K,
2.0 ≤ log(g) ≤ 5.0, in increments of 0.5 dex, and
-3.0 ≤ [Fe/H] ≤ 0.0, in increments of 0.5 dex. This range is
set, at the cool end, by the limit at which surface gravities can be
reliably determined from U-B colors and, at the hot end, by the point
at which surface gravity can be used as a luminosity class indicator
and at which the Ca II K line can be employed as a metal abundance
estimator.
File Summary:
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FileName Lrecl Records Explanations
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ReadMe 80 . This file
table1.dat 74 833 Calibration grid from Kurucz model atmospheres
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See also:
J/AJ/103/267 : Spectrocopy of hot stars in galactic halo (Beers+ 1992)
VI/39 : Model Atmospheres (Kurucz, 1979)
Byte-by-byte Description of file: table1.dat
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Bytes Format Units Label Explanations
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1- 5 I5 K Temp Effective temperature of Kurucz model
8- 10 F3.1 [g/cm2] log(g) Log of the surface gravity of Kurucz model
14- 18 F5.1 [Sun] [Fe/H] Log of the iron abundance relative to
hydrogen of Kurucz model
22- 26 F5.2 mag B-V Predicted B-V from Kurucz color calibrations
30- 34 F5.2 mag U-B Predicted U-B from Kurucz color calibrations
38- 42 F5.2 0.1nm EqWCa Equivalent width of the Ca II K line
46- 50 F5.2 0.1nm EqWH4 Equivalent width of Hδ
54- 58 F5.2 0.1nm EqWH3 Equivalent width of Hγ
62- 66 F5.2 0.1nm DH4 Full width at 20% below a local continuum
level of Hδ
70- 74 F5.2 0.1nm DH3 Full width at 20% below a local continuum
level of Hγ
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History:
From AJ electronic edition
References:
Gray, R. O., & Corbally, C. J. 1994, AJ, 107, 742 (1994AJ....107..742G 1994AJ....107..742G)
(End) Greg Schwarz [AAS] 06-Apr-2000