Issue |
A&A
Volume 454, Number 1, July IV 2006
|
|
---|---|---|
Page(s) | 333 - 340 | |
Section | Stellar atmospheres | |
DOI | https://doi.org/10.1051/0004-6361:20064999 | |
Published online | 03 July 2006 |
Computed H
indices from ATLAS9 model atmospheres
1
Istituto Nazionale di Astrofisica, Osservatorio Astronomico di Trieste, via G.B. Tiepolo 11, 34131 Trieste, Italy e-mail: castelli@oats.inaf.it
2
Harvard-Smithsonian Center for Astrophysics, 60 Garden Street, Cambridge, MA, USA e-mail: rkurucz@cfa.harvard.edu
Received:
10
February
2006
Accepted:
6
April
2006
Aims.Grids of H indices based on updated (new-ODF) ATLAS9 model atmospheres were computed for solar and scaled solar metallicities [+0.5], [+0.2], [0.0], [ -0.5] , [ -1.0] , [ -1.5] , [ -2.0] , [ -2.5] and for α enhanced compositions [+0.5a], [0.0a], [ -0.5a] , [ -1.0a] , [ -1.5a] ,
[ -2.0a] , [ -2.5a] , and [ -4.0a] .
Methods.Indices for Teff > 5000 K were computed with the same methods as described by
Lester et al. (1986, LGK86) except for a different normalization of the computed natural system
to the standard system. LGK86 used special ODFs to compute the fluxes.
For Teff ≤ 5000 K we computed the fluxes using the synthetic spectrum method. In order to assess the accuracy of the computed indices comparisons were made with the indices computed
by Smalley & Dworetsky (1995, A&A, 293, 446, MD95) and with the empirical relations Teff–H given by Alonso et al. (1996, A&A, 313, 873) for several metallicities. Furthermore, for cool stars, temperatures inferred from the computed indices were compared with those of the fundamental stars listed by MD95.
The same kind of comparison was made between gravities for B-type stars.
Results.The temperatures from the computed indices are in good agreement, within the error limits, with the literature values for 4750 K ≤ Teff ≤ 8000 K, while the gravities agree for Teff > 9000 K. The computed H indices for the Sun and for Procyon
are very close to the observed values. The comparison between the observed
and computed H
indices as function of the observed H
has shown a very small trend which almost completely disappears when only stars hotter than 10 000 K are
considered. The trend due to the cool stars is probably related with the
low accuracy of the fundamental Teff which are affected by large errors for most of the stars.
Key words: stars: atmospheres / stars: fundamental parameters / techniques: photometric
© ESO, 2006
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