A new method for the inversion of atmospheric parameters of A/Am stars
Abstract
Context. We present an automated procedure that simultaneously derives the effective temperature T_{eff}, surface gravity log g, metallicity [Fe/H], and equatorial projected rotational velocity vsini for "normal" A and Am stars. The procedure is based on the principal component analysis (PCA) inversion method, which we published in a recent paper .
Aims: A sample of 322 highresolution spectra of F0B9 stars, retrieved from the Polarbase, SOPHIE, and ELODIE databases, were used to test this technique with real data. We selected the spectral region from 44005000 Å as it contains many metallic lines and the Balmer Hβ line.
Methods: Using three data sets at resolving powers of R = 42 000, 65 000 and 76 000, about ~6.6 × 10^{6} synthetic spectra were calculated to build a large learning database. The online power iteration algorithm was applied to these learning data sets to estimate the principal components (PC). The projection of spectra onto the few PCs offered an efficient comparison metric in a lowdimensional space. The spectra of the wellknown A0 and A1type stars, Vega and Sirius A, were used as control spectra in the three databases. Spectra of other wellknown Atype stars were also employed to characterize the accuracy of the inversion technique.
Results: We inverted all of the observational spectra and derived the atmospheric parameters. After removal of a few outliers, the PCAinversion method appeared to be very efficient in determining T_{eff}, [Fe/H], and vsini for A/Am stars. The derived parameters agree very well with previous determinations. Using a statistical approach, deviations of around 150 K, 0.35 dex, 0.15 dex, and 2 km s^{1} were found for T_{eff}, log g, [Fe/H], and vsini with respect to literature values for Atype stars.
Conclusions: The PCA inversion proves to be a very fast, practical, and reliable tool for estimating stellar parameters of FGK and A stars and for deriving effective temperatures of M stars. Based on data retrieved from the Polarbase, SOPHIE, and ELODIE archives.Table 2 is only available at the CDS via anonymous ftp to http://cdsarc.ustrasbg.fr (ftp://130.79.128.5) or via http://cdsarc.ustrasbg.fr/vizbin/qcat?J/A+A/589/A83
 Publication:

Astronomy and Astrophysics
 Pub Date:
 May 2016
 DOI:
 10.1051/00046361/201528052
 arXiv:
 arXiv:1603.01146
 Bibcode:
 2016A&A...589A..83G
 Keywords:

 stars: fundamental parameters;
 stars: earlytype;
 methods: numerical;
 Astrophysics  Instrumentation and Methods for Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 16 pages, 9 figures. Accepted in A&