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Centro de Astrofísica da Universidade do Porto
StePar: an automatic code for stellar parameter determination

Hugo M. Tabernero Guzmán
Departamento de Astrofísica, UCM

I will present some aspects of the automatic code StePar (Tabernero et al. 2012) for determinig stellar atmospheric parameters (Teff, logg, ξ and [Fe/H]). StePar employs the 2002 version of the MOOG code (Sneden 1973) and a grid of Kurucz ATLAS9 plane-paralell model atmospheres (Kurucz 1993). The atmospheric parameters are obtained from the EWs from any previously selected Fe I-II linelist. StePar iterates until the excitation and ionization equilibrium are fullfilled. It uses a Downhill Simplex method (Press et al. 1992) that minimizes a quadratic form composed by the excitation and ionization equilibrium conditions.
Atmospheric parameters determined by StePar are independent of the stellar parameters initial-guess for the problem star, therefore we employ the canonical solar values as initial input. StePar can only deal with FGK stars from F6 to K4. It can also not work with fast rotators, veiled spectra, very metal poor stars or very low signal to noise ratio spectra.
Optionally StePar can operate with MARCS models (Gustafsson et al. 2008) instead of Kurucz ATLAS9 models, additionally Turbospectrum (Álvarez and Plez 1998) can replace the MOOG code and play its role during the parameter determination. StePar has been used to determine stellar parameters for some studies (González Hernández et al. 2012, Tabernero et al. 2012, Wisniewski et al. 2012). In addition StePar is being used to obtain parameters for FGK stars from the GAIA-ESO Survey.

02 maio 2013, 13:30

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