We present an empirical calibration of the physical parameters of A , F and early G-type stars of luminosity class V. We have used a statistical approach based on a sample of about 15 000 stars having both uvby -Strömgren photomerty ( ) and spectral types taken from SIMBAD .
Stars closer than 70 pc have been considered reddening-free .
In this paper we present the results for 1900 stars within 70 pc .
Mean unreddened measurements have been used as input to CHORIZOS ( ) .
By assuming “ solar metallicity ” ( [ Fe/H ] =0 ) , we have been able to determine effective temperatures ( T _ { eff } ) and surface gravities ( \log g ) for each spectral type .
We have found a tight correlations among the observations and the derived physical parameters ; for example , T _ { eff } can be expressed as a cubic polynomial in \left ( b - y \right ) _ { 0 } .
From the distribution of colors and indices for 128 stars and their associated physical parameters we have proposed an alternative definition for solar-analogs : stars whose classification is G2 V with \left ( b - y \right ) _ { 0 } = 0.3927 \pm 0.0190 , \left ( m _ { 1 } \right ) _ { 0 } = 0.1901 \pm 0.0143 , and \left ( c _ { 1 } \right ) _ { 0 } = 0.3302 \pm 0.0388 , T _ { eff } = 5930 \pm 145 , and \log g = 4.70 \pm 0.33 .
These values are consistent with previous empirical results ; however , \left ( m _ { 1 } \right ) _ { 0 } differs from a recent model-based value for this index derived by .
This discrepancy points out the actual solar metallicity problem .
We suggest that our sample of solar analogs could be useful for searches of solar twins and exoplanets .