Spectroscopic characterization of a sample of metal-poor solar-type
  stars from the HARPS planet search program. Precise spectroscopic parameters
  and mass estimation
  Stellar metallicity strongly correlates with the presence of planets and
their properties. To check for new correlations between stars and the existence
of an orbiting planet, we determine precise stellar parameters for a sample of
metal-poor solar-type stars. This sample was observed with the HARPS
spectrograph and is part of a program to search for new extrasolar planets. The
stellar parameters were determined using an LTE analysis based on equivalent
widths (EW) of iron lines and by imposing excitation and ionization
equilibrium. The ARES code was used to allow automatic and systematic
derivation of the stellar parameters. Precise stellar parameters and
metallicities were obtained for 97 low metal-content stars. We also present the
derived masses, luminosities, and new parallaxes estimations based on the
derived parameters, and compare our spectroscopic parameters with an infra-red
flux method calibration to check the consistency of our method in metal poor
stars. Both methods seems to give the same effective temperature scale. Finally
we present a new calibration for the temperature as a function of \textit{B-V}
and [Fe/H]. This was obtained by adding these new metal poor stars in order to
increase the range in metallicity for the calibration. The standard deviation
of this new calibration is $\sim$ 50 K.
