Dark energy equation of state parameter and its variation at low
  redshifts
  In this paper, we constrain dark energy models using a compendium of
observations at low redshifts. We consider the dark energy as a barotropic
fluid, with the equation of state a constant as well the case where dark energy
equation of state is a function of time. The observations considered here are
Supernova Type Ia data, Baryonic Acoustic Oscillation data and Hubble parameter
measurements. We compare constraints obtained from these data and also do a
combined analysis. The combined observational constraints put strong limits on
variation of dark energy energy density with redshift. For varying dark energy
models, the range of parameters preferred by the supernova type Ia data is in
tension with the other low redshift distance measurements.
