Hubble parameter data constraints on dark energy
  We use Hubble parameter versus redshift data from Stern, et al(2010) and
Gazta\~{n}aga, et al (2009) to place constraints on model parameters of
constant and time-evolving dark energy cosmological models. These constraints
are consistent with (through not as restrictive as) those derived from
supernova Type Ia magnitude-redshift data. However, they are more restrictive
than those derived from galaxy cluster angular diameter distance, and
comparable with those from gamma-ray burst and lookback time data. A joint
analysis of the Hubble parameter data with more restrictive baryon acoustic
oscillation peak length scale and supernova Type Ia apparent magnitude data
favors a spatially-flat cosmological model currently dominated by a
time-independent cosmological constant but does not exclude time-varying dark
energy.
