In this paper , we set the new limits on the equation of state parameter ( EoS ) of dark energy with the observations of cosmic microwave background radiation ( CMB ) from Planck satellite , the type Ia supernovae from Pan-STARRS and the baryon acoustic oscillation ( BAO ) .
We consider two parametrization forms of EoS : a constant w and time evolving w ( a ) = w _ { 0 } + w _ { a } ( 1 - a ) .
The results show that with a constant EoS , w = -1.141 \pm { 0.075 } ( 68 \%~ { } C . L . ) , which is consistent with \Lambda CDM at about 2 \sigma confidence level .
For a time evolving w ( a ) model , we get w _ { 0 } = -1.09 ^ { +0.16 } _ { -0.18 } ( 1 \sigma~ { } C . L . ) , w _ { a } = -0.34 ^ { +0.87 } _ { -0.51 } ( 1 \sigma~ { } C . L . ) , and in this case \Lambda CDM can be comparable with our observational data at 1 \sigma confidence level .
In order to do the parametrization independent analysis , additionally we adopt the so called principal component analysis ( PCA ) method , in which we divide redshift range into several bins and assume w as a constant in each redshift bin ( bin-w ) .
In such bin-w scenario , we find that for most of the bins cosmological constant can be comparable with the data , however , there exists few bins which give w deviating from \Lambda CDM at more than 2 \sigma confidence level , which shows a weak hint for the time evolving behavior of dark energy .
To further confirm this hint , we need more data with higher precision .