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We revisit the kink-like parametrization of the deceleration parameter q(z),which considers a transition, at $z_t$, from cosmic deceleration toacceleration. In this parametrization the initial, at $z \gg z_t$, value of theq-parameter is $q_i$, its final, z=-1, value is $q_f$ and the duration of thetransition is parametrized by $\tau$. By assuming a flat space geometry weobtain constraints on the free parameters of the model using recent data fromtype Ia supernovae, BAO, CMB and the Hubble parameter H(z). The use of H(z)data introduces an explicit dependence of the combined likelihood on thepresent value of the Hubble parameter $H_0$, allowing us to explore theinfluence of different priors when marginalizing over this parameter. We alsostudy the importance of the CMB information in the results by considering datafrom WMAP7, WMAP9 and Planck. We show that the contours and best fit do notdepend much on the different CMB data used and that the considered new BAO datais responsible for most of the improvement in the results. Assuming a flatspace geometry, $q_i=1/2$ and expressing the present value of the decelerationparameter $q_0$ as a function of the other three free parameters, we obtain$z_t=0.67^{+0.10}_{-0.08}$, $\tau=0.26^{+0.14}_{-0.10}$ and$q_0=-0.48^{+0.11}_{-0.13}$, at 68\% of confidence level, with an uniform priorover $H_0$. If in addition we fix $q_f=-1$, as in flat $\Lambda$CDM, DGP andChaplygin quartessence that are special models described by ourparametrization, we get $z_t=0.66^{+0.03}_{-0.04}$, $\tau=0.33^{+0.04}_{-0.04}$and $q_0=-0.54^{+0.05}_{-0.07}$, in excellent agreement with flat $\Lambda$CDMfor which $\tau=1/3$. We also obtain for flat wCDM, another dark energy modeldescribed by our parametrization, the constraint on the equation of stateparameter -1.22 < w < -0.78 at more than 99% confidence level.

Constraining cosmic deceleration-acceleration transition with type Ia supernova, BAO/CMB and H(z) data