Estimation of the Star Formation Rate using Long-Gamma Ray Burst
  observed by SWIFT
  In this work we estimate the Star Formation Rate (SFR) through 333 Long-GRBs
detected by Swift. This investigation is based on the empirical model proposed
by Y\"uksel et al. (2008), basically, the SFR is estimated using long-GRBs
considering that they have an stellar origin based on the Collapsar model or
the collapse of massive stars (Hypernova) $M>20 M_{\bigodot} $. The analysis
starts with the study of $\varepsilon (z)$ which accounts the long-GRBs
production rate and it is parameterized by
$\varepsilon(z)=\varepsilon_{0}(1+z)^{\delta} $ where $\varepsilon_{0}$ include
the SFR absolute conversion to GRBs rate in a luminosity range already defined
and $\delta$ is a dynamical parameter which changes at different regions of
redshift it accounts the SFR slope which is obtained by an analysis of linear
regression over our Long-GRBs sample, the results obtained provide evidence
that support our proposal to use Long-GRBs as tracers of SFR.
