Toward a standard Gamma Ray Burst: tight correlations between the prompt and the afterglow plateau phase emission

Abstract

To reveal and understand astrophysical processes responsible for the Gamma Ray Burst (GRB) phenomenon, it is crucial to discover and understand relations between their observational properties. The presented study is performed in the GRB rest frames and it uses a sample of 62 long GRBs from our sample of 77 Swift GRBs with known redshifts. Following the earlier analysis of the afterglow {\it characteristic luminosity $L^*_a$ -- break time $T^*_a$} correlation for a sample of long GRBs \citep{Dainotti2010} we extend it to correlations between the afterglow and the prompt emission GRB physical parameters. We reveal a tight physical scaling between the mentioned afterglow luminosity $ L^*_a$ and the prompt emission {\it mean} luminosity $<L^*_p>_{45} \equiv E_{iso}/T^*_{45}$. The distribution, with the Spearman correlation coefficient reaching 0.95 for the data subsample with most regular light curves, can be fitted with approximately $L^*_a \propto {<L^*_p>_{45}}^{0.7}$. We also analyzed correlations of $L^*_a$ with several other prompt emission parameters, including the isotropic energy $E_{iso}$, the peak energy in the $\nu F_{\nu}$ spectrum, $E_{peak}$, and the variability parameter, $V$, defined by \cite{N000}. As a result, we reveal significant correlations also between these quantities, with an exception of the variability parameter. The main result of the present study is the discovery that the highest correlated GRB subsample in the \citet{Dainotti2010} afterglow analysis, for the GRBs with canonical X\,-\,ray light curves, leads also to the highest {\it prompt-afterglow} correlations and such events can be considered to form a sample of standard GRBs for astrophysics and cosmology.