2007A&A...463..913A

We analyze and discuss the position of GRB060218 and GRB060614 in the E_p,i - E_iso plane. GRB060218 is important because of its similarity with GRB 980425, the prototypical event of the GRB-SN connection. While GRB980425 is an outlier of the E_p,i-E_iso correlation, we find that GRB060218 is fully consistent with it. This evidence, combined with the ``chromatic'' behavior of the afterglow light curves, is at odds with the hypothesis that GRB 060218 was a ``standard'' GRB seen off-axis and supports the existence of a class of truly sub-energetic GRBs. GRB060614 is a peculiar event not accompanied by a bright supernova. Based on published spectral information, we find that also this event is consistent with the E_p,i-E_iso correlation. We discuss the implications of our results for the rate of sub-energetic GRBs, the GRB/SN connection and the properties of the newly discovered sub-class of long GRBs not associated with bright supernovae. We have included in our analysis other recent GRBs with clear evidence (or clear evidence of lack) of associated SNe.