ARE SUPERLUMINOUS SUPERNOVAE AND LONG GRBs THE PRODUCTS OF DYNAMICAL PROCESSES IN YOUNG DENSE STAR CLUSTERS?

Abstract

Super Luminous supernovae (SLSN) occur almost exclusively in small galaxies (SMC/LMC-like or smaller), and the few SLSN observed in larger star-forming galaxies always occur close to the nuclei of their hosts. Another type of peculiar and highly energetic supernovae are the broad-line type Ic SNe (SN Ic-BL) that are associated with long-duration gamma-ray bursts (LGRBs). Also these have a strong preference for occurring in small (SMC/LMC-like or smaller) star-forming galaxies, and in these galaxies LGRBs always occur in the brightest spots. Studies of nearby star-forming galaxies that are similar to the hosts of LGRBs show that these brightest spots are giant HII regions produced by massive dense young star clusters with many hundreds of O- and Wolf-Rayet-type stars. Such dense young clusters are also found in abundance within a few hundred parsecs from the nucleus of larger galaxies like our own. We argue that the SLSN and the SN Ic-BL/LGRBs are exclusive products of two types of dynamical interactions in dense young star clusters. In our model the high angular momentum of the collapsing stellar cores required for the "engines" of a SN Ic-BL results from the post-main sequence mergers of dynamically produced cluster binaries with almost equal-mass components. The merger produces a critically rotating single helium star with sufficent angular momentum to produce a LGRB; the observed "metal aversio" of LGRBs is a natural consequence of the model. We argue that, on the other hand, SLSN could be the products of runaway multiple collisions in dense clusters, and we present (and quantize) plausible scenarios of how the different types of SLSNs can be produced.