%0 Journal Article
%T The signature of the central engine in the weakest relativistic explosions: GRB100316D
%A R. Margutti
%A A. M. Soderberg
%A M. H. Wieringa
%A P. G. Edwards
%A R. A. Chevalier
%A B. J. Morsony
%A R. Barniol Duran
%A L. Sironi
%A B. A. Zauderer
%A D. Milisavljevic
%A A. Kamble
%A E. Pian
%J Physics
%D 2013
%I arXiv
%R 10.1088/0004-637X/778/1/18
%X We present late-time radio and X-ray observations of the nearby sub-energetic Gamma-Ray Burst (GRB)100316D associated with supernova (SN) 2010bh. Our broad-band analysis constrains the explosion properties of GRB100316D to be intermediate between highly relativistic, collimated GRBs and the spherical, ordinary hydrogen-stripped SNe. We find that ~10^49 erg is coupled to mildly-relativistic (Gamma=1.5-2), quasi-spherical ejecta, expanding into a medium previously shaped by the progenitor mass-loss with rate Mdot ~10^-5 Msun yr^-1 (for wind velocity v_w = 1000 km s^-1). The kinetic energy profile of the ejecta argues for the presence of a central engine and identifies GRB100316D as one of the weakest central-engine driven explosions detected to date. Emission from the central engine is responsible for an excess of soft X-ray radiation which dominates over the standard afterglow at late times (t>10 days). We connect this phenomenology with the birth of the most rapidly rotating magnetars. Alternatively, accretion onto a newly formed black hole might explain the excess of radiation. However, significant departure from the standard fall-back scenario is required.
%U http://arxiv.org/abs/1308.1687v1