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SN1993J in M81 is the best studied young radio-luminous supernova in theNorthern Hemisphere. We recently reported results from the analysis of acomplete set of VLBI observations of this supernova at 1.7, 2.3, 5.0, and 8.4GHz, covering a time baseline of more than one decade. Those reported resultswere focused on the kinematics of the expanding shock, the particulars of itsevolving non-thermal emission, the density profile of the circumstellar medium,and the evolving free-free opacity by the supernova ejecta. In the presentpaper, we complete our analysis by performing a search for any possible signalfrom a compact source (i.e., a stellar-mass black hole or a young pulsarnebula) at the center of the expanding shell. We have performed a stacking ofall our VLBI images at each frequency, after subtraction of our best-fit shellmodel at each epoch, and measured the peak intensity in the stacked residualimage. Given the large amount of available global VLBI observations, thestacking of all the residual images allows us to put upper limits to theeventual emission of a putative compact central source at the level of$\sim102$ $\mu$Jy at 5 GHz (or, more conservatively, $\sim192$ $\mu$Jy, if wemake a further correction for the ejecta opacity) and somewhat larger at otherwavelengths.

Limit to the radio emission from a putative central compact source in SN1993J