Radio observations probe the fastest material ejected in stellar explosions and are therefore well-suited for searching for relativistic ejecta.  In 2002 I began a large radio survey of local (d < 150 Mpc) SNe Ibc with the Very Large Array. Since then, I have observed roughly 200 SNe Ibc.  Through this study, I have characterized the ejecta and environmental properties of SNe Ibc for the first time and increased the sample of radio SNe Ibc tenfold.  I find that GRB-SNe are easily distinguished by their early, bright radio emission attributed to relativistic ejecta,  and that less than 10% of SNe Ibc show strong radio emission.  Moreover, I have searched for "off-axis" GRBs and XRFs where the jets were initially pointed away from our line-of-sight, and find that these events are also rare.  Most exciting, I find a dispersion in the radio emission from SNe Ibc that spans four orders of magnitude, indicating significant dispersion in their explosion and/or progenitor properties.
 

Radio light-curves and upper limits (grey triangles) for local SNe Ibc (color) and GRB-SNe (black).  Clearly, GRB-SNe can be distinguished from ordinary SNe Ibc based on their early, bright radio emission.    From Soderberg,  2006,  (astro-ph/0601693)

X-ray observations also trace the fastest ejecta in stellar explosions and therefore are complemenary to radio observations.  As part of my thesis, I have undertaken a detailed X-ray survey of nearby (z < 0.1) SNe Ibc and GRB-SNe using the Chandra X-ray Observatory and the Swift X-ray Telescope.   As shown at right, GRB-SNe are easily distinguished from ordinary SNe based on their early, bright X-ray emission.   Most recently, I have shown that X-rays may also enable a direct view to the central engine -- in some cases probing a newly born magnetar.   Finally, through this study I have found a large dispersion in the temporal and spectral properties of X-ray SNe Ibc, echoing what is seen at radio wavelengths.
 
Soderberg et al. , 2004,  Nature,  430,  648

In contrast to the radio and X-rays, optical emission traces the slower ejecta to which the bulk of the kinetic energy is coupled.  Based on a comprehensive study of the early-time optical luminosities for GRB-SNe, XRF-SNe, and ordinary SNe Ibc, I have shown that the populations are effectively indistinguishable, perhaps indicative of similar Nickel-56 production mechanism (see my GRB page for more details). However, ejecta asymmetries (e.g. GRB jets) may significantly affect this comparison.  Fortunately, an independent constraint on the Nickel mass may be derived through late-time monitoring of the optical emission,  powered by the decay of Cobalt-56. A comparison of the Nickel masses values derived through early- and late-time optical light-curves enables a direct mapping of the ejecta asymmetries.  I am investigating this question through observations at the Palomar 200-inch telescope.