I have designed a dedicated, multi-wavelength campaign utilizing radio, X-ray and optical facilities to target the nearest (z < 0.3) GRBs.   While early studies suggested that all GRBs produce roughly the 10⁵¹ erg of relativistic energy, I have shown that this is not entirely true. In fact, though my dedicated study, I have discovered a new class of explosions that are sub-energetic compared to typical GRBs and only detectable nearby.  These sub-energetic GRBs are further differentiated from ordinary bursts in that they (1) show no evidence for strongly collimated jets, and (2) are up to 10 times more common.  In two recent Nature papers,  I discuss the properties of this large class of sub-energetic GRBs lurking in the nearby Universe.

See my  press release page to read the International media response to this exciting discovery.
 

Energy released in gamma-rays is compared to the ejecta kinetic energy for cosmological GRBs (upper right) and the newly discoverd class of  sub-energetic bursts (labeled).  Typical bursts release ~10⁵¹ erg in gamma-rays and have ~10⁵¹ erg in ejecta energy  implying a total relativistic energy yield of 2x10⁵¹ erg (arc).  The nearest GRBs (labeled) are outliers in one or both axes

Discovered in the 1990's, the class of XRFs are distinguished by their X-ray rich prompt emission spectrum that peaks a factor of 10 lower than those of GRBs. While several lines of evidence (e.g.~durations) initially suggested that the mysterious XRFs are similar to GRBs, the lack of XRF redshift measurements prevented a clear comparison. In 2003, I set the distance scale to XRFs by measuring the first redshift, z=0.25, to XRF 020903 (right).  Not only did this breakthrough establish that XRFs are cosmological in origin, but also showed that their total energy output is similar to that of GRBs.  Finally, my discovery of a supernova associated with an XRF showed that they too are produced by the death of massive stars.  

See my press release page to read the media response to this exciting discovery.
 

Just like ordinary SNe Ibc, GRBs and XRFs produce strong optical emission on timescales less than 30 days after the explosion attributed to the radioactive decay of Nickel-56.  Through a comprehensive investigation utilizing both ground-based and Hubble Space Telecope data,  I compared the optical luminosities for GRB-SNe, XRF-SNe, and ordinary SNe Ibc.  As shown at right, I found that the classes are remarkably similar. This surprising result suggests that there is a common Nickel-56 production mechanism for GRBs, XRFs, and ordinary SNe and may even suggest similar explosion mechanisms.   This result was not anticipated given that GRBs and XRFs require central "engines" (accreting compact source) to power their gamma-ray emission while ordinary SNe do not. 

See my SN page to read more about my research on ordinary SNe  Ibc and their relation to GRBs and XRFs.