GRB 000926 has one of the best-studied afterglows to-date , with multiple X-ray observations , as well as extensive multi-frequency optical and radio coverage .
Broadband afterglow observations , spanning from X-ray to radio frequencies , provide a probe of the density structure of the circumburst medium , as well as of the ejecta energetics , geometry , and the physical parameters of the relativistic blastwave resulting from the explosion .
We present an analysis of Chandra X-ray Observatory observations of this event , along with Hubble Space Telescope and radio monitoring .
We combine these data with ground-based optical and IR observations and fit the synthesized afterglow lightcurve using models where collimated ejecta expand into a surrounding medium .
We find that we can explain the broadband lightcurve with reasonable physical parameters if the cooling is dominated by inverse Compton scattering .
For this model , an excess due to inverse Compton scattering appears above the best-fit synchrotron spectrum in the X-ray band .
No previous bursts have exhibited this component , and its observation would imply that the GRB exploded in a moderately dense ( n \sim 30 cm ^ { -3 } ) medium , consistent with a diffuse interstellar cloud environment .