The bright gamma-ray burst GRB050525a has been detected with the Swift observatory , providing unique multiwavelength coverage from the very earliest phases of the burst .
The X-ray and optical/UV afterglow decay light curves both exhibit a steeper slope \sim 0.15 days after the burst , indicative of a jet break .
This jet break time combined with the total gamma-ray energy of the burst constrains the opening angle of the jet to be 3.2 ^ { \circ } .
We derive an empirical ‘ time-lag ’ redshift from the BAT data of \hat { z } = 0.69 \pm 0.02 , in good agreement with the spectroscopic redshift of 0.61 .

Prior to the jet break , the X-ray data can be modelled by a simple power law with index \alpha = -1.2 .
However after 300 s the X-ray flux brightens by about 30 % compared to the power-law fit .
The optical/UV data have a more complex decay , with evidence of a rapidly falling reverse shock component that dominates in the first minute or so , giving way to a flatter forward shock component at later times .
The multiwavelength X-ray/UV/Optical spectrum of the afterglow shows evidence for migration of the electron cooling frequency through the optical range within 25000s .
The measured temporal decay and spectral indices in the X-ray and optical/UV regimes compare favourably with the standard fireball model for Gamma-ray bursts assuming expansion into a constant density interstellar medium .