The UVOT telescope on the Swift observatory has detected optical afterglow emission from GRB 050319 .
The flux declines with a power law slope of \alpha = -0.57 between the start of observations some 230 seconds after the burst onset ( 90s after the burst trigger ) until it faded below the sensitivity threshold of the instrument after \sim 5 \times 10 ^ { 4 } s. There is no evidence for the rapidly declining component in the early light curve that is seen at the same time in the X-ray band .
The afterglow is not detected in UVOT shortward of the B-band , suggesting a redshift of about 3.5 .
The optical V-band emission lies on the extension of the X-ray spectrum , with an optical to X-ray slope of \beta = -0.8 .
The relatively flat decay rate of the burst suggests that the central engine continues to inject energy into the fireball for as long as a few \times 10 ^ { 4 } s after the burst .