Image courtesy of NRAO/AUI
Image courtesy of NRAO/AUI |
XRF 060218 was a faint Gamma-Ray Burst (GRB) detected by NASA's Swift satellite on February 18 2006. The on-board follow-up instruments quickly identified an optical/X-ray transient. Comparison with optical images from the Sloan Digital Sky Survey showed that the transient source was associated with a nearby galaxy just 500 million light-years away. At this distance, the gamma-ray and X-ray emission were 100 times fainter than that observed for typical GRBs and XRFs. Our radio observations with the Very Large Array showed that the radio afterglow was similarly sub-luminous and led us to infer a kinetic energy for the explosion which is 100 times smaller than that observed for typical GRBs but similar to that inferred for the nearest burst, GRB 980425. Using these two nearby bursts, we estimate that sub-energetic bursts are up to 10 times more common than typical GRBs. We speculate that the physical difference between sub-energetic and typical bursts may be the nature of their central engine -- magnetar versus black hole. |
