Soft Gamma-Ray Repeater Light Echoes Captured by Swift Satellite
on February 10, 2009
The X-Ray Telescope (XRT) aboard NASA's Swift satellite captured light echoes from a soft-gamma-ray repeater. These stellar remnants, which are thought to be highly magnetized neutron stars called magnetars, occasionally belt out a series of X- and gamma-ray flares. On Jan. 22, 2009, an object known as SGR J1550-5418 began its second and most intense round of outbursts since October 2008. In the following days, Swift's XRT captured what appears to be an expanding halo as X-rays from the brightest bursts scatter off of intervening dust. Multiple rings form as the X-rays interact with different dust clouds. Closer clouds produce larger rings. Both the rings and their apparent expansion are an effect of light's finite speed and the longer path the scattered light must travel. They will be studied to make a more reliable measurement of the distance to the source and to the dust clouds.