from 1998 to 2002...the team's computer algorithm identified 11 bursting radio sources coming from various directions near the galactic plane. The team spent the next three years observing the sky coordinates of these objects to confirm the discovery and to measure their properties. On average these bursting objects are invisible for all but 0.1 to 1 second per day, which explains why they were not discovered earlier. The bursts last between 2 and 30 milliseconds, with intervals between bursts ranging from 4 minutes to 3 hours. Previous astronomers might have interpreted such signals as radio interference. The group found periodicities for 10 of the 11 sources, falling between 0.4 and 7 seconds. This regularity strongly suggests (but does not prove) that the radio bursts come from rotating neutron stars. McLaughlin's team has affectionately named these objects RRATs, short for Rotating RAdio Transients.

Source: Sky and Telescope