From Scientific American:
An international team of astronomers has discovered a new class of stars–massively compressed old neutron stars that seem inactive but for intermittent bursts of radio waves. Dubbing them rotating radio transients (RRATs), the researchers note that their isolated outbursts last for as few as two milliseconds and are separated by gaps as long as three hours.
“These things were very difficult to pin down,” says Dick Manchester of the Commonwealth Scientific and Industrial Research Organization’s (CSIRO) Australia Telescope National Facility. “For each object we’ve been detecting radio emissions for less than one second a day. And because these are single bursts, we’ve had to take great care to distinguish them from terrestrial radio interference.” Given the fact that the single, 35-minute observation that first revealed these new stars had only a roughly 20 percent chance of catching one of these outbursts, there may be as many as five times more of these RRATs than the 100,000 or so constant pulsars in the Milky Way.