Physical Interpretations of Rotating Radio Transients

Nearly a dozen of Rotating RAdio Transients (RRATs) have been discovered recently. These objects share similar spin parameters with normal radio pulsars but distinguish themselves from normal pulsars by being quiescent most of the time and only becoming radio bright occasionally. We discuss two possible interpretations to the phenomenon. The first model suggests that these objects are pulsars slightly below the radio emission “death line”, and become active occasionally when the conditions for pair production and coherent emission are satisfied. The second model invokes a radio emission direction reversal in normal pulsars, as has been introduced to interpret the peculiar mode changing phenomenon in PSR B1822-09. In this picture, our line of sight misses the main radio emission beam of RRATs but happens to sweep the emission beam when the radio emission direction is reversed. RRATs are therefore the other half of the normal “nulling” pulsars. We suggest that X-ray observations can provide clues to differentiate these two possibilities. Subject headings: stars: pulsars X-ray: observation radiation mechanism: coherent radio