A Search for Submillisecond Pulsations in Unidentified FIRST and NVSS Radio Sources

We have searched 92 unidentified sources from the FIRST and NVSS 1400 MHzradio survey catalogs for radio pulsations at 610 MHz. The selected radiosources are bright, have no identification with extragalactic objects, arepoint-like and are more than 5% linearly polarized. Our search was sensitive tosub-millisecond pulsations from pulsars with dispersion measures (DMs) lessthan 500 pc cm-3 in the absence of scattering. We have detected no pulsationsfrom these sources and consider possible effects which might prevent detection.We conclude that as a population, these sources are unlikely to be pulsars.Comment: 8 pages, including 2 tables and 1 figure. Accepted for publication in A