A survey for short-period pulsars

Abstract

All extensive pulsar surveys to date^1–5 have had sensitivities that deteriorate rapidly for periods P shorter than a few-tenths of a second, and none of them has had any appreciable sensitivity for P<30 ms. For this reason, the unexpected discovery of two millisecond pulsars^6,7 raised the question of the possible existence of a large population of very short-period pulsars, previously overlooked because of bias in the surveys. In an attempt to remove this bias, we have carried out an extensive new survey sensitive to pulsar periods as short as 4 ms. The search covered ∼ 3,725 square degrees, mostly at galactic latitudes |b| < 15° and longitudes 15° < l<230°, with a sensitivity of 2–100 mJy depending on period, dispersion measure, and sky background temperature. We detected 87 pulsars, including 20 new ones, but found none with P< 100 ms. We conclude that the Galaxy does not contain a large population of pulsars with 4< P< 100 ms, unless their radio luminosities are substantially less than those of slower pulsars.