High-sensitivity searches for radio pulsars

[摘要] Radio pulsars are rapidly spinning, highly magnetized neutron stars which emit beams of radio waves and are observed to pulse when the beam crosses the Earth. They represent the end-point in the evolution of massive stars, and are excellent laboratories for the study of the bulk properties of matter at nuclear densities and beyond. Millisecond pulsars are old pulsars reborn through accretion of matter from a companion star, spinning so fast that the surface velocities approach the speed of light.We describe several high-sensitivity searches for radio pulsars, both for very recently born pulsars in supernova remnants and for ancient millisecond pulsars born early in the history of the Galaxy.We have conducted a survey of 18 supernova remnants for young pulsars using the 305-m radio telescope in Arecibo, Puerto Rico at 430 MHz and 1400 MHz. No pulsars were discovered in this survey which was sensitive to pulsars as faint as 0.2 mJy. The selection effects making pulsars difficult to find in supernova remnants, including high background temperatures of the remnants and high birth velocities of pulsars, are discussed. We conclude that deeper and more extensive surveys are required to constrain the pulsar population in supernova remnants.We have also performed several very large area surveys with excellent sensitivity to pulsars as fast as 1 millisecond, also employing the Arecibo 305-m dish. These surveys will help place limits on the population of low-luminosity pulsars in the Galaxy. A total of 12 non-recycled pulsars were discovered with periods ranging from 96 ms to 2.06 seconds.The primary motivation for these surveys was the discovery of new millisecond pulsars. One 5.9 ms pulsar was discovered and initial timing observations show that it is in a binary system with orbital period 56.2 d and semi-major axis 20.1 lt-s. The implied companion mass is at least 0.2 solar masses. This pulsar, as well as a number of others discovered in recent surveys, are providing excellent laboratories for studies of the formation and evolution of millisecond pulsars, as well as measurements of general relativistic parameters, constraints on the cosmological background of gravitational waves, a pulsar based time standard and dynamical-optical frame ties.

[发布机构] University:California Institute of Technology;Department:Physics, Mathematics and Astronomy

[关键词] Physics