Compact Binaries and the Origin of Millisecond Pulsars

Michigan State University, East Lansing MI

Investigators

Abstract

The fastest-spinning neutron stars observable by astronomers have rotation periods of milliseconds and are known as millisecond pulsars.  These stars, of which about 250 are known in the Milky Way Galaxy, are important laboratories for modern astrophysics in fields ranging from general relativity to the study of supernovae.  Most have acquired their brisk spins by accretion of matter from a binary companion, a process known as "pulsar recycling." However, most of these systems have permanently stopped accreting and have low-mass white dwarf stellar companions, making it impossible to study the pulsar recycling process.   A research team at Michigan State University has developed a method to use the NSF-supported SOAR telescope to discover new pulsars that are still actively accreting, which will allow them to uncover how millisecond pulsars are formed and find new insights into the nature of neutron stars.   The team will do this by observing variable stars near gamma-ray sources newly discovered by NASA's Fermi Gamma-Ray Space Telescope, and measuring their detailed physical properties.  The team will mentor undergraduate students in astronomy research, with an emphasis on recruiting members of groups underrepresented in science, and also link public observing at the campus observatory to university football games. When spun up as millisecond pulsars in binary systems, neutron stars offer stringent tests of general relativity, and the most massive neutron stars can give clues to the details of supernovae explosions and constrain the equation of state of cold nuclear matter at densities exceeding those of atomic nuclei. The planned work will lead to the discovery of unique neutron star binaries, clarify the existence of new classes of neutron star binaries, inform models for millisecond pulsar evolution, and trace the mass distribution of neutron stars.   These binaries will be further characterized with multi-wavelength radio, X-ray, and gamma-ray data.