Prof. Froney Crawford ’94 – Franklin and Marshall College
“An Observational Test of a Pulsar Spin-down Model Using Radio Polarimetry”
Pulsars are highly magnetized rotating neutron stars that are typically modeled as spinning magnetic point dipoles that lose rotational kinetic energy to dipole radiation. However, the spin-down behavior that is actually observed for pulsars deviates from the point dipole model in complicated ways. A recent theory attempts to explain this complex behavior by making a simple modification to the point dipole model. This proposed model has no free parameters, and its predictions are testable using only a few observable pulsar characteristics, making a test of this theory quite feasible. The young, highly polarized radio pulsar PSR J1119-6127 is one of the few known systems that can be used to test the model, and radio polarimetry of its pulsed emission offers the chance to constrain an elusive yet important parameter required for the test: the inclination angle between the pulsar’s magnetic and spin axes. Using archival radio telescope data from the Parkes telescope, an undergraduate student and I created polarization profiles for PSR J1119-6127 and fit the variation of the position angle of linear polarization across the pulse profile to a four-parameter model of the pulsar’s emission geometry. The resulting constraint on the inclination angle from this fit is used to try to rule out the proposed spin-down model.