New Phase-coherent Measurements of Pulsar Braking Indices

Pulsar braking indices offer insight into the physics that underlies pulsar spin-down. Only five braking indices have been measured via phase-coherent timing; all measured values are less than 3, the value expected from magnetic dipole radiation. Here we present new measurements for three of the five pulsar braking indices, obtained with phase-coherent timing for PSRs J1846−0258 (n = 2.65 ± 0.01), B1509−58 (n = 2.839±0.001) and B0540−69 (n = 2.140±0.009).We disM. Livingstone Physics Department, McGill University Rutherford Physics Building 3600 University Street Montreal, Qc H3A 2T8 Canada E-mail: [email protected] V.M. Kaspi Physics Department, McGill University Rutherford Physics Building 3600 University Street Montreal, Qc H3A 2T8 Canada F.P. Gavriil NASA Goddard Space Flight Center Code 662, X-ray Astrophysics Laboratory Greenbelt, MD 20771 R.N. Manchester Australia National Telescope Facility CSIRO P.O. Box 76 Epping NSW 1710 Australia E.V. Gotthelf Columbia Astrophysics Laboratory Columbia University 550 West 120th Street New York, NY 10027-6601 L. Kuiper Netherlands Institute for Space Research Sorbonnelaan 2 3584 CA Utrecht, Netherlands cuss the implications of these results and possible physical explanations for them.