Pulsar wind nebulae created by fast-moving pulsars

We review multiwavelength properties of pulsar wind nebulae created by supersonically moving pulsars and the effects of pulsar motion on the pulsar wind nebulae morphologies and the ambient medium. Supersonic pulsar wind nebulae are characterized by bow-shaped shocks around the pulsar and/or cometary tails filled with the shocked pulsar wind. In the past several years significant advances in supersonic pulsar wind nebula studies have been made in deep observations with the Chandra and XMM-Newton X-ray observatories and the Hubble Space Telescope. In particular, these observations have revealed very diverse supersonic pulsar wind nebula morphologies in the pulsar vicinity, different spectral behaviours of long pulsar tails, the presence of puzzling outflows misaligned with the pulsar velocity and far-UV bow shocks. Here we review the current observational status focusing on recent developments and their implications.

PULSAR KICKS WITH STANDARD AND STERILE NEUTRINOS AND LANDAU LEVELS

I first give an update on our study of the energy asymmetry given the proto-neutron star during the time when the neutrino sphere is near the surface of the proto-neutron star, at a time 10-20s, using the modified URCA process. With the magnetic field strong enough for a large fraction of the electrons produced with the anti-neutrinos to be in the lowest Landau level, we predict a pulsar velocity of 1.03 × 10−4(T/1010K)7 km / s , which reaches 1000 km/s if T ≃ 9.96 × 1010 K . Also, using the recent results of the MiniBoone study, with two sterile neutrinos, I give results for pulsar kicks during the first 10s.

Bow Shocks from Radio Pulsars: Observations of the Guitar Nebula

We present optical observations and radio non-detections of the bow shock nebula associated with the pulsar B2224+65 (the “Guitar Nebula”), and fit an analytic model to the observed bow shock to estimate its inclination and constrain other parameters (distance, pulsar velocity, ISM density). We also test scaling laws for bow shock parameters.

PULSAR VELOCITIES DUE TO VIOLATION OF THE EQUIVALENCE PRINCIPLE BY NEUTRINOS

We consider the pulsar velocity problem and relate it to some unconventional neutrino oscillation mechanisms based on the violation of the equivalence principle by neutrinos. We show that the observed pulsar velocities may be explained by violations at the level from 10-9 to 10-10 in the case of a non-universal tensor neutrino-gravity coupling, whereas there is no solution in the case of a non-universal scalar neutrino-gravity coupling. Neutrinos may remain massless and the requisite magnetic field strength is similar to that in the conventional mass oscillation mechanism.

The Origin of Millisecond Pulsar Velocities

We have developed a computer code (Tauris & Bailes 1996) to follow the evolution of a binary system from the zero-age main sequence to its “final” state as a binary millisecond pulsar (BMSP), at all stages keeping careful track of the mass and orbital separation of the two stars.To help determine the origin of millisecond pulsars, we compute the space velocities predicted by various models of their formation. It is difficult to produce a millisecond pulsar velocity greater than 270 km s−1with any model, unless the formation of the neutron star is accompanied by some form of asymmetric kick. We obtain average 3-D system velocities of 〈vrecoil〉= 99.6, 137.6 and 160.7 km s−1using Gaussian kicks of 〈vkick〉=0, 200 and 450 km s−1(σ=0, 100 and 200 km s - 1, respectively). Our computations show that, in general, we expect those systems with shorter orbital periods to have larger velocities than those with longer periods, but any relation between the final orbital period and space velocity is fairly weak, especially if asymmetries are involved.