Weakly radiating radio pulsars

We analyze the statistical distribution of weakly radiating pulsars, i.e., radio pulsars that have passed to the stage of an orthogonal rotator during the evolution of the inclination angle X. We discuss in detail the factors that lead to a significant reduction in the energy losses for this class of objects. We have determined the number of weakly radiating radio pulsars and their distribution in spin period P. The predictions of a theory based on the model of current losses are shown to be consistent with observational data.     

Statistics of extinct radio pulsars

We study the statistical distribution of extinct radio pulsars at the stage of an ejector. An important element that distinguishes our study from other works is a consistent allowance for the evolution of the angle of inclination of the magnetic axis to the spin axis. We determined the distribution of extinct radio pulsars in spin period for two models: the model with hindered particle escape from the neutron-star surface and the model with free particle escape. The total number of extinct radio pulsars is shown to be much smaller than that in the model in which the evolution of the angle of axial inclination is disregarded. This is because when the evolution of the angle of axial inclination is taken into account, the transition to the stage of a propeller occurs at much shorter neutron-star spin periods (P ～ 5–10 s) than assumed previously.     

Multifrequency polarimetry of 300 radio pulsars

Polarimetric observations of 300 pulsars have been conducted with the 76-m Lovell telescope at Jodrell Bank at radio frequencies centred around 230, 400, 600, 920, 1400 and 1600 MHz. More than half of the pulsars have no previously published polarization profiles and this compilation represents about three times the sum of all previously published pulsar polarization data. A selection of integrated polarization profiles is provided. Tables of pulse widths and the degree of both linear and circular polarization are given for all pulsars, and these act as an index for all the data, which are available by anonymous ftp in numerical and graphical form.     

Morphology and characteristics of radio pulsars

This review describes the observational properties of radio pulsars, fast rotating neutron stars, emitting radio waves. After the introduction we give a list of milestones in pulsar research. The following chapters concentrate on pulsar morphology: the characteristic pulsar parameters such as pulse shape, pulsar spectrum, polarization and time dependence. We give information on the evolution of pulsars with frequency since this has a direct connection with the emission heights, as postulated in the radius to frequency mapping (RFM) concept. We deal successively with the properties of normal (slow) pulsars and of millisecond (fast-recycled) pulsars. The final chapters give the distribution characteristics of the presently catalogued 1300 objects.Received: 5 December 2003, Published online: 15 April 2004 Correspondence to: Richard Wielebinski     

Possibilities for detecting extinct radio pulsars

We explore the possibilities for detecting pulsars that have ceased to radiate in the radio band. We consider two models: the model with hindered particle escape from the pulsar surface [first suggested by Ruderman and Sutherland (1975)] and the model with free particle escape (Arons 1981; Mestel 1999). In the model with hindered particle escape, the number of particles that leave the pulsar magnetosphere is small and their radiation cannot be detected with currently available instruments. At the same time, for Arons' model, both the number of particles and the radiation intensity are high enough for such “extinct” pulsars to be detectable with the GLAST and INTEGRAL satellites.     

30 glitches in 18 radio pulsars

Pulsar timing is a classic technology of detecting irregularities in pulsar rotation.We carried out this method for 18 young radio pulsars,with long-term timing observations obtained between 2007 and 2015 using the Parkes 64-m radio telescope.As a result,30 glitches were identified,ranging from 0.75 × 10~(-9) to 8.6 × 10~(-6) in the relative glitch sizes Δv/v,where v=1/P is the pulse frequency.These glitches are composed of 26 new glitches and four published glitches with new exponential recoveries.All pulsars exhibit normal glitches,and six pulsars were observed to undergo a glitch event for the first time.We discuss the properties and implications for neutron-star physics of these glitches,and show that they are in agreement with previous work,except that the cumulative probability distributions of the mean waiting times for PSRs J0537-6910,J1341-6220 and J1740-3015 are not in consonance with the Poisson model.     

Theory of the radio emission of pulsars

A consistent theory of excitation, stabilization, and propagation of electromagnetic oscillations in a relativistic one-dimensional electron-positron plasma flowing along curved magnetic field lines is presented. It is shown that in such a medium which is typical of the magnetosphere of a neutron star there exist unstable natural modes of oscillations. Nonlinear saturation of the instability leads to an effective energy conversion into transverse oscillations capable of leaving the magnetosphere of a pulsar. The polarization spectrum and the directivity pattern of generated radiation are determined. A comparison with observations has shown that the theory makes it possible to explain practically all the basic characteristics of observed pulsar radio emission.     

The possible companions of young radio pulsars

We discuss the formation of pulsars with massive companions in eccentric orbits. We demonstrate that the probability for a non-recycled radio pulsar to have a white dwarf as a companion is comparable to that of having an old neutron star as a companion. Special emphasis is given to PSR B1820−11 and PSR B2303+46. Based on population synthesis calculations we argue that PSR B1820−11 and PSR B2303+46 could very well be accompanied by white dwarfs with mass ≳1.1 M_⊙. For PSR B1820−11, however, we cannot exclude the possibility that its companion is a main-sequence star with a mass between ∼0.7 M_⊙ and ∼5 M_⊙.     

The nature of radio emission from pulsars

It is shown that radio emission from pulsars is unlikely to be of coherent synchrotron origin if the surface magnetic field of the central neutron star is greater than 10⁸ G.     

HartRAO observations of glitches in radio pulsars

Results of regular monitoring of radio pulsars over the past ten years are described. Several glitches in PSR 0833-45 and PSR 1641-45 have been observed.     

A possible radio emission mechanism for pulsars

The magnetic field in the neutron-proton-electron (npe) layer of a neutron star is caused by quasi-stationary vortex current of superconducting and normal protons relative to the normal electrons. The same current generates the radio emission due to the Josephson effect. The radiation propagates in the magnetically-active medium and goes out the crust through the cracks to the magnetosphere (npe-layer is optically thick layer). As a result the hot radiospots on the star surface develop and a resulting polarized radiation pattern near the magnetic poles is formed. The cross-section of this radiation pattern gives the observed pulse structure of the pulsar. The variations of quasi-stationary vortex current can result in the amplitude-frequency variations of the radiation spectrum due to specific properties of the radiation mechanism. From this we have the variations of the fine spectrum structure, pulse amplitude and pulse structure and the correlation of them with the spectral index variations of pulsars in this model.     

Statistical analysis of the radio luminosity of pulsars

The results of statistical analyses of the radio luminsotiy of 81 pulsars obtained in this paper appear to be in favour of the view that the radio emission originates in regions close to the light cylinder. The various statistical relations given in TABLES 1 and 2 may provide some clues on the radio emission.     

Radio pulsars with expected gamma radiation and gamma-ray pulsars as pulsating radio emitters

Pulsars play a crucial astrophy sical role as highly energetic compact radio, X-ray and gammaray sources. Our previous works show that radio pulsars identified as pulsing gamma-ray sources by the Large Area Telescope(LAT) on board the Fermi Gamma-Ray Space Telescope have high values of magnetic field near the light cylinder, two-three orders of magnitude stronger compared with the magnetic fields of radio pulsars: log B_(lc)(G) are 3.60-3.95 and 1.75 correspondingly. Moreover,their losses of rotational energy are also three orders higher than the corresponding values for the main group of radio pulsars on average: log E(erg s~(-1)) = 35.37-35.53 and 32.64. The correlation between gammaray luminosities and radio luminosities is found. It allows us to select those objects from all sets of known radio pulsars that can be detected as gamma-ray pulsars with high probability. We provide a list of such radio pulsars and propose to search for gamma emission from these objects. On the other hand,the known catalog of gamma-ray pulsars contains some sources which are not currently identified as radio pulsars. Some of them have large values of gamma-ray luminosities and according to the obtained correlation, we can expect marked radio emission from these objects. We give the list of such pulsars and expected flux densities to search for radiation at frequencies 1400 and 111 MHz.