I. F. Malov

The distribution of space velocities of radio pulsars

The distribution of the directions of the space velocities of 67 radio pulsars is shown to be strongly anisotropic. This anisotropy cannot be explained by the structure of our Galaxy or by various types of solar motions. Pulsars with stronger surface magnetic fields B have higher velocities V. The mean value of V for B < 1010 G is 108 km/s, while 〈V〉 = 340 km/s for B > 1010 G. These results must be taken into account when identifying a mechanism to explain the observed pulsar velocities and their anisotropy.

The drift model for AXPs and SGRs in the light of new observtional data

The latest observational data are analyzed to investigate their consistency with two known models for anomalous X-ray pulsars (AXPs) and soft gamma-ray repeaters (SGRs): the magnetar and drift models. The results of spectral measurements disagree with the predictions of theories that assume the presence of super-strong magnetic fields on AXPs and SGRs and associated processes for the generation of electron-positron plasma in the upper layers of the neutron-star magnetosphere. We present arguments against the use of magnetic-dipole braking for these objects. The rotational periods P, period derivatives dP/dt, and magnetic fields B of known AXPs and SGRs are calculated for the drift model. The mean values of these parameters in the sample used are 〈P〉 = 108 ms and 〈log Bs [G]〉 = 12.08. Overall, the measured profiles, polarizations, and spectra can be brought into agreement with the drift model.

The spectra of hard radiation from radio pulsars

The kinetic equation for the distribution function of relativistic electrons is solved taking into account quasi-linear interactions with waves and radiative processes. Mean values of the pitch angles ψ are calculated. If the particles of the primary beam with Lorentz factors γb∼106 are resonant, then the condition γbψb≲1 is satisfied, the particle distribution is described by the function f‖(γ) ∝ γ−4, and the synchrotron radiation spectrum is characterized by the spectral index α=3/2. On the other hand, if a cyclotron resonance is associated with particles of the high-energy tail of the secondary plasma (γt∼105), then γtψt≫1, and the distribution function has two parts—f‖(γ) ∝ γ and f‖(γ) ∝ γ−2—which correspond to the spectral indices α1=+1 and α2=−0.5. This behavior is similar to that observed for the pulsar B0656+14. The predicted frequency of the maximum νm=7.5×1016 Hz coincides with the peak frequency for this pulsar. The model estimate for the total synchrotron luminosity of a typical radio pulsar with hard radiation Ls=3×1033 erg/s is in agreement with observed values.

Angles between the rotational axis and magnetic moment in 80 pulsars from observations near 1 GHz

Data on the pulse structure and variations of the linear polarization angle at frequencies near 1 GHz have been used to estimate the angles β between the rotational axis and magnetic moment of the neutron stars assocaited with 80 pulsars. The calculations applied several methods. The minimum values of β were estimated from the observed pulse width W10 at the 10% level for the entire sample. Maximum estimates of β were obtained for six sources with small polarization position angle derivatives. Equations for the angle β were derived for various forms of the observed profile, and solutions obtained for 34 pulsars. The β values calculated using different methods are compared. For three pulsars with known interpulses, the obtained values of β demonstrate that two (PSR B1055-52 and PSR 1822-09) are aligned rotators, whereas the other (PSR B1702-19) is an orthogonal rotator. A search for interpulses and interpulse emission in PSRB1641-45, PSR1642-03, and PSR 1944+17 is necessary, and a search for an interpulse at 180° from the main pulse is required in PSR B2321-61.

Integrated radio luminosities of pulsars

The integrated radio luminosities of 311 long-period (P > 0.1 s) and 27 short-period (P < 0.1 s) pulsars have been calculated using a new compilation of radio spectra. The luminosities are in the range 1027 − 1030 erg/s for 88% of the long-period pulsars and 1028 − 1031 erg/s for 88% of the short-period pulsars. We find a high correlation between the luminosity L and the estimate L1 = S400d2 from the catalog of Taylor et al. The factor η for the transformation of the rotational energy of the neutron star into radio emission increases-decreases with increasing period for long-period and short-period pulsars. The mean value of η is −3.73 for the long-period and −4.85 for short-period pulsars. No dependence was found between L and the pulsar’s kinematic age tk = |z|/〈vz〉, where |z| and 〈vz〉 = 300 km/s are the pulsars’ height above the plane of the Galaxy and mean velocity. A dependence of L on the rate of rotational energy losses Ė was found for both groups of pulsars. It is shown that L ∝ Ė1/3 for the entire sample. The pulsar luminosity function is constructed, and the total number and birth rate of pulsars in the Galaxy are calculated.

Do magnetars really exist

We perform a comparative analysis of the properties of isolated single neutron stars and show the absence of any single typical feature providing unambiguous evidence that they belong to the classes of AXPs or SGRs. Several objects with features intermediate between AXPs and radio transients (RRATs) have been discovered recently: radio pulsars with high magnetic fields, radio-emitting AXPs, etc. Assuming the existence of fields of 1016 G in the stellar interiors cannot explain the giant gamma-ray outbursts of SGRs. It appears necessary to invoke other energy sources, such as nuclear reactions in the matter that breaks through the crust of the neutron star. For the recently discovered AXP PSR J1642-4950, we find that the angle β between its spin axis and magnetic moment is 15.6°. This agrees with earlier estimates for the AXPs J1810-197 and 1E 1547.0-5408, which have β < 10°. The similarity of these objects to aligned rotators enables a description using the drift model. This model yields a rotational period for PSR J1642-4950 of P = 0.32 s, amagnetic field in the radiation generation region of B = 950 G, and a surfacemagnetic field ofBs = 3.39×1012 G. It is shown that the cyclotron instability in the neighbourhood proximity of the light cylinder, associated with particles in the tail of the secondary-plasma distribution, can explain the generation of the radio emission of PSR J1642-4950, which should be observed predominantly at low frequencies (∼100 MHz).

The geometry of radio pulsar magnetospheres

Data on the profiles and polarization of the 10- and 20-cm emission of radio pulsars are used to calculate the angle β between the rotational axis of the neutron star and its magnetic moment. It is shown that, for these calculations, it is sufficient to use catalog values of the pulse width at the 10% level W10, since the broadening of the observed pulses due to the transition to the full width W0 and narrowing of the pulses associated with the emission of radiation along tangents to the field lines approximately cancel each other out. The angles β1 are calculated for 283 pulsars at 20 cm and 132 pulsars at 10 cm, assuming that the line of sight passes through the center of the emission cone. The mean values of these angles are small and similar for the two wavelengths (〈β1〉 = 18° at λ = 10 cm and 〈β1〉 = 14° at λ = 20 cm). The angle β2 is estimated for several dozen pulsars for the case when the orientation of the angle to the line of sight is arbitrary. The mean value of β2 at 10 cm is found to be 〈β2〉 = 33.9° if the maximum derivative of the polarization position angle C is positive and 〈β2〉 = 52.1° ifC < 0. We find at 20 cm 〈β2〉 = 33.9° ifC > 0 and 〈β2〉 = 54.1° ifC < 0. The values at the two wavelengths are equal within the errors, and close to the β2 value obtained earlier at 30 cm (〈β2〉 = 36.4° if C >0 and 〈β2〉 = 49.1° if C < 0). The mean 〈β2〉 for the entire set of data can be taken to be 43.5°. The period dependence of the pulse width W(P) √ P−0.25 differs from the relation that is usually used in the polar-cap model, W(P) √ P−0.5. This difference could be associated with the rate of development of plasma instabilities near the surface of the neutron star (in the region where high-frequency radiation is generated). The role of the quadrupole component of the magnetic field is not important here. There is no dependence of the angle β on the pulsar age (z distance, luminosity L, or characteristic age τ = P/(2dP/dt)) for the studied sample.

Differences in the parameters of radio pulsars with short and long periods

A comparative analysis of various parameters of pulsars with short (P < 0.1 s) and long (P > 0.1 s) periods is carried out. There is no correlation between the radio and gamma-ray luminosities of the pulsars and their surfacemagnetic fields, but there is a correlation between the X-ray luminosity and the surfacemagnetic field. A dependence of the X-ray and gamma-ray luminosities on the magnetic field at the light cylinder is also found. This result provides evidence for the formation of hard, non-thermal emission at the periphery of the magnetosphere. An appreciable positive correlation between the luminosity and the rate of rotational energy loss by the neutron star is observed, supporting the idea that all radio pulsars have the same basic source of energy. The efficiency of the transformation of rotational energy into radiation is significantly higher in long-period pulsars. The dependence of the pulse width on the pulsar period is steeper for pulsars with short periods than for those with long periods. The results obtained support earlier assertions that there are differences in the processes generating the emission in pulsars with P < 0.1 s and those with P > 0.1 s.

The magnetospheric structure of radio pulsars with interpulses

Pulsars with interpulses—pulse components located between the main pulses—are studied. About 50 such objects are currently known. Methods developed earlier to determine the angle β between the rotation axis and the magnetic moment of the neutron star are used to investigate the geometry of the magnetospheres in these objects. In a number of pulsars, β < 20°, so that not only interpulses, but also radiation between pulses and a correlation between the behaviors of the interpulses and main pulses, is expected. In other pulses, this angle is greater than 60°, and interpulses can appear if the radiation cone is sufficiently broad and there is a favorable orientation of the line of sight of the observer. Thus, the earlier prediction that there should be two types of pulsars with interpulses—aligned and orthogonal—is supported. Estimates of the ages of the pulsars in these two groups indicate that aligned rotators are appreciably older than orthogonal rotators.

The radio pulsar J0205+6449 in the supernova remnant 3C 58

AbstractThe detection of pulsed radio emission from the recently discovered X-ray pulsar J0205+6449 in the young supernova remnant 3C 58 is reported together with the results of first studies of this emission. The observations were carried out at 111 and 88 MHz on radio telescopes of the Pushchino Observatory. The pulsar period, 65.68 ms, and period derivative,