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- Malov, I. F. 2 (%)
- Anand, J D 1 (%)
- Barsukov, D. P. 1 (%)
- Baurov, Yu. A. 1 (%)
- Cherepashchuk, A. M. 1 (%)

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## Measurements of the scattering of pulsar radio emission

### Astronomy Reports (2007-08-01) 51: 615-623 , August 01, 2007

Measurements of the broadening of pulsar pulses by scattering in the interstellar medium are presented for a complete sample of 100 pulsars with Galactic longitudes from 6° to 311° and distances to three kiloparsec. The dependences of the scattering on the dispersion measure (*τ*_{sc}(DM) ∝ DM^{α}), frequency (*τ*_{sc}(*v*) ∝ *v*^{−γ}), Galactic longitude, and distance to the pulsar are analyzed. The dependence of the scattering on the dispersion measure in the near-solar neighbourhood can be represented by the power law *τ*_{sc}(DM) ∝ DM^{2.2±0.1}). Measurements at the low frequencies 111, 60, and 40 MHz and literature data are used to derive the frequency dependence of the scattering (*τ*_{sc}(*v*) ∝ *V*^{−γ}) over a wide frequency interval (covering a range of less than 10: 1) with no fewer than five frequencies. The index for the frequency dependence, *γ* = 4.1 ± 0.3, corresponds to a normal distribution for inhomogeneities in the turbulence in the scattering medium. Based on an analysis of the dependence of the scattering on the distance to the pulsar and on Galactic longitude, on average, the turbulence level *C*_{n}^{2}
is the same in all directions and at all distances out to about three kpc, testifying to the statistical homogeneity of the turbulence of the scattering medium in the near-solar region of the Galaxy.

## The pulsar PSR B1931+24 as an orthogonal rotator

### Astronomy Reports (2007-06-01) 51: 477-480 , June 01, 2007

The angles of the magnetic moment *µ* and the line of sight *L* to the rotation axis *Ω* are estimated for the pulsar PSR B1921+24, which displays “on” and “off” periods in its radio emission. It is shown that this object is an orthogonal rotator, i.e., the angle *β* between *µ* and *Ω* is equal to 88°.2 and the angle between *L* and *Ω* is ζ = 98.7°, and that its rotation period should be twice the usually adopted value (*P* = 1.626 s). One possible reason for the peculiarities of this pulsar could be the precession of a relic disk in the equatorial region of the object. Further observations (in particular, in the infrared) are required to confirm the existence of such a disk. Polarization data for other pulsars whose radiation switches on and off (transients) are also required, to determine if they are likewise orthogonal rotators. Calculations for PSR B0656+14 show that *β* ∼ 20°, and the sharp increase of its pulse intensities is due to intrinsic reasons, and is not associated with a relic disk.

## Three-dimensional explosion dynamics of a critical-mass neutron star (in a binary)

### Astronomy Letters (2007-07-01) 33: 468-480 , July 01, 2007

In a close neutron star binary resulting from the collapse of the rotating iron core of a collapsing supernova, the low-mass component of mass *m* undergoes explosive disruption at the final evolutionary stage of this binary. We have obtained a numerical solution for the three-dimensional dynamics of 0.1 *M*_{⊙} iron ejecta with energy release 4.7 MeV per nucleon in the gravitational field of a massive neutron star with mass *M*. The numerical solution has been obtained by the method of particles, which is adequate for a collisionless description of the ejecta dynamics in the absence of an interstellar medium. As a test problem, the suggested model is compared with the well-known asymptotic solution (for *m/M* → 0), which we have also been able to slightly improve and extend. We analyze in detail the separation of the ejecta into two categories of particles with hyperbolic and elliptical orbits. We have been able to obtain a number of corollaries from the analytical solution. These have allowed us to estimate the kinetic energy of the ejecta as a function of the binary component mass ratio and the final pulsar velocity by applying the momentum conservation law in the pulsar—ejecta system. Further use of our calculations is promising for the formulation of initial conditions for the three-dimensional hydrodynamic problem of the collision of ejecta with presupernova shells, in particular, with the toroidal iron atmosphere obtained previously in our two-dimensional calculations of the collapse of a rotating stellar core.

## Irregularity in the period of the pulsar B1822-09

### Astronomy Reports (2007-09-01) 51: 746-755 , September 01, 2007

The results of long-term monitoring of irregularies in the rotation rate of the pulsar B1822-09 (J1825-0935) are presented. Observations of the pulsar carried out since 1991 on the Large Phased Array of the Pushchino Radio Astronomy Observatory have revealed a new type of irregularity in the rotation, which has the form of “slow glitches” and is manifest as a gradual exponential growth in the rotation frequency of the star over several hundred days. In 1995–2004, five slow glitches in the rotation frequency were observed, with relative amplitudes of Δ*ν/ν* ∼ (2.5-32) × 10^{−9}. Together with these unusual “slow glitches” in the rotation frequency, two modest ordinary glitches, associated with sudden, jump-like increases in the rotation frequency, were also observed. The observed irregularities in the rotation frequency of the pulsar are analyzed in detail, and possible interpretations of the results are discussed.

## Bulk viscosity of strange quark matter in density dependent quark mass model

### Pramana (2000-05-01) 54: 737-749 , May 01, 2000

We have studied the bulk viscosity of strange quark matter in the density dependent quark mass model (DDQM) and compared results with calculations done earlier in the MIT bag model where *u, d* masses were neglected and first order interactions were taken into account. We find that at low temperatures and high relative perturbations, the bulk viscosity is higher by 2 to 3 orders of magnitude while at low perturbations the enhancement is by 1–2 order of magnitude as compared to earlier results. Also the damping time is 2–3 orders of magnitude lower implying that the star reaches stability much earlier than in MIT bag model calculations.

## The distribution of space velocities of radio pulsars

### Astronomy Reports (2007-10-01) 51: 830-835 , October 01, 2007

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* < 10^{10} G is 108 km/s, while 〈*V*〉 = 340 km/s for *B* > 10^{10} G. These results must be taken into account when identifying a mechanism to explain the observed pulsar velocities and their anisotropy.

## A study of the X-ray pulsars X1845-024 and XTE J1858+034 based on INTEGRAL observations

### Astronomy Reports (2008-02-01) 52: 138-151 , February 01, 2008

We present an analysis of observations of the relatively unstudied X-ray pulsars X1845-024 and XTE J1858+034 carried out from May 2003 through November 2004 using the JEM-X and IBIS telescopes of the INTEGRAL international gamma-ray observatory at energies of 5-70 keV. The X-ray spectra and light curves of the pulsars are constructed. During the observation period, outbursts at 18-70 keV at levels of 13 mCrab and 111 mCrab were detected for X1845-024 and XTE J1858+034, respectively. We refined the rotational period of the neutron star in XTE J1858+034 (220.4 s), measured its acceleration during the outburst, and derived a probable value of the orbital period (≃380 d).

## Long-period variations of pulsar emission and the dynamical ellipticity of neutron stars

### Astronomy Reports (2008-01-01) 52: 61-69 , January 01, 2008

Assuming that the observed periodic variations of pulsar emission are due to the free precession of the spin axis, we investigate the evolution of the rotation of a two-layer neutron star using the Hamiltonian method of Getino. We model the dynamical characteristics of a rotating neutron star using the observed variations of the emission of seven pulsars. We estimate the dependence of the period of the Chandler wobble, the period of precession of the spin axis, and the dynamical ellipticity of a neutron star on the model used to describe the super-dense neutron matter and the mass of the star.

## Curvature and non-resonance Compton gamma-ray emission of a radio pulsar with a non-dipolar magnetic field

### Astronomy Reports (2007-06-01) 51: 469-476 , June 01, 2007

We consider the influence of a non-dipolar magnetic field on the gamma-ray emission from the polar regions of a radio pulsar. The pulsar is treated in a Goldreich-Julian model with a free flow of charge from the surface of the neutron star. When finding the intensity of the gamma-ray radiation of the pulsar tube, both curvature gamma-ray radiation from the primary electrons and non-resonance inverse Compton scattering of thermal photons from the polar cap on primary electrons are taken into account. When finding the height of the upper plate of the pulsar diode, we included only positrons created by the curvature radiation of primary electrons. We assumed that the polar cap is heated by the return positron current. The influence on the gamma-ray emission of variations in both the radius of curvature of the magnetic force lines and in the electric field due to the non-dipolarity of the magnetic field were taken into account. The presence of even weak non-dipolarity of the magnetic field leads to a sharp decrease in the intensity of the gamma-ray emission from the pulsar tube at energies 1–100 MeV, while the intensity of the inverse Compton radiation (at energies 1–100 GeV) varies only relatively weakly.

## Electron-positron plasma generation in a magnetar magnetosphere

### Astronomy Letters (2007-10-01) 33: 660-672 , October 01, 2007

We consider the electron—positron plasma generation processes in the magnetospheres of magnetars—neutron stars with strong surface magnetic fields, *B* ≃ 10^{14}–10^{15} G. We show that the photon splitting in a magnetic field, which is effective at large field strengths, does not lead to the suppression of plasma multiplication, but manifests itself in a high polarization of γ-ray photons. A high magnetic field strength does not give rise to the second generation of particles produced by synchrotron photons. However, the density of the first-generation particles produced by curvature photons in the magnetospheres of magnetars can exceed the density of the same particles in the magnetospheres of ordinary radio pulsars. The plasma generation inefficiency can be attributed only to slow magnetar rotation, which causes the energy range of the produced particles to narrow. We have found a boundary in the
$$
P - \dot P
$$
diagram that defines the plasma generation threshold in a magnetar magnetosphere.