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11.
The effect of the radius of the tube of open magnetic-field lines on the gamma-ray curvature radiation from the polar regions of a radio pulsar with a non-dipolar magnetic field is analyzed. The pulsar is considered in a polar-cap model with free electron emission from the neutron-star surface. The effect of the non-dipolar magnetic field on the radius of curvature of the field lines and the field intensity is taken into account. In connection with the creation of electron-positron pairs, we take into account only the birth of pairs by curvature radiation in the magnetic field. The small non-dipolarity of the field enables the radio pulsar not to turn off, even after a considerable decrease in the pulsar-tube radius. For instance, with a 20% non-dipolarity (ν = 0.2), a pulsar with B = 1013 G and P = 0.5 s can still operate even for a fivefold decrease in the pulsar-tube radius. A maximum is observed in the dependence of the electrostatic potential in the diode on the non-dipolarity parameter ν at ν ～ 0.5–0.7. The pulse profile in non-thermal X-ray emission for ν ～ 0.5–0.7 may look virtually the same as for ν ～ 0.1–0.2. Decreases in the pulsar-tube radius could be due to a structure of currents in the magnetosphere that results in the pulsar diode on the neutron-star surface occupying only a small fraction of the pulsar tube, with the remainder of the tube containing an outer annular gap. The pulsar-tube size is also affected by the presence of a circum-pulsar disk. A change in the pulsar-tube radius could also be due to an external magnetic field, associated with either a magnetic white dwarf or a circum-pulsar disk. 相似文献
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13.
The evolution of the angle between the magnetic moment and rotation axis of radio pulsars (inclination angle) is considered taking into account the presence of a non-dipolar magnetic field at the neutron-star surface and superfluid neutrons in the stellar interior. It is assumed that the total loss of angular momentum by the pulsar can be represented as a sum of magnetodipole and current losses. The neutron star is treated as a two-component system consisting of a charged component (including protons and electrons, as well as the crust, which is rigidly coupled with them, and normal neutrons) and a superfluid core. The components interact through scattering of degenerate electrons on magnetized Feynman-Onsager vortices. If a superfluid core is absent, then, in spite of the presence of stable equilibrium inclination angles, the rate with which these are reached is so slow that most pulsars do not have sufficient time to approach them during their lifetimes. The presence of superfluid neutrons results, first, in faster evolution of the inclination angle and, second, in the final stage of the evolution being either an orthogonal or a coaxial state. The proposed model fits the observations better in the case of small superfluid cores. 相似文献
14.
We adopt that in the interior of neutron stars both the proton and neutron superfluids are in the vortex state. Thus, in the superconducting core the magnetic field is expected to be organized in the form of quantized fluxoids. It is shown that fluxoids are buoyant. This gives rise to a rapid (5×104 yr) expulsion of the magnetic field out of the superconducting core to the subcrustal region, and a subsequent decay within the outer crust. The effect considered may be the physical reason why the characteristic decay-time of pulsar magnetic fields (106 yr) corresponds to the ohmic dissipation time within the neutron star crust. The intersection of two types of vortex lines with each other and its possible consequence for pulsars is briefly discussed. 相似文献
15.
The influence of an axisymmetric magnetic field on the intensity, spectrum, and shape of a pulse of gamma-ray curvature radiation from the polar regions of a radio pulsar is investigated. The pulsar is considered in a Goldreich-Julian model with a free-electron emission from the neutron-star surface. The influence on the curvature radiation of variations of both the curvature of the magnetic field lines and the electric field due to the nondipolarity of the magnetic field are investigated. The presence of even modest nondipolarity (less than 10%) can lead to a sharp drop in the intensity of the gamma-ray curvature radiation, while the intensity of the X-ray curvature radiation (photon energies <100 keV) is affected only weakly. 相似文献
16.
The accretion of neutral gas (hydrogen and helium) onto a neutron star is studied. The gas is gravitationally captured into the magnetosphere of the star, where it is ionized by thermal radiation from the stellar surface and accelerated by the electric field at the light cylinder and in a tube of open magnetic lines. Particles accelerated at light cylinder generate gamma-ray, some particles move to the star and heat its polar regions, resulting in the emission of X-rays. Our calculations of the model parameters of the X-ray and gamma-ray radiation indicate that the radiation intensities should be sufficient to be observed. 相似文献
17.
A. I. Tsygan 《Astronomy Letters》2017,43(12):820-830
The X-ray luminosity and temperature of the polar cap heated by the back flux of positrons from a radio pulsar with a period P ～ 1 s and a magnetic field B ~ 1012 G have been estimated. An additional source of X-ray emission—a thin, hotter semiring on the polar-cap periphery—is shown to also exist. It is heated by the back flux of electrons from the light cylinder. Furthermore, the electric field near the hot semiring accelerates the ions of the surface layer that leave the neutron-star magnetosphere. The semiring area is smaller than the polar-cap area approximately by a factor of 100, i.e., at the same luminosity the temperature is higher by a factor of 3. The observed X-ray emission from old radio pulsars is the emission from thin hot polar-cap semirings. The emission from the polar caps themselves is strongly attenuated by interstellar absorption. 相似文献
18.
The reverse positron current flowing through the inner gap of an old radio pulsar in the presence of a small-scale magnetic field is found. Computations for the case of both strong and weak screening of the longitudinal electric field by the electron–positron plasma are presented. 相似文献
19.
We investigate the orientation of the orbital planes of X-ray binary systems relative to the direction of the additional velocity acquired by the binary in a supernova explosion or as a result of radiative acceleration. In the second case, the acceleration occurs due to X-ray radiation during a stage of intense accretion onto the neutron star, which has an asymmetric magnetic field. Observational consequences that could enable estimation of the role of each acceleration mechanism are discussed. The results are also applicable to binary millisecond radio pulsars, assuming that they have gone through an accretion stage. 相似文献
20.
It is shown that, when angular-momentum losses of a radio pulsar are represented as a sum of magnetic-dipole and current losses,
the angle between the magnetic moment and rotation axis of the radio pulsar tends to some equilibrium value (near 45°). This
process takes place on a timescale of the order of the pulsar’s characteristic age. Taking into account the non-dipolarity
of the pulsar’s magnetic field changes this equilibrium angle. 相似文献