Astronomy Letters-A Journal of Astronomy and Space Astrophysics最新文献

We propose a universal approximation of the equation of state of superdense matter in neutron star (NS) interiors. It contains only two parameters, the pressure and the density at the center of the maximally massive neutron star. We demonstrate the validity of this approximation for a wide range of different types of equations of state, including both baryonic and hybrid models. Combined with recently discovered correlations of internal (density, pressure, and speed of sound at the center) and external (mass, radius) properties of a maximally massive neutron star, this approximation turns out to be an effective tool for determining the equation of state of superdense matter using astrophysical observations.

We consider the evolutionary status of the recently discovered long-period radio sources PSR J0901-4046, GLEAM-X J1627-52, and GPM J1839-10. It is hypothesized that all three sources are radio pulsars. Within the framework of standard scenarios, it is thought that for the pulsar mechanism to operate, it is necessary to exclude the penetration of external matter into the light cylinder, which corresponds to the ejector stage. We show that for realistic properties of the interstellar medium the 76-second pulsar J0901-4046 must be at this stage, whereas the sources GLEAM-X J1627-52 and GPM J1839-10 with periods ({gtrsim}1000) s can be at this stage only in the case of unrealistically high dipolar magnetic fields ({gtrsim}10^{16}) G. We also show that sources with periods ({sim}100) s and magnetic fields ({lesssim}10^{13}) G cannot be ejectors in a realistic interstellar medium. Thus, we predict that long-period radio pulsars with standard magnetic fields will not be discovered.

We have analyzed the results of our observations of the millisecond pulsar B0329+54 (J0332+5434), which exhibits quasi-periodic variations in the barycentric times of arrival (TOAs) of pulses on long time scales. We have tested the hypothesis about the existence of a planet with a mass close to the mass of the terrestrial planets and an orbital period of 27.8 yr around this pulsar that was proposed previously to explain the variations in its TOAs. We show that this hypothesis is not confirmed when considering the series of TOA residuals over the entire available time interval of observations 1968–2022 and that the TOA variations for this pulsar apparently have a different physical cause.

The detection of radio emission from the gamma-ray pulsar J1836+5925 is reported. Rare events of radio emission from this object have been recorded with the LPA radio telescope at the Pushchino Radio Astronomy Observatory. A two- or three-component integrated profile and very narrow individual pulses are a peculiarity of the radio emission from the pulsar J1836+5925. The presence of an interpulse is also possible. We have measured the dispersion measure, (DM=23pm 1) pc cm({}^{-3}), and estimated the distance to the pulsar, 1.5 kpc. The flux density and the lower limit on the spectral index have been estimated.

In pulsating X-ray sources a magnetized neutron star is surrounded by an accretion disk whose structure requires a study. In particular, the dipole magnetic field of the star can partially penetrate the disk and, freezing into the matter, can give rise to an induced magnetic field in the disk. The field growth can be limited by its turbulent diffusion. In this paper we calculate such an induced field. The problem is reduced to solving the induction equation in the presence of diffusion. An analytical solution of the equation has been obtained, with the radial and vertical structures of the induced field having been calculated simultaneously. The radial structure is close to the previously predicted dependence on the difference of the angular velocities of the disk and the magnetosphere: (bproptoOmega_{textrm{s}}-Omega_{textrm{k}}), while the vertical structure of the field is close to the linear proportionality between the field and the height above the equator: (bpropto z). The possibility of the existence of nonstationary quasi-periodic components of the induced magnetic field is discussed.

We consider the influence of space curvature in the Schwarzschild metric on the contribution of the magnetic field outside the neutron star to the moment of inertia of a radio pulsar. Our consideration is restricted only to the simplest configuration of the magnetic field, when it can be described by only one harmonic. We show that at a fixed magnetic field strength on the stellar surface the influence of space curvature reduces the contribution of the magnetic field outside the star to the departure of the inertia tensor from the spherical one several-fold.

We have searched for pulse emission at 111 MHz toward 116 RRAT candidates. For our search we used the archival data obtained at the meridian 128-beam Large Phased Array radio telescope. About six days of observations in an interval of eight years were accumulated for each candidate. Eleven new RRATs were detected. We managed to estimate the periods for six of them and to construct the average profiles for four RRATs. Some of the candidates turned out to be known pulsars observed in the side lobes of the radio telescope and interference. For some of the candidates we failed to find any pulses with a signal-to-noise ratio greater than seven, and their nature remains unknown.

A self-consistent radiation-hydrodynamics model of an accretion channel of subcritical X-ray pulsars is constructed. The influence of the presence of resonance in the scattering cross-section on the accretion process and radiation transfer is taken into account. It is shown that the efficiency of plasma deceleration by radiation depends on the magnitude of the magnetic field (B). For (B=1.7times 10^{12}) G, the spectra and the degree of linear polarization of the radiation of the accretion channel are constructed. In the obtained spectra, the shape of the cyclotron line depends on the direction of the outgoing radiation. The calculated linear polarization degree of the outgoing radiation is (30{-}40%) near the cyclotron resonance, whereas it can be small (({lesssim}5{-}10%)) at energies significantly lower than the resonant one.

Gamma-ray bursts (GRBs) are the phenomena of rapid energy release of enormous power associated with the collapse or merging of stars. As a result of internal processes, populations of nonthermal accelerated particles radiating in a wide energy range are formed in them. A number of observations have shown that photons with energies up to tens of TeV are detected from some GRBs. However, due to the great energy losses of radiating particles, the explanation of this high-energy radiation in terms of standard radiation mechanisms runs into great difficulties. In this paper, based on the model of adiabatic expansion for the GRB afterglow phase, we investigate the influence of magnetic inhomogeneities on the spectra within the electron and proton synchrotron radiation mechanism by taking into account the Compton scattering of synchrotron photons. We show that the magnetic inhomogeneity effect can increase the maximum energies of the synchrotron radiation from electrons and protons several fold without affecting the maximum energies of the Compton photons being produced in the Klein–Nishina regime.

The orbital motion of a spacecraft with a solar sail in the vicinity of the Sun–Earth collinear libration point is studied. The study is carried out within the Hill approximation of the circular restricted three-body problem. The collinear libration point is unstable, but instability can be a positive factor in the tasks of maneuvering in interplanetary space. This is because a small change in velocity near an unstable libration point can lead to a significant change in orbital motion. This property can be used in the development of projects to counteract the comet–asteroid hazard. A scheme for constructing the trajectories of interception of a spacecraft with a potentially hazardous object is proposed. One of the stages of this scheme, an optimal escape from the vicinity of the libration point using light pressure forces, is considered. The results of numerical simulations are presented.