Space-Time Description of Scalar Particle Creation by a Homogeneous Isotropic Gravitational Field

We give the generalization of the method of the space-time description of particle creation by a gravitational field for a scalar field with nonconformal coupling to the curvature. The space-time correlation function is obtained for a created pair of the quasi-particles, corresponding to a diagonal form of the instantaneous Hamiltonian. The case of an adiabatic change of the metric of homogeneous isotropic space is analyzed. We show that the created pairs of quasi-particles in de Sitter space should be interpreted as pairs of virtual particles.Comment: 7 pages, 3 figure

Equation of State for Water in the Small Compressibility Region

The equation of state for dense fluids has been derived within the framework of the Sutherland and Katz potential models. The equation quantitatively agrees with experimental data on the isothermal compression of water under extrapolation into the high pressure region. It establishes an explicit relationship between the thermodynamic experimental data and the effective parameters of the molecular potential

Polarization of Thermal X-rays from Isolated Neutron Stars

Since the opacity of a magnetized plasma depends on polarization of radiation, the radiation emergent from atmospheres of neutron stars with strong magnetic fields is expected to be strongly polarized. The degree of linear polarization, typically ~10-30%, depends on photon energy, effective temperature and magnetic field. The spectrum of polarization is more sensitive to the magnetic field than the spectrum of intensity. Both the degree of polarization and the position angle vary with the neutron star rotation period so that the shape of polarization pulse profiles depends on the orientation of the rotational and magnetic axes. Moreover, as the polarization is substantially modified by the general relativistic effects, observations of polarization of X-ray radiation from isolated neutron stars provide a new method for evaluating the mass-to-radius ratio of these objects, which is particularly important for elucidating the properties of the superdense matter in the neutron star interiors.Comment: 7 figures, to be published in Ap

GEMINGA'S SOFT X-RAY EMISSION AND THE STRUCTURE OF ITS SURFACE

We present a model to explain the decrease in the amplitude of the pulse profile with increasing energy observed in Geminga's soft X-ray surface thermal emission. We assume the presence of plates surrounded by a surface with very distinct physical properties: these two regions emit spectra of very distinct shapes which present a crossover, the warm plates emitting a softer spectrum than the colder surrounding surface. The strongly pulsed emission from the plates dominates at low energy while the surroundings emission dominates at high energy, producing naturally a strong decrease in the pulsed fraction. In our illustrative example the plates are assumed to be magnetized while the rest of the surface is field free. This plate structure may be seen as a schematic representation of a continuous but very nonuniform distribution of the surface magnetic field or as a quasi realistic structure induced by past tectonic activity on Geminga.Comment: 10 pages, AASTeX latex, + 3 figures (compressed 7 uuencoded). Submitted to Ap. J. Let

Classification of integrable hydrodynamic chains and generating functions of conservation laws

New approach to classification of integrable hydrodynamic chains is established. Generating functions of conservation laws are classified by the method of hydrodynamic reductions. N parametric family of explicit hydrodynamic reductions allows to reconstruct corresponding hydrodynamic chains. Plenty new hydrodynamic chains are found

The Pulsar B2224+65 and Its Jets: A Two Epoch X-ray Analysis

We present an X-ray morphological and spectroscopic study of the pulsar B2224+65 and its apparent jet-like X-ray features based on two epoch Chandra observations. The main X-ray feature, which shows a large directional offset from the ram-pressure confined pulsar wind nebula (Guitar Nebula), is broader in apparent width and shows evidence for spectral hardening (at 95 percent confidence) in the second epoch compared to the first. Furthermore, the sharp leading edge of the feature is found to have a proper motion consistent with that of the pulsar (~180 mas yr-1). The combined data set also provides evidence for the presence of a counter feature, albeit substantially fainter and shorter than the main one. Additional spectral trends along the major and minor axes of the feature are only marginally detected in the two epoch data, including softening counter to the direction of proper motion. Possible explanations for the X-ray features include diffuse energetic particles being confined by an organized ambient magnetic field as well as a simple ballistic jet interpretation; however, the former may have difficulty in explaining observed spectral trends between epochs and along the feature's major axis whereas the latter may struggle to elucidate its linearity. Given the low counting statistics available in the two epoch observations, it remains difficult to determine a physical production scenario for these enigmatic X-ray emitting features with any certainty.Comment: 9 pages, 6 figures, submitted to MNRAS; updated as per reviewer comment

Equation of state and opacities for hydrogen atmospheres of magnetars

The equation of state and radiative opacities of partially ionized, strongly magnetized hydrogen plasmas, presented in a previous paper [ApJ 585, 955 (2003), astro-ph/0212062] for the magnetic field strengths 8.e11 G < B < 3.e13 G, are extended to the field strengths 3.e13 G < B < 1.e15 G, relevant for magnetars. The first- and second-order thermodynamic functions and radiative opacities are calculated and tabulated for 5.e5 < T < 4.e7 K in a wide range of densities. We show that bound-free transitions give an important contribution to the opacities in the considered range of B in the outer neutron-star atmosphere layers. Unlike the case of weaker fields, bound-bound transitions are unimportant.Comment: 7 pages, 6 figures, LaTeX using emulateapj.cls (included). Accepted by Ap