Magnetic torques between accretion discs and stars

I show in this paper that two types of magnetic torques can appear in the interaction between an accretion disc and a magnetic accretor. There is the well-known torque resulting from the difference in angular velocity between the accretion disc and the star, but in addition there is a torque coming from the interaction between the stellar magnetic field and the disc's own magnetic field. The latter form of magnetic torque decreases in strength more slowly with increasing radius, and will therefore dominate at large radii. The direction of the disc field is not determined by the difference in angular velocity between the star and the disc as in the Ghosh &38; Lamb model, but rather is a free parameter. The magnetic torque may therefore either spin up or spin down the star, and the torque changes sign if the magnetic field in the disc reverses. I suggest that this mechanism can explain the torque reversals that have been observed in some disc-fed X-ray pulsars.     

Measurement of fluid contents and wetting front profiles by real-time neutron radiography

Few methods exist for measuring rapidly changing fluid contents at the pore scale that simultaneously allow whole flow field visualization. We present a method for using real-time neutron radiography to measure rapidly changing moisture profiles in porous media. The imaging technique monitors the attenuation of a thermal neutron beam as it traverses a flow field and provides measurements every 30 ms with an image area >410 cm² and a spatial resolution 0.05 cm. The technique is illustrated by measuring the variation in moisture content across a wetting front moving at constant velocity through SiO₂ sand. The relative contributions of the hydraulic conductivity and diffusivity terms in Richards' equation to the total fluid flux within the wetting front region were also measured. The diffusivity was found to rise from zero to a peak value within the wetting front region before falling off while the conductivity was found to rise monotonically. The reliability of the technique was checked via mass balance.     

地震波实时处理系统在自贡台网地震速报中的应用分析

着重介绍了自贡地震台网地震波实时处理系统在地震速报中的作用，并利用台网1997－2001年地震速报资料，统计分析了发震时刻、震中位置、震级及速报速度等，在地震波实时处理系统参与后，自贡台网速报质量均有大幅度的提高。     

Accretion by a Neutron Star Moving at a High Kick Velocity in the Supernova Ejecta

1 INTRODUCTION The classical problem of spherical accretion onto a compact object, e.g., a black hole or a neutron star (NS), has been studied by many authors. A hydrodynamical solution was presented by Bondi 1952, who showed that inside a certain capture…     

On the neutron star–disc interaction in Be/X-ray binaries

We have investigated the long-term X-ray variability, defined as the root-mean-square (rms) of the All Sky Monitor Rossi X-ray Timing Explorer (ASM RXTE ) light curves, of a set of galactic Be/X-ray binaries and searched for correlations with system parameters, such as the spin period of the neutron star and the orbital period and eccentricity of the binary. We find that systems with larger rms are those harbouring fast-rotating neutron stars, low eccentric and narrow orbits. These relationships can be explained as the result of the truncation of the circumstellar disc. We also present an updated version of the Hα equivalent width–orbital period diagram, including sources in the Small Magellanic Cloud (SMC). This diagram provides strong observational evidence of the interaction of neutron star with the circumstellar envelope of its massive companion.     

Improbability of DUrca Process Constraints EOS

According to recent observational and theoretical progresses,the DUrca process (direct Urca process) may be excluded from the category of neutron star cooling mechanisms. This result,combinedwith the latest nuclear symmetry energy experiments,will provideus an independent way of testing the EOS (equation of state) for supernuclear density. For example,soft EOSs,such as FPS,will probably be excluded.     

Slow glitches in the pulsar B1822-09

The pulsar B1822-09 (J1825-0935) experienced a series of five unusual, slow glitches over the 1995–2004 interval. The results of further study of this unusual glitch phenomenon are presented. It is also reported the detection a new glitch of typical signature that occurred in the pulsar period in 2006 January.