The radiation force on small particles

A more complete expression for the radiation force on a small particle in the solar system is given which includes the effect of asymmetry of the thermal reradiation and also of inelastic scattering such as fluorescence. Both the Poynting-Robertson drag and the Yarkovsky effect are affected by such asymmetries and are incorporated into the formalism. For non-spherical particles the direction of the radiation force will no longer coincide with the solar irradiation.     

Effects of solar radiation on the orbits of small particles

Revised equations of motion are formulated on more general assumptions than hitherto making allowance for some reflection of sunlight by a dust-particle, and from these the secular rates of change of the orbital elements of the particle are obtained. The equation for the eccentricity yields numerical results for the time taken for given changes in this element to occur. Other elements turn out to be expressible in terms of the eccentricity and thence are effectively also known in terms of the time. More general forms of earlier results are found, and some new mathematical results in the theory of the process are derived. The time of infall to the Sun associated with almost circular initial motion of a particle is calculated, and also the time from an orbit of initially high eccentricity. In this latter case, infall takes place much more rapidly than from a circular orbit of radius comparable with the average distance in the eccentric orbit. The effect on a particle of a long-period comet during a single return is negligible compared with the change in its binding-energy to the Sun that will in general result from planetary action. The possible history of a dust-particle from original capture by the Sun to final infall to the solar surface is briefly considered.     

Perihelion motion of small irregular dust particles due to radiation forces

Perihelion motion, i.e. a secular change of longitude of perihelion, of interplanetary dust particles is investigated under the action of solar gravity and solar electromagnetic radiation. As for spherical particle [Kla?ka, J., 2004. Electromagnetic radiation and motion of a particle. Cel. Mech. Dynam. Astron. 89, 1-61]: (i) perihelion motion is of the order ( is heliocentric velocity of the meteoroid and c is the speed of light in vacuum), if a component of electromagnetic radiation acceleration is considered as a part of central acceleration; (ii) perihelion motion is of the first order in if the total electromagnetic radiation force is considered as a disturbing force. The new facts presented in this paper concern irregular dust particles. Detailed numerical calculations were performed for the grains ejected at aphelion of comet Encke. Perihelion motion for irregular interplanetary dust particles exists already in the first order in for both cases of central accelerations. Moreover, perihelion motion of irregular particles exhibits both positive and negative directions during the particle orbital motion. Irregularity of the grains causes not only perihelion motion, but also dispersion of the dust in various directions, also normal to the orbital plane of the parent body.     

Investigations of AGNs by the interplanetary scintillation method

This is a brief review of investigations of AGNs by the interplanetary scintillation method made in Pushchino Radio Astronomy Observatory. This revised version was published online in July 2006 with corrections to the Cover Date.     

Extinction and scattering by small planetesimal particles

Computations are presented for the extinction and scattering properties of small planetesimal particles consisting of iron cores and silicate mantles. The possible relevance of such calculations to the observed properties of T Tauri-like stars is discussed.     

Possible nature of cometary atmosphere particles

The polarimetric and spectrophotometric data of observations, the results of laboratory simulations, and theoretical calculations are considered as evidence in favor of the presence of large irregular particles in cometary atmospheres. The attempt is made to define more precisely the particle parameters. In particular, observations of some comets at small phase angles can be interpreted by light scattering on large icy grains. The results of laboratory experiments with ice at low temperatures and pressures are adduced; this can be explain the formation of a large icy grain cloud near the cometary nucleus. Changes of these particles under the effects of solar radiation are considered.     

Compton scattered transition radiation from very high energy particles

X-ray transition radiation can be used to measure the Lorentz factor of relativistic particles. At energies approaching γ=E/mc²=10⁵, transition radiation detectors can be optimized by using thick (5–10 mil) foils with large (5–10 mm) spacings. This implies X-ray energies 100 keV and the use of scintillators as the X-ray detectors. Compton scattering of the X-rays out of the particle beam then becomes an important effect. We discuss the design of very high energy detectors, the use of metal radiator foils rather than the standard plastic foils, inorganic scintillators for detecting Compton scattered transition radiation, and the application to the ACCESS cosmic ray experiment.     

Hawking radiation of Dirac particles via tunneling from a black plane

Extending Kerner and Mann’s fermion tunneling, we investigate the Dirac particle’s tunneling radiation from a black plane in Anti-de Sitter space-time. The result shows that the tunneling probability is related to the change of Bekenstein-Hawking entropy.     

Outflows from AGNs: a brief overview of observations and models

Recent observations show that outflows from Active Galactic Nuclei are much more common than previously thought, with such outflows seen in various wavebands. I review the recent advances in observations of wind signatures and the progress in modelling various wind launching mechanisms.     

Description of accretion induced outflows from ultra-luminous sources to under-luminous AGNs

We study the energetics of the accretion-induced outflow and then plausible jet around black holes/compact objects using a newly developed disc-outflow coupled model. Inter-connecting dynamics of outflow and accretion essentially upholds the conservation laws. The energetics depend strongly on the viscosity parameter $\alpha$ and the cooling factor f which exhibit several interesting features. The bolometric luminosities of ultra-luminous X-ray binaries (e.g. SS433) and family of highly luminous AGNs and quasars can be reproduced by the model under the super-Eddington accretion flows. Under appropriate conditions, low-luminous AGNs (e.g. Sagittarius $A^1$) also fit reasonably well with the luminosity corresponding to a sub-Eddington accretion flow with $f\to 1$.     

On extinction by small graphite,silicate and iron particles

The refractive indices of graphite, silicate and iron, which are believed to be candidates for interstellar dust grains, are shown to exhibit large experimental uncertainties. The Mie scattering theory has been used to demonstrate how errors in the refractive indices are manifested in the extinction curves for small spheres in the wavelength range from 0.1 μm to 2 μm. It is found that the transmitted errors in the extinction curves are wavelength dependent: for graphite, significant errors occur in the far ultraviolet part of the extinction curve; for silicates, in the near ultraviolet; while for iron the error is relatively small in the wavelength range considered.     

Temperature-influenced dynamics of small dust particles

The motion of spherical dust particles under the action of gravity, electromagnetic radiation force and Lorentz force (LF) is studied theoretically for materials with temperature-dependent dielectric functions in the visible (VIS) spectral range. Even a weak variation of the optical constants with heliocentric distance may influence predominately a long-term dynamical behaviour of submicron-sized and small micron-sized dust grains. It is shown that the lifetime of carbonaceous or Si particles may change by several tens of per cent because of the temperature dependence of particle refractive indices. The orbital inclination is the most evident difference between the evolution of a dust particle with temperature-dependent optical properties and one without. While carbonaceous 2-μm-sized particles with optical constants independent of temperature may evolve in orbits with inclinations greater than an initial value, grains of the same size with variable refractive indices will be spread along orbits characterized with inclinations lower than the initial one. Here the temperature works as a separation factor for particles having slightly different temperature dependences of the optical constants.     

Possible evidence for continued ejection of RR telescopii

FeII and [FeII] intensity measures enable the size of the region containing singly ionized iron to be estimated, calculations for a phase near maximum light support a continued ejection model.     

Search for Binary Black Hole Candidates from the VLBI Images of AGNs

We have searched the core-jet pairs in the VLBI scales (<1 kpc), from several VLBI catalogues, and found out 5 possible Binary Black Hole (BBH) candidates. We present here the search results and analyse the candidates preliminarily. We plan to study with multi-band VLBI observation. We also plan to carry out optical line investigation in future.     

Possible evidence for a variable fine-structure constant from QSO absorption lines: systematic errors

Comparison of quasar (QSO) absorption spectra with laboratory spectra allows us to probe possible variations in the fundamental constants over cosmological time-scales. In a companion paper we present an analysis of Keck/HIRES spectra and report possible evidence suggesting that the fine-structure constant, α , may have been smaller in the past:     over the redshift range     . In this paper we describe a comprehensive investigation into possible systematic effects. Most of these do not significantly influence our results. When we correct for those which do produce a significant systematic effect in the data, the deviation of     from zero becomes more significant. We are led increasingly to the interpretation that α was slightly smaller in the past.     

Electromagnetic radiation recoil of a system ofN-charged particles

We give the radiation of anN-charged particles system associated with the succeeding terms in the expansion in the inverse powers of the velocity of light of the four vector force on the material system in a slow motion. We investigate the conditions under which theN-charged particles system may recoil while emitting electromagnetic radiation. Furthermore, the lowest-order secular effects in the radiation arise from dipole and quadrupole radiations exactly as it is expected from the classical theory.