Searching for the Parent of the Tunguska Cosmic Body

We present the results of an extensive study of the Tunguska Cosmic Body (TCB) origin on dynamical grounds. To identify the TCB parent, or a plausible candidate, we applied the well-known concept of dynamical similarity whereby we have compared the geocentric and heliocentric dynamical parameters of a selected set of the Near Earth Objects (NEOs) and TCB particles. First, we made use the idea of Kresak by comparing geocentric coordinates of the TCB radiant with those of the NEOs. Second, we studied the long-term dynamical evolution of all NEOs and TCB particles searching for similarities between their heliocentric orbits. As a general result, we observed many more similar cases and a different pattern of the high orbital similarity among the TCB particles and the asteroid orbits than we did for comets.     

Validity of Power Law for the Distribution of Intensity of Radio Bursts

The intensity distribution of solar radio bursts observed in the frequency band 0.245–17 GHz has heen derived statistically. The distribution law has been found to be quite different from that of a power law as reported by earlier workers. This distribution leads to the error function, when the total number of bursts in any intensity range is found out. The generalized distribution law can be approximated to the power law only in the frequency band 0.65–2.8 GHz.     

On the Possibility of a Finite Model Describing the Universe

In his book “The expanding universe” EDDINGTON (1933) suggested the idea of an astronomical world model containing a finite number of material particles. Starting from this idea the author has speculated about the possibility to create a cosmological model where in addition also the number of geometrical points and time-instants is finite (JÄRNEFELT 1929, 1949, 1951, 1954a, 1954b, 1957, 1964, 1974, JÄRNEFELT and KUSTAANHEIMO 1952, JÄRNEFELT and QVIST 1955). The ultimate goal would be a world model based essentially upon GALOIS fields. In order to explore such a possibility the most simple actually existing physical system, the structure describing a non-relativistic free particle in an one-dimensional Euclidean space, is treated here. A discrete representation of this system is outlined and then a GALOIS -finitization of this platform is discussed. The author suggests that the method presented here for a very special case, could be generalizable and finally extended to a cosmological model.     

On the Power Distribution of Solar p MODES

We present a simple idealized model of stochastically forced solar oscillations, and compare the distribution function of energy, averaged over 12-hour intervals, with that of low-degree solar modes. We find that the simulated energy distribution is similar to the observations, except at extremely high energy.     

The Common Cutoff Energy of Non-Thermal Electrons with Power Law Distribution

The linear correlation between the logarithm of the total density and the energy index with a negative coefficient is proven as the necessary condition for the cross of the power law distribution lines or the common cutoff energy of the non-thermal electrons responsible for synchrotron and bremsstrahlung radiations. The statistical results calculated from atypical solar microwave burst shows a positive correlation coefficient, which is just opposite to the necessary condition. Therefore, the common cutoff energy does not exist in this event. This revised version was published online in July 2006 with corrections to the Cover Date.     

The Asymptotic Longitudinal Cosmic Ray Intensity Distribution as a Precursor of Forbush Decreases

Identifying the precursors (pre-increases or pre-decreases) of a geomagnetic storm or a Forbush decrease is of great importance since they can forecast and warn of oncoming space weather effects. A wide investigation using 93 events which occurred in the period from 1967 to 2006 with an anisotropy A _xy >1.2% has been conducted. Twenty-seven of the events revealed clear signs of precursors and were classified into three categories. Here we present one of the aforementioned groups, including five Forbush decreases (24 June 1980, 28 October 2000, 17 August 2001, 23 April 2002, and 10 May 2002). Apart from hourly cosmic ray intensity data, provided by the worldwide network of neutron monitor stations, data on solar flares, solar wind speed, geomagnetic indices (Kp and Dst), and interplanetary magnetic field were used for the analysis of the examined cosmic ray intensity decreases. The asymptotic longitudinal cosmic ray distribution diagrams were plotted using the “ring of stations” method. Results reveal a long pre-decrease up to 24 hours before the shock arrival in a narrow longitudinal zone from 90° to 180°.     

Isotopic-geochemical study of nitrogen and carbon in peat from the Tunguska Cosmic Body explosion site

Isotopic-geochemical investigations were carried out on peat samples from the 1908 Tunguska Cosmic Body (TCB) explosion area. We analyzed two peat columns from the Northern peat bog, sampled in 1998, and from the Raketka peat bog, sampled during the 1999 Italian expedition, both located near the epicenter of the TCB explosion area. At the depth of the “catastrophic” layer, formed in 1908, and deeper, one can observe shifts in the isotopic composition of nitrogen (up to Δ¹⁵N = +7.2‰) and carbon (up to Δ¹³C = +2‰) and also an increase in the nitrogen concentration compared to those in the normal, upper layers, unaffected by the Tunguska event. One possible explanation for these effects could be the presence of nitrogen and carbon from TCB material and from acid rains, following the TCB explosion, in the “catastrophic” and “precatastrophic” layers of peat. We found that the highest quantity of isotopically heavy nitrogen fell near the explosion epicenter and along the TCB trajectory. It is calculated that 200,000 tons of nitrogen fell over the area of devastated forest, i.e., only about 30% of the value calculated by Rasmussen et al. (1984). This discrepancy is probably caused by part of the nitrogen having dispersed in the Earth’s atmosphere. The isotopic effects observed in the peat agree with the results of previous investigations [Kolesnikov et al 1998a], [Kolesnikov et al 1998b], [Kolesnikov et al 1999] and [Rasmussen et al 1999] and also with the increased content of iridium and other platinoids found in the corresponding peat layers of other columns [Hou et al 1998] and [Hou et al 2000]. These data favor the hypothesis of a cosmochemical origin of the isotopic effects.     

On the Modeling of the Disruption of Cosmic Bodies at High-Speed Impacts

The results of the experimental study of the interaction of polyethylene impactors with a massive flat organic-glass target are presented. The impactor speed ranged from 3.2 to 5.84 km/s. A statistical analysis of the mass and size distributions of fragments of the impact and chop craters of the target is done. As a result, some scaling relations are established for the geometric size of the craters, the cumulative ejected mass, the mass of the largest fragment ejected from the impact crater, and for the dust mass. The mass distribution of the impact-crater fragments is shown to obey a power law and agrees well with other authors" data for some materials. The critical impact energy _k , resulting in the catastrophic disruption of the target into individual fragments, is estimated. For organic glass, the value of _k is found to be 4 × 10⁴J/kg. The mass of the largest (central) fragment accounts for 27 to 33% of the overall mass ejected from the impact crater. The use of the parameter ₃= _p / _p v ² ₀gives the best fit to the observational data for the masses released from the impact and chop craters.     

Measurement of a Peak in the Cosmic Microwave Background Power Spectrum from the North American Test Flight of Boomerang

We describe a measurement of the angular power spectrum of anisotropies in the cosmic microwave background (CMB) at scales of 0&fdg;3 to 5 degrees from the North American test flight of the Boomerang experiment. Boomerang is a balloon-borne telescope with a bolometric receiver designed to map CMB anisotropies on a long-duration balloon flight. During a 6 hr test flight of a prototype system in 1997, we mapped more than 200 deg(2) at high Galactic latitudes in two bands centered at 90 and 150 GHz with a resolution of 26&arcmin; and 16&farcm;5 FWHM, respectively. Analysis of the maps gives a power spectrum with a peak at angular scales of 1 degrees with an amplitude 70 μK(CMB).     

Gravitational waves as a source for the polarization of the Cosmic Microwave Background

The polarization of the Cosmic Microwave Background (CMB) induced by gravitational waves (GWs) is studied by solving in a semi-analytical way the Chandrasekhar radiative transfer equation; following the Polnarev approach, the equation is written as a second-kind Volterra integral equation and its kernel is handled by performing a series expansion of the trigonometric functions it contains. In this way, a recursive calculation of the Volterra equation gets possible and the polarizing effect of the gravitational waves can be brought out.The polarization degree of the CMB coming from this analysis shows a peak for a wavenumber corresponding to GWs re-entering the horizon at the end of the recombination epoch: the position and the size of the maximum are in agreement with the results of other works, based on a totally numerical calculation. However, a difference quite relevant can be remarked when one looks at the shape of the polarization plot: a semi-analytical calculation of the solution of the Volterra integral equation gives a sharp peak due to the fact that the contribution of each packet of GWs of fixed wavenumberk is strongly singled out when one substitutes the integrals with series and sums.As a consequence, this solution method may have some usefulness when one wants to point out the contributions really dominating in producing a polarization for the CMB.From this analysis one can also infer that the best angular scales to test in order to detect a polarization for the CMB are 2°–3°, smaller than those investigated by COBE.     

On Einstein–Rosen Cosmic Strings in a Scalar Tensor Theory of Gravitation

Explicit field equations of a scalar tensor theory of gravitation proposed by Saez and Ballester are obtained with the aid of Einstein–Rosen cylindrically symmetric metric in the presence of cosmic string source. The field equations being highly non–linear static and non–static cases have been considered separately. It is observed that in the static case the geometric strings do not exist while in the non–static case cosmological model does not exist in this theory.     

Line-of-Sight Anisotropies in the Cosmic Dawn and Epoch of Reionization 21-cm Power Spectrum

The line-of-sight direction in the redshifted 21-cm signal coming from the cosmic dawn and the epoch of reionization is quite unique in many ways compared to any other cosmological signal. Different unique effects, such as the evolution history of the signal, non-linear peculiar velocities of the matter etc. will imprint their signature along the line-of-sight axis of the observed signal. One of the major goals of the future SKA-LOW radio interferometer is to observe the cosmic dawn and the epoch of reionization through this 21-cm signal. It is thus important to understand how these various effects affect the signal for its actual detection and proper interpretation. For more than one and half decades, various groups in India have been actively trying to understand and quantify the different line-of-sight effects that are present in this signal through analytical models and simulations. In many ways the importance of this sub-field under 21-cm cosmology have been identified, highlighted and pushed forward by the Indian community. In this article, we briefly describe their contribution and implication of these effects in the context of the future surveys of the cosmic dawn and the epoch of reionization that will be conducted by the SKA-LOW.     

Relation of Velocity Distribution and Mass for DA White Dwarfstwo

White dwarfs are the evolutionary endpoint of the low-and-medium mass stars. In the studies of white dwarfs, the mass of white dwarf is an important physical parameter. In this paper, we give an analysis about the velocity distribution of DA white dwarfs in the Sloan Digital Sky Survey (SDSS), and hope to find the relation between mass and velocity distribution of white dwarfs. We get the radial velocity and tangential velocity of every DA white dwarf according to their proper motion and spectral shift. Through analyzing the velocity distribution of DA white dwarfs, we find that the small-mass white dwarfs, which are produced from the single-star evolution channel, have a relatively large velocity dispersion.     

Stability of the Triangular Libration Points in the Unrestricted Planar Problem of a Symmetric Rigid Body and a Point Mass

In papers (Godziewski and Maciejewski, 1998a, b, 1999), we investigate unrestricted, planar problem of a dynamically symmetric rigid body and a sphere. Following the original statement of the problem by Kokoriev and Kirpichnikov (1988), we assume that the potential of the rigid body is approximated by the gravitational field of a dumb-bell. The model is described in terms of a 2D Hamiltonian depending on three parameters.In this paper, we investigate the stability of triangular equilibria permissible by the dynamics of the model, under the assumption of low-order resonances. We analyze all resonances of order smaller than four, and we examine the stability with application of theorems by Markeev and Sokolsky. These are the possible following cases: the non-diagonal resonance of the first order with two null characteristic frequencies (unstable); resonances of the first order with one nonzero frequency (diagonal and non-diagonal, stable and unstable); the second-order resonance, which is non-diagonal and stable, and the third-order resonance which is generically unstable, except for three points in the parameters' space, corresponding to stable equilibria.We discuss a perturbed version of Kokoriev and Kirpichnikov model, and we find that if the perturbation is small and depends on the coordinates only, the triangular equilibria persist, except if for the unperturbed equilibria the first-order resonance occurs. We show that the resonances of the order higher than two are also preserved if the perturbation acts.     

On the prospects of Ultra-High Energy Cosmic Rays detection by high altitude antennas

Radio emission from Ultra-High Energy Cosmic Rays (UHECR) showers detected after specular reflection off the Antarctic ice surface has been recently demonstrated by the ANITA balloon-borne experiment. An antenna observing a large area of ice or water from a mountaintop, a balloon or a satellite may be competitive with more conventional techniques. We present an estimate of the exposure of a high altitude antenna, which provides insight on the prospects of this technique for UHECR detection. We find that a satellite antenna may reach a significantly larger exposure than existing UHECR observatories, but an experimental characterization of the radio reflected signal is required to establish the potential of this approach. A balloon-borne or a mountaintop antenna are found not to be competitive under any circumstances.     

Satellite Orbital Precessions Caused by the Octupolar Mass Moment of a Non-Spherical Body Arbitrarily Oriented in Space

I consider a satellite moving around a non-spherical body of mass M and equatorial radius R, and calculate its orbital precessions caused by the body’s octupolar mass moment J ₄. I consider only the effects averaged over one orbital period T of the satellite. I give exact formulas, not restricted to any special values of either the eccentricity e or the inclination i of the satellite’s orbit. I do not assume any preferential orientation for the body’s spin axis ${\boldsymbol{\hat{{\mathbf{k}}}}}$ because in many cases of potential interest (exoplanets, neutron stars, black holes) it is poorly known or unknown at all.     

A Statistical Study of the Mass Distribution of Neutron Stars

By reviewing the methods of mass measurements of neutron stars in four different kinds of systems, i.e., the high-mass X-ray binaries (HMXBs), low-mass X-ray binaries (LMXBs), double neutron star systems (DNSs) and neutron star-white dwarf (NS-WD) binary systems, we have collected the orbital parameters of 40 systems. By using the boot-strap method and the Monte-Carlo method, we have rebuilt the likelihood probability curves of the measured masses of 46 neutron stars. The statistical analysis of the simulation results shows that the masses of neutron stars in the X-ray neutron star systems and those in the radio pulsar systems exhibit different distributions. Besides, the Bayes statistics of these four different kind systems yields the most-probable probability density distributions of these four kind systems to be (1.340 ± 0.230)M8, (1, 505 ± 0.125)M8,(1.335 ± 0.055)M8 and (1.495 ± 0.225)M8, respectively. It is noteworthy that the masses of neutron stars in the HMXB and DNS systems are smaller than those in the other two kind systems by approximately 0.16M8. This result is consistent with the theoretical model of the pulsar to be accelerated to the millisecond order of magnitude via accretion of approximately 0.2M8. If the HMXBs and LMXBs are respectively taken to be the precursors of the BNS and NS-WD systems, then the influence of the accretion effect on the masses of neutron stars in the HMXB systems should be exceedingly small. Their mass distributions should be very close to the initial one during the formation of neutron stars. As for the LMXB and NS-WD systems, they should have already under- gone the process of suffcient accretion, hence there arises rather large deviation from the initial mass distribution.     

Mass Distribution and Kinematics of the Barred Galaxy NGC 2336

For the barred galaxy NGC 2336, stationary models are constructed which reproduce in a consistent manner the observed NIR surface brightness distribution and the observed HII kinematics in those regions affected by the bar. This procedure can answer the question whether the observed kinematics of the galaxy agree with the model predictions derived from the observed distribution of visible matter (assuming that plausible corrections for the presence of dark matter can be applied). It turns out that the parameter values from the morphological decomposition and those needed to fit the HII rotation curves of NGC 2336 best are in excellent agreement. This revised version was published online in July 2006 with corrections to the Cover Date.     

Constraining the Mass Distribution of Cluster Galaxies by Weak Lensing

Analysing the weak lensing distortions of the images of faint background galaxies provides a means to constrain the average mass distribution of cluster galaxies and potentially to test the extent of their dark matter haloes as a function of the density of their environment. The observable image distortions are a consequence of the interplay between the effects of a global cluster mass distribution and the perturbations resulting from individual cluster galaxies. Starting from a reconstruction of the cluster mass distribution with conventional techniques, we apply a maximum likelihood method to infer the average properties of an ensemble of cluster galaxies. From simulations this approach is found to be reliable as long as the galaxies including their dark matter haloes only contribute a small fraction to the total mass of the system. If their haloes are extended, the galaxies contain a substantial mass fraction. In this case our method is still applicable in the outer regions of clusters, where the surface mass density is low, but yields biased estimates of the parameters describing the mass profiles of the cluster galaxies in the central part of the cluster. In that case it will be necessary to resort to more sophisticated strategies by modelling cluster galaxies and an underlying global mass distribution simultaneously. We conclude that galaxy–galaxy lensing in clusters provides a unique means to probe the presence and extent of dark haloes of cluster galaxies.