Relativistic model of radiating massive fluid sphere

In this paper we present a new class of nonsingular solutions representing time dependent balls of perfect fluid with matter-radiation in general relativity. The solution of the class is suitable for interior modeling of a quasar i.e. a massive radiating star. The interior solution is matched with a zero pressure Vaidya metric. From this solution we constructed a quasar model by assuming the life time of the quasar of ≈10⁷ year. We obtained a mass of the quasar of ≈10⁹ M _θ , linear dimension ≈10¹⁷ km and a rate of emission L _∞≈10⁴⁷ erg/s.     

Artificial contradiction between cosmology and particle physics: the Λ problem

It is shown that the usual choice of units obtained by taking G=c=ℏ=1, giving the Planck’s units of mass, length and time, introduces an artificial contradiction between cosmology and particle physics: the lambda problem that we associate with ℏ. We note that the choice of ℏ=1 does not correspond to the scale of quantum physics. For this scale we prove that the correct value is ℏ≈1/10¹²², while the choice of ℏ=1 corresponds to the cosmological scale. This is due to the scale factor of 10⁶¹ that converts the Planck scale to the cosmological scale. By choosing the ratio G/c ³=constant=1, which includes the choice G=c=1, and the momentum conservation mc=constant, we preserve the derivation of the Einstein field equations from the action principle. Then the product Gm/c ²=r _g , the gravitational radius of m, is constant. For a quantum black hole we prove that ℏ≈r _g ²≈(mc)². We also prove that the product Λℏ is a general constant of order one, for any scale. The cosmological scale implies Λ≈ℏ≈1, while the Planck scale gives Λ≈1/ℏ≈10¹²². This explains the Λ problem. We get two scales: the cosmological quantum black hole (QBH), size ∼10²⁸ cm, and the quantum black hole (qbh) that includes the fundamental particles scale, size ∼10⁻¹³ cm, as well as the Planck’ scale, size ∼10⁻³³ cm.      

Magnetoacoustic Wave Trains in the 11 July 2005 Radio Event with Fiber Bursts

A dm-radio emission with fiber bursts observed on 11 July 2005 was analyzed using wavelet filtration and spectral methods. In filtered radio spectra we found structures with different characteristic period P and frequency drift FD: i) fiber substructures (composed of dot emissions) with P ₁≈ 0.5 s, FD₁=− 87 MHz s⁻¹ on average, ii) fiber structures with P ₂≈1.9 s, and iii) drifting structures with P ₃≈81.4 s, FD₂=− 8.7, + 98.5, and − 21.8 MHz s⁻¹. In the wavelet spectra we recognized patterns having the form of tadpoles. They were detected with the same characteristic periods P as found for the filtered structures. The frequency drift of the tadpole heads is found to be equal to the frequency drift of some groups of fibers for the long-period wavelet tadpoles (P ₃) and to the frequency drift of individual fibers for the short-period tadpoles (P ₂). Considering these wavelet tadpoles as signatures of propagating magnetoacoustic wave trains, the results indicate the presence of several wave trains in the fibers’ source. While the long-period wave trains trigger or modulate a whole group of fibers, the short-period ones look like being connected with individual fiber bursts. This result supports the model of fibers based on magnetoacoustic waves. Using a density model of the solar atmosphere we derived the velocities of the magnetoacoustic waves, 107 and 562 km s⁻¹, and setting them equal to the Alfvén ones we estimated the magnetic field in the source of fiber bursts as 10.7 and 47.8 G.     

High Temporal and Spectral Resolution Interferometric Observations of Unusual Solar Radio Bursts

We report very high temporal and spectral resolution interferometric observations of some unusual solar radio bursts near 1420 MHz. These bursts were observed on 13 September 2005, 22 minutes after the peak of a GOES class X flare from the NOAA region 10808. Our observations show 11 episodes of narrow-band intermittent emission within a span of ≈ 8 s. Each episode shows a heavily frequency-modulated band of emission with a spectral slope of about −245.5 MHz s⁻¹, comprising up to 8 individual blobs of emission and lasts for 10 – 15 ms. The blobs themselves have a spectral slope of ≈ 0 MHz s⁻¹, are ≈ 200 – 250 kHz wide, appear every ≈ 400 kHz and last for ≈ 4 – 5 ms. These bursts show brightness temperatures in the range 10¹² K, which suggests a coherent emission mechanism. We believe these are the first high temporal and spectral resolution interferometric observations of such rapid and narrow-bandwidth solar bursts close to 1420 MHz and present an analysis of their temporal and spectral characteristics.     

Horizon-free gravitational collapse of radiating fluid sphere

In this paper we present a detailed study of BCT Ist solution Tewari (Astrophys. Space Sci. 149:233, 1988) representing time dependent balls of perfect fluid with matter-radiation in general relativity. Assuming the life time of quasar 10⁷ years our model has initial mass≈10⁸ M _Θ with an initial linear dimension≈10¹⁵ cm. Our model is radiating the energy at a constant rate i.e. L _∞=10⁴⁷ ergs/sec with the gravitational red shift, z=0.44637. In this model we have 2GM(u)/c ² R _S (u))=0.3191 i.e. the model is horizon free.     

New class of Well behaved exact solutions of relativistic charged <Emphasis Type="Italic">white-dwarf</Emphasis> star with perfect fluid

The paper presents a class of interior solutions of Einstein-Maxwell field equations of general relativity for a static, spherically symmetric distribution of the charged fluid. This class of solutions describes well behaved charged fluid balls. The class of solutions gives us wide range of parameter K (0.3277≤K≤0.49), for which the solution is well behaved hence, suitable for modeling of super dense star. For this solution the mass of a star is maximized with all degree of suitability and by assuming the surface density ρ _b =2×10¹⁴ g/cm³. Corresponding to K=0.3277 with X=−0.15, the maximum mass of the star comes out to be M=0.92M _Θ with radius r _b ≈17.15 km and the surface red shift Z _b ≈0.087187. It has been observed that under well behaved conditions this class of solutions gives us the mass of super dense object within the range of white-dwarf.     

Variety of well behaved exact solutions of Einstein–Maxwell field equations: an application to Strange Quark stars, Neutron stars and Pulsars

We present a variety of well behaved classes of Charge Analogues of Tolman’s iv (1939). These solutions describe charged fluid balls with positively finite central pressure, positively finite central density; their ratio is less than one and causality condition is obeyed at the centre. The outmarch of pressure, density, pressure-density ratio and the adiabatic speed of sound is monotonically decreasing, however, the electric intensity is monotonically increasing in nature. These solutions give us wide range of parameter for every positive value of n for which the solution is well behaved hence, suitable for modeling of super dense stars. keeping in view of well behaved nature of these solutions, one new class of solutions is being studied extensively. Moreover, this class of solutions gives us wide range of constant K (0.3≤K≤0.91) for which the solution is well behaved hence, suitable for modeling of super dense stars like Strange Quark stars, Neutron stars and Pulsars. For this class of solutions the mass of a star is maximized with all degree of suitability, compatible with Quark stars, Neutron stars and Pulsars. By assuming the surface density ρ _b =2×10¹⁴ g/cm³ (like, Brecher and Caporaso in Nature 259:377, 1976), corresponding to K=0.30 with X=0.39, the resulting well behaved model has the mass M=2.12M _Θ, radius r _b ≈15.27 km and moment of inertia I=4.482×10⁴⁵ g cm²; for K=0.4 with X=0.31, the resulting well behaved model has the mass M=1.80M _Θ, radius r _b ≈14.65 km and moment of inertia I=3.454×10⁴⁵ g cm²; and corresponding to K=0.91 with X=0.135, the resulting well behaved model has the mass M=0.83M _Θ, radius r _b ≈11.84 km and moment of inertia I=0.991×10⁴⁵ g cm². For n=0 we rediscovered Pant et al. (in Astrophys. Space Sci. 333:161, 2011b) well behaved solution. These values of masses and moment of inertia are found to be consistent with other models of Neutron stars and Pulsars available in the literature and are applicable for the Crab and the Vela Pulsars.     

On the origin of the high-Q high-frequency oscillations of magnetars

A model for the high-frequency (20–2400 Hz) quasi-periodic oscillations (QPOs) of magnetars based on the representation of coronal magnetic loops as equivalent electric RLC circuits is proposed. The observed periods of the QPOs and their high Q-factor (Q ≈ 10⁴–10⁵) are explained. It follows from the model that the QPOs can be excited not only in the tail of a flare but also before the main pulse. The parameters of the QPO source at the “ringing tail” stage of the flare from SGR 1806–20 on December 27, 2004, have been estimated: electric current I ≈ 3 × 10¹⁹ A, minimum magnetic field strength B _min ≈ 10¹³ G, and electron density n ≈ 2 × 10¹⁶ cm⁻³.     

Well-behaved relativistic charged super-dense star models

A new class of charged super-dense star models is obtained by using an electric intensity, which involves a parameter, K. The metric describing the model shares its metric potential g ₄₄ with that of Durgapal’s fourth solution (J. Phys. A, Math. Gen. 15:2637, 1982). The pressure-free surface is kept at the density ρ _b =2×10¹⁴ g/cm³ and joins smoothly with the Reissner-Nordstrom solution. The charge analogues are well-behaved for a wide range, 0≤K≤59, with the optimum value of X=0.264 i.e. the pressure, density, pressure–density ratio and velocity of sound are monotonically decreasing and the electric intensity is monotonically increasing in nature for the given range of the parameter K. The maximum mass and the corresponding radius occupied by the neutral solution are 4.22M _Θ and 20 km, respectively for X=0.264. For the charged solution, the maximum mass and radius are defined by the expressions M≈(0.0059K+4.22)M _Θ and r _b ≈−0.021464K+20 km respectively.     

The Atmosphere of Io: Abundances and Sources of Sulfur Dioxide and Atomic Hydrogen

An analysis and interpretation of reflected solar Lyman α intensity data acquired with the Hubble Space Telescope (HST) implies an equatorially confined atmosphere with SO₂ column densities ∼ 1–2 × 10¹⁶ cm^-2. Poleward of 30° the SO₂ density must decrease sharply reaching an asymptotic polar value of < 10¹⁵ cm^-2 at 45° to achieve the observed 2 kR intensity peaks. The corresponding surface reflectivities must be either a constant 0.047 for higher equatorial SO₂ or a variable reflectivity of 0.027 with lower SO₂ densities at the equator increasing to a polar value of ∼ 0.05. The average residence time for an atmospheric SO₂ molecule is ∼ 2–3 days for the canonical mass loading rate of the Io plasma torus = 10³⁰ amu s^-1. With atomic hydrogen in the atmosphere and corona constrained by the HST observations, it is estimated that a pickup proton density ratio of 0.25–0.4% can be sustained by a supply of Io plasma torus protons neutralized in Io's atmosphere/exosphere, if protons constitute 7% of the total torus ion density, which is close to the Chust et al. (1999) pickup proton density ratio and under the widely quoted 10% proton content of the torus. This revised version was published online in July 2006 with corrections to the Cover Date.     

WR 140 (=V1687 Cyg): Infrared photometry, 2001–2010

We present the results of our infrared observations of WR 140 (=V1687 Cyg) in 2001–2010. Analysis of the observations has shown that the J brightness at maximum increased near the periastron by about 0 ^m .3; the M brightness increased by ∼2 ^m in less than 50 days. The minimum J brightness and the minimum L and M brightnesses were observed 550–600 and 1300–1400 days after the maximum, respectively. The JHKLM brightness minimum was observed in the range of orbital phases 0.7–0.9. The parameters of the primary O5 component of the binary have been estimated to be the following: R(O5) ≈ 24.7R _⊙, L(O5) ≈ 8 × 10⁵ L _⊙, and M _bol(O5) ≈ −10 ^m . At the infrared brightness minimum, T _g ∼ 820–880 K, R _g ≈ 2.6 × 10⁵ R _⊙, the optical depth of the shell at 3.5 μm is ∼5.3 × 10⁻⁶, and its mass is ≈1.4 × 10⁻⁸ M _⊙. At the maximum, the corresponding parameters are ∼1300 K, 8.6 × 10⁴ R _⊙, ∼2 × 10⁻⁴, and ∼6 × 10⁻⁸ M _⊙; the mean rate of dust inflow (condensation) into the dust structure is ∼3.3 × 10⁻⁸ M _⊙ yr⁻¹. The mean escape velocity of the shell from the heating source is ∼10³ km s⁻¹ and the mean dispersal rate of the shell is ∼1.1 × 10⁻⁸ M _⊙ yr⁻¹.     

On origin of ultra high energy cosmic rays

Propagation of UHE protons through CMB radiation leaves the imprint on energy spectrum in the form of Greisen–Zatsepin–Kuzmin (GZK) cutoff, bump (pile-up protons) and dip. The dip is a feature in energy range 1×10¹⁸–4×10¹⁹ eV, caused by electron-positron pair production on CMB photons. Calculated for power-law generation spectrum with index γ _g =2.7, the shape of the dip is confirmed with high accuracy by data of Akeno—AGASA, HiRes, Yakutsk and Fly’s Eye detectors. The predicted shape of the dip is robust: it is valid for the rectilinear and diffusive propagation, for different discretenesses in the source distribution, for local source overdensity and deficit etc. This property of the dip allows us to use it for energy calibration of the detectors. The energy shift λ for each detector is determined by minimum χ ² in comparison of observed and calculated dip. After this energy calibration the absolute fluxes, measured by AGASA, HiRes and Yakutsk detectors remarkably coincide in energy region 1×10¹⁸–1×10²⁰ eV. Below the characteristic energy E _c ≈1×10¹⁸ eV the spectrum of the dip flattens for both diffusive and rectilinear propagation, and more steep galactic spectrum becomes dominant at E<E _c . The energy of transition E _tr<E _c approximately coincides with the position of the second knee E _2kn , observed in the cosmic ray spectrum. The dip-induced transition from galactic to extragalactic cosmic rays at the second knee is compared with traditional model of transition at ankle, the feature observed at energy ∼1×10¹⁹ eV.      

A diffraction limit on the gravitational lens effect

The focussing of gravitational radiation by the interior and exterior gravitational field of a Newtonian gravitational lens is considered. A graphical method for determining the caustic structure of a Newtonian gravitational lens is presented and the caustic structure of a solar type gravitational lens is discussed. Estimates of the amplitude magnification in the caustic region indicate that waves with frequencies less than a critical cutoff frequency ω _c are not amplified significantly. For a lens of massM this cutoff frequency is ω _c ≈(10^-1πM)^-1; for the Sun ω _c ≈10⁴s^-1. Work supported in part by National Science Foundation Grant PHY78-05368.     

A new well behaved exact solution in general relativity for perfect fluid

We present a new spherically symmetric solution of the general relativistic field equations in isotropic coordinates. The solution is having positive finite central pressure and positive finite central density. The ratio of pressure and density is less than one and casualty condition is obeyed at the centre. Further, the outmarch of pressure, density and pressure-density ratio, and the ratio of sound speed to light is monotonically decreasing. The solution is well behaved for all the values of u lying in the range 0<u≤.186. The central red shift and surface red shift are positive and monotonically decreasing. Further, we have constructed a neutron star model with all degree of suitability and by assuming the surface density ρ _b =2×10¹⁴ g/cm³. The maximum mass of the Neutron star comes out to be M=1.591 M _Θ with radius R _b ≈12.685 km. The most striking feature of the solution is that the solution not only well behaved but also having one of the simplest expressions so far known well behaved solutions. Moreover, the good matching of our results for Vela pulsars show the robustness of our model.     

Kinematics of Gould's Belt: Model and Observations

Using the available data for nearby stars we derive the velocity ellipsoid of dwarf O-B5.5 stars belonging to the Gould Belt (GB). The resulting vertex deviation for the whole sample is negative (l _v ≈ −70^°) and this value is modified to l _v≈ 20^° when the members of the Pleiades moving group are removed from the sample. This implies the existence of, at least, two different kinematic groups defining the GB system. We also model the evolution of a supershell in the solar neighborhood, and obtain a fit to the shape and kinematics of the gas in GB. Assuming that the expanding shell is also forming stars, we obtain the corresponding velocity fields for the shell and its newly formed stars. The average vertex deviation value resulting from these models for the new stars is l _v≈ 20^°, and is consistent with the observed value when the Pleiades moving group members are excluded from the GB. This revised version was published online in July 2006 with corrections to the Cover Date.     

Expansion Speed of Coronal Mass Ejections

A large set of limb coronal mass ejections (CMEs) are used to determine the accurate relationship between radial (V _rad) and expansion (V _exp) speeds of CMEs. It is demonstrated that this relation is exceptionally well described by the function f(w)=1/2(1+cot w), representing a full cone model for the CME with a half-width, w. We also demonstrate that for extremely fast CMEs (V _exp>3000 km s⁻¹), it is better to use the approximation V _rad≈V _LE. This implies that such CMEs expand spherically above the solar surface.     

Acceleration of Relativistic Protons During the 20 January 2005 Flare and CME

The origin of relativistic solar protons during large flare/CME events has not been uniquely identified so far. We perform a detailed comparative analysis of the time profiles of relativistic protons detected by the worldwide network of neutron monitors at Earth with electromagnetic signatures of particle acceleration in the solar corona during the large particle event of 20 January 2005. The intensity – time profile of the relativistic protons derived from the neutron monitor data indicates two successive peaks. We show that microwave, hard X-ray, and γ-ray emissions display several episodes of particle acceleration within the impulsive flare phase. The first relativistic protons detected at Earth are accelerated together with relativistic electrons and with protons that produce pion-decay γ rays during the second episode. The second peak in the relativistic proton profile at Earth is accompanied by new signatures of particle acceleration in the corona within ≈1R _⊙ above the photosphere, revealed by hard X-ray and microwave emissions of low intensity and by the renewed radio emission of electron beams and of a coronal shock wave. We discuss the observations in terms of different scenarios of particle acceleration in the corona.     

Electron Temperatures and Flow Speeds of the Low Solar Corona: MACS Results from the Total Solar Eclipse of 29 March 2006 in Libya

An experiment was conducted in conjunction with the total solar eclipse on 29 March 2006 in Libya to measure both the electron temperature and its flow speed simultaneously at multiple locations in the low solar corona by measuring the visible K-coronal spectrum. Coronal model spectra incorporating the effects of electron temperature and its flow speed were matched with the measured K-coronal spectra to interpret the observations. Results show electron temperatures of (1.10±0.05) MK, (0.70±0.08) MK, and (0.98±0.12) MK, at 1.1 R _⊙ from Sun center in the solar north, east and west, respectively, and (0.93±0.12) MK, at 1.2 R _⊙ from Sun center in the solar west. The corresponding outflow speeds obtained from the spectral fit are (103±92) km s⁻¹, (0+10) km s⁻¹, (0+10) km s⁻¹, and (0+10) km s⁻¹. Since the observations were taken only at 1.1 R _⊙ and 1.2 R _⊙ from Sun center, these speeds, consistent with zero outflow, are in agreement with expectations and provide additional confirmation that the spectral fitting method is working. The electron temperature at 1.1 R _⊙ from Sun center is larger at the north (polar region) than the east and west (equatorial region).     

An Extreme Solar Event of 20 January 2005: Properties of the Flare and the Origin of Energetic Particles

The famous extreme solar and particle event of 20 January 2005 is analyzed from two perspectives. Firstly, using multi-spectral data, we study temporal, spectral, and spatial features of the main phase of the flare, when the strongest emissions from microwaves up to 200 MeV gamma-rays were observed. Secondly, we relate our results to a long-standing controversy on the origin of solar energetic particles (SEP) arriving at Earth, i.e., acceleration in flares, or shocks ahead of coronal mass ejections (CMEs). Our analysis shows that all electromagnetic emissions from microwaves up to 2.22 MeV line gamma-rays during the main flare phase originated within a compact structure located just above sunspot umbrae. In particular, a huge (≈ 10⁵ sfu) radio burst with a high frequency maximum at 30 GHz was observed, indicating the presence of a large number of energetic electrons in very strong magnetic fields. Thus, protons and electrons responsible for various flare emissions during its main phase were accelerated within the magnetic field of the active region. The leading, impulsive parts of the ground-level enhancement (GLE), and highest-energy gamma-rays identified with π ⁰-decay emission, are similar and closely correspond in time. The origin of the π ⁰-decay gamma-rays is argued to be the same as that of lower-energy emissions, although this is not proven. On the other hand, we estimate the sky-plane speed of the CME to be 2 000 – 2 600 km s⁻¹, i.e., high, but of the same order as preceding non-GLE-related CMEs from the same active region. Hence, the flare itself rather than the CME appears to determine the extreme nature of this event. We therefore conclude that the acceleration, at least, to sub-relativistic energies, of electrons and protons, responsible for both the major flare emissions and the leading spike of SEP/GLE by 07 UT, are likely to have occurred nearly simultaneously within the flare region. However, our analysis does not rule out a probable contribution from particles accelerated in the CME-driven shock for the leading GLE spike, which seemed to dominate at later stages of the SEP event. S.N. Kuznetsov deceased 17 May 2007.     

Cosmic behavior, statefinder diagnostic and w?w′ analysis for?interacting new agegraphic dark energy model in non-flat universe

We investigate the interacting NADE model in non-flat universe. The effects of spatial curvature Ω _k , interaction coefficient α and the main parameter of NADE, n, on EoS parameter w _d and deceleration parameter q are studied. We obtain a minimum value for n in both early and present time, in order to that our DE model crosses the phantom divide. Also in a closed universe, changing the sign of q is strongly dependent on α. It has been shown that the quantities w _d and q have a different treatment for various spatial curvature. At last, we calculate the statefinder diagnostic and w−w ^′ analysis in non flat universe. In non flat universe, the statefinder trajectories are discriminated by both n and α.