ALBERT

Description: Two classes of GRBs have been identified thus far without doubt and are prescribed to different physical scenarios—NS-NS or NS-BH mergers, and collapse of massive stars, for short and long GRBs, respectively. The existence of two distinct populations was inferred through a bimodal distribution of the observed durations \(T_{90}\) , and the commonly applied \(2~\mbox{s}\) limit between short and long GRBs was obtained by fitting a parabola between the two peaks in binned data from BATSE 1B. Herein, by means of a maximum likelihood (ML) method a mixture of two Gaussians is fitted to the datasets from BATSE, Swift , BeppoSAX , and Fermi in search for a local minimum that might serve as a new, more proper, limit for the two GRB classes. It is found that Swift and BeppoSAX distributions are unimodal, hence no local minimum is present, Fermi is consistent with the conventional limit, whereas BATSE gives the limit significantly longer (equal to \(3.38\pm 0.27~\mbox{s}\) ) than \(2~\mbox{s}\) . These new values change the fractions of short and long GRBs in the samples examined, and imply that the observed \(T_{90}\) durations are detector dependent, hence no universal limiting value may be applied to all satellites due to their different instrument specifications. Because of this, and due to the strong overlap of the two-Gaussian components, the straightforward association of short GRBs to mergers and long ones to collapsars is ambiguous.

Description: When luminosity of black hole accretion disks is greater than 0.06 Eddington luminosity ( \(L \geq0.06 L_{E} \) ), according to standard disk model, the inner region of these disks is radiation-pressure dominated (RPD) and unstable in thermal and viscous modes. Whereas this object conflicts with the observations, if \(0.01 L_{E}\leq L \leq0.5 L_{E}\) . Thus, the change of viscosity or considering relativistic corrections that are essential in realistic black hole accretion disks may solve this problem between theory and observation. An explanation by taking into account the effect of black hole spin with the presence of different viscosities on the secular and thermal instabilities in geometrically thin optically thick accretion disks is presented. In order to consider the effects of spin and general relativity, kerr space-time is used. A diffusive form of viscous stress tensor, a new form of fully relativistic shear stress tensor that is not used so far, power law, and parametric viscosity are considered. Investigations have been done in some parameters of viscosity and some values of spin. We conclude that the type of viscosity is effective in stabilization of the disk, whereas spin has no effect. Increasing stability or instability in the disk can be caused by spin, which this behavior is related to the type of viscous parameter. Thereby, spin can be effective on the temperature, accretion rate, and in the luminosity of the system.

Description: We consider the effect of a partial coverage of quasar broad-line regions (QSO BLRs) by intervening \(\mbox{H}_{2}\) -bearing clouds when a part of quasar (QSO) radiation passes by a cloud not taking part in absorption-line system formation of the QSO spectrum. That leads to modification of observable absorption line profiles and consequently to a bias in physical parameters derived from standard absorption line analysis. In application to the \(\mbox{H}_{2}\) absorption systems the effect has been revealed in the analysis of \(\mbox{H}_{2}\) absorption system in the spectrum of Q 1232+082 (see Ivanchik et al. in Mon. Not. R. Astron. Soc. 404:1583, 2010 , Balashev et al. in Mon. Not. R. Astron. Soc. 418:357, 2011 ). We estimate a probability of the effect to be detected in QSO spectra. To do this we derive distribution of BLR sizes of high-z QSOs from Sloan Digital Sky Survey (SDSS) Data Release 9 (DR9) catalogue and assume different distributions of cloud sizes. We conclude that the low limit of the probability is about 11 %. The latest researches shows that about a fifth of observed \(\mbox{H}_{2}\) absorption systems can be partially covered. Accounting of the effect may allow to revise significantly physical parameters of interstellar clouds obtained by the spectral analysis.

Description: The spatially homogeneous and anisotropic Bianchi type-V universe filled with interacting Dark matter and Holographic dark energy has been studied. The exact solutions of Einstein’s field equations are obtained by (i) applying the special law of variation of Hubble parameter that yields constant values of the deceleration parameter and (ii) using a special form of deceleration parameter. It has been observed that for suitable choice of interaction between dark matter and holographic dark energy there is no coincidence problem (unlike \(\varLambda\) CDM). Also, in all the resulting models the anisotropy of expansion dies out very quickly and attains isotropy after some finite time. The physical and geometrical aspects of the models are also discussed.

Description: The properties of nonlinear dust-acoustic rogue waves in an unmagnetized, collisionless, four-component dusty plasma system consisting of electrons, nonthermal ions, hot and cold dust species have been investigated. The basic set of fluid equations is reduced to a nonlinear Schrodinger equation. The dependence of the rogue wave properties on the ion energetic population parameter is discussed. The results of the present investigation could be applicable in Saturn F-ring.

Description: In this paper, we study the reconstruction scenario of a dark energy model in the framework of modified Horava-Lifshitz \(F(R)\) gravity or \(F(\tilde{R})\) gravity. We assume generalized ghost pilgrim dark energy model in flat universe. We consider three well-known scale factors to analyze the behavior of reconstructed \(F(\tilde{R})\) model. These scale factors include bouncing and intermediate scale factors as well as scale factor representing the unification of matter and accelerated phases. The graphical representation is adopted to analyze the behavior of reconstructed model and equation of state parameter for different values of model parameter. The reconstructed model represents increasing and decreasing behavior with respect to time in all cases. The equation of state parameter represents phantom-like universe after transition for intermediate scale factor while quintessence behavior for bouncing and unified scale factors. We also found that the squared speed of sound exhibits the stability of all reconstructed models.

Description: In this paper, we investigate the role of electromagnetic field on the stability regions of charged self-gravitating compact objects by using the concept of cracking. For this purpose, we have applied local density perturbation scheme to the hydrostatic equilibrium equation as well as on physical parameters involved in the model. In particular, we have examined the cracking of charged compact objects like PSR J1614-2230, PSR J1903+327, Vela X-1, SMC X-1 and Cen X-3 with different values of charge. We conclude that these objects exhibit cracking and stability regions decreases with the increase of charge.

Description: In this paper we have studied the behavior of static spherically symmetric relativistic objects with locally anisotropic matter distribution considering the Tolman VII form for the gravitational potential \(g_{rr}\) in curvature coordinates together with the linear relation between the energy density and the radial pressure. The interior spacetime has been matched continuously to the exterior Schwarzschild geometry. We have investigated and analyzed different physical properties of the stellar model and presented graphically.

Description: This paper explores structure scalars of cylindrically symmetric spacetime in Brans-Dicke gravity. We construct twelve scalar factors using orthogonal splitting of the Reimann tensor and study their distinct dynamical interpretations. These structure scalars are used to derive a set of governing equations of the evolving system. It is concluded that cylindrical systems are necessarily inhomogeneous. Finally, we show that all possible static inhomogeneous cylindrical solutions can be obtained through structure scalars.

Description: In this Letter, based on Bianchi-I type cosmological model, we have studied the evolution of universe in terms of a vector field coupled to the scalar field. The symmetries of the system are calculated in the Noether approach, the scalar potential and the gauge kinetic function are also obtained following these symmetries. The dynamical equations are integrated numerically and the behaviors of cosmological evolution are presented certainly. Furthermore, the early-time and late-time scenarios are also reached asymptotically, that is, the universe is during the period of decelerating expansion in the early time while during the period of accelerating expansion in the late time. Moreover, we have also studied the expansion isotropization of the universe during evolution. There is no Kasner solution in the present case, while the universe would approach an isotropic Robertson-Walker one, concretely, a de Sitter type one in the late time.

Description: In this paper, based on the BSBM theory, we investigate the dynamics of a homogeneous and anisotropic Bianchi type-V (BV) cosmological model subject to variation of the fine structure constant. By performing stability analysis, the anisotropic cosmic attractors are obtained and the anisotropic parameters are studied. The outcome confirms that universe underwent both anisotropy and variation of fine structure constant in the past for an accelerating expansion. However, the result also shows that both anisotropy and fundamental constant variation exist at the present epoch and even become greater in the future. This is in contradiction with the current observational data and therefore the model is not satisfactory.

Description: Our aim is to prove that long time series of solar observations measured with Metsähovi Radio Observatory’s 1.8-meter solar radio telescope, RT-1.8, at 11.2 GHz are reliable, and that the data can be used for solar cyclicity studies. We give a detailed description of RT-1.8 and its calibration. We compare 14 years of Metsähovi Radio Observatory’s solar data from solar cycles 23 and 24 to both Dominion Radio Astrophysical Observatory (DRAO 2015 ), Penticton, Canada 2.8 GHz and Nobeyama Solar Radio Observatory (NSRO 2015 ), Nobeyama, Japan 9.4 and 17.0 GHz data. Our results show high correlation between all data sets.

Description: This work investigates the theoretical and numerical studies on nonlinear propagation of ion acoustic solitary waves (IASWs) in an unmagnetized plasma consisting of nonextensive electrons, Boltzmann positrons and relativistic thermal ions. The Korteweg-de Vries (KdV) equation is derived by using the well known reductive perturbation method. This equation admits the soliton like solitary wave solution. The effects of phase velocity, amplitude of soliton, width of soliton and electrostatic nonlinear propagation of weakly relativistic ion-acoustic solitary waves have been discussed with graphical representation found in the variation of the plasma parameters. The obtained results can be helpful in understanding the features of small but finite amplitude localized relativistic ion-acoustic waves for an unmagnetized three component plasma system in astrophysical compact objects.

Description: Systematic relationships of the subclass-averaged rise, decay times and durations of flare events as a function of the logarithmic peak flux ( \(\operatorname{ln}f\) ) are investigated, employing the soft X-ray flares observed by GOES during the period from September 1975 to October 2014. Different behaviors are found before and after 1997. Since 1997 they all vary linearly with \(\operatorname{ln}f\) , obeying the RV model. However, prior to 1997 they vary quadratically with \(\operatorname{ln}f\) , implying a different energy storage/release process of flaring. The discrepancy may be related to the variation in the turbulence in the corona caused by the weakening magnetic field strength in the recent two decades. This motivates us to propose a Stochastic-Diffusive model for explaining the above result, by assuming that the temporal rate of flare energy resulted by external forces is proportional to the total energy already stored in the flare system and inversely proportional to the size scale of diffusion.

Description: Intermediate inflation is considered in a non-canonical scalar field model, in which the kinetic term of scalar field is taken as a power-law function. The free parameters of the model are constrained by using the most recent observational data related to scalar spectra index, tensor-to-scalar ratio, and scalar perturbation amplitude. The results are used to depict the potential behavior of the model and estimate the initial and final time of inflation.

Description: In light of the recent interest in dynamical dark energy models based on a cosmology with varying gravitational and cosmological parameters \(G\) and \(\varLambda\) , we present here a model of inertia in a type of Friedmann universe with \(G = G_{0}(A/A_{0})^{\sigma}\) ; \(A\) being the dimensionless scale factor, that was recently studied by Singh et al. (Astrophys. Space Sci. 345:213, 2013 ). The proposed Machian model of inertia utilizes the curved space generalization of Sciama’s law of inertial induction, which is based on the analogy between the retarded far fields of electrodynamics and those of gravitation, and expresses the total inertial force \(F= -ma\) on an accelerating mass \(m\) in terms of contributions from all matter in the observable Universe. We show that for a varying Friedmann model with \(\sigma=-3/2\) , inertial induction alone can account for the total inertial force on the accelerating mass. We then compare this cosmological model with current observational constraints for the variation of \(G\) .

Description: Elemental abundance provides an effective vehicle to understand lunar petrologic characteristics and evolutional history. The APXS mounted on the Yutu rover provides a valuable opportunity to determine the major elemental abundances in lunar soil within a short distance. In this study, we processed the APXS spectra including energy calibration, dead time correction and nonlinear least-squares fitting, and determined the abundances of the lunar major elements using the fundamental parameter method. In the calculation of X-ray fluorescence yield, a finite element method (FEM) was employed to improve the accuracy. The major elemental abundances derived from Chang’E-3 (CE-3) APXS possess a good consistency with the result of LP-GRS (Lunar Prospector gamma-ray spectrometer) data in the landing region. Compared with the chemical composition of the returned lunar rock samples, we draw the conclusion that the lunar soils in CE-3 landing site are fragments of mare basalts. Our conclusion is supported by the geological map of Mare Imbrium.

Description: Mathematica program for various general observer quantities in the general theory of relativity has been developed which uses coordinate system, metric tensor and unit timelike velocity vector as input.

Description: We consider the cosmological system with two interacting fluids: dark energy and dark matter, in a homogeneous and isotropic universe with dissipation. The modified gravitational equation for dark matter is solved. The analytic representations for the Little Rip, the Pseudo Rip, and the bounce cosmology models with dissipation are obtained in terms of the thermodynamic parameters in the equation of state. We analyze the corrections in the energy density for dark matter, in view of the dissipative processes and the coupling with dark energy.

Description: In this paper, we have investigated Kantowski-Sachs space-time in the presence of anisotropic fluid with variable equation of state (EoS) parameter and constant deceleration parameter in the scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977 ). We have found a determinate solution of the field equations of the theory using variation law for Hubble’s parameter given by Bermann (Nuvo Cimento 74:182, 1983 ). Our solution represents Kantowski-Sachs dark energy model in this theory. The physical and kinematical properties of the model are also discussed.

Description: Spatially homogeneous and anisotropic Kantowski-Sachs space-time is considered in the scale covariant theory of gravitation proposed by Canuto et al. (Phys. Rev. Lett. 39:429, 1977 ) in the presence of bulk viscous fluid containing one dimensional cosmic strings. A determinate solution of the field equations of this theory is presented using the special law of variation proposed by Bermann (Nuovo Cimento B74:183, 1983 ). We have also used the proportionality of shear scalar to the scalar expansion of the space time. The solution obtained represents a bulk viscous string cosmological model in this theory. Some physical and kinematical properties of the model are also discussed.

Description: We follow the development of nonaxisymmetric instabilities of self-gravitating disks from the linear regime to the nonlinear regime. Particular attention is paid to comparison of nonlinear simulation results with previous linear and quasi-linear modeling results to study the mass and angular momentum transport driven by nonaxisymmetric disk instabilities. Systems with star-to-disk mass ratios of \(M_{*}/M_{d} = 0.1\) and 5 and inner-to-outer disk radius ratios of \(r_{-}/r_{+} = 0.47\) to 0.66 are investigated. In disks where self-gravity is important, systems with small \(M_{*}/M_{d}\) and large \(r_{-}/r_{+}\) , Jeans-like J modes are dominant and the gravitational stress drives angular momentum transport. In disks where self-gravity is weak, systems with large \(M_{*}/M_{d}\) and large \(r_{-}/r_{+}\) , shear-driven P modes dominate and the Reynolds stress drives angular momentum transport. In disks where self-gravity is intermediate in strength between disks where P modes dominate and disks where J modes dominate, I modes control the evolution of the system and the Reynolds and gravitational stresses both play important roles in the angular momentum transport. In all cases, redistribution of angular momentum takes place on the characteristic disk timescale defined as the orbital period at the location of maximum density in the disk midplane. The disk susceptible to one-armed modes behaves differently than disks dominated by multi-armed spirals. Coupling between the star and the disk driven by one-armed modes leads to angular momentum transfer between the star and disk even when instability is in the linear regime. All modes drive spreading of the disk material and eventually accretion onto the star. The disks dominated by an I mode and one-armed mode do not lead to prompt fission or fragmentation. The J mode dominated disk fragments after instability develops.

Description: Amplitude modulation of a positron acoustic wave is considered in a four-component electron–positron plasma in the quantum magnetohydrodynamic regime. The important ingredients of this study are the inclusion of the particle exchange-correlation potential, quantum diffraction effects via the Bohm potential, and dissipative effect due to viscosity in the momentum balance equation of the charged carriers. A modified nonlinear Schrödinger equation is derived for the evolution of the slowly varying amplitude of the quantum positron acoustic wave by employing the standard reductive perturbation technique. Detailed analysis of the linear and nonlinear dispersions of the quantum positron acoustic wave is presented. For a typical parameter range, relevant to some dense astrophysical objects, it is found that the quantum positron acoustic wave is modulationally unstable above a certain critical wavenumber. Effects of the exchange-correlation potential and the Bohm potential in the wave dynamics are also studied. It is found that the quantum effect due to the particle exchange-correlation potential is significant in comparison to the effect due to the Bohm potential for smaller values of the carrier wavenumber. However, for comparatively larger values of the carrier wavenumber, the Bohm potential effect overtakes the effect of the exchange-correlation potential. It is found that the critical wavenumber for the modulation instability depends on the ratio of the equilibrium hot electron number density and the cold positron number density and on the ratio of the equilibrium hot positron number density and the cold positron number density. A numerical result on the growth rate of the modulation instability is also presented.

Description: We study a more complex case of Hohmann orbital transfer of a satellite by considering non-coplanar and elliptical orbits, instead of planar and circular orbits. We use as parameter the angle between the initial and transference planes that minimizes the energy, and therefore the fuel of a satellite, through the application of two non-tangential impulses for all possible cases. We found an analytical expression that minimizes the energy for each configuration. Some reasonable physical constraints are used: we apply impulses at perigee or apogee of the orbit, we consider the duration of the impulse to be short compared to the duration of the trip, we take the nodal line of three orbits to be coincident and the three semimajor axes to lie in the same plane. We study the only four possible cases but assuming non-coplanar elliptic orbits. In addition, we validate our method through a numerical solution obtained by using some of the actual orbital elements of Sputnik I and Vanguard I satellites. For these orbits, we found that the most fuel-efficient transfer is obtained by applying the initial impulse at apocenter and keeping the transfer orbit aligned with the initial orbit.

Description: In this paper, we have studied the Einstein-Rosen space time in \(f(R,T)\) gravity by considering the second model of Harko et al. (Phys. Rev. D 84:024020, 2011 ), \(f(R,T) = f_{1}(R)+f_{2}(T)\) , where \(f_{1}(R)=\lambda R\) ; \(f_{2}(T)=\lambda T\) and \(f_{1}(R)=\lambda R\) ; \(f_{2}(T)=\lambda T^{2}\) . The matter field is considered in the form of perfect fluid. It is observed that, the perfect fluid represent the Zel’dovich universe in both the forms.

Description: Ionospheric scintillation is a significant component of space-weather studies and serves as an estimate for the level of perturbation in the satellite radio wave signal caused due to small-scale ionospheric irregularities. B-spline functions are used on the GPS ground based data collected during the year 2007–2012 for modeling high- and mid-latitude ionospheric scintillation. Proposed model is for Hornsund, Svalbard and Warsaw, Poland. The input data used in this model were recorded by GSV 4004b receivers. For validation, results of this model are compared with the observation and other existing models. Physical behavior of the ionospheric scintillation during different seasons and geomagnetic conditions are discussed well. Model is found in good coherence with the ionospheric scintillation theory as well as to the accepted scintillation mechanism for high- and mid-latitude.

Description: In the Earth-Moon-spacecraft circular restricted three-body problem (CRTBP), the evaluation of the orbits near the Moon can distinctly reflect the complexity of the dynamical system. In this paper, the long-term behavior of the spatial orbit near the Moon is investigated in the CRTBP. The Poincare section, where the section points are defined as the lunar apsides, is an effective tool. The distribution of the long-term capture solutions and the orbital elements of the section points display the long-term behavior of the spatial lunar orbits from the qualitative and quantitative angles, respectively. As two kinds of important long-term lunar orbits, the quasi-periodic and periodic orbits are also investigated. Using the continuation scheme, we obtain the spatial lunar periodic orbit families. The characters of the periodic orbit families are discussed in detail. In addition, some applications of the spatial lunar periodic orbits are given. The method to investigate the long-term behavior of the spatial lunar orbits we present is simple and direct. We can easily locate the lunar quasi-periodic orbit and obtain the spatial periodic orbit family.

Description: Compact stars serve as a logical regimen for the implementation of theoretical models that are difficult to understand from an experimental setup. In our present work, we discuss the stability of self-gravitating compact objects by using the concept of cracking in the linear regime. We investigate the effect of density perturbation and local anisotropy on the stability regions of the following compact objects, neutron star PSR J1614-2230, the millisecond pulsar PSR J1903+327 and X-ray pulsars Vela X-1, SMC X-1, Cen X-3. We find that SMC X-1 is the stable compact object and all other exhibit cracking.

Description: In this paper, non-diagonal Bianchi type-IV space-time is investigated in Einstein general theory of relativity. The matter field is considered in the form of perfect dark energy fluid. It is interesting to observe that in this case, Bianchi type IV perfect dark energy fluid cosmological model does not exist. The space-time reduces to Minkowskian geometry.

Description: We propose a new model of modified \(F(R)\) gravity theory with the function \(F(R) = (1/\beta) \arcsin(\beta R)\) . Constant curvature solutions corresponding to the flat and de Sitter spacetime are obtained. The Jordan and Einstein frames are considered; the potential and the mass of the scalar degree of freedom are found. We show that the flat spacetime is stable and the de Sitter spacetime is unstable. The slow-roll parameters \(\epsilon\) , \(\eta\) , and the \(e\) -fold number of the model are evaluated in the Einstein frame. The index of the scalar spectrum power-law \(n_{s}\) and the tensor-to-scalar ratio \(r\) are calculated. Critical points of autonomous equations for the de Sitter phase and the matter dominated epoch are found and studied. We obtain the approximate solution of equations of motion which is the deviation from the de Sitter phase in the Jordan frame. It is demonstrated that the model passes the matter stability test.

Description: We describe the data processing pipeline developed to reduce the pointing observation data of Lunar-based Ultraviolet Telescope (LUT), which belongs to the Chang’e-3 mission of the Chinese Lunar Exploration Program. The pointing observation program of LUT is dedicated to monitor variable objects in a near-ultraviolet (245–345 nm) band. LUT works in lunar daytime for sufficient power supply, so some special data processing strategies have been developed for the pipeline. The procedures of the pipeline include stray light removing, astrometry, flat fielding employing superflat technique, source extraction and cosmic rays rejection, aperture and PSF photometry, aperture correction, and catalogues archiving, etc. It has been intensively tested and works smoothly with observation data. The photometric accuracy is typically ∼0.02 mag for LUT 10 mag stars (30 s exposure), with errors come from background noises, residuals of stray light removing, and flat fielding related errors. The accuracy degrades to be ∼0.2 mag for stars of 13.5 mag which is the \(5\sigma\) detection limit of LUT.

Description: In the Generalized Uncertainty Principle (GUP), there should be a minimal black hole whose size is comparable to the minimal length so that it cannot evaporate completely through the thermal radiation. Again, the black hole is not allowed to have a mass less than a scale of order Planck mass, which suggested a black hole remnant. We study the warped AdS 3 rotating black hole and calculate the entropy, heat capacity and critical mass with the help of GUP. We compute the area theorem with GUP correction.

Description: The standard cosmological parallax–distance formula, as found in the literature, including text-books and reference books on cosmology, requires a correction. This correction stems from the fact that in the standard text-book derivation it has been ignored that any chosen baseline in a gravitationally bound system does not partake in the cosmological expansion. Though the correction is available in the literature for some time, the text-books still continue to use the older, incorrect formula, and its full implications are not yet fully realized. Apart from providing an alternate correct, closed-form expression that is more suitable and convenient for computations for certain limiting cases of FRW ( \(\varLambda=0\) ) world models, we also demonstrate how one can compute parallax distance for the currently favored flat-space accelerating-universe ( \(\varLambda〉0\) , \(k=0\) ) cosmologies. Further, we show that the correction in parallax distance at large redshifts could amount to a factor of three or even more. Moreover, even in an infinite universe the parallax distance does not increase indefinitely with redshift and that even the farthest possible observable point may have a finite parallax angle, a factor that needs to be carefully taken into account when using distant objects as the background field against which the parallax of a foreground object is to be measured. Some other complications that could arise in parallax measurements of a distant source, like that due to the deflection of incoming light by the gravitation field of the Sun and other planetary bodies in the solar system, are pointed out.

Description: The propagation of non-linear electromagnetic waves is carefully analyzed on a curved spacetime created by static spherically symmetric mass and charge distribution. We compute how non-linear electrodynamics affects the geodesic deviation and the redshift of photons propagating near this massive charged object. In the first order approximation, the effects of electromagnetic self-interaction can be distinguished from the usual Reissner–Nordström terms. In the particular case of Euler–Heisenberg effective Lagrangian, we find that these self-interaction effects might be important near extremal compact charged objects.

Description: The behavior of short-term oscillations (≤one solar rotation) of the solar-wind parameters, galactic cosmic rays and geomagnetic indices are discussed during the last two solar minima between cycles \(22/23\) and cycles \(23/24\) . There are strong signatures of short-term oscillations of all the selected time series during the early phase of the minima, where the high speed streams are prominent structures in the heliosphere and these signatures almost die out at the end of the two minima. Result also suggests that the second and third harmonics of one solar rotation period of few parameters are prominent during the minimum between the cycles 22 and 23. Moreover, all the sub-harmonics/quasi-oscillations are more consistent and deviate less during the recent deep prolonged minimum. Through this work, we are reporting ∼7.1 days, ∼5.5 days, ∼4.4 days, ∼3.3 days oscillations, observed in few solar-wind parameters [interplanetary magnetic field \((B)\) , RMS standard deviation in the magnetic field ( \(\sigma_{B}\) ), southward component of magnetic field \((\mathit{Bz})\) and electric field \((\mathit{Ey})\) ] and geomagnetic ( \(D_{\mathit{sT}}\) and \(\mathit{AE}\) ) parameters during the solar minimum between cycles 23 and 24, in addition to ∼1.9 days oscillations which is observed in \(\mathit{Bz}\) , \(\mathit{Ey}\) and \(\mathit{AE}\) parameters.

Description: We consider the cosine Natural inflation model that is a good candidate to explain the initial accelerating phase of the universe. By computing the inflationary parameters in Einstein frame, we construct a consistency relation between the scalar spectral index, tensor-to-scalar ratio, as well as the running of the scalar spectral index and compare the results with recently released Planck 2015 observational data. Our results show that a Natural Inflation model in Einstein frame has a good agreement with the observational data.

Description: In this paper, we investigate \(f(T)\) cosmology and find an exact solution for \(f\) which gives a Little Rip cosmology. Also, considering accelerating cosmology with dark matter, the time-dependent solution is found. For these cases, by using solutions obtained from \(f(T)\) gravity we find expressions for \(\omega\) and \(\varLambda\) defined as time functions via equivalent description in terms of inhomogeneous fluid. This puts the question: which theoretical model describes the observational cosmology?

Description: A new class of solutions for Einstein’s field equations representing a static spherically symmetric anisotropic distribution of matter is obtained on the background of pseudo-spheroidal spacetime. We have prescribed the bounds of the model parameters \(k \) and \(p_{0} \) on the basis of the elementary criteria for physical acceptability, viz., regularity, stability and energy conditions. By taking the values of model parameters from the prescribed bounds, we have shown that our model is compatible with the observational data of a wide variety of compact stars like 4U 1820-30, PSR \(\mathrm{J}1903{+}327\) , 4U 1608-52, Vela X-1, PSR J1614-2230, SMC X-4 and Cen X-3.

Description: In this paper we perform the reconstruction scheme of the gravitational action within \(f(T,\mathcal{T})\) gravity, where \(T\) and \(\mathcal{T}\) denote the torsion scalar and the trace of the energy momentum tensor, respectively. We particularly focus our attention on the case where the algebraic function \(f(T,\mathcal{T})\) is decomposed as a sum of two functions \(f_{1}(T)\) and \(f_{2}(\mathcal{T})\) , i.e., \(f(T,\mathcal{T})=f_{1}(T)+f_{2}(\mathcal{T})\) . The description is essentially based on the scale factor and then, we consider two interesting and realistic expressions of this parameter and reconstruct the action corresponding to each phase of the universe. Our results show that some \(f(T,\mathcal{T})\) models are able to describe the evolution of the universe from the inflation phase to the late time dark energy dominated phase.

Description: Here 28 BL Lac objects, 18 FR I type radio galaxies, 4 FR I/II type radio galaxies and 10 FR II type radio galaxies are studied from FIR (far infrared) to optical region (180 μm to 0.44 μm) to understand the nature of infrared emission from these objects and the physical properties of dust in the emitting region. Using the flux densities from 2MASS, IRAS, ISO, SCUBA (40 % samples), WISE All-sky Data, AKARI (10 % samples) data and optical (B) observations, the spectral energy distributions are constructed. FIR and NIR spectral indices ( \(\alpha_{\mathrm{FIR}}\) and \(\alpha_{\mathrm{NIR}}\) ) are estimated. The dust temperatures and dust masses of all the samples are estimated from FIR flux densities. The SEDs of most of the samples (90 %) show steep slopes from FIR to optical region and about 10 % of the samples show flat continuous spectra from FIR to NIR region. The SEDs of 80 % FR I type radio galaxies and 1 out of 4 FR I/II type radio galaxies and two RBLs show a bump in the NIR to optical region. The SEDs of these sources are compared with Radiative transfer models. From FIR to MIR region, the SEDs of 90 % of the objects studied here can be fitted to the models with luminosities \(\mathrm{L}\sim 10^{9.5} \mathrm{L}_{0}\) , considering uncertainty from 10 % to 20 %. But the observable fluxes in the NIR region are higher and can be fitted to other models with higher \(\mathrm{L}\sim 10^{12.5} \mathrm{L}_{0}\) . Since there is a difference in emission in NIR region, mainly for FR I radio galaxies, so the variation of apparent K magnitudes with logarithm of redshift z is also studied. The WISE colours, ( \(\mathrm{W}_{1} - \mathrm{W}_{2}\) ) and ( \(\mathrm{W}_{2} - \mathrm{W}_{3}\) ) are compared with isodensity contours. Comparing with radiative transfer models it can be suggested that, in the FIR and MIR region the infrared emission is from the dust containing large grains, small graphites and PAHs at temperature ∼50 K–100 K. In the NIR region hot dust is mainly due to small grains at temperature ∼1200 K and the emission is mainly from synchrotron radiation produced in the inner part of the relativistic jets. The dust masses of RBLs are higher than those of XBLs and IBLs. FR II radio galaxies also have higher dust masses and that is mainly due to the clumpy dust which is very seldom in FR I radio galaxies. Dust clearly plays an important role in the evolution of these objects.

Description: We are interested in the periodic motion and bifurcations near the surface of an asteroid. The gravity field of an irregular asteroid and the equation of motion of a particle near the surface of an asteroid are studied. The periodic motions around the major body of triple asteroid 216 Kleopatra and the OSIRIS-REx mission target-asteroid 101955 Bennu are discussed. We find that motion near the surface of an irregular asteroid is quite different from the motion near the surface of a homoplastically spheroidal celestial body. The periodic motions around the asteroid 101955 Bennu and 216 Kleopatra indicate that the geometrical shapes of the orbits are probably very sophisticated. There exist both stable periodic motions and unstable periodic motions near the surface of the same irregular asteroid. This periodic motion which is unstable can be resonant or non-resonant. The period-doubling bifurcation and pseudo period-doubling bifurcation of periodic orbits coexist in the same gravity field of the primary of the triple asteroid 216 Kleopatra. It is found that both of the period-doubling bifurcations of periodic orbits and pseudo period-doubling bifurcation of periodic orbits have four different paths. The pseudo period-doubling bifurcation found in the potential field of primary of triple asteroid 216 Kleopatra shows that there exist stable periodic orbits near the primary’s equatorial plane, which gives an explanation for the motion stability of the triple asteroid 216 Kleopatra’s two moonlets, Alexhelios and Cleoselene.

Description: Properties of nonlinear ion-acoustic travelling waves propagating in a three-dimensional multicomponent magnetoplasma system composed of positive ions, negative ions and superthermal electrons are considered. Using the reductive perturbation technique (RPT), the Zkharov-Kuznetsov (ZK) equation is derived. The bifurcation theory of planar dynamical systems is applied to investigate the existence of the solitary wave solutions and the periodic travelling wave solutions of the resulting ZK equation. It is found that both compressive and rarefactive nonlinear ion-acoustic travelling waves strongly depend on the external magnetic field, the unperturbed positive-to-negative ions density ratio, the direction cosine of the wave propagation vector with the Cartesian coordinates, as well as the superthermal electron parameter. The present model may be useful for describing the formation of nonlinear ion-acoustic travelling wave in certain astrophysical scenarios, such as the D and F-regions of the Earth’s ionosphere.

Description: In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy \(\gamma\) -ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi -Large Area Telescope. We report the detection of 19 new high-energy \(\gamma\) -ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

Description: In this paper, capturing Near-Earth asteroids (NEAs) into bounded orbits around the Earth is investigated. Several different potential schemes related with gravity assists are proposed. A global optimization method, the particle Swarm Optimization (PSO), is employed to obtain the minimal velocity increments for each scheme. With the optimized results, the minimum required velocity increments as well as the mission time are obtained. Results of numerical simulations also indicate that using MGAs is an efficient approach in the capturing mission. The conclusion complies with the analytical result in this paper that a NEA whose velocity relative to the Earth less than 1.8 km/s can be captured by Earth by just one MGA. For other situations, the combination of MGAs and EGAs is better in sense of the required velocity-increments.

Description: We investigate the gauged Nambu-Jona-Lasinio model in curved space-time at the large \(N_{c}\) limit and in slow-roll approximation. The model can be described by the renormalization group corrected gauge-Higgs-Yukawa theory with the corresponding compositeness conditions. Evaluating the renormalization group (RG) improved effective action, we show that such model can produce CMB fluctuations and find inflationary parameters: spectral index, tensor-to-scalar-ratio and running of the spectral index. We demonstrate that the model can naturally satisfy the Planck 2015 data and maybe considered as an alternative candidate for Higgs inflation.

Description: Nonlinear ion acoustic shocks in homogenous multicomponent electron-positron-ion (e-p-i) dissipative magneto rotating plasmas are studied. Dissipation in the plasma system is included via kinematic viscosity of ions. The electrons and positrons are Lorentzian and following kappa distribution function. Reductive perturbation technique is applied to derive Korteweg de Vries Burgers (KdVB) equation. The effects of variation of positron density, positron spectral index, temperature ratio of kappa distributed electrons to kappa distributed positrons, ion kinematic viscosity and rotational frequency effects are discussed in the context of pulsar magnetosphere.

Description: We here apply the ASTG-model to the observed secular trend in the mean Sun-(Earth-Moon) and Earth-Moon distances thereby providing an alternative explanation as to what the cause of this secular trend may be. Within the margins of observational error; for the semi-major axis rate of the Earth-Moon system, in agreement with observations (of Standish and Kurtz, Proceedings IAU Colloquium, IAU, pp. 163–179, Cambridge University Press, Cambridge, 2005 ), we obtain a value of about +(5.10±0.10) cm/yr. The ASTG-model predicts orbital drift as being a result of the orbital inclination and the Solar mass loss rate. The Newtonian gravitational constant G is assumed to be an absolute time constant. Krasinsky and Brumberg (Celest. Mech. Dyn. Astron. 90(3–4):267–288, 2004 ); Standish and Kurtz ( 2005 ) reported for the Earth-Moon system, an orbital recession from the Sun of about +(15.00±4.00) cm/yr and +(7.00±2.00) cm/yr respectively; while Williams et al. (Phys. Rev. Lett. 93:261101, 2004 ); Williams and Boggs (Proceedings of 16th International Workshop on Laser Ranging, Space Research Centre, Polish Academy of Sciences, Poland, 2009 ), Williams et al. (Planet. Sci. 3(1):2, 2014 ) report for the Moon, a semi-major axis rate of about +(38.08±0.04) mm/yr from the Earth. The predictions of the ASTG-model for the Earth-Moon system agrees very well with those the findings of Standish and Kurtz ( 2005 ), Krasinsky and Brumberg ( 2004 ). The lost orbital angular momentum for the Earth-Moon system—which we here hypothesize to be gained as spin by the two body Earth-Moon system; this lost angular momentum accounts very well for the observed Lunar drift, therefore, one can safely say that the ASTG-model does to a reasonable degree of accuracy predict the observed Lunar semi-major axis rate of about +(38.08±0.04) mm/yr from the Earth.

Description: We present a photometric study for three rarely studied open star clusters; Juchert-Saloranta 1, Teutsch 1 and Teutsch 5 using the 2MASS-JHKs photometric data. Their structural and photometric parameters are determined. We obtained the distance from the Sun of 3.30±0.30 kpc, 3.82±0.25 kpc and 2.91±0.34 kpc and their log(age) of 9.15, 8.75 and 8.9 at solar metallicity and the total mass of 215, 807 and 165  M ⊙ for Juchert-Saloranta 1, Teutsch 1 and Teutsch 5 respectively. The three clusters lie in the galactic plane and about 11 kpc from the galactic center. The relaxation times of the clusters are smaller than the estimated cluster ages (∼0.01) that may be reflect the dynamical relaxation of these clusters.

Description: Finding analytical solutions to the eddy current torque produced by a conducting body rotating within a magnetic field is arduous. In this paper, the finite difference method is adopted to solve numerically the boundary problem regarding the distributions of eddy currents in determining eddy current torque. Through analysis of the solutions, this paper presents the expression of eddy current torque that applies to a model of arbitrary shape rotating around an arbitrary axis. The parameters of the physical properties of the rigid body are integrated into the eddy current torque tensor, the features of which are analogous to the inertia tensor. The elements in the tensor are constants for a specific rigid body; thus, in the expression, the torque is associated only with the relative angular velocity and magnetic field. The expression is used to investigate the evolution of the rotation of space debris subjected to eddy current torque, through numerical integration with the angular velocity of the variation of the geomagnetic field, which is assumed a dipole. The results explain the observed phenomenon of change in the spin decay rate. Moreover, the effects of gravity-gradient torque and orbit precession cause the self-spin of the space debris to resonate with the orbital motion and ultimately, to reach a steady state.

Description: Analysis of rapid variability at 4.85 GHz for the BL Lac object 0925+504 is presented and discussed. The structure functions (SF) are investigated with both refractive and weak interstellar scintillation (RISS/WISS) models analytically. Parameters obtained with these models are quantitatively compared, suggesting that the emission region of IDV is remarkably compact and the responsible interstellar scintillation medium (ISM) lies very close to the observer. Furthermore possible evidence of annual modulation of the variability timescales is detected in this source. Our findings indicate that the observed rapid variability in 0925+504 is predominantly caused by a scattering screen located along the line of sight to the source, at a distance of ∼110 pc to the observer.

Description: Inhomogeneous fluid models for warm inflation are investigated. The early-time acceleration is supported by inhomogeneous fluid whose coupling with radiation leads to the radiation dominated era after inflation. Several examples are analyzed, strong dissipation regime is discussed, and the viability of the models respect to the last Planck data is verified.

Description: Although the tunneling approach is fully established for black holes radiation, much work has been done to support the extension of this approach to more general settings. In this paper the Parikh-Kraus-Wilczeck proposal of black holes tunneling radiation is considered. The spherically symmetric black holes thermodynamics and tunneling radiation are studied based on the generalized uncertainty principle (GUP) and the modified dispersion relation (MDR) analysis. It is shown that entropy, temperature and the original Parikh-Kraus-Wilczek calculation of the black hole tunneling radiation receive some corrections. Through comparison, the results of these two alternative approaches are shown to be identical if one uses the suitable expansion coefficients.

Description: We study a charged compact object with anisotropic pressures in a core envelope setting. The equation of state is quadratic in the core and linear in the envelope. There is smooth matching between the three regions: the core, envelope and the Reissner-Nordström exterior. We show that the presence of the electric field affects the masses, radii and compactification factors of stellar objects with values which are in agreement with previous studies. We investigate in particular the effect of electric field on the physical features of the pulsar PSR J1614-2230 in the core envelope model. The gravitational potentials and the matter variables are well behaved within the stellar object. We demonstrate that the radius of the core and the envelope can vary by changing the parameters in the speed of sound.

Description: A catalog of 4231 Galactic H 2 CO absorption lines ( \(\sim 2241\) sources) at 6 cm has been collected from the literature published up to 2014. The distribution of these H 2 CO absorption lines has been compared with the OH masers at 18 cm in the Milky Way. Most of the OH masers are distributed in the inner Galaxy ( \(-75^{\circ} 〈 l 〈 75^{\circ}\) ) with a higher Galactic latitude than the H 2 CO sources ( \(-5^{\circ} 〈 b 〈 5^{\circ}\) ). The longitude-velocity distributions of H 2 CO and OH show that the majority of the objects are located in the molecular ring following the CO molecular gas distribution. The range of velocities of the OH masers is larger and distribution more diffuse than the H 2 CO sources in the Galactic longitude range \(30^{\circ} 〈 l 〈 90^{\circ}\) . The H 2 CO sources have been matched with the four ground state transitions of OH and a close associations have been found with H 2 CO clouds with small velocity differences ( \(〈5~\mbox{km}\,\mbox{s}^{-1}\) ). The H 2 CO sources observed with a higher resolution telescope have a better correlation with the OH maser, which may imply a common excitation process and may be attributed to shock excitation. The correlation index of the 1720 MHz OH for the relations \(L_{\mathrm{OH}}\) – \(L_{\mathrm{H}_{2}\mathrm{CO}}^{\alpha}\) and \(L_{\mathrm{OH}}\) – \(L_{\mathrm{IR}}^{\alpha}\) is much weaker as compared with 1612, 1665, and 1667 MHz OH transitions. The correlation between H 2 CO and the interstellar OH maser is much stronger than between H 2 CO and the stellar OH maser. Similarly the correlation is stronger for the presence than for the absence of far-infrared radiation (FIR) sources. This may indicate that both the FIR and the radio continuum connects the OH with H 2 CO characteristics.

Description: In a recent work, a particular class of \(f(T)\) gravity, where \(T\) is the teleparallel torsion scalar, has been derived. This class has been identified by flat-like universe (FLU) assumptions (El Hanafy and Nashed 2015 ). The model is consistent with the early cosmic inflation epoch. A quintessence potential has been constructed from the FLU \(f(T)\) -gravity. We show that the first order potential of the induced quintessence is a quasi inverse power law inflation with an additional constant providing an end of the inflation with no need to an extra mechanism. At \(e\) -folds \(N_{*}= 55\) before the end of the inflation, this type of potential can perform both \(E\) and \(B\) modes of the cosmic microwave background (CMB) polarization pattern.

Description: We have statistically studied 220 events from 1996 to 2008 (i.e. solar cycle 23). Two set of flare-CME is examined one with Deca-hectometric (DH) type II and other without DH type II radio burst. Out of 220 events 135 (flare-halo CME) are accompanied with DH type II radio burst and 85 are without DH type II radio burst. Statistical analysis is performed to examine the distribution of solar flare-halo CME around the solar disk and to investigate the relationship between solar flare and halo CME parameters in case of with and without DH type II radio burst. In our analysis we have observed that: (i) 10–20° latitudinal belt is more effective than the other belts for DH type II and without DH type II radio burst. In this belt, the southern region is more effective in case of DH type II radio burst, whereas in case of without DH type II radio burst dominance exits in the northern region. (ii) 0–10° longitudinal belt is more effective than the other belts for DH type II radio burst and without DH type II radio burst. In this belt, the western region is more effective in case of DH type II radio burst, while in case of without DH type II radio burst dominance exits in the eastern region. (iii) Mean speed of halo CMEs (1382 km/s) with DH type II radio burst is more than the mean speed of halo CMEs (775 km/s) without DH type II radio burst. (iv) Maximum number of M-class flares is found in both the cases. (v) Average speed of halo CMEs in each class accompanied with DH type II radio burst is higher than the average speed of halo CMEs in each class without DH type II radio burst. (vi) Average speed of halo CMEs, associated with X-class flares, is greater than the other class of solar flares in both the cases.

Description: In this paper, a three dimensional case of the restricted four-body problem with radiation pressure is considered. The three primaries are supposed to be in a collinear central configuration where both masses and both radiation forces of peripheral bodies are equal. In addition to the analysis of the equilibria in the planar problem introduced in a previous paper by the authors, we present here a complete study of position and stability of the equilibrium points out of \(\mathit{Oxy}\) plane.

Description: Investigations of thermal evolution of neutron stars with hyperon cores require neutrino emissivities for many neutrino reactions involving strongly degenerate particles (nucleons, hyperons, electrons, muons). We calculate the angular integrals \(I_{n}\) (over orientations of momenta of \(n\) degenerate particles) for major neutrino reactions with \(n=3, 4, 5\) at all possible combinations of particle Fermi momenta. The integrals \(I_{n}\) are necessary ingredients for constructing a uniform database of neutrino emissivities in dense nucleon–hyperon matter. The results can also be used in many problems of physical kinetics of strongly degenerate systems.

Description: We study motion and collision of particles in the gravitational field of rotating black hole immersed in quintessential dark energy characterized with the quintessential parameter \(\omega_{q}\in(-1;-1/3)\) governing the equation of state of the dark energy, and the dimensionless quintessential field parameter  \(\tilde{c}\) . We focus on the acceleration of particles due to collisional processes and show how the center of mass energy depends on the quintessential field parameter \(\tilde{c}\) . We also make comparison of the obtained results to the collisional energetics of quintessential static black holes demonstrating the crucial role of the rotation parameter \(a\) in the particle acceleration. Finally we study the dependence of the maximal value of the efficiency of energy extraction through Penrose process for rotating black hole with quintessential field parameter  \(\tilde{c}\) . It is found that quintessence field decreases the energy extraction efficiency through Penrose process and when the parameter \(\tilde{c}\) vanishes one can get the standard value of the efficiency coefficient for the Kerr black hole as \(\eta\sim 21~\%\) .

Description: Intermediate polars with known rates of spin period changes are not numerous because such tasks require measurements performed for a long time. To measure a spin period change, MU Cam is a good candidate because it has a spin oscillation with a large amplitude enabling measurements with high precision. Fortunately, in the past the spin period of MU Cam was measured with high precision. To measure the spin period anew, in 2014–2015 we performed extensive photometric observations of MU Cam, spanning a total duration of 208 h within 46 nights. We found that the spin, sideband and orbital periods are equal to \(1187.16245\pm0.00047~\mbox{s}\) , \(1276.3424\pm0.0022~\mbox{s}\) and \(4.71942\pm0.00016~\mbox{h}\) , respectively. Comparing the measured spin period with the spin period of MU Cam in the past, we detected the spin period change with \(\mathrm{d}P/{\mathrm{d}}t=-(2.17\pm0.10)\times 10^{-10}\) . This rate of the spin period change was not stable and varied in a time scale of years. During four nights in 2014 April–May MU Cam was fainter than usual by 0.8 mag, and the amplitude of the sideband oscillation was five times larger, denoting significant fraction of disc-overflow accretion. The sideband oscillation showed a double-peaked pulse profile in the normal brightness state. When the star brightness was decreased by 0.8 mag, the sideband oscillation showed a single-peaked pulse profile. In contrast, the spin pulse, which was quasi-sinusoidal, remained remarkably stable both in profile and in amplitude. Moreover, the spin pulse was also remarkably stable in a time scale of years and even decades. MU Cam is of great interest because it represents a distinctive object with a large and unstable rate of the spin period change and exhibits a distinctive behaviour of the pulse profiles.

Description: The detection of anomalies in gravitational microlensing events is nowadays one of the main goals among the microlensing community. In the case of single-lens events, these anomalies can be caused by the finite source effects, that is when the source disk size is not negligible, and by the Earth rotation around the Sun (the so-called parallax effect). The finite source and parallax effects may help to define the mass of the lens, uniquely. Free-floating planets (FFPs) are extremely dim objects, and gravitational microlensing provides at present the exclusive method to investigate these bodies. In this work, making use of a synthetic population algorithm, we study the possibility of detecting the finite source and parallax effects in simulated microlensing events caused by FFPs towards the Galactic bulge, taking into consideration the capabilities of the space-based Euclid telescope. We find a significant efficiency for detecting the parallax effect in microlensing events with detectable finite source effect, that turns out to be about 51 % for mass function index \(\alpha_{\mathrm{PL}} = 1.3\) .

Description: In this paper, we present a model of transitioning universe with minimal interaction between perfect fluid and anisotropic dark energy in Bianchi I space-time. The two sources are assumed to minimally interacted and therefore their energy momentum tensors are conserved separately. The explicit expression for average scale factor are considered in hybrid form that gives time varying deceleration parameter which describes both the early and late time physical features of universe. We also discuss the physical and geometrical properties of the model derived in this paper. The solution is interesting physically as it explain accelerating universe as well as singularity free universe.

Description: The next generation interferometric radio telescope, the Square Kilometre Array (SKA), which will be the most sensitive and largest radio telescope ever constructed, could greatly contribute to the detection, survey and characterization of Gamma Ray Bursts (GRBs). By the SKA, it will be possible to perform the follow up of GRBs even for several months. This approach would be extremely useful to extend the Spectrum Energetic Distribution (SED) from the gamma to the to radio band and would increase the number of radio detectable GRBs. In principle, the SKA could help to understand the physics of GRBs by setting constraints on theoretical models. This goal could be achieved by taking into account multiple observations at different wavelengths in order to obtain a deeper insight of the sources. Here, we present an estimation of GRB radio detections, showing that the GRBs can really be observed by the SKA. The approach that we present consists in determining blind detection rates derived by a very large sample consisting of merging several GRB catalogues observed by current missions as Swift , Fermi , Agile and INTEGRAL and by previous missions as BeppoSAX, CGRO, GRANAT, HETE-2, Ulysses and Wind. The final catalogue counts 7516 distinct sources. We compute the fraction of GRBs that could be observed by the SKA at high and low frequencies, above its observable sky. Considering the planned SKA sensitivity and through an extrapolation based on previous works and observations, we deduce the minimum fluence in the range 15–150 keV. This is the energy interval where a GRB should emit to be detectable in the radio band by the SKA. Results seem consistent with observational capabilities.

Description: Obtaining exact solutions of the spherically symmetric general relativistic gravitational field equations describing the interior structure of an isotropic fluid sphere is a long standing problem in theoretical and mathematical physics. The usual approach to this problem consists mainly in the numerical investigation of the Tolman-Oppenheimer-Volkoff and of the mass continuity equations, which describes the hydrostatic stability of the dense stars. In the present paper we introduce an alternative approach for the study of the relativistic fluid sphere, based on the relativistic mass equation, obtained by eliminating the energy density in the Tolman-Oppenheimer-Volkoff equation. Despite its apparent complexity, the relativistic mass equation can be solved exactly by using a power series representation for the mass, and the Cauchy convolution for infinite power series. We obtain exact series solutions for general relativistic dense astrophysical objects described by the linear barotropic and the polytropic equations of state, respectively. For the polytropic case we obtain the exact power series solution corresponding to arbitrary values of the polytropic index  \(n\) . The explicit form of the solution is presented for the polytropic index \(n=1\) , and for the indexes \(n=1/2\) and \(n=1/5\) , respectively. The case of \(n=3\) is also considered. In each case the exact power series solution is compared with the exact numerical solutions, which are reproduced by the power series solutions truncated to seven terms only. The power series representations of the geometric and physical properties of the linear barotropic and polytropic stars are also obtained.

Description: We look at viscosity production in a universe consisting purely of leptons and photons. This is quite close to what the universe actually look like when the temperature was between \(10^{10}~\mbox{K}\) and \(10^{12}~\mbox{K}\) (1–100 MeV). By taking the strong force and the hadronic particles out of the equation, we can examine how the viscous forces behave with all the 12 leptons present. By this we study how shear- and (more interestingly) bulk viscosity is affected during periods with particle annihilation. We use the theory given by Hoogeveen et al. from 1986, replicate their 9-particle results and expanded it to include the muon and tau particles as well. This will impact the bulk viscosity immensely for high temperatures. We will show that during the beginning of the lepton era, when the temperature is around 100 MeV, the bulk viscosity will be roughly 100 million times larger with muons included in the model compared to a model without.

Description: The background plasma is assumed to have generalized \((r, q)\) distribution for the electrons in the solar wind. The propagation of a beam of hot electrons through solar wind plasma with generalized \((r,q)\) distribution and the generation of Langmuir waves are simulated using quasilinear equations. It is shown that spectral indices \(r\) and \(q\) affect the quasilinear dynamics of the beam and Langmuir waves. The damping of beam generated waves increases in \((r,q)\) distributed plasma. As indices \(r\) and \(q\) increase the system shows quasilinear behavior which is more similar to the Maxwellian distribution function. The value of average velocity of the beam increases in a plasma with \((r, q)\) distribution function and as the values of \(r\) and \(q\) increase, the average velocity of the beam decreases. It is also shown that the gas-dynamical parameters of the beam are functions of spectral indices \(r\) and \(q\) . The upper boundary of the plateau, and local velocity spread are increasing functions while the lower boundary and height of plateau are decreasing functions of \(r\) and \(q\) . The local velocity shows smooth behavior with respect to spectral indices \(r\) and \(q\) , and for all indices at given time and position has approximately same values.

Description: The interaction between novae ejecta and accretion disks or circumbinary (CB) disks surrounding nova systems based on the diffusive shock acceleration (DSA) mechanism are investigated. Results suggest that interaction between the novae ejecta and CB disks most probably produce \(\gamma\) -rays. Both leptonic and hadronic scenarios can feasibly produce \(\gamma\) -rays in CB disks. A grid is calculated in order to discuss the \(\gamma\) -ray sources in classical novae (CNe), and results indicated that the mass of a white dwarf and the orbit period in CNe can greatly affect the production of \(\gamma\) -rays. According to the proposed grid and synthesis population method, it is estimated that the percentage of CNe that can produce \(\gamma\) -rays ranges from approximately 0.17 % to 51 % for leptonic scenarios when the magnetic field strength in the shock region ranges from 0.005 G to 0.02 G. The occurrence rate of \(\gamma\) -ray CNe ranges from approximately \(1~\mbox{yr}^{-1} \mbox{ to } 27~\mbox{yr}^{-1}\) in the galaxy. The corresponding percentage ranges from approximately 64 % to 97 % in hadronic scenarios, while the occurrence rate of \(\gamma\) -ray CNe ranges from approximately \(35~\mbox{yr}^{-1} \mbox{ to } 52~\mbox{yr}^{-1}\) in the galaxy.

Description: The connection between the problems of celestial mechanics: the Kepler problem, the two-center problem and the two body problem in spaces of constant curvature with the generalized Kepler and Hooke potentials is investigated. The limit passage in the two-center and two body problems in the Lobachevsky space and on a sphere is carried out as \(\lambda\to0\) ( \(\lambda\) is the curvature of the corresponding space) for the two potentials. The potentials and metrics in spaces under study are written in the gnomonic coordinates. It is shown that as the curvature radius tends to infinity, the generalized gravitational and elastic potentials transform to the Kepler and Hooke forms in the Euclidean space.

Description: The ekpyrotic phase (a slow contraction cosmic phase before the current expansion phase) manages to solve the main problems of the standard cosmology by means of a scalar field interpreted as a cosmic fluid in the Friedmann equation. Moreover, this phase generates a nearly scale-invariant spectrum of perturbations in agreement with the latest data. Then, the ekpyrotic mechanism is a serious possibility to the inflationary model. In this work—by using the approach of deforming metrics at linear level—we point out that it is impossible to generate a black hole with spherical symmetry supported by an isotropic fluid in this cosmological scenario.

Description: We present lzifu (LaZy-IFU), an idl toolkit for fitting multiple emission lines simultaneously in integral field spectroscopy (IFS) data. lzifu is useful for the investigation of the dynamical, physical and chemical properties of gas in galaxies. lzifu has already been applied to many world-class IFS instruments and large IFS surveys, including the Wide Field Spectrograph, the new Multi Unit Spectroscopic Explorer (MUSE), the Calar Alto Legacy Integral Field Area (CALIFA) survey, the Sydney-Australian-astronomical-observatory Multi-object Integral-field spectrograph (SAMI) Galaxy Survey. Here we describe in detail the structure of the toolkit, and how the line fluxes and flux uncertainties are determined, including the possibility of having multiple distinct kinematic components. We quantify the performance of lzifu , demonstrating its accuracy and robustness. We also show examples of applying lzifu to CALIFA and SAMI data to construct emission line and kinematic maps, and investigate complex, skewed line profiles presented in IFS data. The code is made available to the astronomy community through github. lzifu will be further developed over time to other IFS instruments, and to provide even more accurate line and uncertainty estimates.

Description: In this paper, we study the dynamics of tilted cylindrical model with imperfect matter distribution. We formulate the field equations and develop relations between tilted and non-tilted variables. We evaluate kinematical as well as dynamical quantities and discuss the inhomogeneity factor. We also obtain the Raychaudhuri equation to study evolution of expansion scalar. The solutions of field equations are also investigated for static cylinder under isotropy and conformally flat condition. Finally, we analyze some thermoinertial aspects of the system.

Description: In the present study, we have analyzed the field localization of kinetic Alfvén wave (KAW) due to the presence of background density perturbation, which are assumed to be originated by the three dimensionally propagating low frequency KAW. These localized structures play an important role for energy transportation at smaller scales in the dispersion range of magnetic power spectrum. For the present model, governing dynamic equations of high frequency pump KAW and low frequency KAW has been derived by considering ponderomotive nonlinearity. Further, these coupled equations have been numerically solved to analyze the resulting localized structures of pump KAW and magnetic power spectrum in the magnetopause regime. Numerically calculated spectrum exhibits inertial range having spectral index of \(-3/2\) followed by steeper scaling; this steepening in the turbulent spectrum is a signature of energy transportation from larger to smaller scales. In this way, the proposed mechanism, which is based on nonlinear wave-wave interaction, may be useful for understanding the particle acceleration and turbulence in magnetopause.

Description: We take the scalar field dark energy model possessing a non-canonical kinetic term in the framework of modified Chern-Simon gravity. We assume the flat FRW universe model and interacting scenario between dark matter and non-canonical dark energy part. Under this scenario, we check the stability of the model using squared speed of sound which represents the stable behavior for a specific choice of model parameters. We also discuss the validity of generalized second law of thermodynamics by assuming the usual entropy and its corrected forms (logarithmic and power law) at the apparent horizon. This law satisfied for all cases versus redshift parameter at the present as well as later epoch.

Description: In the current paper we have investigated a well-behaved new model of anisotropic compact star in ( \(3+1\) )-dimensional spacetime. The exterior spacetime is described by the Schwarzschild vacuum solution. The model is obtained in the background of Tolman IV \(g_{rr}\) metric potential. Our model is free from central singularities and satisfies all energy conditions. The solution is compatible with observed masses and radii of a few compact stars like Her X-1, PSR J0737-3039A, PSR B1913+16, RX J1856.5-3754, Cyg X-2 and PSR J1903+0327.

Description: We study the cosmic acceleration in dynamical Chern-Simons modified gravity in the frame-work of non-flat FRW universe. The pilgrim dark energy (with future event and apparent horizons) interacted with cold dark matter is being considered in this work. We investigate the cosmological parameters (equation of state, deceleration) and planes (state-finders, \(\omega_{\vartheta }\) – \(\omega_{\vartheta }^{\prime }\) ) in the present scenario. It is interesting to mention here that the obtained results of various cosmological parameters are consistent with various observational schemes. The validity of generalized second law of thermodynamics for present dark energy models is also being analyzed.

Description: In this paper, we investigate a simple class of Horndeski models where the scalar field plays the role of a \(k\) -essence fluid. We present several solutions for early-time universe, namely inflation and cosmological bounce, by making use of some reconstruction technique. Moreover, we furnish the formalism to calculate perturbations in FRW space-time and we compute the spectral index and the tensor-to-scalar ratio during inflation.

Description: We present here results from observations at 5.5 and 9 GHz of the Bullet cluster 1E 0657–55.8 with the Australia Telescope Compact Array (ATCA). Our results show detection of diffuse emission in the cluster. Our findings are consistent with the previous observations by Shimwell et al. ( 2014 , 2015 ) at 1.1–3.1 GHz. Morphology of diffuse structures (relic regions A and B and the radio halo) are consistent with those reported by the previous study. Our results indicate steepening in the spectral index at higher frequencies ( \(\gtrsim5.0~\mbox{GHz}\) ) for region A. The spectrum can be fit well by a broken power law. We discuss the possibility of a few recent theoretical models explaining this break in the power law spectrum, and find that a modified Diffusive Shock Acceleration (DSA) model or a turbulent reacceleration model may be relevant. Deep radio observations at high frequencies ( \(\gtrsim5~\mbox{GHz}\) ) are required for a detailed comparison with this model.

Description: The interplanetary coronal mass ejections (ICMEs) and the corotating interaction regions (CIRs) are the two most important structures of the interplanetary medium affecting the Earth and the near-Earth space environment. We study the solar wind-magnetosphere coupling during the passage of ICMEs and CIRs, in the Solar Cycle 23 (Jan. 1995–Dec. 2009), and their relative geoeffectiveness. We utilize the timings of different features of these structures, their arrival and duration. As geomagnetic parameter, we utilize high time resolution data of Dst and \(\mathit{AE}\) indices. In addition to these geomagnetic indices, we utilize the simultaneous and similar time resolution data of interplanetary plasma and field, namely, solar wind velocity, interplanetary magnetic field, its north-south component and dawn-dusk electric field. We apply the method of superposed epoch analysis. Utilizing the properties of various structures during the passage of ICMEs and CIRs, and variations observed in plasma and field parameters during their passage along with the simultaneous changes observed in geomagnetic parameters, we identify the interplanetary conditions, plasma/field parameters and their relative importance in solar wind-magnetosphere coupling. Geospace consequences of ICMEs and CIRs, and the implications of these results for solar wind-magnetosphere coupling are discussed.

Description: We discuss the interior solutions of fluid Sphere in \(f(R,T)\) gravity admitting conformal killing vectors, where \(R\) is Ricci scalar and \(T\) is trace of energy momentum tensor. The solutions corresponding to isotropic and anisotropic configurations have been investigated explicitly. Further, the anisotropic case has been dealt by the utilization of linear equation of state. The results for both cases have been interpreted graphically. The equation of state parameter, integration constants and other parameters of the theory have been chosen to find the central density equal to standard value of central density of the compact objects. The energy conditions as well as stability of the solutions have been investigated in the background of \(f(R,T)\) gravity.

Description: Spacecraft observations indicate the signatures of highly oblique kinetic Alfvén waves (KAWs) and whistler waves in the solar wind plasma. In the present work, we explore the possible role of KAWs and whistler waves in the observed solar wind magnetic turbulent spectrum. The nonlinear spatial evolution of KAW is studied including the effects of the ponderomotive force which results in intense localized structures due to the background density modification. Weak quasi-transverse whistler wave propagating through these localized structures also gets localized in the form of small-scale localized structures. We present numerically calculated magnetic power spectra for both KAW as well as for whistler wave. Our obtained results demonstrate the important role that KAWs and whistler waves play in the energy cascading from larger to smaller scales. The relevance of these results to recent spacecraft observations is also pointed out.

Description: So far the basic physical properties of matter forming a thin accretion disc in the static and spherically symmetric space–time metric of the vacuum \(f(R)\) modified gravity models (Pun et al. in Phys. Rev. D 78:024043, 2008 ) and building radiative models of thin accretion disks for both Schwarzschild and Kerr black holes in \(f(R)\) gravity (Perez et al. in Astron. Astrophys. 551:4, 2013 ) were addressed properly. Also von Zeipel surfaces and convective instabilities in \(f(R)\) -Schwarzschild(Kerr) background have been investigated recently (Alipour et al. in Mon. Not. R. Astron. Soc. 454:1992, 2015 ). In this streamline, here we study the effects of radial and angular pressure gradients on thick accretion disks in Schwarzschild geometries in a constant curvature \(f(R)\) modified gravity. Since thick accretion disks have high accretion rate, we study configuration and structure of thick disks by focusing on the effect of pressure gradient on formation of the disks. We clarify our study by assuming two types of equation of state: polytropic and Clapeyron equation of states.

Description: The thorium distribution on the lunar surface is critical for understanding the lunar evolution. This work reports a global map of the thorium distribution on the lunar surface observed by Chang’E-2 gamma-ray spectrometer (GRS). Our work exhibits an interesting symmetrical structure of thorium distribution along the two sides of the belt of Th hot spots. Some potential positions of KREEP volcanism are suggested, which are the Fra Mauro region, Montes Carpatus, Aristarchus Plateau and the adjacent regions of Copernicus Crater. Based on the lunar map of thorium distribution, we draw some conclusions on two critical links of lunar evolution: (1) the thorium abundance within the lunar crust and mantle, in the last stage of Lunar Magma Ocean (LMO) crystallization, may have a positive correlation with the depth in the crust, reaches a peak when coming through the transitional zone between the crust and mantle, and decreases sharply toward the inside of the mantle; thus, the Th-enhanced materials originated from the lower crust and the layer between the crust and mantle, (2) in PKT, KREEP volcanism might be the primary mechanism of Th-elevated components to the lunar surface, whereas the Imbrium impact acted as a relatively minor role.

Description: The long-term activity of AM Her, the prototype of polars, consists of interchanging high and low states. This analysis uses the data from the BAT/ Swift , MAXI/ ISS , and AAVSO data archives (including long CCD \(V\) -band night series) for investigating the relation of the time evolution of intensities in the hard X-ray, medium/hard X-ray, and the optical bands on super-orbital timescale in a season dominated by the long high-state episodes. The observations mapped the relation of the cyclotron and bremsstrahlung luminosities in such episodes. Although an increase of intensity of the cyclotron emission is generally accompanied by a brightening of the bremsstrahlung component, this relation differs for the individual high-state episodes. These variations were accompanied by the large changes of the optical modulation. In my view, all of these variations suggest variations of the dimensions and structure of the cyclotron emitting region(s), not only the changes of the mass accretion rate. The activity during a decline (much less steep than the state transition) from an initial very bright peak can be explained by a gradual evolution of the conditions in stratified shock regions in a single high state episode. The observed behavior in the neighboring high-state episodes is also important for explaining the mechanisms which cause the low state between them. In the interpretation, some low-state episodes cause that AM Her develops a different accretion mode than the one before entering the low state. Each high-state episode is a complex phenomenon in the history of accretion in this system.

Description: The structure of stationary, axisymmetric advection-dominated accretion disk (ADAF) around rotating black hole, using non-standard model, was examined. In this model, the transport efficiency of the angular momentum \(\alpha \) was dependent on the magnetic Prandtl number \(\alpha \propto \mathit{Pm}^{\delta } \) . The full relativistic shear stress recently obtained by a new manner, was used. By considering black hole spin and Prandtl number instantaneously, the structure of ADAFs was changed in inner and outer region of the disk. It was discovered that the accretion flow was denser and hotter in the inner region, due to the black hole spin, and in the outer region, due to the presence of Prandtl parameter. Inasmuch as the rotation of the black hole affected the transport efficiency of angular momentum in parts of the disk very close to the even horizon, then in these regions, the viscosity depended on the rotation of black hole. Also, it was discovered that the effect of the black hole spin on the structure of the disk was related to the presence of Prandtl parameter.

Description: We calculate Gamow–Teller strength distributions for \(\beta \beta\) -decay nuclei \({}^{76}\mbox{Ge}\) and \({}^{82}\mbox{Se}\) using the deformed pn-QRPA model. We use a deformed Nilsson basis and consider pairing correlations within the deformed BCS theory. Ground state correlations and two-particle and two-hole mixing states were included in our pn-QRPA model. Our calculated strength distributions were compared with experimental data and previous calculation. The total Gamow–Teller strength and centroid placement calculated in our model compares well with the measured value. We calculate \(\beta\) -decay and positron capture rates on \({}^{76}\mbox{Ge}\) and \({}^{82}\mbox{Se}\) in supernovae environments and compare them to those obtained from experimental data and previous calculation. Our study shows that positron capture rates command the total weak rates at high stellar temperatures. We also calculate energy rates of \(\beta\) -delayed neutrons and their emission probabilities.

Description: We propose the unimodular-mimetic \(F(R)\) gravity theory, to resolve cosmological constant problem and dark matter problem in a unified geometric manner. We demonstrate that such a theory naturally admits accelerating universe evolution. Furthermore, we construct unimodular-mimetic \(F(R)\) inflationary cosmological scenarios compatible with the Planck and BICEP2/Keck-Array observational data. We also address the graceful exit issue, which is guaranteed by the existence of unstable de Sitter vacua.

Description: During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015 ). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, \(R = S_{\mathrm{core}}/ S_{\mathrm{ext.}}\) , where \(S_{\mathrm{core}}\) is the core emission, while \(S_{\mathrm{ext.}}\) is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have \(\gamma\) -ray emission (from 3FGL). We compared the core-dominance parameters, \(\log R\) , between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are \(\langle \log R\rangle = 0.99\pm0.87\) for FDBs and \(\langle \log R\rangle = -0.62\pm1.15\) for the non-FDBs. A K-S test shows that the probability for the two distributions of FDBs and non-FDBs to come from the same parent distribution is near zero ( \(P =9.12\times10^{-52}\) ). Secondly, we also investigated the variability index ( \(V.I.\) ) in the \(\gamma\) -ray band for FDBs, and we found \(V.I.=(0.12 \pm0.07) \log R+(2.25\pm0.10)\) , suggesting that a source with larger \(\log R\) has larger \(V.I.\) value. Thirdly, we compared the mean values of radio spectral index for FDBs and non-FDBs, and we obtained \(\langle \alpha_{\mathrm{radio}}\rangle =0.06\pm0.35\) for FDBs and \(\langle \alpha_{\mathrm{radio}}\rangle =0.57\pm0.46\) for non-FDBs. If \(\gamma\) -rays are composed of two components like radio emission (core and extended components), then we can expect a correlation between \(\log R\) and the \(\gamma\) -ray spectral index. When we used the radio core-dominance parameter, \(\log R\) , to investigate the relationship, we found that the spectral index for the core component is \(\alpha_{\gamma}|_{\mathrm{core}} = 1.11\) (a photon spectral index of \(\alpha_{\gamma}^{\mathrm{ph}}|_{\mathrm{core}} = 2.11\) ) and that for the extended component is \(\alpha_{\gamma}|_{\mathrm{ext.}} = 0.70\) (a photon spectral index of \(\alpha_{\gamma}^{\mathrm{ph}}|_{\mathrm{ext.}} = 1.70\) ). Some discussions are also presented.

Description: Complete UV band light curve of the eclipsing binary AI Dra was observed with the Lunar-based Ultraviolet Telescope (LUT) in October 2014. It is very useful to adopt this continuous and uninterrupted light curve to determine physical and orbital parameters of the binary system. Photometric solutions of the spot model are obtained by using the W–D (Wilson and Devinney) method. It is confirmed that AI Dra is a semi-detached binary with secondary component filling its critical Roche lobe, which indicates that a mass transfer from the secondary component to the primary one should happen. Orbital period analysis based on all available eclipse times suggests a secular period increase and two cyclic variations. The secular period increase was interpreted by mass transfer from the secondary component to the primary one at a rate of \(4.12 \times10^{-8}M_{\odot}/\mbox{yr}\) , which is in agreement with the photometric solutions. Two cyclic oscillations were due to light travel-time effect (LTTE) via the presence of two cool stellar companions in a near 2:1 mean-motion resonance. Both photometric solutions and orbital period analysis confirm that AI Dra is a mass-transferring binary, the massive primary is filling 69 % of its critical Roche lobe. After the primary evolves to fill the critical Roche lobe, the mass transfer will be reversed and the binary will evolve into a contact configuration.

Description: We present the results of a photon cluster search in the 7-years Fermi -Large Area Telescope extragalactic Pass 8 \(\gamma\) -ray sky by means of the Minimum Spanning Tree (MST) algorithm, at energies higher than 10 GeV. We found 16 clusters of photons, corresponding to candidate \(\gamma\) -ray sources, located very close to infrared-selected sources in the 1WHSP (WISE High Synchrotron Peaked) sample, and therein classified as either “new” or “candidate” blazars. In this paper some properties of the MST clusters and of the associated sources are presented.

Description: In this paper we use the planar circular restricted three-body problem where one of the primary bodies is an oblate spheroid or an emitter of radiation in order to determine the basins of attraction associated with the equilibrium points. The evolution of the position of the five Lagrange points is monitored when the values of the mass ratio \(\mu \) , the oblateness coefficient \(A_{1}\) , and the radiation pressure factor \(q\) vary in predefined intervals. The regions on the configuration \((x,y)\) plane occupied by the basins of attraction are revealed using the multivariate version of the Newton-Raphson method. The correlations between the basins of convergence of the equilibrium points and the corresponding number of iterations needed in order to obtain the desired accuracy are also illustrated. We conduct a thorough and systematic numerical investigation demonstrating how the dynamical quantities \(\mu \) , \(A_{1}\) , and \(q\) influence the basins of attractions. Our results suggest that the mass ratio and the radiation pressure factor are the most influential parameters, while on the other hand the structure of the basins of convergence are much less affected by the oblateness coefficient.

Description: We present the results of a photon cluster search in the \(\gamma\) -ray sky observed by the Fermi Large Area Telescope, using the new Pass 8 dataset, at energies higher than 10 GeV. By means of the Minimum Spanning Tree (MST) algorithm, we found 25 clusters associated with catalogued blazars not previously known as \(\gamma\) -ray emitters. The properties of these sources are discussed.

Description: In this paper, we have studied exact solutions of Brans-Dicke (BD) theory for higher dimensional generalized Friedmann-Robertson-Walker (FRW) universe in the presence of strange quark matter (SQM) attached to the string cloud and domain walls. We have obtained that string tension density does not survive in this model. This result agrees with Kiran and Reddy, Krori et al., Sahoo and Mishra and Reddy. Also we have obtained constant scalar field in the presence of string cloud and domain walls. Then BD theory does not observe for higher dimensional FRW universe with SQM attached to the string cloud and domain walls. Our BD solutions turn into general relativity (GR). Finally, some physical properties are discussed.

Description: In this Letter, a new conceptual approach has been presented to investigate the interaction of energetic electrons with dust whistler-mode waves in magnetospheric dusty (complex) plasmas. Dust whistler-mode waves generated in the presence of charged dust grains in the magnetized dusty plasma, can scatter the launched electrons into the loss-cone leading to precipitation into the upper atmosphere which is an important loss process in the radiation belts and provides a major source of energy for the diffuse and pulsating aurora. To study the scattered electrons and chaotic regions, a Hamiltonian model of the electron-dust wave interaction has been employed in the magnetospheric plasma by considering the launched electron beam self-fields. Numerical simulations indicate that an electron beam interacting with the whistler-mode wave can easily trigger chaos in the dust-free plasma, while in the presence of dust charged grains in the plasma, the chaotic regions are quenched to some extent in the magnetosphere. Consequently, the rate of scattered electrons into the loss-cone reduces for the regions that the dust grains are present.

Description: In this paper we study the 3D symmetric periodic orbits of the circular restricted four-body problem, through their bifurcation from plane orbits. To this end, we calculate the special generating planar periodic orbits, i.e. the vertical-critical orbits, from five basic planar families of symmetric periodic orbits of the problem. We study the simplest 3D periodic orbits and so we restrict our calculations to simple vertical bifurcation orbits leading to families of one or two revolutions three-dimensional symmetric periodic orbits. We found 21 such families of simple 3D symmetric periodic orbits and typical orbits of all symmetry type 3D orbits are presented. The stability of each calculated 3D periodic orbit is also studied. Characteristic curves as well as stability diagrams of families of 3D periodic orbits are illustrated.

Description: The Jovian InfraRed Auroral Mapper, JIRAM, is an image-spectrometer onboard the NASA Juno spacecraft flying to Jupiter. The instrument has been designed to study the aurora and the atmosphere of the planet in the spectral range 2–5 μm. The very first scientific observation taken with the instrument was at the Moon just before Juno’s Earth fly-by occurred on October 9, 2013. The purpose was to check the instrument regular operation modes and to optimize the instrumental performances. The testing activity will be completed with pointing and a radiometric/spectral calibrations shortly after Jupiter Orbit Insertion. Then the reconstruction of some Moon infrared images, together with co-located spectra used to retrieve the lunar surface temperature, is a fundamental step in the instrument operation tuning. The main scope of this article is to serve as a reference to future users of the JIRAM datasets after public release with the NASA Planetary Data System.

Description: We study the warm intermediate inflationary regime in the presence of generalized cosmic Chaplygin gas and an inflaton decay rate proportional to the temperature. For this purpose, we consider standard scalar field model during weak and strong dissipative regimes. We explore inflationary parameters like spectral index, scalar and tensor power spectra, tensor to scalar ratio and decay rate in order to compare the present model with recent observational data. The physical behavior of inflationary parameters is presented and found that all the results are agreed with recent observational data such as WMAP7, WMAP9 and Planck 2015.

Description: The famous Yukawa-type potential was very often used for explaining a great variety of recent observed astronomical phenomena which range from the solar-system scale to cosmological distances. In this paper we tackle the two-body problem in the Yukawa post-Newtonian field from the particular standpoint of orbits stability. Starting from the equations of motion and first integrals written in standard polar coordinates, we apply McGehee-type transformations of the second kind. Then we depict the phase-space structure considering the foliations by the energy constant and the angular momentum constant. Various stability regions are found for each case. The problem presents interesting features, such as: cases when all trajectories (maybe except for a separatrix) are stable; cases when there exist totally different types of orbits, both stable and unstable, for the same values of the energy constant and the angular momentum constant; the existence of stable motion for nonnegative energy levels; positive Lebesgue measure for initial data leading to quasiperiodic and noncircular periodic orbits; the key role of the angular momentum.

Description: We have investigated Bianchi type-I cosmological model in the presence of magnetized field with disordered radiation in Barber’s second self-creation theory of gravitation. To obtain exact solution we assume that the component \(\sigma^{1}_{1}\) of shear tensor \(( \sigma_{i}^{j} )\) is proportional to expansion ( θ ). Some geometrical and physical properties of the model have also been discussed.