Advances in Astronomy The latest articles from Hindawi © 2018 , Hindawi Limited . All rights reserved. Capability of the HAWC Gamma-Ray Observatory for the Indirect Detection of Ultrahigh-Energy Neutrinos Tue, 25 Jul 2017 08:07:37 +0000 The detection of ultrahigh-energy neutrinos, with energies in the PeV range or above, is a topic of great interest in modern astroparticle physics. The importance comes from the fact that these neutrinos point back to the most energetic particle accelerators in the Universe and provide information about their underlying acceleration mechanisms. Atmospheric neutrinos are a background for these challenging measurements, but their rate is expected to be negligible above ≈1 PeV. In this work we describe the feasibility to study ultrahigh-energy neutrinos based on the Earth-skimming technique, by detecting the charged leptons produced in neutrino-nucleon interactions in a high mass target. We propose to detect the charged leptons, or their decay products, with the High Altitude Water Cherenkov (HAWC) observatory and use as a large-mass target for the neutrino interactions the Pico de Orizaba volcano, the highest mountain in Mexico. In this work we develop an estimate of the detection rate using a geometrical model to calculate the effective area of the observatory. Our results show that it may be feasible to perform measurements of the ultrahigh-energy neutrino flux from cosmic origin during the expected lifetime of the HAWC observatory. Hermes León Vargas, Andrés Sandoval, Ernesto Belmont, and Rubén Alfaro Copyright © 2017 Hermes León Vargas et al. All rights reserved. Star Formation Law at Sub-kpc Scale in the Elliptical Galaxy Centaurus A as Seen by ALMA Tue, 13 Jun 2017 06:38:18 +0000 We present an extensive analysis of the relationship between star formation rate surface density () and molecular gas surface density () at sub-kpc scale in the elliptical galaxy Centaurus A (also known as NGC 5128) at the distance 3.8 Mpc. 12CO ( = 2-1) data from Atacama Large Millimetre/Sub-Millimetre Array SV data with very high resolution (2.9′′, 0.84′′), as well as 24 μm data from the Spitzer Space Telescope, were used. This is one of the first studies of the SF law on Centaurus A at this very high spatial resolution. The results showed a breakdown in star formation law with a index relating and at 185 pc. A significant correlation exists between surface densities of molecular gas and SFR with very long depletion time (68 Gy). In addition we examined the spatially resolved relationship between velocity dispersion and star formation rate surface density for the outer disk of this galaxy and we found that the average velocity dispersion is equal to 11.78 km/s. The velocity dispersion of the molecular ISM for the outer disk is found to follow a power relation with the star formation rate surface density , where β is the slope from the ordinary least square fitting. The value of β is about and is the power law index of the star formation law. Jazeel H. Azeez, Zamri Z. Abidin, C.-Y. Hwang, and Zainol A. Ibrahim Copyright © 2017 Jazeel H. Azeez et al. All rights reserved. The Observer’s Guide to the Gamma-Ray Burst Supernova Connection Tue, 11 Apr 2017 09:21:31 +0000 We present a detailed report of the connection between long-duration gamma-ray bursts (GRBs) and their accompanying supernovae (SNe). The discussion presented here places emphasis on how observations, and the modelling of observations, have constrained what we know about GRB-SNe. We discuss their photometric and spectroscopic properties, their role as cosmological probes, including their measured luminosity–decline relationships, and how they can be used to measure the Hubble constant. We present a statistical summary of their bolometric properties and use this to determine the properties of the “average” GRB-SN. We discuss their geometry and consider the various physical processes that are thought to power the luminosity of GRB-SNe and whether differences exist between GRB-SNe and the SNe associated with ultra-long-duration GRBs. We discuss how observations of their environments further constrain the physical properties of their progenitor stars and give a brief overview of the current theoretical paradigms of their central engines. We then present an overview of the radioactively powered transients that have been photometrically associated with short-duration GRBs, and we conclude by discussing what additional research is needed to further our understanding of GRB-SNe, in particular the role of binary-formation channels and the connection of GRB-SNe with superluminous SNe. Zach Cano, Shan-Qin Wang, Zi-Gao Dai, and Xue-Feng Wu Copyright © 2017 Zach Cano et al. All rights reserved. Research on Control Method of Keeping Flight Formation by Using SDRE on the Sun-Earth Libration Points Mon, 13 Feb 2017 09:43:45 +0000 Keeping the flying formation of spacecraft is a key problem which needs to be solved in deep space exploration missions. In this paper, the nonlinear dynamic model of formation flying is established and a series of transformations are carried out on this model equation. By using SDRE (State-Dependent Riccati Equation) algorithm, the optimal control of flying formation is realized. Compared with the traditional control method based on the average orbit elements and LQR (Linear Quadratic Regulator) control method, the SDRE control method has higher control precision and is more suitable for the advantages of continuous control in practical engineering. Finally, the parameter values of the sun-earth libration point L2 are substituted in the equation and simulation is performed. The simulation curves of SDRE controller are compared with LQR controller. The results show that the SDRE controllers time cost is less than the LQR controllers and the former’s fuel consumption is less than the latter’s in the system transition process. He Zhenqi, Zhang Ke, and Lv Meibai Copyright © 2017 He Zhenqi et al. All rights reserved. Modeling Kelvin–Helmholtz Instability in Soft X-Ray Solar Jets Wed, 08 Feb 2017 00:00:00 +0000 Development of Kelvin–Helmholtz (KH) instability in solar coronal jets can trigger the wave turbulence considered as one of the main mechanisms of coronal heating. In this review, we have investigated the propagation of normal MHD modes running on three X-ray jets modeling them as untwisted and slightly twisted moving cylindrical flux tubes. The basic physical parameters of the jets are temperatures in the range of 5.2–8.2 MK, particle number densities of the order of  cm−3, and speeds of 385, 437, and 532 km s−1, respectively. For small density contrast between the environment and a given jet, as well as at ambient coronal temperature of 2.0 MK and magnetic field around 7 G, we have obtained that the kink () mode propagating on moving untwisted flux tubes can become unstable in the first and second jets at flow speeds of ≅348 and 429 km s−1, respectively. The KH instability onset in the third jet requires a speed of ≅826 km s−1, higher than the observed one. The same mode, propagating in weakly twisted flux tubes, becomes unstable at flow speeds of ≅361 km s−1 for the first and of 443 km s−1 for the second jet. Except the kink mode, the twisted moving flux tube supports the propagation of higher () MHD modes that can become unstable at accessible jets’ speeds. Ivan Zhelyazkov, Ramesh Chandra, and Abhishek K. Srivastava Copyright © 2017 Ivan Zhelyazkov et al. All rights reserved. Astronomical Tasks for Tests of X-Ray Optics in VZLUSAT-1 Nanosatellite Tue, 07 Feb 2017 00:00:00 +0000 VZLUSAT-1 nanosatellite (scheduled launch in spring 2017 from India) is a CubeSat mission which, besides other instrumentation, contains X-ray desk to perform efficiency tests of the X-ray optics. In this article the analysis of potential observational candidates for VZLUSAT-1 X-ray board is presented together with the suggestion of observational modes, laboratory measurements, and estimations of exposure settings. Martin Blazek, Petr Pata, Adolf Inneman, and Petr Skala Copyright © 2017 Martin Blazek et al. All rights reserved. Analysis of the Conformally Flat Approximation for Binary Neutron Star Initial Conditions Mon, 09 Jan 2017 09:18:56 +0000 The spatially conformally flat approximation (CFA) is a viable method to deduce initial conditions for the subsequent evolution of binary neutron stars employing the full Einstein equations. Here we analyze the viability of the CFA for the general relativistic hydrodynamic initial conditions of binary neutron stars. We illustrate the stability of the conformally flat condition on the hydrodynamics by numerically evolving ~100 quasicircular orbits. We illustrate the use of this approximation for orbiting neutron stars in the quasicircular orbit approximation to demonstrate the equation of state dependence of these initial conditions and how they might affect the emergent gravitational wave frequency as the stars approach the innermost stable circular orbit. In-Saeng Suh, Grant J. Mathews, J. Reese Haywood, and N. Q. Lan Copyright © 2017 In-Saeng Suh et al. All rights reserved. High-Order Analytic Expansion of Disturbing Function for Doubly Averaged Circular Restricted Three-Body Problem Tue, 06 Dec 2016 12:59:28 +0000 Terms in the analytic expansion of the doubly averaged disturbing function for the circular restricted three-body problem using the Legendre polynomial are explicitly calculated up to the fourteenth order of semimajor axis ratio between perturbed and perturbing bodies in the inner case , and up to the fifteenth order in the outer case . The expansion outcome is compared with results from numerical quadrature on an equipotential surface. Comparison with direct numerical integration of equations of motion is also presented. Overall, the high-order analytic expansion of the doubly averaged disturbing function yields a result that agrees well with the numerical quadrature and with the numerical integration. Local extremums of the doubly averaged disturbing function are quantitatively reproduced by the high-order analytic expansion even when is large. Although the analytic expansion is not applicable in some circumstances such as when orbits of perturbed and perturbing bodies cross or when strong mean motion resonance is at work, our expansion result will be useful for analytically understanding the long-term dynamical behavior of perturbed bodies in circular restricted three-body systems. Takashi Ito Copyright © 2016 Takashi Ito. All rights reserved. Gamma-Ray Bursts: A Radio Perspective Wed, 23 Nov 2016 13:37:12 +0000 Gamma-ray bursts (GRBs) are extremely energetic events at cosmological distances. They provide unique laboratory to investigate fundamental physical processes under extreme conditions. Due to extreme luminosities, GRBs are detectable at very high redshifts and potential tracers of cosmic star formation rate at early epoch. While the launch of Swift and Fermi has increased our understanding of GRBs tremendously, many new questions have opened up. Radio observations of GRBs uniquely probe the energetics and environments of the explosion. However, currently only 30% of the bursts are detected in radio bands. Radio observations with upcoming sensitive telescopes will potentially increase the sample size significantly and allow one to follow the individual bursts for a much longer duration and be able to answer some of the important issues related to true calorimetry, reverse shock emission, and environments around the massive stars exploding as GRBs in the early Universe. Poonam Chandra Copyright © 2016 Poonam Chandra. All rights reserved. Effective Perihelion Advance and Potentials in a Conformastatic Background with Magnetic Field Sun, 20 Nov 2016 14:10:20 +0000 Exact solutions of the Einstein-Maxwell field equations for a conformastatic metric with magnetized sources are investigated. In this context, effective potentials are studied in order to understand the dynamics of the magnetic field in galaxies. We derive the equations of motion for neutral and charged particles in a spacetime background characterized by this class of solutions. In this particular case, we investigate the main physical properties of the equatorial circular orbits and related effective potentials. In addition, we obtain an effective analytic expression for the perihelion advance of test particles. Our theoretical predictions are compared with the observational data calibrated with the ephemerides of the planets of the solar system and the Moon (EPM2011). In general, we show that the magnetic punctual mass predicts values that are in better agreement with observations than the values predicted in Einstein’s gravity alone. Abraão J. S. Capistrano and Antonio C. Gutiérrez-Piñeres Copyright © 2016 Abraão J. S. Capistrano and Antonio C. Gutiérrez-Piñeres. All rights reserved. Intelligent Cognitive Radio Models for Enhancing Future Radio Astronomy Observations Mon, 17 Oct 2016 14:29:12 +0000 Radio astronomy organisations desire to optimise the terrestrial radio astronomy observations by mitigating against interference and enhancing angular resolution. Ground telescopes (GTs) experience interference from intersatellite links (ISLs). Astronomy source radio signals received by GTs are analysed at the high performance computing (HPC) infrastructure. Furthermore, observation limitation conditions prevent GTs from conducting radio astronomy observations all the time, thereby causing low HPC utilisation. This paper proposes mechanisms that protect GTs from ISL interference without permanent prevention of ISL data transmission and enhance angular resolution. The ISL transmits data by taking advantage of similarities in the sequence of observed astronomy sources to increase ISL connection duration. In addition, the paper proposes a mechanism that enhances angular resolution by using reconfigurable earth stations. Furthermore, the paper presents the opportunistic computing scheme (OCS) to enhance HPC utilisation. OCS enables the underutilised HPC to be used to train learning algorithms of a cognitive base station. The performances of the three mechanisms are evaluated. Simulations show that the proposed mechanisms protect GTs from ISL interference, enhance angular resolution, and improve HPC utilisation. Ayodele Abiola Periola and Olabisi Emmanuel Falowo Copyright © 2016 Ayodele Abiola Periola and Olabisi Emmanuel Falowo. All rights reserved. A Decade of GRB Follow-Up by BOOTES in Spain (2003–2013) Mon, 10 Oct 2016 13:15:44 +0000 This article covers ten years of GRB follow-ups by the Spanish BOOTES stations: 71 follow-ups providing 23 detections. Follow-ups by BOOTES-1B from 2005 to 2008 were given in a previous article and are here reviewed and updated, and additional detection data points are included as the former article merely stated their existence. The all-sky cameras CASSANDRA have not yet detected any GRB optical afterglows, but limits are reported where available. Martin Jelínek, Alberto J. Castro-Tirado, Ronan Cunniffe, Javier Gorosabel, Stanislav Vítek, Petr Kubánek, Antonio de Ugarte Postigo, Sergey Guziy, Juan C. Tello, Petr Páta, Rubén Sánchez-Ramírez, Samantha Oates, Soomin Jeong, Jan Štrobl, Sebastián Castillo-Carrión, Tomás Mateo Sanguino, Ovidio Rabaza, Dolores Pérez-Ramírez, Rafael Fernández-Muñoz, Benito A. de la Morena Carretero, René Hudec, Víctor Reglero, and Lola Sabau-Graziati Copyright © 2016 Martin Jelínek et al. All rights reserved. Analytic Models of Brown Dwarfs and the Substellar Mass Limit Mon, 10 Oct 2016 07:46:30 +0000 We present the analytic theory of brown dwarf evolution and the lower mass limit of the hydrogen burning main-sequence stars and introduce some modifications to the existing models. We give an exact expression for the pressure of an ideal nonrelativistic Fermi gas at a finite temperature, therefore allowing for nonzero values of the degeneracy parameter. We review the derivation of surface luminosity using an entropy matching condition and the first-order phase transition between the molecular hydrogen in the outer envelope and the partially ionized hydrogen in the inner region. We also discuss the results of modern simulations of the plasma phase transition, which illustrate the uncertainties in determining its critical temperature. Based on the existing models and with some simple modification, we find the maximum mass for a brown dwarf to be in the range . An analytic formula for the luminosity evolution allows us to estimate the time period of the nonsteady state (i.e., non-main-sequence) nuclear burning for substellar objects. We also calculate the evolution of very low mass stars. We estimate that ≃11% of stars take longer than  yr to reach the main sequence, and ≃5% of stars take longer than  yr. Sayantan Auddy, Shantanu Basu, and S. R. Valluri Copyright © 2016 Sayantan Auddy et al. All rights reserved. Space Creation Mechanism during the Expansion of Universe Wed, 28 Sep 2016 07:50:45 +0000 We propose a novel mechanism related to the expansion of universe. Recently Verlinde’s proposal has been applied to the deformed bosons being a candidate for the dark energy constituents, since the negative pressure of the deformed bosons. The expansion of universe is dependent on the dark energy and implies a creation of space; we admit that the space creation mechanism is related to the deformed bosons and so is the dark energy. In order to relate the dark energy and the mechanism for creation of space, we consider Verlinde’s proposal including the Holographic principle for emergence of space, which was recently applied to the deformed bosons. To check the validity of our mechanism, we calculate the ratio of the size of universe before and after the expansion and compare the results with the observational data. We find that the results are consistent with each other and infer that the proposed mechanism works correctly. Emre Dil Copyright © 2016 Emre Dil. All rights reserved. Atmospheric Effect on Cosmic Ray Muons at High Cut-Off Rigidity Station Thu, 25 Aug 2016 09:44:26 +0000 Cosmic ray data and radiosonde measurements from Riyadh, Saudi Arabia (Rc = 14.4 GV), for the period 2002–2012, were used to study the effect of atmospheric pressure, level of pion production, and temperature at that level, on cosmic ray muons. We found that, even if corrections were made to the detected muons using these three parameters, seasonal variations of the cosmic rays still exist. This suggests that other terrestrial and/or extraterrestrial causes may be considered. The levels of pion production and atmospheric pressure are inversely correlated with the muon rate. On the other hand, the temperature at the pion production level is correlated with muons in spring and winter and inversely correlated in fall and summer. There is no clear explanation for this behavior. Abdullrahman Maghrabi and Mohammed Almutayri Copyright © 2016 Abdullrahman Maghrabi and Mohammed Almutayri. All rights reserved. Caravan-Submm, Black Hole Imager in the Andes Wed, 20 Jul 2016 10:05:04 +0000 Imaging a black hole horizon as a shadow at the center of black hole accretion disk is another method to prove/check Einstein’s general relativity at strong gravitational fields. Such black hole imaging is expected to be achievable using a submillimeter wavelength VLBI (very long baseline interferometer) technique. Here, we introduce a Japanese black hole imaging project, Caravan-submm undertaken in the Andes. Makoto Miyoshi, Takashi Kasuga, Jose K. Ishitsuka Iba, Tomoharu Oka, Mamoru Sekido, Kazuhiro Takefuji, Masaaki Takahashi, Hiromi Saida, and Rohta Takahashi Copyright © 2016 Makoto Miyoshi et al. All rights reserved. Kilonova/Macronova Emission from Compact Binary Mergers Thu, 14 Jul 2016 07:15:28 +0000 We review current understanding of kilonova/macronova emission from compact binary mergers (mergers of two neutron stars or a neutron star and a black hole). Kilonova/macronova is emission powered by radioactive decays of -process nuclei and it is one of the most promising electromagnetic counterparts of gravitational wave sources. Emission from the dynamical ejecta of ~0.01 is likely to have a luminosity of ~1040–1041 erg s−1 with a characteristic timescale of about 1 week. The spectral peak is located in red optical or near-infrared wavelengths. A subsequent accretion disk wind may provide an additional luminosity or an earlier/bluer emission if it is not absorbed by the precedent dynamical ejecta. The detection of near-infrared excess in short GRB 130603B and possible optical excess in GRB 060614 supports the concept of the kilonova/macronova scenario. At 200 Mpc distance, a typical peak brightness of kilonova/macronova with ejecta is about 22 mag and the emission rapidly fades to >24 mag within ~10 days. Kilonova/macronova candidates can be distinguished from supernovae by (1) the faster time evolution, (2) fainter absolute magnitudes, and (3) redder colors. Since the high expansion velocity () is a robust outcome of compact binary mergers, the detection of smooth spectra will be the smoking gun to conclusively identify the gravitational wave source. Masaomi Tanaka Copyright © 2016 Masaomi Tanaka. All rights reserved. The Photometric Investigation of V921 Her Using the Lunar-Based Ultraviolet Telescope of Chang’e-3 Mission Wed, 15 Jun 2016 09:26:11 +0000 The light curve of V921 Her in ultraviolet band observed by the Lunar-based Ultraviolet Telescope (LUT) is analyzed by the Wilson-Devinney code. Our solutions conclude that V921 Her is an early type marginal contact binary system with an additional close-in component. The binary system is under poor thermal contact with a temperature difference of nearly 700 K between the two components. The close-in component contributes about 19% of the total luminosity in the triple system. Combining the radial velocity study together with our photometric solutions, the mass of the primary star and secondary one is calculated to be , . The evolutionary scenario of V921 Her is discussed. All times of light minimum of V921 Her available in the bibliography are taken into account and the curve is analyzed for the first time. The most probable fitting results are discussed in the paper, which also confirm the existence of a third component ( year) around the binary system. The period of V921 Her is also undergoing a continuously rapid increase at a rate of , which may be due to mass transfer from the less massive component to the more massive one. Xiao Zhou, Sheng-Bang Qian, Jia Zhang, Lin-Jia Li, and Qi-Shan Wang Copyright © 2016 Xiao Zhou et al. All rights reserved. A Time-Dependent and Cosmological Model Consistent with Cosmological Constraints Wed, 08 Jun 2016 09:19:53 +0000 The prevailing constant cosmological model agrees with observational evidence including the observed red shift, Big Bang Nucleosynthesis (BBN), and the current rate of acceleration. It assumes that matter contributes 27% to the current density of the universe, with the rest (73%) coming from dark energy represented by the Einstein cosmological parameter in the governing Friedmann-Robertson-Walker equations, derived from Einstein’s equations of general relativity. However, the principal problem is the extremely small value of the cosmological parameter (~10−52 m2). Moreover, the dark energy density represented by is presumed to have remained unchanged as the universe expanded by 26 orders of magnitude. Attempts to overcome this deficiency often invoke a variable model. Cosmic constraints from action principles require that either both and remain time-invariant or both vary in time. Here, we propose a variable cosmological model consistent with the latest red shift data, the current acceleration rate, and BBN, provided the split between matter and dark energy is 18% and 82%. decreases (, where is the normalized cosmic time) and increases () with cosmic time. The model results depend only on the chosen value of at present and in the far future and not directly on . L. Kantha Copyright © 2016 L. Kantha. All rights reserved. Diverse Features of the Multiwavelength Afterglows of Gamma-Ray Bursts: Natural or Special? Sun, 15 May 2016 08:22:39 +0000 The detection of optical rebrightenings and X-ray plateaus in the afterglows of gamma-ray bursts (GRBs) challenges the generic external shock model. Recently, we have developed a numerical method to calculate the dynamics of the system consisting of a forward shock and a reverse shock. Here, we briefly review the applications of this method in the afterglow theory. By relating these diverse features to the central engines of GRBs, we find that the steep optical rebrightenings would be caused by the fall-back accretion of black holes, while the shallow optical rebrightenings are the consequence of the injection of the electron-positron-pair wind from the central magnetar. These studies provide useful ways to probe the characteristics of GRB central engines. J. J. Geng and Y. F. Huang Copyright © 2016 J. J. Geng and Y. F. Huang. All rights reserved. Adjacent Zero Communication Parallel Cloud Computing Method and Its System for -Body Problem with Short-Range Interaction Domain Decomposition Mon, 21 Mar 2016 10:45:29 +0000 Although parallel computing is used in the existing numerical solutions of -body problem, tons of communications between particles render the parallel efficiency extremely low. Despite the fact that domain decomposition based on short-range interaction is used, when is exceedingly large and lots of communications exist between particles in adjacent areas, the parallel efficiency remains terribly low. This paper puts forward adjacent zero communication parallel cloud computing method for -body problem with short-range interaction domain decomposition. According to this method, the adjacent subblock data are exchanged and redundantly stored without acquiring data from other subblocks in the parallel processing, so the waiting time for data transmission can be saved and hence the parallel processing efficiency can be enhanced substantially. Dingju Zhu Copyright © 2016 Dingju Zhu. All rights reserved. Physical Environment of Accreting Neutron Stars Mon, 21 Mar 2016 09:17:36 +0000 Neutron stars (NSs) powered by accretion, which are known as accretion-powered NSs, always are located in binary systems and manifest themselves as X-ray sources. Physical processes taking place during the accretion of material from their companions form a challenging and appealing topic, because of the strong magnetic field of NSs. In this paper, we review the physical process of accretion onto magnetized NS in X-ray binary systems. We, firstly, give an introduction to accretion-powered NSs and review the accretion mechanism in X-ray binaries. This review is mostly focused on accretion-induced evolution of NSs, which includes scenario of NSs both in high-mass binaries and in low-mass systems. J. Wang Copyright © 2016 J. Wang. All rights reserved. Realization of High Dynamic Range Imaging in the GLORIA Network and Its Effect on Astronomical Measurement Sun, 13 Mar 2016 13:51:32 +0000 Citizen science project GLORIA (GLObal Robotic-telescopes Intelligent Array) is a first free- and open-access network of robotic telescopes in the world. It provides a web-based environment where users can do research in astronomy by observing with robotic telescopes and/or by analyzing data that other users have acquired with GLORIA or from other free-access databases. Network of 17 telescopes allows users to control selected telescopes in real time or schedule any more demanding observation. This paper deals with new opportunity that GLORIA project provides to teachers and students of various levels of education. At the moment, there are prepared educational materials related to events like Sun eclipse (measuring local atmosphere changes), Aurora Borealis (calculation of Northern Lights height), or transit of Venus (measurement of the Earth-Sun distance). Student should be able to learn principles of CCD imaging, spectral analysis, basic calibration like dark frames subtraction, or advanced methods of noise suppression. Every user of the network can design his own experiment. We propose advanced experiment aimed at obtaining astronomical image data with high dynamic range. We also introduce methods of objective image quality evaluation in order to discover how HDR methods are affecting astronomical measurements. Stanislav Vítek and Petr Páta Copyright © 2016 Stanislav Vítek and Petr Páta. All rights reserved. Planar Central Configurations of Symmetric Five-Body Problems with Two Pairs of Equal Masses Tue, 08 Mar 2016 09:38:19 +0000 We study central configuration of a set of symmetric planar five-body problems where the five masses are arranged in such a way that , , and are collinear and , , and are collinear; the two sets of collinear masses form a triangle with at the intersection of the two sets of collinear masses; four of the bodies are on the vertices of an isosceles trapezoid and the fifth body can take various positions on the axis of symmetry both outside and inside the trapezoid. We form expressions for mass ratios and identify regions in the phase space where it is possible to choose positive masses which will make the configuration central. We also show that the triangular configuration is not possible. Muhammad Shoaib, Abdul Rehman Kashif, and Anoop Sivasankaran Copyright © 2016 Muhammad Shoaib et al. All rights reserved. A Hydrodynamical Model of a Rotating Wind Source and Its Effects on the Collapse of a Rotating Core Sun, 27 Dec 2015 11:54:16 +0000 This work presents three-dimensional hydrodynamical simulations with the fully parallel GAGDET2 code, to model a rotating source that emits wind in order to study the subsequent dynamics of the wind in three independent scenarios. In the first scenario we consider several models of the wind source, which is characterized by a rotation velocity and an escape velocity , so that the models have a radially outward wind velocity magnitude given by 1, 2, 4, 6, and 8 times . In the second scenario, we study the interaction of winds emitted from a binary system in two kinds of models: one in which the source remains during the wind emission and a second one in which all the source itself becomes wind. In the third scenario we consider the interaction of a rotating source that emits wind within a collapsing and rotating core. In this scenario we consider only wind models of the second kind built over a new initial radial mesh, such that the angular velocity of the wind is 1, 100, and 1000 times the angular velocity of the core . Guillermo Arreaga-Garcia Copyright © 2015 Guillermo Arreaga-Garcia. All rights reserved. The Impact of KLT Coder on the Image Distortion in Astronomy Tue, 24 Nov 2015 09:27:49 +0000 Presented paper is devoted to the application of Karhunen-Loève transform (KLT) for compression and to study of KLT impact on the image distortion in astronomy. This transform is an optimal fit for images with Gaussian probability density function in order to minimize the root mean square error (RMSE). The main part of the encoder is proposed in relation to statistical image properties. Selected astronomical image processing algorithms are used for the encoder testing. The astrometry and point spread function distortion are selected as the most important criteria. The results are compared with JPEG2000 standard. The KLT encoder provides better results from the RMSE point of view. These results are promising and show the novel approach to the design of lossy image compression algorithms and also suitability for algorithms of image data structuring for retrieving, transfer, and distribution. Petr Pata Copyright © 2015 Petr Pata. All rights reserved. Parameterizing the SFC Baryogenesis Model Tue, 15 Sep 2015 10:40:06 +0000 We have numerically explored the scalar field condensate baryogenesis model for numerous sets of model’s parameters, within their natural range of values. We have investigated the evolution of the baryon charge carrying field, the evolution of the baryon charge contained in the scalar field condensate, and the final value of the generated baryon charge on the model’s parameters: the gauge coupling constant , the Hubble constant at the inflationary stage , the mass , and the self-coupling constants . Daniela Kirilova and Mariana Panayotova Copyright © 2015 Daniela Kirilova and Mariana Panayotova. All rights reserved. Corrigendum to “Regions of Central Configurations in a Symmetric 4 + 1-Body Problem” Sun, 13 Sep 2015 13:52:55 +0000 Muhammad Shoaib Copyright © 2015 Muhammad Shoaib. All rights reserved. The Appearance and Disappearance of Exocomet Gas Absorption Sun, 13 Sep 2015 09:02:13 +0000 CaII K-line (3933 Å) absorption profiles observed towards 15 A-type and two B-type stars with known (or suspected) debris disks, in addition to archival spectral data for three A-type stars, are presented. Inspection of the extracted CaII K-line absorption lines has determined that one late B-type (HD 58647) and four new A-type (HD 56537, HD 64145, HD 108767, and HD 109573) stellar systems exhibit short-term (night-to-night) absorption variation within these profiles. This variability is due to the liberation of gas from falling evaporating bodies (the so-called FEBs activity) on the grazing approach of exocomets towards their parent star. Also we present archival spectra of the FeI λ3860 Å and CaII K-lines towards β Pictoris (HD 39060) that, for the first time, reveal the absorption signatures of FEB activity at similar velocities in both line profiles. FEB-hosting stars seem to be of an earlier type (on average spectral type Al.8 as compared with A3.1) than those where no FEB activity has been observed. This could be due to stellar activity levels (such as chromospheric activity or nonradial pulsations) being of a higher level within the atmospheres of these hotter A-type stars. Barry Y. Welsh and Sharon L. Montgomery Copyright © 2015 Barry Y. Welsh and Sharon L. Montgomery. All rights reserved. Cosmic Rays Report from the Structure of Space Sun, 06 Sep 2015 13:57:49 +0000 Spectrum of cosmic rays follows a broken power law over twelve orders of magnitude. Since ubiquitous power laws are manifestations of the principle of least action, we interpret the spectrum accordingly. Our analysis complies with understanding that low-energy particles originate mostly from rapidly receding sources throughout the cosmos. The flux peaks about proton rest energy whereafter it decreases because fewer and fewer receding sources are energetic enough to provide particles with high enough velocities to compensate for the recessional velocities. Above 1015.6 eV the flux from the expanding Universe diminishes below the flux from the nearby nonexpanding part of the Universe. In this spectral feature, known as the “knee,” we relate to a distance of about 1.3 Mpc where the gravitational potential tallies the energy density of free space. At higher energies particles decelerate in a dissipative manner to attain thermodynamic balance with the vacuum. At about 1017.2 eV a distinct dissipative mechanism opens up for protons to slow down by electron-positron pair production. At about 1019.6 eV a more effective mechanism opens up via pion production. All in all, the universal principle discloses that the broad spectrum of cosmic rays probes the structure of space from cosmic distances down to microscopic details. A. Annila Copyright © 2015 A. Annila. All rights reserved.