bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Fly's Eye Camera System: An instrument design for large étendue time‐domain survey
Authors: Pál A. , Mészáros L. , Csépány G. , Jaskó A. , Schlaffer F. , Vida K. , Mező Gy. , Döbrentei L. , Farkas E. , Kiss Cs. , Oláh K. , Regály Zs. 
Published: October 2014

AbstractIn this paper we briefly summarize the design concepts of the Fly's Eye Camera System, a proposed high resolution allsky monitoring device which intends to perform high cadence time domain astronomy in multiple optical passbands while still accomplish a high étendue. Fundings have already been accepted by the Hungarian Academy of Sciences in order to design and build a Fly's Eye device unit. Beyond the technical details and the actual scientific goals, this paper also discusses the possibilities and yields of a network operation involving ∼10 sites distributed geographically in a nearly homogeneous manner. Currently, we expect to finalize the mount assembly – that performs the sidereal tracking during the exposures – until the end of 2012 and to have a working prototype with a reduced number of individual cameras sometimes in the spring or summer of 2013. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The use of UV‐VIS‐NIR reflectance spectroscopy to identify iron minerals
Authors: Szalai Z. , Kiss K. , Jakab G. , Sipos P. , Belucz B. , Németh T. 
Published: October 2014

AbstractIron minerals – which behave as indicators in earthly and Martian environments – can be identified by UV‐VIS‐NIR reflectance spectroscopy. The aim of this study was to compare the spectra of various soils and sediments all of which contain iron minerals but developed under different environmental conditions. To identify the mineral of the sediments we used the first and second derivatives of the Kubelka‐Munk transformed spectra. According to their iron mineral composition, the analysed samples can be divided into three distinct groups. Goethite refers to the hydromorphic conditions, hematite suffers from the long and intense weathering in leaching environment. In the case of steppe climatic conditions the weathering is so weak that the appearance of pedogenic iron minerals is improbable in these soils. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Turbulent magnetic energy spectrum and the cancellation function of solar photospheric magnetic fields
Authors: Marschalkó G. , Petrovay K. 
Published: October 2014

AbstractA simple analytical relation of form α = 2κ – 1 between the magnetic energy spectral exponent α of the turbulent magnetic field in the solar photosphere and its magnetic flux cancellation exponent κ, valid under certain restrictive assumptions, is tested and extended outside its range of validity in a series of Monte Carlo simulations. In these numerical tests artificial “magnetograms” are constructed in 1D and 2D by superposing a discrete set of Fourier modes of the magnetic field distribution with amplitudes following a power law spectrum and measuring the cancellation function on these simulated magnetograms. Our results confirm the validity of the analytical relation and extend it to the domain α < –1 where κ → 0 as α → –∞. The observationally derived upper limit of 0.38 on κ implies α < –0.24 in the granular size range, apparently at odds with a small scale dynamo driven in the inertial range. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Oscillator models of the solar cycle and the Waldmeier effect
Authors: Nagy M. , Petrovay K. 
Published: October 2014

AbstractWe study the behaviour of the van der Pol oscillator when either its damping parameter μ or its nonlinearity parameter ξ is subject to additive or multiplicative random noise. Assuming various power law exponents for the relation between the oscillating variable and the sunspot number, for each case we map the parameter plane defined by the amplitude and the correlation time of the perturbation and mark the parameter regime where the sunspot number displays solar‐like behaviour. Solar‐like behaviour is defined here as a good correlation between the rise rate and cycle amplitude and the lack of a good correlation between the decay rate and amplitude, together with significant (≳10%) r.m.s. variation in cycle lengths and cycle amplitudes. It is found that perturbing μ alone the perturbed van der Pol oscillator does not show solar‐like behaviour. When the perturbed variable is ξ, solar‐like behaviour is displayed for perturbations with a correlation time of about 3–4 years and significant amplitude. Such studies may provide useful constraints on solar dynamo models and their parameters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
A statistical analysis on the relationship between thunderstorms and the sporadic E Layer over Rome
Authors: Barta V. , Scotto C. , Pietrella M. , Sgrigna V. , Conti L. , Sátori G. 
Published: October 2014

AbstractMeteorological processes (cold fronts, mesoscale convective complexes, thunderstorms) in the troposphere can generate upward propagating waves in the neutral atmosphere affecting the behaviour of the ionosphere. One type of these waves are the internal atmospheric gravity waves (AGWs) which are often generated by thunderstorms. Davis & Johnson (2005) found in low pressure systems that a localized intensification of the sporadic E layer (Es) can be attributed to lightnings. To confirm this result, we have performed two different statistical analysis using the time series of the critical frequency (foEs), the virtual height of the sporadic E layer (h'Es), and meteorological observations (lightnings, Infrared maps) over the ionospheric station of Rome (41.9° N, 12.5° E). In the first statistical analysis, we separated the days of 2009 into two groups: stormy days and fair‐weather days, then we studied the occurrence and the properties of the Es separately for the two different groups. No significant differences have been found. In the second case, a superposed epoch analysis (SEA) was used to study the behaviour of the critical frequency and virtual height 100 hours before and after the lightnings. The SEA shows a statistically significant decrease in the critical frequency after the time of the lightnings, which indicates a sudden decrease in the electron density of the sporadic E layer associated with lightnings. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Empirical formulae of temperature and luminosity as functions of mass for calculating the habitable zone
Authors: Dobos V. , Orgoványi J. , Nagy I. 
Published: October 2014

AbstractThe location of the habitable zone can be calculated from the stellar mass by theoretical expressions. In this work we compare different effective temperature and luminosity relations from which the habitable zone is calculated. It was found that for the effective temperature the theoretical models give acceptable results but for the luminosity the measured values are underestimated. Because of the experienced deviation we propose new empirical equations for F, G, K, M main sequence stars (0.3–1.4 M⊙) hosting known exoplanets. Using these equations the boundaries of the habitable zone fit well to the ones which were calculated from measured stellar parameters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Refined position angle measurements for galaxies of the SDSS Stripe 82 co‐added dataset
Authors: Varga J. , Csabai I. , Dobos L. 
Published: October 2014

AbstractPosition angle measurements of Sloan Digital Sky Survey (SDSS) galaxies, as measured by the surface brightness profile fitting code of the SDSS photometric pipeline (Lupton et al. 2001), are known to be strongly biased, especially in the case of almost face‐on and highly inclined galaxies. To address this issue we developed a reliable algorithm which determines position angles by means of isophote fitting. In this paper we present our algorithm and a catalogue of position angles for 26397 SDSS galaxies taken from the deep co‐added Stripe 82 (equatorial stripe) images. Data are published on‐line at http://www.vo.elte.hu/galmorph. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Constraints on supermassive black hole spins from observations of active galaxy jets
Authors: Kun E. , Wiita P.J. , Gergely L.Á. , Keresztes Z. , Gopal‐Krishna  , Biermann P.L. 
Published: October 2014

AbstractWe discuss the origin of the low‐energy cutoff, or LEC, seen in the radio spectra of many extragalactic jets and relate this to the spin of the supermassive black holes that presumably power them. Pion decay via proton‐proton collisions is a possible mechanism to supply a secondary positron population with a low energy limit. We expect that pion production would occur in advection dominated accretion flows or ADAFs. In radiatively inefficient ADAFs the heat energy of the accreting gas is unable to radiate in less than the accretion time and the particle temperature could be high enough so that thermal protons can yield such pion production. Strong starbursts are another option for the injection of a truncated particle population into the jet. The role of both mechanisms is discussed with respect to the black hole spin estimate. The energy demanded to produce the pion decay process involves a minimum threshold for kinetic energy of the interacting protons. Therefore the mean proton speed in the flow can determine whether a LEC is generated. In ADAFs the random velocity of the protons can exceed the minimum speed limit of pion production around the jet launching region in the innermost part of the flow. Finally we summarize the additional work needed to put the model assumptions on a more rigorous basis. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of non‐linear dynamics using Graphical Processing Units
Authors: Nagy‐Egri M.F. , Rácz I. , Debreczeni G. 
Published: October 2014

AbstractA new Graphical Processing Unit (GPU) accelerated general lattice PDE solver and real‐time visualisation framework, called Gripper, is presented. Besides its scientific goals, the purpose of this project is to provide a publicly available, general purpose GPU enabled framework with visualisation capabilities. One of the application of this newly developed software, is aimed to provide valuable insight into non‐linear evolution of relativistic dynamical systems, such, as for example, neutron stars or black holes. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Weak and strong field approximations and circular orbits of the Kehagias‐Sfetsos space‐time
Authors: Dwornik M. , Horváth Zs. , Gergely L. Á. 
Published: October 2014

AbstractThe Kehagias‐Sfetsos asymptotically flat black hole and naked singularity solutions of the Hořava‐Lifshitz gravity are investigated both in the weak‐field and strong‐field regimes. In the weak‐field limit the gravitational field generated by the Kehagias‐Sfetsos spherically symmetric solution is weaker then in the case of the Schwarzschild black hole of general relativity. In the strong‐field regime naked singularities with ω0 ≪ 1 display an unusual distance dependence: gravity becomes weaker when approaching the singularity. The stability of circular orbits is also analyzed. While in the black hole case the square of the angular momentum should be larger than a certain finite, non‐zero minimal value, in the naked singularity case there are stable circular orbits for any non‐zero value of the angular momentum. In this regime we prove the existence of an infimum of the allowed radii of circular orbits (corresponding to vanishing angular momentum). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Lambda matter in the effective density dependent mean‐field model
Authors: Petrik K. , Gmuca S. 
Published: October 2014

AbstractThe density dependent relativistic hadron field (DDRHF) theory is introduced with various forms of the density dependence of the nuclear interaction to study the A matter in the β ‐equilibrium. Several new parametrizations are extracted from the Dirac‐Brueckner‐Hartree‐Fock (DBHF) calculations. We have compared and analysed high density extrapolations of A matter properties and shown that the choice of the density dependence has important effects on the structure of compact stars. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Evolution of primordial magnetic fields
Authors: Banerjee R. 
Published: October 2014

AbstractHere we briefly summarise the main phases which determine the dynamical evolution of primordial magnetic fields in the early universe. On the one hand, strong fields undergo damping due to excitations of plasma fluctuations, and, on the other hand, weak magnetic fields will be strongly amplified by the small‐scale dynamo in a turbulent environment. We find that, under reasonable assumptions concerning the efficiency of a putative magnetogenesis era during cosmic phase transitions, surprisingly strong magnetic fields 10–13–10–11 G, on comparatively small scales 100 pc–10 kpc may survive to prior to structure formation. Additionally, any weak magnetic field will be exponentially amplified during the collapse of the first minihalos until they reach equipartition with the turbulent kinetic energy. Hence, we argue that it seems possible for cluster magnetic fields to be entirely of primordial origin. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Modelling giant radio halos Doctoral Thesis Award Lecture 2012
Authors: Donnert J.M.F. 
Published: October 2014

AbstractWe review models for giant radio halos in clusters of galaxies, with a focus on numerical and theoretical work. After summarising the most important observations of these objects, we present an introduction to the theoretical aspects of hadronic models. We compare these models with observations using simulations and find severe problems for hadronic models. We give a short introduction to reacceleration models and show results from the first simulation of CRe reacceleration in cluster mergers. We find that in‐line with previous theoretical work, reacceleration models are able to elegantly explain main observables of giant radio halos. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Cosmological simulations of galaxy formation: Successes and challenges in the era of supercomputers
Authors: Scannapieco C. 
Published: October 2014

AbstractI use cosmological hydrodynamical simulations to study the formation and evolution of galaxies similar in mass to the Milky Way. First, I use a set of eight simulations where the haloes have a great variety of merger and formation histories, to investigate how similar or diverse these galaxies are at the present epoch, and how their final properties are related to the particular formation history of the galaxy. I find that rotationally‐supported disks are present in 7 of the 8 galaxies at z ∼ 2–3; however, only half of the galaxies have significant disks at z = 0. Both major mergers and the accretion of gas that is misaligned with the preexisting stellar disk contribute to the transfer of material from the disks to the spheroidal components, lowering the disk‐to‐total ratios during evolution. I also present and discuss recent results of the Aquila Project, which compares the predictions of 13 different numerical codes for the properties of a galaxy in a Λ cold dark matter universe. All simulations use a unique initial condition and are analysed in the exact same way, allowing a fair comparison of results. We find large code‐to‐code variations in stellar masses, star formation rates, galaxy sizes and morphologies. We also find that the way feedback is implemented is the main cause of the differences, although some differences might also result from the use of different numerical technique. Our results show that state‐of‐the‐art simulations cannot yet uniquely predict the properties of the baryonic component of a galaxy, even when the assembly history of its host halo is fully specified. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Large Hadron Collider and Dark Matter
Authors: Covi L. 
Published: October 2014

AbstractWe review shortly the scenarios of Weakly Interactive Massive Particle (WIMP) and Super‐Weakly Interacting Massive Particle (SuperWIMP) Dark Matter candidates and discuss the recent searches for Dark Matter candidates at the Large Hadron Collider (LHC). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Long‐term photometry of three active red giants in close binary systems: V2253 Oph, IT Com and IS Vir
Authors: Oláh K. , Moór A. , Strassmeier K.G. , Borkovits T. , Granzer T. 
Published: October 2014

AbstractWe present and analyze long‐term optical photometric measurements of the three active stars V2253 Oph, IT Com and IS Vir. All three systems are single‐lined spectroscopic binaries with an early K giant as primary component but in different stages of orbital‐rotational synchronization. Our photometry is supplemented by 2MASS and WISE near‐IR and mid‐IR magnitudes and then used to obtain more accurate effective temperatures and extinctions. For V2253 Oph and IT Com, we found their spectral energy distributions consistent with pure photospheric emission. For IS Vir, we detect a marginal mid‐IR excess which hints towards a dust disk. The orbital and rotational planes of IT Com appear tobe coplanar, contrary to previous findings in the literature. We apply a multiple frequency analysis technique to determine photometric periods, and possibly changes of periods, ranging from days to decades. New rotational periods of 21.55±0.03 d, 65.1±0.3 d, and 23.50±0.04 d were determined for V2253 Oph, IT Com, and IS Vir, respectively. Splitting of these periods led to tentative detections of differential surface rotations of δP/P ≈ 0.02 for V2253 Oph and 0.07 for IT Com. Using a time‐frequency technique based on short‐term Fourier transforms we present evidence of cyclic light variations of length ≈ 10 yr for V2253 Oph and 5‐6 yr for IS Vir. A single flip‐flop event has been observed for IT Com of duration 2–3 yr. Its exchange of the dominant active longitude had happened close to a time of periastron passage, suggesting some response of the magnetic activity from the orbital dynamics. The 21.55‐d rotational modulation of V2253 Oph showed phase coherence also with the orbital period, which is 15 times longer than the rotational period, thus also indicating a tidal feedback with the stellar magnetic activity. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Peculiarity of stellar kinematics in the solar vicinity
Authors: Popova M.E. 
Published: October 2014

AbstractThe peculiar velocities of nearby stars are studied. We determine the solar velocity components from the radial velocities and proper motions of stars and open clusters. We show that nearby stars are not very suitable for the determination of the solar motion components because of peculiarities in their velocity distribution. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Recent revolutions and unsolved problems in the galaxy evolution paradigm
Authors: Sil'chenko O.K. 
Published: October 2014

AbstractDue to the fast development of observational techniques, observations of high‐redshift galaxies and detailed studies of nearby galaxies bring surprises every week. Many quite unexpected discoveries have been made over the last years, which have changed our views about galaxy formation and evolution substantially. I review some of the most important and unexpected observational facts, which bring changes even to paradigms. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Stochastization in gravitating systems
Authors: Ovod D.V. , Ossipkov L.P. 
Published: October 2014

AbstractWe discuss the effective stochastization time τe for gravitating systems in terms of the Krylov and GurzadyanSavvidi paradigm. The truncated Holtsmark distribution for a random force proposed by Rastorguev and Sementsov implies τe/τc α N0.20, where τc is the crossing time. We find in the case of the Petrovskaya distribution for a random force τe/τc α Nk, where k = 0.27–0.31, depending on the oblateness and rotation of the system, and τe/τc α N1/3/(ln N)1/2 when N » 1. The latter result agrees with those of Genkin (1969) and Gurzadyan & Kocharyan (2009) (k = 1/3). (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Four states of the recurrent symbiotic nova V407 Cyg
Authors: Esipov V.F. , Kolotilov E.A. , Komissarova G.V. , Shenavrin V.I. , Shugarov S.Yu. , Tarasova T.N. , Tatarnikov A.M. , Tatarnikova A.A. 
Published: October 2014

AbstractWe analyze the results of our spectroscopic and photometric monitoring of V407 Cyg in 1984–2009. We show that the hot component of V407 Cyg can be in four different states: a passive state (the system looks as an ordinary, non‐symbiotic Mira), a quiescent state (the system looks as a low‐excitation classical symbiotic star), a Z And‐type outburst, and an RS Oph‐type outburst. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Virtual Observatory for stellar astronomy
Authors: Malkov O. , Zolotukhin I. 
Published: October 2014

AbstractThe principal idea of the Virtual Observatory is to achieve real transparency for astronomical data, similar to transparency for all the world's documents in the World Wide Web. In the Virtual Observatory, all the world's astronomical data is available from one's desktop. All archives understand the same query language, can be accessed through a uniform interface, and diverse data can be analyzed with the same tools. In particular, facilities of the Virtual Observatory allow users to make a fast and correct analysis of objects from various surveys. It yields multi‐photometry data on registered objects and makes it possible to determine stellar parameters. Methods of astronomical data analysis as well as their application to various areas of stellar astronomy are discussed in this paper. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Discovery and investigation of open star clusters in the Milky Way
Authors: Glushkova E.V. 
Published: October 2014

AbstractDuring the recent decade, many investigators searched for new clusters using data from large surveys. In this paper, we review the results of these studies and discuss the methods used to derive physical parameters of open clusters. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
New programs for determining the main parameters of open clusters
Authors: Popova M.E. 
Published: October 2014

AbstractA set of computer programs for the determination of the main parameters of open clusters, such as color excess, distance, and age, is developed. The set consists of two units. The first unit is designed to search for open clusters in wide fields using JHKs‐photometry from various catalogs (2MASS, UKIDSS, VISTA) by identifying areas of high stellar density. The second unit determines the parameters of open clusters by fitting photometric diagrams. This is the unit described in the paper. Probable cluster members are identified by the proximity to the basic sequences on the J–(J — H) and Q–(J — H) diagrams. The color excess is determined by minimizing the deviations of Q values on the Q–(J — H) diagram. Ages and distance moduli are determined by comparing the color‐magnitude diagrams with theoretical isochrones. (© 2013 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)