bluuebunny/crossref_metadata_2025_split huggingface dataset:
Evolutionary Characteristics of Large-Scale Magnetic and Velocity Fields
Authors: Ambrož Pavel 
Published: July 2016

AbstractLong-term evolution of solar large-scale magnetic fields in relation to the local active phenomena is studied. The changes of the magnetic flux distribution are influenced by the horizontal transport of magnetized plasma. The whole system of magnetic field changes is interpreted as a global process which is controlled by the large-scale convective patterns. The large-scale horizontal velocity field of transporting motions is determined in various approaches with similar results. Regions with positive divergence in the field of horizontal flow field are found to be closely connected with the occurrence of solar active regions. The process of the horizontal flow was analysed by the “cork” method. The corks reveal a pattern of giant cells which are persistent for several solar rotations. These large cells are interpreted as giant convective elements. Occurrence of new strong magnetic flux in regions of positive divergence is then interpreted as a result of emergence of flux in the upflowing parts of that pattern.
Generation of Plasma Flows and Filamentation of Magnetic Fields in the Solar Atmosphere
Authors: Ryutova Margarita 
Published: July 2016

AbstractNonlinear effects in dynamics of solar magnetic fields which, in particular, determine the evolution of solar magnetic structures and their lifetimes, are discussed. By some analogy with the effects of acoustic streaming in usual hydrodynamics the general definition of these effects as “magneto acoustic streaming” is proposed.
VLBI Observations of Turbulence in the Inner Solar Wind
Authors: Spangler Steven R. 
Published: July 2016

AbstractI discuss the use of Very Long Baseline Interferometer (VLBI) phase scintillations to probe the conditions of plasma turbulence in the solar wind. Specific results from 5.0 and 8.4 GHz observations with the Very Long Baseline Array (VLBA) are shown. There are several advantages of phase scintillation measurements. They are sensitive to fluctuations on scales of hundreds to thousands of kilometers, much larger than those probed by IPS intensity scintillations. In addition, with the frequency versatility of the VLBA one can measure turbulence from the outer corona ~ 5 –10 R⊙ to well past the perihelion approach of the Helios spacecraft. This permits tests of the consistency of radio propagation and direct in-situ measurements of turbulence. Such a comparison is made in the present paper. Special attention is dedicated to measuring the dependence of the normalization coefficient of the density power spectrum, on distance from the sun. Our results are consistent with the contention published several years ago by Aaron Roberts, that there is insufficient turbulence close to the sun to account for the heating and acceleration of the solar wind. In addition, an accurate determination of the relationship could aid the detection of transients in the solar wind.
Eruptive Prominence Associated with Limb Flare of 25 January 1991
Authors: Uddin Wahab , Verma V.K. 
Published: July 2016

AbstractWe have observed an eruptive prominence at the east solar limb on 25 January 1991 which started earlier than 0623 UT and was associated with a limb flare (S16 E90) of class 1B/ X10.0. We have recorded a huge mass ejection in the corona by the limb flare associated eruptive prominence. The eruptive prominence ejected a part of the loop in the corona with maximum speed of about 1280 km/sec. The ejected material attain height upto 150,000 km in the corona and finally faded/disappeared in the corona. During the ascending phase of the prominence material in the corona there was a unscrewing of the loop system associated with the eruptive prominence. The type II, III, and IV radio bursts were also reported by a number of Radio Observatories during observation of the eruptive prominence. The high flux of sudden ionospheric disturbances and the solar radio emissions on fixed frequencies (245-80000 MHz) were also recorded. The eruptive prominence associated with limb flare also shows increased proton flux (>10 MeV) during its occurence. The flare was classified as X10.0 flare. In this paper we have analysed the observed data and compared it with the theoretical model of the solar flare.
An Essay on Terminology, Myths, - and Known Facts: Solar Transient - Flare - CME - Driver Gas - Piston - BDE - Magnetic Cloud - Shock Wave - Geomagnetic Storm
Authors: Schwenn Rainer 
Published: July 2016

AbstractIn the field of solar-terrestrial relations a clear and unique terminology is needed in order to abolish and avoid unnecessary confusion between the scientists from several involved disciplines. For example, the widely used abbreviation CME (for coronal mass ejection) has turned out to be somewhat misleading. Early on it had been known that other than coronal material is often involved in such events. The discoverers observed transient events of mass ejections from the sun, which could be observed in the corona owing to the newly available coronagraphs. This article is meant to clarify the terminology, with emphasis on giving credit to the original discoverers and the terms they introduced. With this aim in mind I suggest some minor modifications of the terminology.
The Hamburg All-Sky Bright QSO Surveys
Authors: Reimers Dieter , Wisotzki Lutz 
Published: July 2016

AbstractOver the past decade, our team has pursued a quest to search for the optically brightest quasars in the entire extragalactic sky, by means of automated quasar selection using digitised objective prism spectra. We give a brief overview over the observational database and selection strategies and present some of the major survey highlights
QSOs from a Variability-and-Proper Motion Survey
Authors: Meusinger Helmut , Brunzendorf Jens , Scholz Ralf-Dieter , Irwin Mike 
Published: July 2016

AbstractWe report on a search for QSOs via variability and zero-proper motion. Candidates were selected by means of indices for overall variability, long-term variability, proper motion and image structure measured on a large number of Schmidt plates with a time-baseline of three decades. Spectroscopic follow-up observations of the candidates brighter than the pre-estimated completeness limit, Blim ≈ 19.7, of the survey revealed about 200 QSOs and Seyfert 1s with redshifts z ≈ 0 — 3. We describe the survey strategy and discuss the properties of the resulting QSO sample.
Infrared Surveys for AGN
Authors: Smith Harding E. 
Published: July 2016

AbstractFrom the earliest extragalactic infrared studies AGN have shown themselves to be strong infrared sources, and IR surveys have revealed new populations of AGN. I briefly review current motivations for AGN surveys in the infrared and results from previous IR surveys. The Luminous Infrared Galaxies, which in some cases house dust-enshrouded AGN, submillimeter surveys, and recent studies of the cosmic x-ray and infrared backgrounds suggest that there is a population of highly-obscured AGN at high redshift. ISO Surveys have begun to resolve the infrared background and may have detected this obscured AGN population. New infrared surveys, particularly the SIRTF Wide-area Infrared Extragalactic Legacy Survey (SWIRE) will detect this population and provide a platform for understanding the evolution of AGN, Starbursts and passively evolving galaxies in the context of large-scale structure and environment.
Results from ISOCAM Deep Surveys: An Answer on the AGN Contribution to the Cosmic Infrared Background
Authors: Aussel Hervé 
Published: July 2016

AbstractThe amount of energy contributed by type-2 AGNs to the Cosmic Infrared Background (CIB) has recently been the subject of some debate, since models have shown it could be responsible for up to half. If this were the case, this contribution should be taken carefully into account before using the combined CIB and COB to derive the density of metals in the universe. I argue here that an observational answer to this problem comes from ISOCAM deep surveys performed at 15 μm, that do resolve into discrete sources the bulk of the CIB at 140 μm. Studies of the X-ray properties of these sources allow us to assess whether or not they are dominated by AGNs, and to derive that the type-2 AGNs contribution to the CIB is not greater than 20%.
The AGN Content of Hard X-ray Surveys
Authors: Comastri Andrea , Vignali Cristian , Brusa Marcella 
Published: July 2016

AbstractMultiwavelength observations of the hard X-ray selected sources discovered by BeppoSAX, Chandra and XMM-Newton surveys have significantly improved our knowledge of the AGN population. The increasing number of X-ray obscured AGN so far discovered confirms the prediction of those AGN synthesis models for the X-ray background based on the Unified scheme. However, follow-up optical observations of hard X-ray selected sources indicate that their optical properties are quite varied and the simple relations between optical and X-ray absorption are by no means without exception. Moreover there is evidence of a substantial number of luminous X-ray sources hosted by apparently normal galaxies. In this paper the results obtained from multiwavelength observations of hard X-ray selected sources discovered by BeppoSAX and XMM-Newton are presented and briefly discussed.
The X-ray Variability of High-Redshift QSOs
Authors: Manners J. , Almaini O. , Lawrence A. 
Published: July 2016

AbstractWe present an analysis of X-ray variability in a sample of 156 radio quiet quasars taken from the ROSAT archive, covering a redshift range 0.1 < z < 4.1. Through combining light curves in ensembles we are able to identify trends in variability amplitude with luminosity and with redshift. The decline in variability amplitude with luminosity identified in local AGN (z < 0.1) is confirmed out to z = 2. There is tentative evidence for an increase in QSO X-ray variability amplitude towards high redshifts (z > 2) in the sense that QSOs of the same X-ray luminosity are more variable at z > 2. The simplest explanation for this effect may be that high-redshift QSOs are accreting at a higher efficiency than local AGN.
AGN Selection by Size of Dominant Emission
Authors: Augusto Pedro , Gonzalez-Serrano J. Ignacio 
Published: July 2016

AbstractThe potential of AGN surveys extends to structure-related objectives: e.g. to study the size and properties of the NLR in AGN. From a complete sample of 1665 radio sources, we selected fifty-five with features on ~0.2-2 kpc scales (core/jet flux ratio <7:1) for further study. Here, we summarize the radio interferometric selection technique used and speculate on the prospects for optical surveys (using a size criterion).
Survey and Analysis of 1-22 GHz Spectra for the Full Sample of 660 AGNs North of Declination −30°
Authors: Kovalev Y. Y. , Nizhelsky N. A. , Kovalev Yu. A. , Zhekanis G. V. , Bogdantsov A. V. 
Published: July 2016

AbstractMeasurements of broad-band 6-frequency 1-22 GHz spectra of 660 compact extragalactic radio sources were performed in 1997 (for declinations −30° < δ < + 43°) and 1998 (north of+49°) at RATAN-600. “Average rest-frame” statistical spectral shapes for different subsamples of sources are analyzed. These shapes and each spectrum observed can be represented as the sum of a spectrum of an extended optically thin component (magnetized envelope/lobe), constant or slowly variable and dominating at lower frequencies, and a spectrum of a compact component (relativistic jet), dominating at higher frequencies, with any type of variability. We have revealed specific radio features of the EGRET sub-sample; this favors the models suggesting a relation between the emission mechanisms in radio and gamma-ray ranges. Sources are sampled for which the most compact VLBI structure is expected.
Rapid Variations in the Seyfert 1 Galaxy Mrk 474
Authors: Valiullin R. R. 
Published: July 2016

AbstractSpectra of Mrk 474 have been obtained in order to search for short-term (less than one day) variability in the broad Hβ and Hα profiles. Observations were carried out using a slit spectrograph and a three-cascade image tube attached to the 70-cm reflector. The processing of the series of spectrograms, obtained on 1999 April 25, showed a rapid (less than 20 minutes) and powerful increase of the flux in the region of [O III]λ5007. The increase of the flux near maximum (5060Å ± 10Å)appeared to be equal approximately to 300%. The value similar to the FWHM for the long-wavelength excess of the flux was equal to 170Å ± 20Å. The dying-out of the long-wavelength excess lasted approximately two hours.
Statistical results on discovered near-Earth asteroids
Authors: Berinde S. 
Published: July 2016

AbstractThe first part of this paper gives a recent overview (until July 1st, 1998) of the Near-Earth Asteroids (NEAs) database stored at Minor Planet Center. Some statistical interpretations point out strong observational biases in the population of discovered NEAs, due to the preferential discoveries, depending on the objects’ distances and sizes. It is known that many newly discovered NEAs have no accurately determinated orbits because of the lack of observations. Consequently, it is hard to speak about future encounters and collisions with the Earth in terms of mutual distances between bodies. Because the dynamical evolution of asteroids’ orbits is less sensitive to the improvement of their orbital elements, we introduced a new subclass of NEAs named Earth-encounter asteroids in order to describe more reliably the potentially dangerous bodies as impactors with the Earth. So, we pay attention at those asteroids having an encounter between their orbits and that of the Earth within 100 years, trying to classify these encounters.
Orbital evolution of comet 73P/Schwassmann--Wachmann 3 and its meteor streams
Authors: Gajdoš Š. , Galád A. , Klačka J. , Pittich E. M. 
Published: July 2016

AbstractThe orbital evolution of the parent body of comet 73P/Schwassmann-Wachmann 3 and its secondary nuclei B and C after its split at the end of 1995 is investigated. 1500 years backward numerical integration of the parent body and 500 years forward numerical integration of all three bodies were done. Possible consequences of the comet splitting on the population of meteoroids in the vicinity of the Earth's orbit, mainly its manifestation as a meteor shower in 2006, are presented.
Collisional reaccumulation of asteroids
Authors: Campo Bagatin A. , Farinella P. 
Published: July 2016

AbstractWe have developed a new version of the code developed by Campo Bagatin (1994a, b) to model the collisional evolution of the asteroid size distribution. The new code distinguishes between “intact”, unfractured asteroids and asteroids converted by energetic collisions into “piles of rubble”. We have run a number of simulations of the collisional evolution process to assess the size range where reaccumulated bodies should be expected to be abundant in the main asteroid belt. We find that this diameter range ranges from about 10 to 100 km, but may extend to smaller or larger bodies depending on the prevailing collisional response parameters.
Analysis of power law assumptions for short-period comets and Kuiper bodies
Authors: Donnison J.R. , Pettit L.I. 
Published: July 2016

AbstractA Pareto distribution was used to model the magnitude data for short-period comets up to 1988. It was found using exponential probability plots that the brightness did not vary with period and that the cut-off point previously adopted can be supported statistically. Examination of the diameters of Trans-Neptunian bodies showed that a power law does not adequately fit the limited data available.
Size, physical properties, and orbital evolution of the comet Hale-Bopp (C/1995 O1) nucleus
Authors: Churyumov K.I. , Kruchynenko V.G. , Makarchuk R.V. 
Published: July 2016

AbstractThe equation of the energy balance for the comet Hale-Bopp nucleus is analyzed for the moment when the comet passed perihelion and the sublimation rate (for water) was 1031molecules s−1≈ 3 × 105kgs−1. The minimal value of the nucleus radiusRequ(for γ = 1.0, i.e. the total surface sublimation) equals 14.6 km; for γ = 0.2 (the comet Halley nucleus had approximately this γ value)Requ= 33 km; the thickness of the mineral crust equals ≈ 10−2m for the heat conductivity coefficient ƛ ≈ 0.2 Jm−1s−1K−1. The results of calculations of the orbital elements evolution of the comet Hale-Bopp during one rotation around the Sun show that the comet will not collide with Jupiter (both passages near Jupiter will take place at distances more than 4 AU).
Electron Beam as Origin of White-Light Solar Flares
Authors: Aboudarham J. , Henoux J. C. 
Published: July 2016

AbstractWe study the effect of chromospheric bombardment by an electron beam during solar flares. Using a semi-empirical flare model, we investigate energy balance at temperature minimum level and in the upper photosphere. We show that non-thermal hydrogen ionization (i.e., due to the electrons of the beam) leads to an increase of chromospheric hydrogen continuum emission, H− population, and absorption of photo-spheric and chromospheric continuum radiation. So, the upper photosphere is radiatively heated by chromospheric continuum radiation produced by the beam. The effect of hydrogen ionization is an enhanced white-light emission both at chromospheric and photospheric level, due to Paschen and H− continua emission, respectively. We then obtain white-light contrasts compatible with observations, obviously showing the link between white-light flares and atmospheric bombardment by electron beams.
Models of Flaring Loops
Authors: Emslie A. Gordon 
Published: July 2016

AbstractWe review the somewhat questionable concept of an isolated flare loop and the various physical mechanisms believed to be responsible, to some degree, for energy transport within the loop structure. Observational evidence suggests a predominant role for high-energy electrons as an energy transport mechanism, and we explore the consequences of such a scenario in some detail, focusing on radiation signatures in the soft X-ray, hard X-ray, and EUV wavebands, as observed by recent satellite observatories. We find that the predictions of flare loop models are in fact in excellent agreement with these observations, reinforcing both the notion of the loop as a fundamental component of solar flares and the belief that electron acceleration is an integral part of the flare energy release process.
Radio Emission From Stellar Flares
Authors: Kuijpers Jan 
Published: July 2016

AbstractAn overview is given of the observations of stellar radio ‘flares', defined as radio emission which is both variable in time and created by explosive releases of magnetic energy. The main sources of such flares are late-type Main-Sequence stars, classic close binaries, X-ray binaries, and pre-Main-Sequence stars.We summarize the interpretations of these observations in terms of the various incoherent and coherent emission mechanisms. The possible importance of a coherent emission process in electrostatic double layers is pointed out.We briefly indicate the diagnostic importance of radio emission for the flare process in classic and compact stars. In particular we discuss the possible production of radio flares from interactions between an accretion disk and the magnetic field of the central object.
Hydrodynamic Models of Solar and Stellar Flares
Authors: Peres Giovanni 
Published: July 2016

AbstractThis paper discusses the hydrodynamic modeling of flaring plasma confined in magnetic loops and its objectives within the broader scope of flare physics. In particular, the Palermo-Harvard model is discussed along with its applications to the detailed fitting of X-ray light curves of solar flares and to the simulation of high-resolution Caxix spectra in the impulsive phase. These two approaches provide complementary constraints on the relevant features of solar flares. The extension to the stellar case, with the fitting of the light curve of an X-ray flare which occurred on Proxima Centauri, demonstrates the feasibility of using this kind of model for stars too. Although the stellar observations do not provide the wealth of details available for the Sun, and, therefore, constrain the model more loosely, there are strong motivations to pursue this line of research: the wider range of physical parameters in stellar flares and the possibility of studying further the solar-stellar connection.
Summary of Automation on the AURA 150-inch Telescope
Authors: Crawford D. L. 
Published: July 2016

We hope to have a well-planned program tied to the astronomical specifications demanded. We also hope to save time and money, very important considerations in high cost, big science.I have become really aware of the sink of dollars and man-hours that technology involves, especially so when it is not well defined and well planned. We hope to avoid a near bottomless sink if we can. Total systems design is very important, not just a careful design of each subsystem.In adopting automation, I want to insist that we don’t lock out certain experimental possibilities that we had before, or lock out certain type people (good ones) who are unwilling or unable to work with the highly sophisticated equipment we’ll be providing. Excellent astronomy has been done with poor equipment used by good astronomers; even the best equipment doesn’t do the best astronomy without the full involvement of good scientists. What I’m saying is, perhaps, that the system has to be our slave, not the reverse, and that we should not be limited by it.What we want is an improvement in astronomical research, not merely in the gadgetry involved. The key to success may well be to strive for the best possible astronomer-technologist interface.
Aspects of an Integrated Telescope Computer System
Authors: Laustsen S. , Malm B. 
Published: July 2016

The art of computing was early recognized by astronomers as being the link between observation and theory. Computing became more and more important with the appearance of electronic computers.Today we can regard the application of electronic computers in three different aspects.1.Theoretical investigations.2.Data handling, that means collecting of astronomical observations and reduction to observational results.3.Control of telescopes and other astronomical instruments.The present paper deals with item No. 3 only. It should, however, be emphasized that the combination of items 2 and 3 will lead to fully automatic astronomical observation in the future.
Some Information on the Catania Flare Star Survey
Authors: Cristaldi S. 
Published: July 2016

I should like to give some information on the activity of the Catania Working Group on Flare Stars constitued by G. Godoli, M. Rodono and myself.The first purpose of our work is to carry out a sufficient large amount of homogeneous photoelectric observations.A first series of data, which refer to 1967 and 1968 observations, has already been published in the Supplement of Astronomy and Astrophysics (2, 223,1970).
Variables in Globular Clusters, the Common and the Rare
Authors: Hogg Helen Sawyer 
Published: July 2016

The title of this talk is really just a different phrasing from one I have used at several IAU meetings on the subject of numbers and kinds of variables in globular clusters. To furnish this material, I have finished the Third Catalogue of Variables in Globular Clusters. Since many of you are coming to this Colloquium with new information, the Catalogue is in draft form with a request that corrections and additions be given me by October 2, after which the draft will go to the printer.The First Catalogue of Variables in Globular Clusters was published at this observatory in 1939 and the Second Catalogue in 1955. In 1966 appeared the excellent Catalogue of Variables South of Declination—29° by Fourcade, Laborde and Albarracin, with splendid large prints of identification charts.