bluuebunny/crossref_metadata_2025_split huggingface dataset:
Unveiling the Evolution of Type I AGNs in the IR (15μm) — As Seen by ISO in the ELAIS-S1 Region
Authors: Matute Israel , Franca Fabio La , Gruppioni Carlotta , Pozzi Francesca , Lari Carlo 
Published: July 2016

AbstractWe present the first estimate of the evolution of type 1 AGNs in the IR (15 μm) obtained from the ELAIS survey in the S1 region. We find that the luminosity function (LF) of Type 1 AGNs at 15μm is fairly well represented by a double power-law function with a bright slope of 2.9 and a faint slope of 1.1. There is evidence for significant cosmological evolution according to a pure luminosity evolution model L15(z)α(l+z)k, with in a (Ωm,ΩΛ)=(1.0,0.0) cosmology. This evolution is similar to what is observed at other wavebands. From the luminosity function and its evolution, we estimate a contribution of ~ 2% from Type 1 AGN to the total Cosmic Infrared Background (CIRB) at 15 μm.
The FIRST-APM QSO Survey (FAQS) in the SBS Region. Current Status
Authors: Chavushyan V. , Mújica R. , Valdés J.R. , Carrasco L. , Stepanian J. , Verkhodanov O. 
Published: July 2016

AbstractAs the first step of the Multiwavelength AGN Survey (MWAS), we have started the FIRST-APM QSO Survey (FAQS). The main goal of FAQS is to compile the most complete sample of bright QSOs, located in the area of the sky covered by the Second Byurakan Survey (SBS). Here we report the current status of an ongoing study based on the cross-identification of the FIRST radio catalog and the APM optical catalog. The overlapping sky area between FIRST and SBS is about 700 deg2. The compiled list of sources for this overlapping region contains ~ 400 quasar candidates brighter than . About 90 objects were already spectroscopically classified. During 1999-2000, we observed spectroscopically more than 150 FAQS objects with the 2.1m telescope of the Guillermo Haro Astropysical Observatory (GHAO). We have found 51 new QSOs (4 BAL QSOs), 13 Seyfert Galaxies (5 NLSyl’s), 23 emission line galaxies, 3 BL Lac objects and 57 stars.
Are There AGNs in the Nearby Dwarf Galaxies?
Authors: Karachentsev I. D. , V. E. Karachentseva  
Published: July 2016

AbstractThe presence or absence of a nucleus is considered for a sample of galaxies limited by distance, not by flux. For the 365 nearest galaxies situated within a distance of ~7 Mpc, classification of their central regions is based on large-scale images obtained with the Hubble Space Telescope as well as with the 6-m and other large ground-based telescopes. Occurrence of nucleated galaxies is considered as a function of their luminosity, morphological type and other global properties.
Spectral Variability of Some Seyfert Galaxies
Authors: Denissyuk E.K. , Gaisina V.N. , Valiullin R.R. 
Published: July 2016

AbstractThe very first spectrograms of 40 Seyfert galaxies are discussed. All these objects were taken from Markarian’s lists of galaxies. They were first investigated and classified at Fesenkov Astrophysical Institute during 1973-1988. Spectral study was carried out with a slit spectrograph, attached to the 70-cm telescope and equipped with a three cascades image-tube. Repeated observations of 22 galaxies were obtained in 1985-2000. An analysis of possible spectral variability of the studied galaxies over 10-26 years was made. A list of objects which are the most interesting for further observations is presented.
Analysis of Color Variability of BL Lac during the 1997 and 1999 Outbursts
Authors: Hagen-Thorn V.A. , Larionov V.M. , Hagen-Thorn A.V. , Jorstad S.G. , Temnov G.O. 
Published: July 2016

AbstractThe analysis of multicolor observations of BL Lac obtained in the 1997 and 1999 outbursts shows that in both cases the spectral energy distribution of the variable source was unchanged in the course of outburst. The sources have power-law spectra with slightly different spectral indices (the spectrum was flatter in the more powerful outburst of 1997). The variable source is most probably of synchrotron nature.
Energy Releases from Accreting Superdense Compact Objects in AGNs
Authors: Sadoyan Avetis Abel 
Published: July 2016

AbstractWe consider an accreting central symmetric object that is near to the Eddington limit, i.e., the luminosity pressure is balancing the gravity. In special cases, a layer of accreting matter will be formed near the surface of a centrally symmetric object. We discuss the conditions of formation of the layer, its inner structure and stability. If the luminosity pressure will be reduced for some reason, then the layer will collapse immediately, releasing an enormous quantity (up to 1042 erg/sec) of energy. We discuss some possible scenarios for energy releases.
Planetesimal formation in the solar nebula
Authors: Ruzmaikina T.V. 
Published: July 2016

AbstractTerrestrial planets, cores of giant planets and small bodies of the solar system − comets and asteroids − resulted from the coagulation of interstellar dust grains, and grains which were melted or evaporated and condensed again in the solar nebula.The paper describes the growth and processing of dust grains and their aggregates, starting from molecular cloud cores through the formation and evolution of the solar nebula and the accumulation of these aggregates in larger solid bodies − planetesimals. Discussed are the processes which could be responsible for the interruption of accumulation in the region of the asteroid belt, and processes which shaped the Kuiper belt.
Dynamics of comets in the collapsing protosolar nebula
Authors: Neslušan L. 
Published: July 2016

AbstractComets are created in the cool, dense regions of interstellar clouds. These macroscopic bodies take place in the collapse of protostar cloud as mechanically moving bodies in contrast to the gas and miscroscopic dust holding the laws of hydrodynamics. In the presented contribution, there is given an evidence concerning the Solar system comets: if the velocity distribution of comets before the collapse was similar to that in the Oort cloud at the present, then the comets remained at large cloud-centric distances. Hence, the comets in the solar Oort cloud represent a relict of the nebular stage of the Solar system.
Follow-up astrometry of NEOs at Kleť Observatory – present and future
Authors: Tichá J. , Tichý M. , Moravec Z. 
Published: July 2016

AbstractThe reliable orbit determination of newly discovered NEOs is impossible without precise follow-up astrometry in a sufficient arc of observations. This paper describes the follow-up astrometry NEO programme at the Kleť Observatory. Since 1994 we have used a 0.57-m reflector equipped with CCD camera for confirmations of newly discovered NEO candidates, early follow-up astrometry of NEOs in discovery opposition, recovery of NEOs in second opposition and also follow-up astrometry of poorly observed NEOs in further oppositions. In this field the Kleť Observatory is one of the most productive sites in the world. This programme will be extended to fainter objects with the new 1.02-m reflector − which will become operational at the end of 1998.
V lightcurves and B-V colour of main-belt asteroids
Authors: Blanco C. , Riccioli D. 
Published: July 2016

AbstractTo obtain asteroid photometric lightcurves sufficiently covered to yield the elements necessary to apply the methods for computing their rotational parameters and shape, an observational campaign of main-belt asteroids was undertaken at the Astronomy Institute of Catania University. During more than 40 observational runs, made since 1992 at the M.G. Fracastoro station of Catania Astrophysical Observatory, the lightcurves of more than a hundred asteroids were constructed and the values of rotational axis orientation and of the axes ratio of 50 objects were computed. We present the V lightcurves, the B-V colour, the found values of the synodical rotational period and the lightcurves amplitude of 56Melete,95Arethusa,138Tolosa,198Ampella,212Medea,286Idea,432Pythia\509Iolanda,568Cheruskia,674Rachele,860Ursina,1369Ostaninaand 1469Linzia.The characteristic of the lightcurves and the period values are discussed in comparison with the ones reported in the literature.
Some comments about observations and image processing of comet 29P/Schwassmann-Wachmann 1
Authors: Kubáček D. , Galád A. , Pravda A. 
Published: July 2016

AbstractUnusual short-period comet 29P/Schwassmann-Wachmann 1 inspired many observers to explain its unpredictable outbursts. In this paper large scale structures and features from the inner part of the coma in time periods around outbursts are studied. CCD images were taken at Whipple Observatory, Mt. Hopkins, in 1989 and at Astronomical Observatory, Modra, from 1995 to 1998. Photographic plates of the comet were taken at Harvard College Observatory, Oak Ridge, from 1974 to 1982. The latter were digitized at first to apply the same techniques of image processing for optimizing the visibility of features in the coma during outbursts. Outbursts and coma structures show various shapes.
The long-term evolution of the main asteroidal belt and the origin of large Mars- and Earth-crossers
Authors: Nesvorný D. , Morbidelli A. 
Published: July 2016

AbstractResults of numerical simulations show that the orbits of asteroids in the inner part of the main belt may gradually, subject to a chaotic process acting on 10-100 Myr time scales, become more elliptic and start intersecting the orbit of Mars. The subsequent evolution of an asteroid having close encounters with Mars frequently leads to the Earth-crossing orbit. This revolutionary scenario of the origin of near-Earth asteroids was quantified by Miglioriniet al.(1998) and here we discuss some of the aspects of this work.
Electron Acceleration in Solar Flares
Authors: Dröge Wolfgang , Meyer Peter , Evenson Paul , Moses Dan 
Published: July 2016

AbstractFor the period September 1978 to December 1982 we have identified 55 solar flare particle events for which our instruments on board the ISEE-3 (ICE) spacecraft detected electrons above 10 MeV. Combining our data with those from the ULEWAT spectrometer (MPI Garching and University of Maryland) electron spectra in the range from 0.1 to 100 MeV were obtained. The observed spectral shapes can be divided into two classes. The spectra of the one class can be fit by a single power law in rigidity over the entire observed range. The spectra of the other class deviate from a power law, instead exhibiting a steepening at low rigidities and a flattening at high rigidities. Events with power-law spectra are associated with impulsive (< 1 hr duration) soft X-ray emission, whereas events with hardening spectra are associated with long-duration (> 1 hr) soft X-ray emission. The characteristics of long-duration events are consistent with diffusive shock acceleration taking place high in the corona. Electron spectra of short-duration flares are well reproduced by the distribution functions derived from a model assuming simultaneous second-order Fermi acceleration and Coulomb losses operating in closed flare loops.
The Association of Flares to Cancelling Magnetic Features on the Sun
Authors: Livi Silvia H. B. , Martin Sara , Wang Haimin , Ai Guoxiang 
Published: July 2016

AbstractPrevious work relating flares to evolutionary changes of photospheric solar magnetic fields are reviewed and reinterpreted in the light of recent observations of cancelling magnetic fields. In line-of-sight magnetograms and H-alpha filtergrams from Big Bear Solar Observatory, we confirm the following 3 associations: (a) the occurrence of many flares in the vicinity of emerging magnetic flux regions (Rust, 1974), but only at locations where cancellation has been observed or inferred; (b) the occurrence of flares at sites where the magnetic flux is increasing on one side of a polarity inversion line and concurrently decreasing on the other (Martres et al, 1968; Ribes, 1969); and (c) the occurrence of flares at sites where cancellation is the only observed change in the magnetograms for at least several hours before a flare (Martin, Livi, and Wang, 1985). Because cancellation (or the localized decrease in the line-of-sight component of magnetic flux) is the only common factor in all of these circumstances, suggest that cancellation is the more general association that includes the other associations as special cases. We propose the hypothesis that cancellation is a necessary, evolutionary precondition for flares. We also confirm the observation of Martin, Livi, and Wang (1985) that the initial parts of flares occur in close proximity to cancellation sites but that during later phases, the flare emission can spread to other parts of the magnetic field that are weak, strong, or not cancelling.
Solar and Stellar Magnetic Fields and Atmospheric Structures: Theory
Authors: Parker E. N. 
Published: July 2016

AbstractThis presentation reviews selected ideas on the origin of the magnetic field of the Sun, the dynamical behavior of the azimuthal field in the convective zone, the fibril state of the field at the photosphere, the formation of sunspots, prominences, the spontaneous formation of current sheets in the bipolar field above the surface of the Sun, coronal heating, and flares.
Solar Flares: High-Energy Radiation and Particles
Authors: Rieger Erich 
Published: July 2016

AbstractDue to the Sun's proximity flares can be investigated in the gamma-ray regime and flare generated particles can be measured in space and related to particular events. In this review paper we focus on the problem of particle acceleration by using as observational ingredients: the fluxes and spectra of particles inferred from gamma-ray measurements and observed in interplanetary space, the temporal characteristics of flares at high-energy X- and gamma-rays and the distribution of gamma-ray flares over the solar disc.
Solar Flares: The Gradual Phase
Authors: Švestka Zdeněk 
Published: July 2016

AbstractOne has to distinguish between two kinds of the gradual phase of flares: (1) a gradual phase during which no energy is released so that we see only cooling after the impulsive phase (a confined flare), and (2) a gradual phase during which energy release continues (a dynamic flare).The simplest case of (1) is a single-loop flare which might provide an excellent opportunity for the study of cooling processes in coronal loops. But most confined flares are far more complicated: they may consist of sets of unresolved elementary loops, of conglomerates of loops, or they form arcades the components of which may be excited sequentially. Accelerated particles as well as hot and cold plasma can be ejected from the flare site (coronal ‘tongues', flaring arches, sprays, bright and dark surges) and these éjecta may cool more slowly than the source flare itself.However, the most important flares on the Sun are flares of type (2) in which a magnetic field opening is followed by subsequent reconnection of fieldlines that may continue for many hours after the impulsive phase. Therefore, the main attention in this review is paid to the gradual phase of this category oflong-decay flares. The following items are discussed in particular: The wide energy range of dynamic flares: from eruptions of quiescent filaments to most powerful cosmic-ray flares. Energy release at the reconnection site and modelling of the reconnection process. The ‘post-flare’ loops: evidence for reconnection; observations at different wavelengths; energy deposit in the chromosphere, chromospheric ablation, and velocity fields; loops in emission; shrinking loops; magnetic modelling. The gradual phase in X-rays and on radio waves. Post-flare X-ray arches: observations, interpretation, and modelling; relation to metric radio events and mass ejections, multiple-ribbon flares and anomalous events, hybrid events, possible relations between confined and dynamic flares.
The Automatic Control of Large Optical Telescopes
Authors: Walker G. S. 
Published: July 2016

The aims of the automatic control system are to position the mechanical axis of the telescope to specified right ascension and declination coordinates, and to track the right ascension axis smoothly at sidereal rate, atmospheric refraction variations being taken care of by an auto-guider. The design problems involved fall naturally into two groups, the mechanical ones of measuring the rotations of the axes and of applying drives to these, and the electronic ones of providing supervisory control and calculation facilities.Solutions to these problems depend to a large extent on whether automatic control is being added to an existing telescope with existing drive systems, or a new telescope design is being carried out with automatic control in mind, and on whether an on-line process control computer is to be incorporated or not.
The Edinburgh Automatic Star Follower
Authors: Adam G. R. 
Published: July 2016

The automatic star follower or autoguider described in this paper was designed for the Edinburgh 40/60 cm Schmidt camera. The stellar image in the focal plane of the 15 cm f/18 guide telescope is split optically to produce four stationary images which are sampled by a single image dissector tube, whose sequential output signals are proportional to the intensity of illumination in each quadrant. These signals are compared to produce error signals which are a measure of the radial displacement of the star. Guiding corrections in both right ascension and declination are applied to the fine motions of the Schmidt drive mechanism.Measurements made on a typical plate given an exposure time of 30 min, and using guide stars down to magnitude 8.5 indicate a guiding accuracy of better than 0.14 arcsec or 2 μm at the focus of the guide telescope.
Auromatic Centering on Photographic Star Images
Authors: Høg Erik 
Published: July 2016

AbstractA method for precise centering on photographic star images is proposed. The image is moved only once across one scanning slit for the first coordinate and then across another slit for the orthogonal coordinate.The photometric values are stored and treated in an on-line computer. The relative opto-mechanical simplicity suggests the application of the method to existing comparators.
A New-Star-Counting Device
Authors: Tanabe H. , Mori K. 
Published: July 2016

Measurements of the magnitude distribution and integrated color of stellar fields in many parts of the sky by the star-counting method are important for studies of the structure of the Galaxy and the distribution of interstellar matter. On the other hand, in quantitative studies of the airglow and zodiacal light, we have to know the integrated brightness of the star field in order to subtract the background light from the measured light.Up to the present, these star-counts have been made only for limited areas of the sky, since these measurements were made by using a reading microscope, and they would require much time and labor to extend the measurements to larger sky areas.
Computerized Microphotometry of Stellar Spectrograms
Authors: Latham David W. 
Published: July 2016

Let me begin my description of how we have been doing computerized microphotometry with a brief history of the hardware and its evolution. Then I’ll get on to the more interesting topic of what we do with the data after we get them into the computer.In 1966, the Shock Tube Laboratory at Harvard College Observatory took delivery of a David Mann microphotometer. Briefly, this $50 000 instrument can measure positions in an area 250 x 250 mm to an accuracy of about 1 μn. The limiting resolution of the measuring slit approaches 1 or 2 μm at the plate, and the drift in the photometer output is on the order of 1 per cent in 12 hours.
Microphotometer Digital Data Processing
Authors: Hutchings J. B. 
Published: July 2016

In the past several years many, if not most, observatory microphotometers have been made or adapted to give digital output. At the same time, astronomers have been faced with the task of specifying exactly all the folk lore and experience necessary to reduce microphotometer output, so that the task can be performed by a computer. In addition to the speed and accuracy gains therefore, we have also been obliged to separate the subjective from the objective in this processing, and this may be the most important improvement of all.Knowing that many other observatories have developed similar programming systems, this paper presumably does not contain much that is startlingly new, but it is hoped that it may promote the exchange of ideas desirable to overcome common difficulties and avoid duplication (or multiplication) of effort.
Automatic Computer Reduction of Astronomical Television Images
Authors: Deutschman W. A. 
Published: July 2016

During the 15 months that we operated the Celescope experiment on the Orbiting Astronomical Observatory, we acquired 8700 television frames of star fields containing a total of approximately 10 000 stars.Figure 1 shows an example of one of these frames. Note the target ring, an aluminum deposit on the target of the tube, in each corner of the picture; the shadow in the upper left corner; the calibration lamp just below the center of the picture; and its ghost slightly below and to the left. All other objects are stars. Each frame consists of 256 scan lines designated by the number k, with each line containing 251 pixels (picture elements) designated by the numberl, making a total of 65 000 intensity points I(k,l). The frames are divided into two spectral regions by two filters—lines 1 to 128 have one spectral range, lines 129 to 256 have a different one. Hence, each frame is reduced as two half frames in the first portion of the reduction system.
Polarization of Young Shell Variables
Authors: Breger M. 
Published: July 2016

AbstractStellar polarization between 3000 and 7500 Å has been measured in NGC 2264. Out of 37 stars (including many variables) 4 are definitely polarized, while 3 others show weak polarization. The mean (interstellar) cluster polarization is found to be very small. The highest polarization (4,6 %) is found in a T Tauri star. W 90, a variable below the main sequence, has the highest polarization found among the A and F stars (2, 6%). With the exception of W46, polarization peaks in the blue implying small particle sizes. A good correlation is found between the size of polarization and (other) shell characteristics. These measurements confirm the recently proposed shells in some pre-main sequence stars which appear to be too faint for their color, but fail to detect any new stars with extensive shells. This suggests that some of the scatter in the color-magnitude diagram amongst the A and F stars is real because of an age spread between 1 and 3 X 106 years.
Duplicity and its Consequences among Variable Stars in General
Authors: Larsson-Leander G. 
Published: July 2016

AbstractThe consequences of stellar duplicity for variable stars in general are reviewed. Gravitational effects, radiation effects and effects due to gaseous streams and mass transfer are considered. The possibility of tidal interactions, modulating the pulsations ofβCMa andδSct variables, is among the topics treated in some detail.
On Stothers’ and Simon’s Binary-Star Hypothesis for Beta Canis Majoris Star Pulsation
Authors: Percy John R. , Madore Katherine 
Published: July 2016

The β CMa stars are short-period pulsating variable stars lying slightly above the upper main sequence. Although they have been known and studied for 70 years, little is known about the nature and cause of their pulsation.STOTHERS and SIMON (1969) have recently advanced an hypothesis – hereinafter known as the hypothesis – which proposes that all β CMa stars are the former secondary components of massive binary systems. The former primary components, being more massive, have evolved first, have shed their envelopes by rapid mass loss, and have deposited helium-enriched material from their cores upon the surfaces of the secondary components. This causes the secondary components (now the primary components) to become unstable, via the so-called „μ-mechanism“, to nuclear-energized radial pulsations.