bluuebunny/crossref_metadata_2025_split huggingface dataset:
Weak dynamical effects in the Uranian ring system
Authors: Freedman Adam P. , Tremaine Scott , Elliot James L. 
Published: July 2016

ABSTRACTA number of weak gravitational forces were examined for their kinematic effects on the Uranian ring system, in an attempt to account for residual errors of ~2 km in the ring positions and a few times 10-3deg/day in the apse precession rates. The principal conclusions are as follows: (1) perturbations by the five known satellites are too small to have observable effects with the best current estimates of the satellite masses. (2) Limits can be set on the masses of inter-ring “shepherd” satellites from their influence on precession rates and their radial perturbations on the rings. For example, the maximum mass of a shepherd satellite between rings 4 and 5 is ~ 1019gm. (3) Using the best available ring parameters, there is no convincing evidence that the rings are associated with resonances with known satellites. The only close association is of rings 5, α and γ with three-body resonances due to Miranda and Ariel. It is more likely that the putative shepherd satellites may occupy resonances. (4) The known satellites can cause anomalous residuals by changing the position of Uranus relative to the system barycenter during the occultation. The maximum change, so far, during the 1977 March 10 event, was 1.6 km. This effect will be investigated with the MIT Uranus ring model.
Stochasting modeling of planetary ring systems
Authors: Hart Robert W. 
Published: July 2016

ABSTRACTThis paper models maximum entropy configurations of idealized gravitational ring systems. Such configurations are of interest because systems generally evolve toward an ultimate state of maximum randomness. For simplicity, attention is confined to ultimate states for which interparticle interactions are no longer of first order importance. The planets, in their orbits about the sun, are one example of such a ring system. The extent to which the present approximation yields insight into ring systems such as Saturn's is explored briefly.
Dynamics of neutral small particles
Authors: Mignard F. 
Published: July 2016

ABSTRACTThe dynamics of small grains are reviewed when the radiation pressure forces are added to the gravitational attraction.In the first section we attempt to summarize the studies dealing with the interaction matter - radiation. The problem consists in the computation of the momentum transfer between a grain and the radiation field. The flie's theory of scattering is used for this purpose and the results come out as the value of the ratio of the radiation pressure force to the gravitational force for various material of different sizes.The motion of a grain in an heliocentric orbit is discussed through the second section and includes conditions for a particle to be ejected from the solar system, abrupt change of the orbital elements due to fragmentation along with continuous variation generated by sublimation and sputtering. Likewise the Poynting- Robertson drag is considered and some results are given concerning the lagrangian points L4 and L5 when radiation forces are taken into account.The last section deals with the motion of a grain about a planet. The solution of this problem has recently been updated and the orbital evolution of a grain is presented for a sphericla planet. In order to make the solution relevant for the planetary rings it is adapted to allow for the planet's oblateness.
The formation of spokes in Saturn's rings
Authors: Morfill G.E. 
Published: July 2016

ABSTRACTStarting from the assumption that electromagnetic interactions are in some way related to the formation of spokes, it is shown that energy constraints and spoke observations suggest an evolutionary spoke formation model rather than a sudden imprint of an unspecified phenomenon. It is further shown that relatively small (100's km) plasma clouds, interacting both with the magnetosphere and with small dust particles from the ring, can obtain high radial velocities. The “dynamo” which drives the plasma cloud, is a direct result of the difference in the azimuthal velocity components of the corotating plasma and the Keplerian (charged) dust, with its associated azimuthal current. In its wake, the plasma cloud leaves an almost radial trace of sub-micron sized dust elevated above (or below) the ring plane. Finally, the question of the origin of the plasma clouds is addressed. There could be several processes, e.g. meteorite impacts, electric discharges in the ring, particle acceleration along parallel electric fields etc. Each process has its own characteristic signature, and more work (analysis of measurements and theory) is needed to differentiate between them.
The gravito-electrodynamics of charged dust in planetary ring systems
Authors: Mendis D.A. , Hill J.R. , Northrop T.G. 
Published: July 2016

ABSTRACTSolid bodies within planetary magnetospheres could be charged, under a variety of circumstances, to sizable electrostatic potentials. While this charging has only physical effects on the larger bodies (e.g., electrostatic levitation and blow-off of fine loose dust from their surfaces), it can have both physical (e.g., electrostatic erosion and disruption) and dynamical effects on the smaller (micron and sub-micron sized) dust grains. Here we will confine ourselves to the dynamics of such small grains moving under the combined influence of the planet's gravitational and the electromagnetic forces within the co-rotating regions of planetary magnetospheres, where the observed ring systems are located.
The formation of the terrestrial planets from lunar sized planetesimals
Authors: Aarseth Sverre J. , Lecar Myron 
Published: July 2016

ABSTRACT.We have performed a numerical simulation of the formation of the terrestrial planets from lunar sized planetesimals. The simulation was confined to a plane and included the gravitational forces between planetesimals as well as the Sun. When two planetesimals physically collided, they were merged into one.Initially, two hundred moons were distributed with uniform surface density, from 0.5 to 1.5 AU. The eccentricities were zero at the start: the average eccentricity grew to 0.06 in 10,000 years. After 65,000 years we were left with five bodies, the two largest of which each had 3/4 of an Earth mass. This system is extremely stable to further evolution and an additional mechanism may be required to reduce the number of bodies to one or two.
Asteroid compositional «rings»: clues to the compositions of primordial planetesimals in the middle solar system
Authors: Tedesco E.F. 
Published: July 2016

ABSTRACTIt has recently been established that the distribution of asteroid taxonomic types at distances between 2.1 and 5.3 astronomical units is highly structured. There are four major, overlapping but nevertheless compositionally distinct, “rings” of asteroids present within this range of heliocentric distance. These “rings”, within which ~ 80% of each of four major taxonomic types (S, C, P, and D) fall, are centered at 2.6 (0.7), 2.9 (0.8), 3.4 (0.7), and 4.6 (1.5) AU respectively, where the numbers within parentheses are the ring “widths” in AU. The overall physical resemblence between the asteroid “rings” and planetary rings is poor; physically the asteroid belt more closely resembles a debris strewn satellite system. This structure is consistent with these objects having been formed directly from the solar nebula at, or near, the heliocentric distances at which we find them today. Once the mineralogy of these taxonomic types is firmly established, and complications arising from post-accreationary metamorphism are dealt with, they may be used as probes of physical conditions in the early solar system. In particular, the identification of primordial planetesimals will allow us to obtain a first-hand look at the siblings of the planetesimals responsible for the final stage of planetary accretion.
Radio Supernovae: The Detection of SN 1961V in NGC 1058
Authors: Cowan John J. , Henry Richard B. C. , Branch David 
Published: July 2016

AbstractWe report the radio detection of supernova 1961v in NGC 1058. SN 1961v has a spectral index of -0.4 ± 0.1. At the distance of NGC 1058, the absolute monochromatic luminosity of this source is comparable to that of Cas A. A second nonthermal source with a spectral index of -0.3 ± 0.1 was also detected in NGC 1058 and is likely to be a remnant of a supernova that was not optically detected. The two radio sources, and two optically faint H II regions that coincide with the radio sources, are separated by only 3.5".
Instabilities Driven in Young Supernova Remnants by Electron Heat Conduction
Authors: Bedogni R. , D’Ercole A. 
Published: July 2016

Adiabatic models of supernova remnants (SNRs) show very large temperature gradients. The effect of thermal conduction on the Sedov solution was studied by a number of authors (Solinger et al., 1979; Cox and Edgar, 1983; Cowie, 1977).The observations show, however, that young SNRs such as SN 1006 (Hesser and van den Bergh, 1981) and SN 1572 (Strom, Goss and Shaver, 1982) are in an intermediate state between free expansion and the Sedov phase. In these cases stellar matter cannot be neglected. Following Chevalier (1982), the freely expanding ejecta of a Type I SNR can be modeled in such a way that the inner 4/7 of the mass have constant density and the outer 3/7 have a ρ∝r−7 profile (the "ramp"). The interaction of the ejecta with the uniform circumstellar medium (CSM) gives rise to a pair of shocks. As long as the reverse shock is within the r−7 part of the density profile, the interaction region is described by a self-similar solution (Chevalier, 1982). Such a solution holds for an adiabatic single fluid; the temperature gradient, however, is so large that it may give rise to a quite high heat flux.
Adiabatic Supernova Expansion into the Circumstellar Medium
Authors: Band David L. , Liang Edison P. 
Published: July 2016

AbstractWe perform one dimensional numerical simulations with a Lagrangian hydrodynamics code of the adiabatic expansion of a supernova into the surrounding medium. The early expansion follows Chevalier’s analytic selfsimilar solution until the reverse shock reaches the ejecta core. We follow the expansion as it evolves towards the adiabatic blast wave phase. Some memory of the earlier phases of expansion is retained in the interior even when the outer regions expand as a blast wave. We find the results are sensitive to the initial configuration of the ejecta and to the placement of gridpoints.
[Ni II] Emission in Supernova Remnants
Authors: Henry Richard B.C. , Fesen Robert A. 
Published: July 2016

AbstractCombining new spectrophotometric data on the Orion and Crab Nebulae with detailed calculations, we show that strong [Ni II] λ7378 emission observed in numerous SNR’s may be associated with gas having Ne > 50,000 cm−3.
The Interaction of the Supernova Remnant VRO 42.05.01 with its HI Environment
Authors: Landecker T.L. , Pineault S. , Routledge D. , Vaneldik J.F. 
Published: July 2016

AbstractVRO 42.05.01 (G166.0+4.3) is a SNR which has broken into and re-energized an old interstellar cavity. Observations of HI in a field containing the SNR show features associated with it. An expanding shell of mass ∼40 M⊙ is associated with the semi-circular shell of the SNR. The cavity, which the SNR has re-energized, is seen in the HI. A cloud of HI of mass ∼25 M⊙ has apparently been hit by the shock and has been accelerated by the post-shock flow.
Two Remarkably Thin CO Filaments Toward the Supernova Remnant G109.1-1.0
Authors: Tatematsu K. , Fukui Y. , Iwata T. , Nakano M. 
Published: July 2016

AbstractWe observed the semicircular supernova remnant G109.1-1.0 in the J = 1-0 transition of CO with the Nobeyama 45-m radio telescope. It is found that two remarkably thin molecular filaments delineate the inner boundary of the X-ray jet feature in this remnant. These filaments seem to have experienced evaporation due to the hot gas in the remnant.
SNR Polarization and the Direction of the Magnetic Field
Authors: Milne D.K. 
Published: July 2016

AbstractAt the CSIRO Division of Radiophysics we are currently engaged in a program to map polarization in SNRs at 8.4 GHz. These results are compared with earlier Parkes 5 GHz maps to deduce the direction of magnetic field, Faraday rotation and depolarization.
Infrared Spectroscopy and Mapping of IC443
Authors: Wright Gillian S. , Graham James R. , Longmore Andrew J. 
Published: July 2016

AbstractWe present infrared (IR) spectroscopy and imaging of the supernova remnant IC443. [FeII] 1.644µm, Brackett γ and H2 1-0 S(l) were detected. The most striking feature of the spectra is the high [FeII] 1.644µm/Brackett γ ratio, which is typically ~30. We argue that this ratio is due to shock excitation. Two 5’×3’ maps of the remnant in the 1.644µm [FeII] line are used to study the line excitation. The IR [FeII] line is a sensitive probe for regions of shocked gas which is especially useful where the extinction is high, or the shocks are too slow to excite optical lines.
Luminosity of Evolving Supernova Remnants
Authors: Cioffi D.F. , McKee C.F. 
Published: July 2016

AbstractWe present an analytic kinematic model for the evolution of a supernova remnant beginning with the Sedov-Taylor adiabatic stage and continuing through the radiative stage. Using this model, we obtain the luminosity of the radiative shock and the hot interior.
High-Resolution Radial Velocity Mapping of Optical Filaments in Evolved Supernova Remnants
Authors: Greidanus H. , Strom R.G. 
Published: July 2016

AbstractWe report on observations of the kinematical structure of optical filaments in evolved supernova remnants, using an imaging Fabry-Perot interferometer. The radial velocity characteristics as seen in [OIII] λ5007 emission in one area in the Cygnus Loop are described, where four kinematically different components contributing to the emission can be recognized.
Supershells with Induced Large-Scale Supernovae Formation
Authors: Kolesnik I.G. , Silich S.A. 
Published: July 2016

AbstractWe propose a model of expanding supershells regulated by star formation which is induced in HI superclouds by similar shells from a previous evolutionary stage. Compression of pre-existing cloudlets by such shells triggers the formation of massive stars which then
explode at the end of their evolution as supernovae. Efficiency of induced supernovae formation must be less than 1% to fit the observational properties of supershells.
A Statistical Study of the Correlation of Galactic Supernova Remnants and Spiral Arms
Authors: Li Zongwei , Wheeler J. Craig , Bash Frank N. , Jefferys William H. 
Published: July 2016

AbstractA statistical study of the correlation of Galactic supernova remnants with spiral arms and the disk is presented. SNR apparently have a larger radial scale length than disk stars. We estimate that only about 10 percent of the Galactic SNR have been detected.
Star Formation, Supernovae and the Structure of Disk Galaxies
Authors: Dopita Michael A. , Stromlo Mt. 
Published: July 2016

AbstractA physical model for bi-modal star formation and the structure of the interstellar medium and the self-regulating evolution of disk galaxies is presented. Stars heavier than about one solar mass are produced as a result of collisions of molecular clouds or in cloud crushing events whereas low-mass stars are produced at a steady rate in dense molecular clouds and the T-Tauri winds resulting maintain the support of these clouds against rapid collapse and fragmentation. Supernova explosions and stellar winds associated with the massive stars maintain the phase structure, and the scale height of the gas. The collective effects of these energetic processes may create a hole in the disk gas, and allow a galactic wind of metalenriched gas to develop.
Properties Of Cool Stellar Components in S-Type Symbiotic Stars
Authors: Taranova O.G. , Yudin B.P. 
Published: July 2016

In 1975 Webster and Allen (1975) divided all symbiotic stars into two groups-those in which the 1-4μm continuum show only the presence of a cool star (type S),and those in which dust emission dominates (type D). With the exception of some of yellow symbiotic stars, the dust presence in others correlates with the spectral type of their cool components. That is why one can say that S-type symbiotics contain red giants with spectral type earlier than M6-M7.At the IAU Colloq. N 7Q Allen (1982) noted that it is difficult to escape the conclusion that symbiotic stars contain normal cool giants. Nowadays it is certaiu to be correct because the modern observations of S-type symbiotic stars have not yet discovered any specific distinctions between their cool stellar components and normal red giants. At the same time it should be noted that some of these, for example, Z And, CI Cyg may be interacting binaries in which the cool component apparently fields its Roche lobe and unstable accretion of gas from the red giant onto its hot companion leads to the out bursts of the latter (Kenyon and Webbink 1984; Yudin 1987).
Slow and Rapid Changes of the Radial Velocities in the Symbiotic Binary CH Cygni
Authors: Skopal A. 
Published: July 2016

In the period 1982–1986, new 98 radial velocities (RVs) were determined (at the figures denoted by □). All spectrograms were obtained at the Toruń Observatory. RVs were measured at the Skalnaté Pleso Observatory. The main results are summarized in the figures 1-3. The phase is determined from the middle position of the hot component eclipse (JD 2 446 272) and from the minima difference observed in U light curve (5700d) (Mikolajewski et al., 1987).Slow changes of the RVs of the absorption components of ionized metals reflect the orbital motion of the hot component only between the phases 0.7 and 0.0. The rapid changes are observed mainly between the phases 0.8 and 0.9. They are created by combination of the emission red wing with the absorption component (Skopal et al., 1987). RVs of the cool component are in antiphase (Tomov and Luud, 1984).
Continued Radio Activity from CH Cygni
Authors: Taylor A.R. , Seaquist E.R. , Kenyon S.J. 
Published: July 2016

AbstractFollowing the discovery of the radio outburst and jet formation from CH Cygni in 1984, continued radio monitoring has been carried out with the Very Large Array. We present the preliminary results of these observations, including a high resolution image of the jet in 1986 – 1.5 years after the initial outburst. The star has remained active in the radio, undergoing at least one additional outburst. The radio jet has continued to expand and shows evidence of multiple episodes of ejection along the same axis.
A Review of the R Aquarii System
Authors: Michalitsianos A.G. , Kafatos M. 
Published: July 2016

AbstractThe spatially resolved nebula that characterizes the D–type symbiotic R Aquarii has afforded investigators a unique opportunity to probe the extended emission line regions. Its extensive and complex radio morphology, that includes SiO emission from the only symbiotic associated with maser emission, has provided important clues concerning the mass expulsion process in interacting binary radio stars. Infrared, radio, optical, UV and X-ray observations of the system are discussed in context with models which have been proposed to explain the appearance of the brilliant jet.
The Ultraviolet Spectrum of RX Puppis
Authors: Kafatos M. , Michalitsianos A.G. 
Published: July 2016

AbstractThe UV spectrum of the peculiar star RX Puppis has afforded symbiotic star investigators a wealth of information for unraveling its mysteries. RX Pup and R Aqr, both being of the D-type variety, are now better understood as result of an extended coverage of observations at different wavelengths including radio observations using the VLA. These stars present challenges to our understanding of the symbiotic phenomenon and clues to other astrophysical phenomena like jets. Resolution of the question whether RX Pup has a jet system and an associated system of rings/extended disk or, alternatively, a colliding winds region will be resolved by high resolution radio observations or future observations using the Hubble Space Telescope.
Changing Emphases in Spectral Classification
Authors: Keenan P. C. 
Published: July 2016

The definitions and general principles of the MK system given in the statement by Dr. Morgan, which Dr. McCarthy has read to you, are an expression of my views also.It is mainly in specifying the MK domains that modifications are necessary for the cooler stars - and these for rather obvious reasons. For example, the spectral range has been extended to longer wavelengths, particularly for stars showing strong molecular bands. The lines and bands in the visual and far red regions are particularly useful in defining temperature and chemical composition, but the blue region remains important as having the features most sensitive to luminosity.
Observation of the Spectra of Stars in the Same Photometric Boxes
Authors: Jaschek M. , Jaschek C. , Chmielewski I. 
Published: July 2016

AbstractWe have started at the OHP observatory an observing program for classifying stars in Golay’s boxes of photometrically identical stars. So far 380 stars have been observed at 80 Å/mm dispersion, covering the range from BO to G8. The main result is that stars belonging to the same box are spectroscopically identical at this dispersion if one considers classifications taken from different well experienced observers. This remains true within the current errors of spectral classification. The problem presented by the Ap and Am stars is discussed in detail.
Spectroscopy with New Detectors
Authors: Spinrad H. 
Published: July 2016

AbstractModern digital spectrophotometric devices allow for a much more rapid gathering of spectroscopic data on stars and galaxies. Colors and line strengths can lead to new classification schemes, and/or physical interpretations of much fainter objects than previously possible. However, the same old conceptual problems of interpretation (e.g. in abundances of G and K stars) remain a serious difficulty. Illustrations of these accomplishments and problems are given.
The Effective Temperature Distribution Function of Cataclysmic Variable White Dwarfs
Authors: Sion E.M. 
Published: July 2016

AbstractWith the recent detection of direct white dwarf photospheric radiation from certain cataclysmic variables in quiescent (low accretion) states, important implications and clues about the nature and long-term evolution of cataclysmic variables can emerge from an analysis of their physical properties. Detection of the underlying white dwarfs has led to a preliminary empirical CV white dwarf temperature distribution function and, in a few cases, the first detailed look at a freshly accreted while dwarf photosphere. The effective temperatures of CV white dwarfs plotted versus orbital period for each type of CV appears to reveal a tendency for the cooler white dwarf primaries to reside in the shorter period systems. Possible implications are briefly discussed.
A Photometric and Spectroscopic Comparison of the Cataclysmic Variables on the 2 Sides of the Period Gap and at a Specific Orbital Period
Authors: Szkody P. 
Published: July 2016

AbstractNew and previously existing photometric colors and spectroscopic H and He line strengths are used to compare CV disk systems below the period gap (P=80–130 min) with those directly above (P=190–240 min). Significant differences are found in the mean U-B,V-J colors and in the Hβ equivalent widths on the 2 sides of the gap. A detailed comparison from UV-IR of 3 high inclination novalike systems with periods near 3.3 hr (PG1012−029, PG1030+590 and V1315 Aql) shows similar continuum distributions (and implied mass accretion rates) but large differences in high excitation lines (HeII1640,4686;CIV1550).