bluuebunny/crossref_metadata_2025 huggingface dataset:
Consistency of Nutation Modeling in Radio Source Position Comparisons
Authors: Sovers O.J.
Published: July 2016

Comparisons between sets of radio source coordinates determined from independent VLBI measurements show that rotational offsets can be as large as several milliarcseconds (mas), and are considerably larger than the positional uncertainties (≤1 mas). The 1 to 2 mas discrepancies remaining after removal of the rotational offsets indicate the present true level of accuracy. Analyses of DSN and CDP astrometric data are performed to explore the effects of alternative schemes of nutation modeling on such catalog comparisons. It is concluded that rotations between different source catalogs are minimized or eliminated if the nutation models employed are consistent. Intrinsic source coordinate discrepancies, however, remain at the 1 mas level.
β Persei, a Fundamental Star among the Radiostars
Authors: Debarbat Suzanne
Published: July 2016

Optical fluctuations of the radiostar β Persei are seen from 13 campaigns performed with the astrolabe located at the Paris Observatory.
Comment on the Definition of the Nonrotating Origin
Authors: Eichhorn Heinrich
Published: July 2016

The paper gives a rigorous and purely formal derivation for the relationship between the “nonrotating” origin and the x-axis of the Qt system, i.e., the true equator system. Neglecting nutation, a nonrotatingorigin could also be achieved by putting m=0 in the formula for the time derivative of right ascension.
On the Determination of an Astrometric Center of a Quasar
Authors: Galas Roman
Published: July 2016

The influence of optical structure of compact extragalactic radio sources on the definition of their centroids is discussed. Numerical calculations are performed using 4C 31.63 as an example. The results show that the presence of the underlying luminous galaxy does not lead to an unusual decrease of the accuracy in the optical astrometric measurements.
Ecliptical Coordinate System as the Basis of Regatta–Astro Space Astrometry Program
Authors: Guseva Irina S. , Kogan Alexandr Ju. , Heifets Vladimir N.
Published: July 2016

One of the most important problems of modern astrometry is constructing of an ideal inertial coordinate system. A bulk of up–to–date star catalogues is referenced to an equatorial frame, which is far from being really inertial, Some attempts were made to remove this defect by excluding both nutation and precession in right ascention [Guinet 1979, Murray, 1990]. This proposal seams to be a compromise between the existing tradition and the new requirements met by the modern astrometry.
Close Approach Astrometry: A Method for Improving Reference Systems
Authors: Nakamura T. , Shibasaki H.
Published: July 2016

For improved establishment of the dynamical reference frame and tying it to the stellar reference frame, a method to observe close approach (CA) events between satellite and satellite and/or satellite and star is proposed here. The accuracy of measurements of angular distance is 0”.02 – 0”.03 for a single data point. We apply this technique fairly successfully to the CA events of the Galilean satellites and a preliminary orbital longitude correction to the E2X3 constants of J4 is obtained from eight CA observations ranging from 1987 to 1989.
Systematic Corrections to the Fundamental Catalogue due to the Precession Error and the Equinox Correction
Authors: Sôma Mitsuru
Published: July 2016

Fundamental catalogues of stars have systematic errors due to the precession error and the equinox correction. The formula for these errors to be applied to the FK4 is presented.
On Precession and Nutation Values
Authors: Vicente R.O.
Published: July 2016

The results of research on the Earth’s theory of rotation are presented, comparing observed and theoretical values specially for the luni-solar precession and nutation. Investigations of geodynamics show the strong dependence of the nutation values on the adopted model for the structure of the Earth, while the values referring to the precession are not affected as much. The new observational techniques are able to determine some of these values with greater precision than the classical optical techniques, but it is essential that the observations should be done in a systematic and regular way for several decades.
Periodic Variation of the North-South Asymmetry of Solar Activity Phenomena
Authors: Verma V. K.
Published: July 2016

We report here a study of various solar activity phenomena occurring in both north and south hemispheres of the Sun during solar cycles 8–23. In the study we have used sunspot data for the period 1832–1976, flare index data for the period 1936–1993, Hα flare data 1993–1998 and solar active prominences data for the period 1957–1998. Earlier Verma reported long-term cyclic period in N-S asymmetry and also that the N-S asymmetry of solar activity phenomena during solar cycles 21, 22, 23 and 24 will be south dominated and the N-S asymmetry will shift to north hemisphere in solar cycle 25. The present study shows that the N-S asymmetry during solar cycles 22 and 23 are southern dominated as suggested by Verma.
Long-term Cyclic Variations of Prominences, Green and Red Coronae over Solar Cycles
Authors: Rušin Vojtech , Minarovjech Milan , Rybanský Milan
Published: July 2016

Long-term cyclic variations in the distribution of prominences and intensities of green (530.3 nm) and red (637.4 nm) coronal emission lines over solar cycles 18–23 are presented. Polar prominence branches will reach the poles at different epochs in cycle 23: the north branch at the beginning in 2002 and the south branch a year later (2003), respectively. The local maxima of intensities in the green line show both poleward- and equatorward-migrating branches. The poleward branches will reach the poles around cycle maxima like prominences, while the equatorward branches show a duration of 18 years and will end in cycle minima (2007). The red corona shows mostly equatorward branches. The possibility that these branches begin to develop at high latitudes in the preceding cycles cannot be excluded.
Helioseismology and the Solar Interior Dynamics
Authors: Vauclair S.
Published: July 2016

The inversion of helioseismic modes leads to the sound velocity inside the Sun with a precision of about 0.1 per cent. Comparisons of solar models with the “seismic sun” represent powerful tools to test the physics: depth of the convection zone, equation of state, opacities, element diffusion processes and mixing inside the radiative zone. We now have evidence that microscopic diffusion (element segregation) does occur below the convection zone, leading to a mild helium depletion in the solar outer layers. Meanwhile this process must be slowed down by some macroscopic effect, presumably rotation-induced mixing. The same mixing is also responsible for the observed lithium depletion. On the other hand, the observations of beryllium and helium 3 impose specific constraints on the depth of this mildly mixed zone. Helioseismology also gives information on the internal solar rotation: while differential rotation exists in the convection zone, solid rotation prevails in the radiative zone, and the transition layer (the so-called “tachocline”) is very small. These effects are discussed, together with the astrophysical constraints on the solar neutrino fluxes.
Tomography of the Solar Wind using Interplanetary Scintillation
Authors: Oberoi Divya , Rao A. Pramesh
Published: July 2016

Extended Abstract

Interplanetary scintillation (IPS) measurements are sensitive to a weighted sum of the properties of solar wind (SW) along the line-of-sight (los) to a distant compact radio source. Mapping alosback to the surface of the Sun provides information of the sites of origin of the SW sampled by thelos. By observing different sources, lines-of-sight can be so chosen that they sample overlapping regions of Solar surface. In addition, the rotation of the Sun causes the long lived features in the SW to co-rotate, much like the twirling skirt of a ballerina, presenting different perspective views to the Earth based observers. These properties raise the possibility that systematic IPS observations can be inverted to give the maps of density and the velocity of the SW in the inner heliosphere, using techniques similar to tomography.
Filament in EUV Lines; Temperature Gradient Measurements
Authors: Mouradian Z. , Martres M.J. , Soru-Escaut I.
Published: July 2016

On the EUV spectroheliograms obtained with ATM-Skylab, we studied the temperature gradient of the transition region between a filament and the surrounding corona. For this purpose we established contrast curves defined as the ratio between the intensity of the observed point and the adjacent quiet sun. The filament was scanned in three different positions noted B, R, D. The position of the maximum of the contrast of different lines – C II, C III, O IV, O VI, Mg X – formed in the transition zone (104< T < 106) allows us to deduce the horizontal temperature gradient. The following table gives the results of the gradient measurements in K/km.
On the Need for a Routine Coronagraphic Active – Prominence Patrol
Authors: Rompolt B.
Published: July 2016

At the meeting of Working Group 2.4 (Physics of Solar Activity Phenomena) of the Commission of the Academies of Sciences on Planetary Geophysics (KAPG) in Prague in August 1975, I was asked to prepare a program of observations for coronagraphs of small size. The suggested program motivated the importance of observations of the active prominence and proposed to undertake such observations. The program was presented to Working Group 2.4 at the meeting held in Irkutsk in June 1976. According to the recommendation of the Working Group the coronagraphic patrol observations of active prominences has been organized.
Coronal Manifestations of Eruptive Prominences - Theory
Authors: Pneuman G.W.
Published: July 2016

Of all observable solar phenomena, the eruption of prominences is perhaps the most spectacular. These interesting structures may remain quiescent for months and then, for some unknown reason, suddenly rise and leave the Sun at considerable speeds. The physical structure of quiescent prominences is complex. They appear, in Hα, to consist of fine vertical threads of cool dense material suspended at some height above the photosphere surrounded by the hot tenuous corona. They are definitely related to the coronal magnetic field configuration since they are always situated in the vicinity of a neutral line in the line of sight magnetic field.
Chaos and order in the Rotational Motion
Authors: Maciejewski Andrzej J.
Published: July 2016

It was proved that the problem of perturbed planar oscillations of a rigid-body in a circular orbit is nonitegrable. Two types of perturbations were considered: solar radiations pressure and the third body torques. In the second part of the paper example of chaotic rotations of a symmetric rigid body in a circular orbit was given. It was shown numerically that the phase space is divided into two separate regions of chaotic and ordered motions.
The Stochasticity of Motions in the Triplets of Stars and Galaxies
Authors: Anosova J.P. , Kiseleva L.G. , Chernin A.D. , Ivanov A.V. , Orlov V.V.
Published: July 2016

The dynamical instability of motions is studied numerically for the triplets of stars and galaxies. The models of equal-mass components which are in rest initially, are investigated. The divergence of initially near by trajectories close to exponential one is observed in the configurational as well as the phase space. The characteristic time of such divergenee is less for the configurations which are initially hierarchical. The presence of significant dark matter distributed over the whole volume of system speeds up the rate of stochastisation considerably.
On Dynamical Non-Stationarity of the Galaxy Systems
Authors: Anosova J.P. , Kiseleva L.G. , Orlov V.V.
Published: July 2016

By the computer simulations we have studied a behaviour of the virial coefficient k(t) for the triples and quintets of galaxies as a function of time. In a number of cases some quasiperiodical oscillations k(t) have been observed; these variations are resulted from an existence of the temporary binary subsystems. Strong negative correlation between k and rmin (rmin is a minimum separation between the bodies) is observed. A presence of a large hidden mass Mn distributed around a triple increases the degree of stochasticity of the process k(t) and decreases the correlation between k and rmin. The process k(t) must not been considered as a random one, as the autocorrelation function does not show any decreasing of the oscillation amplitude with a grow of time.
Formation of Large Sacle Structures in the Universe by Inverse Cascade: Cosmosynergetics
Authors: Krishan V. , Sivaram C.
Published: July 2016

It is suggested that inverse cascade that may occur in the turbulent cosmic medium can result in the formation of very large scale structures in the universe, upto the largest scales like the Great Wall. Again clustering of galaxies on all scales is interpreted to be due to these self-organisation processes occurring in a turbulent medium, the largest structures being anisotropic and nearly two dimensional, the smaller structures remaining isotropic. The observed fractal distribution of galaxies is also interpreted on this basis. The direct proportionality between the flow velocity and the linear dimension of the structure may show a way out of the dilemma of missing matter.
A Balloon-Borne Detector for Stratospheric Cosmic Dust Detection
Authors: Gucun Wan , Ziyuan Ouyang , Yiwen Xu , Xiguang Wu
Published: July 2016

This paper introduces a kind of cosmic dust collecting technique and describes in detail the structure of the collector, the balloon-basket system and concerning experimental skill.
Dynamic Modelling Transformations for the Low Earth Orbit Satellite Particulate Environment
Authors: McDonnell J.A.M. , Sullivan K. , Green S.F. , Stevenson T.J. , Niblett D.H.
Published: July 2016

A simple dynamic model to investigate the relative fluxes and particle velocities on a spacecraft’s different faces is presented. The results for LDEF are consistent with a predominantly interplanetary origin for the larger particulates, but a sizable population of orbital particles with sizes capable of penetrating foils of thickness <30μm. Data from experiments over the last 30 years do not show the rise in flux expected if these were space debris. The possibility of a population of natural orbital particulates awaits confirmation from chemical residue analysis.
Face-Dependent Impact Probabilities Upon LDEF for Heliocentric Particle Orbits
Authors: Steel Duncan
Published: July 2016

If the impact record upon LDEF is to be interpreted so as to determine the flux, orbits, sizes and compositions of natural meteoroids and dust, and space debris, then it is necessary to relate the microcraters and perforations recorded to the likely source orbit of the particle in each case. Here a single-particle approach is used to calculate the relative impact probabilities upon six orthogonal faces of LDEF for particles coming from heliocentric orbits confined to the ecliptic; the results are presented as functions of impact velocity and impact angle for each face. The flux from geocentric orbits to the Space-and Earth-pointing faces is much lower than to the other faces; experiments positioned on those faces are thus likely to be less contaminated by space debris. Particles from heliocentric orbits can impact both the Space and Earth faces, but the latter is less likely to be hit due to the shadowing effect of the planet. The cratering ratios for the East (or leading) face compared to the West (or trailing) and the Earth-directed faces are strongly dependent upon the velocities of the particles and can therefore indicate of the velocity distribution of meteoroids and interplanetary dust.
Light Scattering by Solar System Dust: The Opposition Effect and the Reversal of Polarization
Authors: Muinonen K. , Lumme K.
Published: July 2016

The opposition effect and the reversal of linear polarization, or negative polarization, at small phase angles have been almost universally observed in light scattered from atmosphereless solar system bodies (e.g., Seeliger 1887, Lyot 1929). Recent investigations have indicated that both phenomena can be qualitatively understood as resulting from a common physical mechanism: coherent multiple backscattering (Shkuratov 1989, Muinonen 1989). These findings have cast doubt on the hitherto accepted explanation that mutual shadowing alone is responsible for the opposition effect, and for the first time offer an acceptable interpretation of the polarization reversal near opposition. As for interplanetary dust, the coherent backscattering mechanism contributes both to the Gegenschein and to the almost certainly existing negative polarization branch (Roosen 1970, Lumme and Bowell 1985).

In the following, theoretical results supporting the coherent backscattering explanation are briefly presented. As future work, we suggest modeling light scattering by a particulate medium to include the first, second and, if necessary, higher orders of scattering in the range below the typical particle size.
Methods, Difficulties, and First Results in Laboratory Simulation of Cosmic Dust Electric Charging
Authors: Svestka J. , Grün E.
Published: July 2016

Particles of radii 0.2 to 3 μm and of different materials were suspended in an electrodynamic quadrupole inside a vacuum chamber and exposed to beams of electrons and ions of energies up to 20 keV and 5 keV, respectively, with the aim to simulate electric charging of cosmic dust particles. It was found that the equilibrium surface electrostatic potential of glass particles of radii 0.2 to 2 μ charged by electrons of energies 1 to 20 keV is always positive. This can be explained by secondary electron emission at lower energies of electrons and by penetration of electrons through particles with subsequent secondary electron emission mainly from the exit side at higher energies. In case of charging by ions electrostatic potential of particles is generally much lower than expected values and interpretation of results of measurement is more complicated. The most promising way to eliminate instrumental influences disturbing processes of charging seems to be a construction of a smaller suspension system in which these influences would be negligible. Parameters of such a suspension system were derived from results of measurements.
Plasma Emission from High Velocity Impacts of Microparticles Onto Water Ice
Authors: Timmermann R. , Grün E.
Published: July 2016

Collisions of icy objects play a major role in the outer solar system. The purpose of this investigation is the experimental study of plasma production by dust impacts on icy surfaces. Impact speeds ranged from 3 to 60 km/s. It was found that the dominant ion species which were released are both positive and negative water clusters. The impact charge yield from icy surfaces is approximately a factor 100 below that from previously studied gold surfaces.
The Interplanetary Medium is Thriving
Authors: Greenberg J. Mayo
Published: July 2016

Usually in presenting a summary report of a meeting one tries to pick out the highlights. In the present instance I am tempted to say that the meeting was its own highlight because there were so many fine presentations covering such a wide range of interrelated topics. The organizers are clearly to be congratulated on their timing.
Interstellar and Stellar Abundances Across the Galactic Disk
Authors: Peimbert Manuel
Published: July 2016

Observational evidence related to the chemical composition across the disk of the Galaxy is reviewed. The H2density distribution derived for the Galaxy is poorly known, consequently it is still not possible to compare theoretical models of the chemical evolution of the Galaxy with the gaseous density distribution. The H2density distribution is particularly sensitive to the fraction of carbon atoms embedded in CO molecules and to the possible presence of a C/H abundance gradient.
s-Process Elements and Galactic Evolution
Authors: Rocca-Volmerange Brigitte , Audouze Jean
Published: July 2016

Among the observations of heavy s-process elements at the surface of very metal poor stars (population II stars), Peterson 1976 and Spite and Spite 1977 recently showed that the ratio of the abundances of these elements against that of Fe increases with increasing [Fe/H].
Metal Enrichment in the First Ages of the Galaxy
Authors: Spite F. , Spite M.
Published: July 2016

It is obviously interesting to study in detail the chemical composition of extreme Population II stars since they may give indications about the processes which took place in the very first ages of the Galaxy.

It is well known that de abundance of metals in the stars of extreme Population II are smaller than in Population I stars, but it is not yet clear from the literature if all the metals, in all the metal deficient stars, are deficient by the same factor or not. However some anomalies were shown in some halo stars : over-deficiency of barium, “s process” element (Pagel 1965), over-deficiency of odd elements (Arnett 1971, Peterson 1976). These differences are however difficult to measure and are not very much larger than the possible errors of the analysis, so that according to Trimble 1975 they are “not proven”.
The Non-Linear Theory of Spiral Structure
Authors: Contopoulos G.
Published: July 2016

The main steps of the non-linear theory of spiral structure are described. Near each of the main resonances the basic periodic orbits are calculated, and the sets of non-periodic orbits that follow them are found. A different integral of motion is applicable for each set, besides the Jacobi integral. Then the initial distribution function, f, is expressed as a function of the two integrals and the corresponding angles. The final distribution function is found by averaging over the angles:Then by integratingover all velocities we find the response density σresp. In order that σrespshould be equal to the imposed density, σimpwe must adjust the parameters of the imposed spiral field. The form of σrespaway from resonances can be derived explicitely for tight ana open spirals or bars; however near the resonances σrespcan be only calculated numerically. If the imposed field has almost constant amplitude, then the amplitude of the response is very large near the Inner Lindblad Resonance. In the case of a tight spiral the azimuth of the response density maximum with respect to the imposed density maximum tends to zero outside the ILR, while it tends to -90° inside the ILR. One possible self-consistent solution has zero amplitude inside the ILR both in the case of tight spirals and of bars. Finally an important quadrupole term was found near the ILR.
Solar Cosmions
Authors: Spergel David N.
Published: July 2016

Two of the outstanding problems in astrophysics are the solar neutrino problem and the missing mass problem. The “solar cosmion”, a weakly interacting massive particle, could solve both problems. Several particle physics models have been suggested for the solar cosmion.

The solar cosmion may have other interesting astrophysical effects. It will alter the predicted helioseismology spectrum, effect horizontal branch evolution and may alter the mass-radius relationship in low mass stars. These considerations constrain solar cosmion properties.

Several laboratories have begun an active experimental search for the solar cosmion. The UCSB-UCB-Saclay silicon experiment in the Oroville mine has already placed stringent limits on solar cosmions that couple to matter through spin-independent interactions. A planned Saclay experiment may either detect or rule out the existence of “solar cosmions”.

The Sun is an powerful laboratory for exploring particle physics beyond the standard model. Even if “solar cosmions” do not exist, the Sun can help “illuminate” the search for other weakly interacting particles posited as solutions to the missing mass problem.
The Long Term Behaviour of Classical Old Novae
Authors: Bianchini A.
Published: July 2016

Quiescent novae are more stable against mass transfer rate than dwarf novae. They may however show cyclical variations of their quiescent magnitudes on time scales of years, probably caused by solar–type cycles of activity of the secondary. The probability density function of the periods of the cycles observed in CVs is similar to that for single stars. Sometimes, periodic or quasi periodic light variations on time scales of tens to hundreds of days are also observed. Although the magnitudes of prenovae and postnovae are essentially the same, the definition of the magnitude of a quiescent nova is still uncertain. At present, the hibernation theory for old novae seems to be supported only by the observations of two very old novae.
Spin Period Variations of the White Dwarf in FO Aqr/H2215-086
Authors: Augusteijn Thomas
Published: July 2016

An investigation of the rotation period variation of the white dwarf in FO Aqr/H2215-086 is presented. A cubic ephemeris is derived for the arrival times of maxima of the pulse light curve which is associated with the white dwarf rotation. Potential problems, resulting from variations of the pulse arrival time as function of orbital phase, and from the change with wavelength of the pulse light curve shape, are investigated. A possible explanation is given for the second effect, being caused by a variable contribution of a modulation at the beat period (of the pulse and orbital periods) as a function of orbital phase.
A Possible Nova from the IRAS Point Source Catalogue
Authors: Garcia-Lario P. , Manchado A. , Sahu K.C. , Pottasch S.R.
Published: July 2016

During a spectroscopic survey of IRAS sources with infrared colours similar to those in planetary nebulae, IRAS 06518-1041 revealed itself as a possible nova-like object. The spectrum of IRAS 06518 – 1041, which is shown in Figure 1, presents strong and broad hydrogen Balmer lines together with broad permitted lines of He and C. This spectrum also shows a much weaker narrow nebular component, with forbidden lines of [OIII] and narrow Hα. The mean velocity associated to the observed line widths is about 800 km s−1. The observed emission lines correspond well to typical post-novae objects in the quiescent phase (Warner, 1989). Another argument which supports the idea of this object being a nova-like star is that there are some indications of the binarity of the source if we attend to the asymmetries observed both in the Hβ and Hα profiles. The high resolution spectrum at Hα shows the presence of a sharp double-peaked central emission from a low expanding envelope at a velocity of 35±5 km s−1, together with a much broader emission with velocities of several hundred kilometers. The displacement between both components is about 130 km s−1. This broad component could be due to the presence of an accretion disk around the system with hydrogen-rich material falling onto the compact companion. This is supported by the fact that the broad emission looks like the combination of different velocity components giving rise to a complex and asymmetric line profile. From this high resolution spectrum we derive a VLSR = 57 km s−1, which points to a distance of 5.5 kpc if we adopt the model rotation curve of the Galaxy given by Pottasch (1984) and a distance of 9 kpc from the Sun to the galactic center. The large infrared excess detected by the IRAS satellite is probably the result of the formation of dust grains in the outer parts of the common envelope at a temperature of about 160 K, as can be derived from the infrared data. This infrared excess is also present in other nova-like objects and is specially important in old and slow novae (Callus et al, 1987) where the continuous ejection of mass produces dust shells which are strong emitters in the infrared.
Spectroscopic Observations of the Southern Old Novae CP Pup and V841 Oph
Authors: Bianchini A. , Friedjung M. , Sabbadin F.
Published: July 2016

New spectroscopic observations of the old nova CP Pup suggest most probable orbital period of 0.061375 days. First systematic monitoring of the very old nova V841 Oph reveals orbital motion with a most probable period of about 0.6 days. A slightly eccentric solution at P = 0.3755 days is less probable.
Measurements of Outburst Characteristics, Temperatures, Densities and Abundances in the Ejecta of Nova Muscae 1983
Authors: Hassall B.J.M. , Snijders M.A.J. , Harris A. W. , Cassatella A. , Dennefeld M. , Friedjung M. , Bode M. , Whittet D. , Whitelock P. , Menzies J. , Evans T. Lloyd , Bath G.T.
Published: July 2016

We present results for IUE, optical and IR observations of Nova Muscae 1983, from early outburst to January 1986 obtained by the European IUE Target of Opportunity Team. A detailed description of the data will appear elsewhere (Hassall et al., 1989), but here we summarise the most important results.

The outburst lightcurve initially indicated a fast speed class for this nova, but was later characterised by a rather slow optical decline with two or more secondary outbursts with sudden doubling of the bolometric flux. In Figure 1, we show the contributions of X-ray, UV, optical and IR to the total luminosity for 1200 days following outburst, assuming a distance of 4.3kpc and an interstellar extinction E(B-V)=0.5. In the absence of dust formation, first the UV and later the X-ray flux (Ögelman et al, 1984) dominate the radiative energy late into the nebular phase. There was a plateau stage lasting about 500 days, with a bolometric luminosity of ~ 1038ergs s−1 near the Eddington limit. The secondary outbursts were thus super-Eddington. We estimate a total outburst energy (including kinetic and gravitational potential energy of the ejecta) of ~ 5·l046 ergs, corresponding to a mass of ~ 4·10−6Mº of hydrogen burnt in the thermonuclear runaway.
Formation and evolution of dust in novae
Authors: Evans A.
Published: July 2016

The formation and evolution of dust grains following a nova outburst are reviewed, and various observational methods of constraining the nature of nova dust are described. Despite recent advances in understanding grain formation and evolution in classical nova systems, there remains a number of outstanding problems, the solutions to which are likely to come from studies of other aspects of the nova outburst.
Optical Observations of Recent Novae
Authors: Wolf B.
Published: July 2016

The observations of two rather different classical novae, V 1500 Cyg (= Nova Cyg 1975) and NQ Vul (= Nova Vul 1976), are presented and compared. Nova Cyg 1975 is outstanding with respect to absolute magnitude (M = -10), range of brightening (Δm = 19), and speed of evolution (t3= 3.6 days). Its prenova object had to be fainter than about magnitude 9. The corresponding values for Nova Vul 1976 are rather conservative (M≈-7.5, Δm ≈ 12, t3=40 days, absolute magnitude of the prenova ≈4.5). The light curve of Nova Cyg 1975 is very smooth. Some superimposed photometric variations of a small and slightly variable amplitude of a period of 3.4 hours are most naturally ascribed to a binary nature of Nova Cyg 1975. Nova Vul 1976 has a completely different lighteurve with extremely strong rapid irregular variations of considerably amplitude. There is a remarkable second maximum about 14 days after discovery.
Spectroscopic Observations of Recent Novae (N Per 1974, N Sct 1975)
Authors: Rosino L.
Published: July 2016

Continuing the systematic study of novae, carriedout at Asiago since 1958, two recent galactic novae, V400 Per (1974) and V373 Sct (1975) have been observed, after the announcement of the discovery, during their decline towards minimum, with the spectrographs applied to the telescopes of 122 cm and 182 cm of the Asiago astrophysical Observatory, equipped with image-tubes.
HM Sagittae: an eruptive variable resembling V1016 Cygni
Authors: Ciatti F. , Mammano A. , Vittone A.
Published: July 2016

We present photometric and spectroscopic observations (intermediate dispersion in the wavelength range 3700-10900 Å) of the recently discovered variable HM Sagittae (Dokuchaeva, 1976). Also pre-outburst data, indicating a red star, are used to discuss its nature and distance.
AM Herculis Type Stars - Magnetic Binaries
Authors: Krzemiński W.
Published: July 2016

A new class of close binary stars, proposed to be called polars, has been discovered during recent year; its prototype is AM Her. The three known polars, AM Her, AN UMa, and W Pup, are polarization, spectrum, radial velocity, optical, and infrared variables of short periods of 3.1, 1.9, and 1.7 hours, respectively (Tapia 1977 a, b, c; Michalsky et al. 1977; Krzemiński and Serkowski 1977; Stockman et al. 1978; Herbig 1960; Cowley and Crampton 1977; Priedhorsky 1977; Greenstein et al. 1977; Berg and Duthie 1977; Szkody and Brownlee 1977; Olson 1977; Mumford 1977; Priedhorsky and Krzemiński 1978; Neugebauer et al. 1977). AM Her itself has been found to have strong soft X-ray emission in the 0.1 - 0.4 keV band (Hearn and Richardson 1977) and a hard X-ray spectrum (about half the observed 2-60 keV energy lies above 28 keV, Swank et al. 1977) both modulated with a 3.1 hour period. No X-ray emissions from the other systems have been detected so far.
The Bq[] Evolved Massive Eclipsing Binary RY Scuti
Authors: Ciatti F. , Mammano A. , Margoni R. , Vittone A. , Strazzulla G.
Published: July 2016

Photometric and spectroscopic observations of RY Scuti are presented. These da ta indicate an advanced stage of this β Lyrae-type massive system, whose further e volution could lead to a SN-II event with the formation of a system like Cyg X-l.
IR Energy Distribution of OH/IR Sources
Authors: Sherwood W. A. , Kreysa E. , Schultz G. V.
Published: July 2016

Some infrared counterparts of Type II OHAR sources have been observed between 1µ and 30µ. In spite of their having very similar OH emission spectra, their energy distributions differ considerably among themselves from “flat” (1. 25µ to 4. 9µ) to “steep” (2. 2µ to 20µ). The energy distributions are compared with more familiar objects.
3. The Constitution of Cometary Nuclei
Authors: Whipple F. L.
Published: July 2016

For many comets the accelerations radially from the Sun have been determined by deviations from gravitational orbits. The radial force per unit area can be calculated on the basis of certain assumptions concerning the nature of the vaporizing material, the physical circumstances, and the geometry of the cometary nucleus. The observed accelerations combined with the calculated forces yield numerical values for (1-A)/R where A is the albedo, and R the radius of the nucleus. At extreme solar distances photometry provides the well-known quantity area-times-albedo or RA1/2. Solutions are then possible for R and A for the nuclei of the comets. The derived quantity, (1-A)A1/2, provides a limiting check on the basic assumptions and, therefore, on the basic physical properties of the nuclei. For ten short-period comets with q < 1.5 AU, the observations are satisfied by H2O ice. About half show “spotty” surfaces.

For comets of a single apparition H2O ice is generally not volatile enough to produce the observed radial accelerations. The resulting problems are discussed including the possibility that in some cases displacements of the photometric from the gravitational nucleus may produce spurious non-gravitational accelerations.

The physical characteristics of comets vary with their orbits and with their age. New comets on their first near solar passage from the Oort cloud are extremely active. The activity falls statistically with increasing age. This sequence must represent a corresponding sequence or layering of structure from the surface of a new comet inwards and is described qualitatively in this paper.

The excessive activity of new comets is ascribed to cumulative cosmic-ray damage that activates the outer few hundred gm cm-2 from the surface. The total energy input in 4.6 x 109 yr reaches 50,000 cal gm-1 near the surface so that both crystalline structures and molecules are severely damaged if not completely destroyed. Annealing at T - 10 K must be very small. Hence significant exothermic energy in the form of defects, vacancies and radicals is added to produce the extraordinary activity observed in new comets.

Other aspects and problems of cometary activity are discussed.
6. Differential Nongravitational Forces in the Motions of the Split Comets
Authors: Sekanina Z.
Published: July 2016

The new model, which has recently been proposed for the motions of fragments of the split comets, is critically examined through a comparison with the traditional approach. It is concluded that the new model, based on the premise that the rate of separation of any two fragments of a split comet is determined primarily by the differential nongravitational forces in their motions, is preferable in many a respect to the traditional hypothesis, built on the assumption that significant impulses are exerted on the fragments at the time of splitting. The new model appears to have interesting implications for the physics of cometary splitting, suggesting that the breakup mechanism may essentially be non-violent or of a low degree of violence, and for estimates of cometary masses.
10. Photometric Parameters of Comet Kohoutek 1973 XII
Authors: Kleine T. , Kohoutek L.
Published: July 2016

An analysis of the 2796 visual observations as well as of 282 V, B or U photoelectric observations was carried out using a two-parametric model for the light curve of the comet. After having applied an aperture correction to the visual observations, the following photometric parameters were derived: before perihelion n = 2.5, after perihelion n = 3.6 and a drop of m0by 1.5 -1.9 after the perihelion passage. From the UBV photoelectric data the coma was found to be more gaseous before the perihelion passage.
4. Asteroid Surface Compositions from Infrared Spectroscopic Observations: Results and Prospects
Authors: Larson H. P.
Published: July 2016

Advances in IR detector technology, the increased availability of large aperture telescopes, and the techniques of Fourier transform spectroscopy (FTS) now permit IR (λ > 1μ) spectroscopic observations of asteroid surfaces. Asteroids already observed include Ceres, Vesta, and Eros. These initial results demonstrate that such studies can contribute new data concerning asteroid compositions. Some of the most diagnostic features of mineral spectra are in the IR spectral region, and for featureless spectra characterized only by slopes the extension of the spectral reflectivity curve into the IR provides tighter constraints on possible mineralogies. A systematic study of additional asteroids should exploit even further this new observational link to problems of meteorite origin and solar system evolution.
3. Fragmentation of Asteroids and Delivery of Fragments to Earth
Authors: Wetherill G. W.
Published: July 2016

Earth-impacting meteoroids are derived from both comets and asteroids, and some uncertainty still exists regarding with which of these bodies some stone meteorites should be identified. In contrast, the long cosmic ray exposure ages of iron meteorites strongly suggest a long-lived asteroidal source capable of providing ~108g/yr of this material to the earth’s surface over at least much of solar system history. Spectrophotometric data show that differentiated asteroids are concentrated in the inner portion of the asteroid belt. The orbital histories of fragments of inner belt asteroids are investigated, considering the combined effects of close planetary encounters, secular perturbations, and secular resonances. Particular attention is given to the low inclination (<15°) objects with small semimajcr axis (2.1 to 2.6 A.U.), which can make fairly close approaches to Mars (<0.1 A.U.). It is found that the annual yield and dynamical lifetime of collision fragments of these asteroids is in agreement with the observed impact rate and exposure age of iron meteorites. A smaller yield of stone meteorites (-107g/yr) is expected, because elimination of these objects by collision is probable on the long dynamical time scaTe. Achondrites could be produced in this way; the yield is probably too low to account for chondrites. Chondrites could possibly be derived indirectly from these bodies insofar as these asteroids are also sources of Apollo and Amor objects.
1. Interstellar Material in Meteorites: Implications for the Origin and Evolution of the Solar Nebula
Authors: Clayton R. N.
Published: July 2016

Several isotopie anomalies, unexplained by known nuclear or non-nuclear processes within the solar system have been attributed to the preservation of pre-solar variations. The largest of these (in number of atoms) in an 16O-excess (up to 5%) in “high-temperature condensate” minerals in primitive meteorites. Some of these same minerals have an excess of 26Mg, probably a decay product of 26Al, that could have been a major source of heat for melting and metamorphosing planetesimals. Excesses of 22Ne and of isotopes of Xe, found in carbonaceous chondrites, may have origins in presolar solid particles. Large variation in the isotopie abundances of nitrogen and carbon in meteorites may also represent isotopie heterogeneity in the solar nebula. Most of these “Isotopically anomalous” elements are found to be highly concentrated in minute phases within the meteorites, rather than being uniformly distributed. The identification and characterization of these carriers of presolar materials constitutes the principal thrust of current research in this area.
8. Meteorites in Meteorites: Evidence for Mixing among the Asteroids
Authors: Wilkening L. L.
Published: July 2016

Inclusions of one type of meteorite enclosed in another have been found in several gas-rich meteorites, unequilihrated chondrites and mesosiderites. The inclusions in all but one case are chondritic; a majority are mineralogically and isotopically similar to carbonaceous chondrites. These meteorite mixtures most probably resulted from collisions among asteroids.
1. The Origin of Iron Meteorites
Authors: Kelly W. R. , Rambaldi E. R. , Larimer J. W.
Published: July 2016

The chemistry of iron meteorites is compared to predictions of the chemical fractionations that develop during the cosmic history of the metal phase, from condensation and accretion through melting, segregation and freezing. Of the 12 resolved iron meteorite groups, 3 appear to have evolved in bodies which accreted at T > 1000° K. In several cases, the core-forming process seems to have ceased prematurely, just as the metal began to melt and flow (group IAB with its silicate inclusions) or after the metal aggregated into pods but before it sank to form a core (group IVA, with groups IIAB and IIIAB being in more advanced stages). The Shaw chondrite contains residual metal from a partial melting process, as required to complement the fractional melts which refroze prematurely in the case of group IAB meteorites.
3. A Former Major Planet of the Solar System
Authors: Van Flandern T. C.
Published: July 2016

Dynamical calculations by Ovenden, indicating the former existence of a 90-Earth-mass planet in the asteroid belt, have now been supported by a study of orbital element distributions of very-long-period comets. The indicated epoch for disintegration of the planet is just 5 x 106 years ago.
5. On the Early Scattering Processes of the Outer Planets
Authors: Ip W. H.
Published: July 2016

The gradual scattering of small bodies by the Jovian planets in the late stage of their accretion is simulated by Monte Carlo calculation. The effects of collisional interaction of the scattered planetesimals with the inner planets and asteroidal belt are estimated. The total mass influx injected into the terrestrial zones from the outer planetary zone could be appreciable; however, if the damping effects due to the mutual inelastic or catastrophic collisions among the small bodies were significant, the total mass influx would be greatly reduced. The origin of the cometary Oort cloud in relation to these scattering processes is also discussed. The calculation indicates that, in addition to Jupiter, Uranus and Neptune were likely to be the major contributors to the population of long-period comets if they originated from such scattering processes.
11. The Role of Protoplanets in the Formation of the Solar System
Authors: Williams I. P.
Published: July 2016

A likely origin of the asteroids (and possibly, of the comets?) is the natural outcome of the following scenario that we propose for the formation of the planets. Protoplanets of similar mass and solar composition will segregate in three different ways: For those far enough from the sun (like Uranus and Neptune), the segregation of icy grains releases enough energy to drive the remaining gases to infinity. For all other planets, the segregation of refractory material only does not release enough energy to disrupt the protoplanet; however, while spiraling inwards in a resisting medium, the terrestrial protoplanets cross their Roche limit and lose their gaseous outer layers. Asteroids (or comets) could therefore originate from the disruption of protoplanets before the settling of their refractory (or icy) grains is completed.
GRADES: A New Instrument for Spectroscopy of the Local Hot Gas
Authors: Hurwitz M. , McKee C. , Edelstein J. , Vallerga J. , Jelinsky P. , Freyberg M. , Breitschwerdt D.
Published: July 2016

Competing models for the origin of the local component of the diffuse X-ray background span more than an order of magnitude in temperature. We propose to test these models with a new instrument, the GRating Array Diffuse EUV Spectrometer (GRADES), which is sensitive to diffuse emission in the 90 – 260 Å bandpass, and offers a peak spectral resolution of about λ/127.
On the Zero-Level of the Soft X-ray Background
Authors: Freyberg M.J.
Published: July 2016

The soft X-ray background (SXRB, 0.1 – 2.0 keV) is generally believed to be comprised of a local component, the Local (Hot) Bubble (LHB), which is only marginally absorbed, and of distant emission (galactic halo, extragalactic background). It is vital to know the foreground emission (spectrum, intensity) if one wants to disentangle and determine the 3-dimensional structure of the X-ray emitting regions. During the ROSAT PSPC All-Sky Survey non-cosmic enhancements of the measured X-ray count rate have been observed. These lasted typically for up to 8 hours (i.e. a couple of orbits). Using PSPC data it has been shown that these so-called “long-term enhancements” (LXE) are related to geomagnetic storms and variations of the solar wind. Moreover, during an observation of the comet Hyakutake indications for a correlation of the X-ray background with the X-ray brightness of the comet have been found. This can be interpreted in terms of an X-ray emitting region around the Earth. Although the variable component of these enhancements could be subtracted from the sky maps an uncertainty remained concerning an undetected and relatively constant contribution which might be present in soft X-ray observations. As a consequence this could explain or contribute to the high PSPC count rate observed from the dark side of the Moon.