bluuebunny/crossref_metadata_2025 huggingface dataset:
Formation of Luminous Contact Binaries by Rapid Accretion onto White Dwarfs
Authors: Nomoto Ken'Ichi , Nariai Kyoji , Sugimoto Daiichiro
Published: July 2016

During the evolution of a close binary system, there is a phase of mass exchange between its component stars. When the mass-losing star is an evolved star off the main sequence, the mass exchange is very rapid. Its rate may well exceed the critical accretion rate corresponding to the Eddington limit of the mass accreting star. Effects of such a rapid accretion were studied for the mass-accreting main-sequence stars (Flannery and Ulrich 1977; Kippenhahn and Mayer-Hofmeister 1977; Neo et al. 1977). The mass-accreting stars become quickly overluminous and their radii increase even to a red-giant size as mass is accumulated. Then the both component stars will fill their Roche lobes to form a contact binary system.
The Evolution of Pre-Main Sequence Close Binaries
Authors: West Jon K. , Chen Kwan-Yu
Published: July 2016

Conventional computer models of close binary star systems usually start with at least one component on the main sequence. Models of premain sequence binaries have been computed to study mass transfer (Yamasaki 1971). However no pre-main sequence computations have been published that follow the evolutionary tracks of a binary system onto the main sequence, even though some observed systems appear to be premain sequence (Field 1969). The main purpose of this investigation is the evaluation of individual close binaries with a pre-main sequence model. The evaluation will be accomplished by comparing the positions of the observed binary on the Hertzsprung-Russell diagram with the evolutionary tracks generated by the pre-main sequence model. If both components appear to have the same age and fall near the tracks of the model, then the system is possibly pre-main sequence. Eleven semidetached binaries were considered, each with a total mass between 2.5 and 6 solar masses and with a period between 0.9 and 3.4 days.
Anomalous Mass Ratios in O-Star Binaries
Authors: Garmany Catharine D. , Conti Peter S.
Published: July 2016

A study of the binary frequency among the O-stars finds that only 40% are binaries. They show a strong tendency to have mass ratios near unity and none with values less than 0.3. We discuss the evidence that mass loss is responsible for the observed mass ratios.
Observations of Wolf-Rayet Binaries
Authors: Niemela Virpi S.
Published: July 2016

In many recent papers dealing with computations of evolutionary sequences for massive stars with mass loss, the evolutionary status of Wolf- Rayet stars has been discussed. When one whishes to compare these theoretical computations with observations, it is of great importance to know the masses of Wolf-Rayet stars, which unfortunately are well determined only in a few cases. Estimates of the masses are provided by binaries with WR type components. I will report here preliminary results of spectrographic observations for 4 WN+OB systems, with new information about the masses of their components.
Wolf-Rayet Binaries
Authors: Moffat A.F.J. , Seggewiss W.
Published: July 2016

An updated list of known spectroscopic double-line and single-line Galactic Wolf-Rayet binaries is presented. From this we discuss e.g. mass ratios, the binary frequency and the evidence for low-mass unseen (compact?) companions. Spectroscopic binary orbits of several WR stars in the Magellanic Clouds are noted for the first time.
The Interpretation of Light Curves λλ2460 : 35000Å of the Eclipsing Wolf-Rayet Binary V444 Cyg
Authors: Cherepashchuck A. M. , Eaton Y. A. , Khaliullin Kh.F.
Published: July 2016

The structure of the extended atmosphere and the physical characteristics of the WN5 star V444 Cyg have been determined from the analysis of light curves of this system in the range λλ2460 − 35000. The radius of the core of the WN5 star at τ = 1 is ro = 2.9R⊙; the temperature at the surface of the core is equal to 90000oK, the electron density at its surface is 0.9 · 1013 cm−3. The bolometric luminosity of the WN5 star Lb = 2.1039 erg/s is close to the critical Eddington luminosity 2.6 · 1039 erg/s. The electron temperature decreases monotonically with height through the extended atmosphere from the value Te = 80000° − 90000°K at r = 2.9R⊙ to the value Te = 20000° − 30000°K at r = 8R⊙. The outflow velocity at the surface of the core (ro = 2.9R⊙, τ = 1) is vo = 400 km/s; the outflow in the region r ≥ 12R⊙ becomes stationary with the constant velocity v = 1000 − 1200 km/s. The total interstellar absorption for the system V444 Cyg is Av = 2m.66. The results obtained confirm strictly the model of Wolf-Rayet phenomenon proposed by Beals (1944). Chromospheric-coronal effects in the extended atmosphere are absent until r = 20R⊙. Characteristics of the WR star are consistent with the predictions of the evolution theory for massive close binary systems with mass exchange. The WR star is in a late evolutionary stage after the main sequence stage, being a helium remnant that has been formed as a result of the mass exchange.
Abundance of Sodium in the Atmospheres of Algol A and B
Authors: Kondo Masayuki , Okazaki Akira
Published: July 2016

The Na D1 and D2 lines of Algol A and B observed by Tomkin and Lambert(1978) were analyzed to obtain sodium abundance. A mild deficiency of sodium [Na/H]∼-0.5 is found in Algol B, while a slight overabundance [Na/H]∼+0.3 is found in Algol A.
On the Location of Radio and X-Ray Emission in the Algol System
Authors: Florkowski D. R.
Published: July 2016

The radio behaviour of Algol at centimeter wavelengths has been reviewed by Hjellming (1976, 1977), and by Gibson (1976). The observed radio emission can be roughly divided into two types: a quiescent type and a flare-like or outburst type. The quiescent emission is characterized by a low flux density, usually between 20 − 50 mJy, and a nearly flat spectral index. The latter means that the value of the flux density is nearly independent of wavelength. The variations in flux density, when present, are gradual and have a time scale on the order of days. The flare-like behaviour shows rapid and large changes in flux density. The amplitude of an outburst is wavelength dependent, the shorter wavelengths having larger amplitudes. Woodsworth and Hughes (1976, hereafter WH) attributed the two types of behaviour to two physically distinct sources. The quiescent type of emission is produced by a very large, thermally emitting cloud which surrounds the eclipsing system. The flare-like variations are due to a synchrotron source that is associated with mass loss. Their model is inconsistent with optical and X-ray information concerning the Algol system. However, a model with two radio components can be modified to agree with other types of data.
IUE Ultraviolet Spectra of the Interacting Binary U Cephei
Authors: Kondo Yoji , McCluskey George E. , Stencel Robert E.
Published: July 2016

The eclipsing binary U Cephei has proven to be of great interest in the study of stellar evolution in close binary systems. Batten (1974), Hall and Walter (1974), Rhombs and Fix (1976), Markworth (1977), and Olson (1978), among others, have recently reported on their intensive ground based studies of U Cephei. Kondo, McCluskey and Wu (1978) have investigated the ultraviolet light curves of U Cephei obtained with Astronomical Netherlands Satellite (ANS). Kondo, McCluskey and Stencel (1979) have discussed the International Ultraviolet Explorer (IUE) spectra of U Cephei. This paper discusses results incorporating additional IUE high resolution spectra of U Cephei obtained in both far-ultraviolet and mid-ultraviolet spectral regions.
On the Existence of Double-Contact Binaries
Authors: Wilson R. E. , Twigg L. W.
Published: July 2016

We present observational evidence relevant to the existence of binaries of the morphological type proposed by Wilson (1979), called double-contact binaries. Consider normal evolution with Roche lobe overflow, in the rapid phase of mass exchange. It is well known that such mass-exchange spins-up the accreting star (most of whose mass is transferred material by the end of the rapid phase). Many examples are known (Table 1, for example) of Algol-types with fast-spinning primaries (original secondaries). Suppose the accreting star has been spun-up so much that it cannot accept further high-angular momentum material. It will then be filling its limiting rotational lobe (but not its Roche lobe). The secondary (original primary) will still be filling its Roche lobe. The overall result is that both stars fill their limiting lobes accurately, but are not in contact with one another. Since it is common to speak of “the contact component” of a semi-detached system - meaning the one in contact with its limiting lobe - it seems natural to call members of the new morphological type “double-contact” systems. Of course, there must be a repository for the mass lost by the Roche lobe filling and rotational lobe filling components. This would naturally be the circumstellar disks around the primary components of such systems as β Lyr and V356 Sgr (Wilson and Caldwell, 1978). The end of the double-contact phase would occur when the rate of transfer of rotational angular momentum back into the orbit, by tidal braking, begins to exceed the rate of transfer of angular momentum the opposite way by mass exchange.
Narrow Band Photometry and Observable Effects in Algol Type Systems
Authors: Budding E.
Published: July 2016

The application of narrow band photometry to Algol type systems is considered and advantageous circumstances pointed out. Observable effects can be divided into two kinds: classical (associated essentially with differential centre to limb variation) and interactive (where an emission component may be present in the line). Observations of U Sge and β Per are discussed from this basis and deductions made about the size and shape of an emitting region. Conclusions are compared with theoretical ideas about such regions and their expected stability, both for these and other similar systems.
X-Ray Binary Systems
Authors: Crampton David
Published: July 2016

X-ray emission has now been detected from a large number and variety of binary systems. A brief survey of the properties of these binary systems is given, primarily from an optical standpoint.
A Critique of the Polarimetric Evidence on the Nature of CBS
Authors: Simmons J.F.L. , Aspin C. , Brown J. C.
Published: July 2016

Determination of the values and confidence intervals for physical parameters and the orbital inclination of binaries from polarimetry is critically discussed. A new method based on X2 best fitting and incorporating constraints imposed by the canonical model is developed and applied to polarimetric data for Cygnus X-1. Whereas the X2 best fitting procedure yields an inclination of |i| = 79° for Cygnus X-1, the level of noise, and the model dependency of the parameter determination give rise to a very broad confidence interval around this value. Our method also indicates the accuracy of the polarimetric measurements necessary for more precise parameter determinations.
Radio Flares in the Circinus X-1 System
Authors: Nicolson G. D.
Published: July 2016

The 16.6 day periodic radio flares in Circinus X-l have been observed at 6 cm wavelength from February 1978 to May 1979. Two strong flares occurred in February 1978 followed by a long period of quiescence until flaring recurred in January 1979. The onset of the flares was however 18 hours earlier in the 16.6 day cycle than previous flares. Similar behaviour has been reported for the X-ray emission and it is concluded that both the X-ray and radio emission are caused by mass transfer at peristron in an eccentric binary with a 16.6 day period. Each radio flare generally shows a multipeaked structure with the first maximum being the strongest. There is also a systematic trend for the subsequent peaks to become weaker with each cycle and this suggests that the compact object precesses in relation to an accretion disc.
Period Changes and Mass Loss Rates in 34 RS CVn-Type Binaries
Authors: Hall Douglas S. , Kreiner Jerzy M. , Shore Steven N.
Published: July 2016

We have collected all available times of minimum, over 1650, for 23 regular, 7 short-period, and 4 long-period eclipsing RS CVn binaries using the card catalogues at the Sternberg Astronomical Institute and the Krakow Astronomical Observatory, as well as unpublished data. We examined them critically, discarded those grossly in error, and assigned weights. For AD Cap, RV Lib, and ε UMi there are virtually no data. For the remaining 31 we determined quadratic ephemerides by weighted least squares. Values of d1nP/dt are given in the Table with their errors. Roughly 2/3 are variable at greater than the 2 σ level. Significant decreases outnumber significant increases by almost 2:1. We show that light curve asymmetry produced by the distortion wave probably accounts for the relatively small, rapid fluctuations in the O-C curve but not the long-term period changes.
Radio Flare Activity of RS CVn Stars
Authors: Feldman Paul A.
Published: July 2016

For several years, a systematic program to observe RS CVn and similar binaries has been undertaken with the 46-m telescope of the Algonquin Radio Observatory. A number of large radio outbursts at 2.8 cm wavelength has been found from HR 1099, AR Lac, SZ Psc, UX Ari, and HR 5110. In several cases, simultaneous, or nearly simultaneous, observations of these stars were made by cooperating observers at (other) radio, optical, UV, and X-ray wavelengths. It is now clearly established that the mechanism responsible for the cm-wavelength radio emission is nonthermal gyrosynchrotron radiation in a volume whose characteristic dimension is comparable with the binary star separation. More generally, a semi-quantitative model for the radio flare activity of these stars seems to be possible using greatly scaled-up analogues of solar magnetic activity.
W UMa Stars and Angular Momentum Loss
Authors: Vilhu Osmi , Rahunen Timo
Published: July 2016

The structure and evolution of W UMa stars is still unsolved although considerable progress has been achieved in recent years. Most theoretical studies are based on the common convective envelope model by Lucy (1968a,b), which almost satisfactorily explains the nearly equal minima of the light curves. All A-type (Wilson, 1978) and some W-type systems (Whelan et al., 1979) may contain an evolved primary. In this case stable models exist (Hazlehurst, 1970; Moss and Whelan, 1970). Computations performed for the subsequent evolution (Moss, 1971; Hazlehurst and Meyer-Hofmeister, 1973; Rahunen and Vilhu, 1977) show nuclear time scale evolution towards more extreme mass ratio, supplemented by possible thermal time scale oscillations.
Energy Transfer by Circulation in W Ursae Majoris Systems
Authors: Smith David H. , Smith Robert Connon , Robertson J. Alistair
Published: July 2016

After Lucy (1968) introduced the contact-binary model with a common convective envelope, it was envisaged by Hazlehurst & Meyer-Hofmeister (1973) that a sideways flow of convective elements would carry energy from the more luminous star, the primary, to the less luminous star, the secondary, as a result of horizontal pressure variations. Webbink (1977) extended this picture by noting that the interaction between vertical entropy gradients and large-scale smooth circulation currents in the common envelope would provide the necessary redistribution of flux. That is, energy is absorbed by the flow during its vertical motion in the primary and is released during its vertical motion in the secondary. Webbink (1977) mentioned two mechanisms by which a large-scale circulation could be generated: (1) the non-spherically symmetric force field due to rotation and tides which will drive an analogue of classical Eddington-Sweet circulation and (2) differential heating of the base of the common envelope. Although these mechanisms are conceptually different, they are not in practice easy to disentangle, and will certainly both be operating in contact binaries.
Low Color Temperature Variations over the Common Envelope of W Ursae Majoris and the Cause of Its W-Type Light Curve
Authors: Eaton J. A. , Wu C. - C. , Rucinski S. M.
Published: July 2016

We discuss ultraviolet photometry of the eclipsing binary W Ursae Majoris obtained with the Groningen instruments on the Astronomical Netherlands Satellite (ANS). Fifty measurements of this star's brightness were obtained for each of the bandpasses at 2200, 2500, and 3300 Å. This new data is significantly more precise than Rucinski's OAO-2 photometry, enabling us to draw definitive conclusions about the distribution of brightness on the surface of W UMa. The ultraviolet light curves are generally similar in shape to those for optical passbands; the amplitudes are greater in the UV, while the depths of the primary and secondary eclipses are nearly equal at both 2200 and 2500 Å. We have analyzed the (2200 − 3300) color curve to determine how much the color temperature varies over the common envelope, concluding that any such temperature variations must be small. In terms of the traditional surface-brightness parameters for gravity darkening, temperature excess of the smaller component, and bolometric albedo, we find β = 0.03 ± 0.01, X = ΔT/T = 0.000 ± 0.009, and Abol = 0.4 ± 0.4. Further, we conclude that the star is limb darkened considerably more at 2200 than at 3300 Å.
Mass Loss from Contact Binary Systems and their Dynamical Evolution
Authors: Nariai Kyoji
Published: July 2016

When there is mass loss from a binary system, the lost mass carries energy and angular momentum out of the system. Therefore, the remaining system must adjust its orbital parameters to the changing values of the total kinematic energy E and the total angular momentum N as the total mass M decreases. The parameters concerned here are : the fractional mass μ, the semi-major axis a, and the eccentricity e.
A Search for Spectroscopic Binaries Among Planetary Nuclei
Authors: Méndez Roberto H.
Published: July 2016

The present paper is a progress report on a search for spectroscopic binaries among central stars of planetary nebulae. In the last few years it has become clear that such a program may result in a significant improvement of the available information about the central stars, and, whatever the outcome, it will certainly help to test current theoretical work on the origin of planetary nebulae.
Research into astronomical refraction - today and tomorrow (A Survey Paper)
Authors: Teleki G.
Published: July 2016

Proceeding from the present-day and future needs of astrometry, current researches into astronomical refraction as well as its prospective development are analysed. Particular attention is dedicated to the constructing of new refraction tables, determination of the refractional influences by way of experiments, site selection of the observing stations and to the preventive measures to be taken at them. Need and usefullness are emphasized of the cooperation of experts specialized in astronomical, terrestrial, photogrammetric, radio and other kinds of refractional influences.
Calculating astronomical refraction by means of continued fractions
Authors: Mikkola S.
Published: July 2016

A continued fraction was derived for the summation of the asymptotic expansion of astronomical refraction. Using simple approximations for the last denominator of the fraction, accurate formulae, useful down to the horizon, were obtained. The method is not restricted to any model of the atmosphere and can thus be used in calculations based on actual aerological measurements.
Chromatic refraction in the vertical circle observation
Authors: Bagildinsky B. K. , Puliaev S. P. , Zhilinsky E. G.
Published: July 2016

In 1962 a photographic vertical circle (PVC) for determining absolute declinations was designed and constructed at the Pulkovo Observatory under the supervision of Prof. M.S. Zverev (Zverev, M.S., 1960). The Maksutov meniscus cassegrain system (D = 200 mm, f′ = 2000 mm) was used for the first time in astrometry. Its construction is symmetric and it is automatically operated. In 1963–1966 the declination observation of bright and faint stars of the southern hemisphere was made with this instrument (Zverev, M.S. et al., 1966). At present after the reconstruction the PVC has been used again for determination of absolute declinations (Bagildinsky, B.K., Usanov, D.S., Smirnov, B.N., 1978).
Two color refractometry, precision stellar catalogs, and the role of anomalous refraction
Authors: Currie Douglas G.
Published: July 2016

Atmospheric refraction, with its non-predictable variations, is one of the dominant sources of error in the precise determination of the apparent position of a star. It appears that this will be the dominant error source for the new generation of instrumentation now being installed for the determination of stellar catalog and Universal Time (i.e., the USNO 65-cm PZT). The effects of anomalous refraction measurements of stellar position propagate to the various quantities derived from this data. This includes the compilation of stellar catalogs, the determination of Universal Time, and variations in the latitude.
The accuracy of the determination of terrestrial refraction from reciprocal zenith angles
Authors: Ramsayer K.
Published: July 2016

To investigate the accuracy of the determination of terrestrial refraction from reciprocal zenith angles and astronomical latitudes and longitudes at both ends of a line a test net with lines from 4 km to 23 km was observed and three dimensionally adjusted. As the measurements of the zenith angles were repeated every hour 40 times in an average the adjusted values were taken as a substitute for the true values. It is shown, that the mean refraction coefficient k, which is changing from k = 0.10 at day up to k = 0.34 at night, and the corresponding refraction angle can be determined very accurately, if both angles are measured simultaneously. Observations with day light are better than observations in the night. For observations with day light the mean difference between the true refraction angle at the observation station and the mean refraction angle of the observed line was smaller than ± 1″ independent of the length of the line. That means that the mean deviation of the true effective refraction coefficient in the observation station and the mean refraction coefficient of the observed line was inverse proportional to the distance.
Possibilities of increasing the accuracy in the determination of refractional angles with Tengström's IDM
Authors: Milewski J.
Published: July 2016

The main purpose of the IDM research of prof. Tengström was to confirm the possibility of determining instrumentally the refraction angle in the field even over long distances.

An appreciable increase of the accuracy could only be achieved by further improvement of the instrument. Even with the first laboratory model it seems possible to achieve an increase of the accuracy in the final results. This paper discusses the above possibilities and proposes some methods to achieve this improvement in the accuracy.
On precursors of electromagnetic wave propagation
Authors: Brunner F. K.
Published: July 2016

The precursor theory of an electromagnetic wavetrain propagating through a dispersive medium is briefly reviewed. The few successful experimental determinations of these precursors, which have been reported in the literature, are limited to transients in waveguides. The determination of precursors in the optical frequency range appears to be achievable in the laboratory. However, in the geodetic context of long wavepaths through the troposphere the utilisation of precursors for measuring distances and directions free of atmospheric effects is judged as not feasible at the present time.
Four Years of Zodiacal Light Observations from the Helios Space Probes: Evidence for a Smooth Distribution of Interplanetary Dust
Authors: Leinert C. , Richter I. , Pitz E. , Hanner M.
Published: July 2016

The zodiacal light experiments on Helios 1 and Helios 2 have been continually operating since launch in December 1974 and January 1976, respectively. The data support the view that the distribution of interplanetary dust is rather simple in space and quite constant in time. Instrument and data reduction have been described by Leinert et al. (1978). In the following we present Helios 2 data only.
Brightness and Polarization of the Zodiacal Light: Results of Fixed-Position Observations from Skylab
Authors: Weinberg J. L. , Hahn R. C.
Published: July 2016

In an earlier paper Sparrow et al. (1976) found the polarized brightness of zodiacal light to have solar color at five sky positions for which there were fixed-position observations from Skylab: north celestial pole, south ecliptic pole, vernal equinox, and two places near the north galactic pole. The brightness and degree of polarization of zodiacal light at these sky positions are derived using Pioneer 10 observations of background starlight from beyond the asteroid belt (Weinberg et al., 1974; Schuerman et al., 1976) and the assumption that the zodiacal light is also solar color in total light.
An Attempt to Observe Zodiacal Light at 5μ with a Balloon Experiment
Authors: Pitz E.
Published: July 2016

Observations of the infrared emission of the interplanetary dust enable a more direct analysis to be made of interplanetary dust material than is possible from observations of the scattered sunlight. A liquid nitrogen cooled photometer with Indium Antimonide detectors is described which has been developed for balloon-borne observations of the zodiacal light. The provision of both difference and absolute flux measurement modes will allow the observation of the zodiacal light, and the presumably much more intense emission of the high atmosphere, respectively.
Two-dimensional Photographic Photometry of the Zodiacal Light from Spatial Observations
Authors: Lamy P.L. , Llebaria A. , Koutchmy S.
Published: July 2016

Preliminary results for the photometry of a photograph of the inner zodiacal light taken aboard Saliout 6 are reported. The Very Wide Field Camera to be flown aboard Spacelab 1 is described and the program of observations of the zodiacal light is presented.
Orbit, Chemical Composition and Atmospheric Fragmentation of a Meteoroid from Instantaneous Photographs
Authors: Babadzhanov P. B. , Getman V. S.
Published: July 2016

Difficulties in the interpretation of the meteor phenomenon have been mainly caused by the impossibility of dividing in time and space the information obtained from the observations. To a certain extent the use of the method of instantaneous exposures can help to overcome these difficulties. The present paper deals with the study of a bright meteor N 770533, broken into many fragments and its spectrum, which was doubly photographed in 1977, July, 19h 30m 56s UT in Dushanbe (Figure 1). The photographs were taken by the method of instantaneous exposures, which has been described by Babadzhanov and Kramer (1968). To take the photographs of spectra, transparent replica diffraction gratings with light concentration in the first order have been used. Rotating shutters made it possible to obtain meteor images in integrated light with duration of 0.00056s every 0.02s, as well as to obtain spectra with durations of 0.00056s and 0.0033s every 0.02s. A panchromatic emulsion with spectral sensitivity 3800 to 7000 Å was used.
Experimental and Theoretical Study of Radiometeors
Authors: Delcourt Jean
Published: July 2016

We study the long-term evolution of the orbits of meteoric particles subjected to planetary perturbations and to Poynting-Robertson drag. Solar wind erosion of the particle is considered. We compute the long-period elliptic elements of the meteoric orbit when it intersects the orbit of the Earth. We compare experimental results with those of the dynamical study.
On Time-dependent Models of the Meteoric Background Complex
Authors: Štohl Ján
Published: July 2016

Continuous models of the meteoric background complex are discussed and analysed on the basis of observational data on radiants and hourly rates of sporadic meteors. A time-dependent, bi-elliptical model of the true radiant distribution fits the observational results.
Evolution of Orbits and Intersection Conditions with the Earth of the Geminid and Quadrantid Meteor Streams
Authors: Babadzhanov P. B. , Obrubov Yu.V.
Published: July 2016

The Geminids and Quadrantids belong to the most active annual meteor showers. The distinct difference between the orbit sizes of large and small meteoroids in these streams has been shown. From this, the estimated age of the streams greatly exceeds the time since their discovery in the XIX century (Geminids in 1862, Quadrantids in 1830) (Lovell 1954, Hindley 1972).
The Structure of the Taurid, Geminid and Quadrantid Meteor Streams
Authors: Lokanadham B.
Published: July 2016

The Taurids, Geminids and Quadrantids represent meteor streams existing at different stages of stream evolution. This can be inferred from the duration of their activity, more than a month for Taurids, a few days for Geminids and only a few hours for Quadrantids. The structure of the streams can be deduced from a study of the variations in incident flux of shower meteors and their mass exponents as a function of solar longitude. This paper is an attempt to deduce such structure from recent observations in India combined with data available for these showers from the early years of this century (Lovell 1954, Olivier 1960, Rao et al. 1975,1976, Webster et al. 1966).
Evidence for Fragmentation of Strongly Nonspherical Dust Particles in the Tail of Comet West 1976 VI
Authors: Sekanina Z. , Farrell J. A.
Published: July 2016

Following Sekanina's (1976a,b) suggestion that striae (also known as “synchronic” or pseudosynchronic bands) observed in the dust tails of several comets could be products of fragmentation of friable dust particles ejected from the nucleus, we have completed an investigation of these structures in Comet West 1976 VI (Sekanina and Farrell 1979, detailed paper in preparation), which shows that the dynamical solutions, provided by the fragmentation model on the assumption that solar attraction and radiation pressure are the only forces involved, are indeed in agreement with the observed motions of 16 striae through the tail over a time interval of more than three days. The match is so good that the probability of its being a coincidence of some sort must be virtually nil.
Collisions Among Interplanetary Dust Grains
Authors: Sergeant L.B. Le , Lamy P.L.
Published: July 2016

Assuming that the zodiacal cloud is composed of two populations, the effect of collisions among the largest grains is investigated. It is found that the population of fragments is unable to explain the observed flux of submicron grains.
A Two-Stream Instability in Streams of Charged Grains
Authors: Havnes Ove
Published: July 2016

We study the conditions for the onset of two-stream instabilities in interacting streams of charged grains. These conditions are such that instabilities cannot be important in the solar system of today and have probably been of very limited importance in the protoplanetary cloud.
A Monte Carlo Simulation of the Mass Distribution in an Accreting System of Dust Particles
Authors: Daniels Paul A. , Hughes David W.
Published: July 2016

This paper investigates the way in which the mass distribution index, s, of the particles in a dust cloud varies as a function of time and particle mass, assuming that accretion, and only accretion, takes place after interparticle collisions. The approach is an extension of one first put forward by Napier and Dodd (1974). Two cases are considered. In the first the cloud starts with 500 particles of unit mass and as accretion takes place, more unit mass particles are added to keep that number constant at 500. This simulates a constant source feeding the low mass end of the distribution. In the second case the cloud starts with 5000 particles of unit mass and no additions are made. This corresponds to accretion in a closed system.
From Interstellar Dust to Comets to the Zodiacal Light
Authors: Greenberg J. M.
Published: July 2016

We consider the consequences of the assumption that the interplanetary particles which produce the zodiacal light have evolved from interstellar dust via comets. The chemical evolution of interstellar dust followed by the process of aggregation into the cometary nucleus and the subsequent ejection of cometary debris provide the basis for a model for the interplanetary particles. The scattering properties of these particles are reasonably consistent with current observations of the variation with elongation angle of the brightness and polarization of the zodiacal light. The major chemical constituents of the model are in the form of a matrix of volatile ices and complex nonvolatile molecules containing C, N and O in which are imbedded silicate and metallic inclusions.
Existence and Role of Amorphous Grains in the Solar System
Authors: Smoluchowski R.
Published: July 2016

Consideration of the nucleation and growth processes and observational arguments suggest that besides crystalline grains in the solar system and interplanetary space there are also amorphous H20-ice, Si02 and C grains. Of particular importance are effects of the bombardment of these grains by protons in the solar wind and in the planetary radiation belts and the ensuing various erosion processes. Differences in the physical properties of crystalline and amorphous grains lead to interesting astrophysical consequences.
Orbits of Submicron Lunar Ejecta in the Earth-Moon System
Authors: Chamberlain J. D. , Alexander W. M. , Corbin J. D.
Published: July 2016

Flux measurements of picogram dust particles near the lunar surface and in selenocentric and cis-lunar space made by Lunar Explorer 35, HEOS, and ALSOP dust experiments all indicate, to varying degrees, ejecta from lunar impacts of interplanetary dust particles. The orbits of these submicron particles in the earth-moon system are significantly altered by radiation pressure. Recent orbit calculations show that, in favorable lunar phases, as many as 80% of the ejecta may enter the magnetosphere and 20% may enter the earth's atmosphere. The results of this analysis are presented, and their implications are discussed.
Evolution of Coronal and Interplanetary Magnetic Fields
Authors: Levine Randolph H.
Published: July 2016

Numerous studies have provided the detailed information necessary for a substantive synthesis of the empirical relation between the magnetic field of the sun and the structure of the interplanetary field. We will point out the latest techniques and studies of the global solar magnetic field and its relation to the interplanetary field. The potential to overcome most of the limitations of present methods of analysis exists in techniques of modelling the coronal magnetic field using observed solar data. Such empirical models are, in principle, capable of establishing the connection between a given heliospheric point and its magnetically-connected photospheric point, as well as the physical basis for the connection. We thus find ourselves at a plateau, looking back over a quarter century of empirical synthesis while anticipating a new era of detailed physical investigation on a global scale.
Coronal Structure and Solar Wind
Authors: Tandon J. N.
Published: July 2016

Recent observations of large scale coronal structures and solar wind have been studied. The intercorrelation of the two have been qualitatively explained through the focussing of solar-ion streams taking account of the local and general solar magnetic fields. This explains the association of coronal holes with weak, diverging open magnetic field lines and envisages the transfer of hydromagnetic wave energy from nearby active centers to account for the enhanced outflow of solar wind associated with coronal holes.
Properties of Magnetohydrodynamic Turbulence in the Solar Wind
Authors: Dobrowolny M. , Mangeney A. , Veltri P.L.
Published: July 2016

The observations of MHD turbulence in the solar wind indicate that this is in a state characterized, to a good degree by the absence of non linear interactions. It is argued that this is a general property of incompressible MHD turbulence in a magnetized plasma.
The Filament Eruption in the 3B Flare of July 29, 1973: Onset and Magnetic Field Configuration
Authors: Moore R. L. , Labonte B.J.
Published: July 2016

We present direct observational evidence for the preflare magnetic field configuration, the nature of the filament destabilization and triggering of the flare, and the magnetic field configuration after the filament eruption in the large, well-ordered, expanding two-ribbon flare of July 29, 1973.
The False Equilibrium of a Force-Free Magnetic Field
Authors: Low B. C.
Published: July 2016

It has been a customary assumption that any force-free magnetic field represents an equilibrium field in the solar atmosphere under the extreme condition 8πp/B2 ≪ 1. An example of a force-free magnetic field is presented for which this assumption fails in the sense that no equilibrium is possible for the magnetic field if imposed with an arbitrary ambient pressure, however weak the pressure is. A simple mechanism is proposed for the onset of eruption in the course of otherwise quasi-static evolution of magnetic fields in the solar atmosphere.
The Filament Instability in a Sheared Field
Authors: Chiuderi C. , Van Hoven G.
Published: July 2016

Filaments and prominences are classical examples of condensations of nongravitational origin, their formation being due to the thermal instability. The physics of this instability in a uniform plasma at coronal temperatures, which exhibits increasing radiative output as it cools, is well known (Field, 1965). Filaments, however, form in regions of sheared magnetic fields, as evidenced by their location above photospheric polarity-inversion lines and their occurrence after a period of increasing fibril inclination (Tandberg-Hanssen, 1974). Physically, the importance of the field structure is readily understood if one recalls the capability of magnetic field of strongly collimating the local heat conduction. Thus, the preferred locations for the development of the thermal instability will be those where the field configuration inhibits the stabilizing effects of thermal conduction on the growing temperature perturbation.
A Model of Surge
Authors: Noci Giancarlo
Published: July 2016

This paper reports on the application of a siphon flow model to the late stage of a surge observed in the UV radiation by the S055 experiment on board Skylab. The MgX λ625 and OVI λ1032 emissions from the density distributions occurring in flows which become supersonic at the top of the loop agree with the observations, indicating a pressure drop, along the loop, of a factor of 4 for the plasma emitting the OVI line, and of a factor of 2 for the plasma emitting the MgX line.
Propagation of an MHD Shock in the Vicinity of a Magnetic Neutral Sheet
Authors: Mullan D. J. , Steinolfson R. S.
Published: July 2016

The acceleration of solar cosmic rays in association with certain solar flares is known to be highly correlated with the propagation of an MHD shock through the solar corona (Svestka, 1976). The spatial structure of the sources of solar cosmic rays will be determined by those regions of the corona which are accessible to the flare-induced shock. The regions to which the flare shock is permitted to propagate are determined by the large scale magnetic field structure in the corona. McIntosh (1972, 1979) has demonstrated that quiescent filaments form a single continuous feature (a “baseball stitch”) around the surface of the sun. It is known that helmet streamers overlie quiescent filaments (Pneuman, 1975), and these helmet streamers contain large magnetic neutral sheets which are oriented essentially radially. Hence the magnetic field structure in the low solar corona is characterized by a large-scale radial neutral sheet which weaves around the entire sun following the “baseball stitch”. There is therefore a high probability that as a shock propagates away from a flare, it will eventually encounter this large neutral sheet.
Two-Fluid Theory of Interplanetary Shock Waves
Authors: Rosenau P.
Published: July 2016

A 2-fluid time-dependent analytical model of the perturbed solar wind is presented. The expansion of newly emitted material, caused, for instance, by the outburst of a solar flare, is simulated by a spherical piston. For a given thermal conductivity in the limit of strong coupling, one fluid flow in a thermally conducting medium is recovered. A pattern of flow which resembles one-fluid flow in adiabatic medium may be recovered if heat is removed from the perturbed plasma into the propelling plasma. The perturbed flow consists of a thermal precursor which is followed by a shock across which electrons are isothermal while protons are compressed and heated. Finally, we show that the post-shock rise and fall of density cannot be used to distinguish piston-driven waves from blast waves.
Variations of Interplanetary Parameters and Cosmic-Ray Intensities
Authors: Geranios A.
Published: July 2016

Observations of cosmic ray intensity depressions by earth bound neutron monitors and measurements of interplanetary parameter's variations aboard geocentric satellites in the period January 1972-July 1974 are analysed and grouped according to their correlation among them. From this analysis of about 30 cases it came out that the majority of the depressions correlates with the average propagation speed of interplanetary shocks as well as with the amplitude of the interplanetary magnetic field after the eruption of a solar flare. About one fourth of the events correlates with corotating fast solar wind streams. As the recovery time of the shock-related depressions depends strongly on the heliographic longitude of the causitive solar flare, it seems that the cosmic ray modulation region has a corotative-like feature.
Interplanetary Scintillation - Preliminary Observations at 103 MHz
Authors: Alurkar S. K. , Bhonsle R. V.
Published: July 2016

A 3-station interplanetary scintillation (IPS) observatory is being developed mainly with a view to study the solar wind plasma. The first IPS telescope operating at 103 MHz at Thaltej near Ahmedabad has been put into regular operation since April 1979. With only half the antenna aperture (≃2500 m2) presently in use, observations of 8-10 sources are being made to calculate scintillation index, temporal spectrum of intensity fluctuations and scale size of density irregularities.
Magnetically Driven Motions in Solar Corona
Authors: Somov B. V. , Syrovatskii S. I.
Published: July 2016

Solution of the nonlinear MHD problem of plasma flow in an increasing dipolar magnetic field is obtained in the approximation of a strong field. The distributions of plasma velocity, displacement, and density are calculated. The situation when the magnetic dipole is ‘increased’ by rapid process of magnetic reconnection or current sheet rupture is illustrated. Possible applications are discussed in connection with plasma ejections from chromosphere in corona.
The OPEN Program: An Example of the Scientific Rationale for Future Solar-Terrestrial Research Programs
Authors: Williams D. J.
Published: July 2016

The field of solar-terrestrial physics has evolved to a point where quantitative theoretical modeling and cause-effect predictive techniques can be foreseen. Instrumentation now exists to quantitatively test these theories and lead to a significant improvement in our understanding of the solar-terrestrial environment. The proposed Origins of Plasma in the Earth's Neighborhood (OPEN) program will be used to trace this theoretical and experimental evolution and describe a solar-terrestrial research scenario for the 1980's which includes specific problems related to solar and interplanetary dynamics.
Searches for Primeval Galaxies - Past, Present, and Future
Authors: Davis Marc
Published: July 2016

Most models of galactic evolution include a high luminosity epoch of bright star formation at a redshift 2 < Z < 100. Past searches have failed to detect galaxies in their “primeval” state, but recent advances in detector technology will soon enable much improved searches that will very seriously constrain the evolutionary models. Using the CCD detectors on the Space Telescope offers the opportunity for a thousandfold improvement over present search limits. We review here several models of primeval galaxies and comment on their observability in present and future experiments.
A Catalogue of Very Faint Clusters of Galaxies in the Region of the South Galactic Pole
Authors: Vidal N. V.
Published: July 2016

In a search for very distant clusters of galaxies on a redsensitive (6° × 6°) Schmidt plate taken at Siding Spring in the region of the south galactic pole, we found some 49 very faint and compact clusters. We tried to reduce the number of chance configurations, by limiting our survey to (a) very compact and isolated groups of galaxylike images outside crowded regions; (b) some degree of concentration could be observed towards the brightest galaxy; (c) the size of the central object exceeded by several times the seeing disk diameter; (d) a minimum of 15 galaxies could be counted within a circle of ~ 30 arcsec in diameter. The red magnitudes of the brightest galaxies in each clusters are estimated to be fainter than 19.0 magnitudes. From the Hubble diagram for red magnitudes we estimate the redshifts to be about z ≥ 0.5. The integrated red magnitude of the first ranked galaxies in the faintest clusters are about 21.5. Taking into account seeing effects, a more realistic formula for the surface brightness at the centers of galaxies (rather than the [1 + z]−4) is derived. It is shown that, assuming no evolution, the limit of our survey corresponding to the faintest clusters is about z ≥ 1.0. A list of clusters coordinates, magnitudes of the first ranked galaxies and finding charts can be obtained from the author.
Distribution in Depth of Quasars
Authors: Schmidt Maarten , Green Richard F.
Published: July 2016

We discuss the distribution in depth of different kinds of quasars: quasi-stellar radio sources with steep radio spectrum, those with flat radio spectrum, and optically selected quasars. All exhibit an increase of space density with distance to a different degree. The optically selected quasars, in particular, show a steep increase of surface density with magnitude. The steepness of the increase is inconsistent with a uniform distribution of quasars in the local hypothesis. In the cosmological hypothesis the co-moving space density of optically selected quasars increases by a factor of 100,000 to a redshift of 2, and by factors of 1000 and 10 for steep-spectrum and flat-spectrum radio quasars, respectively.
Associations Between QSOs and Groups of Galaxies
Authors: Stockton Alan
Published: July 2016

Evidence that most presently known low-redshift QSOs are associated with groups of galaxies has led to a program aimed at determining the typical properties of these groups. For the 3C273 field, observations of essentially all galaxies with mB ≤ 21.5 over a region 10.1′ (∼1.5 Mpc) in diameter yield four galaxies having redshifts close to that of the QSO. Consideration of the present evidence concerning the richness of groups associated with QSOs leads to the conclusion that, for at least those QSOs that are radio sources, their galactic environment is similar to that of radio galaxies, except that they seldom, if ever, occur in the centers of rich clusters of galaxies.