bluuebunny/crossref_metadata_2025 huggingface dataset:
The Application of Coronal Scattering Measurements to Solar Radio Bursts
Authors: Bradford Henry M.
Published: July 2016

The interpretation of ground based observations of solar “plasma frequency” radio bursts has been hampered in the past by an insufficient knowledge of coronal scattering by density inhomogeneities close to the sun. Calculations based on measurements of the angular broadening of natural radio sources, and Woo's 1975 measurement of the angular broadening of the telemetry carrier of Helios I near occultation (Woo, 1978), indicate that plasma frequency solar bursts should undergo considerable scattering, at least near the maximum of the sunspot cycle. The calculated displacements of the apparent positions of the bursts are about equal to the observed displacements which have been attributed to the bursts occurring in dense streamers. In order to obtain more scattering data close to the sun, interferometer measurements of the angular broadening of spacecraft signals are planned, and the important contribution which could be made with large dishes is discussed.
Current Understanding of the Physics of Type III Solar Radio Bursts
Authors: Papadopoulos K.
Published: July 2016

One of the most exciting plasma physics investigations of the recent years has been connected with the understanding of a new strong turbulent plasma state excited by propagating electron beams. This new state is initiated on the linear level by parametric instabilities (OTS, modulational, etc.) and results in a very dynamic state composed of collective clusters of modes called solitons, cavitons, spikons, etc. Introduction of these concepts to the classic beam plasma interaction problem has rendered quasilinear and weak turbulence theories inapplicable over most of the interesting parameter range, and helped explain many paradoxes connected with the propagation of beams in the laboratory and space. Following a brief review of these non-linear notions, we demonstrate how their application to type III solar radiobursts has revolutionized our understanding of their propagation, radio-emission and scaling properties and has guided the in situ observations towards a more complete understanding. A particular burst (May 16, 1971) is analyzed in detail and compared with numerical predictions.
Quasi-Linear Dynamics of a Hot Maxwellian Electron Distribution Released from a Localized Region in a Homogeneous Plasma
Authors: Grognard R.J.-M.
Published: July 2016

To investigate by numerical analysis the transition towards the asymptotic regime postulated by Ryutov and Sagdeev (1970) in their study of the expansion of a hot electron cloud through a plasma, a physically consistent system of one-dimensional quasi-linear equations has been solved on a Cyber 7600. The results obtained for various conditions of injection were all found in qualitative agreement with the simple analytic description of Ryutov and Sagdeev, in spite of the serious deficiencies of their analysis. Although the aims and techniques of the present study are quite distinct from published numerical works by Takakura and Shibahashi (1976) and Magelssen (1976), all the results point towards the same conclusion: plasmon emission, due to advective instability at the front of the electronic disturbance, is followed by strong reabsorption through a reverse advective process at the rear. In the present note, only the case of a localized hot electronic distribution (initially Maxwellian with Te = 108 K) is considered. The effect of plasmon-plasmon scattering, which can also be included in the programmes, is mentioned in the conclusion.
Origin of Plasma Wave Clumping in Type III Radio Burst Sources
Authors: Smith Dean F.
Published: July 2016

It is hypothesized that the observed clumping of plasma waves in type III sources in the solar wind is due to suppression of the linear stream-plasma interaction by density inhomogeneities of scale size comparable to the characteristic amplification length. Criteria are given for when such suppression should be important. The magnitude and scaling of density inhomogeneities in the 50–200 km range near 0.5 AU is estimated from interplanetary scintillation data. This information is used to construct model sources in which plasma waves are traced and amplified with random inhomogeneities to test the hypothesis. Significant clumping occurs for inhomogeneity scales of 50 and 100 km with inhomogeneity expectation values of 4.8×10−3 and 6.0×10−4, respectively, but not for 200 km scales. Further research is suggested to determine more completely the effects of density inhomogeneities in type III sources. Further details can be found in Smith, D.F., Sime, D. 1979, Astrophys. J., in press.
Observations of Solar Bursts of Types II and III at Kilometric Wavelengths from Voyager
Authors: Riddle A. C. , Boischot A. , Leblanc Y.
Published: July 2016

The Planetary Radio Astronomy receivers aboard the Voyager spacecraft have been recording solar bursts of Types II (Boischot et al. 1930) and III (Riddle 1979) since launch in August and September 1977. The receivers themselves have been described in detail elsewhere (Lang and Peltzer 1977, Warwick et al. 1977). This study restricts itself to data from the 69 channels uniformly spaced between 20.4 and 1326.0 kHz. Each of these channels can be sampled once each six seconds, and the signal to noise ratio on each sample is about 0.8 dB. The sense of circular polarization to which a receiver responds alternates with each sample.
Temporal and Spectral Investigation of Two Thermal Impulsive Microwave and X-ray Bursts of 1972 May 18 for the Determination of Source Parameters
Authors: Wiehl H.J. , Schoechlin W.A.
Published: July 2016

In order to study the dynamical burst process we investigated two bursts of 1972 May 18 at 14:05 UT and at 16:16 UT in the microwave (1–15 GHz, Berne and Sagamore Hill), the hard X-ray (28–102 keV, ESRO TD-1A) and the soft X-ray (0.5–20Å, Solrad 11) frequency ranges. For both flares a thermal interpretation was adopted.
Flare Characteristics and Type III Bursts: A Statistical Approach
Authors: Zanelli C. , Zlobec P. , Koren U.
Published: July 2016

An analysis has been carried of the correlation of the occurrence of type III bursts and flares in spotless regions (G-flares) or covering major sunspot umbrae (Z-flares) - i.e. in magnetic conditions presumably opposite - over the past 10 years. A very low correlation of the former flares (8%) and a higher than average value for the latter flares (36% against the normally accepted 25%) shows that the ambient magnetic field of the flaring region is a primary factor for type III burst emission. The presence of a surge and of a rapid brightness rise (“flash-phase”) are recognized to be other important, if secondary, factors for type III burst generation.
Intrinsic Reddening of Be Stars and its Relation with Hα Emission Intensities
Authors: Divan L. , Doazan V. , Zorec J.
Published: July 2016

The intrinsic reddening and its relation with Hα emission has been determined for 32 Be/Shell stars observed simultaneously at high dispersion at Hα and between λλ3000-and 6200 Å with the Chalonge spectrograph. A trend toward higher reddenings when Hα emission is stronger is observed, together with a large scatter which indicates that for a given emission at Hα, intrinsic reddening can be quite different for different stars.
Polarization in Peculiar Emission-Line Objects
Authors: Barbier R. , Swings J. P.
Published: July 2016

We report on visual polarimetric measurements of B[e] and related stars, and on an unsuccessful search for correlating the observational data with characteristics of the objects or of their surrounding dust shells.
Statistical Properties of Be Stars
Authors: Hubert-Delplace A.M. , Jaschek M. , Hubert H. , Chambon M. Th.
Published: July 2016

The emission features of 140 Be stars described in “An Atlas of Be stars” are briefly reviewed. The time scale of the emission variations are determined for about 35 stars. For several stars we estimated, on the Hβ line, the V/R ratio of the two emission components.
Search for Long-Period Radial Velocity Variations in Some Be Stars
Authors: Pastori L. , Antonello E. , Fracassini M. , Pasinetti L.E.
Published: July 2016

Some astronomers have suggested long period phenomena in the Be stars: Hubert (1971), Delplace and Hubert (1975), Feinstein (1975), Harmanec et al. (1976), Pustylnik (1976). In particular, Fracassini et al. (1977) have made a periodogram analysis of the radial velocities (RV) of the Be star o And from 1900 to 1976, to connect the shell appearance with eventual long-term RV variations. In the present study all the RV of seven Be stars, found in the literature from the beginning of the century up to now, have been assembled and analysed in the same way as o And, in order to find out long period phenomena (duplicity, variability, shell activity, etc…). A brief review on the studied stars may be found in Harmanec et al. (1980).
An Unusually Stable and Short Spectroscopic Period of the Be Star 28 CMa
Authors: Baade D.
Published: July 2016

Spectroscopic (1970: ESO, 12 Å/mm, 6 spectra kindly put at my disposal by Prof. A. Van Hoof; 1976: ESO, 12 Å/mm; 1977: Calar Alto Observatory, 42 Å/mm; 1979: ESO, 12 Å/mm) and photometric (1976: ESO and Cerro Tololo, Hβ, uvby) observations of 28 CMa (B2-3 IV-Ve; 3.52 < mV < 4.18, irregular variations on the time scale of months or years reported; vrot = 80 km/s) revealed a very complex variability. All observed individual types of variations are known from at least a few other Be stars. In 28 CMa, however, for the first time a highly significant correlation between the various variations is established by a stable common period. The period is 1.365 days which seems to be the shortest stable period presently known of any Be star. There is no indication that the star's behaviour changed between 1970 and 1979. Only the equivalent widths of the emission lines increased noticeably.
A Preliminary Report on Simultaneous Ultraviolet and Optical Observations of Lambda Eridani
Authors: Bolton C. T.
Published: July 2016

Radial velocity observations of λ Eridani between 1971 and 1980 and uvbyHα photometry in 1977 show that the star is both a light and velocity variable with a period of 0.701538 d. Copernicus observations in 1977 are compatible with this result. Both the radial velocity and photometric amplitude are variable, and these variations may be correlated with the hydrogen emission line strength. The character and phasing of the light and velocity curves suggest that λ Eridani is a pulsating variable.
Spectroscopic Observations of Be Stars Especially in the Infrared
Authors: Houziaux L. , Andrillat Y.
Published: July 2016

Since the time of I.A.U. Colloquium n° 70, new data have been obtained in the infrared, far less however than in the ultraviolet or in the visible. Few line spectra have been recorded but numerous results have been published in the field of spectrometry of the continuum. It is however neither easy nor very useful to report on the infrared wavelength range alone, and therefore we shall consider when appropriate other spectral regions in this review. After all, the astrophysicist nowadays has the advantage to seek for information in a spectrum which encompasses a fantastic frequency range of about 10 dex, from ν = 108s−1 up to ν = 1018s−1. This means that a contemporary astronomer will have to become familiar with a somewhat larger span of phenomena than with the rather narrow one he has been accustomed to for the last 40 or 50 years.
A Preliminary Digital Analysis of the Spectrum of β Lyrae
Authors: Eugenio E. , Mendoza V.
Published: July 2016

This paper describes preliminary results from a digital analysis of the Fourier transform spectroscopy of β Lyrae. The spectra are photometrically precise in the 4800–10200 Å range with a spectral resolution of 3.85/cm. The most remarkable spectral features are the emission strength of some neutral Helium and Hydrogen lines, and their vari ability with time. Other fainter emission lines disappear, now and then.
A Catalogue of Be Stars
Authors: Jaschek M. , Egret D.
Published: July 2016

We are presently undertaking, at the Stellar Data Center, a large effort to produce the Catalogue of Stellar Groups, which is a catalogue listing all the kinds of stars with spectral peculiarities existing up to now. The work is in progress and presently about fifty groups (Ap, Am, Be, WR, H and K emission line stars, etc.) are defined, gathering more than 25000 stars. The catalogue was started with the aim to set up lists defined by homogeneous criteria, because up to now the available information is scattered through the literature. We hope that the catalogue will be useful for formulating observing programs and for further detailed research on each of the groups.
The Evolution of Rapidly Rotating B/Be Stars
Authors: Endal A. S.
Published: July 2016

Rotation can significantly change the moment-of-inertia of a main sequence star. As a result, the ZAMS rotation rate need only be within ~30% of the critical value in order to reach critical rotation during the hydrogen burning stage. Calculations of the evolution of rotating stars show that the Be stars result from a normal (Maxwellian) distribution of B-star rotation velocities.
Be Stars as Interacting Binaries
Authors: Peters Geraldine J.
Published: July 2016

At the last IAU Symposium on Be stars held in Bass River, MA in 1975, several of us (including P. Harmanec, M. Plavec, R.S. Polidan, and myself) suggested that Be stars are mass transfer binaries and represent the higher mass counterparts to the familiar Algol systems. Although a number of alternatives to the rotational hypothesis have been presented at this symposium (including “chromospheric” activity and non-radial pulsation) and some of these may well explain certain objects, I strongly believe that binary mass transfer is responsible (either directly or indirectly) for the circumstellar envelopes observed in a large percentage of Be stars.
Ultraviolet Observations, Stellar Winds, and Mass Loss for Be Stars
Authors: Marlborough J. M.
Published: July 2016

Although the first ultraviolet (UV) observation of an astronomical source was obtained in 1946, the first UV observations of Be stars were not obtained until 1964. In this review of UV data covering the period since 1964, the term Be star will be assumed to include Oe stars as well (Frost and Conti, 1976). An earlier review of this subject is by Heap (1976).
The Problem of X Persei
Authors: Viotti R. , Ferrari-Toniolo M. , Giangrande A. , Persi P. , Baratta G. B.
Published: July 2016

X Per is a variable emission line star which shows among other peculiarities a weak X-ray emission (4U 0352+30) and a strongly variable IR excess (Ferrari-Toniolo et al. 1978, Viotti et al. 1980). In the past decade the star has undergone three phases of enhanched “activity” (1972–73, 1978 and 1980) characterized by brighter visual luminosity, excess in the Balmer continuum and in the IR, stronger X-ray emission, with intermediate periods of minimum activity (1974–77, 1979) when the optical-infrared energy distribution was closer to that of a normally reddened early type star (figure 2). But during most of its history the energy distribution largely deviated from that of a non-emission line early type star, and the first problem is to determine the interstellar extinction, disregarding any “local” effect. The strength of the 2200 A band in the UV spectrum of X Per is consistent with E(B-V)=0.35, a value close to the extinction towards other Per II stars: Per (0.34), o Per (0.31), Per (0.32, Viotti & Lamers 1975). The i.s. Ly∝ line observed in the high resolution IUE spectrum of X Per obtained on 1979, December 23, has a FWHM of 11.0 A corresponding to N(HI)=4.9 1020 cm−2. The Copernicus observation of H2 lines (of not good quality) gives N(H2)≅1.1 1021 (Mason et al. 1976). A much lower value of 3–5 1020was derived by Snow (1976, 1977) for o and Per. Taking for X Per N(H2)≅5 1020we have N(H total)≅1.5 1021, yielding to N(H)/E(B-V)=4.3 1021 cm−2/mag in agreement with Bohlin law (1975).
An Overview of the Globular Cluster System of the Galaxy
Authors: Zinn Robert
Published: July 2016

Harlow Shapley (1918) used the positions of globular clusters in space to determine the dimensions of our Galaxy. His conclusion that the Sun does not lie near the center of the Galaxy is widely recognized as one of the most important astronomical discoveries of this century. Nearly as important, but much less publicized, was his realization that, unlike stars, open clusters, HII regions and planetary nebulae, globular clusters are not concentrated near the plane of the Milky Way. His data showed that the globular clusters are distributed over very large distances from the galactic plane and the galactic center. Ever since this discovery that the Galaxy has a vast halo containing globular clusters, it has been clear that these clusters are key objects for probing the evolution of the Galaxy. Later work, which showed that globular clusters are very old and, on average, very metal poor, underscored their importance. In the spirit of this research, which started with Shapley's, this review discusses the characteristics of the globular cluster system that have the most bearing on the evolution of the Galaxy.
Globular Clusters and Field Halo Stars
Authors: Carney Bruce W.
Published: July 2016

Recent work on the chemistry and kinematics of the field halo population stars is reviewed, including the metallicity distribution function, elemental abundance patterns, primordial abundances, and their relations with stellar kinematics. The important role played by these stars in determining the ages of the globular clusters is discussed. A comparison is made between the kinematic and chemical properties of the field and cluster stars to ascertain if they share a common history.
Intermediate-Age Magellanic Cloud Globular Clusters
Authors: Olszewski Edward W.
Published: July 2016

In this paper, I discuss some of the new facts that have been learned about Magellanic Cloud clusters, mostly thanks to new detectors and associated reduction code. I first show the extent of the LMC cluster system, in order to note that studies of age, abundance, and kinematics of the cluster system have been missing clusters to the north and south of the Hodge and Wright atlas, and to point out that star formation has gone on in places far from present day neutral hydrogen. I will concentrate on the intermediate age clusters (108-1010 y) in the discussion concerning new stellar evolution results, neglecting the 107 y clusters and 30 Doradus. I further restrict my choice of topics to 1) the luminosity of clump giants, 2) the youngest possible RR Lyrae stars, and 3) the patterns and history of cluster formation. The discussion of abundances of Cloud clusters leads readers to the excellent poster papers presented at this meeting.
The NGC 5128 Cluster System
Authors: Harris Hugh C. , Harris Gretchen L. H. , Hesser James E.
Published: July 2016

We review what has been learned about the globular clusters in NGC 5128 (Cen A). Two independent programs (our work at CTIO and Sharples” work at the AAT) have confirmed 87 objects as clusters in NGC 5128 from their velocities. We discuss the colors of the clusters, which are indicative of a wide range of metallicities, their velocities, and their origin as genuine globular clusters in this elliptical galaxy.
The M 87 Globular Cluster System∗
Authors: Huchra John
Published: July 2016

We review early and recent photometric studies of the M87 globular cluster system. We also describe recent high quality spectroscopic studies that have been used both to measure the metallicities of M87 globular clusters and to determine the mass of M87's halo.
Tidal Heating of Globular Clusters
Authors: Chernoff David F. , Shapiro Stuart L.
Published: July 2016

The influence of tidal heating on the evolution of globular clusters (GC's) in circular orbits about the Galactic center is studied. Giant Molecular Clouds (GMC's) stretch a globular cluster in a direction transverse to its orbit through the disk. The variation in acceleration with height in the disk compresses the cluster in a longititudinal direction. Numerical and analytic calculations of heating and mass loss for GC's, represented by King models, show that disk heating dominates. We apply the results to calculate GC evolution prior to core collapse or tidal disruption using a three parameter (energy, mass, and tidal radius) sequence of King models. The changes in the parameters are calculated for tidal perturbations, relaxation and evaporation. Clusters close to the Galactic center (less than 3 kpc) undergo core collapse in a Hubble time. The effect of tidal perturbations on energy and mass loss of the cluster is strongest between 3 and 5 kpc where it can substantially effect the evolution of the cluster. Here, depending upon their initial concentration, clusters are either tidally heated and dissolved, or forced towards a gravothermal catastrophe in times that are a fraction of a Hubble time. These inner regions of the Galaxy should be fertile territory for the search for post-collapsed clusters.
X-Ray Binaries in Globular Clusters
Authors: Grindlay Jonathan E.
Published: July 2016

X-ray binaries in globular clusters provide a powerful tool for the exploration of the evolution of compact binaries and their host globular clusters. Recent x-ray and optical studies of these systems have yielded long-sought binary periods and fundamental properties for two sources (in NGC 6624 and M 15). It appears that tidal capture formation of compact binaries in globular clusters can proceed by several different routes and lead to exotic systems such as the white dwarf-neutron star binary with an 11-minute period recently discovered in NGC 6624. Combined with previously reported long-term periods for several globular cluster (and field) x-ray sources, this suggests again that many of these systems may in fact be hierarchical triple systems. The prospects for forming these in the dense cores of clusters undergoing core collapse is discussed, and searches for color gradients in the cores of globular clusters showing cusps in their central surface brightness distribution are presented. A program to test for the high central density of binaries (and triples) expected in cusp clusters by searching for diffuse line emission from their constituent cataclysmic variables is briefly described. Finally, the case for globular cluster disruption and the formation of galactic x-ray burst source is reviewed in light of recent developments.
Stellar Evolution in Globular Clusters and HST
Authors: Renzini Alvio
Published: July 2016

Globular clusters (GC) have been regarded among the most obvious targets for the Hubble Space Telescope since the very first conception of this project, and some observational programs have been exemplified in publications concerning the future use of HST (e.g. Westphal 1982 and Macchetto 1982, in the “Patras Book”, Bahcall 1985, see also the 1985 Report of the STScI working group on Stars and Star Clusters).
Simulations of HST Observations of Globular Clusters
Authors: Bahcall John N. , Schneider Donald P.
Published: July 2016

The high angular resolution of the Hubble Space Telescope will provide opportunities for many fundamental observations of globular clusters, most of which have been extensively discussed in the literature. We have therefore chosen to devote our time (and pages) to a presentation of what HST observations may reveal about some aspects of galactic globular clusters. To avoid infringing upon programs that others may propose, we have limited ourselves to simulations of observations that are part of our Guaranteed Time Observations. [The complete catalog of GTO observations has published by the Space Telescope Science Institute and is available upon request.]
A New Survey of Globular Cluster Structural and Luminosity Parameters
Authors: Reed B. Cameron , Peterson Charles J.
Published: July 2016

We have made an analysis of the visual photometric data contained in the Catalogue of Concentric Aperture UBVRI Photoelectric Photometry of Globular Clusters (Peterson 1986). Structural parameters have been obtained by use of the Simplex algorithm of Caceci and Cacheris (1984) to fit the model curves of King (1966) to the run of cluster luminosity with radius. We find that concentric aperture photometry alone can be used to determine globular cluster core radii and central surface brigtnesses reliably. Application of this techique, however, is limited to about two-thirds of the known clusters of the Galaxy because no or inadequate numbers of photometric measurements exist for the remaining clusters. Accurate determination of cluster concentration classes still requires use of other types of data, such as star counts.
On the Bimodal Distributions of Horizontal Branches
Authors: Lee Young-Wook , Demarque Pierre , Zinn Robert
Published: July 2016

New synthetic horizontal branch (HB) models are presented for some globular clusters known to have bimodal HB distributions. These models are based on new Yale HB evolutionary tracks for Y=0.25 and the core masses appropriate for the compositions. The distribution of stellar masses along the HB is given by a slightly modified version of Rood's (1973) function. Figure 1 compares the synthetic and the observed color-magnitude diagrams and the generalized histograms of the distribution of HB stars over (B-V)o (observational data from Alcaino & Liller 1984, Buonanno et al. 1981, Stetson 1981, and Menzies 1974 for clusters M4, M5, N1851, and N6723 respectively). Following Norris (1981), we have used the period-luminosity-color relations to estimate the colors of some RR Lyrae variables. Since none of the parameters in the models has a bimodal distribution, the excellent agreement between the color distributions of the models and the observations suggests that the observed bimodal distributions are a consequence of the evolution from the zero-age HB. Contrary to the suggestion of Norris (1981) and Smith & Norris (1983), there is no need to connect the bimodality of the HB with the observed bimodal CN distributions of the red giants in some of these clusters. The clusters in Figure 1 span a narrow range in metallicity ([Fe/H]=-1.40 to −1.09; Zinn 1985), and we are investigating other, less well observed, clusters in this range (e.g., N2808) to see if their bimodal HB distributions also have simple explanations.
Horizontal-Branch Stars by Strong HE Lines
Authors: Crocker Deborah A. , Rood Robert T.
Published: July 2016

We discuss observations of He lines at λ 4026 å in two stars in NGC 6752 and three in M 92. M 92 and NGC 6752 are moderate to extreme second parameter clusters. The presence of He lines in stars where diffusion should deplete atmospheric helium may be a clue to the identity of the second parameter. One such candidate which could easily inhibit diffusion is rotation.
Globular Clusters in the Vilnius Photometric System
Authors: Zdanavičius K.
Published: July 2016

The Vilnius photometric system was developed for photometric two-dimensional classification of stars and for the determination of interstellar reddening. The system consists of seven magnitudes U, P, X, Y, Z, V and S with mean wavelengths of 345, 375, 405, 466, 516, 544 and 655 nm and half-widths of the order 20 – 30 nm (Straižys 1977). Later on the system was successfully used for the determination of temperatures and the metallicities of halo stars (Bartkevičius and Sperauskas 1983).
A Search for Obscured Globular Clusters
Authors: Djorgovski S.
Published: July 2016

It has been estimated that up to several tens of globular clusters in our Galaxy remain undiscovered, because they are hidden by the dust. Most of those clusters are expected to be in the bulge area, but some may be anywhere in the galactic plane. This search is based on the use of IRAS catalogs as candidate lists for the obscured globular clusters. It was found that the properties of detected known clusters are sufficiently distinct for a meaningful sifting through the PSC. A sequence of statistical “filters”, described below, was applied on the PSC, until a couple of hundred most promising candidates were found in the bulge.
A Complete Sample of Globular Clusters in NGC 5128
Authors: Sharples Ray
Published: July 2016

We present the results of an unbiased survey to search for globular clusters around the nearby elliptical galaxy NGC 5128. A total of 44 clusters has been identified on the basis of radial velocities alone. The cluster system appears to be flattened towards the major axis of the galaxy but does not show any dynamically significant rotation. There is a deficit of clusters in the core when compared with the power law density profile seen at large radii.
The Blue Star Clusters of M 31
Authors: Hodge Paul
Published: July 2016

CCD images in UBVR of 33 star clusters in the disk of M31 show them to be mainly bright and very young. Few cataloged clusters in the disk are likely to be as old as 109 years.
Photometric Models for Globular Clusters from Population Synthesis
Authors: Dolcetta R. Capuzzo
Published: July 2016

Integral fluxes (Bolometric and U, B, V) are computed in a completely theoretical frame in order to investigate the structural properties and stellar content of coeval stellar systems of various ages and metal abundance. Some results concerning the problem of the color gap in the distribution of the sample of Magellanic Cloud clusters are discussed.
Do Binary Clusters Exist in the Large Magellanic Cloud?
Authors: Hatzidimitriou D. , Bhatia R. K.
Published: July 2016

The possible existence of binary clusters in our Galaxy (h and x Persei, Ocl 556) has been argued in the past, but it has never been a well established fact either in our Galaxy, or in external systems. An early speculation on the problem by Innanen et al (1972) has predicted a considerable degree of stability for binary clusters in low nuclear density galaxies, like the LMC.
The Distances to RR Lyrae Variables
Authors: Jones Rodney V. , Carney Bruce W. , Latham David W. , Kurucz Robert L.
Published: July 2016

Of all the different methods employed to estimate the mean absolute magnitude of RR Lyrae variables, only an analysis of the Baade-Wesselink type can determine this quantity directly. The distance to a globular cluster can therefore be measured by determining RR for that cluster instead of being forced to assume that RR is the same as that of the nearby field variables. This is important in that the field stars may have a different luminosity than cluster variables. In addition, since RR should depend on the composition (especially helium) and history of mass loss of these stars, this quantity may vary from cluster to cluster.
Globular Clusters Detected in the Coma Cluster's Central Giant Galaxy NGC 4874
Authors: Thompson Laird A. , Valdes F.
Published: July 2016

We have used the Canada-France-Hawaii Telescope on Mauna Kea to obtain two deep CCD exposures in the central region of the Coma cluster, and we have used the new images to detect globular clusters in the central giant galaxy NGC 4874. One exposure with a total integration time of 2 hours lies in the halo of the giant galaxy. A second (comparison) exposure of the same integration time was taken within the cluster core but well away from any other bright galaxy. Our analysis, which includes both photometry and image classification with the automated routines called FOCAS, extends to a limiting B magnitude of 26.25. Image classification is a necessary part of this study because at the faintest limiting magnitudes globular clusters are easily confused with the rich population of faint background galaxies. We have been particularly successful in sorting stellar objects from galaxies because the image quality on our images is quite good: FWHM ~ 0.6 arcsec. The data were taken with the fast autoguiding instrument called ISIS (Thompson and Ryerson 1984)
Globular Clusters in Lenticular Galaxies: NGC 3115
Authors: Held E. V. , Capaccioli M.
Published: July 2016

We present a progress report for the ongoing study of the globular cluster (GC) system around the edge-on lenticular galaxy NGC 3115. This object is one of the best targets for this kind of investigation, due to its proximity (~ 10 Mpc) and favourable inclination (for a deep photometric study and a review of the properties of NGC 3115, see Capaccioli et al., 1986). Previously published data include a preliminary luminosity function of GC candidates, based on indirect calibration of KPNO photographs (Strom et al., 1977), and visual star counts on CFH and AAT deep plates (Hanes and Harris, 1986). Here we report on B-band photometry down to mB ~ 24, based on CCD calibration.
An Automated HR Diagram for NGC 6809 (M 55)
Authors: Irwin Michael J. , Trimble Virginia
Published: July 2016

For decades, star counts and HR diagrams extending below the main sequence turnoff in globular clusters meant the work of Sandage (1957). The advent of large CCD's at the foci of large telescopes has changed this (McClure et al. 1985, Harris & Hesser 1985, Christian & Heasley 1986, Heasley et al. 1986, Penny & Dickens 1986, Richer & Fahlman 1986, Smith et al. 1986) and made clear that clusters differ in the shapes of their luminosity functions and in the morphology of their HR diagrams. We return here to photographic methods, which can capture an order of magnitude more images and so possibly reveal new details.
The Dynamics of Globular Clusters in High Eccentricity Orbits
Authors: Bhatia R. K.
Published: July 2016

The aim of the present work is two-fold: 1) To study the effect of the tidal field of the Galactic bulge on a cluster in a high eccentricity plunging orbit with half-mass density nearly equal to the Roche density; 2) To estimate the tidal or limiting radius for such orbits.
The Spatial Distribution of Spectroscopic Binaries and Blue Stragglers in M 67
Authors: Mathieu Robert D. , Latham David W.
Published: July 2016

Mathieu et al. (1986) have completed an extensive radial-velocity survey of over 100 late-type stars in M 67 with V < 12.8. The spatial distributions of the spectroscopic binaries and single stars (i.e. those stars without detected radial-velocity variation; many of these are undoubtedly binaries, albeit with lower secondary masses) are shown in Fig. 1. The distribution of the binaries is notably more centrally concentrated than the single stars. The two observed distributions derive from distinct parent distributions at the 98% confidence level. The projected half-mass radius of the binaries is 0.9 pc; the half-mass radius of the single stars is 2.4 pc. Indeed, 77% of the binaries lie within the single-star half-mass radius.
Kirkwood Gaps and Resonant Groups
Authors: Ferraz-Mello Sylvio
Published: July 2016

This paper is a short review of the dynamics of the asteroidal resonances as currently determined from maps and simulations over 106 – 107 years. The main recent results concern the extensive exploration of the phase space to determine domains of initial conditions leading to close approaches to the inner planets, the topological dynamics of the planar Sun-Jupiter-asteroid problem at very high eccentricities and the differences amongst 2/1 and 3/2 resonances able to explain the existence of a gap in the asteroidal belt at the 2/1 resonance and of a group of asteroids in the 3/2 resonance. Current results point to a confirmation of Wisdom's theory for the formation of the gaps by gravitational evolution and scattering by the inner planets.
The Galileo Encounters with Gaspra and IDA
Authors: Chapman Clark R.
Published: July 2016

The Galileo spacecraft encounters with 951 Gaspra and 243 Ida have provided the first close-up pictures and measurements of asteroids. These two small, S-type asteroids are both irregular in shape, confirming generalized pre-encounter interpretations from groundbased data. Gaspra is lightly cratered by small, fresh craters whereas Ida's surface is heavily covered by craters of all sizes and in all stages of degradation. Unless there are major differences in strength between these two bodies, Ida may be about 10 times older than Gaspra – approaching the age of the solar system. Both asteroids have grooves, although not as prominent as on Phobos. Ida has a population of boulders, particularly near its ends. While Ida seems to have a deep regolith, Gaspra is more nearly in a state of erosion, although there is evidence for an older megaregolith. The data are thus far not conclusive about the geophysical properties of these objects (e.g. whether they are rubble piles) and there are as yet no firm conclusions about how asteroid families are produced by catastrophic collisions. Interesting spectral data relevant to the S-type asteroid controversy (e.g. spatial variations on Gaspra) may lead to some useful generalizations after the remaining Ida data are returned and analyzed in spring 1994. Unexpected magnetic anomalies observed in the vicinities of both asteroids are being studied.
The Rosetta Mission to Primitive Bodies of the Solar System
Authors: Langevin Yves
Published: July 2016

The European Space Agency (ESA) has selected Rosetta as the next cornerstone mission, to be launched in 2003. The goal is to perfom one or more fly-bys to main belt asteroids, followed by a rendez-vous with an active comet. Advanced in situ analysis, both in the coma and on the surfaces of the nucleus, will be possible, as well as monitoring by remote sensing instruments of the nucleus and of the inner coma for a time span of more than one year, until perihelion. This paper outlines the scientific and technological choices done in the definition of the mission.
Asteroid Families
Authors: Zappalà Vincenzo , Cellino Alberto
Published: July 2016

In spite of their widely recognized importance in the framework of the modern understanding of the asteroidal population and its collisional evolution, asteroid dynamical families have long been a puzzling subject of research, due to the disagreement among the family lists published by different authors. In the present review, the definition and meaning of asteroid families are critically discussed, as well as the various problems which have to be faced by any suitable technique of family identification. In this respect, major improvements have been achieved during the last few years. The most recent family searches show an excellent agreement both in the number of reliably identified families, and in their members. Moreover, the overall performances of the most recent techniques of family identification have been tested by means of numerical simulations, with encouraging results. For these reasons, we believe that we are presently at the beginning of an era in which detailed physical studies of families can be attempted, and observational campaigns can be planned on the basis of solid evidence, like in the case of the recent spectacular results obtained for the family associated to the large asteroid 4 Vesta.
A Composite Catalogue of Asteroid Proper Elements
Authors: Milani Andrea , Bowell Edward , Knežević Zoran , Lemaitre Anne , Morbidelli Alessandro , Muinonen Karri
Published: July 2016

We have assembled the asteroid proper elements computed by different authors, using different methods, and for different regions of the asteroid belt. Asteroids on planet crossing orbits are not yet included. The use of very different algorithms is dictated by the dynamics of the different regions. For the asteroids of the main belt, having semimajor axes between 2.1 and 3.8 AU, and with proper eccentricity and sine of inclination less than 0.3, proper elements are computed by a fully analytical iterative theory developed by Milani and Knežević (1990,1992,1994; hereafter M&K). For high inclination and/or eccentricity main-belt asteroids, having 1.8 < a < 3.8 AU and either e or sin I larger than 0.24, proper elements are computed by a semianalytical theory developed by Lemaitre and Morbidelli (1994; hereafter L&M). For Trojans, proper elements are computed by a synthetic theory (that is, from the output of a numerical integration for a few Myr) by Milani (1993). For the Hilda asteroids in the 3: 2 resonance, proper elements have been computed by a synthetic theory by Schubart (1982, 1991). For a discussion of the state of the art in the computation of proper elements, see Knežević and Milani, this volume; for Trojans, see Milani, this volume; for some other cases (e.g. proper elements for resonant asteroids), see Froeschlé and Morbidelli, this volume. When and if new proper elements will be available for other asteroids, they will be added to the public domain file, together with updates and upgrades of the existing catalogues.
2. 21-cm. observations in Sydney
Authors: Carpenter Martha Stahr
Published: July 2016

The primary project in the current 21-cm. hydrogen-line work in Sydney is a study of the southern Milky Way by F. J. Kerr, J. V. Hindman, and the author. Earlier observations* made at the Radiophysics Laboratory during 1954 yielded a tentative picture of spiral structure in the southern portion of the conventional galactic plane. That picture, slightly modified by more recent results, is shown in Fig. 1.
11. 21-cm. meridian plane surveys
Authors: Tatel H. E.
Published: July 2016

The meridianal surveys [1] at 21-cm. of interstellar hydrogen gas have been continued. Surveys at galactic longitudes of 50° [1], 60° [2], 80° [2], 90° [1], 110° and 200° have been completed while partial surveys have been made at longitudes of 20°, 205°, and 210°.
15. Detection of the spectral line of deuterium from the centre of the Galaxy on the wave-length of 91·6 cm.
Authors: Getmanzev G. G. , Stankevitch K. S. , Troitzky V. S.
Published: July 2016

As was shown by I. S. Shklovsky, a radio spectral line from interstellar deuterium on λD = 91·6 cm. (fD = 327·38424 Mc./s.) may be expected [1]. According to Shklovsky the difference between the effective temperature Teff in this line and outside it must be of the order of 1/500 Teff in the direction of the galactic centre, if the concentration of deuterium equals 10−3 that of hydrogen. In this case, contrary to the emission by hydrogen, an absorption line is expected. As Teff equals about 300° the depth should be of the order of 0·6°.
16. Microwave and radio-frequency resonance lines of interest to radio astronomy
Authors: Townes C. H.
Published: July 2016

A review of microwave and radio-frequency spectral lines which might possibly be detected by the techniques of radio astronomy is attempted here. Brief discussions of this type have already been given by several authors [1, 2, 3, 4]. However, the present treatment is somewhat more complete than previously published material, and has the advantage of more recent information about certain transition frequencies. It includes a general discussion of types of spectra which might be found, expected intensities, and some characteristics and known frequencies of the lines which may be of interest in radio astronomy.
37. Galactic radio emission and the distribution of discrete sources: Introductory Lecture
Authors: Brown R. Hanbury
Published: July 2016

At wave-lengths greater than about 1 metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form:
where TA is the equivalent black-body temperature of a region of sky and λ is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore, the value of TA is about 1050K. at 15 metres and thus greatly exceeds the electron temperature expected in H 11 regions.

At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 to 10 metres where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.
52. Brightness distribution of the sun at 1·45 metres
Authors: Firor J.
Published: July 2016

The brightness distribution of the quiet sun at radio frequencies is of importance in determining the electron density and temperature in the chromosphere and the corona. Calculations made by Smerd, based on parameters derived from optical observations of the sun, indicate that the brightness distributions for wave-lengths near 1·5 metres are sensitive to the assumed coronal conditions and hence are well suited to checking these parameters.
55. Radio observations of the eclipse of 30 June 1954
Authors: Laffineur M.
Published: July 2016

The laboratory of radio astronomy of the Institut d'Astrophysique at Paris has observed the eclipse of 30 June 1954 at öland (Sweden) and at Meudon (France) [1].
63. The enhanced radiation from sunspot-regions
Authors: Waldmeier M.
Published: July 2016

The so-called enhanced radiation appears at all frequencies in connexion with sunspot-regions. For λ < 25 cm. it may be interpreted satisfactorily as thermal radiation of the coronal condensations (Waldmeier, 1955) [1]. For λ > 50 cm. the mechanism responsible for the production of this emission is still unknown. The enhanced radiation from 62 to 200 Mc./s. shows a strong concentration in the radial direction and, therefore, becomes observable only when the source of radiation is close to the centre of the sun's disk. For sin θ = 0·3, i.e. at an angular distance of θ = 17° from the centre of the solar disk, the intensity has dropped to 50 % of that for θ = 0° and for sin θ = 0·5 to about 25 %. For sin θ = 0·8 the radiation intensity is certainly < 10%. This property has recently been investigated again by Machin and O'Brien (1954) [2] as well as by H. Müller[3], using the entire material of the years 1947–53 published in the Quarterly Bulletin on Solar Activity. According to Müller the limb darkening is very similar for the frequencies 62 to 200 Mc./s., the radiation intensity having decreased at sin θ = 0·29 to half of its value for sin θ = 0. A diminution to 10% may be found for 62 Mc./s. at sin θ = 0·54, for 80 Mc./s. at sin θ = 0·59, for 98 Mc./s. at sin θ = 0·62, for 175 Mc./s. at sin θ = 0·72 and for 200 Mc./s. at sin θ = 0·77. For 600 and 1200 Mc./s. the limb darkening is much weaker, the intensity decreasing to 50% at sin θ = 0·57 and 0·75 respectively.
64. On the origin of solar radio noise
Authors: Menzel D. H. , Krook M.
Published: July 2016

The radio-frequency emission observed in solar bursts cannot reasonably be interpreted as thermal radiation. Its origin is to be sought for rather in terms of co-operative behaviour of systems of charged particles. In any case, we cannot avoid having to examine the physical consequences that arise from such co-operative behaviour.
66. Remarks on the energy of the nonthermal radio-frequency emission
Authors: Biermann L. , Lüst R.
Published: July 2016

It is proposed to discuss the role of the radio-frequency emission in the whole set of the non-thermal emissions of the sun, which originate in the solar corona and the uppermost regions of the chromosphere. Of these, the radiative emissions give probably an amount of between 104and 105ergs/cm.2sec., to which the radio-frequency region contributes only very little (even during an intense outburst, when the total radiative emission is much larger, not more than 10°–102ergs/cm.2sec.); the contribution of the lower chromosphere, however, is not yet well known. The corpuscular emissions under normal conditions seem to require ≈ 105ergs/cm.2sec. (but again much more in active, e.g. ‘M’, regions), and to constitute a normal feature of the outer solar corona. These emissions, we propose, are maintained by the same supply of mechanical energy which secures the thermal and radiative equilibrium of the inner corona. That is to say, some part of the flux of acoustic energy originating in the hydrogen convection zone and, according to this theory, heating the upper chromosphere and the inner corona, is believed always to reach the outer corona, where the radiative loss is smaller, and this part is then at least comparable with that dissipated in the inner corona.*