bluuebunny/crossref_metadata_2025 huggingface dataset:
The Abundance of the LMC Globular Cluster NGC 2213
Authors: Geisler Doug
Published: July 2016

A new technique for determining accurate abundances in distant giants - Washington CCD photometry - has been applied to the intermediate-age LMC globular cluster NGC 2213. An abundance of −0.40 ± 0.15 was found from the analysis of 42 giants with V < 20, using data obtained with the 1.5 m telescope. Combined with published main-sequence photometry, the derived abundance indicates a true LMC distance modulus of 18.2 ± 0.2. A likely CN strong giant near the tip of the giant branch is identified. Abundances are also derived for a sample of 27 field giants. Results indicate that one could determine both the age and abundance of Magellanic Cloud clusters with high accuracy from Washington photometry using the 4 m in less than one hour of observing time per cluster.
Short-Period Variables in Globular Clusters of Moderate Metallicity
Authors: Hazen Martha L.
Published: July 2016

Three Galactic globular clusters of moderate metallicity, (−0.7 > [Fe/H] > −0.9), have been searched for variable stars. NGC 6388 and NGC 6569 appear to contain RR Lyrae variables as members; NGC 6652 does not. NGC 6388 and NGC 6569 thus appear to have bluer horizontal branches than normally found at their metallicity.
The Structure of Collapsed Cluster Cores
Authors: Lugger Phyllis M. , Cohn Haldan , Grindlay Jonathan E. , Bailyn Charles D. , Hertz Paul
Published: July 2016

In order to test the prediction that many Galactic globular clusters have undergone core collapse (Lightman 1982, Cohn and Hut 1984) and should therefore have central surface brightness cusps, we have obtained UBVR CCD frames of the cores of 72 clusters. We present and analyze U-band surface brightness profiles for three clusters: one “control cluster” with a normal flat core profile — NGC 6388 — and two with central power law cusps — NGC 6624 and M15 (NGC 7078).
Evolution of Globular Clusters by Tidally-Captured Binaries through Core Collapse
Authors: Statler Thomas S. , Ostriker Jeremiah P. , Cohn Haldan N.
Published: July 2016

We present calculations of globular cluster evolution performed by a modified Fokker-Planck approach, in which binaries formed by tidal capture are followed explicitly, along with subsequent heating mechanisms. The cluster is simulated by a two component model, using the cross sections of Press and Teukolsky (1977) for tidal capture, those of Hut (1984) for the single-binary encounters and for distant binary-binary encounters, and those of Mikkola (1983) for the strong binary-binary encounters. The initial state of the cluster is a Plummer model with N = 3 × 105 and scale radius ro = 1.13 pc. All stars are identical, with mass M∗ = 0.7M⊙ and R∗ = 0.57R⊙. This gives an initial core radius rc = 0.8 pc, and one-dimensional dispersion σ = 11.6 km s-1. All binaries are assumed to be identical, with separation a = 2.5R∗. There are no binaries in the cluster initially. Additional important effects, such as tidal truncation, tidal shocks, stellar evolution and mass loss, and stellar mergers, are not included.
Origin and Radial Distribution of Faint Blue Horizontal-Branch Stars
Authors: Bailyn Charles D. , Grindlay Jonathan E. , Cohn Haldan , Lugger Phyllis M.
Published: July 2016

We report the identification of 23 faint blue horizontal branch stars in Omega Centauri similar to those discussed by Buonanno et al. (1985) in M15. We find that these stars are significantly concentrated towards the center of the cluster with respect to other giants. We suggest that they may have formed from the collision of a main sequence star and a white dwarf.
Linear Density Waves in Globular Clusters
Authors: Sobouti Yousef
Published: July 2016

It is often maintained that Antonov's equation, a linearization of the collisionless Liouville-Boltzmann equation, governs small perturbations of a stellar system. The variational integrals resulting from Antonov's equation are in six dimensional phase space. However, expanding the perturbations in the velocity coordinates and carrying out the integrals over the velocity components gives integrals in the three dimensional configuration space. Solutions in successive approximations lead to standing density waves. The first order equations involve a vector field ξ(x) related to but not identical with the Lagrangian displacements of a volume element of the system. In this respect the problem is analogous to the linear oscillations of a fluid star. The analogy is exploited to provide a classification for the modes of oscillation and to obtain suitable data for variational calculations. The normal modes appear to be trispectral, in the sense that the associated vector field ξ(x) is derived predominantly either from a scalar potential, a toroidal vector potential, or a poloidal vector potential. The eigenfrequencies of the radial (ι = 0) and non-radial (ι = 1) modes are calculated. The associated density waves are analyzed.
Cooling and Fragmentation of Proto-Clobular Cluster Clouds
Authors: Palla Francesco , Zinnecker Hans
Published: July 2016

Recently, Fall and Rees (1985) have proposed a theory for the origin of globular clusters forming from the largely primordial gas in the protogalaxy. These authors have explained the typical masses of proto-globular cluster clouds (~ 106 M⊙) as gravitationally unstable condensations at temperature T ~ 104 in a hot protogalactic medium (T ~ 106 K) but they were not concerned with how these clouds would fragment into stellar masses (~ 1 M⊙). In fact, their proto-globular cluster clouds are trapped at T ~ 104 K, and cannot cool to lower temperatures. However, substantial cooling must occur if these clouds are to form solar mass stars. It is known that under primordial conditions the only available cooling agent is molecular hydrogen, formed in the gas phase. Therefore, if sufficient molecular hydrogen is formed, it is possible to cool the gas well below T ~ 104 K. In the following we outline how non-equilibrium conditions lead to a larger H2 abundance than derived by Fall and Rees, who assumed equilibrium conditions.
Formation of Population III Objects due to Cosmic Strings
Authors: Hara Tetsuya , Miyoshi Shigeru
Published: July 2016

Behind the moving cosmic strings, wakes are formed from dark matter and baryon matter. The shock waves for baryon matter appear after the stage z≃790(μ/10-6). These wakes will fragment into lumps of mass M≃108(μ/10-6)3(vst/c)3/(1+z)1.5M⊙ where μ and vst~c are the line density in units of G=c=1 and the velocity of the strings.
The Comet – Asteroid Transition: Recent Telescopic Observations
Authors: Mcfadden Lucy-Ann
Published: July 2016

The phenomenon of a comet-asteroid transition presents the opportunity to study the comet reservoir in comparison to that from which asteroids are derived and to understand the evolution of comets. I discuss six significant areas which have impacted understanding of the comet-asteroid transition from recent years: new discoveries, discovery of dust and volatile comae at 2060 Chiron, observations of comet nuclei, observations of extinct-comet candidates, observations of dust trails associated with short period comets, and discovery of a dust tail on a prediscovery image of 4015 Wilson-Harrington. It is currently possible to recognize an object only as either a comet or an asteroid. There is currently insufficient information to recognize dormant or extinct cometary nuclei, though this is certainly the major goal being sought.
Meteoroid Streams
Authors: Steel Duncan
Published: July 2016

Meteoroid streams, producing meteor showers if some part of the stream has a node near 1 AU, have complex structures which are only just beginning to be understood. The old simplistic idea of a narrow loop being formed about the orbit of a parent comet with one, or possibly two, terrestrial intersection(s) is now being replaced by the recognition that their dynamical evolution may render convoluted and distorted ribbon shapes with eight or more distinct showers being generated. As such the streams are excellent tracers of the sorts of orbital evolution which may be undergone by larger objects (asteroids and comets) in the inner solar system; indeed it is now known that objects presently observed as Apollo-type asteroids may also be the progenitors of streams.

Searches for showers associated with newly-discovered possible parent objects may be carried out either via the calculation of theoretical meteor radiants (which have hitherto been derived using an untenable method), or through searches of catalogues of individual meteor orbits. In order to accomplish the latter, about 68,000 radar, photographic and TV meteor orbits from various programmes in the U.S.A., the former Soviet Union, Canada and Australia are available from the IAU Meteor Data Center, and more than 350,000 orbits of very faint meteors have been determined over the past three years using a new facility in New Zealand.

The discovery amongst IRAS data of dust trails lagging behind comets has opened up a new way in which meteoroid streams may be investigated, although the relationship between these trails and the streams observed as meteor showers at the Earth is by no means clear at this stage. Similarly radar, radio and spacecraft impact observations of meteoroids near cometary nuclei have added to our knowledge.

In spite of the improvement in our understanding of meteoroid streams over the past few years it is clear that there is much still to be done. The words of W.F. Denning in 1923 are still pertinent: “Few astronomers occupy themselves with the observation and investigation of meteors, and yet it is an attractive field of work offering inviting prospects of new discoveries”.
Meteorite Delivery and Transport
Authors: Farinella Paolo , Froeschlé Claude , Gonczi Robert
Published: July 2016

Understanding how meteorites and near–Earth asteroids reach their Earth–crossing orbits starting as fragments from main–belt asteroids is a basic prerequisite to identifying the original parent bodies of these objects and building a self–consistent cosmogonical interpretation of the observed properties of meteorites. We review the recent progress made in this area and the most important remaining open problems. These concern the physics of asteroidal collisions, the size distribution of small main–belt asteroids, the efficiency of different dynamical routes, and the relationships between asteroid taxonomic types based on spectrophotometry data and meteorite classes having different thermal histories and compositions.
A Review of Comets and Nongravitational Forces
Authors: Yeomans D. K.
Published: July 2016

A review is given on the recent advances in understanding the nature of the nongravitational forces that affect the motions of nearly all active comets.
Asteroid Spectroscopy and Mineralogy
Authors: Burbine Thomas H. , Binzel Richard P.
Published: July 2016

Spectroscopic observations of asteroids of smaller sizes and in the near-infrared have led to many exciting discoveries that have increased substantially our knowledge of the mineralogy of asteroids. These discoveries include the identification of hydrated M and E-asteroids, the mineralogical diversity of the S-class, anomalous S-asteroids, a possible source body of the aubrites, Vesta-like objects in the main belt, possible ordinary chondrite-like objects and one of the reddest objects in the solar system.
Coherent Backscattering by Solar System Dust Particles
Authors: Muinonen Karri
Published: July 2016

I review progress in interpreting the opposition effect and negative linear polarization observed for solar system dust particles. The so–called coherent backscattering mechanism has recently been introduced to explain the observations. However, fundamental difficulties in theoretical modeling still prevent quantitative interpretation. I also review some of the key observations that questioned the hitherto widely accepted mutual–shadowing explanation for the opposition effect. I summarize previous theoretical and experimental work on the opposition effect and negative polarization.
An Overview of Datasets on Small Bodies Available Through the Planetary Data System and Soard
Authors: Davis Donald R. , A'HEARN MICHAEL , Grayzeck Edwin , Sykes Mark V. , Del Castillo E.M. Alvarez , Tholen David , Garlow Kevin
Published: July 2016

In this chapter we present an overview of NASA's Planetary Data System project with emphasis on the Small Bodies Node (SBN) and describe a separate relational database project, the Steward Observatory Asteroid Relational Database (SOARD). We summarize the datasets that are currently available through SBN and SOARD as well as those planned to be ingested in the future. Procedures for accessing data from the SBN and SOARD via Internet are included.
3. Deviations from circular motion and the importance of southern hemisphere 21-cm. observations
Authors: Edmondson F. K.
Published: July 2016

(1) The suggestion of systematic deviations from circular motion by an angle ϕ, constant throughout the Galaxy, was first presented (Edmondson, 1955) [1] as an ad hoc way to recompute distances so as to make the long circular arm discovered by the Leiden observers (van de Hulst, Muller and Oort, 1954) [2] spiral in. The logarithmic spiral motions postulated in this model are not necessarily along the spiral arms, in contrast to the assumption made by Mrs Rubin (1955) [3].
8. Report on 21-cm. observations between l = 60° and l = 135°
Authors: Matthews T. A.
Published: July 2016

Observations of the 21-cm. hydrogen profiles have been taken between galactic longitudes l = 60° and l = 135°, with the 24-ft. radio telescope at the George R. Agassiz Station. The beam-width of the antenna is approximately 1°·7 between the half-power points. The electronic equipment used was a d.c. comparison radiometer, which has a signal channel with a frequency band-width of 15 kc./s. between the half-power points. At galactic latitude b = 0° the observations are generally spaced 2°·5 apart, although a few gaps of 5° exist. At b = + 15° and b = ሢ 15° the centres are 5° apart. A strip in latitude at l = 100°, and other centres at various latitudes (mainly at l = 75° and l = 87°·5) have also been taken, but little reference will be made to this material in the present paper.
19. Recent results in radio astronomy at the Ohio State University
Authors: Kraus J. D. , Ko H. C. , Nash R. T. , Stoutenburg D. V.
Published: July 2016

Research in radio astronomy at the Ohio State University covers a wide range of astronomical and engineering phases. In this paper the principal topics currently under investigation are briefly discussed. Reference is made to more detailed papers or reports published within recent months or now in the press.
20. Spectra of some radio sources
Authors: Hagen J. P.
Published: July 2016

At the tenth General Assembly of U.R.S.I. held in The Hague, Netherlands, in August 1954, the author presented a set of curves showing spectra of five bright, non-thermal, discrete radio sources. The spectra were based on the recent measurements at centimetre wave-lengths made with the 50-ft. antenna at the Naval Research Laboratory and on earlier published values for the flux at longer wave-lengths. The spectra are shown in Fig. 1. It is seen that there is in each case a discontinuity in the region between 30 and 100 cm. wave-length. Unfortunately, there had been no measurements made in this middle region. The slope of the two ends of the curve is nearly the same. There was considerable doubt at the time as to whether the spectra were in fact S-shaped as they would be if the two ends were joined in the simplest fashion. One possibility was that, due to the different techniques used in the centimetre and metre regions both in antennas and receivers, there might exist a calibration error of sufficient magnitude to cause the offset. For many reasons, this was hard to believe. In particular, measurements of solar flux at long and short wave-lengths yield a consistent picture.
28. The angular diameter of discrete radio sources
Authors: Palmer H. P.
Published: July 2016

An interferometer of readily varied resolving power has been constructed at Jodrell Bank, and since 1953 it has been used to measure the angular diameters of all but the faintest of the discrete sources reported in the survey of Brown and Hazard [1].
44. Comparison between radio and optical surface brightness distributions in the Magellanic Clouds
Authors: De Vaucouleurs G.
Published: July 2016

The distribution of radio surface brightness in the Large Cloud has been measured at 3·5 metres by Mills [1], and in the 21-cm. line by Kerr, Hindman and Robinson [2], in Sydney. A comparison with the distribution of the optical surface brightness in red light (λλ 5600–6600)[7] and with the surface density of stars brighter than mpg = 14·0(Mpg = − 4·7)[3], determined by the author at Mount Stromlo, is made in this paper.
53. Radio observations of the solar corona at sunspot minimum
Authors: Hewish A.
Published: July 2016

Previous experiments to determine the distribution of radio brightness across the solar disk at metre wave-lengths using the method of Fourier synthesis have been described by O'Brien (1953) [1]. These results could be explained in terms of a spherically symmetrical corona only if the electron density and temperature differed appreciably from estimates derived by visual methods (O'Brien and Bell, 1954) [2]. In order to check these measurements a similar series of observations was carried out in 1954 during an extended period of exceptionally low solar activity. Additional experiments, which gave information concerning the ellipticity of the brightness distribution, were made at Cambridge during the partial eclipse of June 1954.
56. Radio observation of the partial solar eclipse, 20 June 1955
Authors: Hatanaka T.
Published: July 2016

The partial solar eclipse of 20 June 1955 was observed at Tokyo and Toyokawa, where regular solar radio observations are conducted. A party was sent to Kagoshima by the Tokyo Astronomical Observatory. The locations, the frequencies observed and the types of aerial are listed in Table 1. The paths of the northern limb of the moon at three stations are shown by dotted lines in Fig. 3.
62. Optical evidences of radiational and corpuscular emission from active solar regions
Authors: Roberts W. O.
Published: July 2016

The detailed physical processes involved in centres of activity still remain obscure. Optical and radio noise observations enable us to state in increasing detail the phenomena that any comprehensive theory must explain. At times it seems that the complexity of the picture provided by these new data grows more rapidly than our ability to invent adequate theoretical models.
80. The moon as a scatterer of radio waves
Authors: Browne I. C. , Evans J. V.
Published: July 2016

Radio echoes from the moon at 120 Mc./s. have been obtained with a pulse length of 30 msec. and a pulse interval of 1·8 sec., using a fixed aerial directed due south. Their study has given information about the nature of the scattering function of the lunar surface.
Radar reflection characteristics of the moon
Authors: Senior T. B. A. , Siegel K. M.
Published: July 2016

In recent years many sets of experimental data have been obtained on radar reflections from the moon. After analyzing the results, workers tried to determine the scattering properties of the moon at radar wavelengths, and they concluded that rough-scattering laws could be ascribed to the surface. The available evidence no longer appears to support this view.
Sur les ionospheres planetaires
Authors: Link F.
Published: July 2016

Les recherches récentes [1, 2, 3] ont permis d'établir l'existence des émissions planétaires dans le domaine des ondes radio, dont les sources sont plus ou moins localisées sur les surfaces planétaires. En relation avec ces observations on peut aussi étudier les ionosphères planétaires [5]. Dans ces études on jouit d'un certain avantage de pouvoir se baser sur nos connaissances relativement avancées de l'ionosphère terrestre et nous en profiterons également dans ce rapport.
Flare-associated bursts at 18 Mc/s
Authors: Warwick Constance , Warwick J. W.
Published: July 2016

The occurrence of increased radio noise at the onset of short-wave fadeouts (SWF's) was noted by Appleton [1], who attributed the enhancements to solar emission. Payne-Scott [2], observing at about 19 Mc/s, measured burst intensities and times of occurrence to compare these high-frequency phenomena with radio events in the VHF range from 50 to 100 Mc/s.
Flare puffs as a cause of type III radio bursts
Authors: Giovanelli R. G.
Published: July 2016

It has been well established that a strong association exists between flares and type III bursts: Loughhead, Roberts, and McCabe [1] showed that 60 to 70 per cent of type III bursts occurred during the lifetimes of flares or microflares of apparent area exceeding about 20 × 10–6 solar hemispheres. On the other hand, only about 22 per cent of all such flares are associated with bursts. This low figure indicates that there are differences of degree or type between various flares, but the large area range involved shows that flare size alone is not the determining factor.
Etude interferometrique des sources d'activite solaire sur 3 cm de longueur d'onde
Authors: Kundu M. R.
Published: July 2016

Le rayonnement solaire sur ondes décimétriques et centimétriques est dû non seulement au rayonnement thermique de l'atmosphère solaire, mais aussi à un rayonnement dont la nature exacte est encore inconnue, et qui provient de régions émissives localisées sur le disque solaire. Le rayonnement global dans ce domaine de longueur d'onde augmente avec l'apparition de ces régions émissives sur le disque solaire et diminue avec leur disparition.
Some remarks on the polarization of 200-Mc/s solar radio emission
Authors: Cohen M. H. , Fokker A. D.
Published: July 2016

Detecting a weak linearly polarized component in an isolated solar burst is very difficult. It is a unique event and it is not possible to make a series of observations to reduce the error. Interference and reflections confuse the result and it is extremely difficult to determine the equipment parameters precisely, especially those pertaining to the antenna.
Concluding lecture
Authors: Minnaert M. G. J.
Published: July 2016

During this part of the Symposium, so carefully prepared by Messrs. Denisse and Pawsey, a great amount of new data has been presented, almost all obtained since the last international meeting on these subjects only one year ago. It is clear that this is a part of astronomy that develops impetuously. Hypothetical theories have been definitely confirmed by direct observation; on the other hand, new facts have been disclosed, increasing the complication of the phenomena; but we have reason to hope that we are in a transitory stage and that the complications will gradually be explained on clear and simple principles. It is of course impossible to mention in this summary the contents of all communications; only the more essential results will be reviewed.
Observations of extragalactic radio emission
Authors: Shain C. A.
Published: July 2016

Several extragalactic radio sources within reach of Sydney radio telescopes have been found to have angular sizes so great that they can be resolved with the pencil-beam aerials, which are available at three frequencies. It is possible to study in some cases the brightness distribution in some detail; in others to study the qualitative general picture. The observations with which the present paper is concerned are set out in Table I.
The distribution of neutral hydrogen in the orion region
Authors: Van Woerden H.
Published: July 2016

Neutral hydrogen is the main constituent of interstellar material. While solid particles and ionized hydrogen have long been studied, detailed investigations of the distribution of neutral hydrogen have only recently become possible. The first survey of neutral hydrogen in Orion was made by Menon [1, 2] with the Harvard 24–foot telescope and reported at Jodrell Bank in 1955. A more detailed study of the structure and dynamics of the interstellar medium in this region is now in progress with the 25–meter reflector at Dwingeloo. Its beamwidth is 0°.57 at 21 cm, corresponding to 5 parsecs at the distance of the Orion association. The bandwidth of the receiver was 20 kc/s, or 4 km/second, in this program. Observations with 10 kc/s bandwidth are being added.
Atomic hydrogen survey near the galactic plane
Authors: Burke B. F. , Ecklund E. T. , Firor J. W. , Tatel H. E. , Tuve M. A.
Published: July 2016

Using an 8-meter Würzburg parabola on an equatorial mount in Washington, D. C., we have completed about half of the necessary observations and reductions for a survey of the 1420-Mc/s hydrogen emission for all sky areas near the galactic plane which are visible here.
A survey of neutral hydrogen at high galactic latitudes
Authors: Erickson W. C. , Helfer H. L. , Tatel H. E.
Published: July 2016

Approximately 1000 observations of neutral hydrogen have been obtained with the 54-channel H-line receiver and the Würzburg antenna of the Carnegie Institution of Washington. H-line profiles have been observed at 10-degree intervals along the ±20-, ±30-, and ± 40-degree parallels of galactic latitude; at 20-degree intervals along the ± 50- and ±60-degree parallels; at 40-degree intervals along the ±70- and ±80-degree parallels and at the poles. Approximately two dozen observations have been taken at points near the galactic plane in order to correlate these observations with the Leiden survey [1]. The beamwidth of the Würzburg antenna was about 2 degrees. The observations were taken in two series, one series during the summer of 1957, and the other series during 1958 January. The video frequency bandwidth of the receiver is 12 kc/s. The profiles consist of averages of from two to six scans with integration times from 4.8 to 7.5 minutes.
Neutral hydrogen in the central part of the galactic system
Authors: Rougoor G. W. , Oort J. H.
Published: July 2016

While trying to determine the rotation curve in 1953 Kwee, Muller, and Westerhout [1] found long and faint wings in the line profiles within 20 to 25 degrees longitude from the center. The gas responsible for these wings should therefore lie within 3 kiloparsecs from the center. The velocities of the neutral hydrogen causing these wings are far greater than could be expected on the basis of a reasonable rotational model of the Galaxy. Therefore, the wings were tentatively interpreted as being caused by high turbulent velocities in the gas. In view of the new and better data obtained with the 25-meter telescope in Dwingeloo, this interpretation has now been dropped. The new conclusion is that all of the neutral hydrogen in these regions is expanding and at the same time taking part in the galactic rotation. The evidence for this conclusion will be briefly presented.
Neutral hydrogen in extragalactic systems
Authors: Volders Louise , Van De Hulst H. C.
Published: July 2016

In the past two years several extragalactic systems were observed for 21-cm emission with the 25-meter telescope at Dwingeloo. The results on the Andromeda nebula (mainly points along the major axis) have already been published [1]. Observations of M 33 and M 101 are finished, a few other systems are still being observed.
Hydrogen-line observations on the coma cluster
Authors: Muller C. A.
Published: July 2016

In 1956 and 1958 Heeschen [1, 2] reported hydrogen-line radiation at 21 cm from the Coma cluster of galaxies. He found a maximum antenna temperature of 2 °K and gave a profile with a width of about 4 Mc/s. From his details, it seems clear that these results depend mainly on a large number of drift curves on a frequency of 1386.9 Mc/s, since the accuracy of other points of the profile was much lower. Because the intensity is low and near the limit of what can be observed with present-day receivers we decided to repeat some of the observations with the 21-cm equipment at Dwingeloo.
Studies of radio sources at 159 Mc/s
Authors: Archer S. , Baldwin J. E. , Edge D. O. , Elsmore B. , Scheuer P. A. G. , Shakeshaft J. R.
Published: July 2016

Two years ago the Cambridge 4-aerial interferometer [1] was adapted to work at a frequency of 159 Mc/s, the resolving power thereby being increased by a factor of four over that at the previous frequency, 81.5 Mc/s. The overall beamwidth at 159 Mc/s is 1.2 degrees by 7 degrees but the beam contains interference fringes in two planes at right angles, so that, by phase-switching between the east pair and the west pair of aerials, sources with angular diameters greater than about 7 minutes of arc are eliminated. A survey using this technique has been carried out by Edge and Shakeshaft and may be called a “small diameter” survey. If the phase-switching receiver is connected between the north pair and the south pair of aerials it is possible to record sources with diameters up to about 1 degree and to measure diameters between 2 and 8 minutes of arc. Archer and Baldwin have used the aerial in this way to make a “large diameter” survey. These two surveys will be referred to collectively as the 3C survey.
Synchrotron radiation and solar radio outbursts at microwave frequencies
Authors: Takakura T.
Published: July 2016

The characteristics and the generation mechanisms of solar radio outbursts seem to be distinct at the frequencies above and below a certain cross-over frequency somewhere between 300 and 600 Mc/s (see Table I).
The determination of the energy distribution of relativistic electrons by the frequency distribution of their “synchrotron radiation”
Authors: Wallis G.
Published: July 2016

Relativistic electrons moving in a homogeneous magnetic field H emit “synchrotron radiation” with a frequency distribution which may be written in the following form.
Séance du mercredi 3 octobre, après-midi.: Président de Séance : A. R. Hogg.: Instruments et techniques
Authors: Courtès G.
Published: July 2016

Dans cet exposé, on cherche à définir les conditions que doivent remplir les instruments utilisables en campagne pour une mesure aussi bonne que possible des paramètres caractéristiques permettant de choisir l'emplacement d'un grand télescope d'au moins 3 m de diamètre.
Séance du jeudi 4 octobre, matin.: Président de Séance : G. Righini.: Solar Site Testing
Authors: Kiepenheuer K. O.
Published: July 2016

While at night almost all optical effects of the atmosphere have to be investigated by using stellar images, the solar observer has at his disposal the solar disk of about half a degree in diameter, covered all over with low contrast details of about 1″, the granules, and confined to the sky by a sharp limb. This enables him to observe all effects occuring within the area of the Sun simultaneously, to follow even the propagation of certain atmospheric effects across the disk. On the other hand he has only the Sun and cannot — as night astronomers might do — extend his observations to all directions in the sky.
I. — Afrique du Sud
Authors: Dommanget J.
Published: July 2016

I have not prepared anything on the subject of the present session.

The best I can do is to take as an example the organization of the field survey in Southern Africa, by the European Southern Observatory (E. S. O.) with which I was collaborating from November 1955 to March 1957.
A discussion of NGC 4755 and some other young clusters in the Galaxy and the Magellanic Clouds
Authors: Feast M. W.
Published: July 2016

A study of the cluster NGC 4755 (κ Crucis) was begun as a result of the several interesting problems raised by an earlier study of NGC 3293 (Feast 1958). Determinations of radial velocity and spectral type have been made in NGC 4755 from 102 spectra of 35 stars. Full details are published elsewhere (Feast 1963). These results were combined with the three-colour photometry of Arp and van Sant (1958). The cluster has a nearly-vertical evolved main sequence at spectral type B1. The spectral types and B, V measures for giants and dwarfs yield a mean reddening of +0m48 and a distance of 2 · 36 kpc. These values are considerably greater than those deduced by Arp and van Sant but they have been confirmed from an analysis of the three-colour measurements alone.
Galactic evolution and the two-colour diagram
Authors: Stoy R. H.
Published: July 2016

Information about the past history of the Galaxy may be obtained from a two-colour diagram, since the present distribution of stars in such a diagram depends on the past rate of star formation and the past metal abundances in the interstellar medium. As an illustration of this, I would like to discuss three diagrams that were recently prepared by Dr. M. E. Dixon from Cape photometric data (Dixon 1963a,b).
Planetary nebulae in the central region of the Galaxy
Authors: Perek L.
Published: July 2016

Planetary nebulae are convenient objects for studying the large-scale structure of the Galaxy. Firstly, they are easily recognized up to considerable distances on plates taken through an objective prism, and secondly, methods have been devised by various authors to determine their distances from two observable quantities: angular diameter and surface brightness. The importance of the subsystem of planetary nebulae has been accentuated especially by the discoveries by Minkowski and Haro of large numbers of planetaries in the direction of the galactic centre. The distribution of planetaries on the sphere suggests that they are connected with the galactic nucleus, but no direct determination of their distances, which would either confirm or contradict this statement, is available. The most serious obstacle in studying the subsystem of planetaries is the lack of observing data. The aim of the reported paper (Perek 1963) is to give a tentative outline of the distribution of planetaries in space based on extensive new observing material.
Galactic structure and rotation from cepheids
Authors: Kraft R. P. , Schmidt M.
Published: July 2016

Internally consistent distances to classical cepheids can be derived with considerable accuracy because they satisfy period-luminosity and period-colour relations. Studies of five cepheids that are members of galactic clusters have led to a revised period-colour relation and a new zero point for the period-luminosity relation. Distances have been computed for all cepheids given in recently published photoelectric surveys. The material can be regarded as complete to a distance of about 1500 pc.
The region of NGC 6522
Authors: Woolley Richard
Published: July 2016

The field of NGC 6522 is of especial importance because Baade considered that the cluster-type variable stars found in this field were located in a stellar concentration at the centre of the Galaxy. This particular field is a few degrees away from the actual centre, but is a region of comparatively small absorption, so that stars at considerable distances from the Sun can be seen and studied. Baade found a marked maximum in the frequency of these variables between 17m and 18m apparent photographic magnitude on plates which were exposed down to a limit of 20m. He supposed that this maximum was due to an actual concentration of cluster-type variables round the centre of the Galaxy. Assuming 0m0 for the absolute magnitude, and allowing 3 magnitudes for absorption, Baade found a value of 8·2 kpc for R0, the distance to the centre of the Galaxy. The absorption was computed from a rather high value for the reddening of the cluster NGC 6522 itself, which was given by Stebbins and Whitford.
Comparison of HI spiral pattern by optical structure of other galaxies
Authors: de Vaucouleurs G.
Published: July 2016

I. The maps of the spiral pattern of neutral hydrogen in the outer and intermediate regions of the Galaxy resulting from the 21-cm studies at Leiden and Sydney may be compared with the optical structure of other galaxies. If, as seems probable, most hydrogen arms coincide with or follow closely the optical arms marked by the blue supergiant stars, a comparison of the HI pattern with photographs in blue light should be meaningful. Such a comparison may lead to the identification of the galaxy type to which our Galaxy belongs. The regularity and symmetry of the HI spiral pattern indicates that our Galaxy is a normal system, and one to which, in principle, a definite type in the revised classification scheme (de Vaucouleurs 1958, 1959) can be assigned. If this assignment can be made successfully it should assist in the interpretation of the radio observations of the inner regions. There is a good possibility of at least restricting the range of galaxy types consistent with the HI spiral pattern of the outer regions because there is a high degree of correlation between galaxy type and multiplicity of the spiral pattern.
Some new observations relating to galactic radio sources and background structure
Authors: Hill E. R.
Published: July 2016

A survey of the distribution of radio emission at wavelengths of 75 and 20 cm along an extensive section of the Southern Milky Way has recently been carried out by M. Komesaroff and myself using the 210-foot radio telescope at Parkes. The area surveyed ranges from lII = 280 to 355° and extends on the average to 6 degrees either side of the plane. The beamwidths of the aerial at 75 and 20 cm are 50 and 14 min arc respectively. Observations at the shorter wavelength offer a picture of this section of the Galaxy at considerably higher angular resolution than hitherto available, while the 75-cm observations are expected to make a useful contribution to our spectral information.
Observations de restes de supernovae a la station de radioastronomie de Nançay
Authors: Boischot A. , Lequeux J.
Published: July 2016

La structure de restes de supernovae galactiques de petit diamètre apparent a été étudiée sur 1420 Mc/s avec l'interféromètre à 2 antennes de Nançay, dont la résolution maximale est 18″ EW et 1′ NS (Lequeux 1962). Taurus A a des dimensions de 3′,9 × 2′,7 à demi-intensité, l'angle de position du grand axe étant 126°. L'émissivité dans cette radiosource croît rapidement vers le centre; d'autre part ses dimensions augmentent avec la longueur d'onde, ce qui peut s'expliquer d'après Woltjer (1958) par une création continue d'électrons relativistes au centre de la radiosource. Cassiopeia A, au contraire de Taurus A, est parfaitement circulaire; en admettant la symétrie sphérique, nos observations montrent que presque toute l'émission radioélectrique provient d'une enveloppe sphérique de 2′,0 de rayon et 0′,6 d'épaisseur à demi émissivité. Les résultats obtenus sur les Supernovae de Képler et Tycho Brahé sont en accord avec ceux de Cal Tech sur 960 Mc/s: la Supernova de Tycho Brahé est peut-être une enveloppe sphérique, mais on ne peut rien dire de celle de Képler.
Radio studies of HII regions and galactic structure
Authors: Komesaroff M. M. , Westerhout G.
Published: July 2016

Radio studies of galactic HII regions are best carried out at the two ends of the radio spectrum. At high frequencies, of hundreds or thousands of megacycles per second, HII regions are seen by virtue of their thermal emission against a weak nonthermal background. Since radio waves are unaffected by the obscuration along the plane, it is possible in principle to see right through the Galaxy, and the high resolution which can be achieved in the thousands of megacycles range enables us to study at least the nearer regions in considerable detail. At low frequencies, below about 20 Mc/s, ionized hydrogen is seen in absorption against a bright nonthermal background. Since quite tenuous regions may be almost opaque at the lower frequencies, the technique provides quite a sensitive method of detecting them. The absorption increases with decreasing frequency so that studies at different frequencies enable us to see to varying depths along the line of sight and could permit the derivation of rough distance estimates.
Superassociations in distant galaxies
Authors: Ambartsumian V. A.
Published: July 2016

It is well known that the Large Magellanic Cloud contains in addition to a considerable number of ordinary O-associations a certain number of large objects which, however, are similar in nature to the associations. These objects were named “constellations” by Shapley. But the large complex 30 Doradus surpasses notably all of these objects both in diameter and in absolute brightness. The latter is of the order of −15m0 while its diameter is of the order of 600 pc. If we take the average absolute brightness of associations in our Galaxy as equal to −10m0 then it turns out that 30 Doradus is 100 times more luminous than the ordinary associations. The photographic images of more distant galaxies reveal that sometimes complexes occur in them of the same order of luminosity and dimensions as 30 Doradus. Therefore it seems to us useful to regard these complexes as a special class of objects and call them superassociations.
Radio polarization effects in the Galaxy
Authors: Gardner F. F.
Published: July 2016

Polarization effects involving our Galaxy have been studied in two ways: firstly, by observations of the polarization of the galactic radiation itself, and secondly, by the effects of galactic magnetic fields and ionization on the polarization of extragalactic radio sources. For an aerial of fixed dimensions, the intensity of the background varies at about λ2·5 (λ is wavelength) and that of the sources at about λ0·7. Thus background measurements are restricted to the longer wavelengths where the radiation is sufficiently intense, while sources are most easily studied at the shorter wavelengths where background confusion is small. The background radiation includes a component from small unresolved extragalactic radio sources in addition to the galactic radiation which is of interest in the first type of measurement. Both types of observation have been made with the 210-foot aerial at Parkes; the observations of sources were done in collaboration with J. B. Whiteoak and that of the galactic radiation with J. A. Roberts, assisted by J. B. Whiteoak and A. G. Little for part of the time.
A high-resolution 10-centimetre survey of the galactic centre region and spectral characteristics of the region
Authors: Cooper B. F. C. , Price R. M.
Published: July 2016

The region surrounding the galactic centre has been surveyed with the 210-foot telescope of the Australian National Radio Astronomy Observatory at a wavelength of 10·0 cm. At this wavelength the telescope beamwidth is 6.7 between half-intensity points.
The structure of the galactic nucleus
Authors: Parijsky Y. N.
Published: July 2016

The problem of the nuclei of galaxies is really one of the most important problems on the way to our understanding of numerous very strange phenomena which we observe in our own Galaxy as well as in many others, especially in radio galaxies.
Member stars of the Magellanic Clouds from proper motions
Authors: Woolley Richard
Published: July 2016

The material which I wish to present today is set out in Royal Observatory Bulletin Number 66, of which I have a few advance copies with me. The paper describes measures of about 700 stars in an area about 1° square. These are nearly all the stars down to a limit of V =14m5 in the area. Proper motions were measured by comparison between two plates taken on 1912 Jan. 21 and 1960 Nov. 16–17. The earlier plate had an exposure of 5 hr, which is exceptionally long for astrographic plates of those times. The measures of Ax and Ay (the shifts in units of one-tenth of a micron in the directions of right ascension and declination) were reduced by constructing plate constants such as would make the least-squares motion of the stars with B – V < 0 zero. In the reduction 104 such stars were used. The standard errors of measurement are σ(x) = ±15·9 and σ(y) = ±14·9, assuming that these stars really are members of the LMC and exhibit no relative proper motion. By using these plate constants, values of Ax and Ay were computed for all the remaining stars. The stars with 0·5 < B – V < 1·5 (apart from cepheids and a few reddened stars) are very plainly shown by their proper motions to be nearly all field stars, and indeed their motions can be satisfactorily explained by supposing them to be galactic stars showing the parallactic motion, galactic rotation, and a velocity ellipse appropriate to galactic stars. Stars with B – V > 1 · 5 cannot be determined to be members of the LMC on proper motion alone, but other considerations suggest that this is so. For example, their x, y distribution in the field follows the same pattern as that shown by the very blue stars, whereas the field stars (0 · 5 < B – V < 1 · 5) are uniformly distributed over the plate.
Neutral hydrogen in the Large Magellanic Cloud
Authors: McGee R. X. , Milton Janice A.
Published: July 2016

The neutral hydrogen gas in the Large Magellanic Cloud has been observed with the 14′.5 beam of the Parkes 210-foot telescope and the 48-channel H-line receiver. We wish to present a progress report based on computer reductions of integrated brightness and median radial velocities for some 4200 profiles. The survey is incomplete for some of the southern regions below dec. −73°. Assisting in the observations were our colleagues, M. W. Sinclair, C. J. Ohlston, and G. H. Trent and the staff at ANRAO, Parkes.
Old and intermediate populations in the Magellanic Clouds
Authors: Tifft W. G.
Published: July 2016

It is becoming increasingly evident that the older stellar components of the Magellanic Clouds are significantly younger, on the average, than the old star component of the Galaxy. Magellanic Cloud red globular-like clusters of the NGC 419 variety, and the common field stars of similar type, are almost certainly to be classified as intermediate-age populations by galactic standards. The oldest galactic population, seen in the galactic halo, globular clusters, and oldest galactic clusters, is apparently very sparse in the Magellanic Clouds, although in the SMC at least something very similar is seen in and near NGC 121.
Review of magellanic cloud problems
Authors: Thackeray A. D.
Published: July 2016

It must be obvious to all of us that no such Symposium on the Magellanic Clouds as we have been holding over the past few days would have been possible 10 years ago. At that time, radio work on the Clouds had scarcely begun. de Vaucouleurs, Buscombe, and Gascoigne were preparing their summary on Cloud problems as a preliminary to work with the Canberra 74-inch reflector, while the first results of work with the Radcliffe reflector were slowly beginning to emerge. Even five years ago, such a Symposium could scarcely have been fruitful, but the interest of many northern astronomers in the Clouds had certainly been excited. Now there are far more instruments and astronomers concentrated on Magellanic Cloud problems than ever before and the string of papers presented to this Symposium with lively discussions gives striking evidence of their activity.
Adaptation of the MK system to later spectra of medium dispersion by an intent of three-parametric classification
Authors: Dessy J. Landi
Published: July 2016

The aim of this communication is to describe the state of the new atlas and classification with 42Å/mm, which is being carried out at the Observatory of Córdoba in collaboration with the Observatory of La Plata. Several problems which we consider of some interest are also discussed.
Les classifications spectrales avec les prismes-objectifs de l'Observatoire de Haute-Provence et de l'Observatoire Europeen Austral
Authors: Fehrenbach Ch.
Published: July 2016

Dans notre programme de mesures de vitesses radiales aux prismes-objectifs nous déterminons régulièrement des types spectraux et les classes de luminosité dans la classification de W. W. Morgan (1).
Statistical criteria of stellar population types
Authors: Iwanowska W.
Published: July 2016

In connection with the spectrophotometric study of population-type characteristics of various kinds of stars, a statistical analysis of kinematical and distribution parameters of the same stars is performed at the Toruń Observatory. This has a twofold purpose: first, to provide a practical guide in selecting stars for observing programmes, second, to contribute to the understanding of relations existing between the physical and chemical properties of stars and their kinematics and distribution in the Galaxy.