bluuebunny/crossref_metadata_2025 huggingface dataset:
Harlow Shapley and Red Giant Stars
Authors: Martin F. , McCarthy S.J.
Published: July 2016

In five papers written between 1951 and 1955 Shapley considers the topic of red giant stars and reddish variable stars in the Magellanic Clouds. These works coincide with Shapley's final year as Director at Harvard and the first years of his retirement which extended a full score of years before his death in 1972. They include the following: Magellanic Clouds II (Supergiants/Red Variable Stars in the Small Cloud; January 1951); Magellanic Clouds IV (On Period Frequency Anomalies; February 1952); Magellanic Clouds VII (Star Colors and Luminosities in Five Constellations; March 1953); Magellanic Clouds VIII (On the Populations Characteristics of the Two Clouds; October 1953); and Magellanic Clouds XVI (Infrared Stars and Stellar Evolution; July 1955). These five papers, which appeared originally in the Proceedings of the National Academy of Science, may be found in the Harvard Reprint Series I as numbers 346, 360, 373, 376, and 425.
Ages and Metal Abundances of Star Clusters in the Magellanic Clouds
Authors: Smith Horace A. , Searle Leonard , Manduca Armando
Published: July 2016

It has long been apparent that the rich star clusters in the Magellanic Clouds differ widely in age, a circumstance which renders these clusters particularly useful in tracing the age-metallicity relations of their parent systems. We have attempted to exploit this potential by studying the integrated light of red globular clusters in the Large and Small Clouds.
The Absolute Luminosity of RR Lyrae Variables
Authors: Cacciari C. , Clementini G. , Prevot L.
Published: July 2016

We have taken UBVRI photoelectric photometry and CORAVEL radial velocities for 6 field RR Lyraes, i.e. SW And, YZ Cap, SW Dra, SS For, RV Phe and V440 Sgr, with the purpose of applying the Baade-Wesselink (B-W) method and determining their absolute magnitudes. The present improvements with respect to previous applications of the method are: a) the use of the (V-I) color, which shows the smallest sensitivity to gravity and metal abundance in the color-visual surface brightness plane. b) the use of a new grid of model atmospheres by Buser and Kurucz (1986), which include an improved treatment of opacity and convection. They provide a complete set of models for the relevant values of effective temperatures, gravities and metal abundances, thus avoiding the need of inaccurate interpolations or extrapolations.
Deep CCD Photometry in ω Cen and NGC 3201+
Authors: Ortolani S.
Published: July 2016

About 30 deep B and V CCD images, obtained at the 3.6 m ESO telescope, with the EFOSC in the focal reducer option, have been used to obtain color-magnitude diagrams and luminosity functions for the main sequence of the globular clusters ω Cen and NGC 3201. Two fields per cluster, at different distances from the center (25′ − 30′ for ω Cen and 7′.5 − 9′ for NGC 3201) were observed and separately reduced.
A Multicolor CCD Survey of Southern Globular Clusters
Authors: Forte Juan C. , Méndez Mariano
Published: July 2016

The existence of deviations of the observed photometric profiles with respect to the King models is a known fact (e.g., Newell and O'Neil, 1978; Aurière, 1983) and has been recently emphasized in the large survey by Kron et al., 1984. The origin of the light “excesses” (or defects) in the nuclear regions is, however, not very well understood. This work aims at clarifying this problem on the basis of multicolor (BVRIKC) CCD observations.
Low Luminosity Globular Cluster X-Ray Sources
Authors: Hertz Paul
Published: July 2016

Two classes of globular cluster X-ray sources are known. Each consists of compact objects accreting material from a close binary companion. The brighter class has a neutron star primary, and the low luminosity class has a white dwarf primary. These sources formed by tidal capture of the compact object by a main sequence dwarf in the core of the globular cluster. Their presence and number has implications on the end points of stellar evolution in globular clusters and on the formation of binaries in cluster cores.
Radial Velocity Profiles for Anisotropic Spherically Symmetric Clusters: An Example
Authors: Dejonghe Herwig
Published: July 2016

A 1-parameter family of anisotropic models is presented. They all satisfy the Plummer law in the mass density, but have different velocity dispersions. Moreover, the stars are not confined to a particular subset of the total accessible phase space. This family is mathematically simple enough to be explored analytically in detail. The family is rich enough though to allow for a 3-parameter generalization which illustrates that even when both the mass density and the velocity dispersion profiles are required to be the same, a degeneracy in the possible distribution functions persists. The observational consequences of the degeneracy can be studied by calculating the observable radial velocity line profiles obtained with different distribution functions. It turns out that line profiles are relatively sensitive to changes in the distribution function. They therefore can be considered to be more natural observables when a determination of the distribution function is desired.
Computer Aided Near Earth Object Detection
Authors: Scotti James V.
Published: July 2016

The Spacewatch program at the University of Arizona has pioneered automatic methods of detecting Near Earth Objects. Our software presently includes three modes of object detection: automatic motion identification; automatic streak identification; and visual streak identification. For automatic motion detection at sidereal drift rates, the 4σ detection threshold is near magnitude V = 20.9 for nearly stellar asteroid images. The automatic streak detection is able to locate streaks whose peak signal is above ~4σ and whose length is longer than about 10 pixels. Some visually detected streaks have had peak signals near ~1σ.

Between 1990 September 25 and 1993 June 30, 45 new Near Earth asteroids, two comets and two Centaur's have been discovered with the system. An additional six comets, five Near Earth asteroids, and one Centaur were also “re-discovered”. The system has directly detected for the first time Near Earth Objects in the complete size range from about 5 kilometers to about 5 meters. Each month ~2,000 main belt asteroids are also detected.

Future upgrades in both hardware, software, and telescope aperture may allow an order of magnitude increase in the rate of discovery of Near Earth Objects in the next several years. Several of the techniques proposed for the Spaceguard Survey have already been tested by Spacewatch, and others will need to be tested in the near future before such a survey can be implemented.
Asteroid Proper Elements: The Big Picture
Authors: Knežević Zoran , Milani Andrea
Published: July 2016

Four perturbation theories presently used to compute asteroid proper elements are reviewed, and their results are briefly discussed (Milani and Knežević, 1990, 1992, 1994, for low to moderate eccentricity/inclination main belt objects; Lemaitre and Morbidelli, 1994, for high e, I objects; Milani, 1993, for Trojans; Schubart, 1982, 1991 for Hildas). The most important recent improvements are described, in particular those pertaining to the upgrades of the previous analytic and semianalytic solutions. The dynamical structure of the asteroid main belt, as defined by the low order mean motion resonances and by linear and nonlinear secular resonances, is considered from the point of view of the effects of these resonances on the accuracy and/or reliability of the computation of proper elements and on the reliability of the identification of asteroid families.
The Dynamics of the Trojan Asteroids
Authors: Milani Andrea
Published: July 2016

The state of the art in the dynamics of the Trojan asteroids has progressed rapidly, since it has been possible to perform numerical integrations of many orbits for millions of years. Accurate proper elements are now computed by the synthetic method, that is from the output of a numerical integration; their stability, at least for time spans of a few million years, is good. This has allowed identification of Trojan families with an automated procedure closely mimicking the one used in the main belt. Although the families identified in a reliable way are only four, the occurrence of significant collisional evolution, not unlike that of the main belt, can be confirmed. The dynamical structure of the Trojan cloud, including the location of the main secular resonances, can be deduced from the proper elements and frequencies by a simple fit. However, many problems are not solved: the origin of a significant percentage of chaotic orbits showing no indications of instability; the location of the stability boundary of the Trojan cloud; the origin of the high inclination of most Trojans. We also do not know if there are “Trojans” for some other planets beside Jupiter: only one Mars Trojan has been found.
The Secular Resonances in the Solar System
Authors: Froeschle Christiane , Morbidelli Alessandro
Published: July 2016

In the last three years new studies on secular resonances have been done. The second–order and fourth–degree secular perturbation theory of Milani and Knežević allowed to point out the effect of mean motion resonances on the location of the linear and non linear secular resonances. Moreover this theory improved the knowledge of the exact location of the g = g6 (i.e. ν6) resonance at low inclination. Morbidelli and Henrard revisited the semi–numerical method of Williams, taking into account the quadratic terms in the perturbing masses. They computed not only the location of secular resonances, but also provided a global description of the resonant dynamics in the main secular resonances namely g = g5 (i.e. ν5), g = g6 (i.e. ν6) and s = s6 (i.e. ν16). The resonant proper element algorithm developed by Morbidelli allows to identify the dynamical nature of resonant objects, and is a powerful tool to study the mechanisms of meteorite transport to the inner Solar System. Purely numerical experiments have been done, which show: (i) the complexity of the dynamics when two resonances overlap; (ii) the efficiency of successive crossings of non linear resonances in pumping up the inclination of small bodies; (iii) the efficiency of the secular resonance ν6 as a source of meteorites up to 2.4 AU.
Dynamics of Comets: Recent Developments and New Challenges
Authors: Fernández Julio A.
Published: July 2016

There is a broad consensus that long-period comets come from a huge reservoir surrounding the solar system, as proposed originally by Oort. Yet, the classical picture of the Oort cloud has substantially changed during the last decade. In addition to passing stars, the tidal force of the galactic disk and giant molecular clouds have also been identified as major perturbers of the Oort cloud. In particular, the latter may be responsible for limiting the size of the stable Oort cloud to no more than ≈ 104AU, i.e. about one tenth of the classical Oort's radius.

Most comets are injected into the planetary region by the quasi-steady action of the tidal force of the galactic disk. The concentration of aphelion points of dynamically young comets toward mid-galactic latitudes is a consequence of its dominant influence. The frequency of comet passages into the inner planetary region could experience significant fluctuations with time as the Oort cloud meets random strong perturbers. The observed ordered pattern of most comet aphelia, associated with the galactic structure, argues against a recent strong perturbation of the Oort cloud.

The origin of the Jupiter family has become another point of intense debate. Jupiter family comets may come from a transneptunian comet belt -the Kuiper belt- from where they can reach the planetary region through chaotic motion. The Kuiper belt has become accessible to large telescopes, as shown by the recent discoveries of 1992QB1 and 1993FW, possibly belt members. The major challenge will be to explore the region usually inaccessible to external perturbers that goes from ~30 AU to a few thousand AU. A significant mass may have been locked there from the beginnings of the solar system, giving rise to an inner core that feeds the outer or classical Oort cloud. Our aim will be to briefly discuss some of the topics summarized here.
Cometary Nuclei
Authors: Rickman Hans
Published: July 2016

After a brief summary of current concepts on cometary nuclei, resulting from recent advances in observational techniques and laboratory experiments on cometary analogue materials, some of the outstanding problems facing theoretical modelling and interpretations of the new data is described. Emphasis is placed on the outgassing of species more volatile than water over the history of cometary nuclei, the structure of the nuclei in terms of porosity and tensile strength on a variety of different scales, and the volumetric importance and distribution of the refractory “dust” component. Near-surface interactions of dust grains and outflowing gas may be associated with the formation of large dust aggregates and mantling of the nuclei.
Molecular Abundances in Comets
Authors: Crovisier Jacques
Published: July 2016

The molecular composition of cometary volatiles is a basic information on the nature of comets and a clue to their formation mechanisms. It is only recently that direct identifications of cometary volatiles were obtained through in situ exploration as well as from remote sensing at UV, IR and radio wavelengths. An inventory of known cometary volatiles is presented, with a critical review of the evaluations of their abundances.
Small Bodies Around Other Stars
Authors: Sicardy Bruno
Published: July 2016

We briefly review recent advances in the observation and study of planetary bodies in extra-solar systems. We summarize in particular the main physical properties of the β-Pictoris dust disk, and the status of new disk observations. Theoretical implications of infalling discrete bodies are considered, in particular, the existence of possible perturbing planet(s) causing this influx. Such planets could spectacularly disturb circumstellar dust disks, thus revealing themselves in spite of their intrinsic faintness as mere point sources. Finally, we describe the recent possible discovery of at least two planets around a pulsar. This underlines the potential existence of planets in rather exotic circumstances.
4. Progress report on 21-cm. research by the Netherlands Foundation for Radio Astronomy and the Leiden Observatory
Authors: Westerhout G.
Published: July 2016

From November 1953 to August 1955, about 2500 line profiles have been measured with the Kootwijk receiver, under the supervision of Ir C. A. Muller. His receiver is of the well-known frequency-switching type. Two pairs of channels in the second i.f. amplifier, about 5 Mc./s., have band-widths of 36 kc./s. The components of one pair are 1080 kc./s. apart; the second pair is shifted 500 kc./s. with respect to the first. Each pair of channels, combined with the continuously variable second local oscillator and with the fixed, crystal-controlled pair of first local oscillators, which are also 1080 kc./s. apart, gives a switching system. The power at a certain frequency is compared with that at a 1080 kc./s. higher frequency during half the switching period and with that at a 1080 kc./s. lower frequency during the other half by switching between the two first local oscillators. The signals are fed through an integrating network with a time constant of 54 sec. At the outputs of the two pairs are two separate recorders, each giving one-half (or more) of a line profile (see Fig. 1). A continuous frequency calibration of the second local oscillator provides 10 kc./s. markers on the records, accurate to 1 in 106. The limiting sensitivity is 0·7°K., with an overall noise figure of 6·3 (8·0 db.). The 7·5 m. Würzburg aerial has a beam-width between half-power points of 1°·9 × 2°·7.
27. Intensity distribution across the Cygnus and Cassiopeia sources
Authors: Jennison R. C.
Published: July 2016

Measurements of the angular distribution of intensity across the intense discrete sources in Cassiopeia and Cygnus have previously been handicapped by lack of knowledge of the phase of the Fourier transform at very long aerial spacings. The technical difficulties of measuring the phase of the transform and also of calibrating the absolute amplitude have been solved by a new technique involving three stations. This method enables the phase to be measured relative to a frame of reference within the source and obviates the need for retaining the phase angles accurately constant on the removal of one of the aerial systems to a new site. The phase measurement is not limited to observations of the central fringe, and useful measurements may be made on all the fringes contained within the aerial polar diagrams.
45. The quiet and active sun: Introductory Lecture
Authors: Allen C. W.
Published: July 2016

It is both convenient and realistic to regard the solar radio-emission as being composed of a quiet permanent part coming from the whole of the sun's surface, together with a superimposed variable part emitted from centres of activity. The variable part can be further subdivided into various components to which separate reference will be made. The components are almost independent and add to one another to give the solar emission recorded by radio telescopes. For our understanding of the phenomena it would be a great advantage if the components could be completely and reliably segregated but this is not always possible. The results from a wide network of observational stations are recorded in theQuarterly Bulletin of Solar Activity, from which the intensities and characteristics of most of the components may be extracted.
48. The radial brightness distribution of the sun at 9·4 cm.
Authors: Haddock F. T.
Published: July 2016

The Naval Research Laboratory has supported four eclipse expeditions (in the years 1947, 1950, 1952 and 1954) under the direction of Dr J. P. Hagen. The principal purpose was to find the variation of the solar microwave radiation during a total optical eclipse of the sun. During the last two eclipses the sun was sufficiently inactive to enable us to derive the centre-to-limb brightness distribution at a wave-length of 9·4 cm., on the assumption that the distribution was circularly symmetrical. Since these two eclipses were of the same optical magnitude (within 0·12 %) and were measured with the same equipment located at each eclipse near the centre-line of mid-totality, it is of interest to compare their results. The 1954 eclipse observation was described in the last paper by Mayer, Sloanaker and Hagen. The 1952 observation has already been described [1].
49. On the uniformity of the lower chromosphere
Authors: Thomas Richard N. , Athay R. G.
Published: July 2016

It is appropriate at a solar session during a radio astronomy conference to report on an analysis of optical observations to infer the properties of a non-spherically-symmetric chromosphere. For the first detailed model of such a non-symmetric chromosphere was that presented by Giovanelli (1949) [1] in an attempt to reconcile apparent contradictions between radio and optical data. Here we summarize some investigations based only on optical data, obtained by the High Altitude Observatory at the 1952 eclipse. Our observations of this eclipse were obtained as part of a joint programme with the Naval Research Laboratory, which conducted radio observations. Dr Hagen reports on the radio material (papers 46 and 47). The optical data in the present paper come from hydrogen and helium alone, the metallic data being still in reduction.
50. Observations of brightness over the disk of the quiet sun at frequencies of 85, 500 and 1400 Mc./s.
Authors: Pawsey J. L.
Published: July 2016

Observations of radio emission from the quiet sun, which is believed to be due to thermal emission from the ionized gases of the solar atmosphere, provide information about the electron density and temperature throughout the atmosphere. Comprehensive information requires observations, preferably of the brightness distribution over the solar disk, over a large range of wave-lengths. Because such observations are both difficult and tedious it is desirable that a final model atmosphere should be based on a pool of observations taken by independent methods and observers. The following are recent contributions to this pool from the Radiophysics Laboratory.
51. Interpretation of solar radio-frequency disk brightness distributions derived from observations with aerials extended in one dimension
Authors: Smerd S. F. , Wild J. P.
Published: July 2016

Several recent papers have dealt with observations of brightness distributions over the solar disk, which were derived either from two-aerial interferometer observations at various spacings and orientations (e.g. O'Brien, 1953) [1], or from multiple-element interferometer fan-beam observations at various orientations (e.g. Christiansen and Warburton, 1954) [2], In each a two-dimensional distribution is derived from a number of essentially one-dimensional observations by a Fourier synthesis method described by O'Brien. The detail given by these methods must be limited by the finite resolution of the individual observations (limited by the maximum aperture of the aerial system), but the form of the limitation is not obvious, though its knowledge is required when relating the observations to a solar model.
54. The ellipticity of the corona at 80 Mc./s. during sunspot minimum 1954
Authors: Tuominen J.
Published: July 2016

The solar eclipse of 30 June 1954 was observed in the neighbourhood of Helsinki on the frequency 81·5 Mc./s. [1]. At the maximum of the optical eclipse 90 % of the solar diameter was occulted by the moon. We may accordingly assume that on the wave-length of observation the eclipse was nearly central. Further, the angle between the orbit of the moon and the solar equator was only 12°.
61. Sunspots: radio, optical and geomagnetic features
Authors: Simon P.
Published: July 2016

Noise storms on metre wave-lengths originate high in the corona over particular sunspots. Generally, the enhanced radiation comes to a maximum when these sunspots cross the central meridian. If the radiation exceeds a fixed intensity, the sunspots are called noisy (R sunspots); the others are called quiet (Q sunspots). Unfortunately until now only a few interferometer measurements enabled us to know these ‘noisy sunspots’, but the strong directivity of this emission can be used to determine these sunspots in a statistical manner. We have done this for the sunspots having an average area bigger than 100 millionths of the sun, from 1947 to the middle of 1951. We have thus studied the statistical features for 350 sunspots, 160 of which are noisy and 190 quiet.
65. On the mechanism of solar outbursts
Authors: Kiepenheuer K. O.
Published: July 2016

Today it is taken for granted that the solar outbursts are produced by plasma oscillations of coronal matter, excited by a corpuscular radiation originating in the inner corona (Pawsey and Smerd, 1953) [1]. A certain component of this corpuscular radiation is obviously identical with that generating geomagnetic storms.
67. Solar radio emission and the acceleration of magnetic-storm particles
Authors: Schlüter A.
Published: July 2016

The shift of the emitted frequencies towards lower frequencies during a solar outburst is usually interpreted as due to a progressive rarefaction of the emitting gas. If one assumes that the emitted frequency is identical with the plasma frequency and furthermore that the density of the emitting plasma is similar to the density of the solar corona at the location of the radiating material, then it follows that this material is subject to an acceleration throughout the solar corona which compensates or exceeds the effect of the gravitational field of the sun.
68. Polarization of solar radio bursts
Authors: Hatanaka T.
Published: July 2016

The polarization observation of solar radio emission at 200 Mc./s. was started in December 1954 at the Tokyo Astronomical Observatory with a new type of radio polarimeter[1, 2]. With a pair of crossed dipoles at the focus of a 10 metre paraboloid of equatorial mounting, it gives almost simultaneously six components of polarization, two circular and four linear, on a time-sharing basis by using electronic switching. Fig. 1 shows the block diagram of the circuit and the combination of modulators and demodulators. 6AS6 pentodes are used as the time modulators. The duration of each gate pulse is 1/1600 sec. and one set of observations is obtained in 1/200 sec. One of the principal features of the present scheme is to use a common receiving system for all the components in order to avoid inevitable errors due to differences or changes in the gain and in the central frequencies of different receivers. A new type of square-law detector is employed in the present system [3]. It has rapid response time and excellent stability.
Radar observations of the moon at 10-cm wavelength
Authors: Hey J. S. , Hughes V. A.
Published: July 2016

This note describes some of the initial results derived from observations of radar echoes from the moon obtained at 10-cm wavelength at the Royal Radar Establishment, Malvern. The radar, which has been described elsewhere [1], has a transmitter of 2 megawatts peak power with a pulse length of 5 microseconds and a pulse recurrence frequency of 260 per second. The receiver is of conventional design and has a bandwidth of 500 kc/s and a noise factor of 7.5. The aerial used is the 45-foot diameter radio telescope shown in Fig. 1. The telescope is controlled from a mechanical computer that converts the lunar coordinates into azimuth and elevation, which are then fed into a servo drive.
Observations of planetary nonthermal radiation observations of planetary nonthermal radiation
Authors: Smith Harlan J. , Douglas J. N.
Published: July 2016

Observations at Yale of planetary nonthermal noise were first made in 1957 from March to June at 21.1 Mc/s by a single close-spaced phase-switching interferometer with Yagi elements. To be accepted as possibly planetary, noise events had to be unidentifiable as terrestrial; they had to fit the interferometer pattern; and they had to occur when the planet was in the Yagi beams. Thirteen events satisfied these criteria for Jupiter (Fig. 1a), giving the rotation histogram Fig. 2a when plotted according to the System III period of Carr et al. [1]. The pattern is quite similar to that obtained for the immediately preceding months by the Florida group (Fig. 2b).
Radio observations of the comet Arend-Roland
Authors: Whitfield G. R. , Högbom J.
Published: July 2016

Observations were made at Cambridge between 1957 March 12 and May 13 in an attempt to detect radio emission from the comet at 3.7- and 7.9-m wavelengths by observing radio stars through its tails, to derive information on the electron density in the manner used by Hewish [1] in investigating the outermost layers of the solar corona.
The quiet sun at 88-cm wavelength
Authors: Firor J.
Published: July 2016

An attempt has been made to measure the one-dimensional brightness distribution of the sun at 88-cm wavelength. Strip scans of the sun made with a 4′.8 fan beam have been superimposed and the lower envelope drawn, after the manner of Christiansen [1].
The origin of the slowly varying component
Authors: Christiansen W. N. , Mathewson D. S.
Published: July 2016

Two main mechanisms have been proposed to explain the origin of the slowly varying component [1] of the decimeter-wavelength radiation from the sun. Both theories [2, 3, 4] are based on the facts that (a) this component of the sun's radiation is relatively steady in output for periods of days; (b) it originates from active regions on the sun; and (c) its magnitude is closely related to the sunspot area in the region.
Radio picture of the sun at 3.2-cm wavelength
Authors: Vitkevich V. V. , Kuz'min A. D. , Salomonovich A. E. , Udal'tsov V. A.
Published: July 2016

In 1957 July the two-dimensional intensity distribution of radio emission over the solar disk was determined at 3.2- and 10-cm wavelengths. The observations were carried out on the radio telescope 31 m in diameter at the Crimean Radio Astronomical Station of the Physical Institute of the Academy of Sciences of the U.S.S.R. The radio telescope was an immovable parabolic reflector with the axis set in the meridian plane on 22-degrees declination [1]. Scanning the pattern of the radio telescope in the declination range ±32 minutes of arc to obtain the intensity distribution was done by setting the feed and preamplifier on a movable carriage reciprocating near the focal plane. In combination with the sun's daily movement it provided the two-dimensional solar distribution along a zigzag line. These sections gave the radio picture.
Les emissions de type IV
Authors: Boischot A.
Published: July 2016

L'interféromètre à 32 antennes de Nançay [1, 2], a permis de caractériser un nouveau type d'émission sur 169 Mc/s accompagnant certaines éruptions chromosphériques. Cette émission s'identifie sûrement avec la deuxième partie des grands sursauts ou “phase d'orage” signalée par R. Payne-Scott [3] et H. W. Dodson [4], mais certains caractères la différencient cependant nettement des orages de bruit.
Polarization of bursts of solar radio emission at microwave frequencies
Authors: Tanaka H. , Kakinuma T.
Published: July 2016

The intensity and polarization of solar radio bursts at 9400, 3750, 2000, and 1000 Mc/s have been continuously observed since 1957 July. At 3750 Mc/s, the linearly polarized components were also measured during 4 months from 1957 October till 1958 January [1]. The analysis of observations to 1958 May reveals the following points:

1. Many bursts at these frequencies show a difference in the intensity of two circularly polarized components. Frequency distributions of maximum degree of polarization of bursts are shown in Fig. 1, where weak bursts are excluded to reduce errors. At 3750, 2000, and 1000 Mc/s, particularly at 3750 Mc/s, the bursts of small degree of polarization are predominant. Circularly polarized bursts are occasionally observed at 2000 and 1000 Mc/s, but at higher frequencies the degree of polarization is usually less than 50 per cent.

2. At 3750 Mc/s, no linearly polarized components could be detected in 117 bursts for a bandwidth of 10 Mc/s. The burst at this frequency is usually composed of a small degree of circularly polarized component and a randomly polarized one.

3. Sometimes the sense of polarization varies with frequency. An example is shown in Fig. 2. On this occasion, the degree of polarization is small at 3750 Mc/s and the sense of polarization reverses between 2000 and 3750 Mc/s. Roughly grouped in Table I are 129 bursts simultaneously observed at four frequencies. The reversal of sense was found in 64 per cent of such bursts. Sometimes the sense of polarization varies with time, as may be found in our monthly report. Some of such phenomena may be interpreted by the motion of the source from the preceding part of a bipolar spot group to the following one or vice versa [4].

4. In Fig. 3, the bursts associated with flares are classified in three types as regards the sense of polarization, and they are allocated to each of four quadrants on the solar disk according to the position of the flares. At higher frequencies, the sense of polarization seems to correlate with the position of the source as in the case of S component [2, 3]. A precise distribution map at 9400 Mc/s is shown in Fig. 4.
Bursts of microwave radio emission associated with solar flares
Authors: Gelfreich G. B. , Ikhsanova V. N. , Kaĭdanovskiĭ N. L. , Soboleva N. S. , Timofeeva G. M. , Umetskiĭ V. N.
Published: July 2016

Bursts of solar radio emission which coincide in time with solar flares are occasionally observed over the whole frequency range up to 35,000 Mc/s. The purpose of this paper is to describe briefly some bursts observed at Pulkovo at wavelength λ = 3.2 cm.
Observation interferometrique a 169 Mc/s des centres R, sources des orages de bruit
Authors: Avignon Yvette , Boischot A. , Simon P.
Published: July 2016

L'interféromètre a ses lobes principaux sensiblement parallèles au plan méridien [1]. Ils ont une largeur de 3′.8 et sont distants les uns des autres de 2 degrés. La détermination de l'heure et de la durée du passage des centres R dans les lobes permet de déterminer leur distance à un plan nord-sud passant par le centre du disque solaire et leur diamètre apparent dans l'hypothèse d'une symétrie circulaire et d'une luminance uniforme. Les différentes causes d'erreur introduisent une indétermination de l'ordre d'une minute d'arc au plus sur les positions des centres R.
On the polarization of solar radio emission at 1.5-m wavelength
Authors: Alekseev U. J. , Vitkevich V. V.
Published: July 2016

1. Solar radio emission is usually characterized only by the intensity, i.e. by a single value at a given frequency.

In polarization measurements the radio emission is characterized by four values (for example, by the unpolarized-component intensity and three components of the polarization ellipse).

Here we see that observations of solar radio emission with a polarimeter give us considerably more extensive information than the usual observations give. It is a very important fact that the polarization of the radio emission is determined by the strength and direction of the magnetic field of emitting regions. Thus, we connect the polarized radio emission with a magnetic field that is noticeably higher than the field in the region which we can study by optical methods.

It should also be noticed that one of the most interesting unsolved problems is establishing the nature of the disturbed solar radio emission. It is clear that new information on the polarization of radio emission will contribute to the solution of this problem; but in spite of its importance and urgency, investigations to solve it are being carried on only in a small number of observatories. The observations in Australia and the work in Japan may be mentioned.
Manifestations possibles de la couronne de chapman dans la radioastronomie
Authors: Link F.
Published: July 2016

On peut se demander si la grande extension de la couronne solaire demandée par l'hypothèse de Chapman [1] pourrait se manifester par les phénomènes de réfraction lors d'une occultation, par exemple celle de la source du Taureau.
Neutral hydrogen in galactic clusters
Authors: Drake F. D.
Published: July 2016

Observations of the neutral hydrogen content of the galactic clusters h and χ Persei, the Pleiades, the cluster in Coma Berenices, Praesepe, and M 67 have been made with the Harvard College Observatory 60-foot radio telescope. The receiver used was the original receiver made by the Ewen Knight Corporation for the Harvard 24-foot radio telescope. The observations were of three kinds: (1) right-ascension drift curves at 50 kc/s bandwidth, with the receiver fixed-tuned to the frequency of maximum cluster emission, if known, or to the frequency given by the cluster optical radial velocity; (2) conventional frequency profiles at the position of maximum cluster radiation; (3) “residual” frequency profiles, where there is significant general galactic radiation at the cluster frequency and position. These data provide the spatial distribution of any H i in the cluster vicinity that is in excess of the general galactic H i, and a frequency profile for this excess hydrogen. Any excess H i found is considered associated with the cluster if it agrees in velocity and position with the optical cluster.
Concluding lecture
Authors: Van De Hulst H. C.
Published: July 2016

This session contained all the papers that did not fit very well in the other sessions, i.e., those papers dealing neither with the solar system nor directly with problems of galactic structure nor with the faint sources and their statistics. This negative criterion has led to a variety of contributions, the common denominator of which is that we try to find out as much as we can about everything. I shall try to summarize the main points and add my own comments.
Concluding lecture
Authors: Blaauw A.
Published: July 2016

Results have been presented from continuum observations in the range from 19.7 to 1390 Mc/s (λ = 15 to 0.22 m).
A comparison of an interferometer and total-power survey of discrete sources of radio-frequency radiation
Authors: Hazard C. , Walsh D.
Published: July 2016

A fundamental limitation to the number of radio sources observable with a given aerial system is set by the finite solid angle of the aerial beam's reception. In any survey, whether it be a total-power survey or an interferometer survey, errors tend to occur whenever two sources are present simultaneously in the aerial beam. If the receiving system is a total-power system the contributions from the two sources will add, and either they will be interpreted as a single source of greater intensity than each of the individual sources, or the sources may be resolved but their intensities and positions may be subject to considerable errors.
The nature of the radio sources
Authors: Ryle M.
Published: July 2016

Optical search in the positions of radio sources has led to the certain identification of some eight sources with galactic nebulosities, and nineteen with extragalactic nebulae.
Remarks on cosmology
Authors: Mcvittie G. C.
Published: July 2016

First, I should like to say something about the use of highly specialized models in cosmology. The Einstein—de Sitter model is a relativistic model in which the cosmical constant and the space-curvature constant are both equated to zero. Likewise, the pressure is assumed to be zero throughout the history of the universe, except perhaps at the initial instant. It is well-known that the first two constants can be determined from observation, if not at present, at any rate as the data are refined in the future. Hence, I think it is a weakness to prejudge the issue and assign a priori values. Nor is it self-evident to me that the pressure must always have been zero even if it is zero now. Composite models, with nonzero pressure at first, followed by a zero-pressure condition, need to be examined.
The theoretical explanation of radio emission
Authors: Burbidge G. R.
Published: July 2016

To discuss the theories of radio emission it is convenient to divide the sources into five different classes: (1) planets, (2) the sun, (3) galactic nebulosities, (4) galaxies taken as a whole, and (5) clusters in galaxies. About (1) and (2) I shall say little. It appears that the temperatures of Venus and Jupiter obtained from the thermal radio emission measures are in reasonable agreement with the temperatures determined by the older astronomical methods. No theories explaining the nonthermal emission from Jupiter have yet been developed, though there has been discussion of the possibility that some type of discharge mechanism leading to plasma oscillations is involved.
Cosmic rays and radio waves as manifestations of a hot universe
Authors: Gold T. , Hoyle F.
Published: July 2016

Attempts to explain both the expansion of the universe and the condensation of galaxies must be very largely contradictory so long as gravitation is the only force field under consideration. For if the expansive kinetic energy of matter is adequate to give universal expansion against the gravitational field it is adequate to prevent local condensation under gravity, and vice versa. This is why, essentially, the formation of galaxies is passed over with little comment in most systems of cosmology. Yet the galaxies, and the clusters in which they are often found, are such an important characteristic property of the universe that it is unsatisfactory to dismiss their origin in the vague term “fluctuation phenomenon.”
Séance du lundi 1er octobre, après-midi.: Président de séance : K. O. Kiepenheuer.: Procedures for location of astronomical observatory sites
Authors: Stock J.
Published: July 2016

The effectiveness of large telescopes is limited by the terrestrial atmosphere rather than by their optical or mechanical performance. Due to its refractive, absorbing and scattering properties, the atmosphere is one of the important elements that determines the limiting magnitude, resolving power and the wavelength range within which observations are possible. These effects are present even on the clearest nights. In addition, general meteorological conditions such as cloudiness, wind, high humidity, or extremely low temperatures further impair or prevent the operation of astronomical equipment. These effects can be avoided by placing the equipment above most or all of the atmosphere (balloon-borne telescopes, satellite observatory, lunar observatory). For the foreseeable future the cost of placing and operating a telescope outside the atmosphere will be such that it will be restricted to the investigation of problems that cannot be solved with observations made only from the ground. It seems possible, however, to choose sites for terrestrial observatories where the atmospheric effects are minimized. Just where the optimum conditions can be found is not yet known, but it is highly probable that none of the existing observatories is located on the World's best site. In fact, it is quite possible that conditions may be found on hitherto unknown sites that could bring a considerable advance in astronomical research before going to space equipment. Whether or not it is practicable to erect and operate an astronomical observatory on the optimum site (or sites) will depend largely on location, because in addition to excellent astronomical observing conditions the site has to be accessible and capable of development for satisfactory working conditions.
The causes of atmospheric inhomogeneities
Authors: Scorer R. S.
Published: July 2016

There are several different atmospheric causes, of imperfections in the images seen in a telescope. The most serious are due to thermal convection from the ground, or the stirring of a stable layer at the ground by wind : choice of site and observatory design can reduce these effects. In the free air well away from the ground some of the largest inhomogeneities may be due essentially to large gradients of humidity, and certain cloud types indicate the mechanisms by which such inhomogeneities are established. Temperature fluctuations caused by pressure fluctuations in eddies close to the telescope are probably not serious, and can be avoided by observatory design.
Séance du samedi 6 octobre, matin.: Président de séance : J. Rösch.: General summary and conclusion
Authors: Rösch J.
Published: July 2016

It is a great honour and pleasure for me to welcome, at the opening of the last session of this Symposium, the presence among us of Prof. Oort, Retiring President of I. A. U. I would like to thank him for his interest in the problems we are dealing with, and I am confident that our discussions to day will enable him to tell the Executive Committee of the Union that we have usefully spent our time here.
Spectrophotometry of 14 southern planetary nebulae
Authors: Aller L. H. , Faulkner D. J.
Published: July 2016

The theory of radiative and collisional processes in gaseous nebulae makes possible precise predictions of line and continuum intensities as functions of density, electron temperature, and degree of ionization of the emitting gases. It predicts, for example, the relative intensities of successive members of the Balmer series (Balmer decrement), and of corresponding transitions in the Balmer and Paschen series. Hence accurate line intensity measurements are not only of astrophysical interest; they also serve to assess the amount of space absorption.
Interpretation of velocity distribution of the inner regions of the Galaxy
Authors: de Vaucouleurs G.
Published: July 2016

I. The large positive and negative velocities in the 21-cm line profiles near the galactic centre have indicated the presence of substantial departures from circular motions in the central parts of the Galaxy. The Leiden astronomers (Oort and Rougoor 1958; Rougoor and Oort 1960) have interpreted these observations in terms of an “expanding arm” at a mean distance of about 3 kpc from the centre. It is not clear how these arms or arcs are related to the regular spiral structure, if the Galaxy is an ordinary spiral similar to M31 as commonly assumed. If, on the other hand, the Galaxy is similar to the SAB(r) or SAB(rs) systems, as suggested by the multiplicity of the spiral pattern discussed in another communication, a different interpretation of the velocity distribution is possible.
On the HII regions in galaxies
Authors: Sersic J. L.
Published: July 2016

In the present paper we shall consider that the HII complexes observed in galaxies may be interpreted as the resulting Strömgren volume produced by a cluster or association of exciting stars. If ρH is the density of the hydrogen surrounding the cluster or association and I the number of ionizing quanta (λ < 912 å) emitted by the stars, the ionized volume becomes
Review of galactic problems
Authors: Schmidt M.
Published: July 2016

The original plans for this Symposium called for a review of galactic problems by the late Dr. J. L. Pawsey and myself. In the early days of radio astronomy Pawsey often represented CSIRO at international symposia. Many of us enjoyed the lucid reviews that he presented of the work done at CSIRO, much of which was carried out under his inspiring and energetic guidance. It is at a moment such as the present one that we remember him vividly and miss him deeply.
Notes on the structure of the SMC as observed in 21-cm line radiation from neutral hydrogen
Authors: Hindman J. V.
Published: July 2016

Earlier surveys of the line radiation from neutral hydrogen in the Magellanic Clouds (Kerr, Hindman, and Robinson 1954; Hindman, Kerr, and McGee 1963; Hindman et al. 1963) have shown that the amount of gas associated with these extragalactic bodies is relatively large. The gas appears widespread, surrounding the stellar bodies in a single continuous and very tenuous envelope with a marked bridge in the vicinity of the optical wing of the SMC linking the two main concentrations.
Comparison of the Magellanic Clouds by other irregular barred spirals
Authors: de Vaucouleurs G.
Published: July 2016

I. The main structural characteristics of the irregular barred spirals of the magellanic type are illustrated in Figure 1. They were first detected 10 years ago on small-scale photographs of the Large Cloud taken at Mount Stromlo (de Vaucouleurs 1954, 1955) and were later found to be uniformly present in many other “late-type” barred spirals designated SB(s)d and SB(s)m in the revised classification system (de Vaucouleurs 1959). These stages form a continuous transition between the regular barred spirals of the “S-shaped” sequences, such as NGC 1365: SB(s)b, NGC 1300: SB(s)bc, NGC 7479: SB(s)c, and the completely irregular system IBm showing only an axial bar and little or no traces of whorls, such as NGC 4449 and 4214. Examples of the transition stages are NGC 7741: SB(s)cd, NGC 1313: SB(s)d, NGC 4027: SB(s)dm, NGC 4618: SB(rs)m, and the Large Magellanic Cloud: SB(s)m (Fig. 2). The Small Cloud, because of its interaction with the Large Cloud and its unfavourable inclination, is more difficult to classify precisely; it may be designated as SB(s)mp or IB(s)mp to indicate the presence of residual (or incipient) spiral structure (de Vaucouleurs 1957a).
Regions HII dans les Nuages de Magellan et les galaxies proches
Authors: Courtes G.
Published: July 2016

Les clichés du Grand et du Petit Nuage décrits dans cet article ont été pris à travers un filtre interférentiel d'une qualité analogue aux précédents (voir dans le même Symposium: “Distribution des vitesses radiales des régions HII dans la direction du Centre Galactique”), mais centrés évidemment sur la longueur d'onde correspondante au déplacement Doppler-Fizeau dû à la vitesse radiale des Nuages qui, comme on le sait, est de l'ordre de +200 km/sec. La largeur de la bande passante était de 10 å.