bluuebunny/crossref_metadata_2025 huggingface dataset:
The Nuclei of Nucleated Dwarf Elliptical Galaxies - Are they Globular Clusters?
Authors: Zinnecker H. , Keable C. J. , Dunlop J. S. , Cannon R. D. , Griffiths W. K.
Published: July 2016

It came as a great surprise that many dwarf elliptical galaxies of very low surface brightness in the Virgo Cluster have conspicuous bright star-like nuclei (Reaves 1983, Binggeli, Sandage and Tammann 1985). These nuclei are at least a factor of 10 more luminous than the brightest globular clusters in the Local Group and comparable only to the very brightest globulars surrounding M87. They contain a considerable fraction (1 to 20%) of the total light of the parent galaxy (Binggeli, priv. commun.). Their physical nature and origin are a matter of debate (Zinnecker et al. 1985, van den Bergh 1985, Norman 1986, Zinnecker 1986) but optical spectroscopy for 3 objects indicates a stellar composition with a range similar to globular clusters (Bothun et al. 1985). It has been suggested that a central nucleus is formed when off-center bound star clusters migrate to the center as a consequence of dynamical friction (Norman 1986). Support for such a scenario comes from CCD observations of IC 3475 which reveal numerous knots near the center of this dwarf irregular galaxy (Vigroux et al. 1986). These knots have the same color as the parent galaxy and are interpreted as intermediate age star clusters.
Photometry of Faint Stars in Globular Clusters using the Six Meter Telescope
Authors: Samus N.
Published: July 2016

Our program is based on photographic and photoelectric UBV photometry of globular cluster stars with the Soviet 6 m telescope. M 10 = NGC 6254 remains, regretfully, the only cluster for which we were able to gain photoelectric observational material sufficient for calibration of the photographic photometry for faint stars. Samus and Shugarov (1983) presented for M 10 a V, (B - V) diagram showing an unusually large magnitude difference between the main sequence turn-off point and the horizontal branch, V(TO) - V(HB) ≍ 3.8 mag. It seemed of interest to compare M 10 and M 12 by their values of V(TO) - V(HB). A preliminary calibration of the faint star photographic photometry in M 12 leads to V(TO) - V(HB) ≍ 4 mag (Mironov et al., 1984). One may notice that in the classification introduced by Mironov and Samus (1974, 79), which is based mainly on the horizontal-branch morphology, both M 10 and M 12 belong to group I, presumably the older group. V, (B-V) diagrams were also published by us for NGC 288 and M 2 = NGC 7089 (Samus and Shugarov 1978, 79).
The Ages of Globular Clusters Derived from BVRI CCD Photometry
Authors: Alcaino Gonzalo , Liller William
Published: July 2016

Main sequence photometry has been obtained in the BV system for at least 36 galactic globular clusters (Peterson 1986). One of the most important objectives for these continued researches by several astronomical groups has been that of determining the ages of globular clusters. During the past five years, a general consensus has emerged that the spread in age among the known galactic globular clusters could be as small as 1 billion years; Burstein (1985) suggests that the average age of these objects lies between 14 and 17 Gys.
Turnoffs and Ages of Globular Clusters
Authors: Buonanno F. , Corsi C. E. , Pecci F. Fusi
Published: July 2016

The way to arrive at (even relative) ages for globular clusters involves the determination of their (relative) distances. We would like to see a theory which would fit the absolute magnitudes of RR Lyrae stars as determined from observations (Sandage effect). We have examined a sample of 17 CM diagrams of galactic globular clusters, 11 of which were observed at ESO and reduced with the program, ROMAFOT and 6 of which were taken from the literature. In Fig. 1 the difference in bolometric magnitude between the turnoff point and the location of the zero-age horizontal branch (ZAHB), δV RRTO (bo1) is plotted versus [Fe/H]. It turns out that δV RRTO ≃ δ RRTO (bo1) + 0.1 = 3.56 ±0.15. We are faced with the problem of determining how the horizontal branch scales with metallicity in order to understand the constant value of 3.56 in this relation.
Radial Velocity Study of NGC 6712
Authors: Grindlay J. , Bailyn C. , Mathieu R. , Latham D.
Published: July 2016

We report MMT Echelle radial velocity observations of 52 giants within 3 core radii of the center of NGC 6712. The mean radial velocity of these stars is −107.5 km/s, with a line of sight velocity dispersion of 4.0 km/s. We use these data, together with CCD photometry of the cluster, to derive a mass to light ratio for the center of the cluster of 0.7, an unusually low value.
On Gravothermal Oscillations
Authors: Goodman Jeremy
Published: July 2016

An isolated conducting gas sphere (an idealized model of a globular cluster) can have non-singular postcollapse similarity solutions for appropriate energy sources. Solutions have been found for a source mimicking three-body binaries; they are parametrized by N, the number of stars in the cluster, and are linearly stable if N < 7000, overstable if 7000 < N < 40,000, and unstable if N > 40,000. The nonlinear development is always oscillatory and produces a typically lower central concentration than in the “equilibrium”.
Search Programs for Comets
Authors: Marsden B. G.
Published: July 2016

Although there are currently no professional search programs specifically designed for comets, comet discoveries are a significant by-product of the current search programs for near-earth asteroids. With their emphasis on the opposition point and the ecliptic, asteroid patrols are clearly biased toward discovering short-period comets. A. comparison of the comet discoveries made at elongations of less than 120° from the sun during the ten-year intervals ending in 1892 and 1992 indicates that the current opposition searches are not able to displace visual searches in the vicinity of the sun. Modification of the near-opposition search region to that proposed for the Spaceguard Project would be helpful, but—as also proposed for Spaceguard—supplementation is still necessary for high-inclination objects. CCD experimentation in the regions traditionally searched visually by amateurs would be useful. Searches for particular types of object like Kreutz sungrazers and comets near Jupiter in space are briefly discussed.
Density of Meteoroids and Their Mass Influx on the Earth
Authors: Babadzhanov Pulat B.
Published: July 2016

According to the investigation technique it is customary to divide meteoroids into three groups: 1) micrometeorites, with masses between 10–13 g and 10–6 g, and densities between 0.4 and 4 g/cm3; 2) meteorites, for which the chemical composition is studied in detail, and having densities from 2 to 8 g/cm3; 3) meteoroids proper, with masses larger than 10–6 g, which produce meteoric phenomena in the Earth's atmosphere detected by optical and radar means.

On the basis of available photographic and radar observations in Dushanbe the influx M(m) of meteoroids with mass equal or greater than m is determined as log in kg to the Earth per day. This formula is applicable to a mass range from 10–6 g to 102 g.

The phenomenon of meteoroid fragmentation in the atmosphere was observed repeatedly by means of different methods and especially using the photographic technique of instantaneous exposure. Among four principal forms of fragmentation, the quasi-continuous fragmentation, i.e. a gradual release of smallest fragments from the surface of a parent meteoroid and their subsequent evaporation, is most common. The analysis of photographic observations shows that about 30% of meteoroids display this type of fragmentation. According to the theory of quasi-continuous fragmentation and on the basis of lightcurves of meteors, the densities of 85 meteoroids have been determined, which vary in the range from 0.1 to 8 g/cm3. Not only porous and crumbly meteoroids but more dense stony and stony-iron meteoroids are also the subjects of fragmentation as well.
Comets as a Reflection of Interstellar Medium Chemistry
Authors: Greenberg J. Mayo , Shalabiea Osama M.
Published: July 2016

A brief summary of the observed infrared and other properties of interstellar dust is given. Chemical, physical and morphological criteria are discussed concerning the degree to which there are constraints relating comets to interstellar dust chemistry representative of the presolar nebula. Results of theoretical modelling of dust and gas evolution in dense clouds are used to compare with observed dust composition. Sources of the distribution of simple as well as complex molecules in the coma are related to what is presently known about the volatile ices in interstellar dust and to processes leading to evaporation of organic “refractory” grain mantle material represented by laboratory residues produced by photoprocessing of ices. The criterion of preservation of interstellar volatiles in comets leads to the further criterion that the ice in comets is amorphous. Criteria for relating interstellar dust volatiles to asteroids are discussed.
Comet Taxonomy and Evolution
Authors: Schleicher David G.
Published: July 2016

Measurements of physical and dynamical properties of comets have yielded considerable evidence for variations in the origin and evolution of these primordial objects. Given these findings, one might reasonably expect to observe differences in the chemical composition as well. This paper reviews our current state of knowledge of the similarities and differences in the composition of comets, and summarizes the recent findings by A'Hearn et al. (1994) for two taxonomic classes of comets and evidence of compositional variation due to origin and/or evolution.
Formation of Outer Solar System Bodies: Comets and Planetesimals
Authors: Bailey Mark E.
Published: July 2016

Observations of massive, extended discs around both pre-main-sequence and main-sequence stellar systems indicate that protoplanetary discs larger than the observed planetary system are a common phenomenon, while the existence of large comets suggests that the total cometary mass is much greater than previous estimates. Both observations suggest that theories of the origin of the solar system are best approached from the perspective provided by theories of star formation, in particular that the protoplanetary disc may have extended up to ~103AU. A model with a surface density distribution similar to a minimum-mass solar nebula, but extending further in radius, is derived by considering the gravitational collapse of a uniform, slowly rotating molecular cloud. The boundary of the planetary system is determined not by lack of mass, as in previous ‘mass-limited’ models (i.e. those with a sharp decrease in surface density Σ beyond the radius of the observed planetary system), but instead by the increasing collision time between the comets or planetesimals initially formed by gravitational instability beyond the planetary zone. Bodies formed beyond ~50 AU have sizes on the order of 102km and represent a collisionally unevolved population; they are composed of relatively small, unaltered clumps of interstellar dust and ices with individual sizes estimated to range up to ~10 m. By contrast, bodies formed closer in, for example in the Uranus-Neptune zone, consist of larger agglomerations of dust and ices with individual sizes ranging up to ~1 km. Planetesimals formed by gravitational instability at smaller heliocentric distancesrare typically much smaller than those formed further out, the massesmpbeing proportional to Σ3r6, but subsequent collisional aggregation in the planetary region is expected to produce bodies with sizes ranging up to 102km or more. In both cases the first-formed solid objects may be identified with observed cometary nuclei; some accumulate to produce the outer planets, but the majority are ejected, either to interstellar space or into the Oort cloud. Observed comets represent a dynamically well-mixed group from various sources; they are expected to comprise a heterogeneous mix of both pristine and relatively altered material and to have a broad mass distribution ranging up to the size of the largest planetesimals.
The Uppsala Asteroid Data Base
Authors: Magnusson P. , Lagerkvist C.-I. , Dahlgren M. , Erikson A. , Barucci M.A. , Belskaya I. , Capria M.T.
Published: July 2016

A collection of data and results of asteroid photometry and related observations has been made available by anonymous ftp. It contains all published asteroid lightcurve photometry, a table of reliable rotation periods, and a collection of all asteroid spin vector determinations. Here we describe the database in some detail.
A Public–Domain Asteroid Orbit Database
Authors: Bowell Edward , Muinonen Karri , Wasserman Lawrence H.
Published: July 2016

We are constructing a database of J2000.0 osculating elements for all asteroids that have reasonably calculable orbits, and to make it publicly accessible via anonymous ftp. The database will be a very dynamic one; it will change on a quasi-daily basis as new observations and orbits become available. At present, an incomplete version of the database is online. In this paper, we present and discuss sample records of asteroid orbital data as they might appear in more mature form.
1. Studies of the 21-cm. line and their interpretation
Authors: van de Hulst H. C.
Published: July 2016

The subject of the 21-cm. line needs no introduction to this audience. Perhaps as an introduction I may mention one moment that belongs to the pre-history of the investigations of this line. In the spring of 1944 Oort said to me: ‘We should have a colloquium on the paper by Reber; would you like to study it? And, by the way, radio astronomy can really become very important if there were at least one line in the radio spectrum. Then we can use the method of differential galactic rotation as we do in optical astronomy.’
6. The distribution of atomic hydrogen in the inner parts of the Galaxy
Authors: Schmidt M.
Published: July 2016

The determination of the distribution of hydrogen from 21-cm. observations in parts of the Galaxy, which are nearer to the centre than the sun, is seriously handicapped by the fact that the observed radial velocity of the hydrogen clouds determines only the distance to the galactic centre. So two possible values of the distance to the sun correspond to one value of the frequency. We have used as a criterion to separate the contributions from the two regions the latitude distribution of the radiation.
13. 21-cm. absorption effects
Authors: Hagen J. P. , Lilley A. E. , Mcclain E. F.
Published: July 2016

In the discussion which follows, there are presented three areas of the Naval Research Laboratory's study of absorption effects in the spectra of discrete sources produced by interstellar hydrogen. The first topic presented is the theory of the two mechanisms which are operative in producing the observed absorption effects. The second area of the discussion presents the observations and their interpretations for sources which lie in directions where the effects of galactic rotation are an important aid in the interpretation of the observed absorption. When galactic rotation effects are small, special techniques must be developed to supplement the absorption effect in order to determine distances to the discrete source. An example of the latter technique is contained in the third topic presented here, in a study of the source Sagittarius A. All the data discussed here were obtained with the Naval Research Laboratory's 21-cm. radiometer in conjunction with the 50-ft. antenna. A signal band width of 5 kc. (1 km./sec.) was employed throughout.
21. The low-frequency spectrum of Cygnus A and Cassiopeia A
Authors: Lamden R. J. , Lovell A. C. B.
Published: July 2016

The published measurements of the intensity of the radio sources cover a frequency range down to a lower limit of 22·6 Mc./s., at which measurements have been made on Cygnus and Cassiopeia by Hey and Hughes (1954)[1]. Information about the spectrum at still lower frequencies is difficult to obtain because of interference arising from ionospheric reflexion of distant radio transmitters. Some of this trouble can be alleviated by using a narrow pencil-beam radio telescope for reception and the present communication describes measurements made on frequencies of 16·5, 19·0, 22·6 and 30·0 Mc./s. using the 218 ft. transit radio telescope at Jodrell Bank.
22. Preliminary observations of point sources at 12·5 and 15·5 Mc./S.
Authors: Wells H. W.
Published: July 2016

At frequencies much below 30 Mc./s. radio astronomy is substantially affected by the earth's ionosphere. The principal effects of the ionosphere are to absorb signals from extra-terrestrial sources, and to propagate earthbound interfering signals over long distances. Successful observation at these relatively low frequencies requires (1) a clear observing channel, or (2) operation during the interval immediately preceding sunrise when the maximum usable frequency for oblique-incidence ionospheric propagation has fallen below the operating frequency. Since early attempts to locate a clear channel between 10 and 20 Mc./s. were fruitless, we accepted the condition in (2) realizing that ionospheric absorption would also be minimized, since the observing frequency, under these conditions, is more than three times greater than the ionospheric critical frequency at vertical incidence.
25. Intensities of the discrete sources in Cassiopeia, Cygnus and Taurus at Λ 3·2 cm.
Authors: Razin V. A. , Pletchkov V. M.
Published: July 2016

Measurements of the intensities of radio emission from the three most powerful discrete sources were carried out early in 1955 at the Gorky radio astronomical station ‘Zimenky’ (latitude 56° 9·5′). The arrangement used for these measurements is described elsewhere [1]. The main part of the aerial consists of a paraboloid, 4 metres in diameter, on an alt-azimuth mounting. The beam has an opening (between half-power points) equal to 32′. The effective area of the aerial was determined by comparison with the standard megaphone antenna for solar radio emission [2] and equals 10 m.2. The efficiency of the aerial is determined according to the method of measurement of the proper radio emission of the aerial [3]. The reception device is of a modulation type. The fluctuation threshold of the sensitivity of the device for the used time constant of 20 sec. equals 0°·6 C., which corresponds to a flux of non-polarized radiation of 1·65 × 10−24 w.m.−2 (c./s.)−1 reaching the aerial.
42. Radio astronomy and the origin of cosmic rays
Authors: Unsöld A.
Published: July 2016

At present we can observe the origin of only the solar component of cosmic rays. The sun emits cosmic rays in connexion with flares and probably also continuously on a smaller scale. Thus the emission of cosmic rays appears to be connected much more closely with non-thermal radio emission than with thermal radiation of light and heat.
47. Observation of the solar eclipse of 30 June 1954 at 9·4 cm. wave-length
Authors: Mayer C. H. , Sloanaker R. M. , Hagen J. P.
Published: July 2016

The observation of the total solar eclipse of 30 June 1954 at 9·4 cm. wavelength was one of the experiments carried out by the Naval Research Laboratory eclipse expedition to Sweden. The apparatus was set up in the city of Oskarshamn at a point about 5 km. north of the centre-line of totality. At this location the eclipse was total, with magnitude 1·035, at 12h 48m u.t.
59. Spectral observations of solar activity at metre wave-lengths
Authors: Wild J. P.
Published: July 2016

This paper summarizes some recent results obtained with the solar radio-spectroscope at Dapto (Sydney), which has been in operation since 1952. The basic instrument is a receiver which sweeps through the frequency range 40–240 Mc./s. every half a second. Each spectrum is displayed as an intensity-modulated line, and successive spectra are recorded photographically on continuously moving film to give a dynamic record of the spectrum.
69. Disturbed radio emission from the sun as a sum of small monochromatic peaks
Authors: Vitkevitch V. V.
Published: July 2016

Observations of the radio emission from the sun carried out during recent years at the Crimean Station of the Physical Institute of the U.S.S.R. Academy of Sciences showed that the occurrence of spots appreciably increases the intensity of the solar radio emission in the range of metre wave-lengths. This increase of intensity has two components. The first (S-component) changes comparatively slowly with time. The second (P-component) consists of individual brief bursts (of the order of a second and less) of small amplitudes (10–100 % of the intensity of the quiet sun). The P-component is manifested most clearly in the emission connected with spots of small areas, when the general increase of the intensity is insignificant. Such a situation has been utilized for the study of the spectrum of individual small peaks.
71. A peculiar type of scintillation of solar radio radiation
Authors: Fokker A. D.
Published: July 2016

Some authors (Payne-Scott and Little (1952) [1]; Owren (1952) [2]) have mentioned a phenomenon in the enhanced solar radio emission which they call ‘non-selective fading’. The present paper is meant to call attention to another, rather peculiar, type of scintillation in the radio emission of the sun, which differs from the non-selective fading in some important respects. This scintillation has been observed since 1952 by the division ‘Ionosphere and Radio Astronomy’ of the Netherlands Telecommunications Service in the course of a continuous survey of solar radio radiation. It has been found at the radio frequencies 140, 200 and 545 Mc./s.
74. The distribution of meteor masses
Authors: Browne I. C. , Bullough K. , Evans S. , Kaiser T. R.
Published: July 2016

Kaiser (1953) [1] has shown how it is possible, from statistical studies of radio echoes from meteor trails, to obtain values of the exponent s in the assumed equation for the number of meteors n(α) of line density α where αm is the maximum electron line density (number of electrons per cm.) produced in the trail of a meteor. If the simple theories of the meteor ionization process are correct, αm is proportional to the meteor mass m, so that from radio echo studies it should be possible to obtain a measure of the meteor mass distribution:
where n(m) is the number of meteors with mass in the range from m to m + dm.
77. Possible proofs of the lunar atmosphere
Authors: Link F.
Published: July 2016

In the period 1955–57 a number of occultations of two radio sources 05·01 Taurus and 06·01 Gemini by the Moon takes place [1]. They will give an excellent opportunity to examine not only the exact position and the shape of these sources but possibly also some traces of the lunar atmosphere [2].
79. Radio emission from the moon and the nature of its surface
Authors: Troitzky V. S. , Khaikin S. E.
Published: July 2016

A theoretical study of the integral radio emission of the moon, measured at the wave-length of 3·2 cm. (Zelinskaja and Troitzky[1]; Kajdanovsky, Turusbekov and Khaikin[2]), was carried out at the Gorky radio astronomical station ‘Zimenky’ and at the Physical Institute of the Academy of Sciences of the U.S.S.R. The following expression for the average radio temperature of the entire lunar disk, as a function of the lunar phase, Ωt, was obtained (Troitzky, 1954) [3]:
Here tan ξ = δ/(1 + δ) and δ = β/κ, where β is the attenuation coefficient of the thermal wave, κ the power attenuation coefficient of the radio wave. Further, Tm = 374°K. is the temperature of the subsolar point, Tn is the temperature at the lunar midnight, Θ = Tm – Tn and k0 is the reflexion coefficient of radio waves for vertical incidence (k0 ≈ 0–1). The numerical coefficients in equation (1) were obtained as a result of averaging the Fresnel reflexion coefficients over the whole disk. The degree of polarization of the total radio emission was calculated and was found to be about 4 %.
Preliminary observations at 10-cm wavelength using the NRL 84-foot radio telescope
Authors: McClain E. F. , Sloanaker R. M.
Published: July 2016

The largest steerable radio telescope in the United States (Fig. 1) has recently been completed at the U.S. Naval Research Laboratory's Maryland Point Observatory in Charles County, Maryland. The new instrument, an 84-foot parabolic antenna, or “dish,” was designed by the D. S. Kennedy Co. of Cohasset, Massachusetts. Originally ordered in June 1955, the instrument has been three years in design, construction, and erection. Carried on a polar or equatorial mount, the 84-foot aluminum reflector can be aimed at any point in the sky and can track any celestial object from horizon to horizon. It is the largest antenna with this type of mounting in the world.
Resultats preliminaires obtenus avec l'interferometre a 8 antennes sur 3 cm de longueur d'onde
Authors: Gutmann Monique , Steinberg J. L.
Published: July 2016

Un interféromètre de type Christiansen fonctionne depuis Février 1958 à la Station de Nançay sur la longueur d'onde 3.2 cm. Cet appareil comprend 8 miroirs paraboliques de diamètre 1.10 m régulièrement disposés sur une poutre de 11.5 m à monture méridienne; le préamplificateur est monté également sur la poutre.
A new radio telescope of high resolving power
Authors: Khaĭkin S. E. , Kaĭdanovskiĭ N. L.
Published: July 2016

Attempts to construct large parabolic reflectors for microwaves have met with the following difficulty. For normal operation of radio telescopes, the form of the reflecting surface must not deviate from the theoretical by more than 0.1λ; therefore, the larger its size the higher the requirements for relative accuracy (i.e., the ratio of the largest permissible deviation to the cross-section of the reflector). So far, a relative accuracy better than 10–4 has not been attained in any of the existing radio telescopes, and there are no grounds for supposing that it can be increased considerably.

Since the deviation from the theoretical form of the surface should not be more than 0.1λ, then for a relative accuracy of 10–4, the diameter of the reflector D cannot be much larger than 1000λ, and the beamwidth cannot be less than 3 minutes of arc (the beam angle is equal to about λ/D at half-power width).
Relation entre les emissions de rayons cosmiques solaires et certains sursauts radioelectriques
Authors: Denisse J. F.
Published: July 2016

Le 20 Mars 1958, L. Peterson et J. R. Winckler [1] ont observé une brève augmentation du rayonnement cosmique d'une dizaine de secondes de durée; au même instant une éruption chromosphérique se développait sur le soleil et un sursaut radio assez exceptionnel était enregistré sur ondes centimétriques et décimétriques.
Galactic background surveys and the galactic halo
Authors: Baldwin J. E.
Published: July 2016

Two surveys of the galactic background radiation at low frequencies have recently been made at Cambridge. At 38 Mc/s, a survey of the sky between declinations −20° and +70° has been made by Blythe [1] using a new type of pencil-beam aerial system. This instrument, consisting of an array 1200 feet long in an east-west direction together with a small movable aerial, used the principle of aperture synthesis to provide a beam 2°.2 × 2°.3 at the zenith increasing to 2°.2 × 7°.4 at an angle of 70 degrees from the zenith.
The distribution and identification of the sources
Authors: Brown R. Hanbury
Published: July 2016

At the present stage of radio astronomy it is convenient to divide the observed radio sources into two classes: Class I sources, which show a concentration into the galactic plane; and Class II sources, which are distributed more isotropically. In the present session we shall be concerned principally with the Class II sources.
The optical identification of radio sources
Authors: Dewhirst D. W.
Published: July 2016

Previous attempts to identify any large proportion of the discrete sources discovered at meter wavelengths have met with small success. In the investigation briefly reported here an extensive search has been made on the original plates of the 48-inch Palomar—National Geographic Society Sky Survey, using the available published radio data, but more especially the as yet unpublished results of a survey between +50 and −10 degrees declination that has been made with the interferometer of the Mullard Radio Astronomy Observatory, Cambridge. This radio survey (3C) has been carried out at 159.5 Mc/s using the aerial array of the 2C survey [1] in modified form. An account of the observation and reduction of this recent survey is given by other speakers in the Symposium. The area of sky covered by the 3C survey, and the criteria for the selection and classification of the sources, are likely to undergo small extensions and modifications before the final catalog is ready for publication, but these modifications will be of a minor character and will not alter the general conclusions of the present paper.
The relation of radio astronomy to cosmology
Authors: Hoyle F.
Published: July 2016

The advent of radio astronomy provides a new observational tool for arriving at tests of the different theoretical cosmologies. The tests may be either wholly new, or revivals in a more cogent form of earlier work in visual astronomy.
The origin of the belt of galactic radio waves
Authors: Tunmer Harriet
Published: July 2016

Most of the background of cosmic radio waves comes from our own Galaxy. In the equatorial plane this origin is evident, and the obvious features can be directly related to the Galaxy's structure. Away from the plane the emission comes from a roughly spherical halo, which accounts for most of the total emission from the Galaxy. Some features in this part of the sky are not evident from optical studies; the most important is a circular belt of emission passing not far from the center and the anti-center. It is impossible that this should be extragalactic in origin, since it is more than twice as bright as the brightest estimates of the whole galactic component, and optical evidence would be expected of such a major irregularity in the distribution of the galaxies, or indeed of a single spiral galaxy close to or enveloping our own. We turn therefore to a suggestion of an origin in our own Galaxy.
Ages and kinematics of clusters
Authors: Eggen O. J.
Published: July 2016

The recent emphasis on stellar evolution, especially as seen in star clusters, has given us — mainly through Sandage's synthesis of the available material — a good outline of the evolutionary process. Although work of a survey nature obviously must be continued, if only to turn up clusters with an age not represented among those now known, I believe the time has come to concentrate a major effort on detailed studies of the brighter known clusters of various ages. Our knowledge of even the Hyades and Pleiades clusters is far from complete. A full account cannot be given here but I would like to mention some examples of the details in the colour-magnitude arrays that may eventually lead to important tests, or revisions, of current evolutionary models.
Measurements of neutral hydrogen in galactic star clusters
Authors: Davies R. D. , Tovmassian H. M.
Published: July 2016

A search was made for neutral hydrogen in the following galactic star clusters — the Pleiades, NGC 1502, the Trapezium-Orion cluster, NGC 2244, and NGC 6910 (Davies and Tovmassian 1963). Observations were made with a six-channel receiver having a 5 kc/s bandwidth; it was used with the 250-foot radio telescope which has a beamwidth of 12′ by 18′. The first stage of the receiver was a parametric amplifier with an excess temperature of 200°K. Simultaneous measurements with a 5 Mc/s bandwidth showed the existence of ionized hydrogen associated with the clusters.
The magnetic field of the Galaxy determined from the zeeman splitting of the 21-cm hydrogen line
Authors: Davies R. D.
Published: July 2016

The Zeeman effect can be used to measure directly the longitudinal component of the magnetic field in interstellar neutral hydrogen clouds. The frequency separation between the two circularly polarized components is 28 c/s for 10–5 G and can be inferred from measurements of the intensity difference between left- and right-hand circular polarization as a function of frequency. Earlier experiments at Jodrell Bank showed that the mean field in the interstellar medium was less than 10–5 G (Davies et al. 1960). Recent work using more sensitive techniques has provided a positive measurement of a weak general magnetic field and of fields of varying intensity in different interstellar clouds.
An outline of the spiral structure of the Southern Milky Way
Authors: Bok B. J.
Published: July 2016

It has become clear in recent years that the spiral features of our Galaxy — like those of all galaxies — are of recent origin and are presumably short-lived phenomena. To trace them optically, we need to confine ourselves to concentrations in the interstellar gas and to stars and star groupings recently formed from these. We are hence limited primarily to OB associations and star clusters in which the earliest spectral types for the stars are not later than B2, preferably O5 to B1. It is most important that radial velocities be measured for a fair sampling of these stars, especially so for directions in which the radial velocity effects due to galactic rotation vary appreciably with distance. Radial velocities of the stars in question and those found from interstellar absorption lines are not only useful as indicators of distance, but they are very much needed for the identification of star groups and their associated HI clouds, found by 21-cm techniques. They assist also in the study of HII regions, which can now be located by either radio or optical methods.
Recent observations at dwingeloo of the central region of the Galactic System
Authors: Oort J. H.
Published: July 2016

The work reported on was done by G. W. Rougoor and is based on observations made with the Dwingeloo dish and the eight-channel receiver built by Professor Muller.
High-resolution observations of the galactic centre at 1420 Mc/s in the continuum and in the neutral hydrogen line
Authors: Ryzhkov N. F. , Egorova T. M. , Gossachinsky I. V. , Bystrova N. V.
Published: July 2016

The large Pulkovo radio telescope has a beamwidth of 7 min of arc in R.A. at a frequency of 1420 Mc/s. The continuum emission from the source Sagittarius A was measured with a bandwidth of 5 Mc/s. The mean drift curve is shown in Figure 1. It can be separated into components according to Drake (1959) as indicated in the figure. The galactic ridge is also shown. The right ascension, the antenna temperature, the observed angular diameter, and the flux density of each component are given in Table 1. The errors given in the table can be somewhat higher in the case of components 2 and 3 because of the difficulties of separating them. The calibration of the antenna and receiver was made using the flux densities of the sources IAU 19N4A, 05N2A, 05S0A, and 18S1A according to Westerhout (1958) with the corrections given by Altenhoff et al. (1960). The atmospheric extinction at λ = 21 cm was taken from these works as well.
Continuum radio emission from the Magellanic Clouds
Authors: Mathewson D. S. , Healey J. R.
Published: July 2016

Before discussing the results of the radio observations of the Magellanic Clouds in detail, it is worth while to briefly review some of our current ideas about radio emission from “normal” galaxies which would be the classification given to the Clouds by radio astronomers. A “normal” galaxy has no striking visual peculiarity and has a much lower ratio of radio to light flux than the “radio” galaxy.
Optical evidence on the kinematics of the Magellanic Clouds
Authors: Feast M. W.
Published: July 2016

Some while ago radial velocities were published for 112 stars in both Magellanic Clouds from Radcliffe Cassegrain spectrograms (Feast, Thackeray, and Wesselink 1960).
Photoelectric spectrophotometry of emission nebulosities in the Magellanic Clouds
Authors: Dickel H. R. , Aller L. H. , Faulkner D. J.
Published: July 2016

Photometric measurements of the emission nebulosities in the LMC are not numerous. Doherty, Henize, and Aller (1956) microphotometered both widened and unwidened objective-prism photographs covering a narrow wavelength range near Hα to obtain cross-sectional “intensity profiles” for certain nebulosities in the Large Cloud. These intensities were converted to surface brightnesses by tracing the widened spectra of stars of known magnitude and colour and using the method of Ambartsumian (1933). Peak intensities for each scan across a nebulosity are given in erg cm–2 sec–1 steradian–1.
A comparison of the 30 Doradus and η Carinae nebulae
Authors: Faulkner D. J.
Published: July 2016

The program of observations of the 30 Doradus and η Carinae nebulae described here had its origin in the general study of Magellanic Cloud nebulae considered in the previous paper. The 30 Doradus nebula is considerably larger and brighter than the other HII regions in the Clouds, and may be treated in greater detail. The η Carinae nebula was chosen as a comparison object in our own Galaxy.
Supergiants in the Magellanic Clouds and in the Galaxy
Authors: Walraven Th. , Walraven J. H.
Published: July 2016

With the five-colour photometer of the Leiden Southern Station (system V, B, L, U, W) stars can be classified according to luminosity (Th. Walraven and J. H. Walraven 1960).
The wing of the Small Magellanic Cloud
Authors: Westerlund B. E.
Published: July 2016

It is important to study some of the less bright and less rich clusters in the Magellanic Clouds in order to complete the picture of their populations as derived from studies of their giant clusters and associations. The region around NGC 419 in the Small Cloud is fairly rich in small- and medium-sized blue clusters and has, in addition, a photoelectric sequence (Arp 1958). Several clusters and groups of stars in this region have now been investigated (Westerlund, unpublished data). The resulting colour-magnitude arrays for four clusters in this region are presented in Figure 1 together with the arrays for three clusters in the wing. The clusters are identified by their numbers in Kron's (K) or Lindsay's (L) catalogues (Kron 1956; Lindsay 1958).
Photoelectric observations of Magellanic Cloud cepheids
Authors: Gascoigne S. C. B.
Published: July 2016

This is a brief account of some photoelectric observations of Magellanic Cloud cepheids, begun in 1951 with Dr. G. E. Kron on the 30-inch reflector, and since continued there and on the 50- and 74-inch reflectors. The initial emphasis was on colour, the Cloud cepheids, as measured, being considerably bluer than those in the Galaxy. It is now known that this discrepancy is due mostly to reddening of the galactic cepheids, and interest has shifted rather to the differences in the period-luminosity relations in the two Clouds, as revealed by measurements made in the SMC by Arp (1960), and in the LMC by Woolley et al. (1962).
The occurrence of lithium in F5-G8 main-sequence stars
Authors: Herbig G. H.
Published: July 2016

The discovery that there is a major variation in the strength of the Li1λ6707 line among F and G dwarfs adds another classification parameter in this region of the H-R diagram. (We do not consider here the Li situation in stars of higher luminosity.) But the immediate question is: What is the physical significance of this dispersion in lithium content? The details are now in press (1), but here we review the evidence to the effect that the lithium abundance, at least in G stars, can be considered as an index of evolutionary age.
Note on the spectral classification of carbon stars in the photographic infrared region
Authors: Fujita Y.
Published: July 2016

We have investigated the spectrograms (dispersion: 8Å/mm) in the photographic infrared region fromλ7500 toλ9000 of some carbon stars obtained by the coudé spectrograph of the 74-inch reflector attached to the Okayama Astrophysical Observatory. The names of the stars investigated are listed in Table 1.
An equivalent-width study of Harper and Young's luminosity ratios for late-type stars
Authors: Wright K. O. , Jacobson T. V.
Published: July 2016

Equivalent widths of lines used by Harper and Young (1) for determining absolute magnitudes of late-type stars have been measured on plates of the same dispersion as that used by Harper and Young (30Å/mm at Hγ) and on grating plates of high dispersion (3–5Å/mm). It was hoped that the large spread in Harper and Young's luminosities for the different line ratios for each star (sometimes 5mor more) might be reduced when quantitative measures were made although it was realized that some of the scatter might be inherent in the star (differences in composition etc.). However, on the 30Å/mm dispersion, most of the lines are quite badly blended and the equivalent widths include both lines sensitive to absolute magnitude and others not necessarily so. Therefore the mean values for the several line ratios for the two or three low-dispersion plates of each star show considerable scatter when plotted against Johnson and Morgan's MK luminosity classes and also against the Harper and Young data; the results seem to be no better than the data obtained from Harper and Young's eye estimates. This confirms the statement often made that on homogeneous sets of plates of comparable density, where lines are close together in wavelength, the eye can detect small differences as well as, or better than, the microphotometer. The high-dispersion measures have not been completed but it is most probable that, since individual “sensitive” lines can be measured, the results will be considerably improved. Some of Harper and Young's ratios are not specially suitable and it is probable that a few selected line ratios such as 4071/4077, 4215/4250, 4247/4250, and possibly 4233/4236 are just as satisfactory for luminosity classification as the more numerous data used by these authors. An extended report is in print (2).
Yttrium oxide in M- and S-type variable stars
Authors: Keenan P. C.
Published: July 2016

The spectroscopic data that are being collected for a catalogue of spectral types of M- and S-type Mira variable stars include estimates of intensities of several molecular bands. Since the stronger bands are scattered through various parts of the spectrum it is a slow task to collect observations that allow the different molecules to be compared at a given phase or cycle. Fortunately, the material from the Perkins reflector has been richly extended through the generous cooperation of the Mount Wilson and Palomar Observatories—particularly by the collaboration of Dr Deutsch—so that we can now begin to sketch the behavior of the chief bands.
Some problems on the classification of M, S and C-type stars
Authors: Fujita Y. , Yamashita Y. , Kamijo F. , Tsuji T. , Utsumi K.
Published: July 2016

Sixty spectrograms of 25 M-, S- and C-type stars obtained with the spectrographs attached to the 72-inch reflector of the Dominion Astrophysical Observatory, Victoria, have been analysed and the equivalent widths of some atomic lines and molecular bands have been measured.

The relation of C2Swan band and SiC2Merrill-Sanford band intensities with the C classification and of TiO, ScO, VO and YO band intensities with the M and S classification were investigated. The correlation between the temperature sequence of the spectral type M, S and C and corresponding sub-classification was discussed and the assignment of the C subtype equivalent to the M subtype with respect to the excitation temperature was tentatively tried. The relation of absolute intensities with the spectral type was also discussed.
Two-dimensional narrow-band classification of M stars
Authors: Gyldenkerne K. , Helt B.
Published: July 2016

The influence of TiO absorption in reducing the visual light of M giants in comparison with their blue and infrared radiation has been known for many years. The effect is clearly present in the six-colour photometry (1, 2), and in the (B–V) colours which are almost constant for M giants (3, 4); the latter result is used in galactic research. The deviation from black-body radiation has been studied in some detail by Gabovits (5) and by Dobronravin (6).
Photometric separation of temperature, reddening, and chemical composition
Authors: Williams J. A.
Published: July 2016

It is very difficult to separate the effects of interstellar reddening from the effects of temperature reddening and differences in chemical composition. In this paper I discuss several methods which have been used to make this separation. The application of the narrow-band system of Crawford (1), Table 1, to population I cepheids with periods greater than 13 days and the evidence from G–K giants that the system makes the separation are described in more detail.
A search for color systems of optimum performance
Authors: Seitter W.
Published: July 2016

The derivation of spectral types and luminosity classes of reddened stars from three (or multi-) color measurements and the evaluation of the amount of interstellar absorption are based on the knowledge of the reddening path in the two-color diagram orEshort/Elongand the ratioEcolor/Acolorrespectively. Numerous papers have been published both on the empirical and computational determinations of these ratios, the majority of theoretical papers being concerned with the broad bandUBVsystem and the consequent changes inEs/ElandEc/Acwith spectral type and varying amounts of interstellar absorption. Some observational investigations indicate the influence of interstellar absorption on the first of the two ratios to be negligible both for theUBVsystem and for narrow-band photometries. A computational re-investigation might help in solving the present discrepancies between the observational and theoretical results for theUBVsystem and give a better understanding of the behavior of narrow-band photometries for which the near constancy of both ratios has tacitly been assumed.
Luminosity effects in the ultraviolet light of supergiants and giants of type A, F and G
Authors: Walraven Th.
Published: July 2016

The simultaneous five-colour photometer of the Leiden Southern Station was constructed originally for the study of O–B type stars. The spectral bands of the photometer were chosen with the purpose of observing three parameters, i.e. the Balmer jump, the intensity of the Balmer lines and the gradient of the ultraviolet spectrum. The colour index is observed with bandsVandB, which with respect to the position correspond approximately to the same bands of theUBVphotometry. A third band,L, situated atλ3830 is influenced by the strength of the hydrogen lines and this effect is studied in the colour index (B–L). The bandsUatλ3620 andW, atλ3242 give information about the Balmer discontinuity and the ultraviolet gradient.
Calibration problems in hydrogen luminosities
Authors: Beer A.
Published: July 2016

The investigations which I should like to summarize in this paper concern recent photo-electric luminosity determinations of O and B stars. Their final aim has been the derivation of new stellar distances, and some insight into certain patterns of galactic structure.
Variations of Interstellar Ultra-Violet Absorption
Authors: Isobe Syuzo
Published: July 2016

It is shown that mixtures of graphite core-ice mantle grains with large and small mean size and graphite grains provide good fits to the observed interstellar extinction curve.
The Ratio of Total to Selective Extinction from the Cluster Diameter Method
Authors: Harris Daniel H.
Published: July 2016

One hundred and fifty six open clusters with modern photometry, and apparent diameter measures by Trumpler, have been used to measure the mean ratio of total to selective extinction, R̄ It is found that cluster diameter is related to both concentration class and richness class. Diameter also seems to depend on the background stellar density and to decrease with reddening. With such effects measured and removed R̄ = 3.15 ± 0.20. This result is not significantly dependent on the cluster's position in space.
A Kramers-Kronig Analysis of Interstellar Extinction
Authors: Chiao R. Y. , Feldman M. J. , Parrish P. T.
Published: July 2016

Integrals over the observed spectrum of interstellar extinction to 9 μm–1 are related to known laboratory properties of specific compounds. Using Lα hydrogen densities and cosmic abundance ratios, many suggested grain materials can be eliminated.