bluuebunny/crossref_metadata_2025 huggingface dataset:
A Spectrographic Study of the Shell Star EW Lac
Authors: Scholz G.
Published: July 2016

38 Zeeman spectrograms of the Be star EW Lac (HD 217050) were obtained in three successive years, 1978, 1979 and 1980. The investigated lines show long-time variations of the radial velocities, line widths, and line intensities. No hints at the occurrence of a global magnetic field larger than 150 Gauss were found.
R81: P Cygni of the LMC
Authors: Stahl O. , Wolf B. , de Groot M.J.H. , Sterken C.
Published: July 2016

Extensive photometric UBV observations and spectroscopic high dispersion (20 Å/mm and 38 Å/mm) coudé observations of the very luminous (Mv = −8.2) B2.5 eq supergiant R81 of the LMC were carried out between 1970 and 1980 at ESO, La Silla. In addition the IUE satellite was used to obtain a high resolution (0.2 Å) spectrogram in the ultraviolet wavelength range 1200 < λ < 1950 Å. The most prominent features of the visual spectrum are P Cygni profiles of the Balmer lines, indicating a shell with an expansion velocity of about 140 km s−1. The ultraviolet spectrum of R 81 is dominated by blue-shifted absorption resonance lines (Si II, Si IV, C II, C IV, Al III etc.) and Fe III absorption lines originating from metastable lower levels. From the UV resonance lines a very high mass loss rate (M = 5 10−5 M⊙ yr−1) was estimated. The early Balmer lines show very broad shallow emission wings (total width 40 to 50 Å), attributed to electron scattering. The mass loss is highly variable and presumably occurs in the form of sudden ejections of discrete shells. Irregular brightness variations of a few tenths of a magnitude in V on timescales of weeks were found. An absolute bolometric magnitude Mbol ≈ −10 and a photospheric radius R ≈ 70 R⊙ were estimated. A comparison with theoretical evolutionary tracks indicates a stellar mass M > 50 M⊙. The observed spectroscopic properties lead us to suggest that the LMC star R 81 is a close counterpart of the galactic star P Cyg, representing a short lived transient stage in the evolution of the most massive stars.
Le Spectre des Etoiles Oe dans le Rouge et le Proche Infrarouge
Authors: Andrillat Y. , Vreux J. M. , Dennefeld M.
Published: July 2016

Among the 0 stars, Conti and Leep (1974) define the Oe class as those stars showing emission in the hydrogen lines but without emission in N III or 4686 He II.

In the blue-red region, aside from the presence of Lambda 4542 in absorption, the overall appearance is similar to Be stars. So far no Oe star has been observed until 1.1 μ: the aim of this paper is to fill this gap. We present observations of Oe stars in the near infra-red region as well as new observations of Hα profiles.
Introductory Talk: Bibliography of Be Stars
Authors: Koubský Pavel
Published: July 2016

As you know the first list of bibliography on Be stars was published in the second Be Star Newsletter. Six contributors are trying to cover the production of papers in the field. No doubt that the bibliography is very useful and I am very glad that Dr. M. Jaschek has offered the Newsletter for this purpose and that she is acting as the editor of the bibliography.
Rotation, Expansion and Duplicity of Be Stars
Authors: Harmanec Petr
Published: July 2016

In recent years there is a general tendency to divide Be stars into different groups. Bidelman's (1976) division on supergiants, rapidly rotating single stars, interacting binaries, early type nebular variables and quasi (or young) planetary nebulae is often quoted. Another example is the classification by Lesh (1968) or a very recent classification by Jaschek et al (1980), limited a priori to “normal” Be stars i.e. stars of luminosity classes V to III. I do not think such an approach is recommendable. There is still no general agreement as to the nature of the Be phenomenon and all such classifications must be more or less descriptive. The possibility that the hydrogen emission observed in the spectra of apparently very different objects has always the same physical cause, and that the differences between these objects are caused only by continuously varying physical and/or geometrical parameters should seriously be considered, along with all other concepts. At the moment, I find it more promising to study Be stars in context of all early type emission objects, including supergiants, P Cyg stars, Beta Cep objects, WR stars, symbiotic stars and novae. Such a viewpoint is not new – it was expressed already by Struve (1942).
Determination of the Inclination of Rotational Axes and Rotational Velocity from the Line Profiles of Rotating Stars
Authors: Ruusalepp M.
Published: July 2016

For a grid of rotating hot stars the computed line widths at the half maximum depth for the lines HeI λ 4471 and MgII λ 4481 are given. Based on the correspondent observational data the inclination of the rotational axes i and the reduced rotational velocity w have been found for 19 B and Be stars.
Radial-Velocity and Photometric Variations of o and: Critical Evaluation of Possible Periods
Authors: Horn J. , Koubský P. , Arsenijevič J. , Grygar J. , Harmanec P. , Krpata J. , Kříž S. , Pavlovski K.
Published: July 2016

The bright Be star o And has been observed for over 90 years. Throughout this time numerous observers detected highly variable spectrum, photometric changes and substantial range of radial velocity of this star. Much effort has been devoted for period searching in these data. In the present study we collected all available (to our knowledge) radial velocities and photometric measurements in the visible region and tried to evaluate the reported periodicities.
Mass Loss from π Aquarii
Authors: de Freitas Pacheco J.A.
Published: July 2016

Fe III lines from metastable states have been detected in the UV spectrum of π Aqr (HD 212571). The line profiles are asymmetric and they are probably formed in a expanding envelope. From the observed fine widths and using the Sobolev approximation we have derived a mass loss rate of about 2.5 × 10−9M⊙ y−1.
Gross Structural Pattern for the Atmospheres of Be, and Some Closely Related, Stars
Authors: Doazan V. , Stalio R. , Thomas R. N.
Published: July 2016

Abstracted comparison of Struve's 1942 quasi-empirical model of the shell-atmosphere of Be and similar stars, based on visual data and quasi-radiative equilibrium, to that demanded by current visual+nonvisual data, requiring nonradiative+mass fluxes characterized by variability and individuality.
Theoretical Surface Brightness Distributions and Continuum Polarization of Rapidly Rotating B Stars
Authors: Sonneborn George
Published: July 2016

In order that a rotating star be in hydrostatic and radiative equilibrium, the effective temperature of the stellar atmosphere must decrease between the star's poles and its equator. Wavelength differences in this “gravity darkening” have been suggested to account for the observed differences in the rotational broadening of lines in the ultraviolet and visual spectral regions (hutchings, 1976; Sonneborn and Collins, 1977). This paper investigates the problem, using detailed model atmospheres to examine the surface brightness distribution of a rapidly rotating star.
On the Spectrum of the Herbig Be Star HD 200775
Authors: Baschek B. , Beltrametti M. , Köppen J. , Traving G.
Published: July 2016

On the basis of high-dispersion spectra (I. Appenzeller, C. Bertout) and other observational material HD 200775 has been reanalyzed using ι Her as a comparison star. By comparing the depths in the wings of Hγ and Hδ and the equivalent widths of HeI-lines with predictions from model atmospheres we find for both stars Teff = 17000 ± 1000 k (in the scale of Kurucz' models, 1979) and log (g cm s−1) = 3.6 ± 0.3 corresponding to a spectral type of B3V. With a colorexcess EB-V = 0.56 and the standard interstellar reddening also the continuum energy distribution of HD 200775 corresponds to the above photospheric parameters if one allows for some circumstellar emission. However, the interstellar absorption features (4430 A and 2200 A) are of unusual weakness. The strength of the Hα emission requires either a nonthermal source of energy or a substantial rate of photo ionization from the level n = 2. We tend to conclude that for this second reason the dilution factor in the HII-region cannot be less than 10−2, a conclusion which is in accord with the finding that the radio emission at λ = 2 cm is less than 0.3 mJ which also indicates a very compact HII-region.
Kinematics of the Galactic Globular Cluster System
Authors: Webbink R. F.
Published: July 2016

Constraints on cluster kinematics proper motions, radial velocities and tidal radii are reviewed. Analysis of the cluster radial velocity distribution suggests a rotation law for the system in which the specific angular momentum is nearby independent of galactocentric distance, and the residual velocity dispersion is isotropic. However, the absence of severely tidally truncated clusters indicates that nearly radial orbits are absent from this distribution. The kinematic properties of the remote halo clusters remain largely indeterminate. Absolute proper motions measured directly with respect to background galaxies and quasars are needed to determine the kinematics of these objects, and also to elucidate the process of tidal stripping.
Old Globular Clusters in the Magellanic Clouds
Authors: Graham J. A.
Published: July 2016

The old globular clusters in the Magellanic Clouds are important links between our understanding of globular clusters in our own galaxy and similar unresolved objects in more distant galaxies. The Cloud clusters spread over a large range in age. Several contain RR Lyrae variable stars. High weight abundance data are needed for individual cluster members as well as deeper color-magnitude diagrams.
M 31 Cluster System
Authors: Pecci F. Fusi
Published: July 2016

The present status of the search for globular clusters in M31 is reviewed and some outstanding properties of the cluster system as a whole are briefly discussed.
Surface Photometry of Globular Clusters
Authors: Djorgovski S.
Published: July 2016

Much of what we know about the structure, dynamics, and evolution of globular clusters derives from their observed density profiles, and their interpretations. In this review, I will briefly describe the problems and techniques specific to the surface photometry of globular clusters, show some new results, and offer suggestions for future ground-based work.
Globular Cluster Systems in Galaxies: Main Trends and Future Directions
Authors: van den Bergh Sidney
Published: July 2016

This was a really exciting conference! The main problem in summarizing it is that so many new and important results were presented, making it impossible to mention each one individually. In reviewing this conference I shall first discuss new results, then problem areas revealed by papers and during discussions and finally desiderata and trends for future work.
The Metal Abundance of Metal-Rich Globular Clusters
Authors: Gratton Raffaele , Quarta Maria Lucia , Ortolani Sergio
Published: July 2016

We think that it is possible to find the correct scale of abundance for metal-rich globular clusters thanks to the new generation of spectrographs, equipped with CCD cameras. We analyzed giants in ten globular clusters and Arcturus using high dispersion spectra acquired through the CASPEC spectrograph at the 3.6 m telescope at La Silla. The detector was an RCA CCD. Stars cooler than 4150 K were avoided since their absorption spectrum is too strong. By a comparison with standard Arcturus spectra, we found a small trend to overestimate equivalent widths. This systematic error affects the derived abundances only marginally. However, too large equivalent widths must produce too large metal abundances. Abundances were derived following a standard procedure.
The Composition of Warm Giants in M 71 and M 5
Authors: Pilachowski Catherine A. , Sneden Christopher
Published: July 2016

In 1979 a disturbing controversy arose in the field of globular cluster research when Cohen (1980) and Pilachowski, Canterna, and Wallerstein (1980) announced the results of the first high dispersion studies of the composition of giants in the globular clusters M 71 and 47 Tucanae. In contrast to earlier studies, which found metallicities of typically −0.3 and −0.5 dex, these investigators obtained values of −1.3 and −1.1. Since then, many have attempted to redetermine the abundances of M 71 and 47 Tuc to explain the discrepant results. These efforts have all suffered from the absence of high signal-to-noise, high resolution spectra of stars with temperatures above 4300 K.
Bimodal Distributions on the Horizontal Branch
Authors: Rood Robert T. , Crocker Deborah A.
Published: July 2016

We present preliminary versions of log g - log Teff diagrams for a number of clusters with gaps in their blue horizontal branches and for two normal clusters.
Apparent Rotation of the Galactic Globular Cluster System
Authors: Colin J.
Published: July 2016

We use the radial velocities of galactic globular clusters, corrected for solar motion to calculate their apparent angular momentum. Comparing the apparent angular momentum with a numerical simulation we show, with 90% confidence, that the globular cluster system is in prograde rotation. The distribution of angular momentum with Fe/H reveals three distinct groups of clusters with different kind of rotation:

1) 19 clusters with Fe/H > −0.8 have a solid-body rotation in the direct sense.

2) 33 clusters with −1.75 < Fe/H < −0.8 do not exhibit any rotation (80%. confidence).

3) 27 clusters with Fe/H < −1.75 have a uniform rotational velocity in the direct sense (90% confidence).
A Search for Globular Cluster Candidates in NGC 2403
Authors: Malagnini M. L. , Santin P. , Bonoli F. , Frederici L. , Pecci F. Fusi , Kron R. G.
Published: July 2016

A complete search on KPNO 4-m plates has been undertaken in order to determine the whole observable part of the cluster luminosity function of the late-type spiral galaxy NGC 2403. Automatic procedures have been used for object detection and analysis, and then selection criteria, based on geometric and photometric properties, have been applied in order to define the sample of cluster candidates.
Search for Globular Clusters in Nearby Galaxies II. NGC 3109
Authors: Blecha A.
Published: July 2016

We report on the search for globular clusters around NGC 3109, a SB(s)m nearby galaxy using observations taken with the wide field telescope at La Silla. Clusters are discriminated by using the advanced image processing software (MOAN). From 320 objects, 23 candidates are retained. Their luminosity function peaks at mv − 19.8, thus giving the distance of the parent galaxy as 2.13 Mpc. The radial distribution follows the Dp1/4 law well. The total number of clusters is estimated at 40 ± 25 and the specific frequency Sv = 3 clusters per Mv = −15.
Spatial Distribution of Globular Clusters in M 31
Authors: Watanabe Jun-Ichi , Yamagata Tomohiko
Published: July 2016

The spatial distribution of globular clusters in M 31 has been analyzed using the catalogues of Sargent et al. (1977) and Crampton et al. (1985). It is concluded that the globular clusters within the distance of 54′ from the center of M 31 show an elliptical distribution aligned to the major axis of the disk. This is similar to the distribution of metal-rich clusters in our galaxy.
Ellipticities of Globular Clusters in the Andromeda Galaxy
Authors: Spassova Nedka M. , Staneva Anelia V. , Golev Valery K.
Published: July 2016

A program of investigation of globular clusters' structural parameters in nearby galaxies has been initiated at the Rozhen National Observatory, Bulgaria (Spassova and Staneva 1984). Here we report on the projected ellipticities of 88 bright globular clusters in M 31, obtained on plates taken with the 2 m Ritchey-Chretien telescope at Rozhen (16 m focal length, 12″89/mm plate scale over a 1° × 1° field).
CCD Photometry in the Core of the Fornax Dwarf Galaxy
Authors: Light Robert M. , Seitzer P.
Published: July 2016

The present study is concerned with the examination of properties of stars in the core of the Fornax dwarf spheroidal galaxy. Previous studies have shown that Fornax has a very diverse stellar population. Four of the globular clusters associated with Fornax were found to have metallicities significantly lower than the mean metallicity of the field population of the galaxy (Buonanno et al. 1985); these clusters point out an older, metal-poor population. Also, there are a number of luminous carbon stars, which are indicative of a much younger population (see Mould and Aaronson 1986). Studies of the field population of Fornax (Demers, Kunkel, and Hardy, 1979; Buonanno et al., 1985) have shown a dispersion in metallicity. We have measured a large sample of giant branch stars, enabling a good determination of mean properties of the Fornax stellar population, as well as allowing a comparison of stars as a function of distance from the center of Fornax.
Double-Mode RR Lyrae Stars in IC 4499
Authors: Clement Christine M. , Nemec James M. , Dickens Robert J. , Bingham Elizabeth A.
Published: July 2016

Thirteen double-mode RR Lyrae (RRd) stars, with mean magnitudes c = 18.30 ± 0.10 and c = 17.80 ± 0.15, have been identified in the variable-rich Oosterhoff type I globular cluster IC 4499. The stars have surprisingly uniform properties, and are considerably different from RRd stars found in Oo II systems. The mean first-overtone period (Fig.1) is =0.357d ± 0.005d (cf. =0.40d for Oo II RRd stars), and the mean ratio of the first-overtone period to the fundamental period is = 0.7443 ± 0.0002. The mean double-mode pulsation mass for the 13 stars, using the King Ia (Y=0.279, Z=0.001) mass calibration, is 0.535 ± 0.003 M⊙. Such an average mass is 0.11 M⊙ smaller (i.e. ~17% smaller) than that for RRd stars found in Oo II systems, and possibly ~0.01 M⊙smaller than the mean mass for the two RRd stars in M3 (it is important to note that the zero point of these mass determinations is uncertain by at least 15%). The metal abundances for the RRd stars, and for the system of RR Lyrae stars as a whole, are found to be consistent with <[Fe/H]>=-1.38 ± 0.20, determined from δS spectroscopy. In the Peterson diagram (Fig.2), all known RRd stars now divide (apparently by mass) into two groups (split according to Oosterhoff type). With a reddening of EB-V=0.26 ± 0.03, the cluster distance modulus is (m-M)o=16.23m ± 0.23m.
The Core of the M 87 Globular Cluster System
Authors: Lauer Tod R. , Kormendy John
Published: July 2016

We have observed the central distribution of globular clusters in M 87. The core radius of the cluster system is an order of magnitude larger than that of the underlying galaxy.
Globular Clusters in Different Types of Spiral Galaxies
Authors: Harris Hugh G. , Bothun Gregory D. , Hesser James E.
Published: July 2016

Studies of globular clusters in spiral galaxies are still available for only a few galaxies with a limited range of galactic types. We have identified (or set upper limits on) the cluster systems in several edge-on spirals ranging from the early-type spiral NGC 7814 to the late type NGC 5907. We discuss the properties of the cluster systems and their relationship to the properties of the parent galaxies.
Globular Clusters as Extragalactic Distance Indicators: Maximum Likelihood Methods
Authors: Hanes David A. , Whittaker Donna G.
Published: July 2016

We have explored the use of maximum likelihood estimation techniques in the use of globular cluster luminosity functions (LFs) as distance indicators. In particular, we have tested size-of-sample effects through the analysis of Monte Carlo simulations of LFs drawn from an assumed universal population like that characterizing the globular clusters in the Local Group. Our working assumption, following others before us, is that the underlying LF is adequately well described by a Gaussian normal in a number vs. absolute magnitude representation.

For typically observable sample sizes in studies which are limited to the bright half of the LF, statistical limitations preclude a precise determination of the attributes which fully describe the LF, even in the absence of field object contamination. In particular, the intrinsic dispersion (the shape parameter of the LF) must be taken to be a universal constant, independent of galaxy type; only then may the turnover magnitude (which contains the distance information) be derived with good precision. Some data exist for nearby galaxies (including ellipticals) which permit an assessment of the universality of the intrinsic dispersion: they are not inconsistent with the hypothesis. However, it will be important to test this point in future as more data are secured.

Real globular clusters in remote galaxies are unresolved, and the samples are contaminated with foreground field stars and remote background objects. This contamination necessitates corrections which are statistical in nature, applicable to binned LFs. Through numerical simulations, we have tested the limitations imposed by realistic numbers of field objects in globular cluster LFs in remote galaxies, testing for systematic biases and assessing the attainable precision in derived distance as a function of the sample size and the limiting magnitude.
Photographic Phtotometry of 4500 Stars in M 30
Authors: Piotto G. , Capaccioli M. , Ortolani S. , Rosino L. , Alcaino G. , Liller W.
Published: July 2016

We present B and V photometry of ~ 4500 stars (V < 21.3 mag) within the region 2′.1 < r < 10′ centered on the southern globular cluster M 30 (NGC 7099), from two sets of four plates of the 4 m CTIO (CT) and the 2.5 m Dupont (LC) telescopes (Piotto 1986). Instrumental magnitudes (applying INVENTORY to PDS scans) are calibrated by four CCD exposures from the ESO 1.5 m Danish telescope. Our results removed the disagreement between previous photometry (Alcaino and Liller 1980) and the isochrones published by VandenBerg (1983).
A Survey of Globular Cluster Velocity Dispersions
Authors: Pryor Carlton , McClure Robert D. , Fletcher J. M. , Hesser James E.
Published: July 2016

We have used the Dominion Astrophysical Observatory radial velocity spectrometer on the 3.6m Canada-France-Hawaii telescope to obtain radial velocities, accurate to ~0.8 km/s, for ~20 stars in each of nine globular clusters. The stars are generally within three core radii of the cluster center. The cluster names and metallicities (the latter are averages of values in Zinn and West (1984), Pilachowski (1984), and Webbink (1985)) are given in Table I. This sample includes two clusters with cusps in their surface brightness profiles: NGC 6624 and 6681.
Anisotropy in ω Centauri and 47 Tucanae
Authors: Meylan G.
Published: July 2016

The southern sky gives us the great opportunity to observe two among the brightest and nearest globular clusters of the Galaxy: ω Cen and 47 Tuc. For these giant clusters, we present the comparison between observations and King-Michie multi-mass dynamical models with anisotropy in the velocity dispersion. A more comprehensive description of this work is to be published (Meylan 1986a,b).
Evidence for Mass Segregation in NGC 5466
Authors: Nemec James M. , Harris Hugh C.
Published: July 2016

Forty-eight blue straggler stars have been discovered in NGC 5466, the only Galactic globular cluster known to contain an anomalous Cepheid of the sort found in dwarf galaxies. The stars were identified in color-magnitude diagrams constructed from photometry of deep photographic plates taken with the Canada-France-Hawaii 3.6 m telescope (calibrated with new UBV photoelectric photometry), and from point spread function photometry of CCD frames taken with the Palomar 5 m telescope. The stars typically have magnitudes  ~ 19.m1 and colors  ~ 0.m2. Forty-two of the 48 stars are situated inside of R=2.5 arcmin (see Fig.1), the projected radius containing half the cluster luminosity, and only six stars are found between 2.5 and 9 arcmin. A one-sided, two-sample Kolmogorov-Smirnov test (using the CCD data) establishes at the 98% significance level that the blue stragglers are more centrally concentrated than the subgiant stars of the same magnitude. By fitting multi-component King models to the projected radial distributions (Fig.2), the mean mass of the blue stragglers is shown to be ~1.5 to two times larger than the masses of the stars that contributed the light from which the core and tidal radii were derived (i.e. M (Blue Str.)=1.3±0.3 M⊙). Because the central relaxation time for NGC 5466 is much less than the cluster age, the different radial distributions are attributed to mass segregation. A similar mass segregation is also observed in the globular cluster NGC 5053, where Nemec and Cohen (1986, in preparation) have recently identified ~30 blue stragglers. The low stellar density and small escape velocity of NGC 5466 make a recent epoch of star formation (during which the blue stragglers might have formed as massive single stars) seem unlikely. Instead, the blue stragglers probably are either close binary systems that have transferred mass, or are coalesced stars. The very low frequency of stellar collisions expected in the center of NGC 5466 suggests that the blue stragglers are primordial binary systems. The simultaneous presence in NGC 5466 of the blue stragglers and the anomalous Cepheid V19, and their relative numbers, supports the hypothesis that there is an evolutionary connection between the two types of stars. By fitting theoretical isochrones to the photographic c-m diagram, NGC 5466 is estimated to have an age of 18±3 Gyr.
Variability of ω Centauri Blue Stragglers: Clues to their Origin
Authors: Da Costa G. S. , Norris John
Published: July 2016

The four possible origins usually discussed for blue stragglers in stellar systems are (a) mass transfer in, or coalescence of, close binaries; (b) main sequence lifetime extension either through internal mixing or high non-thermal pressures; (c) complete mixing events in evolved stars at the core helium flash; and (d) ongoing star formation over long intervals. However, alternative (d) can be ruled out for the case of globular clusters because any residual gas in the cluster is very efficiently swept out as the cluster passes through the galactic disk, an event that occurs approximately every hundred million years. Hypotheses (a) and (b) both predict masses for the blue stragglers that exceed the turnoff mass but if alternative (c) is correct, then the blue stragglers should have masses less than or equal to the turnoff mass.
Asteroid Albedos and Diameters
Authors: Tedesco Edward F.
Published: July 2016

This paper discusses the status of our knowledge regarding asteroid sizes and albedos. It presents a brief discussion of the methods used to determine sizes and albedos beginning with attempts using filar micrometers as early as 1802 and culminating with the 1993 publication of the IRAS Minor Planet Survey. It addresses the completeness and reliability of the IRAS Minor Planet Survey, summarizes the statistical adjustments made to the derived results, and considers the implications of those results.
Zodiacal Dust Bands
Authors: Dermott S. F. , Durda D. D. , Gustafson B. A. S. , Jayaraman S. , Liou J. C. , XU Y. L.
Published: July 2016

One of the outstanding problems in solar system science is the source of the particles that constitute the zodiacal cloud. The zodiacal dust bands discovered by IRAS have a pivotal role in this debate because, without doubt, they are the small, tail end products of asteroidal collisions. Geometrical arguments are probably the strongest and the plane of symmetry of the dust bands places their source firmly in the asteroid belt. A cometary source, Comet Encke for example, could exist at the distance of the mainbelt, but the dynamics of cometary orbits makes the formation of cometary dust bands impossible, unless, of course, there is a significant (comparable in volume to the asteroidal families) source of comets interior to the orbit of Jupiter with low (asteroidal) orbital eccentricities. We have suggested that the dust bands are associated with the prominent asteroidal families. The link with the Themis and Koronis families is good but the link with Eos remains to be proved. We show here by detailed modeling that even though the filtered infrared flux in the 25μm waveband associated with the dust bands is only ~1% of the total signal, this is only the “tip of the iceberg” and that asteroidal dust associated with the bands constitutes ~10% of the zodiacal cloud. This result, plus the observed size-frequency distribution of mainbelt asteroids and the observed ratio of the number of family to non-family asteroids allows us to estimate that asteroidal dust accounts for about one third of the zodiacal cloud. The discovery of the “leading-trailing” asymmetry of the zodiacal cloud in the IRAS data and our interpretation of this asymmetry in terms of a ring of asteroidal particles in resonant lock with the Earth is important for two reasons. (1) The existence of the ring strongly suggests that large (diameter ≥ 12μm) asteroidal particles (or particles with low orbital eccentricities) are transported to the inner solar system by drag forces. (2) The observed ratio of the trailing-leading asymmetry allows an independent estimate of the contribution of asteroidal particles to the zodiacal cloud. These new results have important implications for the source of the interplanetary dust particles (IDPs) collected at the Earth. Because asteroidal particles constitute about one third of the zodiacal cloud and are transported to the inner solar system by drag forces, gravitational focussing by the Earth that results in the preferential capture of particles from orbits with low inclinations and low eccentricities and the possible “funneling” effect of the ring itself, imply that nearly all of the unmelted IDPs collected at the Earth are asteroidal.
Meteoroid Properties from Photographic Records of Meteors and Fireballs
Authors: Ceplecha Zdeněk
Published: July 2016

Statistical criteria based on the single-body theory enabled the distinction of different composition groups of meteoroids in the past. The new single-body model proposed by Pecina and Ceplecha (1983, 1984) is capable of determining the individual values of ablation coefficients, which has proved to be a better tool for separating meteoroids of different ablation properties. However, a significant fraction of fireballs exhibit a time-dependence of residuals, when the single-body model is applied to their photographic observations. This was recently explained by assuming sudden fragmentation at a point (gross-fragmentation). The proposed gross-fragmentation model was checked in exceptional cases, when splitting of a fireball was directly visible on the photographs. The new fragmentation model was then applied to the best photographic records of Prairie Network fireballs (PN). Least-squares fit of computed to observed distances along a meteoroid trajectory determines uniquely the ablation coefficient, the shape-density coefficient, the position of the gross-fragmentation point and the amount of fragmented material relative to the main body mass. This enabled not only a better classification according to ablation coefficient (composition groups), but also a recognition of different strength categories according to dynamic pressure at the fragmentation point. Except for composition groups (types) I, II, IIIA, IIIB, each meteoroid with precise photographic data on its fireball can be classified as NF (no-fragmenting), 1F (with one point of fragmentation) and MF (with many points of fragmentation). The fragmenting meteoroids (1F and MF) can moreover be sorted into several categories (a, b, c, d, e) according to dynamic pressure at the fragmentation point. Thus the classification became two dimensional, separating meteoroid composition from structure. Values of ablation coefficients and bulk-densities were revised using this model. The amount of fragmented mass relatively to the main body was also determined. Typical sudden fragmentation for almost half of all fragmenting meteoroids is equivalent to stripping away slightly more than half of the mass.
Dust Measurements in the Outer Solar System
Authors: Grün Eberhard
Published: July 2016

In-situ measurements of micrometeoroids provide information on the spatial distribution of interplanetary dust and its dynamical properties. Pioneers 10 and 11, Galileo and Ulysses spaceprobes took measurements of interplanetary dust from 0.7 to 18 AU distance from the sun. Distinctly different populations of dust particles exist in the inner and outer solar system. In the inner solar system, out to about 3 AU, zodiacal dust particles are recognized by their scattered light, their thermal emission and by in-situ detection from spaceprobes. These particles orbit the sun on low inclination (i ≤ 30°) and moderate eccentricity (e ≤ 0.6) orbits. Their spatial density falls off with approximately the inverse of the solar distance. Dust particles on high inclination or even retrograde trajectories dominate the dust population outside about 3 AU. The dust detector on board the Ulysses spaceprobe identified interstellar dust sweeping through the outer solar system on hyperbolic trajectories. Within about 2 AU from Jupiter Ulysses discovered periodic streams of dust particles originating from within the jovian system.
Iras Minor Planet Survey
Authors: Tedesco Edward F.
Published: July 2016

This chapter describes the contents and organization of the IRAS Minor Planet Survey Data Base and tells how to obtain hard-copy and machine-readable versions of the data.
MPC and ICQ Databases
Authors: Marsden B. G. , Green D. W. E. , Williams G. V.
Published: July 2016

Databases of astrometric and orbital data for minor planets and comets and of photometric data for comets are maintained in connection with the publication of the Minor Planet Circulars and the International Comet Quarterly. Aspects of these publications and the content and availability of these databases are discussed.
The Uppsala Comet Magnitude Database
Authors: Kamél Lars
Published: July 2016

The second part of the Comet Light Curve Catalogue/Atlas (CLICC/A) has been made available by anonymous ftp. This database contains magnitude estimates of periodic comets, reduced to a geocentric distance of 1 AU and corrected for observational effects. The database is described in some detail.
Meteoroid Orbits Available from the IAU Meteor Data Center
Authors: Lindblad B.A. , Steel D.I.
Published: July 2016

Since it was founded early in the 1980′s, the IAU Meteor Data Center (IAU MDC) has accumulated a large number of the meteoroid orbits measured worldwide so as to make these freely available to all interested researchers. The total number of orbits available is about 68,000, of which about 6,000 were determined using optical techniques (photographic or TV), the bulk having been detected using decameter radars. The observation sites range from various locations in the U.S.A., Canada, Australia, and in the former Soviet Union and Czechoslovakia; radar orbits from the Soviet Equatorial Expedition to Somalia are also archived. About 39,000 of the 62,000 radar orbits are derived from the Harvard Radar Meteor Project. Most of these programs were carried out during the 1960's and 1970′s, but still represent our best knowledge of the orbital distribution of interplanetary particles in the size range from 100 μm to 1 meter. A new survey currently in progress in New Zealand has so far rendered over 350,000 orbits, and it is anticipated that these will soon become available through the IAU MDC. Presently the 68,000 orbits archived in the IAU MDC are only available on magnetic recording media, but it is planned that they will shortly be made accessible via anonymous ftp.
5. A 21-cm. line survey of the outer parts of the Galaxy
Authors: Westerhout G.
Published: July 2016

In a strip 20° wide around the galactic equator, extending from l = 340° to l = 220°, line profiles were measured at 620 points. The interval in latitude was 2°·5, the longitude interval was 2°·5 from l = 340° to 110°, and 5° from l = 115° to 215°. At some longitudes the latitude range was extended to ±.
7. Progress report on the project in Radio Astronomy at the G. R. Agassiz station of Harvard Observatory
Authors: Bok B. J.
Published: July 2016

Two years ago I reported at the Jodrell Bank symposium on the initiation of the Agassiz Station project in Radio Astronomy. At that time the 24-ft. antenna was under construction and the electronic equipment for observation of the 21-cm. line of neutral hydrogen was being built by Harold I. Ewen, who is the co-director of the project. The first successful observations were obtained in the autumn of 1953 and reported early in 1954 (see Bok[1]). Since then two papers have been published giving the results of the first studies by Heeschen[2] and Lilley[3]; a report on the equipment and the basic programme was given by Bok and Ewen[4], Earlier this year, at the Princeton Meeting of the American Astronomical Society, Bok[5] drew heavily upon the Agassiz Station results in a paper entitled ‘Gas and Dust in Interstellar Clouds’, in which an attempt was made to blend the results of radio and optical research. We note also at this point a joint paper by Heeschen and Lilley[6] in which attention was drawn to the important role of Gould's Belt in the distribution of neutral hydrogen in the vicinity of the sun.
10. Radio observations of interstellar neutral hydrogen clouds
Authors: Lawrence R. S.
Published: July 2016

The detailed relationship between optical interstellar absorption lines and 21-cm. observations is investigated in this paper.

Dr Guido Münch, of the Mount Wilson and Palomar Observatories, provided the list of six intermediate-latitude stars shown in Table 1. The spectra of these stars all show complex absorption lines due to interstellar Ca 11. The 21-cm. line is measurable in four of the six regions, although the peak intensity is low in each case. It is noteworthy that for the first two stars on the list the radio velocity agrees closely with the velocity of an intense optical component. In view of the great difference in angular resolution, the failure to find correspondence in every case is not surprising.
12. The measurement of the distance of the radio sources
Authors: Davies R. D. , Williams D. R. W.
Published: July 2016

In radio astronomy it is becoming increasingly important to know the distance of the radio sources. An identification with astronomical objects observed optically is then more readily obtained and this in turn may allow further investigation of the mechanism of radio emission. A measurement of the distance of sources will also resolve the problem of their distribution in space, showing which are galactic and which are extra-galactic. Furthermore the surface area and absolute luminosity can be estimated from a knowledge of the distance and angular size of a source.
14. Comments on McClain's observations of IAU 17S2A
Authors: Edmondson F. K.
Published: July 2016

Reference to Fig. 1, p. 20 of this symposium will show that a 1° beam directed toward the galactic centre receives a range of velocities that is not negligible. This is due to galactic rotation, which causes material in one edge of the beam to approach and in the other edge to recede.
24. The 400 Mc./s. flux from Cassiopeia A
Authors: Seeger Ch. L.
Published: July 2016

The first trial of equipment designed for 400 Mc./s. absolute flux density measurement was completed just prior to this symposium. Using the midday sun, the gain of a 7·5 metre Würzburg (equipped with a TE°11 circular wave-guide feed) was found by comparison with an ‘optimum’ pyramidal horn of 20·2 square wave-lengths aperture. Cable losses and signal powers were measured against the available noise power from two co-axial resistors, one at ambient temperature and the other stabilized at the boiling-point of pure nitrogen.
31. Apparent intensity variations of the radio source Hydra A
Authors: Bolton J. G. , Slee O. B.
Published: July 2016

During the course of a survey for radio sources using a sea interferometer changes in the apparent intensity of the source Hydra A were observed. The intensities on two consecutive days differed by more than 30 % although the intensities of sources appearing earlier and later on the same records showed no significant changes. The position of this source given by Mills (1952) [2] is r.a. 09h 15m 46s, dec. − 11° 55′ (epoch 1950) and its I.A.U. number 09S1A.
32. Theoretical problems of discrete radio sources
Authors: Greenstein J. L.
Published: July 2016

The range of theoretical problems connected with the discrete sources is very large. It is convenient to distinguish between the normal and abnormal radio-frequency emitters that have quite different energy outputs per unit volume. Since the estimates by Minkowski and Greenstein [1] there has been considerable progress in the identification of these objects and in the provision of quantitative data about them. Table 1 includes revised estimates of the total luminosity, L, the emitting volume, V, and the luminosity per cubic parsec, J. Here L has been obtained by multiplying the observed power at 100 Mc./s. by an effective band-width of 500 Mc./s. and using the newly estimated distances. J is expressed in units of the total energy output of the sun (= 3·82 × 1026 watt) per cubic parsec. The figure for the Galaxy and M31 is considerably higher than that given by Baldwin in this symposium, since I have not revised the estimate of the emitting volume from the original paper by Minkowski and Greenstein. If most of the emission comes from a larger galactic halo the specific luminosity, J, for the Galaxy and M31 should be considerably reduced. For certain of the extra-galactic sources it is not certain whether the volume of the whole nebula, or only of the parts now in collision (or peculiar in nature, like the jet in M87) should be used in computing the specific emissivity, J. In Table 1, two values are then given.
34. Polarization and the radiating mechanism of the Crab nebula
Authors: Oort J. H. , Walraven T.
Published: July 2016

Photo-electric measurements made in Leiden in the first part of 1955 and extended by one of us at the Observatoire de Haute Provence in October 1955, show that the light of the Crab nebula is strongly polarized. The presence of polarization was first suggested by Vashakidze [2] and was firmly established by photo-electric measures by Dombrovsky [3] in 1954. The present observations, which are much more detailed, show that 17 % of the light coming from the central part, with a mean radius of 0′·8, is linearly polarized. It may be seen that over the entire bright part of the nebula the polarizations are sensibly parallel, while in the outer parts they tend to be oriented at random.
35. Optical emission from the Crab nebula in the continuous spectrum
Authors: Shklovsky I. S.
Published: July 2016

All conclusions concerning the nature of the Crab nebula up to the present have been based upon the interpretation of its continuous spectrum given by Baade and Minkowski in their well-known studies ([1, 2]; see also [3, 4]), It was suggested that its continuous emission is a thermal radiation caused by the extremely hot amorphous mass of this nebula. A consequence of this interpretation is that the mass of the envelope is of the order of 10–20 solar masses and the kinetic temperature is extremely high. The filamentary part of the nebula possesses more or less ordinary characteristics.
38. The cambridge survey of radio sources
Authors: Shakeshaft J. R.
Published: July 2016

A survey of radio sources at a wave-length of 3·7 metres has been carried out with a large interferometric radio telescope (Ryle and Hewish, 1955) [1] which has a receiving area of about 5000 square metres. Four parabolic troughs are arranged at the corners of a rectangle 600 metres east–west by 50 metres north–south. The reception polar diagram of each, ± 1° by ± 7° to half-power points, is thus filled with interference fringes in the north–south plane as well as the east–west plane. Sources are observed at transit, the time of which gives the right ascension, while the declination is obtained by comparing the observed intensity on successive days as the phase of the north–south pattern is altered.
39. The Spatial distribution of radio stars
Authors: Ryle M.
Published: July 2016

The Cambridge survey of radio stars [1], which has been described by Shakeshaft, revealed some 1900 sources of small angular diameter, which appeared to be distributed nearly isotropically. An examination of the number–magnitude distribution shows, however, that they cannot be accounted for in terms of a uniform spatial distribution of sources [2].
40. Preliminary statistics of discrete sources obtained with the ‘Mills Cross’
Authors: Pawsey J. L.
Published: July 2016

The statistics of the discrete sources observed in Cambridge and the interpretation given by Ryle and his colleagues constitute one of the most interesting items of recent astronomy. It is therefore of great importance to check the observational data and this can be done from the independent results being obtained in Sydney by Mills and his colleagues with the 85 Mc./s. Mills Cross. With this in mind Ryle sent me some two months ago a pre-publication account of the Cambridge work. (Now published, Ryle and Scheuer, 1955[1].) The currently available observations with the Mills Cross are not yet sufficient to give a decisive answer, but those available disagree with the Cambridge ones. Because of the importance of the subject it seems desirable to give here an interim account of these observations. The general position of the observations is discussed in a separate paper (paper 18, Pawsey). As stated there observations to date have been aimed at the study of known objects. The beam in each case was adjusted to the appropriate declination and an extended record, including the selected object in a small section, was taken. Most of these records have been examined for discrete sources and such sources listed with their intensities when sufficient records at adjacent declinations were available to delineate them. The list was restricted to sources which, within the 50′ limits of resolution of the equipment, appeared to be discrete point sources. Extended sources were neglected. This method gives an irregular coverage of the sky so that the sampling must be watched.
41. The spherical component of the galactic radio emission
Authors: Baldwin J. E.
Published: July 2016

As part of the programme of observations with the large Cambridge radio telescope, a survey of the integrated radio emission has been made using one of the four elements of the interferometer. At a wave-length of 3·7 metres this aerial has beam-widths to half-power points of 2° in right ascension and 15° in declination. The use of a long wave-length makes it possible to obtain accurate measurements of the brightness temperature of the sky in regions away from the galactic plane. It is with the radiation from these regions that this paper is primarily concerned.
57. A survey of Soviet observations of the radio emission from the sun during solar eclipses
Authors: Tchikhatchev B. M.
Published: July 2016

Soviet scientists working in the domain of radio astronomy carried out a number of observations of the radio emission from the sun during solar eclipses. The first observation was obtained by Prof. S. E. Khaikin and the author during the eclipse of 20 May 1947 at a wave-length of 1·5 metres. The solar eclipse of 25 February 1952 was observed in Archman, Turkmenian S.S.R., on wave-lengths of 3·2 and 10 cm. by V. S. Troitzky, and on 1, 1·5, 2 and 2·6 metres by the author and by V. V. Vitkevitch. The eclipse of 30 June 1954 was observed in Novomoskovsk, Ukrainian S.S.R., on 3·2 and 10 cm. by V. S. Troitzky, and on 10 and 23 cm. by V. V. Vitkevitch. It was also observed in the Caucasus on a wave-length of 3·2 cm. by A. P. Moltchanov. All the above observations were carried out in places located in the vicinity of the central path of the totality. The eclipse of 30 June 1954 was observed also outside the path of totality on the southern shore of the Crimea by a group of Dr Vitkevitch's colleagues on wave-lengths of 1, 1·5 and 3·5 metres. The maximum phase in this place was 92 %.