bluuebunny/crossref_metadata_2025 huggingface dataset:
Groups of Galaxies
Authors: Richard Gott J.
Published: March 2016

I would like to report on some work that Ed Turner and I have done on groups of galaxies and how groups may be used to obtain useful cosmological information. Of course the classic study of groups of galaxies was done by de Vaucouleurs (1975) who made a catalogue of groups and loose associations of galaxies in the local supercluster. Partly to obtain a larger sample of groups with uniform and well defined statistical properties and partly to obtain a sample of denser groups suitable for virial analysis, Ed Turner and I decided to make a new catalogue of groups of galaxies based on picking the groups as surface density enhancements in the Zwicky catalogue (Turner and Gott 1976) (TGI).
The Large Space Telescope Astrometric Instrument
Authors: van Altena W.F. , Franz O.G. , Fredrick L. W.
Published: March 2016

The preliminary designs for the LST and its instruments are now complete and present schedules call for the announcement of opportunity for the instruments to be issued during the summer of 1977 and launch of the telescope in late 1983. The astrometric instrument will be an integral part of the telescope’s fine guidance sensor system which is normally used to stabilize the telescope during exposures. Of the three fine guidance sensors, two are required to stabilize the telescope while the third is free to measure the relative positions of stars within a 40 square arc-min area. The instrument is designed to measure serially the relative positions of preselected stars with an accuracy of ±0″.002 (s.e.) to at least the 17th magnitude. The integration may be varied to achieve either higher accuracy or a fainter limiting magnitude.
[no title]
Authors: McCarthy Martin F.
Published: March 2016

After urging you all to briefness, I should set a good example. I “welcome you all: participating colleagues and all IAU members and guests, especially those from our host commissions 25, 33 and 45. I thank you all: the contributors to today’s events, to the members of the Organizing Committee, to the Presidents of the sponsoring Commissions, IAU officials and all those who are not here today but have helped to make the arrangements for today’s discussion.

To assist with the direction of our work I have asked Prof. K. Aa Strand, Prof. T. Elvius and Prof. B. Bok to preside over Parts One, Two and Three. Questions and comments may be made to the invited speakers and to the discussion contributors at the end of each Part of our program.
The Stellar Distribution above the Galactic Plane: An Introduction
Authors: King Ivan R.
Published: March 2016

This paper will truly be an introduction — a presentation and a discussion of the basic problems, to set the stage for detailed research results that will be reported by others.

The problem of star distribution perpendicular to the galactic plane has one central theme, which can be played in two modes. The theme is the drop-off of star-density with z, and the two modes are the general density profile and the stratification of populations. (This last phrase is a convenient one, but I should warn against taking it too literally. By “stratification” I mean a gradual change, rather than a sharp separation; and I want to emphasize even more strongly that the word “population” should be used in a general and abstract sense, rather than as a sharp separation into two, or five, or any other discrete number of components.)
Search for Large Radial Velocities in Direction of NGP Using the Fehrenbach Techniques
Authors: Florsch Alphonse
Published: March 2016

The Observatory of Strasbourg will participate in the future in the general radial velocity survey which is in hand at the Observatories of Haute-Provence and of Marseille with FEHRENBACH’s Objective-prism astrograph. A programme of this type, providing a large number of data, is particularly suitable at the place where the “Data Center” is growing up.

A radial velocity survey is a vast programme which needs many years to be fulfilled. It is natural that one starts with the most interesting areas in the sky, one of them being the area near NGP. In 1976 twenty fields were covered, each by one plate, in that direction. The whole programme covers 70 overlapping fields in an area of 100 square degrees centered at NGP. The limiting magnitude shall be almost the 12th.
Boundary Condition with Mass Loss: The Radiatively-Driven Wind Model
Authors: Mihalas Dimitri
Published: March 2016

A brief summary of the current status of radiatively driven wind models for early-type stars is given. A critique of these models is made both on theoretical and observational grounds, and it is concluded that a pure radiatively driven wind is probably not a realistic approximation for 0-star winds. It is argued that probably the wind structure must have an initial high-temperature (“coronal”) region through which the trans-sonic flow takes place, followed by radiative accelerations to very high terminal velocities. Full details of the discussion can be found in Stellar Atmospheres, 2nd Edition, by D. Mihalas, to be published by W. H. Freeman and Company, San Francisco, in Fall 1977.
Stratification of Elements in a Quiet Atmosphere: Diffusion Processes
Authors: Michaud Georges
Published: March 2016

In the absence of turbulence or convection one expects that, in stars, heavy elements would tend to settle gravitationally while light elements would go to the surface. Eddington (1930) however realized that this general tendency could be modified both by the electric field and by differential radiation pressure. In spite of their small mass, electrons do not all float on the surface of stars because an electric field is generated that keeps them from separating from the protons. Instead of settling gravitationally, heavy elements often concentrate on the surface because they absorb relatively much more photons than hydrogen or helium and are dragged to the surface by the radiative flux. Eddington concluded that turbulence was too strong for diffusion to be important in stars since the relation that diffusion predicts between surface abundances and stellar masses did not appear to be realized in most stars.
Spectral Classification of B and A Stars from the Line Features of S2/68 Spectra
Authors: Cucchiaro A. , Jaschek M. , Jaschek C.
Published: March 2016

The experiment S2/68 has supplied a large number of ear type spectra in the wavelength region 1350–2730 A. The resolution is 37 A, which is about equivalent to a reciprocal dispersion of 1850 A/mm. We had at our disposal about one thousand spectra of stars brighter than 6m5.

The availability of such material has lead us to establish a spectral classification system based only upon features visible in the spectrum. A second step was to compare this system to the MK classifications.

It turned out to be easy to establish a temperature sequence based upon convenient intensity ratios of line features and somewhat more difficult to establish luminosity criteria. Among the B type stars it is possible to distinguish main sequence objects, supergiants and intermediate objects.
Extreme Ultraviolet Observations of White Dwarfs
Authors: Lampton Michael , Margon Bruce , Bowyer Stuart
Published: March 2016

Observations shortward of the hydrogen Lyman limit provide sensitive determinations of stellar temperatures and interstellar absorption. Such data are of particular value in studies of hot white dwarfs, for which a large fraction of the emission occurs in the extreme ultraviolet band (100-1000 Å). Observations of HZ 43 and Feige 24 have been obtained with the Apollo-Soyuz extreme ultraviolet telescope; both stars are copious EUV emitters, with 4 × 10−9 and 3 × 10−9 erg/cm2 sec in the 170-620 A band respectively. The EUV data combined with optical spectrophotometry, allow their temperatures to be estimated as 80, 000 and 60, 000 K respectively. The corresponding interstellar neutral hydrogen column densities are ~ 4 × 1018 cm−2.
A Catalogue of 0.2 Å Resolution Far-Ultraviolet Stellar Spectra Measured with Copernicus
Authors: Snow Theodore P. , Jenkins Edward B.
Published: March 2016

Of the nearly 300 stars which have been observed in the ultraviolet with Copernicus, 60 have been chosen for publication of their complete intermediate-resolution spectra, which consist of scans made with photomultiplier U2 at a nominal resolution and step length of 0.2 Å. The spectra cover the wavelength range 1000 to 1450 Å and are expressed in the form of direct numerical tabulations, compressed-scale plots, and synthetic photographic spectrograms. These three modes of presentation are expected to satisfy the needs of various types of research on stellar spectra, ranging from detailed and rather specialized analyses of line profiles, which require accurate numerical results, to broad, comparative studies of various qualitative features over different spectral types, for which the plots or photographs are best suited. From the qualitative comparisons one might expect to synthesize more exacting criteria for spectral classifications of normal stars, using ultraviolet instead of visible spectra. The catalogue has been submitted for publication in the Astrophysical Journal Supplements.
Spectral Classification from Copernicus Data
Authors: Bidelman William P.
Published: March 2016

The suitability of Copernicus U2 spectrometer scans (resolution 0.2 Å, spectral range roughly 1000–1450 Å) for purposes of spectral classification is discussed. The main conclusion is that while many features in the spectra complicate the situation (numerous interstellar features and those related to the phenomenon of mass loss), the general behavior of the lines in the spectra of most of the 22 stars studied is entirely consistent with the presently accepted classifications of these objects. Whether a significant increase in the accuracy of determination of all of the relevant classification parameters can be obtained from this material is not yet certain. It is emphasized that study of the high-resolution Copernicus scans should be of great value for forthcoming classification programs necessarily utilizing spectral data of considerably lower resolution.
Star Spots on AR Lac Type Stars
Authors: Popper D. M.
Published: March 2016

There is no generally accepted definition of AR Lac Stars, and the term RS CVn stars is used interchangeably or to refer to a particular subgroup. For the purposes of this discussion I use the term AR Lac stars to refer to detached close binaries showing Ca II emission in at least the cooler component outside eclipse, the hotter component being a main-sequence or subgiant star of spectral type F or G. Most of the systems show irregularities in their light curves as well as period changes. In order to determine whether a system is detached, one must know both the mass ratio and the relative radii. The determination of minimum masses is a fairly straightforward spectroscopic task, and provisional values are available for 22 of the systems, two or possibly three of them being non-eclipsing. All but 3 (AD Cap, RT Lac, RV Lib) have masses of the two components within 30% of each other. Because of appreciable irregularities in the light curves, the radii are subject to considerable uncertainty even when photometry of good precision is available. Nevertheless the 9 systems with very provisional radii all appear to be detached. These all have mass ratios near unity. We may assume, as a working hypothesis, that the other systems with mass ratios near unity are also detached and hence also belong in the AR Lac group. Most of the data referred to are to be found in IBVS 1083.
The Uniqueness of the Geographic South Pole for the Observations of Large Scale Velocity Fields on the Sun: Some Experiences from a 120 Hours Continuous H-Alpha Patrol during January 1979
Authors: Kusoffsky U. , Pomerantz M. A.
Published: March 2016

Continuous solar observations over extended periods of time with the sun at constant altitude have heretofore been unobtainable. A solar observatory at the geographic South Pole will provide continuous homogenous observations of various solar features during the austral summer months. An optical site testing campaign during January 1979 showed seeing conditions at the site to be even better than expected. During the 1979-80 austral summer solar global oscillations will be studied with the Nice sodium cell spectrophotometer. Lifetime studies of the chromospheric network will be conducted with a 30-cm heliostat in combination with a 20-cm f/100 objective lens to provide a 20-cm solar image for monochromatic filters during the following year.

A report published a decade ago by the U. S. National Academy of Sciences (1970) devoted one chapter to a discussion of the potential advantages of conducting certain types of astronomical observations at the geographic South Pole. One unique feature of this site is that it affords the opportunity for obtaining continuous homogenous observations with a single instrumental system over extended periods of time. Furthermore, special benefits for solar research stem from the constant angular level of the sun in the sky and the uniform local geography of the high altitude polar plateau (2912 meters, mean atmospheric pressure 680 mb corresponding to roughly 3300 meters at midlatitude).
Global Circulation of the Sun: Where are we and where are we going?
Authors: Gilman P. A.
Published: March 2016

There are several goals I hope to reach in this talk. First, I would like to give this broad audience some idea of our present state of knowledge concerning global circulation of the sun—what the observations tell us (and don’t tell us!) as well as current theories. This will comprise a large part of my talk. In doing this, I hope I do not bore the specialists in this area. Second, I would like to put the problem of global circulation of the sun in the broader context of “solar variability”, a topic of rapidly growing interest in the solar community, that has implications for stars generally, and which may not have caught the attention of the stellar community. I would like also to put the solar circulation problem in the context of stellar rotation, by making a few admittedly speculative extrapolations to other stars. In addition, I will give a few of my own opinions about what we should be doing in the near future to make more progress in understanding the solar problem. And finally, I hope to provoke a wide ranging discussion of the whole area of circulation and variability in the sun and stars.
Infrared Emission from Spiral Galaxy Nuclei
Authors: Wynn-Williams C. G.
Published: March 2016

At the present time we do not know with any certainty what the infrared properties of “normal” galaxies are, although we do know that substantial broad-band emission at 10μm is fairly common in spiral galaxies; Rieke and Lebofsky (1978), for example, were able to detect the nuclei of 16 out of 39 bright spiral galaxies above a level of about 50 mJy. Only one of these, NGC 1068, is a Seyfert Galaxy.

With the exception of M31, whose 10μm emission can be accounted for entirely by stellar photospheric emission, all the spiral galaxies detected in Rieke and Lebofsky’s survey show strong emission from heated dust grains. Airborne observations at longer wavelengths (e.g., Telesco and Harper 1980) of a few of these galaxies show a peak in the energy distribution at around 80μm, corresponding to dust temperatures of order 30-60K, while spatial scans, and multi-aperture photometry at 10μm (Rieke 1976; Becklin, Fomalont, and Neugebauer 1973; Becklin et al. 1980) indicate a physical size for the emitting region of a few hundred parsecs diameter.
Ultraviolet Emission from Strong X-Ray Sources as Observed with Iue
Authors: Gursky Herbert , Davis Robert
Published: March 2016

In 1972, when the request for observing programs for the International Ultraviolet Explorer (IUE) was first made by NASA, ESA and the United Kingdom, a number of scientists recognized that observations in the ultraviolet of the strong galactic X-ray sources could be a fruitful activity. The underlying nature of those objects was understood. Their binary nature had been discovered through the X-ray observations which, combined with extensive optical observations and the insight gained through the tie to traditional ideas of stellar evolution, led to a picture whose general features are still accepted. The strong X-ray sources were taken to be close binary systems in which one object was a compact star, either a neutron star or a black hole, and the other object a common star in a stage of its life when it was undergoing great mass loss, either as a stellar wind or through Roche-lobe overflow.
Abundances in Diffuse Interstellar Clouds
Authors: Jura M.
Published: March 2016

Interstellar clouds are concentrations of cold (T ≲ 100 K) neutral gas (cf. Spitzer 1978) which are immersed within an intercloud medium. It is worthwhile to distinguish between diffuse clouds (roughly those with E[B-V] ≳ 0.5) and dark clouds (those with E[B-V] ≳ 0.5). This distinction is useful in the sense that diffuse clouds are relatively warm (T ∼ 100 K), they are composed mostly of atomic species except for hydrogen which can be appreciably molecular, and they are dynamically controlled by their interaction with the intercloud medium. Dark clouds are relatively cold (T ∼ 10 K), they contain a rich variety of molecules, and self-gravity is important in their evolution. Because the interstellar extinction is a rapid function of wavelength, most ultraviolet observations have been of diffuse clouds. The IUE satellite is sufficiently powerful that observations of some dark clouds are possible, and an important area of future research will be to delineate more quantitatively the similarities and differences between diffuse clouds and dark clouds.

With ultraviolet observations, considerable progress has been made in understanding the physical characteristics of clouds including determinations of their densities, temperatures, chemical compositions and dynamics (cf. Spitzer and Jenkins 1976). Because particular progress has been made on understanding the abundances within diffuse clouds and because of the limitations of space, we restrict this review to a discussion of abundances within diffuse clouds. These abundance measurements provide a set of fundamental astrophysical data.
Variability in β Cephei and B Stars
Authors: Smith Myron A.
Published: March 2016

Rather than review β Cepheids, this paper will address the issue that β Cephei variability is only a readily detectable tip of a much larger iceberg of variability among β stars. This variability being widespread, it becomes crucial to differentiate β Cepheids from other variable subgroups by observational criteria if one is ever to make physical inferences concerning the instability mechanism involved. Shobbrook (1978) has raised this point indirectly in discussing the importance of defining the width of the instability strip: if the strip is narrow, the pulsational instability is more likely to arise in the stellar core; if it is wide, it is probably excited in the envelope. Enormous efforts have gone into delineating the evolutionary and HR-D confines of ß Cepheids. In this paper it will be suggested that the situation is more complicated than the traditional outlook holds.
Theoretical Nonradial Pulsation of β Cephei Models
Authors: Sato Hideyuki
Published: March 2016

The excitation mechanism for the pulsations of β Cephei stars and variable B stars is not yet understood. Recently, Stellingwerf (1978) found that an opacity bump located near the He+ ionization zone has a significant effect on the stability of radial pulsations in massive stars. However, the opacity bump, according to current opacities, is probably not enough to excite radial pulsations. On the other hand, some observational facts suggest that nonradial pulsations may participate in the variations of β Cephei stars and variable B stars. Therefore, it is interesting and important to examine the effect of the opacity bump on nonradial pulsations in massive stars.
Recent Theoretical Results for δ Scuti and Dwarf Cepheid Variables
Authors: Percy John R.
Published: March 2016

Recent evidence suggests that δ Set stars and most dwarf Cepheids are population I objects of normal mass. The remaining dwarf Cepheids, including CY Aqr, DY Peg, SX Phe and GD 428, have low masses, are metal-deficient, and are in a presently undetermined stage of evolution (Breger 1979, McNamara and Feltz 1978, but see also Simon 1979).

Many δ Set and dwarf Cepheid variables are multiperiodic and, in principle, multiple periods can be used to infer physical properties of these stars. The component periods must be determined accurately and reliably, and several workers (Breger, Fitch, Kurtz, Pelt, Percy, Shob-brook, Stellingwerf, Stobie and Warman) are active in developing and applying new methods of period analysis; see Wizinowich and Percy (1979) for a representative example.

One result of these analyses is the discovery that in some stars, modes may vary in amplitude or appear or disappear completely within a few days (Stobie and Shobbrook 1976). Methods of period analysis must allow for this possibility if they are to be accurate and reliable.
Observations of Classical Cepheids
Authors: Madore Barry F.
Published: March 2016

Calibration of the Period-Luminosity relation for Classical Cepheids is still far from settled: the debate continues as to whether there is a unique relation from galaxy to galaxy and what the precise form is in any one system. In the Milky Way we suffer from poor sample size; in the Magellanic Clouds it is still a matter of low accuracy in the observations. Work is in progress at several observatories to alleviate both of these problems through studying not only galactic Cepheids but also those in the LMC, SMC, M33 and NGC 300.

Arellano & Percy (CTI0/DD0) have begun a photoelectric monitoring of the apparently brightest F & G supergiants in the Milky Way. The aim is to detect near-by very-low-amplitude Cepheids which are binaries or are intrinsically low amplitude variables. This should provide a better qualitative hold on the sense of the amplitude dependence on effective temperature, as well as the true fequency of the cepheid phenomenon.
Distances and Radii of Classical Cepheids
Authors: Barnes Thomas G.
Published: March 2016

Suppose one of the current high angular resolution instruments were capable of measuring the instantaneous angular diameter of a Cepheid throughout its pulsation cycle. By comparing the angular diameter variation to the linear displacement variation, obtained from the integrated radial velocity curve, one could determine both the linear radius and the distance of the variable. This distance would be independent of all other astrophysical distance scales and would be geometric, i.e. independent of the effects of interstellar obscuration.

Although none of the current instruments has this capability, the same result can be accomplished indirectly through use of the stellar surface brightness. Recall that the visual surface brightness can be expressed in terms of the apparent visual magnitude and the stellar angular diameter. At any phase in the Cepheid pulsation, knowledge of the visual surface brightness and the apparent magnitude permits inference of the angular diameter.

From stars with measured angular diameters it is known that the visual surface brightness parameter Fv correlates remarkably well with the Johnson V-R color index (Barnes and Evans 1976; Barnes, Evans and Parsons 1976; Barnes, Evans and Moffett 1978). Johnson VR photometry may thus be used to determine the visual surface brightness and hence the stellar angular diameter. As shown in the referenced works, such angular diameters are essentially independent of the choice of interstellar obscuration corrections. This approach to stellar angular diameters and then to variable star distances is therefore nearly equivalent to direct measurements.
The Pulsation Properties of Red Variables
Authors: Feast M. W.
Published: March 2016

Recently derived bolometric absolute magnitudes are used to investigate the pulsational properties of some classes of red variables. The Mira variables with periods over 200 days have pulsation constants appropriate to overtone pulsatore but the shorter period 135 day Miras seem to be hotter and less luminous and may be fundamental pulsators. The large amplitude Shapley-Nail variables in the SMC are probably fundamental pulsators with masses in the 5-10 solar range. Bright supergiant red variables in the LMC show evidence of the period-luminosity relation expected if they are in the early stages of core helium burning.
High Resolution X-Ray Spectroscopy of The Gas Surrounding M87 and NGC1275: Emission Line Detection and Evidence for Radiatively Regulated Accretion
Authors: Canizares C. R. , Berg C. , Clark G. , Jernigan J. G. , Kriss G. , Markert T. H. , Schattenburg M. , Winkler P. F.
Published: March 2016

The topic of this paper really falls somewhere between this session on active galaxies and the session on clusters. What I will report is really a cluster phenomenon but one which depends on the presence of a dominant, massive galaxy in the cluster. Specifically, we have detected several X-ray emission lines from the vicinity of M87 in the Virgo Cluster and NGC 1275 in Perseus. The lines are indicative of material which is cooler than the bulk of the intracluster gas. This material is most likely accreting onto the central galaxy with the accretion rate controlled by the rate of radiative cooling.

The observations I am reporting were made with the Focal Plane Crystal Spectrometer (FPCS)on the Einstein Observatory. The instrument is a Bragg crystal spectrometer which has a resolving power (E/ΔE) of 50 to 500 over the energy range of 0.2 to 3 keV. It operates much like an optical scanner in that it has a narrow passband which is swept over some restricted spectral range containing an emission line. Detailed descriptions are given elsewhere (Canizares et al. 1977, 1979, Giacconi et al. 1979).
X-Ray Observations of M87’s Halo
Authors: Fabricant D. , Lecar M. , Gorenstein P.
Published: March 2016

We briefly describe the soft X-ray image of M87 obtained using the imaging proportional counter aboard the Einstein Observatory. These data provide further strong evidence for the existence of a massive halo of dark matter surrounding M87 and allow a much more precise determination of its mass. Two pointing positions of the satellite were analyzed; one centered on M87, the other 63’ south and 25’ east of M87. The field of view of the imaging proportional counter is 60’ × 60’, and it attains a two dimensional spatial resolution of ˜ 1.5’ in a spectral range spanning 0.1 to 4.5 keV.

As previous reports had suggested (Gorenstein et al. 1977; Fabricant et al. 1978), the present observations show M87 to be a strong, very extended, thermal X-ray source with a temperature near 2 keV, surrounded by weaker and still more extended emission from hotter gas associated with the Virgo cluster as a whole (Davison, 1978; Lawrence, 1978). We find M87 to have a total 0.5-4.5 keV X-ray luminosity of about 2 × 1043 ergs/sec, and an extrapolated 2-6 keV luminosity of approximately 1 × 1043 ergs/sec. The total mass of gas inferred from the X-ray measurement exceeds 1012 solar masses.
Clusters of Galaxies
Authors: Bahcall Neta A.
Published: March 2016

Clusters and groups of galaxies contain the majority of galaxies in the universe. The rich clusters, while less numerous than the many poor groups, are the densest and largest systems known, and can be easily recognized and studied even at relatively large distances. Their study is important for understanding the formation and evolution of clusters and galaxies, and for a determination of the large-scale structure in the universe.
X-Ray Studies of Clusters of Galaxies with The Einstein Observatory
Authors: Helfand D. J. , Ku W. H.-M. , Abramopoulos F.
Published: March 2016

With the advent of imaging in X-ray astronomy, we can, for the first time, study extended sources with the same detailed spatial and spectral resolution employed by radio and optical astronomers. As in other fields of astronomy, the study of the X-ray emission from clusters of galaxies is beginning to feel the tremendous impact of this advance. The accompanying contributions by Murray and by Grindlay show that the division of clusters into classes based solely on X-ray morphology holds clear implications for the origin of the intracluster medium and the evolution of the cluster as a whole. Comparisons with optical and radio data, along with detailed X-ray studies of nearby objects and the extension of cluster observations to redshifts greater than 0.5, will help connect these ideas to a sound theoretical base. In this report on the cluster observations performed by the Columbia Astrophysics Laboratory with the Einstein Observatory, we restrict ourselves to three brief comments concerning the following areas: (1) The correlation of X-ray brightness with cluster morphology, (2) the detection of a spiral-rich cluster at z ˜ 0.4, and (3) detailed observations of Coma, the nearest rich cluster.
Space Astrometry - Its Impact on Astronomy and Astrophysics-Introductory Comments
Authors: Westerhout Gart
Published: March 2016

Astrometry - the determination of positions, motions, and coordinate systems and the entirety of the products of these observations- was the first specialty in astronomy. The value of astrometry for all of the fields of astronomy does not have to be emphasized here; it is clear that the foundation of astronomy and astrophysics is provided by astrometry. What is perhaps not so clear is the fact that, although considerable progress has been made in the seventies, the numerical estimates for many of the basic quantities are much less certain than the average user realizes. Fortunately, astrometry stands at the brink of a technological revolution, involving both ground-based and space techniques. Once completed, this will lead to one or more orders of magnitude improvement in both the precision and quantity of most astrometric observations, with enormous implications for other fields of astronomy.
The Needs in the Radial Velocity Area in View of Impending Space Astrometry Projects
Authors: Andersen J.
Published: March 2016

I have understood the title of this talk given to me by Dr. Westerhout to imply a review of our present ability to provide new radial velocity measurements for the many stars to be observed by the Space Astrometry projects, as well as an indication of the technical developments still required. And indeed, the quantity and quality of the existing radial velocity determinations are such that only a small fraction of the data needed can be considered available.

The challenges presented by the two projects, the Astrometry Satellite and the Space Telescope, are somewhat different, corresponding to the complementary nature of the two programmes: The dedicated Astrometry Satellite will observe a very large number of relatively bright stars, while the Space Telescope is expected to give astrometric results for much fainter, but also far fewer objects (estimated currently at perhaps 20 per year). The two programmes will therefore be considered separately.
Rotational Studies of Lower Main Sequence Stars
Authors: Smith Myron A.
Published: March 2016

This review summarizes the techniques and limitations involved in determining small rotational velocities in late-type stars. Recent results from photoelectric line profiles of field main sequence G stars will also be presented.

Historically three techniques have been used to measure stellar rotational velocities: (1.) calibration of a “clean” line width in terms of computed profile models, (2.) use of the Fourier transform frequency domain (dissection of rotation and turbulent velocity fields from the thermal profile), and (3.) monitoring of the rotational modulation of a chromospherically active or spotted star. The results discussed below concern technique (2.). Technique (3.) has not been exploited much yet but holds considerable promise for the future, in particular for the measurement of ultra-slow rotation.
The Rotation of Pre-Main Sequence Stars
Authors: Kuhi Leonard V. , Vogel Stuart
Published: March 2016

Kraft (1970) obtained the rotational velocities for large numbers of stars located in the field and in clusters of different ages. He noted that (a) among the field stars those stars with strong Call K emission had larger rotational velocities than those without; (b) stars in the Hyades and Pleiades (which are much younger than the field) had both larger rotational velocities and stronger Call K emission than field stars; (c) there was a pronounced break at spectral type early F in v sini as a function of spectral type and (d) the distribution of angular momentum per unit, mass J(M⊚) was proportional to M0.57for main sequence stars with mass M > 1.5 Mʘ. This distribution predicted a v sini of ˜75 km/sec for stars of lower mass (e.g. G type) but such high velocities were not seen in the Pleiades nor in the sun. This implied a more rapid deceleration of v sini for lower mass stars and led to estimates of the e-folding time of ˜4×l08years for stars of 1.2 M⊚to reduce their v sini from that of the Pleiades to that of the Hyades and ˜4×l09years to go from the Hyades to the sun’s v sini. We note also that the age of the Pleiades is approximately equal to the pre-main sequence lifetime of a 1.0 M0star so that the zero-age main sequence cannot have J(M) α M0.57for ˜1 M0stars. Skumanich (1972) showed that both the Call k emission and the rotational velocity decayed as the (age)-½for main-sequence stars.
A Baker’s Dozen: Unsolved Problems with The RS Canum Venaticorum and by Draconis Stars
Authors: Hall Douglas S.
Published: March 2016

The theme of this Joint Meeting of Commissions 10, 27, 40, 42, 44, and 48 is “Close Binaries and Stellar Activity”. At the time this meeting was initially conceived, we took stellar activity to mean activity such as we observe on the Sun: spots, flares, chromospheric emission, variable radio and X-ray emission, coronas, winds, and so forth. That is why the series of seven reviews presented at this meeting will deal for the most part with convective stars, in particular with the RS CVn-type and BY Dra-type stars, which we know are active in so many of these ways.

It had been planned that Steven N. Shore would review briefly the situation from a theoretical viewpoint (briefly, I say, because theoretical treatment of the problem is still in the infant stages). Reference can be made, however to the contribution he presented at I.A.U. Symposium No. 88 in Toronto.

One way to open this meeting, I hope a useful way, is simply to list some unsolved problems. Those on my list may not be equal in importance or difficulty. Different problems would no doubt appear on someone else’s list. It may even turn out that, after we have heard these reviews, a number of my unsolved problems have already been solved or soon will be, but that would be a pleasant surprise rather than a disappointment.
The Problem of Abundances for “Metal-Rich” Globular Clusters
Authors: Gustafsson Bengt
Published: March 2016

The discrepancy between the results of recent high-dispersion analyses and of studies at lower resolution for the classical metal-rich globular clusters is discussed and different explanations for this discrepancy are considered. It is concluded that further systematic investigations are motivated in order to establish the more or less interesting astrophysical explanations for it.
Stellar Populations in the Nuclei of Spiral Galaxies
Authors: O’Connell R. W.
Published: March 2016

Spiral galaxies are a composite of two dynamical population types: the spheroidal and disk populations. These can be studied in isolation in E and Irr galaxies, respectively. It is natural to expect that the combination in a spiral of a dense spheroidal population, having a deep central potential well, with a repository of interstellar gas and dust in the disk gives rise to special conditions not usually found in E or Irr galaxies. And in fact, we find spectacular concentrations of star forming regions in some spiral nuclei.

In this review, I will limit most of the discussion to later spiral types which are classified as “intermediate” in the Yerkes system (Morgan and Osterbrock 1969). Types earlier than Sbc usually have “k-nuclei,” where the spheroidal population dominates; excellent reviews are available for these types (van den Bergh 1975, Faber 1977).
Stellar Populations and Hubble Type
Authors: van den Bergh Sidney
Published: March 2016

Men are more apt to be mistaken in their generalization than in their particular observations. Machiavelli

It was already realized by Hubble (1936) that galaxy morphology and stellar content were correlated. He pointed out that resolution into stars increases along the classification sequence Sa-Sb-Sc. Simultaneously the colours of spirals become bluer and their integrated spectral types become earlier as one proceeds from Sa to Sc. Baade (1944) speculated that the red stars in ellipticals and in the nuclear bulges of spirals were identical to those in globular clusters. He suggested that stars in galaxies belong to two distinct populations: young metal-rich stars of Population I which inhabit the disc and spiral arm regions of spirals, and old metal-poor stars of Population II which dominate the light of elliptical galaxies and the nuclear bulges of spirals. Subsequently Baade (1950) emphasized the strong correlation between the occurrence of gas and dust and the presence of young stars. As Baade put it so succinctly “No dust, no Population I”. Belief in a clear cut dichotomy between Population I and Population II was strengthened by the differences in their radial luminosity distributions. The surface brightness of Population I in spirals is well represented by an exponential disc, whereas the surface brightness of Population II stars in ellipticals and the bulges of spirals may be described by an r1/4 law (de Vaucouleurs 1959).
Introductory Remarks
Authors: Hodge P. W.
Published: March 2016

It is not easy to measure distances to galaxies. That we even try is as much a measure of our audacity as it is an indication of our ingenuity. But we do try, and we feel that we must try, because so many of our grandest questions and most basic problems about the universe depend on our knowledge of its size and scale.

This Joint Discussion brings together some of the astronomers who have concerned themselves with this difficult task. They do not all agree among themselves. This is not a topic that has reached a state of selfcomplacent fixity, but rather is still a subject of controversy and doubt. The Joint Discussion was designed by its organizers to expose the problems rather than to solve them, to discover the questions rather than to agree on an answer to them.
Hubble Type Dependence in the Tolly-Fisher Relationship
Authors: Thonnard Norbert , Rubin Vera C.
Published: March 2016

Data from 60 field spiral galaxies shows that the Tully-Fisher (TF) relationships, MB vs. log(Vmax) and log(Dkpc) vs. log(Vmax), are both Hubble type dependent and that the slope in the MB–log(Vmax) correlation is steep, ~10.

Our study, conducted in collaboration with W.K. Ford, Jr. and D. Burstein, is principally aimed at elucidating the intrinsic range of properties of spiral galaxies. Hence, we picked a sample of 21 Sc’s, 23 Sb’s and 16 Sa’s with the widest range in luminosity and radius we could find at each Hubble type. Type classifications come principally from Sandage and Tammann (RSA); a few from de Vaucouleurs et al. (RC2) and Nilson (UGC). We stress that this is not a volume limited sample; the end members in the luminosity or radius range of the galaxies at each Hubble type are quite rare. Vmax comes from the maximum observed optical rotation velocity. We also have 21-cm profiles for all Sc’s, 2/3 of the Sb’s and 1/2 of the Sa’s; the result remains the same whether Vmax comes from 21-cm profiles or optical rotation curves. But note, ~1/3 of the Sa galaxies observed were undetectable at 21-cm. This must introduce a bias in the infrared 21-cm TF results. Magnitude corrections come from Heiles and Burstein (1978), but corrections from the RC2 give the same result. We currently have data for 8 galaxies in the Pegasus I and Cancer clusters, which are also consistent with the results shown below.
Cometary Spectroscopy and Implications to the Chemical Composition, Physical Properties and Origin of Comets
Authors: Rahe Jürgen
Published: March 2016

Recent spectroscopic observations of comets, obtained especially in the vacuum ultraviolet spectral region from sounding rockets and satellites, have considerably increased our knowledge of the chemical composition of comets, and the physical and chemical processes occurring in their head and tail. From the UV spectra of comets observed so far, one can perhaps conclude that they have a very similar, homogeneous chemical composition, and possibly also a common origin.
Properties of Ices and Grains: An experimental study
Authors: Dorm Bertram
Published: March 2016

Proton irradiation of a variety of ice mixtures were carried out to study the effect of galactic cosmic ray irradiation of comets in the Oort Cloud. Three significant effects were noted (1) production of new molecules; (2) production of a more energetic ice at low temperatures; (3) production of a non-volatile, complex organic residue. These phenomena suggest various effects on new comets approaching the sun including enhanced activity. Experiments on the condensation of silicate grains provide information on the condensation mechanism and properties of grains. Controlled annealing of the amorphous condensates shows how crystallization occurs. Infrared spectra of different stages of crystallization contain features that may identify composition, structure and history of refractory material.
Interrelations Among Asteroids, Comets and Meteoroids
Authors: Simonenko A.N. , Levin B.J.
Published: March 2016

If we investigate the interrelations among different classes of small solar system bodies, we must be aware that we deal with nonrepresentative and practically noncomparable data samples consisting of bodies differing either in size, or in orbits, or in their nature. So, practically, all our knowledge about small bodies - from kilometer-sized Apollo asteroids (including Atens) and Amor asteroids (designated below as AA bodies) to fine dust particles - refer to bodies on orbits intersecting the ecliptic plane at a heliocentric distance ≃ 1 A.U. To solve the problem of origin of this ensemble it would be advantageous if analogous data could be obtained at least for one more heliocentric distance. Since planetary atmospheres are excellent detectors for small cosmic objects, the necessary data could be obtained with the aid of artificial satellites orbiting a planet, e.g. Mars or Venus. Thus the source for the ensemble of Earth-crossing objects may not be correctly pictured. Are comets or asteroids the general supplier? We know the answer to this question only in two cases: (1) meteor streams such as the Leonids originate from comets, (2) meteorites originate from asteroids. But these two categories represent a minute part of the considered ensemble by mass. As to its other members- the selection of the source is a matter of tradition rather than a logic conclusion.
Nature, Origin and Evolution of Interplanetary Dust Grains
Authors: Lamy Philippe L.
Published: March 2016

This contribution will attempt to give a coherent and up-to-date view of the interplanetary dust cloud as well as to delineate some of the current outstanding problems. It is largely based on studies carried out at Laboratoire d’Astronomie Spatiale during the past years.
Physical Conditions in the Central Region, and the Nature of the Engine
Authors: Cavaliere A.
Published: March 2016

The phenomena associated with Active Galactic Nuclei raise three main astrophysical problems: (1) the nature of the primary source of energy; (2) the physical conditions within the radiation source; (3) the nature of the population evolution over cosmological time-scales.

I shall outline the links between (1) and (2), (1) and (3), that briefly go as follows. The Prime Mover is very likely to be a converter of gravitational energy in a very compact mass configuration. The associated radiation source, if it is also very compact, is so efficient and loss-dominated as to require specific conditions for the power transport and supply to the radiating particles: collisionless, effected by electromagnetic fields coherent on scales collective or macroscopic, to the point of producing at times anisotropic bulk motions. Very compact Prime Movers working at high regimes need also a compact mass supply; the output from these compound engines undergoes a characteristic change that accounts for the type of population evolutions of the associated sources.
Positron-Electron Annihilation Radiation from the Galactic Center
Authors: Ramaty R. , Lingenfelter R. E.
Published: March 2016

We discuss observations of the intense, time variable and very narrow 0.511 MeV positron-electron annihilation line from the Galactic Center, and the implications of these and other observations on the source of the positrons and their annihilation site.
Mass Loss from Novae and Supernovae
Authors: Friedjung Michael
Published: March 2016

The physics of mass loss from these objects is reviewed. Both winds of different types and nearly instantaneous ejection are involved. Supercritical winds driven by the pressure of radiation from an object above the Eddington limit, probably exist for novae after their outbursts. Observations outside the optical region and in particular in the satellite UV have been very important.
Infrared Properties of Extragalactic HII Complexes
Authors: Telesco C. M.
Published: March 2016

Many galaxies emit significantly more infrared radiation than expected as directly observable photospheric emission. This emission is not restricted solely, or even predominantly, to the galactic nuclei. Rather, where detailed observations exist, they indicate that pronounced emission often originates throughout the disks and especially in the more extended central regions which are distinct from the nuclei. The process which invariably dominates the emission at wavelengths longer than a few microns is radiation from heated dust. At shorter infrared wavelengths, nebular continuum and line radiation, as well as the stellar photospheres, has been observed. In many cases, this emission has been unambiguously associated with HII complexes.

In this review, we focus first on infrared observations of relatively isolated giant HII complexes in the LMC and the spiral arms of M33 and Ml01. We then examine complexes which extend over several kiloparsecs near the galaxian centers. We will not consider the large body of data on extragalactic infrared emission which, although surely relevant to our discussion, is not straightforwardly attributable to HII complexes rather than unusual phenomena in the nuclei (see Rieke and Lebofsky 1979).