bluuebunny/crossref_metadata_2025 huggingface dataset:
Comments on the Significance of the Positions of Population I Wolf-Rayet Stars in the HR Diagram
Authors: Underhill Anne B.
Published: July 2016

The size of typical errors in log L/L⊙ and log Teff is investigated for WR stars, and it is found that typically Δ log L/L⊙ = ±(0.25 ± 0.03), and Δ log Teff = ±(0.05 ± 0.02). The major sources of error are the uncertainties in the distance modulus of the star and the integrated continuous flux from about 1400 å to 1 µm or so. The same is true for O and early B stars. With uncertainties of these sizes in log L/L⊙ and log Teff, it is unreliable to estimate the mass of an early-type star from its observed position in the HR diagram. The WN7/8 stars lie with the O9/B0 Ia stars, the other WR stars with the B0/B1 III stars.
The Lick Observatory Hamilton Echelle Spectrometer
Authors: Vogt Steven S.
Published: July 2016

The Hamilton Echelle Spectrometer, recently installed at the coudé focus of the Shane 3-m telescope, is a high dispersion spectrograph optimized for use with large format CCD's. It was designed primarily for high resolution (R=50,000) wide bandpass spectroscopy of point-like sources down to a limiting magnitude of about V=16.5, over the 0.34 μm to 1.1 μm spectral region. Its design features a relatively large collimated beam size, the use of prisms rather than gratings for cross dispersion, minimum order separation, the use of protected silver mirror coatings throughout the system, and a fast (f/1.67) folded Schmidt camera with a flat external focal plane. Together, these features yield a very powerful spectrometer for high resolution stellar spectroscopy. This paper gives a brief description of the Hamilton spectrometer and gives several examples of its performance on astronomical objects.
Signal-to-Noise Ratio and Astronomical Fourier Transform Spectroscopy
Authors: Maillard J. P.
Published: July 2016

The multiplex properties of the Fourier Transform Spectrometer (FTS) can be considered as disadvantageous with modern detectors and large telescopes, the dominant noise source being no longer in most applications the detector noise. Nevertheless, a FTS offers a gain in information and other instrumental features remain: flexibility in choosing resolving power up to very high values, large throughput, essential in high–resolution spectroscopy with large telescopes, metrologic accuracy, automatic substraction of parasitic background. The signal–to–noise ratio in spectra can also be improved: by limiting the bandwidth with cold filters or even cold dispersers, by matching the instrument to low background foreoptics and high–image quality telescopes. The association with array detectors provides the solution for the FTS to regain its full multiplex advantage.
White Dwarfs as Observed at High Signal to Noise
Authors: Greenstein Jesse L.
Published: July 2016

The goal is largely historical, 30 years of instrumental progress in a difficult new field, faint white dwarfs, and some results. High signal-to-noise spectrophotometry at 40–160 Å resolution revealed the separation between hydrogen- and helium-rich atmospheres, and provided a temperature scale from models. The white-dwarf color-luminosity relation proved narrow. Their simple spectra made brute-force averaging possible to 14th magnitude at good photographic resolution. Features as shallow as 5% and 200 Å wide included C2, but in magnetic stars some strong absorptions remain unidentified. Metals are deficient, gravitational diffusion setting the surface composition. The Palomar double CCD spectrograph can now give S/N ≈ 100 to 17m. Some polarized white dwarfs have Zeeman triplets in magnetic fields near 20 megagauss. In one, Zeeman components are shifted up to 2000 Å at 300 megagauss. Rotation is small in all white dwarfs, angular momentum mostly lost. Non-LTE cores of Hα, Hβ exist and permit improved gravitational redshifts. An evolutionary phenomenon is progressive steepening of the Balmer decrement below 7000 K, cool atmospheres being helium-dominated.
Abundance and Magnetic Field Geometries of Helium-Strong and Helium-Weak Stars
Authors: Bohlender David A. , Landstreet J. D.
Published: July 2016

The helium-weak and helium-strong stars are main sequence stars with anomalously weak and strong helium lines for their spectral types respectively. Many members of the two classes have strong, globally ordered magnetic fields (Thompson and Landstreet 1985; Bohlender et al. 1987) and are currently thought to represent high temperature extensions of the Ap stars. In collaboration with C. T. Bolton (U. of Toronto), we have obtained high S/N phase resolved spectra of several stars using the coudé reticon detector at CFHT. One of the principle goals of this work is to determine abundance and surface magnetic field geometries of several helium peculiar stars with large, well-determined effective fields. We employ a line synthesis program (Landstreet 1987) that incorporates the effects of surface magnetic fields and non-uniform abundances on the observed line profiles of a star. Since these stars are rapid rotators the surface magnetic field strength must be inferred from differential magnetic intensification of lines with different magnetic sensitivities. Of the few lines with suitable strengths in these hot stars we have decided that the Si III multiplet 2 lines are best suited for this aspect of our investigation. We have also modelled the unblended He I line λ4437, ignoring magnetic effects for the time being. Individual results are discussed below.
Magnetic Field and Silicon diffusion in Bp-Si Stars
Authors: Mégessier C. , Lanz T. , Landstreet J. D.
Published: July 2016

SiII lines of magnetic Bp-Si stars in open clusters have been observed with the CAT (ESO) in order to get a mapping of the Silicon abundance distribution over the stellar surface, in the frame of the oblique rotator model. We point out the influence of the Zeeman splitting and of the abundance inhomogeneities on the line profiles.
NLTE Analysis and Chemical Composition of Hot Low-Mass Stars
Authors: Heber U. , Hunger K. , Werner K.
Published: July 2016

Spectroscopic analyses of hot pre-white dwarfs, i.e. subluminous O and B stars, are presented. In the B-type stars, the resulting abundance patterns are indicative of atmospheric diffusion (gravitational settling). Amongst the O-type subdwarfs, a new group of comparatively luminous stars is identified. Their position in the HR-diagram suggests that, unlike the “classical” sdOs, they are in a post-AGB stage of evolution. Spectroscopic evidence is presented showing that the born-again post-AGB star scenario of Iben et al. (1983) can explain their origin.
Lithium Abundances, Diffusion and Macroscopic Motions In Stellar Clusters
Authors: Vauclair Sylvie
Published: July 2016

The “lithium gap” observed in the Hyades and other galactic clusters by Ann Boesgaard and her collaborators (Boesgaard and Tripicco 1986, Boesgaard 1987, Boesgaard, Budge and Burck 1987) gives a challenge to theoreticians. Indeed a good fit between the theoretical results and the observations will give a clue for our understanding of the stellar internal structure and evolution.
Chemical Compositions of Population II Mid- and Late-Type Stars
Authors: Bond Howard E. , Luck R. Earle
Published: July 2016

The abundance patterns in Population II red giants provide information about galactic chemical evolution and nucleosynthesis sites for various chemical elements. These patterns were first revealed by moderate-S/N photographic spectra and are now being refined and extended to additional chemical elements and fainter stars with high-S/N data. The well-established features include overabundances of O and Ca, underabundances of s-process elements, and solar ratios of heavy r-process elements. An excess of nickel found by us on moderate-S/N spectra is less certain, and should be checked with high-S/N data. New information on oxygen abundances in Population II red giants is becoming available from high-S/N observations of weak [O I] lines, and consistently indicates an oxygen overabundance due to the preferential sampling in Population II stars of ejecta from massive stars of previous generations. Recent studies of highly evolved, post-AGB Population II stars are revealing remarkable overabundances of light elements (C, N, O, and S) and deficiencies of the heaviest elements; these are probably signatures of internal nucleosynthesis followed by mixing up to, or exposure by mass loss at, the stellar surface.
The Effect of Non-LTE and Atmospheric Perturbations on Relative Abundance Determinations in Metal-Poor Giants
Authors: Peterson Ruth C.
Published: July 2016

This paper reports an abundance analysis of spectra of 10 extremely metal-poor giants, including two in the globular cluster M92, in collaboration with Robert Kurucz and Eugene Avrett of the Center for Astrophysics and Bruce Carney of the University of North Carolina. An intercomparison of equivalent widths indicates that Luck and Bond have seriously overestimated the strengths of very weak lines and so deduced a spuriously high nickel abundance in the most metal-poor stars. A review of line-formation effects in the Sun strongly suggests that the rather high metallicities found for some extremely metal-poor stars by Pilachowski and coworkers is due to errors in their solar gf values, which unfortunately are unpublished. In our own analyses, stars with asymmetric H-alpha line profiles tend to have an excitation temperature at odds with the effective temperature found from infrared photometry. The discrepancy is removed by lowering the surface temperature by 100 K or by increasing the microturbulent velocity, either by a constant 0.5 km/s or by an amount which increases toward the surface. These changes have the most impact on those abundances deduced from strong lines or low-excitation lines of the neutral species; this includes sodium and barium as well as all the Fe I lines with very accurate gf values. Despite these difficulties, our findings reveal a low abundance for M92, and intrinsic scatter in the relationship between the relative abundances of sodium and oxygen and the overall iron abundance. In one field star, oxygen is apparently overabundant by an order of magnitude or more, while in the two M92 giants, the sodium abundance appears to differ by nearly this much.
Line-Blanketing in Theoretical Model Atmospheres for F, G, and K-Type Stars
Authors: Buser Roland , Kurucz Robert L.
Published: July 2016

We have computed improved flux distributions from Gustafsson et al.'s extensive grids of theoretical model atmospheres for late-type (F-K) giant and dwarf stars. In order to enhance the realism of the computed fluxes throughout the optical and the ultraviolet wavelength ranges, the massive list of atomic opacity sources used for the hotter Kurucz models was also employed in calculating the cooler spectra. For both the giant and the dwarf models, the resulting synthetic UBVRI photometry provides excellent matches to the spectroscopic calibrations of the observed metallicity and temperature scales based on the ultraviolet excesses, δ (U-B), and the BVRI colors, respectively. We conclude that atomic line-blanketing due to known, rather than “missing”, opacity sources accounts for the largest fraction of the systematic UV discrepancy existing between observations and earlier model calculations.
Abundances of Heavy Elements in the Magellanic Clouds
Authors: Russell Stephen C. , Bessell Michael S. , Dopita Michael A.
Published: July 2016

This paper provides the first reliable determination of the iron abundance of the Magellanic Clouds. There is clear evidence for carbon and nitrogen depletion, with respect to iron, in the Clouds which can be explained by the relative youth of the Clouds compared to our own Galaxy. Oxygen depletion relative to iron is also in evidence and it is suggested here that this is due to preferential loss of ejecta from high mass stars. Finally, our discovery of an extremely low abundance star in the SMC, coupled with the identification of a similar star by Spite et al. (1987), calls in to question whether or not the SMC is indeed a well mixed system as previously assumed.
The Spectral Evolution of the LMC S Dor Variable R127 During Outburst
Authors: Stahl O. , Wolf B.
Published: July 2016

The LMC star R127 was classified as O Iafpe extr. by Walborn (1977). Later, Walborn (1982) noted the spectral similarity to late WN stars and classified R127 as Ofpe/WN9 star. Stahl et al. (1983) discovered an S Dor outburst of R127. It has now been monitored photometrically almost continuously for more than four years. In addition, several high-dispersion and high signal-to-noise spectra were taken with the ESO CASPEC and CES spectrographs. In 1986 R127 became the visually brightest star of the LMC until it was surpassed by SN1987A in Feb. 1987.
Abundance Clues to Early Galactic Chemical Evolution
Authors: Truran James W.
Published: July 2016

High S/N spectroscopic studies of the abundance patterns characterizing extremely metal-deficient halo field stars and globular cluster stars have served to provide significant clues to and increasingly stringent boundary conditions upon the chemical evolution of the halo population of our galaxy. Guided by our current knowledge of nucleosynthesis as a function of stellar mass occurring in stars and supernovae, we identify some interesting constraints that these combined observational and theoretical considerations impose upon theories of the early history of our galaxy.
The 12C/13C Ratio in Barium Stars
Authors: Jorissen A.
Published: July 2016

It is suggested that the position of BaII stars with respect to normal red giants in the (log L, 12C/13C) and ([C/Fe],12C/13C) diagrams supports the hypothesis that 13C(α,n)16O was the neutron source responsible for the synthesis of the heavy elements now present in the BaII star envelopes.
Concluding Suggestions for Future High S/N Spectroscopic Work on Stars
Authors: Nissen P. E.
Published: July 2016

A summary of the main subjects discussed at this symposium is given, and some suggestions for future high signal-to-noise spectroscopic work, which could have a major impact on our understanding of the physics of stars and on astrophysics in general are presented.
Main Results of Studying the Nature of the Irregularity of the Earth's Rotation
Authors: Sidorenkov N. S.
Published: July 2016

The variations of the atmospheric angular momentum were investigated (Sidorenkov, 1976). Using the climatic cross-sections of the zonal wind, the values of the relative angular momentum of the atmosphere, h, were calculated for each month. The variations of h during the year are shown in Figure 1, where curve 1 illustrates the sum of h for the entire atmosphere, and curves 2 and 3 illustrate h for the atmospheres of the northern and southern hemispheres respectively.
Some Advantages and Disadvantages of a Photographic Zenith Tube
Authors: McCarthy Dennis D.
Published: July 2016

The theory and instrumentation of a photographic zenith tube (PZT) have been described by various authors (Torao, 1959; Markowitz, 1960; Thomas, 1964; Schuler, 1968; Takagi, 1974). Analysis of the more recent results of the PZT's of the U. S. Naval Observatory at Washington, D. C. and Richmond, Florida, permit the determination of precision and accuracy estimates which may be expected from the daily operation of a PZT. This analysis shows precisions of in latitude and in time, determined from the internal error of one sight. Accuracies estimated from the external error of a sight were found to be in latitude and in time.
Tidal Perturbations in Astronomical Observations
Authors: O'Hora N. P. J. , Baker T. F.
Published: July 2016

Twenty years of time and latitude observations made with the Herstmonceux Photographic Zenith Tube have been analysed to determine the phase and amplitude of deflexions of the local vertical at the frequency of the semi-diurnal M2tide. The results have been compared with predictions incorporating new calculations of the gravitational attraction due to the M2tides in the surrounding seas. The effects of the zonal Mmand Mftides on the time observations have also been determined and compared with existing theory. In both cases the agreement is reasonably good.
(α−2L) Terms as Obtained from PZT Observations
Authors: Iijima Shigetaka , Fujii Shigeru , Niimi Yukio
Published: July 2016

Periodic terms with arguments such as (α−2L) and (2α−2L) etc. which appear via various phenomena in the results of time and latitude observations by PZT are summarized in analytical forms in order to clarify their mutual relation. Numerical values in time and latitude for these terms to be expected at the Tokyo PZT are also given. From the data of time observations obtained by the Tokyo PZT during the past 15 years, amplitudes of the terms, cos(α−2Lα) and sin(2α−2Lα) in time, are obtained as +0.72 and 1.21 ms, respectively. These results give the value of (l+k-ℓ) as 1.14, and the values of nutation coefficients for 2L, and
On the Coordinate Systems Used in the Study of Polar Motion
Authors: Fedorov E. P.
Published: July 2016

IAU Symposium No. 78 “Nutation and the Rotation of the Earth” held in Kiev in 1977 revealed a certain lack of precision in the fundamental concepts and some looseness of terminology employed in the treatment of this problem. When talking about polar motion we should give, first of all, rigorous conceptual definitions of both the pole and a reference frame in which it moves. The selection of a reference system was the topic of an IAU Colloquium held in Torun in 1974. Although the discussion there was thorough and comprehensive, it did not result in the removal of all ambiguities which have tarnished discussion of the problems in the understanding of the Earth's rotation.
Coordinates of the Pole for the Period 1968–1974 Computed in the System of 10 Stations with Small Variations of Mean Latitudes
Authors: Kolaczek B.
Published: July 2016

The polar orbit was computed in a system of ten stations with small variations of mean latitudes and compared with the polar orbit based on ten stations with large variations of mean latitudes.
Time and Latitude Programs at the National Observatory of Brazil
Authors: Barreto Luiz Muniz
Published: July 2016

The National Observatory of Brazil was established in 1827 to study the problems of latitude and time. Time and latitude programs are still an important part of its work, but are now accompanied by increasing activity in the fields of geophysics, astrophysics and radio astronomy.
The Longitude Difference Merate - Milano Derived from Danjon Astrolabe Observations by Means of an One Step Adjustment Using an Extended Model
Authors: Kaniuth Klaus , Wende Werner
Published: July 2016

As a part of the establishment of a unified longitude system for the European Triangulation Network the difference in longitude between the reference points Merate and Milano was measured with a Danjon Astrolabe. This paper describes the results of a one-step adjustment of these observations including additional parameters for effects like personal equations and catalogue errors.
The NAVOBSY/NRL Program for the Determination of Earth Rotation and Polar Motion
Authors: Johnston K. J. , Spencer J. H. , Mayer C. H. , Klepczynski W. J. , Kaplan G. , McCarthy D. D. , Westerhout G.
Published: July 2016

The joint program of NAVOBSY/NRL is discussed.

The United States Naval Observatory (NAVOBSY) and the Naval Research Laboratory (NRL) are collaborating in a program to apply radio interferometric techniques to the determination of variations in Earth rotation, polar motion, and improved astronomical position reference systems. Investigations of VLBI and connected interferometer techniques and radio sources for astrometic application have been in progress for several years as part of the NRL radio astronomy program, and currently NRL and NAVOBSY are carrying out experimental programs to investigate VLBI time transfer techniques and UT determination using the connected element interferometer of the NRAO in Green Bank. Some previous results of observations using the Green Bank interferometer and proposed plans for operation as a dedicated system over a period of time to evaluate effectiveness for precise determination of Earth rotation parameters are discussed.
Precision Estimates of Universal Time from Radio-Interferometric Observations
Authors: Walter H. G.
Published: July 2016

Considerable improvement in the determination of the motion of the Earth is possible by the potentially high accuracy inherent in very-long-baseline interferometry. Precisions of UT1 are estimated from time delay and fringe frequency measurements of extragalactic radio sources with positional uncertainties at the level. Case studies resulted in standard deviations about one order of magnitude smaller than those obtained by classical astrometric methods. The dependence of estimates on baseline orientations and source declinations is discussed.
On the Effective Use of Lunar Ranging for the Determination of the Earth's Orientation
Authors: Silverberg Eric C.
Published: July 2016

Lunar ranging data have been routinely available since September of 1970, but many problems of a varying nature have delayed the establishment of a world-wide lunar ranging network. As a result, we must re-examine the role which this program can play in the determination of the Earth's rotation and polar motion. Although there are many technical difficulties now inhibiting the widespread use of this technique there seems little doubt but that we can overcome these problems and achieve routine, accurate orientation determinations. The more difficult questions concern how an Earth rotation campaign should now be configured to use the equipment and resources in the best way.

Despite considerable progress by other techniques, the failure to develop a lunar capability for Earth orientation determinations would result in a serious loss of information. Lunar monitoring of long-term effects in the Earth's rotation rate and the relationship of the lunar orbital parameters to a stellar reference frame are two tasks for which there is little redundancy. However, the most cost-effective usage of station resources may not require daily measures, but only periodic, accurate snapshots of the Earth's rotational position relative to the Moon. If some satellite laser ranging facilities could treat the Moon as an object of opportunity, but were able to elevate the program to priority status when global conditions were favorable, the incremental cost of gathering the required lunar data might be drastically reduced. Even though these cost savings could not be achieved without daily communication between cooperating stations, such a detailed interaction is not unreasonable to consider.
Is Lunar Ranging a Viable Component in a Next-Generation Earth Rotation Service?
Authors: Mulholland J. Derral
Published: July 2016

Several new “space” techniques have been used for episodic determination of Earth rotation parameters, usually the variation in apparent longitude (UT0) and apparent latitude of an observing station. Earth rotation services require more than episodic determinations; they need near-daily determinations. Since 1975, planning has been underway for a demonstration of the viability of lunar laser ranging for such a usage. The observing campaign named Earth Rotation from Lunar Distances (EROLD) was organized with the proposed activity to cover the years 1977–78. Progress has not been so rapid as hoped, but it remains true that lunar ranging has produced more Earth rotation information than other new techniques.
Quiet Sun at Metric and Decametric Wavelengths
Authors: Lantos P.
Published: July 2016

In 1950, a few years after the detection of the Sun at radiowavelengths by Southworth (1945), two important points were already established:

1

— The theory (Martyn 1946, Ginzburg, 1946) indicates that the thermal bremmstrahlung is dominant.

2

— The transfer calculations by Smerd (1950) and the total flux measurements (Pawsey 1946, Pawsey and Yabsley, 1949) lead to a coronal temperature of one million degrees.
Microwave Emission from Flaring Magnetic Loops
Authors: Vlahos Loukas
Published: July 2016

We discuss the microwave emission from a flaring loop (Spicer 1977). In particular we examine the following question: What will be the characteristics of the radio emission at centimeter wavelengths from a small compact flaring loop (average plasma density ne ≃ 1010 cm−3, average magnetic field at the footpoint of the loop Bℓ ≃ 500 gauss and Bt ≃ 100 gauss at the top of the loop and length of the loop, L = 109 cm), when the mechanism which pumps magnetic energy into the plasma in the form of heating and/or electron acceleration satisfies the following conditions. a. The magnetic energy is released in a small volume, (the energy release volume (ERV)), compared to the volume of the loop, and the rate at which magnetic energy is transformed into plasma energy is faster than the energy losses from the same volume. This causes a local enhancement of the temperature by as much as one or two orders of magnitude above the coronal temperature. b). The bulk of the energy released goes into heating the plasma and heats primarily the electrons (Te > Ti). Using these two assumptions one can easily show (Brown, Melrose and Spicer 1979, Vlahos and Papadopoulos 1979) that the high energy electrons in the tail of the velocity distribution in the ERV will instantaneously run away from this volume, and the resulting charge imbalance between the ERV and its surroundings (which still have average coronal temperatures ~ 106 K), will drive a return current, with velocity VD. When VD reaches the value of the local sound speed Cs ≃ 107 cm/sec low frequency ion acoustic waves will be excited at the interface of the ERV and its surroundings. It has been shown that the heat flow along the magnetic field lines is greatly reduced due to the presence of ion-acoustic turbulence (cf. Manheimer 1977). The bulk of the electrons in the ERV have electron-wave collision times **τw << 10–100 sec, longer than the impulsive phase of the flare. But since τw ~ v3 for those electrons with velocity v > ve (see Rudakov and Korablev 1966) the electrons in the tail will not “see” the ion sound waves and will stream freely towards the chromosphere.
Fast Fine Structure in Solar Microwave Flares
Authors: Slottje C.
Published: July 2016

A preliminary account is presented of some characteristics of Fast Fine Structure, that is fine structure with time scales in the milli second range, and of the flare events in which they appear. Fast Fine Structure is found to be a fairly common phenomenon that could, but not necessarily does, appear in flare events of any importance occurring at any longitude. It may occur with any type of microwave burst (except most likely “Rise” and “Fall”). It appears more often in the more important events and it may last for only a few seconds up to many minutes. Fast Fine Structure may have any degree of circular polarization, apparently independent of its longitude position.
Some Characteristics of Ultra-Fast Time Structures Superimposed on Impulsive mm-Wave Bursts
Authors: Kaufmann P. , Strauss F. M. , Opher R.
Published: July 2016

The use of increased sensitivity and temporal resolution at mm-wavelengths has revealed a number of novel features associated with solar activity (Kaufmann et al., 1979a). Of particular interest are the ultra-fast time structures superimposed on impulsive bursts. They are distinguished by time scales and repetition rates much shorter than the impulsive times scales. For weak bursts at λ = 13mm (i.e., few s.f.u.) the superimposed spikes are separated in time by several seconds. For moderate fluxes (i.e., 100 s.f.u.) the repetition rate of superimposed spikes is ~ 10–15 per second (i.e., time interval between two repeated spikes ~ 80 msec). For bursts larger than 500 s.f.u. the predicted times between repeated ultra-fast structures are shorter than 10 msec. Various examples have been studied with a time resolution better than 10 msec. (Kaufmann et al., 1979b). The impulsive flux level increases with the repetition rate of the ultra-fast component, following a nearly linear relationship. The simplest interpretation suggests that the injected spikes are associated with the bursting source function and are quasi-quantized in energy (Kaufmann et al., 1979b).
Solar Burst Observations at Metre and Decametre Wavelengths
Authors: McLean D.J.
Published: July 2016

Our success or failure in understanding solar bursts is largely determined by the kinds of instrument with which we observe them. For example, although the basic feature of Type II bursts, a slow drift from high to low frequencies, was recognized and correctly interpreted from radiometer measurements at a few frequencies (Payne-Scott et al., 1947) other properties of Type II bursts such as fundamental-harmonic structure, split bands and herringbone structure can only be recognized on dynamic spectrograms. For this review I have chosen to group together the observations made with a particular type of instrument. I have also tended to emphasize what remains to be done rather than what has already been done. Unfortunately, with so many topics to choose from my treatment can only be cursory; and in attempting to select the interesting topics I have inevitably been biased toward the work I know best - that is, the work of the group to which I belong.
Distribution Functions of Type III Electrons Observed in Interplanetary Space
Authors: Lin R. P. , Potter D. W. , Anderson K. A. , Fainberg J. , Stone R. G. , Steinberg J. L.
Published: July 2016

We present simultaneous energetic electron and solar radio observations from the ISEE−3 spacecraft of several solar type III radio bursts. The UC Berkeley energetic particle experiment measures from 2 to ~ 103 keV with good energy and pitch angle resolution while the Meudon/GSFC radio experiment tracks type III radio bursts at 24 frequencies in the range 30 kHz—2 MHz.
Polarization and Position Measurements of Type III Bursts
Authors: Suzuki S. , Dulk G.A. , Sheridan K. V.
Published: July 2016

We report on the positional and polarization characteristics of Type III bursts in the range 24–220 MHz as measured by the Culgoora radioheliograph, spectrograph and spectropolarimeter. Our study includes 997 bursts which are of two classes: fundamental-harmonic (F-H) pairs and “structureless” bursts with no visible F-H structure. In a paper published elsewhere (Dulk and Suzuki, 1979) we give a detailed description and include observations of source sizes, heights and brightness temperatures. Here we concentrate on the polarization of the bursts and the variation of polarization from centre to limb. The observed centre-to-limb decrease in polarization approximately follows a cosine law. This decrease is not as predicted by simple theory but is consistent with other observations which imply that open field lines from an active region diverge strongly. The observed o-mode polarization of harmonic radiation implies that the wave vectors of Langmuir waves are always parallel, within about 20°, to the magnetic field, while the constancy of H polarization with frequency implies that the ratio fB/fP, the Alfvén speed vA and the plasma beta are constant with height on the open field lines above an active region. Finally, we infer that some factor, in addition to the magnetic field strength, controls the polarization of F radiation.
Theory of Type IV dm Bursts
Authors: Kuijpers Jan
Published: July 2016

The study of fine structures in continuum radio emission from the sun is important to probe the physics of radio sources and of flares in particular. In this light the existing fine structure theories are reviewed and an application to a radio flare is given.
Type I Radio Emission and the Structure of the Solar Corona Results of the Stereo-I Experiment
Authors: Bougeret J. L. , Steinberg J. L.
Published: July 2016

High resolution spatio-temporal observations of noise storms in the meter wavelength range show the existence of many center-limb effects. We show that these effects cannot be interpreted without appealing to scattering effects which must take place close to the primary source of electromagnetic radiation. This contradicts STEREO-1 observations of very directional radiation which require that the scattering takes place far from the primary source, in order to be consistent with the observed source sizes. Using other results of the STEREO-1 Experiment, we suggest a model for the noise storm region in which the Type I bursts are emitted by gyromagnetic radiation of electron packets. The emission is very directional and oriented in the direction of the local magnetic field. The various center-limb effects and the spatio-temporal behavior can be explained using strong scattering effects in a fibrous medium.
Satellite Observations of the Outer Oorona Near Sunspot Maximum
Authors: Michels D. J. , Howard R. A. , Koomen M. J. , Sheeley N. R.
Published: July 2016

This paper shows the first satellite observations of the Sun's white light corona (2.6 R⊙ −10.0 R⊙) during the active phase of a sunspot cycle. Since March 28, 1979, these observations have been obtained routinely with a spatial resolution of 1.25 arc min and a repetition rate of 10 minutes during the one-hour sunlit portion of each 97-minute satellite orbital period. As an illustration of these new observations, we show the coronal changes associated with the great mass ejection of May 8, 1979.
On the Possibility of Radio Observations of Current Sheets on the Sun
Authors: Syrovatskii S.I. , Kuznetsov V.D.
Published: July 2016

Possibility of a discovery of current sheets in the radioband by using their screening and reflective properties as also their own emission is discussed. It is shown, that the thermal bremsstrahlung of the sheet may be of a sufficiently large intensity on the maximal critical frequency for the plasma in the sheet. In dependence from electron density No and temperature Ts the thickness of the sheet from tens centimetres to hundreds metres is sufficient to provide optical depth Spectral observations with sufficient angular resolution may give such characteristics of the sheet as its temperature, electron density, thickness and height in the solar atmosphere.
Optical Variations of the Be Star HDE 245770/A 0535+26
Authors: Guarnieri A. , Bartolini C. , Piccioni A. , Giangrande A. , Giovannelli F.
Published: July 2016

Results of photoelectric observations of HDE 245770 spreaded over six years are presented. No variations greater than some hundreths of magnitudes are evident in contrast with the ancient light history, which is more complex. A sensible variation of the colour indices is present on a time scale of tens of years. The temporal analysis of these data shows some evidence of orbital periodicity.
Simultaneous Spectroscopic and Polarimetric Observations of π Aqr
Authors: Metz Klaus
Published: July 2016

Simultaneous spectroscopic and polarimetric observations of about 40 bright southern Be stars have been carried out by Dr. Pöllitsch and myself with the ESO 1.5m coudé spectrograph and with the ESO two channel polarimeter.
Spectroscopic Observations of Be Stars in the Photographic and Visual Regions
Authors: Slettebak Arne
Published: July 2016

The term “Be star” has been used at times to describe classes of objects which are physically rather different from one another. While it could include early-type supergiant stars with Hα emission, early-type pre-main sequence nebular variables, or quasi-planetary nebulae like MWC 349, I will limit this review paper to a discussion of the “classical” Be stars. These are defined as stars of luminosity classes III to V, usually rapid rotators, which show normal B-type spectra with superposed Balmer (and sometimes Fe II) emission. Included also, however, will be the Oe stars and the A-type shell stars, which seem to represent extensions of the classical Be phenomenon to higher and lower temperatures, respectively.
Results of a New Survey for Early-Type Emission Stars
Authors: MacConnell D.J.
Published: July 2016

We discuss the discovery, on objective-prism plates, of 846 stars showing Hα in emission on non-banded spectra. These stars have not previously been reported to have emission and are located primarily along the southern galactic plane. Twenty-six per cent. of the stars are known to be of type AO or earlier.
On the Radiation Deficiency of Shell Stars in the Balmer Continuum
Authors: Chkhikvadze J. N.
Published: July 2016

The present report gives the results of a statistical comparison of shell stars with normal Be stars to establish the differences in the parameters of the gaseous envelopes, such as the radiation power in the Paschen continuum and the optical depth of the envelopes in the Balmer continuum.
Intensifier-Dissector-Scanner Observations of the Bright Northern Be Stars
Authors: Barker Paul K.
Published: July 2016

Early results are presented from an extensive program of regular Balmer-line spectroscopy; during eight months in 1980 Hα profiles were obtained of over 100 northern Be stars. Transient emission events have been observed in the very early rapid rotator 59 Cygni; sequential variations in Hα are quasi-periodic.
Optical Spectroscopy of HD102567 (4U1145-61)
Authors: Pacheco Eduardo Janot , Chevalier C. , Ilovaisky S. A.
Published: July 2016

Analysis of optical spectra of HD102567 (HEN 715), the optical counterpart of the X-ray source 4U1145-61 is presented. Estimates of the star's rotation velocity, inclination angle, distance and envelope characteristics are given. Some consequences of the possible existence of a 190d orbital period for this Be/X-ray sources are discussed.
The Variable Shell Phase of HD 184279 between 1976 and 1980
Authors: Ballereau D. , Hubert-Delplace A.M.
Published: July 2016

The variable shell (H, HeI, FeIII and once ionized other metals) B0.5 star HD 184279 presents variations of radial velocity and line profiles with a cycle of about 4 years. Some correlations between photometric and spectroscopic data are found. A comparison with 48 Lib and ζ Tau is given.
Radial Velocity Variations in 69 Orionis
Authors: Bossi M. , Guerrero G. , Mantegazza L.
Published: July 2016

69 Ori (B5 V) was discovered as a Be star in 1976 (Doazan et al., 1977). We observed this object at the Merate Observatory during the periods Nov. 77. - Jan. 78 - Jan. 78 and Oct. 78 - Feb. 79 obtaining 20 red spectrograms and 25 blue ones with a dispersion of 35 Å/mm. We performed also B and V photo-electric observations during 12 nights altogether. The results from the red spectra and the photometric measurements have been discussed by Bossi et al. (1981).
On Periodic Variations in the Spectrum of the BOe Star X Persei Associated With the X-Ray Source 3U 0352+30
Authors: Galkina T.S.
Published: July 2016

The bright BOe star X Persei has been observed for over fifthy years, both as an emission line object and as a variable star.
Infrared Photometry of Be Stars
Authors: Feinstein Alejandro
Published: July 2016

A photometric study of Be stars in the JHKL system is reported here. Early papers (see Feinstein and Marraco, 1980) about bright southern Be stars observed photoelectrically in the UBVRI system and in the Balmer-lines: Hα, Hβ and Hγ, permit us to derive several conclusions about their light variability, the amount of emission in the α and β indices, and some correlations about these data. On the other hand, we recently found (Feinstein and Marraco, 1981) that the emission strengths of the hydrogen lines are well correlated to the amount of excess radiation in the near-in-frared of the RI system.
Search for Variability in Near Infrared Fluxes of Peculiar Emission-Line Objects
Authors: Bouchet P. , Swings J. P.
Published: July 2016

Thirty-five peculiar emission line objects (essentially B[e] stars) were observed at J(1.2 μ), H(1.6 μ), K(2.2 μ), L(3.5 μ), and M(4.8 μ) at the E.S.O. 1 m telescope where the photometer is equipped with an InSb detector. The results of the observations performed during several nights and days in Feb. 1979 and March 1980 are listed in Table 1.
A Catalogue of Hα Observations
Authors: Ducati J. R.
Published: July 2016

A catalogue of quantitative observations of Hα published between 1949 and 1980 has been prepared. It contains 4095 measurements concerning 2700 stars.
X-Ray Observations of Be Stars
Authors: Rappaport Saul , Van Den Heuvel Edward P.J.
Published: July 2016

Be star binaries with neutron star companions are shown to constitute a major class of X-ray sources. Some general observational and interpretive techniques of X-ray astronomy are reviewed. Data for 12 Be/X-ray binary systems are summarized. The Be/X-ray binaries are found to be systematically wider systems, with lower-mass primaries, and with significantly more transient behavior than the “standard” massive X-ray binaries such as Cen X-3 and SMC X-1. The difference between the two types of X-ray binaries is explained in the context of slightly different evolutionary scenarios for the progenitor binaries. The “standard” massive X-ray binaries result from wind-mass-loss dominated evolution of very massive close binaries, while Be/X-ray binaries probably result from mass-transfer dominated evolution of systems with primary masses ≲ 20 M⊙. The implications of the X-ray observations of Be/X-ray binaries for Be stars in general are discussed.
Be Components in X-Ray Binaries
Authors: de Loore C. , Burger M. , van Dessel E.L. , Mouchet M.
Published: July 2016

The Be X-ray binaries show rather weak and variable X-rays. They can be divided into two types, the transient sources and the permanent sources. Two ranges for the X-ray luminosity Lx can be discerned: a) Lx~1034erg s−1 (X Per, λ Cas, 2S0114+65, all permanent sources); b) Lx~1036erg s−1. They have long periods, hence wide orbits, they ar not eclipsing and their mass loss rates are low. The optical spectra are generally very variable and irregular, masking periodic changes. No optical orbits exist and only for 4U0115+63 an X-ray orbit is known (Rappaport et al.1978). An overview of the Be X-ray binaries with some of their characteristics is given in Table 1.
Are Classical Be Stars Sources of Hard X-Rays?
Authors: Peters Geraldine J.
Published: July 2016

A point summation technique was used to search the UHURU data base for X-ray emission from classical Be stars. Of the thirty-two stars considered, only three (λ Cas, HR 4009, and HD 187399) were detected at the 3.3σ level or higher. For reasons discussed in this paper, HD 45314, π Aqr, κ Dra, and 48 Per are considered to be possible detections. The X-ray emission from λ Cas from late 1970 through early 1973 is discussed.
Spectroscopic Investigations of Herbig-Ae-Be-Stars
Authors: Finkenzeller Ulrich
Published: July 2016

“Herbig-Ae-Be-Stars” are assumed to be pre-main sequence objects of moderate mass with line emitting envelopes of an unknown nature. From our present theoretical knowledge it is not clear whether the physical structure of these envelopes is dominated by mass accretion or mass loss induced by a stellar wind or radiation pressure effects. Radial velocities and remarks on peculiarities are given for the star HD 200 775, which seems to represent a typical Herbig-Ae-Be-star fairly well. A catalogue of about 60 supposed Herbig-Ae-Be-stars is presented and comments, in particular on the brighter members, are invited.
Shapley's Era
Authors: Hogg Helen Sawyer
Published: July 2016

I am greatly pleased to have a chance to speak at this Symposium about Harlow Shapley, the man who was probably responsible, more than any other, for the shape my life has taken.

In my talk this morning I am repeating a few of the remarks I made at the Centennial Celebration for the birthday of Harlow Shapley last October 17 at the Harvard College Observatory. Some of the people here today were present then, and I trust they will excuse the repetition. But my talk today has a different slant.
Shapley's Impact
Authors: Gingerich Owen
Published: July 2016

Harlow Shapley's legacy can be divided into three aspects: his scientific contributions, the institutions he built, and his multi-faceted efforts to publicize astronomy. Today's public funding of science undoubtedly owes much to Shapley's enthusiasm for astronomy.
Globular Cluster Color-Magnitude Diagrams
Authors: Hesser James E.
Published: July 2016

This review concentrates on new generalities emerging from this, the second “golden era” of B,V color-magnitude diagrams (CMDs), and remarks about future work in other photometric systems.
The Chemical Inhomogeneity within Globular Clusters
Authors: Norris John
Published: July 2016

Twenty years ago it was believed by most astronomers that globular clusters were chemically homogeneous - where by homogeneous one means that the outer layers of all stars within a given cluster are the same to within a few tens of percent. Today it is possible to defend the case that no Galactic globular cluster has this characteristic. The reason that this phenomenon has exercised the minds of so many groups in the past 15 years is exciting and obvious: if one can ascertain which are the relevant physical processes in operation, one stands to gain significant insight into both the way in which globular clusters formed and/or the way in which individual low mass stars evolve and mix the products of their nucleosynthesis into their outer layers. A second important driver at the back of the minds of workers in this field is the possible ramifications of an understanding of the phenomenon; for example, if one concludes that the abundance anomalies are being driven today by some particular effect (angular momentum, magnetic fields, interactions within binary systems, stellar collisions - or whatever) this may lead to insight into other important globular cluster phenomena (eg bimodal horizontal branches, gaps at the base of the giant branch, horizontal branch rotation, etc.)
Ages of the Galactic Globular Clusters
Authors: Vandenberg Don A.
Published: July 2016

Using stellar evolutionary models which have been computed for the preferred set of element abundances, ages of 13-14 Gyr are derived for the Galactic globular clusters. No significant (> 1.5 Gyr) spread in age is found as a function of either metal content or galactocentric distance. The lack of an age-metallicity relation is shown to be contingent upon the assumption that [O/Fe] is anticorrelated with [Fe/H]: the use of scaled solar abundance calculations would predict that the most metal-poor systems are about 3 × 109 yr older than the most metal-rich clusters. Some evidence in support of high oxygen-to-iron ratios is discussed.
Cluster Swapping
Authors: Muzzio Juan C.
Published: July 2016

The investigation of globular cluster swapping in clusters of galaxies has resulted in some interesting theoretical findings and, at the same time, it offers a promising field for observers. Numerical simulations of galaxy clusters where the galaxies have swarms of test particles around them showed that, in addition to tidal stripping, tidal accretion plays an important role in the dynamical evolution of clusters of galaxies; it also turns out that, even in clusters where the gravitational field is dominated by a massive background, the galaxy-galaxy attraction cannot be ignored when estimating the outcome of collisions. Cluster swapping is just an example of tidal accretion and, taking the globulars as probes of halo material, it might offer an opportunity to observe some consequences of that effect; besides, although the difficulties look formidable at present, the study of globulars lost through tidal stripping is a possibility that should not be neglected. Tidal stripping and accretion processes are very sensitive to the ratio of galactic mass to total mass, so that observations related to the cluster swapping phenomena may provide a new means to investigate the missing mass problem.