bluuebunny/crossref_metadata_2025 huggingface dataset:
Redshift Estimates for Distant Radio Galaxies Based on Broadband Photometry
Authors: Puschell J. J. , Owen F. N. , Laing R.
Published: July 2016

Calculations modeling the effects of stellar evolution on elliptical galaxies (e.g., Bruzual and Kron 1980, Bruzual 1981) suggest that the shape of the spectral flux distribution should remain almost constant in the red and near-infrared out to at least z ∼ 2. Thus, it should be possible to derive the redshift of a distant elliptical galaxy by fitting a model galaxy spectrum to broadband near-infrared (RIJHK) photometry.
Space Distribution of Ouasars Based on Optically Selected Samples
Authors: Schmidt Maarten , Green Richard F.
Published: July 2016

Even though the number of known quasars is approaching 2000, relatively few belong to well defined complete samples which are needed to derive their space distribution. For many years, the Braccesi survey (Braccesi, Formiggini, and Gandolfi 1970) was the only published one — its limited spectroscopic coverage allowed construction of only a small complete sample of 19 quasars brighter than B = 18, over an area of 36 sq. deg.
The Effective Temperatures of Early Wolf-Rayet Stars
Authors: Schmutz Werner
Published: July 2016

Nussbaumer et al. (1981) (NSSW) have calculated temperatures of 15 Wolf-Rayet stars, which cover most subtypes in the WN and WC sequences. Some Wolf-Rayet stars are found to have a blackbody-like energy distribution and therefore their effective temperature can be well determined, others show deviation from the blackbody shape. This deviation is probably due to an extended continuum emitting region. In view of these later cases NSSW adopted a temperature which they derived from a Zanstra analysis of the He II recombination lines. According to their analysis there should be a continuum jump at 2050 å. New IUE observations of the WN 5 star HD 50896 however did not show any trace of such an absorption edge. This implies that the effective temperature of this WN 5 star and probably of all WR stars with a non blackbody energy distribution is not yet known accurately. Therefore we started a detailed analysis with a spherically symmetric atmosphere model. Though the model has not yet reached its final shape we have obtained as a first result that the location of HD 50896 in the HR-diagram is to the left of the ZAMS and that the Zanstra analysis is indeed not valid for this star.
Chemical Composition of Wolf-Rayet Stars: Abundant Evidence for Anomalies
Authors: Garmany C. D. , Conti P. S.
Published: July 2016

We have observed 45 WN stars in our Galaxy and the LMC with the IUE satellite at a resolution of 6 å. Examination of the spectra reveals surprising differences in line strength, in many cases at a given spectral subtype. This is similar to the description of the visual spectra given by Leep (1982). One generalization that can be made is that the equivalent width of He II λ1640 is correlated with the H/He ratio measured by Perry and Conti (1982), but not with spectral type.
On the Chemical Abundances, Evolutionary Stage and Bolometric Magnitude of WR Stars
Authors: Vanbeveren D.
Published: July 2016

I will comment on 3 problems concerning WR stars:

a.

are WR stars core hydrogen/core helium burning?

b.

are WR stars H-poor or do they have normal abundances?

c.

can we use B.C. for WR stars which are similar as for 0 stars?
Carbon Abundance in the WC 11 Star CPD −56°8032
Authors: Houziaux L. , Heck A.
Published: July 2016

The star CPD −56°8032 is one of the few objects classified WC 11. First noted by Bidelman, MacConnell and Bond (1968), its blue-violet spectrum has been described by Cowley and Hiltner (1969), while the red/infrared region has been studied by Thackeray (1977). Infrared magnitudes have been measured by Webster and Glass (1974), and Aitken et al. (1980) have scanned the infrared spectrum from 8 to 13 µm. Cohen and Barlow (1980) have also published infrared fluxes from 3.45 to 20 µm. This star shows strong emission lines belonging to C II and C III, much sharper than the usual bands seen in WC stars. Bright lines of H, He I, O II, O III, Si III and Si IV are also present. O I λ 7774 triplet shows a P Cygni profile (Thackeray, 1977). Forbidden lines belong to [O I] (red lines), [O II] (violet and infrared doublets) [N II] (6548 and 6584 å), and [S II] (4068 and 6716 å).
The Influence of the Ratio of Total to Selective Extinction on the Determination of the Mass Loss Rate of Wolf Rayet Stars from Infrared Excess Measurements
Authors: The P.S. , van der Hucht K.A. , Arens M.
Published: July 2016

It is shown that the mass loss rate of the WN7 star HD 93162 decreases with larger values of the ratio of total to selective extinction R. for HD 93162 the mass loss rate will change one order of magnitude, only if ΔR ∼ 2. Mass loss rates are derived for nine other WR stars of which visual, red and near-infrared photometric observations were obtained.
Radio Continuum Measurements of Mass Loss from Wolf-Rayet Stars
Authors: Abbott David C. , Bieging John H. , Churchwell Ed
Published: July 2016

The Wolf-Rayet phenomenon is defined by the striking emission line spectrum which is observed at UV, optical, and IR wavelengths. The usual interpretation is that this characteristic emission-line spectrum results from a stellar wind which has such a high density that even relatively weak lines are formed in the extended envelope formed by the outflow. This model leads to the expectation that the Wolf-Rayet phenomenon is linked to stars which have very high rates of mass loss. The purpose of this paper is to examine the relationship between the mass loss rate and the spectral appearance of O, Of, and WR stars.
The Near Infrared Properties of Selected WN Stars in the Large Magellanic Cloud
Authors: Panagia N. , Tanzi E.G. , Tarenghi M.
Published: July 2016

We report here on preliminary infrared photometry of six WN stars in the Large Magellanic Cloud. Besides R136, the central object of the 30 Doradus Nebula, the sample includes three stars (R139, R140, R145) located near the center of the region (within ∼ 1 arcmin) and two more stars (R144, R147) at a distance of ∼ 5 arcmin from R136.
Wolf-Rayet Stars with Massive Companions
Authors: Massey Philip
Published: July 2016

The study of Wolf-Rayet binaries is important for the information we can gleam about the most fundamental property of any star: its mass. In this regard we are very fortunate, since the masses of WR stars can be determined with far greater confidence than can their luminosities, compositions, colors, effective temperatures, etc. By simply measuring the velocities of both components in a WR+0 system, we can find the minimum masses and the mass ratio of the two stars; if we can get some further handle on the orbital inclination, we then know the mass of the WR star directly.
Is HD 164270 a Long-Period Eclipsing Binary?
Authors: Lundström Ingemar , Stenholm Björn
Published: July 2016

The WC star HD 164270 (=WR 103 in the catalogue by van der Hucht et al., 1981) is one of the stars to which Smith (1968) ascribed variability, although she was not able to investigate the light variations completely. The star has been regarded as a single star (i.e. no evidence of absorption lines) but it has been proposed by e.g. van den Heuvel (1976) that “single” WR stars might have collapsed companions. Eclipses by such short-period companions should be observable. Thus we designed an observational programme to look for hitherto unobserved companions. The programme contained 16 “single” WR stars. Some of them, including WR 103, had previously shown light variations as mentioned.
The Velocity Field of S308. The Ring Nebula Around the WN5 Star HD 50896
Authors: Pişmiş Paris , Quintero Alfonso
Published: July 2016

Radial velocities are determined by Fabry-Pérot interferometry at 131 points of the ring nebula S308. The velocities have yielded a kinematic distance of 1.5 kpc for the object, and an expansion velocity of 45–60 km s−1. The ring nebula has a diameter of 13 pc and the age is estimated to be about 1.5 to 2×105 years.
The Massive Eclipsing Binary RY Scuti
Authors: Giuricin G. , Mardirossian F.
Published: July 2016

We have analyzed Ciatti et al's (1980) UBV lightcurves of the massive eclipsing binary RY Set. The BO primary, being considerably over-luminous and oversized for its mass, is certainly appreciably evolved. That this star is nearly filling its Robe lobe strongly supports the idea that it is undergoing a phase of mass transfer (case B), through Robe lobe overflow, towards its more massive secondary companion. In view of its properties, RY Set, which represents an uncommon evolutionary stage, is lively to evolve into a Wolf-Rayet binary systems.
The Occurrence of Different Wolf-Rayet Phases in Massive Close Binaries
Authors: Doom C. , De Grève J.P.
Published: July 2016

In a recent paper (Doom and De Grève, 1981) the remaining main sequence lifetime of the mass gaining component in massive close binary systems was computed. Using results of that paper and the definition of the four important events in the evolution of a massive close binary system (RLOF(M1), RLOF(M2), SN(M1), SN(M2)), four evolutionary stages in the life of the system can be defined: OB+OB, WR+OB, c+OB (or WR+WR) and c+WR. The two possibilities for the third stage depend on the initial mass ratio of the system. The final stage c+c, is not considered here.
A New Search for Nebulae Surrounding Wolf-Rayet Stars
Authors: Heckathorn Joy N. , Bruhweiler Frederick C. , Gull Theodore R.
Published: July 2016

We have used the plate data from An Emission Line Survey of the Milky Way by Parker, Gull and Kirschner(1979) to make a new search for ring nebulae around Wolf-Rayet stars. The Survey consists of narrow-band interference filter direct imagery centered on the emission lines of Hα + [N II] at λ6570, [O III] at λ5007, and [S II] at λ6730. We have discovered at least five new ring nebulae. of the fifteen ring nebulae we were able to detect on the Survey, including our new discoveries, eleven were brighter in the [O III] bandpass than in the Hα + [N II] bandpass, and were filamentary in [O III]. All of the nebulosities we were able to detect were rated on the basis of three criteria:

1)

Sharp, filamentary structure present in any or all bandpasses.

2)

Wolf-Rayet star centered in projected nebulosity, or, if off-center, the segment of the ring nearest the star proportionally brighter than the rest of the ring.

3)

Absence of any O stars within the nebulosity, or O star in off-centered position not adjacent to the brightest or sharpest portion of the ring.
The Central Object of the 30 Doradus Nebula, a Supermassive Star
Authors: Cassinelli Joseph P. , Mathis John S. , Savage Blair D.
Published: July 2016

The 30 Doradus nebula is the brightest H II region in the local group. Radio continuum and Radio recombination line observations indicate that it is photoionized by the equivalent of ∼100 05 stars. Observations of the central object R136 made at low and high spectral resolution with the IUE reveal a peculiar hot object with a massive stellar wind. An outflow speed of 3500 kilometers per second and a temperature of approximately 60,000 K are indicated by the spectra. The bulk of the observed ultraviolet radiation must come from R136a, the brightest and bluest component of R136. Its absolute visual magnitude and observed temperature imply a luminosity about 108 times that of the sun. Most of the ionizations produced in 30 Doradus are provided by this peculiar object. If R136a is a dense cluster of very hot stars, about 30 stars of classes 03 and WN3 exist in a region estimated to have a diameter of less than 0.1 parsec. This is inconsistent with the ultraviolet line spectrum and the evidence for optical variability. An alternative interpretation of the observations is that the radiation from R136a is dominated by a single super-luminous object with the following approximate properties: luminosity and temperature as given above, a radius 100 times that of the sun, a mass 2500 times that of the sun, and a loss rate of 10−3.5 solar masses per year. Model interior calculations for hydrogen-burning stars are consistent with these parameters. Such stars, however, are expected to be unstable, and this may account for the massive stellar wind.
Precise Radial Velocities of F, G, K Dwarfs
Authors: Campbell Bruce , Walker Gordon A. H.
Published: July 2016

We have monitored changes in the radial velocities of 24 bright F, G and K dwarf stars (known spectroscopic binaries excluded) for the past six years at CFHT by imposing the absorption lines of HF gas in the spectra to act as wavelength fiducials. The average external error in the δ(velocities) which are based on some 16 stellar lines is 13 m/s corresponds to 0.6 micron in the spectrum or 0.04 of a diode spacing per line. Reductions are complete for 16 stars. There is no evidence for brown dwarf companions in the sample. Two previously unknown spectroscopic binaries were found, and seven stars show indications of significant, long-term, low-level velocity variations which could be interpreted as purturbations by companions of a few Jupiter masses with periods greater than 12 years except for γ Cep, which may have a period of 2.7 years, and ε Eri. Observing time has been guaranteed for at least two more years at CFHT.
High S/N Simultaneous Optical and IR Spectrophotometric Observations of Herbig Ae/Be Stars
Authors: Vittone A. , Rossi C. , Covino E. , Giovannelli F.
Published: July 2016

We present a preliminary report on simultaneous optical and infrared observations on a sample of Herbig Ae/Be stars carried out at the European Southern Observatory in La Silla-Chile in March 1984 and in March-April 1985. In this paper Z CMa, V380 Ori, R Mon and HD53367 are analyzed A strong variability in both energy distribution and Ha line profile is detected in Z CMa, while for HD53367 only He I and Ha profile's variations are revealed; V380 Ori and R Mon show non significant variability.
Improved Non-LTE Model Atmospheres for Subluminous O-Stars
Authors: Heber U. , Hunger K. , Rauch T. , Werner K.
Published: July 2016

Improved non-LTE model atmospheres designed for the analysis of very hot subluminous O stars are presented. The calculations are based on the new method of the accelerated lambda iteration (ALI) which proves capable of treating up to 100 levels of various ions. Presented here are improved calculations for (i) pure hydrogen model atmospheres including Stark broadening, (ii) for hydrogen- and helium-composed model atmospheres and (iii) first preliminary models which include in addition a detailed carbon model atom. These models remove an apparent mismatch of Balmer line profiles noted previously and fit high S/N, high-resolution hydrogen and helium spectra obtained with the ESO-Cassegrain echelle spectrograph very well.
A Search for Coronal Emission Lines from Early-Type Stars
Authors: Baade D. , Lucy L. B.
Published: July 2016

For more than ten years now, a controversial issue in studies of stellar winds has concerned the existence or not of a coronal zone (T ∼ 106 K) at the base of the cool winds (T ∼ Teff) of early-type stars. The latest revival of interest in this possibility is due to Wolfire et al. (1985) who showed that Waldron's (1984) recombination stellar wind (RSW) version of the hot corona – cool wind model (Hearn 1975; Cassinelli et al. 1978) yields models for ξ Puppis (O4 If) that are consistent with both IRAS and Einstein IPC data, thus refuting an earlier claim (Lamers et al. 1984) to have excluded the existence of a coronal zone.
Doppler Images of Rapidly Rotating Ap Stars
Authors: Hatzes Artie P.
Published: July 2016

The magnetic Ap stars are characterized by the presence of large magnetic fields which undergo periodic variations. These magnetic field variations are accompanied by spectral variations caused by the inhomogeneous distribution of elements on the stellar surface. It is believed that the magnetic field plays an important role in determining this distribution. Accurate maps of the surface distribution of elements would provide valuable probes as to the field geometry as well as provide clues to the role of the magnetic fields in the atmospheres of these stars. We have developed a new technique for mapping the local equivalent width on a stellar surface from the observed spectral line variations.
Chromospheric Velocity Fields Diagnostics from CaII and MgII Emission Profiles
Authors: Vladilo G. , Crivellari L. , Castelli F. , Beckman J. E. , Foing B. H.
Published: July 2016

We discuss the present limits to the velocity field diagnostics in stellar chromospheres achievable with ESO CAT+CES and IUE high resolution spectra.
Accurate Spectroscopic Surface Gravities for 8 Sub-Giants
Authors: Edvardsson Bengt
Published: July 2016

Logarithmic surface gravities between 2.9 and 3.8 (cgs) have been determined for eight G8IV-K2III stars from the analysis of pressure broadened wings of strong metal lines. Comparisons with trigonometrically determined surface gravities give support to the spectroscopic results. A thorough and rather conservative error analysis suggests that the errors are smaller than about 30% and confirms that the method is very insensitive to uncertainties in the fundamental stellar atmospheric parameters. Surface gravities of α Cen A and B and of Arcturus have also been obtained. Chemical abundances have been derived for 12 elements from Na to Ni, and for five heavier elements from Y to Nd have tentative abundances been derived from a single line of each element. Effective temperatures in the photometric system of Frisk (1983) are found to be consistent with spectroscopic temperatures from the excitation equilibrium of Fe I. Surface gravities determined from the ionization equilibria of Fe and Si are found to be systematically lower than the strong line gravities, which may be an effect of errors in the model atmospheres, or departures from LTE in the ionization equilibria.
The Chemical Composition of Vega
Authors: Gigas Detlef
Published: July 2016

A non-LTE abundance determination of magnesium, iron, and barium was carried out for the atmosphere of Vega. The results indicate marked underabundances of these elements relative to the solar values. First preliminary results of numerical simulations of convective and oscillatory phenomena in the atmosphere of Vega are briefly described.
Detailed Analyses of Four Solar Analogs Analysed On High S/N CFH and ESO Spectra
Authors: Bentolila C. , de Strobel G. Cayrel
Published: July 2016

Four solar type G stars claimed to be photometrically very similar to the Sun have been analyzed in detail on high resolution, high S/N spectra. Their atmospheric parameters : effective temperature, spectroscopic gravity, microturbulence and iron abundance, [Fe/H], have been determined.
A High S/N Spectroscopic Survey of Chemical Abundances in Disk Population F0-G2 Dwarfs
Authors: Andersen J. , Edvardsson B. , Gustafsson B. , Nissen P. E.
Published: July 2016

In collaboration with D. Lambert and J. Tomkin high resolution, high S/N spectra have been obtained for about 250 disk population F0-G2 dwarfs. The aim of this large programme is to study various abundance ratios as a function of [Fe/H] and stellar age. A detailed description of the project and some preliminary results were given by Nissen et al. (1985).
Distribution of R- and S-Process Elements in the Galactic Halo
Authors: Sneden C. , Pilachowski C. A. , Gilroy K. K. , Cowan J. J.
Published: July 2016

Current observational results for the abundances of the very heavy elements (Z>30) in Population II halo stars are reviewed. New high resolution, low noise spectra of many of these extremely metal-poor stars reveal general consistency in their overall abundance patterns. Below Galactic metallicities of [Fe/H] Ã −2, all of the very heavy elements were manufactured almost exclusively in r-process synthesis events. However, there is considerable star-to-star scatter in the overall level of very heavy element abundances, indicating the influence of local supernovas on element production in the very early, unmixed Galactic halo. The s-process appears to contribute substantially to stellar abundances only in stars more metal-rich than [Fe/H] Ã −2.
The Sulphur Abundance in Metal Deficient Dwarfs
Authors: Francois Patrick.
Published: July 2016

The study of the chemical composition of metal deficient dwarfs is very interesting because thse stars have been formed at different epochs and their atmosphere is representative of the chemical composition of the gas at the time of their formation. The study of faint lines in dwarf stars has made it possible to obtain reliable information on the early evolutionary phase of the Galaxy (for a review, see Spite et al. 1985).
High Signal to Noise Analysis of the Chemical Composition of Stars in the Magellanic Clouds
Authors: Spite M. , Spite F. , François P.
Published: July 2016

A few high S/N spectra of F-G supergiants in the field of the Magellanic Clouds, and a spectrum of a star in the in the young SMC cluster NGC330 have been obtained at the échelle spectrograph of the 3.6m telescope of ESO (CASPEC). Preliminary results of the analysis of these stars and their consequences in the evolution of the clouds are presented here.
Final Remarks on IAU Symposium 132
Authors: Furenlid I.
Published: July 2016

FURENLID Without breaking the orderly progression of events during these last moments of IAU Symposium No. 132, I would like to insert a few words. We have just finished an excellent Symposium, and at this point there is no more any discussion or arguments when we all join in gratitude to the supporting staff at the meeting as well as to the scientific and local organizing committees. The Symposium has for me been like a school, where I have found myself -except for 11 too short minutes- on the appropriate side of the teacher's desk, the student side. The teachers were outstanding! Our special thanks go to the Principal of this school, Dr. Giusa Cayrel, and as a small token of gratitude I would like to present her with a copy of the solar flux atlas. Dr. Cayrel, you are dear to us and we thank you very much!
The Future of the Researches About the Earth's Rotation
Authors: Vicente R. O.
Published: July 2016

It is well known that futurology, the science of forecasting the future, is a very difficult science. It also depends on the intervals of time for which we pretend to forecast the evolution of the physical system under consideration. Aldous Huxley thought that futurology might be a very good thing.
Basic Problems in the Kinematics of the Rotation of the Earth
Authors: Guinot Bernard
Published: July 2016

With the advent of more precise methods for measuring Earth rotation, a number of corrections to the apparent directions in space, to the terrestrial references, and to the rotation axis motion have to be carefully applied. It is the duty of the international Astronomical Union to give recommended or conventional expressions of these corrections in order to avoid inextricable difficulties in discussing the evaluated results. However, this task is not sufficient. The concepts used in the description of the Earth's rotation are somewhat obscured by traditions. They should be purified by removing notions which are not directly relevant.
Etude d'Observations Effectuees a l'Astrolabe de Paris et Comparaison avec d'Autres Resultats Concernant les Termes Principaux de la Nutation
Authors: Débarbat Suzanne
Published: July 2016

Chollet has analysed a homogeneous series of astrolabe observations made at Paris since 1956.5 in order to derive corrections to the principal terms of nutation. Comparison of his results with others obtained recently indicates that the values and would be suitable for adoption.
A New System of the U.S.S.R. Standard Time for 1955–1974 and its Application in the Study of the Earth's Rotation
Authors: Gubanov V. S. , Yagudin L. I.
Published: July 2016

For the study of the Earth's rotation and geodetic measurements the longest possible series of homogeneous Universal Time (UT) data is required. For various reasons this remains a difficult problem. Periodically it is necessary to revise past observations and redetermine the UT scale. This was done by the Bureau International de l'Heure (BIH) in 1968 when the FK 4 catalog, revised values of astronomical longitudes, and new techniques were standardized for the reduction of astronomical observations. This system known as the 1968 BIH System has been in use since 1968 and has also been used for the re-reduction of observations back to 1962.0.
On the Computation of Accurate Earth Rotation by the Classical Astronomical Method
Authors: Feissel Martine
Published: July 2016

Improved series of Universal Time and latitude measurements back to 1962 have been provided to the BIH by several observatories recently. New techniques are currently or will soon provide Earth rotation data that are independent from the classical astronomical observations. In the meantime, the BIH has acquired experience on possible methods for achieving better accuracy. These reasons make it worthwhile to apply our present practical knowledge to the past data. The method which will be used for computing Earth rotation data from the updated BIH files is presented.
Secular Variation of Tashkent Astronomical Latitude
Authors: Shcheglov V. P. , Kaganovsky G. M.
Published: July 2016

The mean astronomical latitude of the Tashkent Observatory was determined by D. D. Gedeonov in 1895–1896 before the International Latitude Service had been organized. The determination was based on a continuous fourteen-month series of observations with a Wanschaff visual zenith telescope (d = 68 mm., f = 870 mm.). These data consisted of the observations of 2214 Talcott pairs which were observed from July, 1895 through August, 1896.
The Ephemeris Reference Frame for Astrometry
Authors: Murray C.A.
Published: July 2016

The basic problem of fundamental astrometry is to relate the instrumental reference frame of an observer to the frame defined by ephemerides of stars and objects in the Solar System. It is shown that in principle the choice of definition of the Ephemeris Reference Frame (ERF) can be quite arbitrary. For convenience, it is argued that the ERF should be defined by the rotation of an axi-symmetric rigid model Earth, the celestial pole being the direction of the axis of figure. This definition has practical and theoretical advantages over a model-dependent definition which attempts to take account of non-rigidity of the actual Earth.
An Introduction to Radio Interferometric Techniques
Authors: Elsmore B.
Published: July 2016

At this symposium we are to hear a great deal about new techniques for the measurement of earth rotation and polar motion that have come into being in the last decade and I am privileged to give a short introduction to one of these new techniques, that of radio interferometry.
An Improved Polar Motion and Earth Rotation Monitoring Service Using Radio Interferometry
Authors: Carter William E. , Robertson Douglas S. , Abell Michael D.
Published: July 2016

The National Geodetic Survey (NGS) of the National Ocean Survey (NOS), a component of the National Oceanic and Atmospheric Administration has begun a project to establish and operate a 3-station network of permanent observatories to monitor polar-motion and Earth rotation (UT1) by radio interferometric observations of quasars. The project designation is POLARIS (POLar-motion Analysis by Radio Interferometric Surveying).

The POLARIS observatories will be equipped with a new generation of instrumentation and software, the Mark III data acquisition and processing system currently under development by a multi-organizational team.
On the Fluctuations in the Solar Flux at cm-Wavelengths Monitored on Small Areas of the Sun's Disk
Authors: Hirth W.
Published: July 2016

We discuss the relatively broad spectrum of fluctuations in flux which is observed at cm-wavelengths when tracking a small area on the Sun's disk. The distribution of power P over the frequencies ω of fluctuations can be approximated by a power-law

where α ≃ 2; often a continuous “curvature” is superimposed and a “turnover” frequency is indicated at about ω/2π ≃ 10−3 Hz. Considering the phases of different Fourier components of the time series measured, a significant linear correlation is found between phases of neighbouring frequencies.
On the Origin of Microwave Emission from Sunspots
Authors: Pallavicini R.
Published: July 2016

Coordinated high-resolution XUV and centimetric observations of active regions obtained from Skylab and Stanford are compared with the aim of determining the nature of the centimetric radiation. It is concluded that the thermal gyroresonance process is the most likely emission mechanism for the bright compact radio sources associated with sunspots.
The Spatial Structure of Solar Microwave Bursts
Authors: Marsh K. A. , Hurford G. J. , Zirin H.
Published: July 2016

Observations of five impulsive microwave bursts were made during July 15–18, 1978 using the VLA at 4.9 GHz with temporal and spatial resolutions of 10 s and up to 1″ respectively. A series of 2-dimensional snapshot synthesis maps was made as a function of time, and compared with Hα photographs and magnetograms. Each flare was characterized by a single source of constant size, located on the magnetic neutral line between the Hα kernels.
Solar Type I Radio Bursts: An Ion-Acoustic Wave Model
Authors: Benz A. O. , Wentzel D. G.
Published: July 2016

(paper submitted to Astronomy and Astrophysics)

We propose a model for type I emission based on scattering of Langmuir waves by ion acoustic waves, which are associated with the evolution of the associated active region on the Sun.
Fine Structure in Solar Type III Radio Bursts Spectra
Authors: Perrenoud M. R. , Treumann A. R.
Published: July 2016

The new digitalized polarispectrometer IKARUS (Perrenoud, 1979) at ETH, Zürich gave the possibility for a more detailed investigation of the solar type III spectral evolution.
Pecularities of the Dynamic Spectra of Type V Solar Radio Bursts
Authors: Bakunin L. M. , Markeev A. K. , Fomichev V. V. , Chertok I. M.
Published: July 2016

The data on type V solar radio bursts obtained at IZMIRAN with the 45-90 MHz radiospectrograph are analyzed. A great variety and complexity in the dynamic spectra of these events is found. A number of categories of bursts with different emission characteristics of the leading and following edges are distinguished. A number of types of fine structure were found in the dynamic spectra of many bursts. Type V bursts, for which the radio emission at the fundamental and the second harmonic is clearly observed are analyzed.
An Observed Correlation Between the Flux Densities of Extended Hard X-ray and Microwave Solar Bursts
Authors: Stewart R. T. , Nelson G. J.
Published: July 2016

Crannell et al. (1978) have reported an observed correlation between the time profiles and flux densities of impulsive hard x-ray and microwave solar bursts. We report here on a significant correlation between the fluxes of extended bursts of hard x-rays and microwaves. The significance of our observations follows from the suggestion of Wild, Smerd and Weiss (1963) that the extended bursts are evidence for a second phase acceleration process in the corona. We show that the observed characteristics of these extended microwave bursts (viz. rather a flat spectrum below a turnover frequency which is independent of intensity) can be explained by gyrosynchrotron radiation from the same population of energetic (E ~ 100 keV) electrons as those emitting thin-target x-ray bremsstrahlung.
On the Propagation of the Electrons Related to Type III Bursts
Authors: de Genouillac G.V. , Escande D.F.
Published: July 2016

Type III solar radio bursts are known to be excited by solar electron clouds travelling outwards through the solar corona and interplanetary medium. According to the “plasma hypothesis”, electron plasma oscillations are created by the passing beam, which are in turn converted into electromagnetic waves.
Plasma Oscillations and the Emissivity of Type III Radio Bursts
Authors: Gurnett D. A. , Anderson R. R. , Tokar R. L.
Published: July 2016

Plasma wave electric field measurements with the solar orbiting Helios spacecraft have shown that intense electron plasma oscillations occur in association with type III solar radio bursts, thereby confirming a well known mechanism for generating solar radio emissions first proposed by Ginzburg and Zheleznyakov in 1958. In this paper we review the principal characteristics of these plasma oscillations and compare the observed plasma oscillation intensities with recent measurements of the emissivity of type III radio bursts. The observed emissivities are shown to be in good agreement with two current models for the conversion of electrostatic plasma oscillations to electromagnetic radiation.
Observations of the Structure of Type IIIb Radio Bursts
Authors: Sastry Ch. V. , Subrahmanyan K. R. , Krishnan V.
Published: July 2016

We observed short duration, narrow band Type IIIb radio bursts that occur just before the onset of a normal Type III burst. These observations were made with a multichannel radiometer with a center frequency of 25 MHz, time constant of 10 milliseconds and frequency resolution of 100 KHz. The average half power duration of a typical element of a Type III burst was determined. It was found to be very similar to the time profile of a normal Type III burst, i.e., sharp rise and exponential type decay. The duration of the exciter, tE, and the decay time constant, τ, determined from the average time profile were 0.88 and 0.31 seconds, respectively. The corresponding quantities for the associated Type III bursts are 6.0 and 2.1 seconds, respectively. It is interesting to note that the ratios

are the same, and equal to 0.98. We found that there is no difference between the time profile of a Type III burst associated with a Type IIIb burst and that of an isolated Type III burst. We also found that the two quantities ‘tE’ and ‘ τ ’ are positively correlated in the case of isolated Type III bursts. The linear correlation coefficient is 0.70. This correlation seems to break down in the case of Type III bursts associated with Type IIIb bursts. We looked for a relation between durations of the elements of the Type IIIb bursts and that of the associated Type III bursts, and found that the two quantities are positively correlated. Lastly, we would like to point out that the elements of Type IIIb bursts observed by us are more intense than the associated Type III burst.
A Study of Be Star Variability
Authors: Dachs Joachim
Published: July 2016

Variations of Balmer emission line strength for Be stars are compared to simultaneously measured photometric light-curves in the visual and infrared regions of the spectrum. Three different types of correlations between photometric and spectrometric variations are described. Variable intensity of continuous recombination radiation from ionized hydrogen in the circumstellar envelope is shown to be a major source of light variations for Be stars.
Luminosity Classification of Be Stars by Balmer Line Narrow Band Photometry
Authors: Zeuge Wolfgang
Published: July 2016

The absolute luminosity of most Be stars can be determined by using Balmer line narrow band photometry with an accuracy of about 0.4 mag. The few cases in which this method fails can be detected.
Correlations Between BCD Parameters of the Continuous Spectrum and the Balmer Decrement of Be Stars
Authors: Divan L. , Zorec J. , Briot D.
Published: July 2016

One of the greatest difficulties in interpreting the continuous spectrum of Be stars is to separate the effects of interstellar reddening from the effects due to the presence of the envelope. This difficulty has been avoided in the two types of correlations considered here. In the first one, parameters not affected by interstellar reddening are used (the Balmer jump and the Balmer decrement). In the second one, the parameters used can be affected by the interstellar extinction but comparisons are made only between values which correspond to the same (but variable) Be star, at different epochs, with different amounts of emission.
Observation de la Raie Hα dans les Etoiles Be
Authors: Andrillat Y. , Fehrenbach Ch.
Published: July 2016

Few studies concern the H alpha profile of the Be stars and it is difficult to do a fine analysis of the line structure, and of its variations from the results obtained with different resolutions and accuracies.

Then, it was useful to apply modern technics for the observation of this line to get an homogeneous material, sensitive enough to show fast variations of the order of few minutes because an accurate photometry is available using linear response receivers.
Recent Changes of the Be Star HD 58050
Authors: Hubert-Delplace A.M. , Hubert H. , Ballereau D. , Chambon M. Th.
Published: July 2016

Emission line variations in 1961–1981 of the B2 star HD58050 are reported. Brightness variations are recalled. An estimation of the veiling effect given by continous emission of the envelope, observed in November 1980 in the Balmer lines, is given.
Infrared Emission from Four be Stars Optical Counterparts of Galactic X-Ray Sources
Authors: Persi P. , Ferrari-Toniolo M. , Grasdalen G.L.
Published: July 2016

Preliminary results of our infrared observations from 2.3 up to 10 and 20 microns of the Be-X-ray stars X Per, γ Cas and HDE 245770, indicate the presence of an ionized circumstellar disk with an electron density law of the type ne ∝ r−3.5. x Per and γ Cas show besides, variable infrared excess at 10μ suggesting variability in the stellar wind. LS I+65°010 presents an anomalous infrared energy distribution for a Be star.
The Expanding Atmosphere of HD 218393
Authors: Paterson-Beeckmans F. , Hubert-Delplace A.M. , Hubert H. , Ballereau D.
Published: July 2016

Visible and far ultraviolet high resolution spectra of the B2 binary star HD 218393 have been obtained at one day interval, shortly before the phase of maximum outwards velocity, adopting the period of 38.908 days. Both spectra show the existence of an extended atmosphere, accelerated outwards. The SiIV resonance lines show some indication of mass loss. With only one set of observations, the origin of the strong and wide (about 130 km/s FWHM) ultraviolet absorption lines of once ionized elements is difficult to determine.
The Spectrum of HD 51585 in the Blue and in the Ultraviolet
Authors: Houziaux L. , Andrillat Y. , Heck A. , Nandy K.
Published: July 2016

New visible and ultraviolet spectra of the peculiar emission line star HD 51585 are described. Interstellar lines and the λ 2200 feature are rather weak. A colour excess E(B-V) = 0.33 is derived. The extinction curve resembles the one obtained from LMC stars.
Simultaneous IUE Ground-Based Spectroscopic Observations of the Variable LMC Star R 71
Authors: Wolf B. , Appenzeller I. , Stahl O.
Published: July 2016

Using the IUE satellite we obtained high resolution UV spectrograms (1200 < λ < 3200 Å) of the S Dor type variable R 71 in the LMC. The IUE observations were supplemented by coordinated groundbased high dispersion spectroscopy and by photometric observations. From these observations we derive for the minimum state of R 71 the following stellar parameters: L = 2.0 × 105 L⊙, R ≈ 81 R⊙, Teff ≈ 13 600 K. For the expanding envelope we find a surprisingly low temperature of only about 6000 K and an apparently decelerated velocity field with a maximum outflow velocity of ~ 127 km s−1. The minimum state mass loss rate is in the order of 3 × 10−7 M⊙ y−1. Our results support the suggestion that the visual light variations of the S Dor type variables are produced by strong density variations of the expanding envelopes of these objects. A detailed study is forthcoming in Astronomy & Astrophysics.
Model Atmospheres of Be Stars
Authors: Poeckert Roland
Published: July 2016

The basic concept of what a Be star is we owe to Struve (1931). His proposal that these stars are rapidly rotating and have an extended, disc-like, circumstellar envelope is still the basis for all models of Be stars. Unfortunately, progress in understanding the dynamics of Be stars has been painfully slow, a consequence of the very complex nature of the problem. As yet there does not exist a self-consistent unique model of any Be star.
The Continuing Saga of the Be Stars: A Summary
Authors: Snow Theodore P.
Published: July 2016

This paper, written in summary of IAU Symposium 98 on the Be Stars, contains an outline of the proceedings, organized according to physical parameters of the stars, the circumstellar environment, models explaining the data, and a summary of the outstanding problems. Suggested future observations and needed theoretical work are described.
Globular Cluster Luminosity Functions
Authors: Demarque Pierre
Published: July 2016

The use of luminosity functions in the following areas is reviewed: (a) the determination of the helium content and ages of the globular clusters; (b) the testing of stellar structure theory; and (c) the determination of the initial mass function of globular clusters.
Dwarf Spheroidal Galaxies and Globular Clusters
Authors: Da Costa G. S.
Published: July 2016

Recent observational results for dwarf spheroidal galaxies are reviewed and discussed. In particular, the differences in stellar populations between dwarf spheroidal galaxies and globular clusters are highlighted. It seems most probable that the origin and evolution of dwarf spheroidal galaxies was very different from that of globular clusters.
Galaxy Formation and Cluster Formation
Authors: Larson Richard B.
Published: July 2016

A primary motivation for studying globular clusters is that, as the oldest known galactic fossils, they trace the earliest stages of galactic evolution; indeed, they may hold the key to understanding galaxy formation. Thus it is clearly of great importance to learn how to read the fossil record. To do this, we need to understand something about how the globular clusters themselves formed. Were they the first bound objects to form, or did they form in larger pre-existing systems of which they are just small surviving fragments? If the latter, what were the prehistoric cluster-forming systems like? And how did they manage to produce objects like globular clusters?
Disolution of Star Clusters in Galaxies
Authors: Wielen Roland
Published: July 2016

We present a procedure which allows to predict the dissolution times of star clusters in a simple way. The dissolution time of a cluster depends mainly on its total mass, its median radius and its galactic environment (galactic tidal field and passing massive objects). As an example, we discuss the lifetimes of LMC clusters. Finally, we show that massive black holes, which have been proposed as the major constituent of the dark coronae of galaxies, are very effective in destroying globular clusters.
Harlow Shapley: A View from the Harvard Archives
Authors: Welther Barbara L.
Published: July 2016

This exhibit featured facsimiles of some letters that Shapley exchanged with George Ellery Hale, Henry Norris Russell, and Heber Doust Curtis from 1917 when he was at Mount Wilson working on globular clusters to 1921 when he became Director of Harvard College Observatory.
New Main-Sequence Luminosity Functions for Globular Clusters
Authors: McClure Robert D. , Stetson Peter B. , Hesser James E. , Smith Graham H. , Harris William E. , VandenBerg Don A.
Published: July 2016

We report new results from a program which is aimed at obtaining deep CCD photometry for a sample of relatively nearby globular clusters having a wide range of metallicities. The CCD cameras on the CFHT 3.6 m, CTIO 4 m and KPNO 4 m telescopes have been used over the past 4 years to obtain deep exposures in regions of a number of clusters. In order to avoid the severest crowding, all of our observations have been obtained at distances of greater than ~ 5 core radii from the cluster centers. The images have been analysed by using the DAOPHOT point-spread-function fitting routines.
Global Versus Local Mass Functions
Authors: King Ivan R.
Published: July 2016

Multimass dynamical models are used to study the difference between a mass function determined in an outer field and the global mass function of the cluster. The differences are small.
Spectra of BHB Stars in M 3, M 13 and M 92
Authors: Davis Philip A. G. , Samus N. N.
Published: July 2016

Spectra, at a dispersion of ~ 50 å per millimeter, have been obtained of BHB stars in the globular clusters M 3, M 13 and M 92 with the TV scanner on the Soviet Union's Six Meter Telescope. The spectra cover a range of 700 ångstroms in 500 channels in which counts were made of the intensity of the stellar spectrum. At this dispersion the hydrogen Balmer lines (γ, δ, ε, H8 - H12) can be seen as well as the Ca II line at λ = 3934.
Absolute Proper Motions and Space Velocities of Globular Clusters
Authors: Tucholke H. -J. , Brosche P. , Geffert M.
Published: July 2016

Proper motions of globular clusters referred to extragalactic background objects provide absolute proper motions leading to space velocities. Some results from the Bonn Observatory proper motion program for galactic globular clusters are shown. Reference stars from the Lick program linked to galaxies are used. Low orbital angular momenta for NGC 4147, NGC 5466 and NGC 6218 were detected. In a further program, proper motions of 47 Tuc and NGC 362 are currently being measured relative to the background of the SMC.
Astronomical Catalogues in the M 31 Region
Authors: Battistini P.
Published: July 2016

In the course of work done in the Astronomy Department of Bologna University on “Search and Study of Globular Clusters in M 31”, a remarkable quantity of data in the literature concerning optical, X-ray and radio surveys in the field of Andromeda Galaxy has been accumulated.
Formation of Populous Clusters from Metal-Poor Gas in the Magellanic Clouds
Authors: Richtler T. , Seggewiss W.
Published: July 2016

We present the results of low dispersion spectrophotometry (resolution about 5 å, using IDS at ESO 3.6 m and 1.5 m telescopes) of 80 red supergiants in the Magellanic Clouds: 31 SMC field stars, 26 LMC field stars and 23 suspected members of young populous clusters. From these spectra, spectrophotometric indices have been derived which simulate Strömgren photometry and measure the strengths of the Ca I (4226) line and of the G-band. The indices are calibrated with respect to red giants and provide a set of metallicity indicators.
Observed Variations in the Density Profiles of Star Clusters in the LMC
Authors: Kontizas M. , Hatzidimitriou D. , Metaxa M.
Published: July 2016

Several dynamical theories have been developed in order to approach the dynamical evolution of stellar systems and explain the observational data. The observed density profiles of the clusters can be a valuable source of information towards the understanding of their dynamical properties. King in a series of papers has connected the established theories with the observed profiles in clusters of our own Galaxy (King, 1962, 1966; etc.). Density profiles can be obtained by means of star counts and/or by means of photometric photometry. So far the observations for clusters in our Galaxy and the MCs appear to fit well the so called King models and provide information of their tidal radii, total masses and concentration parameters (Kontizas, 1984).
Ratio of Early to Late Type Stars in SMC Clusters
Authors: Kontizas E. , Kontizas M. , Dapergolas A. , Hatzidmitriou D.
Published: July 2016

Spectral classification of stars in SMC clusters provide useful information on the evolutionary history of this galaxy and permit us to test the theory of stellar evolution.
The SMC Cluster Lindsay 11
Authors: Buttress J. , Cannon R. D. , Griffiths W. K.
Published: July 2016

This small cluster is situated in the western region of the SMC at α = 0h 26m 13s, ε = −73°, 1′, 20″ (1950) and has been chosen for study in the initial post-launch period of the Hubble Space Telescope. This preliminary study was made using data obtained using a CCD camera on the SAAO 1 m telescope in October 1984.