bluuebunny/crossref_metadata_2025 huggingface dataset:
Characteristics of Nebulosity Associated with Parkes Quasars
Authors: Wehinger P. A. , Wyckoff S. , Gehren T.
Published: July 2016

A sample of 13 out of 15 low redshift (0.1 ≤ z ≤ 0.6) radio-loud quasars have been resolved on large-scale (19 arcsec mm−1), sky-limited (µR ∼ 26.5 mag sec−2) Kodak IIIa-F photographs obtained with the ESO 3.6-m telescope. The QSO images were analyzed by digitally subtracting the plate background and the point-spread function defined by images of nearby (≤ 1 arcmin) field stars having magnitudes comparable to the quasars (Δm ≲ 0.3 mag). The resolved nebulosities underlying the QSO images have isophotal diameters in the range θ ∼ 7 to 40 arcsec, with surface brightnesses µR ∼ 22–26 mag sec−2, and integrated apparent red magnitudes ∼ 16–21.
The Evolution of Linear Sizes
Authors: Kapahi V. K. , Subrahmanya C. R.
Published: July 2016

Possible evidence that the linear sizes of extragalactic radio sources were smaller at earlier epochs was first provided by the angular size redshift (θ-z) relation for double radio quasars (Legg 1970, Miley 1971, Wardle and Miley 1974). But because of the strong correlation between redshift (z) and radio luminosity (P) in flux limited radio samples, it is hard to decide if the observed decrease in sizes with z is caused by an epoch dependence of linear sizes (ℓ) or by an inverse correlation between P and ℓ. Several authors (eg. Stannard and Neal 1977, Wardle and Potash 1977, Hooley ET AL. 1978, Wills 1979, Masson 1980) have attempted to separate the two effects by comparing the properties of quasars from the 3CR survey with those from the 4C and Parkes samples. Although most of these studies appear to marginally favour a P-ℓ correlation, none of them can rule out even a fairly strong evolution in ℓ with z. Apart from the small numbers involved, the difficulty is that 3C and 4C quasars do not differ a great deal in their redshifts or luminosities. A complete sample of quasars at much weaker flux levels would be quite valuable in this regard.
The Optical and Infrared Properties of 3CR Radio Galaxies
Authors: Lilly S. J. , Longair M. S.
Published: July 2016

For the last 20 years, a huge observational effort has been devoted to the identification of all 3CR radio sources lying in directions away from the Galactic plane. The project is now more-or-less complete thanks to high-resolution radio observations with aperture synthesis radio telescopes, in particular the Cambridge 5-km telescope, and the use of a CCD camera on the Palomar 5-metre telescope (see e.g. Gunn et al 1980).
Radio Evolution in High Redshift Clusters
Authors: Jaffe Walter
Published: July 2016

In this project we try to follow the evolution of the Radio Luminosity Function (RLF) with redshift by observing a set of galaxy clusters with known spectroscopic redshifts. This method has the advantage over previous studies, based on general radio surveys, that most of the redshifts are accurately known, that intrinsically weaker sources are well represented, and that the parent sample of galaxies is well defined. The chief disadvantages are that, because the sample is optically selected, there are few high luminosity radio sources, and that we cannot examine differences between cluster and field populations.
Line Strengths in WN Stars
Authors: Myckky Leep E.
Published: July 2016

We have analyzed high-dispersion spectra of over 100 WN stars in the Galaxy and the Large Magellenic Cloud (LMC). Most of the spectra were obtained through 4-m telescopes (Conti, Leep, and Perry 1981). The measured strengths of the WN classification lines N III λλ4634-41, N IV λ4057, N V λ4604 (Smith 1968) for stars of WN subtypes 2.5–8 are shown in Figure 1. The assignments of WN subtypes are based on visual estimates of ratios of line strengths according to the scheme of Smith (1968), except that stars appearing to be earlier than WN3 are classified as WN2 or WN2.5 as explained by vander Hucht et al. (1981) and by Conti, Leep and Perry (1981).
Radio Observations of HD 193793
Authors: Florkowski David R.
Published: July 2016

Radio observations of the Wolf-Rayet star HD 19 3793 are presented. Most of the observations were made during a large outburst in the infrared. The radio observations are consistent with the suggestion that a circumstellar dust shell recently formed.
The C/N Ratio in WN and WC Stars
Authors: Smith Linda J. , Willis Allan J.
Published: July 2016

We present new determinations of the C/He, N/He and C/N ratios in 6 WN and 4 WC stars, resulting from a Sobolev analysis of new IUE UV line measurements in these species. Through improved observations of more stars, the present work extends an earlier, UV-based, study carried out by Willis & Wilson (1978, WW), which gives details of the Escape Probability Modelling (EPM) utilised. Full details of the current IUE observations, measurements and modelling will appear in Monthly Notices: here we summarise the results. Table 1 lists the ten WR stars currently studied — all were observed at low resolution and the brightest eight at high resolution.
IR Spectroscopy of WN Stars
Authors: Hillier J.D.
Published: July 2016

The combination of IR data with radio, optical and UV observations has the potential to greatly increase our understanding of the WR phenomena. Consequently we are obtaining IR spectra from 1.1 to 4.2µ for a sample of southern WN stars (K < 7th magnitude) using a low resolution, R∼100, circular variable filter wheel (CVF) and a cooled grating spectrometer, (CGS) (Jones et al. 1981) with a maximum resolution of 2000. Previous IR spectral studies of WR stars have generally concentrated on line identification, and beyond 1.7µ they have been limited to low resolution (Barnes et al. 1974, Cohen et al. 1978, Williams et al. 1980). With the CGS it is now possible to obtain spectra at resolutions sufficiently high to split blends and reveal details of line profiles. Below we present preliminary results of our observations.
Near Infrared Observations of Galactic WN Stars
Authors: Vreux J.M. , Dennefeld M. , Andrillat Y.
Published: July 2016

The observations reported here have been obtained with the ESO Reticon system attached to the Boller and Chivens spectrograph at the 3.6 m telescope. The reciprocal dispersion was 228 A mm−1 with a useful spectral range extending from 5800 A to 11000 A. The slit was 200 µm wide which corresponds to 1.4 arcsec on the sky and to about 33.5 µm(∼ 7.6 A) in the plane of the detector. Sky substraction was performed by means of observations at 93 arcsec. East and West of the object. The correction for atmospheric extinction was based on a mean extinction curve of La Silla (Tug, 1977). As a consequence the strongest atmospheric bands are still present on the final spectra. The data were also corrected for the instrument sensitivity response by using calibrated stars selected from Breger's catalog (1976). As these reference data are from filter photometry, they are not well suited to the resolution of our spectra, at least in some regions. This problem can be significant, as clearly illustrated by Johnson (1980).
Observations of New Wolf-Rayet Binaries
Authors: Niemel Virpi S.
Published: July 2016

At present we know that the Wolf-Rayet stars do not form a homogeneous group of objects with similar masses, but that their masses span a considerable range. Whether or not there is a correlation between the masses and the different subtypes of WR stars, can only be answered by more observations of WR stars in binarysystems yielding estimates of the masses of their components.
The on Stars: A Wider Spectroscopic Definition
Authors: Bisiacchi G.F. , López J. , Firmani C.
Published: July 2016

During the last years, many authors have recognized the existence of some OB stars that show the nitrogen absorption lines enhanced (Walborn 1970, 1971; Conti 1973; Jashek and Jashek 1974).
The Peculiar Binary System HD 45166 (SdO+B8V?)
Authors: Willis Allan J. , Stickland David J.
Published: July 2016

Although clearly a peculiar object (Anger 1933), HD 45166 has been the subject of remarkably few published optical studies. Heap & Aller (1978, HA) discuss its optical spectrum and give evidence that the object is a binary system comprising a B8v star and a hotter WR-like object, denoted qWR by van Blerkom (1978). This paper presents the first UV observations of the system obtained with IUE at the epochs listed in Table 1. These new data show drastic line (but not apparently continuum) variations with epoch, which cast doubt on the WR-connection, although herein we still adopt the notation “qWR”.
Ring Nebulae Around WC6 Stars: NGC 6357 Around HD 157 504
Authors: Lortet M.C. , Testor G. , Niemela V.
Published: July 2016

Three cases of ring nebulae around a WC6 star are definitely known : one is around HD 92809 north of the Carina Nebula (Lortet et al. 1980), another around θ Mus has been studied by Heckathorn et al (1982). We here study the third one, NGC 6357 around HD 157504, first quoted in the survey by Heckathorn et al (1981 and 1982).
Kinematics of the Ring-Shaped Nebula N206 in the LMC
Authors: Rosado M. , Monnet G. , Laval A. , Georgelin Y.
Published: July 2016

Preliminary results on the radial velocity field of the ring-shaped nebula N206 in the LMC are given. Several early type stars are located inside this nebula one of them being a WC5-6 star. A discussion about the kinematics of the gas around the WR star is also given.
IUE Observations of the WN-C Star HD 62910
Authors: Stickland David J. , Willis Allan J.
Published: July 2016

We have obtained low resolution UV spectrophotometry of the WN-C star HD 62910 in both the SWP (λλ1150–2000) and LWR (λλ1850–3250) IUE spectrographs, and also for HD 117688, WN6, used for comparison. The UV spectrum of HD 62910 is shown in Fig 1 and is seen to be dominated by many strong emission lines, which by comparison with the IUE spectra of other galactic WR stars (Nussbaumer et al. 1981) is found to reflect a predominantly WN-type spectrum, but in addition, weaker features characteristic of WC spectra are also seen, particularly in the LWR wavelength range. In Table 1 we list the principal observed WN and WC features in HD 62910. A comparison of the relative strengths of the WN emissions with those observed in various WN subtypes (Nussbaumer et al. 1981) and with our spectra of HD 117688 confirms the subtype of HD 62910 as WN6 as inferred in the visible (Smith 1968, Van der Hucht et al. 1981).
Observations and the Wolf-Rayet Evolutionary Scenario
Authors: Firmani Claudio
Published: July 2016

Results of a statistical analysis of massive stars and of WR stars show general agreement with the scenario that identifies the majority of the WR stars with the He-burning evolutionary phases. The duplicity, the morphological properties and the galactic distribution of the WR stars are valuable pieces of evidence that suggest correlations between the different WR types and the “channels” defined in the scenario. A rough analysis of the “traffic through each channel” is attempted.
The First Detection of Wolf-Rayet Stars in M31
Authors: Shara Michael M. , Moffat Anthony F. J.
Published: July 2016

A search to continuum magnitude B ∼ 21.5 (MB∼ −3) using a narrow band filter at λ4670å and a wide B-band filter has revealed 21 Wolf-Rayet star candidates in about half the giant Sb galaxy M31. Some weak-line WR stars, particularly WN subtypes, may have escaped detection. These numbers are compatible with the total number of luminous (i.e. massive) stars in M31. Eighteen of twenty confirmed candidate stars in M31 lie in the direction of 0B associations in the ring of prominent star formation 5–16 kpc from the center.
Wolf-Rayet Stars in Open Clusters and Associations
Authors: Lundström Ingemar , Stenholm Björn
Published: July 2016

We have made a search for line-of-sight coincidences between WR stars and open clusters using the new catalogue of galactic WR stars (van der Hucht et al., 1981, called the HCLS catalogue) and the catalogue of open cluster data (Lyngå and Lundström, 1980). As a measure of the separation we used the angular distance between the WR star and the cluster centre expressed with the cluster angular radius, r', as unit.
The Wolf-Rayet Stars in 30 Doradus
Authors: Melnick Jorge
Published: July 2016

Giant HII regions as sites of massive star formation.

Giant HII regions are the brightest extragalactic emission line objects that can be studied in detail. With diameters of several hundreds of parsecs, these nebulae can be easily resolved out to distances of a few Mpc. Typically 100 or more 0 stars are required to account for the observed ionization of the nebular gas and this implies that the cores of giant HII regions contain populous young star clusters. The stars in these clusters have essentially the same age and chemical composition. Thus, giant HII region cores provide excellent sites where theories of the formation and evolution of massive stars and, in particular, of Wolf-Rayet (WR) stars can be tested.
Spectra of the Wolf-Rayet Stars in 30 Doradus
Authors: Conti Peter S.
Published: July 2016

The central cluster of the 30 Doradus complex in the Large Magellanic Cloud (LMC) contains at least a dozen Wolf-Rayet (W-R) stars of the nitrogen sequence according to Melnick (1978). In addition to the six stars previously identified by Feast, Thackeray and Wesselinck (1960), Melnick identified an additional six using an Echele spectrograph on the 1.52 m telescope at La Silla. I have obtained high resolution spectra of ten of these stars and would like to discuss the spectral types.
The Impact of Array Detectors on High Resolution Infrared Spectroscopy
Authors: Ridgway Stephen T. , Hinkle Kenneth H.
Published: July 2016

Infrared detector arrays implemented for astronomical use during the past few years achieve performance gains which have profound implications for infrared spectroscopy. Arrays are now available with ∼ few × 103 pixels, each of which is ∼ 102 times more sensitive than previous single element detectors. Depending on the spectral regime, it is now possible to construct infrared spectrometers with limiting sensitivities 10–500 times fainter than in current use.
Rotation of Pre-Main Sequence Stars from High S/N Spectroscopy
Authors: Bouvier J.
Published: July 2016

Until 1980, only a handful of low-mass, active pre-main sequence (pms) stars had known rotation velocities (vsini) /1/. Since then, increasingly sensitive detectors coupled to large telescopes led to high–resolution (a few 104) spectroscopic studies of these faint stars (mv = 10–13), with S/N ratio of the order of 100. The measurement of vsini for large samples of pms stars that resulted brought new insights on various pressing questions related to stellar formation and early stellar evolution : how do the rotation rates of pms stars compare with those expected from models of stellar formation ? how does the stellar angular momentum change during pms evolution ? is pms activity linked with rotation as would be expected if activity were triggered by magnetic processes ?
Shock Phenomena in β Cephei Stars
Authors: Crowe Richard , Gillet Denis
Published: July 2016

In this paper, we present new observations of β Cephei stars made with the CFHT coudé Reticon. Spectral sequences of the extreme star BW Vulpeculae show large velocity and line profile changes in Ha and in the C II doublet (λλ6578,6582) over 0.04 of a cycle, during three different cycles on three different nights. In fact, there are two such phases of line doubling where the velocities are nearly discontinuous before and after the so-called velocity “stillstand” (near maximum light). Also, the line doubling phases coincide with pronounced peaks in the Ha core residual intensity. The most straightforward interpretation of these observations is that there are two shock waves, separated by about 50 minutes, which generate double absorption components. For v Eridani and γ Pegasi, there are no discernible changes in the Ha profiles, despite rather regular velocity variations. This argues against the shock-wave interpretation for “classical” β Cephei stars.
Nonradial Pulsations and the Be Phenomenon
Authors: Baade Dietrich
Published: July 2016

Following a summary of the observations which suggest that the outbursts of classical Be stars are caused by nonradial pulsations, properties, implications and requirements of a model based on this notion are evaluated. A preliminary analysis of new observations of μ Cen is presented which for the first time in a Be star reveals two relatively closely spaced non–commensurate periods. Such a result would render implausible speculations that the variability of Be stars is due to corotating surface features.
Doppler Images of Spotted Late-Type Stars
Authors: Vogt Steven S.
Published: July 2016

Doppler imaging is a technique for deriving resolved images of rapidly rotating stars from a detailed analysis of very high signal-to-noise high resolution spectral line profiles. An improved version of this technique is presented, which now uses principles of maximum entropy image reconstruction to invert the line profile information. The effects that noise, finite resolution, and uncertainties in the assumed stellar physics have on the resultant images were explored through various test simulations. The technique is found to be efficient, accurate, and robust at deriving images of certain classes of stars from realistic quality data. Doppler images are presented of two spotted late-type stars, the RS CVn-type star HR 1099, and the FK Com-type star HD 199178. Both stars show surprisingly similar spot distributions. In each case, there is a single large cool spot straddling the pole, and a number of small cool spots at low latitudes. We expect that the small low latitude spots on each star will migrate poleward to join the polar spot, and suspect that the observed long-lived polar spots are the result of the poleward migration and merging of many active region complexes. If true, the poleward migration of starspots suggests that magnetic activity on very rapidly rotating stars is qualitatively different than that seen on our Sun. We suggest that the observed rotational trigger velocity for the appearance of large spots on late-type stars marks the transition from solar-type boundary layer dynamos to distributed dynamos, which occur only in more rapidly rotating stars. The sizes, locations, and migrations of the spots, however, may be more a result of the convective flow patterns than of any dynamo action, since the spots are quite long-lived.
Abundance Signatures of Internal Stellar Structure in F Stars
Authors: Merchant Boesgaard Ann
Published: July 2016

We have determined Li abundances from high resolution, high signal-to-noise spectra near 6700 å of the F dwarfs in several galactic clusters and in the field. The Li-temperature profiles show large Li depletions in the mid–F stars indicating that matter has been circulated (or diffused) downward in the stars. This brings new observational evidence about the details of stellar envelope structure. Li depletions occur in stars with T = 6400–6900 K, with depletions of over an order of magnitude for those with T = 6500–6800 K. The relationship to rotation, galactic Li, and the halo star Li content is discussed.
The Accuracy of High S/N Spectroscopic Measurements
Authors: Duncan Douglas K.
Published: July 2016

A careful intercomparison is made of several sets of high S/N spectrsocopic observations made by different astronomers, using different telescopes and detectors, observing the same objects. Spectra of moderately weak (10-50 mÅ) Li lines, observed at S/N of one to several hundred using the CFHT Reticon, Lick Observatory Reticon, McDonald Observatory Digicon, and the Intermediate Dispersion Spectrograph plus CCD of the Isaac Newton Telescope agree within the claimed measurement accuracies of about 3-6 mÅ almost without exception. CFHT Reticon observations of Hyades dwarfs are compared with unpublished observations taken with a CCD at Lick Observatory; again, the agreement is very good. However, abundance determinations based on these measurements agree less well. The discrepancy arises from different temperatures used by different investigators for the same stars. The accuracy of various methods of temperature determination is examined, including B-V, R-I, and V-K colors, continuum scans, Hα line profile fitting, and temperatures derived from fine analyses. With careful work and good data, temperatures still limit the accuracy of some of the programs discussed.
On Technetium Abundance in Late-type Stars
Authors: Kipper T. A.
Published: July 2016

Technetium abundances in the atmospheres of S- and C-stars are estimated by comparing the synthetic spectra and high dispersion observed spectra for the TcI λ 5924.47 region. It was found that reliable estimates are possible only for the pure S-stars and SC-stars. For the late carbon stars only the upper limit of the Tc abundance can be found. For TX Psc (C6.5) it was found to be lgεTc = 0.5.
Boron Abundance in the PopII HD 76932
Authors: Molaro P.
Published: July 2016

Aware of the importance of B observations in cool stars we have attempted to search for BI 2496 lines in high resolution IUE spectra of HD 76932, with [Fe/H]=−1.1, and HD 216385, with [Fe/H]=−0.6. Line blending and the impossibility of establishing the continuum level are the major obstacles in such an investigation. Molaro (1987) showed that, in the case of extremely metal-deficient stars, the consequent line-blocking reduction allows us to derive significant upper limits for the B abundance. In HD 140283, [Fe/H]=−3.0, Molaro (1987) derived [B/H]< 2 ×10−11. In HD 76932 a preliminary analysis gives a B abundance of [B/H]< 2 ×10−10, i.e. less than the present “cosmic” value. On the other hand no useful limits can be placed for HD 216385. The presence of an unidentified line, not resolved with IUE, prevents B analysis in cool stars with similar or greater metallicity. Better data with higher spectral resolution and greater photometric accuracy are required to confirm these results. The simultaneous presence of Li in the atmospheres of these stars rules out stellar depletion for B, providing evidence that the B abundance in the Galaxy was lower in the past than it is today. These observations also imply that spallation proccesses were not able to produce significant quantities of B, or other light elements at the beginning of the Galaxy. In particular, spallation processes cannot be adduced as a possible source for the Li observed in the Pop II stars.
Oxygen in Halo Giants
Authors: Barbuy B.
Published: July 2016

High resolution CCD spectra were obtained in the region λλ6290-6330 A containing the |OI| λ6300.3 A line for a sample of halo giants. Synthetic spectra were computed to derive their oxygen abundances. A mean value [O/Fe] ≃+0.35 is obtained.
The Chemical Composition of K Dwarfs
Authors: Morell Olof
Published: July 2016

A project with the purpose of determining the chemical composition of a sample of K dwarfs is presented, the project is yet not completed so this is a status report.
Accurate Abundances in Some Giant Stars of the Globular Cluster ω Centauri
Authors: Spite F. , Spite M. , François P.
Published: July 2016

The globular cluster ω Cen is known as a very peculiar cluster : some stars show anomalous abundances. Accurate abundance determinations of various elements have been made in six giants of ω Cen, using spectra with high signal to noise ratios. The results suggest some constraints on the origin of the anomalies, but also show the great complexity of the problem, which requires more observations for approaching a solution. A solution would help to understand the evolution of other objects : globular clusters in the Magellanic Clouds, and dwarf galaxies.
“2-D Frutti” Spectra of B Supergiants in the Milky Way and the LMC
Authors: Fitzpatrick Edward L.
Published: July 2016

Digital spectra of 7 B-type supergiants in the Milky Way and 15 B-type supergiants in the Large Magellanic Cloud (LMC) were obtained in December 1986 using the “2-D Frutti” detector (2-DF) and the Carnegie Image Tube Spectrograph on the 1-m telescope at the Cerro Tololo Inter-American Observatory. The 2-DF is a photon counting, 2-dimensional Shechtman-type detector, now available on both the 1-m and 4-m telescopes at CTIO. The detector/spectrograph configuration used for the December observing run yielded spectra covering the classical blue region, 3800-5000 Å, with a resolution of approximately 3 Å. The typical observing procedure was to obtain spectra for each star at several locations along the slit. The individual spectra were then averaged (to reduce the detector fixed pattern noise) resulting in S/N ratios of 50-60 in the 4300 Å region.
A New State Time and Frequency Standard of the USSR
Authors: Pushkin S.
Published: July 2016

In 1976 a new state primary time and frequency standard of the USSR was certified and confirmed with an error of reproducibility less than 1 × 10−13 and with an unavoidable systematic error less than 3–4 × 10−13. This standard includes a laboratory primary cesium beam frequency standard providing an independent definition of units in the SI system, primary hydrogen frequency standards preserving the units of frequency and time intervals, and hydrogen and cesium clocks providing the TA(SU) and UTC(SU) time scales.
Polar Motion and Earth Rotation Monitoring in Canada
Authors: Popelar J.
Published: July 2016

PZT observations of the Earth's rotation and polar motion have been carried out from observatories near Ottawa and Calgary since 1952 and 1968 respectively. A comprehensive re-evaluation and analysis of the PZT data is currently under way, using a new self-contained computer program which can easily accommodate changes of astronomical constants as well as modifications of the star catalogue.
Irregularities of the Polar Motion
Authors: Guinot Bernard
Published: July 2016

The independent series of coordinates of the pole obtained by the Defense Mapping Agency by observations of Transit satellites (DOP) and by the BIH using classical astrometry only (AST) are considered. They mainly differ by a periodic annual term. After removal of the mean annual difference from AST, the two series are compared. They show common and remarkable irregularities. A derivation of the excitation functions from DOP and AST shows also a good correlation. In the course of this study the constant improvement of DOP, which is now much better than AST, was noticed. The author expresses the opinion that the annual difference between DOP and AST is due to AST, which should therefore be calibrated against DOP.
Estimation of the Parameters of the Earth's Polar Motion
Authors: Wilson Clark R.
Published: July 2016

The parameters of the Earth's polar motion have been estimated by a method which accounts for observational error and which treats two possible statistical models for the polar motion excitation process. Both a 100 year and a 78 year long polar motion series have been used to estimate the Chandler wobble frequency, Fc, and quality factor, Qc; the noise level in the polar motion data; and the magnitude of the excitation process. Discussion of the annual component of polar motion has been omitted because its frequency (1 cycle per year (cpy)) and cause (annual motion of air and water) are presumed known.
Thermal Cyclotron Radiation from Solar Active Regions
Authors: Zheleznyakov V.V. , Zlotnik E. Ya.
Published: July 2016

Various frequency spectra with the fine structure resulting from the thermal cyclotron radio emission from solar active regions are discussed. The conditions in sources (distribution of magnetic field and kinetic temperature over the height) are put forward which provide the frequency spectrum as a set of cyclotron lines and high frequency cut-offs. For each kind of distribution the frequency spectrum and polarization are of peculiar character. This permits one to find the conditions in the source through the properties of the observed microwave solar radio emission. To obtain reliable data on the fine structure and judge about conditions in the sources it is necessary to study microwave solar radio emission using the swept-frequency or multi-channel receivers combined with high directional antennae.
Recent Development of the Nobeyama 17GHz Interferometer and Some Initial Results
Authors: Kai Keizo
Published: July 2016

We have constructed a 17GHz interferometer of a multi-correlator type at the Nobeyama Solar Radio Observatory. Novel features of the new interferometer are summarized as (i) high time-resolution up to 0.8 s and (ii) “real-time” calibration of the whole system with an accuracy of ~ 2% for amplitudes and ~ 2° for phases. With the aid of these advantages over an interferometer of a conventional drift-scan type we are able to detect and follow rapid time variations of even a faint source (say, ~ 0.5 s.f.u.) on the Sun with a spatial resolution of ~ 40″. The interferometer has been put in operation since July 1978. We have recorded hundreds of bursts at 17GHz in a year including some tens of rapidly changing sources which would not precisely be measured so far. We present here some preliminary results of observations such as polarization structures of both rapidly changing and GRF bursts.
Interferometric Observations of Radio Bursts at 35 GHz
Authors: Kawabata K. , Ogawa H. , Fujishita M. , Kato T. , Ishiguro M. , Omodaka T.
Published: July 2016

Observational results of radio bursts at 35 GHz by the sixteen-element fanbeam interferometer in Nagoya are briefly discussed.
Bursts Observed at 21 cm with the Westerbork Interferometer
Authors: Chiuderi-Drago F. , Palagi F.
Published: July 2016

During the radio observations of the Sun performed at λ = 21 cm on July 1st, 1974 using the Westerbork Radiotelescope (Bregman and Felli 1976; Chiuderi-Drago et al. 1977) four bursts were recorded. Two of them, which present some interesting peculiarity, that it would not be possible to observe with an instrument of lower resolving power, are discussed in this paper.
First Solar Radar Observations in Microwaves
Authors: Benz A. O. , Fitze H. R.
Published: July 2016

(Paper to be submitted to The Astrophysical Journal)

A first solar radar experiment in microwaves has been carried out with the 300 m dish in Arecibo. *The goal was to scatter the radio waves at 2380 MHz on coronal Langmuir waves in the range from 170 to 270 MHz. The nonlinear interaction of these two wave modes produce a radio signal in backward direction at the beat frequencies

Receiption was at 2600 MHz with a bandwidth of 100 MHz. The transmitter of 250 kW power was pulsed in periods between 0.5 and 1.5 s. The received flux was Fourier analysed and searched for the transmitter period.
On Modulations of Radio Type IV Bursts
Authors: Trottet G. , Kerdraon A.
Published: July 2016

It is well known that pulsations with quasi periodicities of the order of 1 s occur during type IV emissions. Recent observations of the Nançay Radioheliograph operating at 169 MHz have revealed the existence of modulations on a longer time scale and brought new information on the faster one.
Transition Between Type I and Type III Bursts in Closed or Open Magnetic Field Lines
Authors: Aubier Monique G.
Published: July 2016

When studying the propagation of accelerated electrons outwards in the corona, we have shown that the perpendicular momentum of the electrons remaining after the type I process is transformed into parallel momentum during the propagation along the decreasing magnetic field, and that type III emission can occur when the parallel velocity component reaches a critical value. With this model we explain in particular the low frequency cut-off of type I emission, the characteristics of the type III bursts near their starting frequency and the transition between type III- and type I-like decameter emission observed in few cases.
Hectometer and Kilometer Solar Observations
Authors: Stone R. G.
Published: July 2016

Three dimensional “snapshots” of the large scale solar magnetic field topology as well as the solar wind electron density distribution from about 0.1 to 1 AU are obtained by tracking traveling solar radio bursts at hectometer and kilometer wavelengths with instruments aborad the ISEE-3 satellite and the HELIOS-2 solar probe. Both instruments observe in the frequency range from 30 kHz to 1 MHz and both are equipped with dipole antennas located in the vehicle spin plane. ISEE-3 also has a dipole along the spin axis and the signals from the two ISEE-3 antennas are combined to give the azimuth and elevation angles of the radio source. Triangulation between HELIOS-2 and ISEE-3 provides the additional observation necessary to uniquely determine the position of the radio source in space at each observing frequency. The techniques will be outlined, and illustrated by an example of the three dimensional field geometry and electron density distribution determined by the observations.
Observation of a Coronal Impulsive X-ray Burst and its Implications Regarding the Associated Microwave Source
Authors: Kane Sharad R.
Published: July 2016

Radial structure of impulsive hard X-ray and microwave sources in solar flares is not well known at the present time. Measurements of near-the-limb flares with a high spatial and temporal resolution is, of course, the best way to determine the radial structure of these sources. In absence of such measurements, particularly for the hard X-ray emission, behind-the-limb flares provide (through occultation) a means of observing the coronal part of the impulsive source. Here we summarize the characteristics of the impulsive coronal X-ray source deduced from multi-spacecraft observations of a behind-the-limb flare and their implications with respect to impulsive microwave source.
Some Photometric Characteristics of be Stars (Review Paper)
Authors: Eugenio E. , Mendoza V.
Published: July 2016

Homogeneous observational data on four photometric systems which cover the spectral range from 0.14 to 4 microns through narrow, intermediate and broad passband filters are used to review and derive some photometric characteristics of Be stars. We find that 60% of the stars under discussion have ultraviolet and infrared excesses.
Long-Term Variation of Be Stars on the Color-Magnitude Diagram
Authors: Hirata Ryuko
Published: July 2016

The ratios α=ΔV/Δ(B-V) and β=Δ(U-B)/Δ(B-V) for the long-term variation of Be stars have been derived. The inclination effect on α is found. The dependence of α on the spectral type is also inferred. The signs of α and β are essentially the same.
Light Variations in Several Broad-Lined B Stars
Authors: Jerzykiewicz M. , Sterken C.
Published: July 2016

In our photoelectric searches for the β Cephei variables (JS77, JS79, and J82) several early B stars with nebulous lines were included. A summary of their photometric behaviour is presented in Table 1, columns four to six. Two of the stars, HR 2963 and HR 3476, are

apparently constant in light, HR 3213 is a short-period β Cephei star, HR 3462 shews ellipsoidal variations with a period of Od.563, which implies an orbital period twice that long (cf. also Shobbrook 1981), and HR 8854 is an eclipsing binary with P = 2d.3913.
Correlation Between Spectrum Characteristics and Photometric Behaviour of Be Stars
Authors: Ponomareva G. A.
Published: July 2016

Based upon a sample of 140 B0-A0 emission-line stars contained in “A Photographic Atlas of Be stars” statistical relationships between variable stars and Be stars are examined. It is found that 44 % of all the stars of the sample show some kind of photometric variations. The stars with narrow metallic absorption lines display relatively more intense photometric activity. Proceeding from this conclusion, the photometric variability of two stars HD 50138 and HD 193182 can be predicted.
The Strongly Polarized P Cygni Star with Infrared Excess CPD −52° 9243
Authors: Swings J. P.
Published: July 2016

The visible spectrum of the point-like source with infrared excess CPD-52°9243 is identified; emission and absorption line strengths are given together with various ion velocities of P Cygni profiles; a strong polarization is detected: P ≃ 5 %, θ ≃ 36°. From stellar and interstellar features, a spectral type around B8Ia and a distance of about 3.1 kpcs are derived.

A detailed publication is presently in press in Astronomy and Astrophysics.
Spectroscopic Observing Campaign
Authors: Barker Paul K.
Published: July 2016

With organization of the Photometric Observing Campaign well under way, there is an exciting opportunity for collaboration amongst the spectroscopists. I am proposing a program of regular ground-based spectroscopy of the 100 or so brightest northern Be stars, to be contemporaneous with the photometric program.
Ultraviolet Observations of Interacting Binary Be Stars
Authors: Peters Geraldine J. , Polidan Ronald S.
Published: July 2016

Initial results from the analysis of a series of timed, high resolution IUE observations of HR 2142, ϕ Per, CX Dra, KX And, AU Mon, and TT Hya are presented. The data base for HR 2142 also includes Copernicus U1 and U2 observations. Variable absorption lines, indicative of mass flow in the system, are observed in all objects except ϕ Per. We also, in general, find evidence of mass outflow in the form of winds and/or discrete components. We observe variable N V absorption in CX Dra and AU Mon and emission features in KX And and ϕ Per (C IV only). U1 data reveals the presence of complex structure in the gas stream in HR 2142. These observations are compared with those of Be stars which are not thought to be interacting binaries.
Far-Ultraviolet Colors of B Stars with and without Emission Lines
Authors: Zorec J. , Briot D. , Divan L.
Published: July 2016

A method free of interstellar reddening of comparing the energy distributions in the far-UV of Be/Shell stars to those of normal B stars is presented. The deviations of Be/Shell stars from the sequences of normal stars are correlated with other physical parameters observed in these stars. The largest UV color differences to the sequences of normal stars are found for those Be/Shell stars having the largest IR color excesses.
Spectral Energy Distribution (119–685 nm) in 16 Shell Stars and a Tentative Model for Accreting be Stars
Authors: Plavec Mirek J. , Dobias Jan J. , Weiland Janet L. , Stone Remington P.S.
Published: July 2016

I.U.E. low-dispersion spectra and spectral scans made with the Lick Observatory IDS scanners have been combined for 16 shell stars. Eleven objects can be represented by Kurucz model atmospheres, although some of them display strong shell-type line spectra. Five among them are known binaries. The six remaining objects (all interacting binaries) display complex spectra. A model involving continuum and line radiation from a hydrogen cloud surrounding the accreting component is proposed. A generalization of this model with optically thick segments of the cloud promises to explain even more exotic objects such as β Lyrae, W Serpentis and possibly ∊ Aurigae.
The Evolution of the System of Globular Clusters
Authors: Ostriker Jeremiah P.
Published: July 2016

Globular clusters have a sufficiently distinct character that we can treat the system of globular clusters, as a distinct object which has a size, mass and angular momentum, but also, an internal density distribution, velocity distribution, and, in general, a detailed interior structure. Shapley, of course, pioneered in the effort to model, that is to describe, the existing state of the system from our vantage point. At the present time we probably have an inventory of clusters which is largely complete, and for the majority of the identified systems we have good knowledge (cf for example Webbink, 1985) of positions in the galaxy, one component of galactic velocity and a sufficiently detailed picture of the interior dynamical state to characterize each cluster by a luminosity and two radii: a core radius rc where the surface density has fallen to half the central value, and a tidal radius rt determined by a fit to the King (1966) truncated isothermal profiles, which is thought to represent the radius beyond which the tidal force due to the galaxy effectively exceeds the force due to the clusters own gravity.
Harlow Shapley and the University of Missouri
Authors: Peterson Charles J.
Published: July 2016

The Laws Observatory of the University of Missouri is an example of the small university observatory that under lean financial circumstances succeeded for a number of years (1890-1920) as a successful research institution. Productive research appears to have been due to the temperament of the individual astronomers who had the ability to find projects which could be accomplished with small telescopes, minimal equipment, and few other resources. In these circumstances, a handful of students began careers in astronomy at the University of Missouri.
Abundances in Stars in Globular Clusters from Palomar CCD Spectra
Authors: Leep E. Myckki , Wallerstein George , Oke J. B.
Published: July 2016

We have completed abundance analyses of stars in three globular clusters: M71, M4. and M22. Spectra of resolution 0.3 and 0.6 (two pixel) resolution have been obtained with the Palomar coudé spectrograph and a TI CCD. The analysis was carried out with model atmospheres and f-values derived from three sources: absolute f-values derived by theory for the 6300 line of OI and for CN bands, laboratory f-values for lines that are too weak in the sun to be useful, and solar f-values. The last introduce an uncertainty of about 0.25 dex because solar f-values derived via the Holweger-Muller model differ from those derived via the BEGN model.
IUE Investigations at the Core of M 79
Authors: Altner Bruce
Published: July 2016

As a result of their investigation of 27 galactic globular clusters with the ANS satellite van Albada, de Boer and Dickens (1981) classified M 79 (NGC 1904) as an “extremely blue” cluster. It was also found to be a low luminosity x-ray source based on data acquired with the Einstein X-ray Observatory (Grindlay 1981). In this brief paper we discuss the stellar spectra extracted from two short wavelength (SWP) IUE images acquired at the “center of light” of M 79. Discrete peaks in the “spatially resolved”, cross-dispersion profile suggested the presence of at least three hot stars in the large aperture in both images (Fig. 1). The images in question are SWP 25303 and SWP 28936 for which it is important to note here that 1) the orientation of the large aperture on the plane of the sky differs for the two images by nearly 180° and 2) the target coordinates, determined from offset maneuvers with respect to a nearby SAO star, are nearly coincident. The cross-dispersion profile observed in the first spectrum is thus repeated in the second case, but is “flipped” left for right. Features immediately apparent in both images include a broad, asymmetric peak, almost certainly the blend of two or more components, and a second peak well separated from this blend and most likely a single star. In Fig. 2 we show the cross-dispersion profile of SWP 28936 and the best fit to that profile, assuming three components. From fits such as this and similar ones in other wavelength bins, we ultimately obtain from each image the entire SWP spectrum of each individual component.
One Micron Photometry of Omega Centauri Giants
Authors: Smith Graeme H.
Published: July 2016

The globular cluster ω Centauri is known to be chemically inhomogeneous, a property that reveals itself via a wide giant branch in the V, B-V color-magnitude diagram (Cannon and Stobie 1973). Typically a color range of δ(B-V) = 0.3 − 0.4 exists among giants with V < 13. However, in the red R, R-I (Norris and Bessell 1975, Bessell and Norris 1976), and I, V-I (Lloyd Evans 1977) diagrams a much tighter giant branch is seen. This has lead to the suggestion (e.g. Bessell and Norris 1976) that molecular absorption in the bandpass of the B filter has significantly reddened the B-V color, and thereby produced an anomalously wide giant branch.
The Metallicity Distribution Function of Halo Dwarfs and Globular Clusters
Authors: Laird J. B. , Rupin M. P. , Carney B. W. , Latham D. W. , Kurucz R. L.
Published: July 2016

Metallicities have been determined for a chemically unbiased sample of field halo dwarf stars. Their metallicity distribution function is similar to the predictions of a simple model of chemical evolution, but somewhat different from that of globular clusters.
The Similarity of the Halo Field K Giant Population by the Globular Cluster System of our Galaxy
Authors: Ratnatunga Kavan U.
Published: July 2016

Line-of-sight velocities and improved metal abundance estimates are available for a representative sample of 58 giants located by an objective prism survey (Ratnatunga and Freeman 1985), in a 20 square degree field near SA 127 (1 = 272, b = +39). These in-situ K-giants of the outer regions of our galactic halo give a direct comparison of the field population with the globular cluster system. Fig. 1 illustrates the distribution of line-of-sight velocity with abundance for the sample of giant stars in SA 127. The mean and dispersion of the sample appears to be discontinuous at [FeH] ~ −0.8. Fig. 2 shows the distribution of [Fe/H] with distance from the Sun for the same stars. The metal stronger giants (filled symbols) represent a population of stars up to 6 kpc above the plane of the disk and have a velocity dispersion of about 50 km/s. In contrast, the metal weaker giants have a typical halo dispersion of about 120 km/s.
On the Color Excesses of Globular Clusters
Authors: Straižys V. , Janulis R.
Published: July 2016

The interstellar reddening of globular clusters of the Galaxy is still an important unresolved problem, especially for metal-rich objects that are found usually at low galactic latitudes in the general direction of the galactic center. Their color excesses are needed in order to correct their color-magnitude diagrams and to determine their intrinsic integrated color indices. For this we need some method which is not related to measures of the cluster stars. One such method is to use foreground field stars in the direction of the globular cluster to measure the interstellar reddening. Because most of the globular clusters lie outside the galactic plane, we need information about the reddening in all the layer of absorbing dust in different directions. This information can be obtained by investigating stars which are at different distances from the Sun up to the edge of the absorbing dust layer. On the other hand, these stars should be as close as possible to the position of the globular cluster to avoid possible variations in the interstellar reddening in the area of the cluster.
BVRI Phtometry of Star Clusters in the Bok Region of the Large Magellanic Cloud
Authors: Liller William , Alcaino Gonzalo
Published: July 2016

It is at present difficult from the literature to intercompare ages of clusters in the Magellanic Clouds owing to the variety of ways in which authors have interpreted the observational data and the several theoretical models used. With these considerations in mind we have embarked on a homogeneous investigation of clusters within a sky area of about 1 square degree. Because of its large concentration of clusters, we have chosen for study the so-called Bok region (Bok and Bok 1969) located in the northwestern part of the LMC bar. Photographic BVRI color-magnitude and color-color diagrams are provided for the 14 clusters listed in Table 1. None of these clusters have had previous stellar photometry in R, I and only four of them in the BV passbands.