bluuebunny/crossref_metadata_2025 huggingface dataset:
Solar 5-minute Oscillations at 2.23 μm
Authors: Leifsen Torben
Published: June 2019

Large amplitude solar 5-min intensity oscillations have recently been detected at 2.23 μm using broad band (650 Å FWHM) photometry (Leifsen and Maltby, 1990). Large intensity amplitudes in a broad range in the near infrared was unexpected, and several questions concerning the source of the high amplitudes were raised. In an attempt to study the nature of these oscillations, time series of spectra have been obtained with the Fourier Transform Spectrometer (FTS) of the McMath telescope at National Solar Observatory at Kitt Peak. We present preliminary results from a 10 day long run in May 1991 in support for the suggestion that the results may be useful in both helio- and asteroseismological investigations.
High-l Rydberg Lines of Fe I in the ATMOS Spectra: 4f–5g, 5g–6h …
Authors: Schoenfeld William G. , Chang Edward S. , Geller Murray
Published: June 2019

We have identified the Fe I 4f–5g lines at 4 μm in the ATMOS solar spectra. Using the polarization model as previously applied to silicon, we predict and identify the 5g–6h lines at 7 μm. Additional absorption features at 2.5 and 12 μm are also shown to be due to high-l Rydberg transitions in Fe I.
1.5 μm Observations and the Depth of Sunspot Penumbrae
Authors: Solanki S. K. , Rüedi I. , Livingston W. , Schmidt H. U.
Published: June 2019

The magnetic structure of a simple, relatively symmetric sunspot is determined using the extremely Zeeman sensitive Landé g = 3 line of Fe I at 1.5648 μm. From the measured strength and inclination of the magnetic field we estimate the fraction of the total magnetic flux of the sunspot passing through the solar surface in the penumbra. It is found that on average approximately 1/2–2/3 of the total magnetic flux of the spot emerges in the penumbra. Sunspot penumbrae are therefore deep, i.e., the τ = 1 level does not correspond to the lower magnetic boundary of the spot in its penumbra.
A Magnetic Field Strength vs. Temperature Relation in Sunspots
Authors: Kopp Greg , Rabin Douglas
Published: June 2019

The near infrared presents several new and powerful advantages in the diagnostics of sunspot atmospheres: (1) increased magnetic sensitivity in Zeeman-split lines, (2) increased sensitivity of umbral brightness to temperature, and (3) reduced scattered light and seeing disturbances due to atmospheric turbulence. This has revealed a strong and consistent relationship between sunspot brightness and magnetic field strength.

We have made spatial/spectral observations of sunspots in the highly sensitive (g = 3) Fe I line at λ = 1.5649 μm to compare field strengths with continuum intensities. We find a characteristic but nonlinear relationship between magnetic field strength, B, and brightness temperature, Tb, in sunspots. In umbrae there is an approximately linear relation between B2 and Tb.
The IR Contrast of Magnetic Elements Obtained from High Spatial Resolution Observations at 1.6 μm
Authors: Darvann Tron A. , Koutchmy Serge
Published: June 2019

We report on new improved infrared (IR) imaging observations (1.6 μm) carried out with the National Solar Observatory's Vacuum Tower Telescope at Sacramento Peak, New Mexico (NSO/SP). Examples of high spatial resolution (up to 0.4″ images are shown, and results of comparisons between infrared and continuum at 526 nm and between infrared and the locations of enhanced magnetic field (“fluxtube regions” as defined by Mg I b1 line imaging) are given and discussed. Our results indicate that, close to disk center, magnetic elements have a positive contrast at the opacity minimum. This is contrary to the findings of several other authors (e.g., Worden 1975, Foukal et al. 1990). We emphasize the necessity of multi-color, high spatial and temporal resolution observations. The potential of present “almost-on-a-routine-basis” IR observations utilizing a fast video acquisition system developed at NSO/SP is pointed out.
Synthetic Infrared Spectra
Authors: Kurucz Robert L.
Published: June 2019

The Sun is the star we can observe with the highest spectral resolution and signal-to-noise. From studying the infrared spectrum we can learn about the Sun, about stars in general, and about atomic and molecular spectroscopy. We discuss the computer programs for spectrum synthesis, the infrared flux and central intensity atlases of the solar spectrum, and the atomic and molecular line data. Considerable work is still required to improve the observations and to improve the line data.
Observations of Infrared Emission from Galaxies
Authors: Roche P. F.
Published: June 2019

Aspects of the infrared emission from galaxies obtained from ground-based observations are described. There are clear differences between the dust in galaxies with active nuclei and those dominated by nuclear HII regions. In particular the family of unidentified emission bands between 3 and 13 μm dominate the spectra in the latter objects, but are rarely evident in spectra of active nuclei. However results from spatial, spectral and polarization measurements show that many of the dust properties in galaxies are broadly similar to those in the Milky Way.
The Izaña Cosmic Microwave Background Fluctuations Experiment: A Progress Report
Authors: Watson R.A. , Rebolo R. , Davies R.D. , Lasenby A.N. , Beckman J.E.
Published: June 2019

The Jodrell-IAC anisotropy experiment operating with twin 8° beams at 10.45 GHz over a two-year period, produced the reported limit of δ T/T≤3.7×10−5 (Davies et al., 1987: Nature 326, 462). Given the ability of this angular scale to strongly constrain cosmological models, it was decided to continue and expand the experiment by extending the horns to reduce the beam-size to 5°, while retaining the 8° separation. This improves the sensitivity to fluctuations by extending the angular range and decreasing beam-smearing.
The APM Galaxy Survey
Authors: Maddox S.J. , Efstathiou G. , Loveday J.
Published: June 2019

Wide-field surveys of galaxies and clusters are an indispensable tool for studying large scale structure in the universe. The Abell catalogue (Abell 1958), Zwicky catalogue (Zwicky et. al. 1961-1968), and the Lick survey (Shane and Wirtanen 1967, Seldner et. al. 1977) have provided many statistical results of key importance to our understanding of galaxy formation and clustering (see e.g. Peebles 1980). However, these surveys were constructed more than 20 years ago. Since then, there have been major technological developments in photographic emulsions, automatic scanning machines and computers. It is therefore possible to improve significantly on earlier surveys by generating deep galaxy catalogues with high photometric precision and uniformity over wide areas of sky. Over the last four years, we have taken advantage of these developments to construct a new survey of several million galaxies.
A Redshift Survey in the Direction of a Void near the Pisces-Cetus Supercluster
Authors: Brodie Jean P. , Willick Jeffrey , Bowyer Stuart , Burns Jack O.
Published: June 2019

The work described here has two main goals:

(1) To test the usefulness of Abell clusters for locating voids

It is well known that Abell clusters are not uniformly distributed in three-dimensional space (e.g. Bahcall and Soneira, 1983). Recently, Batuski and Bums (1985a, b) have suggested that Abell clusters tend to form filamentary structures between which there appear to be large regions (50–200 Mpc across) devoid of bright galaxies. The technique of using Abell clusters as tracers of voids is controversial because the correlation length of Abell clusters is so much larger than the galaxy-galaxy correlation length. However, compared to an all-sky magnitude-limited survey, the technique, if valid, potentially reduces the amount of telescope time required to identify significant voids and map them in redshift space. To investigate this possibility we have undertaken a redshift survey of galaxies in the direction of a nearby and relatively compact candidate void surrounded by a ring of Abell clusters.

(2) To identify a void suitable for more extensive study.

Ultimately we would like to know not only the degree to which voids are empty, but also to what extent those galaxies that may be found within a void differ from those in the surrounding shell. Some theorists (e.g. Dekel and Silk, 1986 and references therein) suggest that as a result of biased galaxy formation, galaxies within a void might be expected to be preferentially younger, fainter, more irregular, more metal-poor and more gas-rich than shell galaxies. The region we selected for study is one which forms part of the Haynes and Giovanelli (1986 and references therein) 21 cm redshift survey. It was chosen, in part, because it is of interest to compare optical results with radio data to determine whether or not the two techniques reveal the same structure.
Is Coma a Young Aggregate of Old Subclusters?
Authors: Mellier Y. , Mathez G. , Mazure A.
Published: June 2019

Evolution of gravitational systems is currently believed to follow a 3-stage scheme:

Stage 1: Subclusters form first ouring violent relaxation

Stage 2: Dynamical friction mass segregation

Stage 3: contraction of core, expansion of halo
Cosmic Strings as a Candidate for Dark Matter. Astrophysical Formulae
Authors: Dabrowski M.P. , Stelmach J.
Published: June 2019

We consider homogeneous, isotropic universe with arbitrary curvature (k=0, ±1), filled with dust, radiation, ˄-term and a set of noninteracting strings (i.e. scaling as ρs ∼ R−2, hence yielding string dominated universe). For such model we find analytic solution of the Friedman equation using Weierstrass functions. We realize that addition of (rather unrealistic component) stable domain walls (ρw ∼ R−1) to the model, does not essentially complicate the calculations.
Are Voids Present in the Lyman-Alpha Forest?
Authors: Crotts Arlin P. S.
Published: June 2019

If voids like those seen in the low z galaxy distribution existed in the H I distribution at z ≈ 2, then high quality QSO spectra, with many Ly-α forest lines per unit z, could be used to discern the voids from the usual random fluctuations in observed number density of lines (≡ n). Several such spectra have been obtained, and these show evidence for gaps in the Ly-α distribution on scales of 20 to 50 h−1Mpc (comoving coordinates, with h = H0/66.7 km s−1Mpc−1, assuming q0 = 0.1). These results are summarized in the table below. All QSO spectra with a line-of-sight n of Ly-α lines n > 80 per unit z and total number of lines N > 40 known to the author are included (except that of PKS 2000-330 [c.f. Carswell and Rees 1987], which is broken into five separate segments of Ly-α forest by gaps in the data and a broad absorption line). Excluded are portions of these spectra where n falls more than 25% below the mean due to instrumental bias. For each of these the distribution of gaps between nearest-neighbor Ly-α redshifts is computed as a function of gap size. If the distribution of redshifts were Poisson, the distribution of gaps should be a decreasing exponential function of gap size. For the two best spectra, large deviations from an exponential are found in the range of 20 to 50 h−1Mpc (in the other four cases, it should be noted that a large number of gaps of such sizes are still expected from Poisson fluctuations). The probability that such deviations are statistically consistent with an exponential distribution is shown in the fifth column of the table.
QSO Surface Density at Faint Light Levels
Authors: Afanasiev V. L. , Dodonov S. N. , Boller Th. , Lorenz H. , Yu. Terebizh V.
Published: June 2019

Two independent fields of 14′ × 14′ south east of M82 and 7′ × 7′ in SA 57 were completely spectroscopicaly searched for quasars using the Multi Slit Field Spectrograph at the 6-meter telescope of the Academy of Sciences of the USSR (Dodonov, 1982).
Morphology of High Redshift 3CR Galaxies (Z>1), from High Spatial Resolution Imaging
Authors: Le Fèvre O. , Hammer F. , Nottale L. , Mazure A.
Published: June 2019

This sample is a small one, typically 20 galaxies with z > 1, is radio flux limited and contains the most distant galaxies we presently know. Gravitational lensing by foreground galaxies and clusters of galaxies may enhance the luminosity of these galaxies by several magnitudes in both optical and radio wavelenghts. Moreover this flux limited sample should have a disproportionate number of gravitationaly amplified objects specifically because their radio fluxes are very close to the 10 Jy detection limit. When considering the spatial distribution of the 3CR galaxies with z > 1 it is found that many cases exist in which a 3CR galaxy is located near the center of a rich cluster of galaxies and/or with a foreground galaxy projected within a few arcseconds. These instances are strongly suggestive that gravitational lensing effects are likely to be present (see Hammer et al., 1986, Astr. Astroph., 169, LI, Le Fèvre et al., 1987, Nature, 326, 268). Moreover, it is not well established that these galaxies are the progenitors of lower redshift ellipticals and radio-galaxies and that they can be compared for galaxy evolution tests.
On the Possibilities of Detecting Dark Matter by the Gravitational Lens Effect
Authors: Kayser R.
Published: June 2019

A class of compact objects with cosmological density ƍ leads to a probability for multiple imaging by gravitational lensing of roughly P ≈ ƍ/ƍc, where ƍc is the critical density.
Refraction In Tycho Brahe's Small Universe
Authors: Moesgaard K.P.
Published: June 2019

Tycho Brahe's work set a new standard of objectivity in empirical science. Aiming at an observational accuracy of one minute of arc he had to introduce corrections of atmospheric refraction. This proved to be anything but trivial, mainly because Tycho adopted the traditional value of 3′ for the parallax of the sun. This parameter measured the size of the entire planetary system which Tycho refrained from vizualizing larger than conventionally accepted.
Mapping The Sky With The Carlsberg Automatic Meridian Circle
Authors: Morrison L V , Helmer L , Quijano L
Published: June 2019

The contribution of the Carlsberg Automatic Meridian Circle to the improvement of the stellar reference frame is reviewed.
Solar Motion And Galactic Rotation: Results From The Lick Northern Proper Motion Program
Authors: Hanson Robert B.
Published: June 2019

This paper reports the first results of solar motion and galactic rotation studies which are being done at Lick Observatory, using the new data from the Lick Northern Proper Motion (NPM) Program. This study finds: (1) A = +11.31 ± 1.06 and B = −13.91 ± 0.92 km/s/kpc, consistent with a nearly flat galactic rotation curve with a local circular velocity near 200 km/s; (2) solar apex locations lying near the standard apex for low galactic latitudes, but trending strongly toward the direction of galactic rotation for high galactic latitudes; (3) RMS external error estimates for the Lick proper motions: for the absolute zero-point in a typical NPM field, and for the overall systematic zero-point error. A more detailed presentation of these results has been given by Hanson (1987). The NPM program is reviewed in another paper in this Symposium, and has been described in detail by Klemola, Jones, and Hanson (1987).
Statistics — Spatial and Velocity Distribution of Planetary Nebulae
Authors: Cahn J. H. , Wyatt S. P.
Published: June 2019

The problems of the spatial and velocity distributions of planetary nebulae in our galaxy are still very much with us. In what follows we comment rather hastily on the older work and more especially on the recent work in these fields. We have not been able to carry out an exhaustive literature search, and therefore trust we shall be forgiven by those whose contributions do not appear herein. We first survey the scene in the greater solar neighborhood. Section 2 deals with the local spatial distribution of planetaries in the galactic plane and perpendicular to the plane. Section 3 focuses on the rather meager results that can be obtained on the kinematical properties of the planetaries in our general part of the galactic system. We conclude by moving farther afield and exploring another part of the galaxy and the galaxy as a whole. Section 4 addresses the distribution of planetaries and summarizes recent estimates of the total planetary population of our galaxy. Finally, Section 5 is devoted to what little one can conclude about the overall kinematical properties of the system of planetaries.
Observations of Cool Dust in Planetary Nebulae
Authors: Moseley Harvey , Harper D.A.
Published: June 2019

We have observed BD +30 3639, IC 418, NGC 6572, NGC 6543, NGC 3918, NGC 2440, NGC 3242, A30, Ml-78, and NGC 6210 in two broad passbands with effective wavelengths of 35μand 75μ. All were detected at 35μ, and all but IC 4997 at 75μ. Their spectral energy distributions are similar in that most have peak flux densities at wavelengths ranging from 30μto 45μ. The two nebulae with markedly different energy distributions are IC 4997, which has a hot spectrum peaking near 20μ, and Ml-78, whose flux density rises rapidly from 35μto 75μ, characteristic of compact H II regions.
Ionization Models of Planetary Nebulae
Authors: Harrington J. Patrick
Published: June 2019

Our knowledge of the ionization structure of gaseous nebulae may be dated from the classic paper of Strömgren (1939), who showed that the transition between ionized and neutral hydrogen is sharp. In fact the very sharpness of the transition region has at last become a difficulty. Another milestone was the paper of Hummer and Seaton (1964) which clarified the structure of nebulae containing helium as well as hydrogen. Then, just a decade ago, the first models of planetary nebulae were constructed which detailed the changes in the temperature and in the ionization of the heavy elements as the stellar radiation was progressively diminished by absorption in the nebular gas (Goodson, 1967 Harrington, 1968; Williams, 1968; Flower, 1969a). These first models were of a general nature, but soon models were constructed to match specific nebulae (Flower, 1968, 1969b; Harrington, 1969; Kirkpatrick, 1970).
The Bowen Fluorescence Mechanism for Spherically Symmetric Planetary Nebulae
Authors: Wehrse R. , Peraiah A.
Published: June 2019

The transfer equation for the interlocked Hell Lya/OIII 2p2P2 − 2p 3d P2° lines is solved for spherical symmetry and for comparison in plane parallel approximation in the framework of the discrete space theory of radiative transfer. We used Harrington's ionization model (1969) without velocity fields and applied the partial redistribution function RIIA for both lines.
Models of Planetary Nebulae
Authors: Perinotto M.
Published: June 2019

From existing models of planetary nebulae an important discrepancy comes out with the low ionization potential ions, as N+ and 0+, whose calculated line intensities are smaller than the observed ones. In this work the effect of charge transfer reactions between single, double, and triple ionized oxygen and nitrogen with neutral hydrogen is taken into account in a model of NGC 7662. The ionization structure of oxygen and nitrogen becomes strongly modified. The computed fractional abundances of 0+ and N+ turn out substantially larger than in previous models, thus helping to reconcile the computed line emissions from low ionization potential ions with the observed ones. (Paper will appear in Astronomy and Astrophysics.)
A Theoretical Model of NGC 7027
Authors: Péquignot Daniel
Published: June 2019

It is demonstrated that ionization structure of NGC 7027 cannot be explained by static models based on the standard photoionization theory unless some complementary physical process is included. The main discrepancies are successfully eliminated by including charge transfer reactions with hydrogen for the following ions: C+, C+3, N+2, O+2, Ne+2, S+ and S+3, the rate coefficients being probably of the order of or larger than 10−9cm+3s−1 except for C+ and Ne+2; in addition the charge exchange rate for N+ is probably ∼200 times smaller than the value proposed by Steigman et al. (1971).
Electron Temperature and Density Mapping in Planetary Nebulae
Authors: Reay N.K. , Worswick S.P.
Published: June 2019

The linear response of the electronographic process provides a simple method for producing relative intensity ratios of emission lines across a complete nebula. Using narrow-band filters to isolate those lines which are sensitive to electron temperature and density changes, it is possible to map the gross variation of these quantities across the object.
Chemical Abundances of Planetary Nebulae in NGC 185, 205, and 221
Authors: Jenner David C. , Ford Holland C.
Published: June 2019

Results are most complete for NGC 185–1, where the electron temperature is 17,900±1600°K. Compared to typical galactic planetary nebulae the abundance ratio in NGC 185–1 of helium/hydrogen (0.24±0.08) is approximately twice that normally found, the abundance ratio of oxygen/hydrogen (7.7±1.3)10−5 is approximately one-tenth that normally found, and the ratio of nitrogen/hydrogen (1.4 × 10−4, poorly known) is approximately equal to that normally found.
Evolution and Gas Dynamics of Planetary Nebulae
Authors: G. Mathews William
Published: June 2019

Since the last IAU Symposium on Planetary Nebulae at Tatranska-Lomnica, a number of significant theoretical and observational advances have been made in the study of nebular dynamics. The following review emphasizes the evolution of nebulae after they have been ejected from the central star and have become optically thin to most radiation.
Examples of Multiple Shell Structures in Planetary Nebulae and Certain Peculiar Emission Nebulae
Authors: Gull T.R.
Published: June 2019

There i s increasing evidence that multiple shell structures occur often in planetary nebulae and emission nebulae surrounding Oef and Wolf-Rayet Stars, yet the multiple shell structures in the two classes of objects are very different. In planetary nebulae they are defined by an internal structure filled by [OIII] 5007 emission, and an outer shell that is most noticeable in the light of singly-ionized species such as [Oil], [SII] or [Nil]. Planetary nebulae with multiple shell structure are well exemplified by NGC 6853 (The Dumbbell Nebula) and NGC7293 (The Helix Nebula). The most pronounced effect is [OI] condensations plus [NII], [OII], [SII] “shadows” and complementary [OIII] structure.
Planetary Nebulae and Chemical Evolution of the Galaxy
Authors: Tinsley Beatrice M.
Published: June 2019

The chemical evolution of galaxies is controlled by star formation, stellar mass loss, gas flows, and the compositions of matter involved in these processes. Planetary nebulae (PN) thus affect chemical evolution directly in representing mass ejection at the end of the nuclear burning lives of many stars, and in enriching the interstellar medium in elements that are overabundant in the nebulae. Supernovae often eclipse PN in discussions of these effects, so it is noteworthy that planetary precursor stars not only provide much of the present stellar mass loss in the solar neighborhood, but also show as clear evidence as supernova remnants for the ejection of elements newly synthesized in the stars themselves. Furthermore, PN are tracers of the past star formation history in a galaxy, since their rate of occurrence depends on the birthrate of progenitor stars during the whole lifetime of the system.
Gas-Phase Abundance Anomalies and the Origin of Planetary Nebulae
Authors: Shields G.A. , Scalo J.M.
Published: June 2019

Six high-excitation PN are found to have gas-phase iron abundances less than solar by M.2 dex, and carbon abundances larger than solar by M3.8 dex. The objects have solar abundances of oxygen, and this supports the idea that the missing iron has condensed into grains. Efficient condensation of iron, and of all carbon not in CO molecules, is expected before the shell becomes ionized. The presence of some gas-phase iron therefore requires partial destruction of the grains.
Has the Universe the Cell Structure?
Authors: Jôeveer Mihkel , Einasto Jaan
Published: June 2019

As demonstrated by de Vaucouleurs (1956, 1975a, b, 1976), Abell (1961), Karachentsev (1966), Kiang and Saslaw (1969) and others, clusters of galaxies as well as groups of galaxies have a tendency to form second-order clusters of galaxies, often called superclusters. Recent statistical studies by the Princeton group (Davis, Groth and Peebles 1977, Seldner and Peebles 1977a) have confirmed this result. Statistical studies, however, give little information about the internal structure of second-order clusters.
Counts of faint galaxies
Authors: Karachentsev I. D. , Kopylov A. I.
Published: June 2019

The number-magnitude relation for galaxies is an insensitive test for discriminating between cosmological models. Nevertheless, counts of faint galaxies enable us to investigate possible evolutionary effects, which may be caused by time dependence of the luminosity and/or number density of galaxies.
Intrinsic Parameters of Hot Blue Stars
Authors: Kudritzki R.P. , Hummer D.G.
Published: June 2019

Advances in both theoretical understanding and observational capabilities in the past few years have made possible the determination of the effective temperature, surface gravity and chemical abundance of massive stars with unprecedented accuracy. These data are in turn important for the study of galaxies, as stars are important sources of information concerning the evolutionary state, past and present chemical composition, and distance of the parent galaxy. In addition to this diagnostic role, stars are crucial as sources of light, matter, and metals in the galaxy. Thus an improved understanding of massive stars makes possible a better determination of the physical conditions in a galaxy as well as a deeper understanding of how it functions.
The Massive Stellar Wind of the Hubble-Sandage Variable S Doradus
Authors: Leitherer C. , Appenzeller I. , Klare G. , Lamers H.J.G.L.M. , Stahl O. , Waters L.B.F.M. , Wolf B.
Published: June 2019

We present coordinated spectroscopic and photometric observations obtained during the present bright phase of the luminous variable star S Dor in the LMC. High resolution spectrograms in the satellite UV and in the visual range were obtained with IUE and with CASPEC (attached to the ESO 3.6-m telescope), respectively. Moreover, photometric UBVRIJHKL observations were carried out.
High-Dispersion Spectroscopy of the Brightest Emission-Line Stars of the Magellanic Clouds
Authors: Stahl O. , Wolf B. , de Groot M. , Leitherer C.
Published: June 2019

We present an atlas of high dispersion spectra of 24 of the brightest peculiar emission-line stars of the Magellanic Clouds.

Our spectra cover the wavelength range from 3600 to 4900 Å. They have been obtained from 1970 to 1984 with the coudé spectrograph of the ESO 1.52 m telescope at La Silla, Chile. The spectral resolution is 0.4 Å for most of the spectra and 0.2 Å for the very brightest stars. Up to 11 spectra are available for one star. In addition, we have done UBVRIJHK(LM) photometry at several epochs of all stars of our sample.
Stellar atmospheric instability in the upper part of the Hertzsprung-Russell diagram
Authors: de Jager C. , Nieuwenhuijzen H.
Published: June 2019

The upper limt of stellar luminosity in the Hertzsprung-Russell diagram is a line running approximately from (log Teff; log (L/L⊙) = (4.5; 6.3) via (4.0; 5.74) to (3.5; 5.7) (Humphreys and Davidson, 1979; Humpreys, 1983).
Summary Talk: What is happening to Massive Stars in Galaxies?
Authors: Graham J. A. , Armandroff Taft E.
Published: June 2019

Highlights of the IAU Symposium 116 are reviewed. Some of the general themes running through the meeting are identified. These include:i) the fruitful interaction between observation, laboratory work and theory. ii) the need for understanding and, if possible, correcting for the effects of incompleteness and bias in observing lists. iii) the importance of the Magellanic Clouds, as the nearest independently evolving stellar systems, in the study of massive star formation and evolution in galaxies.
Convective Overshooting: New Integrated Colours vs. Age Relations for Star Clusters
Authors: Bertelli G. , Bressan A.G. , Chiosi C. , Nasi E. , Pigatto L.
Published: June 2019

If the integrated colours of a star cluster mainly depend on chemical composition and age, then theoretical calibrations of colours as function of age for different chemical compositions are very useful to obtain quantitative determinations of the age and composition of individual clusters, and thus to trace the chemical history of nearby galaxies. Several calibration curves exist in the literature which rest on the standard theory of stellar evolution. However, a growing amount of observational evidence seems to indicate that overshooting from convective cores may be an important phenomenon in stellar evolution. In fact models computed with overshooting are significantly different from the standard ones. The aim of this preliminary investigation is to study the effects of convective overshooting on the integrated colours of clusters whose turnoff mass is in that range in which convective overshooting is effective.
The Peculiar Velocity of the Local Group in the Direction of the Virgo Cluster
Authors: Staveley-Smith L. , Davies R. D.
Published: June 2019

The measurement of the amplitude of the Local Group infall velocity towards the Virgo Cluster is a crucial test for the value of the universal density parameter Ωo and the ratio of the universal Hubble constant to its local value. However, a very large discrepancy exists between total infall velocities derived from peculiar velocity field observations and those derived from “scaling” methods using standard candles in the Virgo and Coma clusters. The former have tended to produce high Virgocentric peculiar velocities (350 to 500 km s−1) whilst the latter give much lower values (-70 to 100 km s−1).
Is the Ratio of Dark-to-Luminous Matter a Function of Galaxy Mass and/or Luminosity?
Authors: Carignan C.
Published: June 2019

The study of the ratio of dark-to-luminous matter in spiral galaxies has been the subject of several recent studies (Bahcall 1983; Casertano 1983; Carignan and Freeman 1985; van Albada et al. 1985; Carignan 1985). These studies have been possible because of the large number of high sensitivity HI observations which became available in the last few years, allowing to probe the halo potential to very large galactocentric distances. In the case of NGC 3198 (van Albada et al. 1985), it was even possible to derive the rotation curve out to 11 disc scale lengths. One of the important questions, forming the motivation for this type of work, is whether the ratio of dark-to-luminous matter is a function of galaxy mass and/or luminosity.
Voids in the 2D CFA Catalog
Authors: Lachièze-Rey M. , Bouchet F.
Published: June 2019

The void probability function was known from a long time to be an efficient tool in analysing the galaxy repartition (White, Sharp, Schaeffer). We developed a method to determine this quantity with a minimum noise, for any proposed distribution resulting from observations, simulations, or theory. We apply it here to the 2D-CFA catalog. This will be later compared to other 2D galaxy catalogs, to the 3D CFA catalog and to the results of numerical simulations.
Halos and Disk Stability
Authors: Kalnajs Agris J.
Published: June 2019

The need for halos on stability grounds is not at all compelling. Compared to a bulge, a halo is not very efficient in stabilising a disk. Because the effect of a modest halo is small, it is difficult to infer its presence or absence from stability arguments.
Baryogenesis in the Inflationary Universe
Authors: Kodama Hideo , Sato Katsuhiko , Sato Nobuaki
Published: June 2019

As is known well, the inflationary universe model resolves most of the fundamental problems concerning the large scale structure of the universe and is now becoming a standard model for the early universe. However, there is one important problem yet to be made clear. In this model the number density of particles effectively goes to zero during the inflation and everything is created after the universe is heated up again at the end of inflation. Since the reheating temperature is much lower than the GUT temperature in general, however, it is not clear whether the observed baryon asymmetry is generated in this process.
A 75cm alt-az telescope with short time focus exchanging system
Authors: Isobe Syuzo , Shinohara Nobuo , Agata Hidehiko
Published: June 2019

The Sundai senior high school built a telescope with an alt-az mounting and an aperture of 75cm. A photographic camera at the prime focus, and an SIT camera, a photomultiplier, and a spectrograph at the Nasmyth focus are prepared. Time needed for the exchange between instruments is in less than a minute. Therefore, effective observations are performed by changing the instruments which are proper for the sky condition at the observed night.
A single-channel polarimeter
Authors: Jain S. K. , Bhattacharyya J. C.
Published: June 2019

We have developed a single-channel photopolarimeter to measure polarization ∼1%, with an accuracy of 0.1% or so. Laboratory tests show that the performance of the instrument is as per the requirements.
Study of Bok globules with small telescopes
Authors: Kulkarni P. V. , Deshpande M. R. , Joshi U. C. , Kulshrestha A. K.
Published: June 2019

Polarization of radiation in the UBVRI spectral bands of the stars in the vicinity of four Bok Globules/dark clouds is observed with 1.5 and 1m telescopes. Moderate to high degree of polarization and alignment of polarization vectors indicate the possibility of frozen magnetic fields. Other possibilities for retarding the cloud collapse have also been pointed out.
Starspot imaging using VRI photometry
Authors: Cameron A. Collier
Published: June 2019

Recent progress on maximum-entropy imaging of stellar surface brightness distributions using VRI photometry and Doppler-broadened absorption line profiles is reported. VRI photometry generally provides tighter constraints on starspot configurations than does Doppler imaging (which requires the use of large telescopes). Observers carrying out long-term photometric monitoring programmes on spotted stars are urged to work in the VRI system, as well as the UBV.
Long term period behaviour of contact binaries
Authors: Kennedy H. D.
Published: June 2019

Determination of the rate of mass flow in contact binary systems is one of the most important motives for their observation. Many of these binaries are in over-contact configuration with a common equipotential surface located somewhwere between the inner and outer Lagrangian zero-velocity surfaces. Most are active systems displaying frequent lightcurve and period changes resulting in residuals behaviour depictable by intersecting linear segments.
Photometry of RZ Ophiuchi - an international collaboration
Authors: Knee L.B.G. , Scarfe C. D. , Baldwin B. W. , Meatheringham S. J.
Published: June 2019

UBV observations, plus a few in R and I, were obtained during the 1984 eclipse of RZ Ophiuchi. Bolometric corrections and temperature calibration, applied to the magnitudes and colours of the stars, were used to derive the ratio of the stellar radii, and a light curve solution was obtained with this parameter fixed. Neither component fills its Roche lobe, but the system may be at a late stage of case C mass transfer.
Photometry of the RS CVn binary II Peg
Authors: Mohin S. , Raveendran A. V. , Mekkaden M. V.
Published: June 2019

B and V photometry of II Peg obtained at Kavalur on 39 nights during 1980–81, 1981–82 and 1984–85 observing seasons is presented in Fig. 1. From an analysis of the available data on this object we find that no two light curves agree in any of the following: shape, amplitude, phases of the light maxima and minima, mean light level, or brightness at the light maxima and minima.
Radial velocities with CORAVEL: results on stellar variability and duplicity
Authors: Burki G. , Mayor M.
Published: June 2019

The complete radial velocity curve has been determined with CORAVEL for many pulsating stars of various classes: cepheid stars in the Galaxy and in the Magellanic Clouds, RR Lyrae, δ Scuti and SX Phoenicis stars. These measurements allow the determination of the radius variation and of the surface acceleration of these stars. In addition, the mean stellar radius of many of these stars has been determined by applying the Baade-Wesselink method.

Systematic surveys of definite groups of binary or multiple stars are in progress with CORAVEL in order to determine the distribution functions of the orbital parameters. The eccentricity distributions for the binaries in the open clusters Pleiades, Praesepe, Coma Ber and Hyades are presented and their dependence on the physical processes (star formation mechanisms, mass exchange, tidal circularization, dynamical evolution) is briefly discussed.
Optical Observations related to the Molecular Chemistry in Diffuse Interstellar Clouds
Authors: Federman S. R.
Published: June 2019

Observations, which have been published since 1979, of molecular species in diffuse clouds will be discussed. Particular attention will be given to the ultraviolet measurements of CO with the Copernicus and IUE satellites and to ground-based optical measurements of CH, CH+, CN, and C2. These data encompass large enough samples to test the chemical schemes expected to occur in diffuse clouds. Upper limits for other species (e.g., H2O, H2O+, and C3) place restrictions on the pathways for molecular production. Moreover, analysis of the rotational distribution of the C2 molecule results in the determination of the physical conditions of the cloud. These parameters, including density, temperature, and the intensity of the radiation field, are necessary for modeling the chemistry.
The Nitrogen Chemistry in Interstellar Clouds
Authors: Langer William D. , Graedel T. E.
Published: June 2019

Our time dependent model of chemistry of dense interstellar clouds has been extended to study the formation of nitrogen bearing molecules. Here we present results for the calculations, under a variety of density, temperature, and elemental conditions, of the abundances of the following observationally important species: CN, HCN, HNC, NH3, NO, and N2H.
Observational Constraints on Silicon Chemistry in the Circumstellar Envelopes of Red Giants
Authors: Sahai Raghvendra
Published: June 2019

We review observations to date of silicon-bearing molecules in circumstellar gas and dust around red giants. New constraints on circumstellar chemistry are provided by the discovery of (i) a systematic decrease in the [SiO]/[H2] ratio with mass loss rate, ii) SiO in carbon-rich CIT 6. The presence/absence of SiO maser emission in oxygen-rich/carbon-rich envelopes is linked to differences in grain composion and the grain-condensation radius.
Radio and Millimeter Observations of Circumstellar Envelopes
Authors: Zuckerman B.
Published: June 2019

Circumstellar chemistry has been confined largely to analysis of a few dozen molecules in the envelope of one carbon-rich star, IRC+10216. A new generation of large millimeter wavelength telescopes promises to broaden the data base to include many other stars and additional molecules. Carbon-monoxide emission has already been detected from approximately 130 stars and many of these are prime candidates for chemical studies. The detection of HCN emission in a few oxygen-rich stars was quite unexpected and indicates that nonequilibrium chemical processes are important in at least some circumstellar envelopes. New millimeter wavelength interferometers can measure the spatial distribution of various molecules for comparison with predictions of models for photodissociation, freeze-out on grains, self-shielding, and nonspherical outflow.
Circumstellar Chemistry: Theoretical Studies
Authors: Omont Alain
Published: June 2019

The different chemical processes responsible for the observed molecular abundances in massive circumstellar shells are examined: freezing-out of chemical equilibrium, radical and ion reactions, grain and shock processes, photochemistry, etc…
Primitive Matter in Meteorites
Authors: Bhandari N.
Published: June 2019

A large number of elements in certain meteorites have isotopic composition different from that existing in rocks of the earth or the moon. Excess amounts of some isotopes, which are radiogenic daughters, are attributed to the in situ decay of their parent nuclide. Material containing radioactive parents is believed to have been injected into the condensing solar nebula, from astrophysical sites of their production shortly before formation of these grains. Other isotopic anomalies do not show mass dependent pattern which is characteristic of chemical fractionation. They must be primary isotopic abundances, if it is assumed that physico-chemical processes in the solar nebula cannot produce non-mass dependent fractionation. In such a case the observed isotopic ratios characterise elements differently synthesised and injected into the solar nebula which condensed before it had enough time to homogenise. Thus the isotopically anomalous matter has extra solar origin and may contain supernovae condensates, interstellar matter or dust from other stars. The evidence for different isotopic anomalies is briefly summarised and discussed in terms of the current ideas regarding chemical processes occurring in the early solar system.
Extended Line Emitting Regions in the Seyfert Galaxy NGC 2992
Authors: Colina L. , Fricke K.J. , Kollatschny W. , Perryman M.A.C.
Published: June 2019

NGC 2992 is a nearby Seyfert galaxy (z=0.008, 1″=150 pc, for HO=75 km s−1 Mpc−1) seen almost edge-on (i=70°). A dust lane crossing the galaxy has been detected (Burbidge et al. 1972, see also Fig. 1) and the presence of two extended radio-emitting regions at position angles P.A. 130° and P.A. 160° has been reported (Ulvestad and Wilson, 1984).
The Low Frequency Variability of Extragalactic Radio Sources
Authors: Altschuler D.R. , Dennison B.K. , Mitchell K.J. , O'Dell S.L. , Broderick J.J. , Condon J.J. , Payne H.E.
Published: June 2019

The spectral evolution between 0.3 and 15 GHz of the extragalactic radio sources 0235+164 and 1611+343 (DA406) is presented. The data show two very different forms of behavior. For 0235+164 the variations over the entire frequency range are correlated and consistent with being intrinsic to the source, whereas for DA406 an extrinsic cause for the variability seems probable.
On the Radio Emission from Interacting Spiral Galaxies
Authors: Malumian V.H.
Published: June 2019

It is shown that the power of radio emission of spiral members of double galaxies depends on their projected distances. For example, the members of pairs with projected distances lower than 10 kpc are 2–2.5 times more powerful than members of pairs with distances larger than 50 kpc. Since 90% of “interacting” spiral galaxies belong to pairs with separations smaller than 50 kpc this means that the members of interacting pairs are more powerful radio emitters than the components of non-interacting pairs.
Infrared observations of GGD objects
Authors: Carballo R. , Eiroa C. , Mampaso A.
Published: June 2019

We present accurate positions and near infrared photometry (Table I) of 11 point-like objects in the neighbourhood of GGD objects obtained on the 1.55 m and on the 1.23 m in Teide Obs. and Calar Alto Obs. respectively, in Spain. Several of the near infrared sources are directly associated with the GGD nebulae and/or are candidate for their excitation. In addition some of them seem to be the near infrared counterparts of IRAS sources. We believe, on the basis of their infrared excess, far infrared emission (IRAS), association with nebulosity, coincidence with H2O masers or the fact that in most cases the observed luminosities are higher than those expected for main sequence stars, that most of them (9/12) are young stars embedded in the dark clouds which contain the GGD objects. The loci of the detected sources in an (H-K,K-L) infrared two-colour diagram is the same as that obtained for known pre-main sequence stars, such as T Tauris and Herbig Ae-Be stars, indicating the presence of dust shells with temperatures in the range 800–1500 K. The observed range in luminosity, 10–4600 L⊙, added to other different characteristics found between them, such' as the presence, or absence, of H2O masers, indicates the interest for a detailed study of the infrared sources and related GGD nebulae.
On the nature of protostellar H2O masers
Authors: Rudnitskij G. M.
Published: June 2019

Most sources of B2O maser radio emission at 1.35 cm, associated with star formation regions, show strong variability with, sometimes, rapid bursts of emission (see, e.g., Liljeström 1984, Rowland and Cohen 1986, and references therein). A preliminary conclusion on the possible cyclicity of H2O maser variability can be drawn (Lekht et al. 1982, 1983), with a quasiperiod of several years. The “quiet” state of a maser source, with moderate, slowly varying values of the line flux density, turns to the “active” phase with H2O line bursts (Lekht et al. 1983). The H2O maser generation region is probably located in a rotating gas-and-dust disc (torus) around a protostar (or young star). This is pointed to by VLBI observations showing in some sources maser features arranged in an ellipsoidal structure around a common centre (presumably, the protostellar object - see Downes et al. 1979), as well as by symmetrical character of E2O line profiles of many masers (Lekht et al. 1982). As an excitation mechanism for H2O, collisional pumping in two-temperature medium behind a shock front (with hot heavy particles and cold free electrons or vice versa) is widely accepted (Bolgova et al. 1982, Kylafis and Norman 1986).
On the infrared excess of Alpha Lyrae
Authors: Anandarao B.G. , Vaidya D.B.
Published: June 2019

Recent measurements in far-infrared (12–200 μm) by IRAS (Aumann et al, 1984) and KAO (Harper et al, 1984) have shown evidence of infrared excess in the AO star Alpha Lyrae. This excess in the infrared radiation was interpreted as due to circumstellar dust constituted by grains much larger (≳10 μm) than those of interstellar origin. However, there appears to be a difficulty in interpreting these observations in terms of a single or a combination of several temperatures of dust. We have formulated a simple model to explain the far-infrared data in 12–200 μm region available with IRAS and KAO observations in terms of multiple dust shells of different temperatures. We have shown that dust grains of size ~10 μm can explain the excess emission in the entire region 12–200 μm with temperatures of 130 ± 15 K and 40 ± 5 K. The far-infrared fluxes seem to vary as λ−β with μ = 3.0–3.8, in quite contrast with small sized grains. This work lends further support to the interpretation of far-infrared excess in ∝ Lyrae as emission from circumstellar shell with large (∼10 μm) size grains. Our calculations show, however, that grains of size larger than 10 μm cannot explain the fluxes.
IRAS observations of classical cepheids
Authors: Butler C. J. , Deasy H. P. , Wayman P. A.
Published: June 2019

IRAS observations of sources identified with cepheid variables are used to give estimates of observed mass-loss rates for those stars.
Circumstellar envelopes of OH-IR sources
Authors: Cohen R. J.
Published: June 2019

This article reviews recent radio observations of maser emission from OH, H2O and SiO molecules in the circumstellar envelopes of OH-IR sources. The different radio lines require different conditions for their excitation, and each therefore probes different regions in the circumstellar envelope. For some stars radio interferometer maps of several maser lines are now available, and a consistent picture of the envelope structure is beginning to emerge.