bluuebunny/crossref_metadata_2025 huggingface dataset:
The Environments of the Massive Star Clusters in the Carina Nebula
Authors: Brooks Kate , Rathborne Jill , Burton Michael
Published: June 2019

We have imaged over an extensive field the 3.29-μm emission from the Carina Nebula. This emission arises from polycyclic aromatic hydrocarbons which are excellent tracers of photodissociation regions. The results emphasis the two very different environments of the massive star clusters of the nebula, Trumpler 14 and 16.
New Cluster Candidates in Dwarf Galaxies of the Local Group
Authors: H. Pedreros Mario , Gallart Carme
Published: June 2019

V and I images of the nearby dIrr galaxies Sextans A and Sextans B were searched for star clusters. The candidates were selected, from a sample of non-stellar objects, on the basis of their morphology, their integrated colors and magnitudes. One of the candidates in Sextans A shows a few resolved stars whose location in the color-magnitude diagram indicates the cluster is at least older than 1 Gyr.
Ages and Metallicities of Five Intermediate-Age Star Clusters Projected Towards the Small Magellanic Cloud
Authors: Clariá Juan J. , Piatti Andrés E. , Santos João F. C. , Bica Eduardo , Sarajedini Ata , Geisler Doug
Published: June 2019

Washington CCD photometry of intermediate-age clusters in the Small Magellanic Cloud (SMC) is presented. The cluster age distribution in the SMC suggests formation epochs at 3 and 6 Gyr, respectively. Recent star formation is confined to the central body of the SMC. The chemical evolution of the SMC appears to be best represented by bursty models.
Ultra-compact Dwarf Galaxies: a New Class of Compact Stellar System Discovered in the Fornax Cluster
Authors: Drinkwater Michael , Bekki Kenji , Couch Warrick , Phillipps Steve , Jones Bryn , Gregg Michael
Published: June 2019

We have used the 2dF spectrograph on the Anglo-Australian Telescope to obtain a complete spectroscopic sample of all objects in the magnitude range, 16.5 < bJ < 19.8, regardless of morphology, in an area centred on the Fornax Cluster of galaxies. Among the unresolved targets are five objects which are members of the Fornax Cluster. They are extremely compact stellar systems with scale lengths less than 40 parsecs. These ultra-compact dwarfs are unlike any known type of stellar system, being more compact and significantly less luminous than other compact dwarf galaxies, yet much brighter than any globular cluster.
Resolving Globular Clusters in the Fornax Cluster and Beyond
Authors: J. Grillmair Carl , Holtzman Jon , Elson Rebecca
Published: June 2019

We describe an ongoing program to measure structural parameters for globular clusters with a range of ages in early-type galaxies. Using deep, optimally-dithered HST WFPC2 observations of NGC 3597, NGC 1316, and NGC 1399, we apply a χ2 minimization method to the determination of cluster sizes. The goals include studying the structure spectrum of stellar clusters at birth, and determining the rate at which tidal and evaporative destruction mechanisms operate to alter luminosity functions and specific frequencies to what we see in ellipticals today.
Dynamical Studies of the M87 Globular Cluster System: The Use of the CFHT MOS
Authors: A. Hanes David
Published: June 2019

We describe and celebrate the use of the MOS instrument at the Canada-France-Hawaii Telescope in a multi-object spectroscopic study of the rich globular cluster system (GCS) of the giant elliptical galaxy M87.
Triggering the Formation of Young Clusters
Authors: Elmegreen Bruce G.
Published: June 2019

Star formation is triggered in essentially three ways: (1) the pressures from existing stars collect and squeeze nearby dense gas into gravitationally unstable configurations, (2) random compression from supersonic turbulence makes new clouds and clumps, some of which are gravitationally unstable, and (3) gravitational instabilities in large parts of a galaxy disk make giant new clouds and spiral arms that fragment by the other two processes into a hierarchy of smaller star-forming pieces. Examples of each process are given. Most dense clusters in the solar neighborhood were triggered by external stellar pressures. Most clusters and young stars on larger scales are organized into hierarchical patterns with an age-size correlation, suggestive of turbulence. Beads-on-a-string of star formation in spiral arms and resonance rings indicate gravitational instabilities. The turbulence model explains the mass spectrum of clusters, the correlation between the fraction of star formation in the form of clusters and the star formation rate, found by Larsen & Richtler, and the correlation between the size of the largest cluster and the number of clusters in a galaxy.
Star Clusters in Giant Extragalactic HII Regions
Authors: Zhi-yao Yu
Published: June 2019

In this paper we study the relationship between the star formation efficiency and luminosity of Hα emission, Lyman continuum radiation, and Hβ emission on 35 giant extragalactic HII regions in seven galaxies. Using the observational results we obtain the relationship, and find that the star formation efficiency is correlation with Halpha luminocity, and Lyman continuum luminosity, and Hβ lumonosity, respectively. Key words: external galaxy—giant HII region—star cluster
Evolution of Globular Cluster Systems in Elliptical Galaxies
Authors: Vesperini Enrico
Published: June 2019

We study the evolution of the main properties of globular cluster systems in elliptical galaxies. In particular, we focus our attention on the evolution of the mass function of globular cluster systems (GCMF), on the fraction of surviving clusters and on the ratio of the final to initial total mass in clusters and we explore the dependence of these properties on the structure of the host galaxy and on the initial GCMF. We show that the observed universality of the GCMF parameters in galaxies with different structures can be reconciled with the effects of evolutionary processes and with the significant differences in the efficiency of evolutionary processes in different host galaxies; the final mean masses of globular cluster systems in massive galaxies can be very similar to each other with a small galaxy-to-galaxy dispersion in spite of large differences in the fraction of surviving clusters.
The Fragmentation of Expanding Shells: Cloud Formation Rates and Masses
Authors: Palouš Jan , Wünsch Richard , Ehlerová Soňa
Published: June 2019

The gravitational instability of expanding shells is discussed. Linear and nonlinear terms are included in an analytical solution in the static and homogeneous medium. We discuss the interaction of modes and give the time needed for fragmentation. Masses of individual fragments are also estimated and their formation rates and the initial mass function are derived. Results of simulations are compared to observation.
HST and Keck Observations of a Young Globular Cluster in the Spiral Galaxy NGC 6946
Authors: Larsen Søren S. , P. Brodie Jean , G. Elmegreen Bruce , N. Efremov Yuri , W. Hodge Paul , Richtler Tom
Published: June 2019

Using new (Cycle 9) HST / WFPC2 data, we have studied a peculiar star forming region in the nearby Sc-type spiral NGC 6946. The region has a bubble-like shape and a diameter of about 600 pc. Near the centre is an extremely luminous young globular cluster with MV = −13.2 mag. The cluster has a compact core with a core radius of about 1.3 pc but is surrounded by an extended halo with a power-law luminosity profile similar to that observed for young LMC clusters. From Keck / HIRES high-dispersion spectroscopy we measure a velocity dispersion of 10 km s−1, leading to a dynamical mass estimate of about 1.7 × 106 solar masses. The dynamical mass estimate is comparable to the expectation from population synthesis modelling under the assumption of a Salpeter IMF extending down to 0.1 M⊙.
A New Method for Measuring the Detailed Chemical Composition of Globular Clusters from High-Resolution, Integrated-Light Spectra
Authors: A. Bernstein Rebecca , McWilliam Andrew
Published: June 2019

We are developing a method for measuring the detailed chemical composition and evolutionary history of extragalactic star clusters from high resolution spectra of their integrated light as one would from spectra of individual stars. In this paper, we show high signal-to-noise ratio echelle spectra of the integrated light of two Galactic globular clusters and equivalent-quality spectra of individual stars in those clusters in order to briefly illustrate some subtleties of the analysis method.
Narrow-Angle and Wide-Angle Astrometry via Long Baseline Optical/Infrared Interferometers
Authors: Pan Xiaopei , Kulkarni Shri , Shao Michael , Colavita M. Mark
Published: June 2019

Long baseline optical/infrared interferometers, such as the Mark III Stellar Interferometer1 on Mt. Wilson and the ASEPS-0 Testbed Interferometer2 on Palomar Mountain, California, have good capabilities for narrow-angle and wide-angle astrometry with very high precision. Using the Mark III Interferometer many spectroscopic binaries became “visual” for the first time. The measurement accuracy of angular separation is 0.2 mas, the smallest separation measured between two components is 2 mas, the maximum magnitude difference is 4 mag, and the smallest semimajor axis is 4 mas. Such high angular resolution and dynamic range have been used to determine stellar masses with precision of 2% and differential stellar luminosities to better than 0.05 mag for separations of less than 0.″2. For some binary stars, not only have the systems been resolved, but also the diameter of the primary component has been determined, yielding direct measurements of stellar effective temperature with high accuracy. For parallax determination, the precision is 1 mas or better and is unaffected by interstellar extinction. For wide-angle astrometry with the Mark III interferometer, the observation results yielded average formal 1σ errors for FK5 stars of about 10 mas. Presently a new infrared interferometer, the ASEPS-0 Testbed Interferometer on Palomar Mountain is under construction, and is being optimized to perform high accuracy narrow-angle astrometry using long baseline observations at 2.2 μm, with phase referencing for increased sensitivity. The goal is to demonstrate differential astrometric accuracies of 0.06–0.1 mas3 in order to allow for detection of extra-solar planets in the near future.
Properties of the Hipparcos Catalogue: What Confidence can we have in the Final Data?
Authors: Lindegren L.
Published: June 2019

The foreseen complexity of the the ESA Hipparcos mission led to the establishment of two independent scientific consortia (FAST and NDAC) for the parallel processing of all main mission data. The validation of Hipparcos data through internal and external checks and by interconsortia comparisons is outlined. Examples are given based on preliminary solutions. The various checks indicate that the overall accuracy and reliability of the Hipparcos Catalogue will be extremely high.
The Dynamical Reference Frame
Authors: Standish E. M.
Published: June 2019

Planetary and lunar ephemerides continue to improve in accuracy as they continue to be adjusted to newer and more accurate observational data. An additional improvement will be that of the orientation of the ephemerides; in the future, the ephemerides produced at JPL will be based upon the reference frame of the radio source catalogues. Recent planetary observations have been made directly with respect to the radio reference frame, and these observations have shown a satisfying degree of absolute accuracy and internal consistency; they enable the automatic orientation of the ephemerides onto the radio reference system during the ephemeris adjustment process.
Galactic Kinematics on the Basis of Modern Proper Motion Data
Authors: Miyamoto M.
Published: June 2019

An accumulation of high precision astrometric data in conjunction with high-precision monitoring of the Earth's orientation, motivates “Galactic Astronomy”. As regards local kinematics, all of the three components of both the vorticity and the shear of stars can be completely determined, in addition to the velocity ellipsoid. We can now be released from the constraint of the “axisymmetric” galaxy. The determination of the proper motion of the LMC will be crucial to understanding the global structure and dynamics of the Galaxy with the dark halo and MACHO's motions.
A Small Interferometer in Space for Global Astrometry: The Gaia Concept
Authors: Lindegren L. , Perryman M.A.C.
Published: June 2019

We present a concept for a scanning interferometer for global (wide-angle) astrometry from space. The GAIA concept has been proposed for the European Space Agency's long-term scientific programme. It consists of three Fizeau-type interferometers with 2.5 m baselines, set at large and fixed angles to each other. Complete utilization of the instrument's resolution and sensitivity requires a new type of photon-counting detector, combining very high spatial and temporal resolution. An array of superconducting tunnel junctions (STJ) may ultimately provide this capability. Pending this development we describe a focal-plane configuration for GAIA using existing technology in the form of a modulating grid and CCD detectors. We estimate that 50 million stars brighter than V = 15.5 could be observed on the 10 to 20 microarcsec accuracy level. In addition, high-precision multi-colour, multi-epoch photometry is obtained for all objects.
Ground-Based Astrometry with Short-Focus CCD-Astrographs
Authors: Guseva I.S.
Published: June 2019

The main complication to use CCDs for astrometry is their small linear size. Nevertheless, a wide range of traditional astrometric problems can be solved by use of short-focus astrographs equipped with available CCDs. They are: creation of large astrometric and photometric catalogues, link of optical catalogues to an extragalactic reference frame, observations of the solar system bodies, etc. It can be shown that a telescope with focal length of 1-2 meters, equipped with a single CCD can produce a huge amount of simultaneous positional and photometric observations of high precision. It will be especially effective when the Tycho catalogue will be completed, because the problem of precise reference system in a small field of view (about 1 square degree) will be solved with extremely high accuracy. The majority of stars up to 18-20 magnitude can be observed with such an instrument. The problem of resolving “close” stars arises only for some very dense areas on the sky, such as globular clusters etc. – The results of CCD-observations made at Pulkovo with a small short-focus astrograph (D=100 mm, F=712 mm, FOV=45 × 67 arcmin) in 1993-1994 show that the precision of single observation is not worse than: in right ascension −0.15 to 0.35 arcsec, in declination — 0.10 to 0.25 arcsec (the size of pixel was 18 × 24 μm2), and in magnitude — 0.05 to 0.15 mag in a wide range of magnitudes from the brightest objects to V=16. From a series of 5–10 frames it is possible to obtain positions and magnitudes of a large number (up to 500–600 in one frame) of stars with a precision quite comparable with that of normal astrographs and other “large” telescopes.
Improvement of Star Positions by a New Axial Meridian Circle with Negligible Systematic Errors
Authors: Pinigin G.I. , Shulga A.V. , Fedorov P.N. , Kovalchuk A.N. , Mazhaev A.E. , Petrov A.G. , Protsyuk Yu.I.
Published: June 2019

The Mykolayiv axial meridian circle (AMC) consists of a horisontal telescope with a pentagon prism of ‘CITALL’ in front of the objective of D=180mm and F=2480mm in the meridian, and a fixed aligned vacuum collimator of D=180mm and F=12360mm.

Investigations of the AMC parameters show that: horizontal flexure is negligible and about −0.037″; collimation is stable and can be described by the formula C = C′ + a · t, where t[C] is the temperature, a = 0.026″ and C′ const. The variation of collimator inclination is of the order 0.09″ per 1°C Test observations of FK5 stars show variations of the AMC intrumental system of not more than 0.1″.

A CCD micrometer is being developed. Test observations with a pilot micrometer with a CCD of 288 × 256 pixels have started. It appears that the AMC magnitude limit (with cooling) will be about 14 and the positional accuracy 0.1 arcsec.

Finally, the expected capabilities of the fully automatic Mykolayiv AMC permit its efficient use for extention of the stellar reference frame to fainter magnitudes, for linking the optical/radio reference frames. In particular, for future observations a programme of 12–14m reference stars around extragalactic radio sources is being prepared.
Astrometric Plate Reduction with Orthogonal Functions and Milliarcseconds Accuracy in Deep Proper Motion Surveys
Authors: Ojha Devendra , Bienaymé Olivier
Published: June 2019

We have been doing a sample survey in UBV photometry and proper motions as part of an investigation of galactic structure and evolution. The 3 fields in the direction of galactic anticentre (l = 167°, b = 47°), centre (l = 3°, b = 47°) and antirotation (l = 278°, b = 47°) have been surveyed. The high astrometric quality of the MAMA machine (CAI, Paris) gives access to micronic accuracy (leading to < 2 mas per year) on proper motions with a 35 years time base. The kinematical distribution of F and G–type stars have been probed to distances up to 2.5 kpc above the galactic plane. We have derived the constrain on the structural parameters of the thin and thick disk components of the Galaxy (Ojha et al. 1994abc):

• The scale lengths of the thin and thick disks are found to be 2.6±0.1 and 3.3±0.5 kpc, respectively. The density laws for stars with 3.5≤MV≤5 as a function of distance above the plane follow a single exponential with scale height of ∼ 260 pc (thin disk) and a second exponential with scale height of ∼ 800 pc (thick disk) with a local normalization of 5–6% of the disk.

• The thin disk population was found with (〈 U+W〉, 〈V〉) = (1±4, −14±2) km/s and velocity dispersions (σU+W, σV) = (35±2, 30±1) km/s. The thick disk population was found to have a rotational velocity of Vrot = 177 km/s and velocity dispersions (σU, σV, σW) = (67,51,42) km/s. No dependence with r and z distances was found in the asymmetric drift measurements of the thick disk population.
Confor Program: Determination of Relative Orientation Parameters Between VLBI and FK5 Reference Frames
Authors: Kumkova Li , Tel'nyuk-Adamchuk V.V. , Babenko Yu.G. , Vertypolokh O. Ya.
Published: June 2019

The primary goal of the CONFOR Program (CONnection of Frames in Optics and Radio) is to study the connection between VLBI and traditional optical reference frames as well as to study regional features of the FK5 (Gubanov, Kumkova & Tel'nyuk-Adamchuk, 1990). The main concept of this program is the usage of fixed systems of reference stars in field containing the extragalactic radio sources (ERS) and as a result the creation of a reliable base for astrometric reduction of photographic plates with ERS images. Fulfillment of the Program is embracing several stages.

1. Star lists have been prepared of 2575 both intermediate reference stars and radio stars for meridian observations and about 7 thousand stars of 12-14 mag. for astrographic observations in 238 fields with extragalactic compact radio sources.

2. Observations have been organized of these stars with meridian circles and astrographs in several Eastern observatories (Kyiv, Odesa, Bucharest, Mykolaiv, Kharkiv). The meridian observations are finished in Kyiv and Odesa. Positions of radio stars were determined from Kyiv meridian observations (two epochs: 1984 and 1990).

3. Databases of both the optical and radio interferometric observations have been compiled of radio stars, ERS as well as optical observations of intermediate stars in the fields centered in ERS.

4. Observations were carried out with several astrographs (Kyiv, Bucharest, Abastumany, Tautenburg, Kitab, Sanglok) and positions were determined of 57 ERS.

5. Determination was carried out of the angles of relative orientation between VLBI and FK5 reference frames as well as estimation of regional features of the FK5. For this purpose both collected and original radio source coordinates were used.

This work was supported by grant of Academy of Sciences of former Soviet Union and ISF grant U52000.
The Interseasonal Trend in Photographic Double Stars Observations
Authors: Kiyaeva O.V.
Published: June 2019

Photographic observations obtained in Pulkovo and USNO for four visual double stars (ADS 48, 7251, 11632, 12815) have been investigated.
Large Number Coincidences and the Anthropic Principle in Cosmology
Authors: Carter Brandon
Published: June 2019

Prof. Wheeler has asked me to say something for the record about some ideas that I once suggested (at the Clifford Memorial meeting in Princeton in 1970) and to which Hawking and Collins have referred (Astrophys. J.180, 317, 1973). This concerns a line of thought which I believe to be potentially fertile, but which I did not write up at the time because I felt (as I still feel) that it needs further development. However, it is not inappropriate that this matter should have cropped up again on the present occasion, since it consists basically of a reaction against exaggerated subservience to the ‘Copernican principle’.
Electromagnetic Detectors of Gravitational Waves
Authors: Braginsky V. B. , Grishchuk L. P. , Doroshkievich A. G. , Zel'Dovich Ya. B. , Novikov I. D. , Sazhin M. V.
Published: June 2019

Our group is investigating highfrequency gravitational waves (GW). The most promising approach to detection and laboratory generation of such GW seems to be through the transformation of GW into electromagnetic waves (EMW), and the reverse process: EMW→GW. The effects are small of course.
Scalar Waves in the Exterior of a Schwarzschild Black Hole
Authors: Persides S.
Published: June 2019

Fourier and Laplace transforms are used to study rigorously the properties of a test scalar field PS in the exterior of a Schwarzschild black hole of the mass m. In the Fourier analysis we examine the properties of the solutions of the radial wave equation and the relations of the exterior and interior solutions of the following four cases: (i) ω ≠ 0, m≠0, (ii) ω=0, m≠0, (iii) ω≠0, m=0, (iv) ω=0, m=0.

In the Laplace analysis we show rigorously the following theorem: If ψ(t, r, τ, ϕ) is the field of a point test particle falling into the black hole,
and lim Ψ exists, then lim Ψ = 0. The proof of this theorem is based on the facts that (a)t+2m ln (r − 2m) is finite for the particle even on the horizon, and (b) the behavior of Ψ as t → + ∞ is related to its Laplace transform near the origin of the complex plane.
The Surface Brightness of Our Galaxy and Other Spirals
Authors: van der Kruit P. C.
Published: June 2019

In this review I discuss some aspects of the luminosity distributions in our Galaxy and external spiral galaxies. The major conclusions are the following: (1) the radial scale length of the luminosity distribution in the disk of our Galaxy is 5.0 ± 0.5 kpc, (2) on this basis the Hubble constant needs to be at most 65 ± 10 km s−1 Mpc−1, if our Galaxy and M31 are among the largest spirals, as the Fisher-Tully relation suggests, (3) the probable Hubble type of the Galaxy is SbI–II, (4) the bi-modal distribution function of face-on, central surface brightness μ0 and radial scale length h of spirals shows a preferred value for μ0 of about 22 B-mag arcsec2 and a distribution of h that declines with one e-folding per kpc, (5) the Galaxy is a normal, fairly large Sb galaxy, and (6) galaxies similar to our own in terms of large-scale, nonmorphological properties are NGC 891 and NGC 5033.
Optical and H-Alpha Emission from Unresolved Red Dwarf Stars in the Galaxy
Authors: Szécsényi-Nagy G.
Published: June 2019

Although many of the nearest dim and cool stars (the red dwarfs) were catalogued in the early sixties, the majority of the astronomers did not realize that these objects provide almost nine tenths of all the stars in our Galaxy. In fact 90-95% of the stars in the solar vicinity (r ≤ 25 pc) are main sequence stars, and at least 80% of them are M dwarfs. Outside the main sequence (MS) one can find a few subdwarfs and somewhat more white dwarfs, but the contribution of this latter type is not known precisely. Estimates range between 4% and 8%. The relative frequency of giants and supergiants can not be determined from the census of the local star population because they are not represented in a statistically meaningful number. But investigations of much greater cosmic volumes demonstrate that luminosity classes Ia, Ib, II, III, and IV altogether contribute fewer than 1% of the stellar content of the Galaxy.
Diffuse [CII] Emission in Interstellar Space
Authors: Okuda H. , Shibai H. , Nakagawa T. , Matsuhara H. , Maihara T. , Mizutani K. , Hiromoto N. , Kobayashi Y. , Low F. J. , Nishimura T.
Published: June 2019

An extensive survey of [CII] line emission has been made with a balloon-borne infrared telescope. It has been found that the emission is diffuse and ubiquitously distributed in general interstellar space.
The Infrared Brightness of the Ecliptic Plane
Authors: Reach William T. , Heiles Carl
Published: June 2019

Prerequisite to the determination of the Galactic and Extragalactic contributions to the infrared background is an accurate removal of the zodiacal emission. The all-sky observations by IRAS in 1983 were made with a variety of observing conditions and with higher sensitivity and angular resolution than previous infrared and optical observations of the zodiacal background. These facts alone mandate a better understanding of the optical properties and spatial distribution of interplanetary dust.
Emission from Dust Near High-Latitude Stars
Authors: Murthy J. , Werner M. W. , Walker H. J. , Henry R. C. , Kimble R. A. , Wofford J. B.
Published: June 2019

The spatial distribution of interstellar dust is clearly important in understanding not only galactic dynamics but also the processing of the dust and the interstellar medium in general. Probably the best spectral region for investigating interstellar dust is the infrared (IR), where the cool dust is likely to radiate. Indeed, one of the most prominent features of the IRAS sky is the ubiquitous cirrus emission, thought to be due to interstellar dust heated by the interstellar radiation field (ISRF), seen at 60 and 100 μm (Low 1984). However, it is difficult to use the cirrus to probe the dust distribution, both because we have no depth information and also because the cirrus, due to its low temperatures (~20 K), is a probe of high-density dust regions. A far more sensitive search could be made if the dust were hotter, that is, in the presence of a greater ultraviolet (UV) flux. We have made use of this fact to search for dust in the vicinity of hot, bright stars, where even a small amount of dust will dominate the total emission along that line of sight.
Extinction Maps of Dust Clouds from Surface Photometry
Authors: Seidensticker K. J. , Schmidt-Kaler Th.
Published: June 2019

We present a new method, based on surface photometry, which allows one to make the spatial resolution of extinction maps of dark clouds as fine as necessary. Applying this technique to the Coalsack (l = 302°, b = 0°), we derived an extinction map and the dust mass MD = (62 ± 25) M⊙. The density was found to vary ρ ~ r−0.8, typical for stable clouds.
Galactic Background Radiation in the 78 to 111 EV Band
Authors: Sanders W. T. , Bloch J. J. , Edwards B. C. , Jahoda K. , Juda M. , McCammon D. , Snowden S. L.
Published: June 2019

Galactic background radiation has been observed in the 78-111 eV Be band using 5000 Å beryllium filters in front of a thin-window proportional counter collimated to a 15° full width at half maximum field of view. Be band data have been analyzed from two sounding rocket flights (Bloch et al. 1986, Juda 1988) that viewed seventeen different directions distributed over the northern galactic hemisphere. In Figure 1 the pointing directions of the two flights are indicated on a map from McCammon et al. (1983) of the 130-188 eV B band count rate.
Cosmology and Fluctuations in the Radiation Backgrounds
Authors: Peebles P. J. E.
Published: June 2019

Four topics are discussed. First, measurements of the autocorrelation function of the optical extragalactic sky background check the possibility that there is an appreciable contribution from young galaxies or from stars well outside normal galaxies. Second, large-scale fluctuations in the mass distribution are probed by the anisotropies of the X-ray and 2.7 K backgrounds. Third, scattering by plasma in young galaxies could affect the primeval anisotropy of the 2.7 K background radiation. Fourth, production of the heavy elements is expected to yield background radiation with a characteristic and perhaps detectable angular distribution.
The Microwave Background Radiation
Authors: De Zotti G. , Danese L. , Toffolatti L. , Franceschini A.
Published: June 2019

We review the data on the spectrum and isotropy of the microwave background radiation and the astrophysical processes that may produce spectral distortions and anisotropies. As yet no fully satisfactory explanation has been found for the submillimeter excess observed by Matsumotoet al.(1988). The most precise data at λ > 1 mm disagree with nonrelativistic comptonization models which match the excess. Distortions produced by a very hot intergalactic medium yielding the X-ray background do not fit the submillimeter data. Very special requirements must be met for the interpretation in terms of high-redshift dust emission to work.

Reported anisotropies on scales of several degrees and of tens of arcsec may be produced, at least in part, by discrete sources. Because the best experiments at cm wavelengths are close to the confusion limit, they provide interesting information on the large-scale distribution of radio sources.
The Distribution of Separations of DMSA Hipparcos Catalogue
Authors: Ling J.F. , Magdalena P. , Prieto C.
Published: June 2019

We have constructed volume-limited samples of wide binaries in the Hipparcos Catalogue Double and Multiple Systems Annex (DMSA, Section C), out to distances of 100 pc and 200 pc. We study the distribution of linear separations for these samples of binaries. We find that they closely follow Öpik’s distribution in the interval of separations between about 10 and 800 AU (for the 100 pc sample), and between 15 and 1400 AU (for the 200 pc sample)
Molecular Gas Kinematics and High-Mass Star Formation in the Spiral Arms of the Milky Way
Authors: Luna A. , Carrasco L. , Ortega L. , Bronfman L. , Yam O.
Published: June 2019

We study the kinematic of the molecular gas using observations of the rotational line 12CO(J=1→0), and also the star formation traced by Ultra-Compact HII regions in the IV galactic quadrant (270° ≤ l ≤ 360°). Our results show that there is a connection between 1) high-mass star formation in the spiral arms of the Milky Way, 2) molecular gas of high column density, and 3) the large-scale rigid-body-like motion of the gas. The large-scale rigid-body-like motions observed in the arms imply that there is less angular momentum to dissipate in the formation processes of stellar systems. We show a multiple stellar system under study, embedded in its parent molecular cloud in the Carina arm region.
The Modified Restricted Three Body Problems
Authors: Jiang Ing-Guey , Yeh Li-Chin
Published: June 2019

The restricted three body problem is well-known and very important for the dynamics of binary and multiple stars and also planetary systems. We extend the classical version of this problem to the situation that there are some external forces from the belt. We find that both the equilibrium points and solution curves become quite different from the classical case. We also determine the values of Lyapunov exponent for some important orbits.
Planets in Multiple-Star Systems: Properties and Detections
Authors: Udry S. , Eggenberger A. , Mayor M. , Mazeh T. , Zucker S.
Published: June 2019

Orbital properties of extra-solar planets are briefly recalled and compared with equivalent features of stellar binaries. Similarities and differences are discussed. Among the more than 115 extra-solar planets discovered to date, 19 are orbiting a component of a binary system. We discuss the properties of this subsample and compare them with the equivalent characteristics of planets around single stars. Differences in the mass-period-eccentricity distributions are observed: exoplanets with m2 sin i > 2 MJup and P≤ 40-100 days are in binaries and present low eccentricities. In the context of the migration scenario, these characteristics are tentatively explained in the light of recent simulations of planet-disk interactions showing an increased accretion and migration rates of planets in case an additional perturbing close stellar companion is present in the system. Finally, different observational approaches to find planets in long-period spectroscopic binaries aiming to improve the still poor available statistics are presented. An important result is the detection of a planetary companion in the HD 41004 triple system.
The Binarity Status of Stars with and without Planets Probed with VLT/NACO
Authors: Udry S. , Eggenberger A. , Beuzit J.-L. , Lagrange A.-M. , Mayor M. , Chauvin G.
Published: June 2019

The properties of planets orbiting a component of a binary or multiple-star system appear different from the ones of planets orbiting isolated stars (Udry et al. 2004). The effect of binarity has, however, still to be better characterized and quantified. In this contribution, we describe a VLT/NACO adaptive optics survey aimed at pointing out the potential effect of stellar duplicity on planet formation and evolution, by comparing the faint-companion statistics of similarly selected subsamples of stars with and without planets. The statistical results of the survey will allow us to possiblydiscriminate between the proposed models of planetary formation (accretion or disk instability), some of them predicting different influences of stellar duplicity. Preliminary results are already very interesting: 20 ± 7% of the “single” stars present companions within ~10″, whereas only 3 ± 3% equivalent companions are found close to stars hosting planets.
Planets in Double Stars: The ϒ Cephei System
Authors: Dvorak R. , Pilat-Lohinger E. , Bois E. , Funk B. , Freistetter F. , Kiseleva-Eggleton L.
Published: June 2019

Up to now we have evidence for some 15 planets moving in double stars. They are all of the so-called S-type, which means that they are orbiting one of the primaries. Only two of the binaries have separations in the order of the distances where the planets in our Solar system orbit the Sun, namely Gliese 86 and ϒ Cep. In this study we investigate the stability of the recently discovered planet in ϒ Cep with respect to the orbital parameters of the binary and of the planet. Additionally we check the region inside and outside the planet’s orbit (a = 2.1 AU). Even when the mass of an additional planet in 1 AU would be in the order of that of Jupiter, the discovered planet would be in a stable orbit.
Spectroscopy, Photometry and Micro-Arcsec Astrometry of Binaries with The Gaia Space Mission and with the Rave Experiment
Authors: Zwitter Tomaž , Munari Ulisse
Published: June 2019

The GAIA astrometric mission of ESA will be very efficient in discovering binary and multiple stars with any orbital period, from minutes to millions of years. The main parameters of the revised mission design are presented. Next we estimate the fraction of binary stars discovered by means of astrometry, photometry and on-board spectroscopy. Finally we summarize observations that confirm the ability to measure physical parameters like masses, radii and spectroscopic distance from GAIA data alone. GAIA will fly only in 2010, but the radial velocity experiment (RAVE) has started this year. We show that its spectroscopic observations have the capacity to discover a large fraction of so far unknown binary systems.
Radio Supernovae
Authors: Sramek Richard A. , Weiler Kurt W. , Panagia Nino
Published: June 2019

Detailed, multi-frequency radio observations of supernovae have shown that the radio emission can be understood as a blastwave interacting with a structured circumstellar medium (CSM) and modeling of the radio light curves allows estimation of the physical conditions in this medium. CSM structures, properties of the presupernova system, and the evolution of the system in the last stages before explosion can then be derived.
Low Frequency Radio and X-ray Properties of Core-Collapse Supernovae
Authors: Ray A. , Chandra P. , Sutaria F. , Bhatnagar S.
Published: June 2019

Radio and X-ray studies of young supernovae probe the interaction between the supernova shock waves and the surrounding medium and give clues to the nature and past of the progenitor star. Here we discuss the early emission from type Ic SN 2002ap and argue that repeated Compton boosting of optical photons by hot electrons presents the most natural explanation of the prompt X-ray emission. We describe the radio spectrum of another type Ic SN 2003dh (GRB030329) obtained with combined GMRT and VLA data. We report on the low frequency radio monitoring of SN 1995N and our objectives of distinguishing between competing models of X-ray emission from this SN and the nature of its progenitor by X-ray spectroscopy. Radio studies on SN 2001gd, SN 2001ig and SN 2002hh are mentioned.
Observational Properties of Type II Plateau Supernovae
Authors: Pastorello A. , Ramina M. , Zampieri L. , Navasardyan H. , Salvo M. , Fiaschi M.
Published: June 2019

We present spectroscopic and photometric data of a sample of Type II plateau Supernovae, covering a wide range of properties from the 56Ni rich, high luminosity events (e.g. SN 1992am) to the low-luminosity, 56Ni poor SNe (e.g. SN 1997D). We provide an observational framework to analyze correlations among observational data, physical parameters and progenitors characteristics of Type II supernovae.
Pre-Supernova Evolution of Rotating Massive Stars
Authors: Hirschi Raphael , Meynet Georges , Maeder André , Goriely Stéphane
Published: June 2019

The Geneva evolutionary code has been modified to study the advanced stages (Ne, O, Si burnings) of rotating massive stars. Here we present the results of four 20 M⊙ stars at solar metallicity with initial rotational velocities, vini, of 0, 100, 200 and 300 km/s in order to show the crucial role of rotation in stellar evolution. As already known, rotation increases mass loss and core masses [4]. A fast rotating 20 M⊙ star has the same central evolution as a non-rotating 26 M⊙. Rotation also increases strongly net total metal yields. Furthermore, rotation changes the SN type so that more SNIb are predicted (see [5] and [6]). Finally, SN1987A-like supernovae progenitor colors can be explained in a single rotating star scenario.
Core-Collapse Supernovae at the Threshold
Authors: Janka H.-Th. , Buras R. , Kifonidis K. , Marek A. , Rampp M.
Published: June 2019

Recent progress in modeling core-collapse supernovae is summarized and set in perspective. Two-dimensional simulations with state-of-the-art treatment of neutrino transport still fail to produce powerful explosions, but evidence is presented that they are very close to a success.
On the Stability of Thermonuclear Burning Fronts in Type Ia Supernovae
Authors: Röpke F.K. , Hillebrandt W.
Published: June 2019

The propagation of cellularly stabilized thermonuclear flames is investigated by means of numerical simulations. In Type Ia supernova explosions the corresponding burning regime establishes at scales below the Gibson length. The cellular flame stabilization - which is a result of an interplay between the Landau-Darrieus instability and a nonlinear stabilization mechanism - is studied for the case of propagation into quiescent fuel as well as interaction with vortical fuel flows. Our simulations indicate that in thermonuclear supernova explosions stable cellular flames develop around the Gibson scale and that a deflagration-to-detonation transition is unlikely to be triggered from flame evolution effects here.
Supernova Statistics
Authors: Cappellaro Enrico , Barbon Roberto , Turatto Massimo
Published: June 2019

The statistics of SN discoveries is used to reveal selection biases of past and current SN searches and to gain insight on the progenitor scenarios for the different SN types. We also report estimates of the SN rate per unit mass in galaxies of different types and on the first attempts to study the evolution of the supernova rate with redshift.
Long GRBs and Supernovae from Collapsars
Authors: MacFadyen A.I.
Published: June 2019

Long duration gamma-ray bursts are associated with the death of massive stars as earlier observations and theoretical arguments had suggested. Supernova 2003dh observed with GRB030329 confirms this picture. Current progress in developing numerical special relativistic hydrodynamics codes with adaptive mesh refinement is allowing for high-resolution simulations of relativistic flow relevant for simulations of GRBs.
Gamma-ray Bursts
Authors: Castro-Tirado Alberto J.
Published: June 2019

Since their discovery in 1967 Gamma-ray bursts (GRBs) have been puzzling to astrophysicists. With the advent of a new generation of X–ray satellites in the late 90’s, it was possible to carry out deep multi-wavelength observations of the counterparts associated with the long duration GRBs class just within a few hours of occurrence, thanks to the observation of the fading X-ray emission that follows the more energetic gamma-ray photons once the GRB event has ended. The fact that this emission (the afterglow) extends at longer wavelengths, led to the discovery of optical/IR/radio counterparts in 1997-2003, greatly improving our understanding of these sources. The classical, long duration GRBs, have been observed to originate at cosmological distances in a range of redshifts with 0.1685 ≤ z ≤ 4.50 implying energy releases of ~ 1051 ergs. The recent results on GRB 021004 and GRB 030329 confirm that the central engines that power these extraordinary events are due to be collapse of massive stars rather than the merging of compact objects as previously also suggested. Short GRBs still remain a mystery as no counterparts have been detected so far.
Brane Universes Tested by Supernovae
Authors: Godłewski Włodzimierz , Szydłowski Marek
Published: June 2019

We discuss observational constrains coming from supernovae Ia imposed on the behavior of the Randall-Sundrum models. It is interesting that brane models predict brighter galaxies for such redshifts which is in agreement with the measurement of the z = 1.7 supernova. We also demonstrate that the fit to supernovae data can also be obtained, if we admit the “super-negative” dark energy p = − (4/3) ϱ on the brane, where the dark energy in a way mimics the influence of the cosmological constant.
Sundials in London - Linking architecture and astronomy
Authors: Kibble Bob
Published: June 2019

Following the inclusion of Astronomy in the revised National Science Curriculum for England and Wales the Association for Astronomy Education, AAE, embarked on a programme of in-service training workshops for teachers to help them to understand the new ideas and deliver the new curriculum. Teacher confidence and knowledge has been the greatest challenge to establishing astronomy in school curricula. As part of the the AAE team I gave presentations on a host of activities including simple cut and paste sundials for pupil projects. We are now seven years on from the revised Science Curriculum and my interest in sundials has stepped up a gear. I have developed an interest in real dials, both studying existing dials and making dials for the homes of friends and families and for schools. This presentation, which has as its focus, the sundial as an architectural feature, uses slides I have taken of some of the dials to be seen in the central London area including some of my own.
University Education in the Next Century
Authors: McNally Derek
Published: June 2019

There is no doubt that the science of astronomy is now in an exhilarating state. We are in the era of the 10 m optical telescope. Radio astronomy rivals optical astronomy in both positional precision and sensitivity. Observation from space has opened access to a wide range of frequencies in the electromagnetic spectrum. The spectacular achievements of the Hubble Space Telescope underline the success story of space astronomy. At all wavelengths, detector technology has made striking advances in sensitivity and, coupled with cheap, sophisticated and powerful computers, raw data can be transformed into useful scientific data with breathtaking speed. One has only to add up the number of papers published in the three major astronomical journals to realise that one must read 100 journal pages a day (every day) to keep up with the literature in these three journals alone. Astronomy at the close of the 20th century is indeed exhilarating.
The Planetarium—a place to learn
Authors: Iwaniszewska C.
Published: June 2019

I would like to dedicate this paper to the memory of professor Edith A. Müller, deceased at the age of 77 a year ago, on July 24, 1995, until her retirement working at Geneva Observatory. She had been at the very beginnings of our IAU Commission 46 in the late sixties, she had been its President in 1970 when we all met during the General Assembly in Brighton, she always took great interest in further educational developments. I am personally grateful to her for much helpful advice during Commission 46 meetings at the General Assembly of 1985 in New Delhi. Wonderful teacher and organizer, she was also an extremely kind lady.
The Role of Science Centres as Aids for Astronomical Education
Authors: Fierro J.
Published: June 2019

Education is training, part of which is being able to handle information. At meetings such as this, one learns new ways to teach and to adapt ideas to one's culture in a way they can have a greater influence on the lay person (Pasachoff and Percy, 1990; Percy, 1996). A reason to promote science popularization is to give people a chance to experience the pleasure of understanding.
Project ASTRO: A Successful Model for Astronomer/Teacher Partnerships
Authors: Bennett M. , Fraknoi A. , Richter J.
Published: June 2019

Project ASTRO is designed to improve astronomy education and science literacy in grades 4-9 by creating effective working partnerships between teachers/youth leaders and astronomers (both professional and amateur). Key elements of the program include:

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training the teachers/youth leaders and astronomers together in inquiry-based “hands-on, minds-on” learning activities

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encouraging an active working partnership between the astronomer and the teacher/youth leader

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encouraging multiple visits by the astronomer to the classroom or youth group meetings.
Coping with a New Curriculum: The Evolving Schools Program at the Carter Observatory, New Zealand
Authors: Leather K. , Andrews F. , Hall R. , Orchiston W.
Published: June 2019

Carter Observatory is the National Observatory of New Zealand and was opened in 1941. For more than ten years the Observatory has maintained an active education program for visiting school groups (see Andrews, 1991), and education now forms one of its four functions. The others relate to astronomical research; public astronomy; and the preservation of New Zealands astronomical heritage (see Orchiston and Dodd, 1995).

Since the acquisition of a small Zeiss planetarium and associated visitor centre in 1992, the public astronomy and education programs at the Carter Observatory have witnessed a major expansion (see Orchiston, 1995; Orchiston and Dodd, 1996). A significant contributing factor was the introduction by the government of a new science curriculum into New Zealand schools in 1995 (Science in the New Zealand Curriculum, 1995). “Making Sense of Planet Earth and Beyond” comprises one quarter of this curriculum, and the “Beyond” component is astronomy.