bluuebunny/crossref_metadata_2025 huggingface dataset:
Toward Solving the Mysteries of the Exotic Eclipsing Binary є Aurigae: Two Thousand years of Observations and Future Possibilities
Authors: Guinan Edward F. , DeWarf Laurence E.
Published: July 2016

The long period (P = 27.1 yr) eclipsing binary є Aurigae (F0 Ia + disk?) is truly an exotic star. It has a deep eclipse that lasts for nearly two years. This eclipse arises as a huge, cool, flattened disk transits the F-supergiant star. Modeling of the eclipse observations shows that the disk has a radius as large as ∼ 9 AU. Infrared observations indicate that the disk is cool with temperatures between 450 − 1000 K. Yet there is evidence of significant FUV emission also originating from the disk.

At present, our knowledge of the mass and luminosity of the binary is still too uncertain to distinguish between two competing models of the system. The high mass model assumes that the F0 supergiant is a normal Pop. I star with a mass appropriate for its spectral type of M ∽ 15 M⊙. It is accompanied by a flattened disk companion with a slightly smaller mass. In this model the disk object is a young proto-stellar or protoplanetary disk. In the low mass model, the F0I star is assumed to be a bloated, old, solar mass post-AGB star. In this case the secondary object is an accretion disk with a mass of 4-5 M⊙. This disk is a remnant of postmain sequence mass transfer that occurred within the last few thousand years. In both models there are still problems explaining the object (or objects) at the center of the disk. Candidates include a pre-main sequence object, a black hole, or a close binary.

In this paper we review the properties of ϵ Aurigae and discuss the advances in our understanding of this enigmatic star from observations made since its last eclipse in 1982-1984. With new technologies and advanced instrumentation it is possible that the physical properties of this puzzling binary star will be found during the next decade. Once found, then ϵ Aurigae and its eclipses can be used as a laboratory for exploring (and testing) current astrophysical concepts and theories that include rapid stages of stellar evolution, binary star evolution, and the structure and dynamics of large disks.
Irradiation Effects in Compact Binaries
Authors: Beer Martin E. , Podsiadlowski Philipp
Published: July 2016

Irradiation of the secondaries in close binary systems affects their appearance and can drastically change their internal structure and hence long-term evolution. In this paper we review the main effects of external irradiation in close binaries with compact primaries, such as the distortion of the shape of the secondary and the conditions for the occurrence of outer critical configurations, and apply these to normal X-ray binaries, including systems such as HZ Her/Her X-l, Vela X-l and black-hole binaries during outburst (e.g. Nova Sco). Particular emphasis will be given to the role of circulation driven by the external heating and the radiative surface stress. We have developed a three-dimensional fluid dynamics code for modelling these effects. We present initial results of self-consistent calculations for the circulation in irradiated systems and show how the inclusion of these effects is vital to the understanding and interpretation of any system where external irradiation of the secondary is significant.
A Protoplanetary Disk in V645 Cyg As Seen with H2O and Methanol Masers
Authors: Val’tts I.E. , Slysh V.I. , Voronkov M.A. , Migenes V.
Published: July 2016

Radio images of maser spots in the infrared source RAFGL 2789, connected with the young stellar object V645 Cyg, have been obtained as a result of radio interferometric observations of the H2O maser at 22 GHz and the methanol maser at 6.7 GHz, with the VLBI arrays VLBA and EVN. It is shown that the position of the masers coincides with the optical object within 02. The maser spots are located along the line North-South, and their position and radial velocity can be described by a model of a Keplerian disk with a maximum radius of 40 AU for the H2O maser and 800 AU for the methanol maser. The H2O and methanol maser spots have not been resolved, and lower limits of the brightness temperature are 2 × 1013 K and 1.4 × 109 k respectively. A model of the maser is suggested in which the maser emission is generated in extended water and methanol envelopes of icy planets orbiting the young star.
The Initial–Final Mass Relation for Close Low–Intermediate-Mass Binaries (Non-conservative Case)
Authors: Chen Xuefei , Han Zhanwen
Published: July 2016

Employing Eggleton’s stellar evolution code, we carry out 150 runs of non-conservative Population I binary evolution calculations with the initial primary mass between 1 and 8 M⊙, the initial mass ratio q = M1/M2 between 1.1 and 4 and the onset of Roche lobe overflow (RLOF) at the early, middle or late Hertzsprung gap. We assume that 50 per cent of the mass lost from the primary during the RLOF is accreted on to the secondary, the other 50 per cent is lost from the system, carrying away the same specific angular momentum as the centre of mass of the primary. We find that the remnant mass depends on when the RLOF begins in the Hertzsprung-gap and the dependency increases with the primary mass. The remnant mass, however, does not depend much on the initial mass ratio, as compared to conservative cases. For qi = 1.1, we fit a formula for the remnant mass as a function of the initial mass M1i of the primary and the radius of the primary at the onset of RLOF with an error less than 2.61 per cent.
The Low State Temperature Distribution and First Chemical Abundances of White Dwarfs in Polars
Authors: Sion Edward M.
Published: July 2016

During the low optical brightness states of AM Her systems (polars) when accretion has declined to a very low value, the underlying magnetic white dwarf photosphere can be modelled without the complication of thermal bremstrahlung and cyclotron emission from the luminous accretion column. The far ultraviolet spectra can be modelled with high gravity Solar composition photospheres. In this way, I present new temperatures and the first chemical abundance estimates for the white dwarfs in three selected polars from the IUE NEWSIPS archive. For the white dwarf in V834 Cen with Teff = 16,000K, Si/H = 0.1 Solar, C/H = 0.5 Solar, for BY Cam, Teff = 17,000K, Si/H = 0.1, C/H = 5 Solar and for RX J1313-32, Teff = 22,000K, Si/H = 0.1 Solar, C/H = 0.1 Solar. The temperature distribution of 24 white dwarfs in polars with known temperatures above and below the period gap is compared with the distribution of the white dwarf temperatures in dwarf novae during quiescence. In both cases, the magnetic white dwarfs in polars are significantly cooler than the non-magnetics. For all CV white dwarfs, magnetic and non-magnetic with Teff < 12,500K, 91% of the objects (10 out of 11) are magnetics in polars. This suggests that long term accretion heating and cooling of white dwarfs in polars differs from the effects of long term accretion in non-magnetic disk accretors.
VY Sculptoris stars are Magnetic Cataclysmic Variables
Authors: Lasota Jean-Pierre , Hameury Jean-Marie
Published: July 2016

We show that VY Scl stars must be magnetized in order to account for the absence of outbursts during their low and intermediate states. Absence of outbursts during low states requires only rather low magnetic moments but in systems in which the drops and rises of luminosity are slower than it takes for the accretion disc to adjust viscously to the variation in mass-transfer rate preventing outbursts require magnetic moments of Intermediate Polars. We discuss some evolutionary aspects of this conclusion.
The XMM-Newton-MSSL survey of Polars
Authors: Ramsay Gavin , Cropper Mark
Published: July 2016

The XMM-Newton-MSSL survey of polars is a snapshot survey of nearly 40 polars. We present the initial results, with an emphasis on the energy balance in these systems and the number of systems which were observed in a low accretion state. In contrast to the ROSAT results we find that the vast majority of polars show no ‘soft X-ray excess’. We find that half of our sample were observed in low or off accretion states. We find no evidence that these systems were biased towards certain orbital periods.
High Speed Keck Spectroscopy of Flickering in AM Her
Authors: Skidmore Warren , Gomer Richard , Horne Keith , O’Brien Kieran , Oke B. , Pearson K. J.
Published: July 2016

We present fast (72ms) spectroscopy of AM Her obtained at an intermediate brightness state just before a rise to a high state. Interesting features in the line behaviour of AM Her are noted and the variability spectrum is presented and compared to that of SS Cyg.
Discovery of 15-second Oscillations in HST observations of W Sge following the 2001 Outburst
Authors: Araujo-Betancor S. , Knigge C. , Marsh T. R. , Hynes R. I. , Steeghs D. , Long K. S.
Published: July 2016

We report the discovery of 15 s oscillations in HST/STIS far-UV spectroscopic observations of WZ Sge in decline, one month after the start of its 2001 outburst. We discuss the implications of this finding for both the magnetic and pulsating white dwarf models that have been proposed to account for the 28 s oscillations.
XMM observations of the long period polar V1309 Ori
Authors: Schwarz Robert , Reinsch Klaus , Burwitz Vadim
Published: July 2016

We present the first full-orbit X-ray light curve of the remarkable eclipsing magnetic Cataclysmic Variable V1309 Ori obtained with XMM-Newton. The photometric behaviour and the extreme soft-to-hard flux ratio of the bright phase emission suggest that accretion occurs entirely via dense blobs.
Polar Motion and Earth Rotation from Lageos Laser Ranging
Authors: Tapley B. D.
Published: July 2016

Laser ranging collected during the period from May 7 1976 through May 1981, has been used to determine polar motion and length of day (LOD) variations. Independent short-arc solutions of five days in length are used to obtain the polar motion and LOD results. The solutions obtained with these approaches are compared with BIH and Doppler solutions. With the Vondrak smoothing parameter of 10−7, the weighted RMS of the raw minus smoothed results is 0010 in x, 0008 in y and 0.28 msec in LOD. Finally, the results obtained during the MERIT campaign, an international polar motion intercomparison experiment, using both “quick-look” and the final processed laser range data are discussed.
Comparison of Polar Motion Data from the 1980 Project Merit Short Campaign
Authors: Mueller Ivan I. , Rajal B. S. , Zhu Y. S.
Published: July 2016

Polar motion coordinates obtained during the Merit short campaign by various techniques, as well as their variations, have been compared directly and through a smoothing procedure. In the direct comparison, values at selected dates were differenced in all combinations and the rms values computed. Through the smoothing procedure the amplitudes of the annual and Chandler motions as well as the centers of the polhodes were estimated and compared with predicted values based on the previous six years of polar motion data. The results are somewhat inconclusive, mainly due to the shortness of the campaign and the (practically) real time data reduction techniques. To resolve the issue of possible systematic differences, the proposed MERIT main campaign seems an absolute necessity.
Planetary and Earth Figure Perturbations in the Librations of the Moon
Authors: Eckhardt Donald H.
Published: July 2016

Comparisons of numeric, semi-analytic and analytic lunar libration models indicate that the planetary and Earth figure perturbations used to supplement the semi-analytic and analytic models are inadequate. Using the ELP-2000 of Chapront and Chapront-Touzé, an improved solution of these perturbations is developed. For the libration in longitude there are numerous terms with periods near that of the free libration; their amplitudes remain ill-defined.
Online Bibliographic Resources in Astronomy and Astrophysics
Authors: Rey-Watson Joyce
Published: July 2016

Online searches may be performed in astronomy and astrophysics either by OBJECT or by SUBJECT. Until recently, although object searches could be performed on a variety of databases in the physical sciences, results were poor and incomplete. Only if an object were mentioned by name in the title or abstract could one hope for any hits at all. The greatest blessing to befall the astronomical community was the advent of SIMBAD (Sets of Identifications, Measurements and Bibliography for Astronomical Data), a database in which searches are conducted by OBJECT only. It is produced and accessible from the Centre de Donnees de Strasbourg (CDS), Observatoire Astronomique, and is the result of many years of arduous work by a few dedicated astronomers and computer scientists. It is comprised of the merging of two earlier databases, the Catalog of Stellar Identifications (CSI) and the Bibliographical Star Index (BSI)
Basic Principles of Computer Networking
Authors: Russo G.
Published: July 2016

The basic principles of networks, the terminology used and the features offered by the most commonly used systems are summarized.
Storing Sky Surveys at NOAO
Authors: Van Atta Cathaleen
Published: July 2016

At NOAO/Tucson the various sky surveys are not kept in or kept by the Library. Instead, the person who is responsible for their acquisition, care, handling and preservation, is someone whose area of expertise is scientific photography and instrumentation, and he has given me the information that follows.

At NOAO we have a very complete set of the sky surveys. In Tucson we have one set of the Palomar survey on print and one on glass, the ESO/SRC southern atlas, red and blue, on glass and film, the SRC infrared atlas on film, the SRC equatorial atlas on glass, the ESO quick blue survey on glass, and original KPNO telescope plates on glass. At the observatory on Kitt Peak there are two sets of the Palomar survey on print. Basically, all of these can be divided by format into three kinds: paper print, film, and glass. I will tell briefly what we do with each.
Handling of Microfiche
Authors: Gómez M. E.
Published: July 2016

The microficher received at the Library E.S.O. - La Silla, come from different sources: old journals out of print, articles in current journals which often include microfiche for long tables, catalogs and figures not suitable for normal printing, and larger catalogues of data (IUE, IRAS, etc.). These microfiche, coming either in journals or being a publication themselves, are ordered in the same way:

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Every microfiche is assigned a running number.

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Three cards are typed: the main one being by author, the second one by title of the article, and the third one by title of the journal. In addition, the running number that identifies the microfiche is typed on the upper right corner of each card. The total amount of microfiche that make up the article or publication is given at the lower center of each card.

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The cards are kept in a special catalogue cabinet labeled Microfiche., in strict alphabetical order, where the cards by author, title, and publication are mixed together.

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The microfiche themselves are kept in a plastic tray with fiche separators and index dividers with insertable label holders. These label holders are placed at an interval of every five fiche separators. The holders display the running numbers of the microfiche.

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In addition, every fiche separator carries on its front side an adhesive label which contains the same information as that found on the main card.
Observatory Publications
Authors: Gantz Joan
Published: July 2016

My library dates back to 1904, shortly after Dr. George Ellery Hale came west from Yerkes Observatory to the sleepy little town of Pasadena, California to start the Mount Wilson Solar Observatory. The classification system used in this new library was published for the International Council by the Royal Society of London. Over time the librarians managed to acquire many complete runs of observatory publications from all over the world, and they were arranged alphabetically according to the place where they were published. University publications have been included in this collection as well.
The ESO Archive Project
Authors: Ochsenbein François
Published: July 2016

Following the Archiving Policy recently defined, observations made at the ESO telescopes will be archived, starting with the large instruments. The Fits format is used extensively for the description of each stored observation, and a Catalogue is built up for retrieval purposes; this Catalogue will be accessible from ESO at Garching and via the existing networks. During the archiving process, special care is taken to homogenize the names of the targets observed.
The Relighting of Kalispell, Montana
Authors: Westpfahl David
Published: July 2016

Kalispell, Montana, a city of about 20,000 near the Canadian border, has completed major relighting. Aging mercury vapor lamps along U.S. routes #2 and #93 nave been replaced with low pressure sodium (LPS) fixtures. The downtown also has LPS plus turn-of-the-century style cast iron lampposts with low wattage fluorescent lamps, which provide white light on storefronts and curbside parking. The Chamber of Commerce helped with the purchase of these fixtures, which are lit from dusk to midnight and, in the winter, from 6:00 A.M. until sunrise. Most other areas of Kalispell are lit with high pressure sodium in full cut-off fixtures. City and county officials have calculated that the payback time for the LPS relighting was 40 months.
In Defense of Space Art: The Role of the Artist in Space Exploration
Authors: Malina Roger F.
Published: July 2016

Artworks will be built in space as the frequency and range of space missions increase. Artists have proposed artworks to be installed in space and have worked with space agencies to begin planning for such projects; a few space art projects have been completed. It is argued that artworks should be reviewed with the same constraints as all other space artifacts. It is unlikely that artworks will ever pose the kind of environmental threat that already exists from scientific, commercial and military activities; the cultural value of creating some space art balances the associated costs and risks. Artworks visible to global audiences can be conceived and have been proposed; it is these proposals that have concerned astronomers. Public space art should be subject to a process of public scrutiny similar to that of earth-based public art works. Most space art will involve interdisciplinary teams of artists, scientists and engineers; these projects offer the possibility of artists providing novel ideas and approaches that will be of interest in other applications. Artists in the past have played crucial roles in promoting space exploration, in literature, film and the plastic arts. They have also explored the negative aspects and risks. In the future it is inevitable and desirable that artmaking be included in planned space activities.
The role of radiation pressure in LBV atmospheres
Authors: Appenzeller I.
Published: July 2016

As LBVs have luminosities close to their Eddington limits, their structure is profoundly influenced by radiation pressure. Radiation pressure effects probably cause the highly extended atmospheres and the extreme mass loss observed during the maximum states of the S Dor variables. An opacity-related instability of the radiative acceleration combined with a delayed thermal readjustement of the sub-atmospheric layers possibly explains the large-amplitude radius variations of these objects.
The ionization and thermal balance in P Cygni’s wind revisited
Authors: Johnson D.R.H. , Drew J.E.
Published: July 2016

The statistical and thermal equilibrium of P Cygni’s wind as a function of radius is investigated using the model of Drew (1985) with an improved treatment of hydrogen. Provisional calculated hydrogen and helium line fluxes are compared with observation. The wind temperature is found to be cooler than observation implies, and a further heating source is tentatively identified.
Variable flux of P Cygni in continuum and spectral lines
Authors: Kolka Indrek
Published: July 2016

Recently, cyclic variations have been discovered both photometrically in the continuum flux of P Cygni (Percy et al. 1988) and by position measurements of different components in spectral lines of this star (Kolka 1983, Markova, Kolka 1985, Lamers et al. 1985). Additionally, more stochastic polarimetric (Haves 1985) and radio flux (van den Oord et al. 1985) variations were discovered, too. It has recurrently been stressed that simultaneous multiwavelength observations are badly needed. Fortunately, we had a possibility to complement our own observational data from 1982 with some additional data of the same year from astronomical literature to compare the B, V-filter flux with the behavior of spectral lines having two flux estimates for this period, too.
Eta Carinae: UV constraints on possible models. The close binary hypothesis
Authors: Baratta Giovanni Battista , Viotti Roberto
Published: July 2016

η Car is one of the brightest stars in our Galaxy. For its luminosity, huge mass loss, large variability can be considered as an ideal laboratory to study the LBV phenomenon, and to give constraints on possible models of LBVs. We propose that η Car is a – possibly binary –F-type hypergiantwhose wind isheated by dissipation of mechanical energy.
LSS 4005 and NaSt1, two Galactic Ofpe/WN or B[e] objects
Authors: van der Hucht K.A. , Williams P.M. , Genderen A.M. van , Mulder P. , Zealey W.J.
Published: July 2016

Optical and IR spectroscopy of two galactic objects previously considered to be extreme late WN stars (van der Hucht et al., 1984), LSS4005 (formerly tentatively listed as WR85a) and NaStl (WR122), show both objects not to be WR stars, but Ofpe/WN- or B[e]-like objects.
Triple Galaxies and a Hidden Mass Problem
Authors: Karachentsev I.D. , Karachentseva V.E. , Lebedev V.S.
Published: July 2016

We consider a homogeneous sample of 84 triple systems of galaxies with components brighter than m = 15.7, located in the northern sky and satisfying an isolation criterion with respect to neighboring galaxies in projection. The distributions of basic dynamical parameters for triplets have median values as follows: radial velocity dispersion 133 km/s, mean harmonic radius 63 kpc, absolute magnitude of galaxies MB = —20.38, crossing time τ = 0.04 H−1. For different ways of estimation the median mass-to-luminosity ratio is (20 – 30)f⊙.

A comparison of the last value with the ones for single and binary galaxies shows the presence of a virial mass excess for triplets by a factor 4. The mass-to-luminosity ratio is practically uncorrelated with linear size of triplets or with morphological types of their components.

We note that a significant part of the virial excess may be explained by the presence of nonisolated triple configurations in the sample, which are produced by debris of more populous groups of galaxies.
Merging Galaxies and Black Hole Ejections
Authors: Valtonen M.J.
Published: July 2016

In mergers of galaxies their central black holes are accumulated together. We show that few-black hole systems arise which decay through black hole collisions and black hole ejections. The ejection statistics are calculated and compared with two observed systems where ejections have been previously suggested: double radio sources and high redshift quasars near low redshift galaxies. In both cases certain aspects of the associations are explained by the merger hypothesis.
M51’s Spiral Structure
Authors: Howard S. , Byrd G. G.
Published: July 2016

The M51 system (NGC 5194/5195) provides an excellent problem both in spiral structure and in galaxy interactions. We present an analytic study of a computer experiment on the excitation mechanisms for M51’s spiral arms and whether or not a halo is important for these mechanisms. This work extends previous numerical studies of the M51 system by including self-gravitation in a two component disk: ’gas’ and ’stars’, and a dark halo. The analytic study provides two new observational constraints: the time (≈ 70 — 84 million years ago) and position angle of perigalacticon (300°). By using these constraints and a simple conic approximation, the search for the companion’s possible orbit is greatly simplified. This requires fewer N-body simulations than a fully self-gravitating orbit search. Fig. 1 shows the dust lane spiral pattern of M51 overlaid on an optical photograph. The analytically determined direction of perigalacticon is indicated with a line.
Dynamics and Configurations of Galaxy Triplets
Authors: Anosova Joanna P. , Orlov Victor V. , Chernin Arthur D. , Ivanov Alexei V. , Kiseleva Ljudmila G.
Published: July 2016

Two methods are proposed for describing the distributions of the triplet configuration parameters characterizing a tendency to alignment and hierarchy: (1) obtaining a representative sample of configurations and determining its statistical parameters (moments and percentages); and (2) dividing the region of possible configurations of triple systems (Agekian and Anosova, 1967) into a set of segments and finding the probabilities for the configurations to find themselves in each of them.
On the Large-Scale Structures Formed by Wakes of Open Cosmic Strings
Authors: Hara Tetsuya , Morioka Shoji , Miyoshi Shigeru
Published: July 2016

Large-scale structures of the universe have been variously described as sheetlike, filamentary, cellular, bubbles or spongelike. Recently cosmic strings become one of viable candidates for galaxy formation scenario, and some of the large-scale structures seem to be simply explained by the open cosmic strings).
Numerical Simulations of Interacting Disk Galaxies
Authors: Noguchi Masafumi
Published: July 2016

Galaxy-galaxy interactions have long attracted many extragalactic astronomers in various aspects. A number of computer simulations performed in the 1970s have successfully reproduced the peculiar morphologies observed in interacting disk galaxies and clarified that tidal deformation explains most of the observed global peculiarities. However, most of these simulations have used test particles in modelling the disk component. Tidal response of a self-gravitating disk remains to be further clarified.

Another topic which is intensely discussed at present is the relation between galaxy-galaxy interactoins and activity. Many observations suggest that interactions trigger strong starbursts and possibly active galactic nuclei (AGN). However, the detailed mechanism of triggering is not yet clear. It is vital here to understand the dynamics of interstellar gas.
Starbursts in Interacting Galaxies: Observations and Models
Authors: Bernlöhr Konrad
Published: July 2016

Starbursts have been a puzzling field of research for more than a decade. It is evident that they played a significant rôle in the evolution of many galaxies but still quite little is known about the starburst mechanisms. A way towards a better interpretation of the available data is the comparison with evolution models of starbursts. The modelling of starbursts and the fitting of such model starbursts to observed data will be discussed in this paper. The models have been applied to a subset of starburst and post-starburst galaxies in a sample of 30 interacting systems. These galaxies are not ultraluminous FIR galaxies but rather ordinary starburst galaxies with FIR luminosities of a few 1010 to a few 1011L⊙.
Caustic Waves in Galaxy Disks Produced in Collisions with Low Mass Companions
Authors: Struck-Marcell Curtis
Published: July 2016

At this meeting much attention has been focussed on interactions and mergers between roughly equal mass galaxies. On the contrary, I will begin by mentioning a few justifications for studying collisions with relatively low mass companions, specifically, less than about one third of the mass of the target galaxy. The first is simply that such collisions are likely to be common, given that the galaxy luminosity function is broad. The second reason is that such collisions have evidently been less well studied than collisions between nearly equal partners. However, there are a few important exceptions to this generalization, including the sinking satellite problem (e.g. Quinn and Goodman 1986), and the collisional model for the formation of shell galaxies in which a companion of negligible mass is completely disrupted(e.g. Dupraz and Combes 1986, Hernquist and Quinn 1988). The third, and potentially most important reason, is that the effects of a collision with a low-mass companion are less extreme (at least from the big galaxy’s point of view!). Thus, these effects are closer to the theorist’s ideal of a “small perturbation”. This is important for both conceptually understanding the effects of the collision, and for justifying the use of approximate numerical techniques (e.g. restricted three-body) to study them.
Simulations of Gas Clouds in Interacting Galaxies
Authors: Thomasson Magnus
Published: July 2016

A companion can induce a varitey of morphological changes in a galaxy. I use N-body simulations to study the effects of different kinds of perturbations on the dynamics of a disk galaxy. The model is two-dimensional, with a disk consisting of about 60,000 particles. Most of the particles (80 %) represent the old stellar population with a high velocity dispersion, while the rest (20 %) represent gas clouds with a low velocity dispersion. Initially, the velocity dispersion corresponds to Q = 1 for the “star” particles, and Q = 0 for the “gas” particles, where Q is Toomre’s (1964) stability parameter. The gas clouds can collide inelastically. The disk is stabilized by a rigid halo potential, and by the random motions of the old “star” particles. To simulate the effect of an encounter on the disk, a companion galaxy, modelled as a point mass, can move in a co-planar orbit around the disk. A complete description of the N-body code is found in Thomasson (1989).
The Mass–Ratio Distribution of Short–Period Binaries
Authors: Mazeh T. , Goldberg D.
Published: July 2016

We present a new algorithm to derive the mass-ratio distribution of an observed sample of spectroscopic binaries. The algorithm replaces each binary of unknown inclination by an ensemble of virtual systems with a distribution of inclinations. We show that contrary to a widely held assumption the orientations of each virtual ensemble should not be distributed randomly in space. A few iterations are needed to find the true mass-ratio distribution. Numerical simulations clearly demonstrate the advantage of the new algorithm over the classical method. We have applied the new algorithm to the recent large sample of G-dwarf spectroscopic binaries, and got a uniform or perhaps a slightly rising linear mass-ratio distribution. This result suggests that the mass-ratio distributions of short-period and long-period binaries are substantially different. It also indicates that the mass distribution of the secondary stars is not the same as that of the single stars.
The Use of Pulsating Stars in Orbit Determination
Authors: Pigulski Andrej
Published: July 2016

In a double or a multiple system, in which one of the components is a pulsating star, the light-time effect leads to apparent changes of the pulsation period. In some cases, one can obtain much more accurate values of the spectroscopic elements from the fit to the 0 — C diagram than from classical analysis of the radial-velocity data. In addition, in the analysis of the O — C diagram, photometric observations can be used. They are easy to obtain, and therefore are usually more numerous than the spectrographic ones.

Below we present the results of a study of three stellar systems, in which the light-time effect is observed. Primaries in all these systems are β Cephei-type pulsating variables.
On the Reduction of CCD Observations of “Close” Visual Binaries
Authors: Sinachopoulos D.
Published: July 2016

We discuss the accuracy of CCD astrometry, and we present an improvement on the method used for the photometric reduction of visual double stars CCD data, whenever the angular separation of the components is only a few arcseconds.
Spectroscopic and Photometric Studies of an X-ray–Selected Sample of Chromospherically Active Binary Stars
Authors: Stefanik Robert P. , Marschall Laurence A. , Nations Harold L.
Published: July 2016

Data from the Einstein X-Ray satellite continue to provide useful information for studies of x-ray emitting objects. The Einstein Medium Sensitivity Survey (EMSS), a tabulation of serendipitously discovered point sources from the Einstein database, included a number of objects which were identified, on the basis of spot sampling of optical spectra, as likely binary star systems (Fleming 1988, Silva et al. 1987; Takalo & Nousek 1988). Because the sample is limited primarily by X-ray flux, the physical characteristics of these stars are of considerable interest for understanding the origins of stellar activity among cool stars.
IUE Studies of Hot Binary Stars
Authors: Stickland David J.
Published: July 2016

The International Ultraviolet Explorer (IUE) was launched on 26th January 1978 and is still fully operational today, with several more years hopefully to come. After six months, the fully–reduced data is consigned to public–access archives maintained by the project agencies (NASA, ESA, and SERC). Thus, in addition to observations from current and future programmes, there are ~12,000 high–dispersion (Δλ ~ 0.15Å) spectra readily available now for research on stars hotter than about mid-B type. Furthermore, a uniform reprocessing, with optimum schemes, of all past IUE images has begun, to create the Final Archive which will be made accessible on–line through optical disk storage systems and will ensure the value of IUE data well into the future.
A Speckle Duplicity Survey of the Hyades Cluster
Authors: Mason B.D. , McAlister H.A. , Hartkopf W.I.
Published: July 2016

Due to its proximity to the Sun, the Hyades serves the critical role of luminosity calibration of all cluster main sequences, and hence is one of the lower rungs in the cosmic distance ladder. We attempt here to use the enhanced capabilities of speckle interferometry, in comparison with classical techniques, to add to the list of binary and multiple stars in the Hyades. New systems will not only eventually help to improve our knowledge of the cluster distance, but they will also help further our understanding of the formation and evolution of binary and multiple stars in the cluster environment.
Biographical and Historical Notes on the Pioneers of Photometry in Ireland
Authors:   The Editors
Published: July 2016

As the circumstances of the early electrical measurements of starlight in Ireland are not widely known we wish to take this opportunity to set down the facts, as far as they are known to us. Corrections or new information will be welcomed.

The observations made in Dublin in 1892 were the result of a collaboration between four graduates of Trinity College: George M. Minchin, William H.S. Monck, Stephen M. Dixon and George F. Fitzgerald. The observations in 1895 were made at Daramona Observatory, Co. Westmeath with a 24-inch reflector by Minchin, Fitzgerald and the owner of the telescope, William E. Wilson. In 1875 Minchin was appointed Professor of Applied Mechanics at the Royal Indian Engineering College at Coopers Hill, near Staines in London. In 1877 he started a long series of investigations of photoelectricity using a small optical laboratory at Coopers Hill and the laboratories of University College London. His initial aim was to transmit images electrically but he became skilled in making photovoltaic cells of selenium.

By September 1891 Minchin had succeeded in making some working cells and he wished “to test them on the stars”. He contacted his friend Monck who had recently set up an observatory in his back garden in Dublin. Monck in turn asked Fitzgerald for the loan of a galvanometer or electrometer and for advice in its use. As Fitzgerald did not have a suitable instrument, he ordered Clifton’s form of Thomson’s quadrant electrometer, which arrived near the end of the year. It seems that Minchin also sent some of his cells to Dr Boeddicker in the spring of 1892 for trials on the 72-inch telescope but no reports are available.
Crowded Field Photometry using Post-Exposure Image Sharpening Techniques
Authors: Redfern R.M , Shearer A. , Wouts R. , O’Kane P. , O’Byrne C. , Read P.D. , Carter M. , Jordan B.D. , Cullum M.
Published: July 2016

The technique of image sharpening which allows high resolution images to be produced from ground-based telescopes is applied to the problem of photometry in crowded field regions - such as close to the cores of globular clusters. The conditions for image sharpening are discussed and the technique is demonstrated using simple objects (close double stars). Preliminary results from image sharpening of M15 are presented.
Determination of Data Quality and Results from two Mount Hopkins Robotic Telescopes
Authors: Pyper Diane M. , Adelman S.J. , Dukes R.J. , McCook G.P. , Seeds M.A.
Published: July 2016

We present various methods for determining night quality from observations obtained with totally unattended automatic photoelectric telescopes at the Fairborn Observatory site on Mt. Hopkins, AZ. Telescopes are the Phoenix 10-inch (P10) and the Four College 75-cm (CAPT). Filter systems used are Johnson UBV, Kron-Cousins RI and Strömgren uvby. As a preliminary data filter for the P10 “rent-a-star” data, all observations with standard errors of the mean (SEM) above 20 mmag are discarded; a summary of nightly SEM’s, number of aborts and total observing time is sent to each user. The CAPT data are evaluated by standard deviation of magnitudes or counts for photometric groups and for an entire night. The Geneva photometric statistics are computed for these latter data and have proved useful as a preliminary screen for bad data. Various criteria for good and bad groups and nights are discussed. Scientific results are presented for several magnetic CP stars that were observed using both telescopes. Differences in precision of the data and strategies for observing are discussed.
GNAT — A Global Network of Automatic Telescopes
Authors: Crawford D.L.
Published: July 2016

All of us “have-nots” need more telescope time, for ourselves and for our students. There are also many programs where a global linkage is needed to accomplish the objectives. In addition, the world needs more and better science education; astronomy can be a leader if it has adequate facilities to do so. A global network of automatic telescopes can help supply these needs, which are global, spanning all countries. A new non-profit organization (GNAT, Inc.) has been formed to be the catalyst to develop and implement such a concept. We hope that many astronomers and organizations will become “members” of GNAT.
Globalizing Observations: Prospects and Practicalities
Authors: Budding E.
Published: July 2016

To promote fuller awareness we should aim to globalize observations. In a more immediate sense, this addresses the planetary distribution of observing facilities and their access. What components in such facilities occur in ‘global networks’? What factors optimize the growth and scientific viability of such a network? What kinds of progress can be expected?
Light Curves of Supernovae
Authors: Leibundgut Bruno
Published: July 2016

Although emerging from a range of progenitor stars and the product of different explosion mechanisms the light curves of the various supernova types are shaped mainly by radioactive power. Core-collapse supernovae have in addition early peaks from shock breakout with a subsequent cooling phase and massive extended stars a recombination (plateau) phase. Variations occur mostly due to differences of the progenitor stars. While there appears to be a fair understanding of the light curves of SNell, new wrinkles are emerging for SNela. The photometry of SNe lb and SNe Ic remains unsatisfactory.
Observations of Type la Supernovae
Authors: Suntzeff Nicholas B.
Published: July 2016

The quality of observational data on Type la supernovae has improved remarkably in the last few years, due mainly to monitoring programs with CCD-equipped detectors on small aperture telescopes at observatories across the world, and at the space observatories. I will review the recent observational characteristics of Type la supernovae, focusing the discussion on our observations of SN1992A in the SO galaxy NGC 1380 in the Fornax cluster as a reference to other Type la events. We now have strong evidence that Type la events are not a homogeneous class, but vary in both color and brightness at maximum light, vary in rise time and decline from maximum, and have spectral characteristics at maximum light that are correlated with these photometric parameters. Insofar as the SBF, PNLF, and infrared Tully-Fisher distance scales are correct, the observed (uvoir) bolometric light curves also indicate that these supernovae are less luminous than expected from the models of the explosion of a C-0 white dwarf at the Chandrasekhar mass.
Understanding the Nebular Spectrum of SN 1987A
Authors: McCray Richard
Published: July 2016

The nebular spectra of supernovae differ from those of better-known emission nebulae in that many of the emission lines are optically thick. Here we sketch the theory for interpreting such spectra, and show how it can be used to interpret prominent emission line systems in the spectrum of SN 1987A. As examples, we describe: (1) a simple method to infer the density of OI from observations of the evolution of the doublet ratio in [O I]λλ6300; (2) new kind of hydrogen recombination hne spectrum; (3) an analysis showing that the Call infrared emission lines must come from primordial, not newly-synthesized, calcium; (4) a theory for the Fe/Co/Ni emission lines that shows that the inner envelope of SN 1987A must have a foamy texture, in which low density radioactive bubbles of Fe/Co/Ni reside in a massive substrate of hydrogen, helium, and other elements.
Optical and UV Observations of Supernova Remnants
Authors: Fesen Robert A.
Published: July 2016

Recent observations of the galactic supernova remnants the Crab Nebula, SN 1006, Cas A, and the Cygnus Loop are reviewed. New studies of the Crab Nebula suggest its progenitor may have had appreciable mass loss in the form of a circumstellar disk resulting in both a bipolar expansion and formation of the synchrotron ‘bays'. Unusually high proper motion knots near to and possibly directed away from the pulsar also have been reported. In the Cas A remnant, a NE jet of ejecta appears to be a plume of mantle material with expansion velocities up to 12000 km s-1 or nearly twice that seen in the main ejecta shell. HST observations of the sdOB star located behind SN 1006 indicate symmetrically expanding Fe II ejecta out to 8100 km s-1. Lastly, deep images of the Cygnus Loop reveal emission structures similar to those seen in 2D & 3D shocked cloud simulations.
The Simulation and Results of a New Speckle Image Processing Technique
Authors: Cady F. M. , Bates R. H. T.
Published: July 2016

A new technique called shift-and-add, which allows nearly diffraction-limited images to be formed of objects viewed through a randomly distorted, turbulent media, has been formulated. True images may be obtained through the earth’s atmosphere when the method is used. It has been shown that this can be achieved even though the telescope may have severe aberration and when using a much wider bandwidth than that used at present in stellar Speckle Interferometry. Results are given for an object of greater extent than simple binary or groups of point sources.
Astrometric Properties of the KPNO 4m Telescope – Prime Focus CCD Detector System
Authors: Monet David G.
Published: July 2016

A parallax program was started in July, 1980, using a CCD detector at the prime focus of the KPNO 4m telescope. The results obtained to date indicate that the centroids of stellar images can be measured to accuracies of 0.25 microns or better from each 2 minute exposure on stars of about 17th magnitude with a filter of 800 Angstroms width centered at 6500 Angstroms (the scale of the KPNO 4m with the doublet corrector is 19.60 milli-arc-seconds per micron). The current CCD, a Fairchild CCD 211, is of relatively low quantum efficiency, about 8%. The integration times become prohibitively short on 15th magnitude and brighter stars. This technology seems quite attractive for the observation of astrometric binaries, as accuracies of about 3 milli-arc-seconds are obtained with only 12 minutes of telescope time, and there is no special set-up required for each field. If time permits, some comments will be made about some preliminary astrometric tests of a 3-phase TI 800 × 800 CCD performed in January, 1981, in collaboration with Roger Lynds of the Sapce Telescope Wide Field Camera Team.
Variable stars in M31 from the MEGA survey
Authors: Alves David R. , Baltz Edward A. , Crotts Arlin , Bergier Alex , Cseresnjes Patrick , Gersch Alan
Published: July 2016

The MEGA microlensing survey is introduced and several topics about variable stars in M31 are discussed. An adopted model population of semiregular (SR) variable stars is presented, and the efficiency to recover these stars in M31 in a specific example MEGA dataset is predicted. The period-flux amplitude relation of the SRs discovered by MEGA could be used to measure the inclination of the M31 disk.
Variable stars from two surveys of microlensing in M31
Authors: Crotts Arlin P.S. , Boyle Richard P. , Corbally Christopher J. ,   the MEGA Collaboration
Published: July 2016

Recently we completed the VATT/Columbia survey monitoring a portion of M31 for microlensing and stellar variability, and report here on the microlensing result. Also, we have nearly completed a much larger survey (MEGA) covering most of the stars in M31, for which we have started cataloging many tens of thousands of Cepheids, Miras, eclipsing variables and other kinds of variable stars. The microlensing results from these two surveys hint that a significant fraction of the dark matter in M31 is composed of stellar-mass objects in the halo.
Multiperiodic RR Lyrae stars in the Galactic Bulge and the SMC
Authors: Mizerski Tomasz
Published: July 2016

I have performed a detailed analysis of multiperiodic RR Lyr stars of the Galactic Bulge and the Small Magellanic Cloud. In the rich OGLE-II database on the Galactic Bulge objects I detected more than 2500 RR Lyr stars, with almost 600 of them exhibiting multiperiodic behavior of various, sometimes unique, kinds. Many of them can only be explained by excitation of nonradial modes. There are two major, striking differences between the two discussed stellar systems: the incidence rate of RRd double mode pulsators is over 30 times higher in the SMC than in the Galactic Bulge, and there are more than twice as many Blazhko stars in the Galactic Bulge as in the SMC.
The distance to the Large Magellanic Cloud from first overtone RR Lyrae variables
Authors: Muzzin A.V. , Clement C.M. , Alves D.R. ,   The MACHO Collaboration
Published: July 2016

Fourier coefficients have been derived for the V and R light curves of 330 bona fide RR Lyrae first-overtone (RR1) pulsators in 16 MACHO fields near the bar of the LMC. We use the Fourier phase parameter ɸ31 and log P values to select a subsample of these stars which are similar to the RR1s in the Galactic globular cluster M5. Assuming that the M5-like stars in the LMC have absolute magnitudes comparable to the HB stars in M5, we use independent studies to derive their mean absolute V magnitude and compute a visual distance modulus of μLMC = 18.43 ± 0.06 (statistical) ±0.16 (systematic). By selecting stars on the basis of their light curve parameters, we are able to derive a distance modulus that does not depend on the somewhat poorly determined Mv – [Fe/H] relation for RR Lyr stars.