bluuebunny/crossref_metadata_2025 huggingface dataset:
The AAVSO and its Variable Star Data Bank
Authors: Mattei Janet Akyuz
Published: July 2016

The American Association of Variable Star Observers (AAVSO) is the largest organization of variable star observers in the world that coordinates observations, and evaluates, compiles, processes, publishes, and disseminates them to the astronomical community. The organizational structure of the AAVSO, i t s visual and photoelectric observing programs, data management, publications, and services to the astronomical community are discussed.
Organized Observations of Night-Sky Brightness in Japan
Authors: Kosai Hiroki , Isobe Syuzo
Published: July 2016

Observations of the night-sky brightness were organized at 106 places in Japan by a promotion of the Environmental Agency with the help of many local governments. Two kinds of measurements were carried out: 1) Number of stars were counted in a region of triangle formed by Alpha Lyr, Epsilon Lyr, and Zeta Lyr by at least 10 contributors at each point. 2) Photographs of a star field at the zenith at each point were taken with the same type of camera and film. These results gave us a good idea on distribution of night-sky brightness in Japan.
Light Pollution Modeling
Authors: Garstang R. H.
Published: July 2016

The growth of urban development and its accompanying outdoor lighting has made the search for new observatory sites increasingly difficult. A method of predicting the brightness of the night sky produced by a city of known population and distance is useful in making studies of prospective new observatory sites, as well as in studying the likely future deterioration of existing sites. Other sources of light pollution can be investigated using the same model. In most cases, several cities are responsible for the light pollution at a given site, and the predicted night sky brightness is the sum of the contributions of all the cities. In this paper, we shall review the surprisingly little work which has been done on predicting night sky brightnesses from model calculations.
The National Radio Quiet Zone and the Green Bank RFI Environment
Authors: Sizemore Wesley A.
Published: July 2016

Today, I would like to discuss with you the history of the National Radio Quiet Zone, the regulation procedures for fixed radio transmitters inside the NRQZ and the RFI environment at the National Radio Astronomy Observatory (NRAO) site in Green Bank, West Virginia.
Protection of Passive Bands in Australia, India, and Japan
Authors: Robinson B.J.
Published: July 2016

The problems of protecting passive bands in Australia, India, and Japan reflect the variety of research activities and radio telescopes in those countries, colored by the degree of user friendliness of the frequency management authorities.

In India, it is important to protect frequencies below 1400 MHz (for high redshift hydrogen line absorption or emission) and continuum bands at 327 MHz and 150 MHz (the latter currently allocated to cordless phones, paging systems, and rural communication).

In Japan, protection from harmful interference has been sought and refused at 4.8 and 5 GHz (microwave network), 10 and 15 GHz (mobile relay service), and 22 GHz (mobile data relay service). But extensive radio astronomy usage of mm to sub-mm bands has established priority for their use and allocation.

In Australia, there are major problems at 408 MHz (telephone links), 1.6 GHz (GLONASS, RDSS, and Land Mobile Service), 4.9 to 5 GHz (RDSS), and 22 GHz (satellite broadcasting and high definition TV service).

The degree of user friendliness of the frequency management administration appears to rate: 1. Australia, 2. India, 3. Japan on a diminishing scale of cooperation and concern. This affects the awareness of the radio astronomy community of conflicting allocations and the level of input into CCIR and the WARC.
RFI Survey for the Giant Metrewave Radio Telescope in India
Authors: Swarup G. , Venkatasubramani T.L.
Published: July 2016

A Giant Meterwave Radio Telescope (GMRT) is being set up at Khodad about 80 km north of Pune in India for operation in the frequency range of about 30 to 1500 MHz. It is to be completed by 1992 and is being designed to investigate many outstanding problems in the fields of galactic and extragalactic astronomy. We present here measurements of man-made radio frequency interference (RFI) conducted at the GMRT site in 1985 and 1988. It is seen that highly sensitive radio astronomy observations can still be made at selected bands in the above frequency range because of the relatively low level of RFI in India. However, this advantage may not remain for more than a decade or two.
Radio Frequency Interference Detection from Space
Authors: Howard William E.
Published: July 2016

Occasional interference experienced in the channels of communications satellites has prompted an analysis to see how radio frequency interference (RFI) might be detected from space. RFI may be experienced on any type of satellite, including commercial and scientific satellites. For a satellite in geostationary orbit that interference may come from anywhere in the hemisphere under the satellite. Because the location of an interfering transmitter is so uncertain, traditional means for geolocating it is not effective. “Down-looking” detectors are needed to detect the “up-looking” interference. Moreover, a low cost, simple solution to the problem – one in which the cost to geolocate is small relative to the cost of the downtime in the channel – is required in order to make the solution tractable.
Plinian eruptions à la Eta Carinae
Authors: Davidson Kris
Published: July 2016

Eta Carinae is at once ourmost notableLBV but also adoubtfulLBV, because its Great Eruption observed 150 years ago was so unique. Since that event exceeded other major LBV outbursts by orders of magnitude in ejected mass and energy, we are not certain that it really was an example of S Dor, P Cyg, R127-type behavior. But even if it turns out to be a freak,ηCar has provided either the original example or one of the earliest hints for several facets of the LBV phenomenon,e.g.:

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Visual-wavelength brightening with little change in luminosity during each major mass-loss event;

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The idea of a modified Eddington limit causing instability in a critical range of surface temperature;

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CNO-processed surface material;

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Bipolar structure in the ejecta.
The B[e] stars
Authors: Zickgraf F.-J.
Published: July 2016

B[e] supergiants show evidence for a non-spherical two-component stellar wind. The general appearance and the physical properties of the suggested disk-like configuration are discussed. The high mass-loss rates, the surprisingly large number and the location in the H-R diagram make these stars important for the understanding of the post-main-sequence evolution of massive stars.
High resolution coronographic imaging of AG Carinae
Authors: Nota Antonella , Paresce Francesco
Published: July 2016

We present the first high resolution observations of the ring nebula around the galactic LBV AG Car obtained through broad band B, V, R, I filters with the STScI coronograph on the ESO 2.2 m. telescope. Highly anisotropic continuum emission in all these bands is clearly detected, in the shape of a bipolar structure elongated along the NE-SW direction extending from a few arcsecs from the star out to ⋍ 15 arcsecs corresponding to a projected linear distance of ⋍ 0.5 parsecs, with a surface brightness in the range 17.9-19.4 mag/arcsec2. Its essentially neutral color with respect to the star Δ(V-I) = −0.07) suggests that the observed radiation is starlight scattered by dust grains of diameter > 1μ.
Infrared observations of circumstellar ejecta around Luminous Blue Variables
Authors: McGregor Peter J.
Published: July 2016

Recent infrared spectroscopy and imaging of LBVs lead to the following results. CO overtone emission at 2.3μm has been found in 13 LBVs in the Galaxy and the LMC. This emission is collisionally excited in warm (3000 – 5000 K), dense (NH> 1010cm-3) circumstellar material. Circumstellar disks offer favorable conditions for the formation and excitation of CO molecules and are very likely the location of the observed emission. It is proposed that the LBVs showing 2.3 μm CO overtone emission possess the highest density circumstellar disks.

A group of eight LBVs has been identified in the LMC with He I 2.058 μm emission stronger than H I Brγ. This group includes the CO emission star HD 37836. Helium is over-abundant in these stars withN(He)/N(H) ranging from 0.2 to >0.5. Remarkably five of the helium strong stars belong to the small class of Ofpe/WN9 stars and a further two are probably related to this class.

Slit scans of the galactic LBV AG Car have resolved the far-infrared emission from this star, clearly showing it to originate from cool dust in the circumstellar ring structure. Thermal equilibrium considerations require large grains in the ring in order to match the measured grain temperature and radial distance. Similar slit scans of the galactic B[e] star HD 87643 fail to resolve the far-infrared emission from this star at the 10″ level.
Close binary models for Luminous Blue Variable stars
Authors: Gallagher J. S.
Published: July 2016

The evolution of massive close binary stars inevitably involves mass exchange between the two stellar components as well as mass loss from the system. A combination of these two processes could produce the stellar wind-modulated behavior seen in LB Vs. The possibility that LBVs are powered by accretion is examined, and does not appear to be a satisfactory general model. Instead, identification of LBVs with close binaries in high mass-loss rate or common envelope evolutionary phases shows promise.
Theoretical relations between LBV’s and other stars
Authors: Langer Norbert
Published: July 2016

The so called Luminous Blue Variables (LBVs) form a rather heterogeneous class of very active, luminous (and therefore massive) stars (c.f. R.M. Humphreys, this volume). The following two points are the aim of theoretical work concerning these objects: 1. to know their internal structure from the center up to the atmosphere, i.e. to find out the place of these objects in the course of thermonuclear evolution, or to identify the physical processes which are responsible for the different types of mass loss phenomena, and 2. to conclude which were their preceding evolutionary phases, and to predict their future evolution, i.e. to identify LBV progenitors and descendants, derive their ages, and so on. The basic tool of the theorists is a stellar evolution computer code, which allows to perform evolutionary computations (including different assumptions, which are necessary since several physical ingredients cannot yet be treated from first principles), leading stellar tracks through the part of the HR diagram where LBVs are found. But in this context we meet already a basic problem: in a certain small area of the HR diagram (which may correspond e.g. to some kind of error box) stars of several different types may be identified by the observers, each type may be even devided into several subtypes. Therefore, the correlation of computer models and observed stars is often very difficult or impossible. The various types of stars are mainly classified by spectroscopic criteria, while important “theoretical quantities” as stellar masses or the chemical composition are hard to derive from observations.
Optical and UV investigation of the envelope of AG Carinae
Authors: Viotti Roberto , Altamore Aldo , Rossi Corinne , Cassatella Angelo
Published: July 2016

The galactic LBV object AG Car is unique for assembling several interesting features: (i) a light curve typical of Hubble-Sandage variables, (ii) a largely variable P Cygni-type spectrum, (iii) a strong IR excess, and especially (iv) a smallring nebula. Caputo and Viotti (1970) found that during 1949-59 the AG Car spectrum varied betweenA1andB0equivalent spectral types. A dramatic evolution occurred in recent years, when the visual magnitude gradually faded from V=6 in 1981 to V=8 in 1985, followed by a rise of the line excitation fromAeqin 1981 (Wolf and Stahl 1982), toBeqin 1983 (Viotti et al. 1984), and to0fpe/WN9in January 1985 (Stahl 1986). This behaviour has represented a unique chance to follow a LBV in different spectral ranges during its major photometric and spectral changes. In the following we present the results of a long term monitoring of the star and of its nebula in the optical and UV. We propose thatAG Car evolved in recent times from a red supergiant phase, and that the present LBV phase is characterized by acritical structureof the stellar atmosphere.
Analysis of LBV circumstellar envelopes using FeII lines
Authors: Rossi Corinne , Muratorio Gerard , Friedjung Michael , Viotti Roberto
Published: July 2016

Emission and absorption lines of Fell frequently dominate the optical and UV spectra of LBVs. Many luminous blue stars possess a rich optical Fell emission line spectrum, which can be used as diagnostic of their extended atmospheres (Viotti 1976a). Since the launch ofIUEseveral LBVs were observed in UV, and in many cases (n Car, AG Car, P Cyg, Hubble Sandage variables, etc.) their spectra were found dominated by a large amount of Fell absorptions, presumably formed in cooler envelopes. Often these absorptions are so strong as to seriously affect the UV energy distribution. In order to study line formation outside LTE of such a complex ion, the Fell line intensities in luminous stars were analyzed using the Self Absorption Curve (SAC) method by Friedjung and Muratorio (1987). The fitting of the emission line fluxes in different multiplets to theoretical SACs obtained with different wind models, leads to the determination of the relative upper and also relative lower level populations. The overlapping of the individual multiplet curves gives the observational SAC which provides an estimate of the wind parameters (column density, acceleration parametera, mass loss rate). This method of analysis was applied to the optical and UV high resolution spectra of several luminous stars. For instance we found that in AG Car the relative population of the Fell levels from 1.6 to 8.6 eV can be fitted to the same Boltzmann distribution with an excitation temperature of Tex«=7200+/-350K, whereas for the W Cep star KQ Pup the linearity extends from 0 to about 9 eV with Tex=6700 K (Viotti et al. 1988).
Physics of instabilities in radiatively driven stellar winds
Authors: Owocki S.P. , Castor J.I. , Rybicki G.B.
Published: July 2016

One type of variability that is ubiquitous among luminous blue stars is that associated with their massive stellar winds. Ultraviolet spectral lines show variable narrow absorption components that may arise from dense shells or clumps in the wind; the observed soft X-ray and non-thermal radio emission from these stars may be produced in embedded wind shocks associated with these shells. The line-driving of such winds is known to be strongly unstable, and recent numerical simulations of the dynamical, nonlinear evolution of such instabilities indicate that such shocks and dense shells do indeed form (Owocki, Castor, and Rybicki 1988; hereafter OCR). However, the structure computed in these dynamical simulations is quite different, and in some sense opposite, what was anticipated in earlier heuristic shock models (e.g. Lucy 1984, Krolik and Raymond 1985, Abbott 1988); the highest speed material is veryrarefied, not dense, and the strongest shocks that form are of thereverse, not forward, type. In subsequent simulations we have found that the detailed character of this structure can depend on many variables, but this tendency always to form high speed rarefied waves and reverse shocks is quite robust. It is thus important that we have a clear understanding of the reasons for this tendency, and it is on this point that we focus our comments here.
Slash stars: Two types, two scenarios?
Authors: Conti P. S. , Bohannan Bruce
Published: July 2016

Of/WN, or as we will call them here, “slash ‘/’” stars were first described by Walborn (1977; 1982a; 1982b) as hot luminous stars that have spectroscopic properties of both O and low-ionization WN spectral classes. Walborn called attention to Sk -67° 22, an 03IP7WN6-A star that had strong O-type absorption lines, but also abroademission feature at Hell λ4686Å. The ‘/’ symbol was used to indicate that there was difficulty in assigning either the Of or the WN type unambiguously. He labled other LMC stars as Ofpe/WN9 not only because of a similar ambiguity in the classification but also the presence of narrow “nebular” emission lines associated with the star. Conti and Garmany (1983) pointed out the similarity of Sk -71° 34 to Sk -67° 22. A total of ten stars with Ofpe/WN9 character have now been identified in the LMC (Bohannan and Walborn 1989) : HDE 269927C, 269445, 269582, 269687, 269858, 269227; Sk -66 040, -67 266, -69 297; BE 381.
Morphological Type Correlation between Nearest Neighbor Pairs of Galaxies
Authors: Yamagata Tomohiko
Published: July 2016

Although the morphological type of galaxies is one of the most fundamental properties of galaxies, its origin and evolutionary processes, if any, axe not yet fully understood. It has been established that the galaxy morphology strongly depends on the environment in which the galaxy resides (e.g. Dressler 1980).

Galaxy pairs correspond to the smallest scales of galaxy clustering and may provide important clues to how the environment influences the formation and evolution of galaxies. Several investigators pointed out that there is a tendency for pair galaxies to have similar morphological types (Karachentsev and Karachentseva 1974, Page 1975, Noerdlinger 1979).

We analyzed morphological type correlation for 18,364 nearest neighbor pairs of galaxies identified in the magnetic tape version of the Center for Astrophysics Redshift Catalogue (Huchra 1987, hereafter CfA Catalog).
What is the Number of Spiral Galaxies in Compact Groups?
Authors: Tikhonov N. A.
Published: July 2016

The distribution of morphological types of galaxies in compact groups is studied on plates from the 6 m telescope. In compact groups there are 57% galaxies of late morphological types (S + Irr), 23% lenticulars (SO) and 20% ellipical galaxies. The morphological content of compact groups is very nearly the same as in loose groups. There is no dependence of galaxy morphology on density in all compact groups (and possibly in loose groups). Genuine compact groups form only 60% if Hickson’s list.
HI Studies of the Sculptor Group Galaxies
Authors: Carignan Claude , Puche Daniel
Published: July 2016

Results from large-scale mapping of the HI gas in the Sculptor group are presented. From our kinematic analysis, a mean global (M/LB) ⋍ 9 M⊙/L⊙ (at the last observed velocity point) is found for the individual galaxies. This is only a factor ~ 10 smaller than the (M/LB)dyn ⋍ 90 M⊙/L⊙ derived from a dynamical study of the whole group. The parameters derived from the mass models suggest that most of the unseen matter has to be concentrated around the luminous galaxies. Under the assumption that the Sculptor group is a virialized system and that all the mass is associated with the galaxies, an upper limit of ~ 40 kpc is derived for the size of the dark halos present in the five late-type spirals of the group.
The HI Content of Non-Isolated Galaxies
Authors: Zasov Anatoli V.
Published: July 2016

It seems obvious that the evolution of star formation rate and hence of gas content in galaxies strongly depends on their environment. It reveals itself in particular in enhanced star formation or even in a strong burst of activity of massive stars often observed in an interacting galaxies. Nevertheless it should be noted that the time scale for the gas to be exhausted in these galaxies is unknown even approximately. To clarify a role of surroundings in the evolution of disk galaxies we should compare the HI content of isolated and non-isolated galaxies otherwise similar by their properties.
HI and Mass Distribution of GR8
Authors: Beaulieu Sylvie , Carignan Claude
Published: July 2016

The dwarf irregular galaxy GR8, which is at the extreme faint end of the luminosity and mass functions, is studied using optical photometry and 21cm HI line observations. It is shown that rotation is only important to the gravitational support of the system in the inner parts (r < 250 pc). GR8 is one of the very few non-elliptical systems known (with M81dwA) where the random motions provide essentially all the support in the outer parts (r ≥ 500 pc). The Gaussian nature of the HI distribution and the isothermal distribution of the HI velocity dispersion implies M α R3 in the outer regions of GR8 (ie the stellar disk and the HI lie in the approximately uniform density core of the dark halo).
Infrared Images of Merging Galaxies
Authors: Wright G. S. , James P. A. , Joseph R. D. , McLean I. S. , Doyon R.
Published: July 2016

Infrared imaging of interacting galaxies is especially interesting because their optical appearance is often so chaotic due to extinction by dust and emission from star formation regions, that it is impossible to locate the nuclei or determine the true stellar distribution. However, at near-infrared wavelengths extinction is considerably reduced, and most of the flux from galaxies originates from red giant stars that comprise the dominant stellar component by mass. Thus near infrared images offer the opportunity to study directly components of galactic structure which are otherwise inaccessible. Such images may ultimately provide the framework in which to understand the activity taking place in many of the mergers with high IRAS luminosities.
Tidal Events and Galactic Activity
Authors: Hutchings J.B. , Neff S.G.
Published: July 2016

We report some results from recent and ongoing work which relate to the connection between nuclear activity and tidal interactions. We suggest that tidal events are in general a necessary but not sufficient condition for nuclear activation. We also suggest that nuclear activity generally develops at a ‘late stage’ of a tidal encounter, following star-formation and dust evaporation, and when the most obvious morphological disturbances may have disappeared.
Dynamical Experiments on Models of Colliding Disk Galaxies
Authors: Gerber Richard A. , Balsara Dinshaw S. , Lamb Susan A.
Published: July 2016

Collisions between galaxies can induce large morphological changes in the participants and, in the case of colliding disk galaxies, bridges and tails are often formed. Observations of such systems indicate a wide variation in color (see Larson and Tinsley, 1978) and that some of the participants are experiencing enhanced rates of star formation, especially in their central regions (Bushouse 1986, 1987; Kennicutt et al., 1987, Bushouse, Lamb, and Werner, 1988). In this paper we describe progress we have made in understanding some of the dynamics of interacting galaxies using N-body stellar dynamical computer experiments, with the goal of extending these models to include a hydrodynamical treatment of the gas so that a better understanding of globally enhanced star formation will eventually be forthcoming.
Paired and Interacting Galaxies: Conference Summary
Authors: Norman Colin A.
Published: July 2016

This has been an excellent conference with a very international component and a rich and wide ranging diversity of views on the topical subject of paired and interacting galaxies. The southern hospitality shown to us by our hosts Jack Sulentic and Bill Keel has been most gracious and the general growth of the astronomy group at the University of Alabama is most impressive.

The conference began with the presentation of the basic data sets on pairs, groups, and interacting galaxies with the latter being further discussed with respect to both global properties and properties of the galactic nuclei. Then followed the theory, modelling and interpretation using analytic techniques, simulations and general modelling for spirals and ellipticals, starbursts and active galactic nuclei. Before the conference I had written down the three questions concerning pairs, groups and interacting galaxies that I hoped would be answered at the meeting: (1) How do they form? including the role of initial conditions, the importance of subclustering, the evolution of groups to compact groups, and the fate of compact groups; (2) How do they evolve? including issues such as relevant timescales, the role of halos and the problem of overmerging, the triggering and enhancement of star formation and activity in the galactic nuclei, and the relative importance of dwarf versus giant encounters; and (3) Are they important? including the frequency of pairs and interactions, whether merging and interactions are very important aspects of the life of a normal galaxy at formation, during its evolution, in forming bars, shells, rings, bulges etc., and in the formation and evolution of active galaxies. In what follows I shall summarize the meeting and where possible focus on these three central issues. Since this is a conference summary my references are all to papers presented at this meeting.
Surveys of Spectroscopic Binaries at the Center for Astrophysics
Authors: Latham D.W.
Published: July 2016

For more than a decade we have been measuring stellar radial velocities with three almost identical digital speedometers on telescopes in Arizona and Massachusetts. By now we have accumulated nearly 100,000 measurements with a typical precision of better than 1 km s-1. One of the main scientific applications has been surveys of binaries in several different stellar environments, to study the frequency and orbital characteristics of binaries in a variety of stellar populations. A main goal is to confront theories of binary formation and evolution with observational results. With various collaborators we have investigated the binary populations among pre-main-sequence stars, in the Hyades and M67 open clusters, and in the Carney-Latham proper-motion sample. Thus, we have data for coeval samples of binaries covering a wide range of ages. One result is clear evidence for evolution of binary orbits. The orbital period at which there is a transition from circular to eccentric orbits gets longer for older samples of binaries, presumably due to tidal circularization. Another result is that the frequency of binaries does not seem to depend on the stellar population. Binaries are just as common among the oldest stars in the halo of our Galaxy as among the younger stars in the disk.
The Combination of Spectroscopic and Astrometric Data in the Analysis of Orbital Motions in Binary Star Systems
Authors: Morbey Christopher
Published: July 2016

Even though various types of data for binary stars are being obtained in unprecedented quantities there is still a lack of completeness. Because the reduction of combinations of these data adds to the fundamental concepts in astronomy it is advantageous to have available a general self-consistent method whereby all the elements of the orbits of a binary or multiple system may be solved simultaneously. Such a method is reviewed in this paper and an emphasis is placed on the specification of meaningful errors attached to the orbital elements.
High-Precision Radial Velocities of Southern Solar-Type Stars
Authors: Murdoch Kaylene , Hearnshaw J.B.
Published: July 2016

With a small telescope and conventional techniques we have achieved external radial-velocity errors for bright stars of only ±50 m/s by using an optical fibre feed between telescope and spectrograph. In a search for low-mass companions to solar-type dwarf stars, intrinsic radial-velocity variability was detected in some IAU radial-velocity standard stars but no convincing evidence was found of the presence of low-mass companions to the dwarfs.
Effects of Duplicity on the Period Changes of Cepheids
Authors: Szabados L.
Published: July 2016

The light-time effect and the phase jump in the pulsation period of Cepheids as two characteristic manifestations of duplicity are discussed.
The Companions of the Classical Cepheid FF Aql
Authors: Evans Nancy Remage , Udalski Andrej
Published: July 2016

We have obtained CCD photometry of the classical Cepheid FF Aql and the companion 6″ away to determine whether they are likely to be physically associated. Because the Cepheid is 5 magnitudes brighter than the companion, the measurements are difficult. The values we find for the companion are V = 11.14 ± 0.07 mag, B – V = 0.60 ± 0.05 mag and V – R = 0.39 ± 0.04 mag. If the companion were at the same distance as the Cepheid, its absolute magnitude would be MV = 2.58 mag, corresponding a spectral type of approximately A8 V. The observed (B – V)0 corresponds to a spectral type of F4 V to F5 V. The observed color and spectral type are incompatible with a ZAMS magnitude of the companion at the distance of the Cepheid.

Positional measures indicate that there may be relative motion between the two stars, which would be too large to be orbital motion. We conclude that the 6″.8 companion is not a member of the FF Aql system. Information about the four stars in the direction of FF Aql is summarized.
The Very Low–Mass Companion to BD+6° 398
Authors: Ianna P.A.
Published: July 2016

New parallax and orbital period estimates for the astrometric binary BD +6° 398 are presented. The mass of the unseen companion is discussed.
Methods of HIPPARCOS Double Star Parameter Estimation for Relative and Absolute Astrometry within the FAST Consortium
Authors: Bernstein H.-H. , Hering R. , Badiali M. , Cardini D. , Emanuele A.
Published: July 2016

This paper outlines the details of astrometric parameter determination of double stars from HIPPARCOS observations as prepared in the FAST consortium. Methods of parameter estimation are developed for relative astrometry and absolute astrometry. The capability of the procedures will be demonstrated using simulated observations, in describing the particular steps of a Monte Carlo simulation which have been executed at the Istituto di Astrofisica Spaziale (IAS) and at the Astronomisches Rechen–Institut (ARI).
Double and Multiple Star Speckle Observations at the 6-m Telescope
Authors: Balega I.I. , Balega Y.Y. , Vasyuk V.A. , McManus J.J.
Published: July 2016

During the last 15 years more than 9,000 speckle interferometric measurements of binary stars have been collected using large optical telescopes (McAlister & Hartkopf 1988). Among them a significant contribution to the world speckle data has been made by the 6-m telscope near Zelenchuk. Up to now this instrument provides the maximal spatial resolution for single–aperture telescopes. First speckle images of the binary Capella were recorded at the telescope in 1977 (Balega & Tikhonov 1977), but we spent 5 more years to create special television techniques for photon counting and digital means for image processing before we started the regular interferometric program of binary observations in the wide range of stellar magnitudes. At first, the measurements were conducted in cooperation with French astronomers from the Centre d’Etudes et de Recherches Geodynamiques et Astronomiques using the optical camera and the television detector developed by Blazit et al. (1977). Since 1983 our equipment has been in use. The program of observations was oriented upon the traditional problems of multiple star speckle interferometry:

1.

Determination of stellar distances and masses for different types of binaries whose orbital elements can be derived. This includes already known fast visual and astrometric pairs with undetermined orbits, spectroscopic binaries that can be resolved directly, and newly discovered interferometric pairs which show fast orbital motion. The main attention was devoted to the late–type dwarfs in the vicinity of the Sun.

2.

Search for the secondary components whose existence could explain anomalies of stellar spectra or photometry (stars with composite spectra, occultation binaries, etc.)

3.

Study of unusual binaries (symbiotic stars, binaries with relativistic components, such as SS 433, etc.)
Stellar Multiplicity Discovery by Lunar Occultations
Authors: White Nathaniel M.
Published: July 2016

The primary result of lunar occultation studies of multiple star systems is the discovery of new systems. Its use as a method of multiplicity discovery has been productive, although incidental to timing observations made by amateurs and professionals for 360 years. The capabilities and limitations as a method of discovering new double stars is discussed.
Photometric Observations of Three Double Stars by the Occultation Method — Comparison with Interferometric Results and with Preliminary Results of HIPPARCOS
Authors: Froeschlé M. , Meyer C.
Published: July 2016

We first briefly recall the geometry of the occultation of a double star by the Moon’s edge. Then we give a short description of the principle of the formation of the diffraction pattern. We present the results for three double stars and compare them with those obtained by other methods.
Multicolour Photometric System for Investigation of the Galaxy Population
Authors: Straižys V.
Published: July 2016

Many photometric systems for classification of stars have been proposed. However, not all of them are equally suitable for investigation of distant and reddened stars without additional information from their spectra. Earlier it was shown that the Vilnius photometric system is optimum for purely photometric classification of stars in spectral types, luminosities, metallicities and peculiarity types, when interstellar reddening is present. When realized with a CCD detector, the system permits to classify stars down to 17 mag with a 1.5 m class telescope or down to 20 mag with a 4 m telescope. A possibility of realizing the system with the WF camera of the Hubble Space Telescope is investigated. The problem of unification of broad-band and medium-band photometric systems is discussed.
Infrared Photometric Systems, Standards and Variability
Authors: Leggett S.K. , Smith J.A. , Oswalt T.D.
Published: July 2016

The accuracy with which infrared photometry can be carried out is currently limited by poor definition of the instrumental system and by the accuracy of the available standard stars. We present new colour transformations between the CIT J, H, K photometric system and systems currently in use at Cerro Tololo, Mauna Kea and Kitt Peak. The precision of the J, H, K data for some of the stars observed by Elias et al. is improved and the system extended to fainter stars suitable for use with larger telescopes and/or infrared arrays. Evidence of infrared variability has been detected for one M dwarf star in our programme.
Lessons from Very Long-Term, Very High-Precision Photoelectric Photometry
Authors: Lockwood G.W. , Skiff B.A. , Thompson D.T.
Published: July 2016

Traditional photoelectric techniques can achieve millimagnitude precision if a few simple rules are scrupulously followed. We illustrate the practical limits of differential photometry obtained with a dedicated telescope and photometer. Using a highly homogeneous set of measurements of bright F, G, and K solar analog stars, we present the distribution of observational noise and intrinsic stellar variability over a typical observing season and over the entire 8-year program. Finally, we list Strömgren uvby standards which we found to vary slightly.
The Avalanche Photodiode — A Promising Low Light Level Detector for Astronomical Photometry
Authors: Śzécésnyi-Nagy G.
Published: July 2016

Astronomical photometry like other scientific methods is always forced to search for up-to-the-minute instruments and the most sophisticated devices. The photomultiplier tube (PMT) is the most widely used photon detector offering high sensitivity and gain with acceptable quantum efficiency and spectral range but it also has some disadvantages. During the past few decades all of these parameters have been improved and it seems likely that possibilities for their continued development are exhausted.

In the meantime, technical development — especially micro electronics and semiconductor technology — has produced a new detector, the avalanche photodiode (APD). The APD which is often referred to as a solid-state PMT is just at the start of its career and we may expect its rapid perfection. Although properties of APDs were first discussed almost twenty years ago their mass production did not start until 1990. Early silicon APDs had very limited dimensions compared to PMTs but unfortunately this also implied that their photosensitive area was less than 0.25 mm. One more year of development has been enough to increase the photon collecting surface by a factor of 1000 and APDs may soon become possible rivals of PMTs.

Following a brief description of the new device and discussion of its operation a comparison of photodetector performance will be given in order to draw attention to those parameters which are of great promise. Those sections of astronomical photometry which are ready to benefit from the suggested testing and use of this kind of photon detector will be highlighted.
A Bidimensional Photon-counting Microchannel Plate Detector Using a Wedge and Strip Anode
Authors: Drazdys R. , Jukonis J. , Skrebutėnas A. , Vansevičius V. , Vilkaitis G.
Published: July 2016

A photon-counting detector with a 45 mm diameter active area has been developed using a microchannel plate (MCP) and the wedge and strip readout system. The detector uses a UV transparent glass input window proximity coupled to a stack of MCP. Quantum efficiency (QE) of the detector photo-cathode is ~ 20%. The resolution of ~ 60 μm FWHM at a gain of 5.107 has been achieved.
The MEKASPEK project — a new step towards the utmost photometric accuracy
Authors: Mantel K. H. , Barwig H. , Kiesewetter S.
Published: July 2016

We present the design of a new 4 channel, fiberoptic spectrophotometer which allows to measure the object, two comparison stars and sky background simultaneously throughout the whole optical wavelength range with high efficiency. The overall spectral resolution of about 50 in combination with over-sampling allows to eliminate colour dependent extinction effects to a high degree and guarantees accurate transformations to other broad band photometric systems.
Correlations between Atmospheric Extinction and Meteorological Conditions
Authors: Reimann H.-G. , Ossenkopf V.
Published: July 2016

A retrospective investigation covering about twenty years of wide-band and intermediate-band photometry at Jena University observing station allows an analysis of variations of atmospheric extinction at different time scales. A comparison with an earlier investigation by Wempe (1947) permits to draw conclusions about the evolution of air pollution by aerosols over nearly half a century. Complementary weather observations obtained at the meteorological observing station of the Jena University allow to find correlations between the variation of extinction parameters and the changing weather situations. Parallel Mie calculations allow to interpret the variations of the measured extinction data in terms of size variations of water-rich aerosols.
On Improving IR Photometric Passbands
Authors: Young A.T. , Milone E.F. , Stagg C.R.
Published: July 2016

The passbands of the Johnson JHKL broadband photometric system used at a number of major observatories have been compared to the atmospheric window transmissions calculated by MODTRAN, and a family of solar-composition model stellar fluxes from Kurucz (1991 private communication) have been used as input to model the atmospheric extinction under different water vapor content, altitude, and airmass conditions. A figure of merit related to the slope of the extinction curve at zero airmass describes the sensitivity of the response function to atmospheric extinction. We have compared passbands used at several observatories, and have designed an improved set of passbands.
Progress with the Whole Earth Telescope
Authors: O’Donoghue D. , Provencal J.
Published: July 2016

A summary of the results from seven global runs using the Whole Earth Telescope is presented, together with an evaluation of the scientific results obtained to date. Factors such as the distance of the target star from the equator, the nature and timescales of its intrinsic variability, etc. are shown to affect the value and quality of the results, as well as the traditional factors such as brightness and long-term coherent behaviour. Experience with the network shows that, taken as a whole, it enjoys far better weather than any one of its sites, and provides unprecedented ‘uncluttered’ resolution of time-series power spectra.
Time-Series Photometry: CCDs vs. PMTs
Authors: Kreidl T.J.
Published: July 2016

With the ability to obtain simultaneous photometry of many objects, CCD time-series photometry is a potentially powerful method for obtaining data, even under non-photometric conditions. In particular, the ability to utilize one or more comparison stars on the same frame without the need to move the telescope to a different field makes for a higher duty cycle than conventional photoelectric photometry. In addition, the ability to determine the local sky in a variety of ways plus the ability to use more complex analysis techniques such as profile fitting and curves of growth permits a variety of analysis options. Some of the advantages of utilizing CCDs and the techniques used in time-series photometry of compact objects are discussed. With the flexibility of modern CCD control systems, possibilities for real-time or near real-time data analysis using readily available computer technology are stressed. Brief discussions of periodicity analysis considerations and other aspects of the data acquisition are presented.
Type la Supernovae: Mechanisms and Nucleosynthesis
Authors: Nomoto K. , Yamaoka H. , Shigeyama T. , Iwamoto K.
Published: July 2016

We summarize various explosion models of Type la supernovae and their nucleosynthesis features for both Chandrasekhar and sub-Chandrasekhar mass white dwarf models. These models provide different predictions of the photometric and spectroscopic variations among Type la supernovae, which are compared with observations. Some attempts to model the peculiar SNe 1991T and 1991bg are shown.
Review of Contributions to the Workshop on SN1993J
Authors: Craig Wheeler J. , Filippenko Alexei V.
Published: July 2016

At its peak, SN 1993J was one of the brightest supernovae in this century, and it is being studied more thoroughly than any supernova except SN 1987A. It is proving to be similar to the transition object SN 1987K, which metamorphosed from being a hydrogen-rich Type II near peak to having a hydrogen-deficient nebular phase. SN 1993J has been observed throughout the electromagnetic spectrum and with optical spectropolarimetry. It is interacting with a dense circumstellar nebula and is generating radio and X-ray flux, but it has probably not been detected in gamma rays. The photometric and spectral evolution are consistent with a star of original mass ∼ 15 Mʘ that lost appreciable mass to a binary companion leaving an extended, helium-rich hydrogen envelope of ≲ 0.5 Mʘ and a helium core of ∼ 4 Mʘ. The spectral evolution will put strong constraints on the mixing of 66Ni and other species.
Radio Supernovae
Authors: Weiler Kurt W. , Van Dyk Schuyler D. , Sramek Richard A. , Panagia Nino
Published: July 2016

Radio observations have shown that some supernovae are powerful radio emitters which increase rapidly in brightness to radio luminosities which are hundreds to thousands of times greater than even the brightest known supernova remnant, Cas A. They then fade over a period of weeks, months, or years. This radio emission has been found to provide important information about the nature of the progenitor stars, their mass loss rates, and the circumstellar material surrounding them. RSN observations may also offer the possibility of extragalactic distance measurements and the presence of radio emission appears to be indicator of strong x-ray emission and late time optical emission.
X-Ray Spectroscopy of Supernova Remnants
Authors: Petre R.
Published: July 2016

X-ray spectroscopy can provide vital information about the progenitors and environments of supernova remnants. Plasma diagnostics and spectral modelling can be used to infer the energy of the remnant, the density and composition of the surrounding medium, and the degree of equilibrium in the shock heated gas. A new generation of X-ray spectrometers, the first of which was the Broad-Band X-Ray Telescope (BBXRT), has improved our ability to make precise measurements of X-ray line fluxes and energies. We summarize the results obtained from the BBXRT mission. These include a definitive measurement of the Fe K line centroid in the Tycho remnant, production of the first narrow-band X-ray maps (of Puppis A) and the first measurement of an electron-ion equipartition timescales in evolved remnants.
YZ Cas ± 0.5%
Authors: Lacy Claud H.
Published: July 2016

I will discuss one of the results of a continuing program to determine accurate masses and radii of stars in eclipsing binaries. This program actually began in 1976 with my work on the faint M-dwarf system CM Dra (Lacy 1977). By faint I mean . I needed high-dispersion spectra to get radial velocities, and an intensified solid state array detector called the Digicon, which had recently been installed on the coude spectrometer of the 2.7m reflector at McDonald Observatory, turned out to be the answer. 30 minute integrations were sufficient to get accurate radial velocities from the Hγ emission lines. The Digicon is very good at getting crumby spectra of faint objects fast. By crumby, I mean signal-to-noise ratio of less than 100.
Observation of Multiple Stars with the Digital Speckle Interferometer
Authors: Bonneau D. , Koechlin L.
Published: July 2016

Since 1977, the Digital Speckle Interferometer chiefly developed for the study of atmospheric structure in cool supergiant stars, has been used for observing multiple stars. It has provided binary star resolution down to 30 milliarcsec. separation with a precision from 3% to 10%.

The incertitude on position angle determination ranges from ± 1° to ± 5°.

Working in photon counting mode, we are able to estimate magnitude difference reaching Δ m ~ 3.0 with an uncertainty of about 0.2−0.3 magnitude.

On the basis of present experimentation, we think that 17th mag binaries can be resolved with a 3.6 meter telescope.
Le Telsecope Spatial et les Etoiles Doubles
Authors: Couteau Paul , Fulconis Monique
Published: July 2016

The number of new couples available for the Space Telescope can be estimated through the study of prior surveys and observational selection.

Surveys realized at the beginning of this century, as well as actual surveys being recalled, show that couples remain to be discovered. A method is developed showing the importance of instrumental selection by the difference of magnitude between the components, this way can be estimated the number of couples inaccessible by earth observations due to differences of magnitudes.

Limiting ourselves to the magnitude 10, we show that the Space Telescope will permit to discoverer mostly close couples with a small difference of magnitude and a short period (P 20 y). They represent several thousands of stars.
Period-K magnitude relations of variable stars in the LMC
Authors: Ita Yoshifusa , Tanabé Toshihiko , Matsunaga Noriyuki , Nakada Yoshikazu ,   The IRSF/SIRIUS team
Published: July 2016

We cross-correlated the OGLE-II database with the SIRIUS JHK survey data in the Large Magellanic Cloud (LMC). After eliminating obvious spurious variables, we determined the pulsation periods for 9 681 stars by applying the Phase Dispersion Minimization (PDM) technique to the OGLE-II data. Based on these data, we studied the period-K magnitude (PK) relations of variable stars in the LMC and found a new sequence. Comparison between the theoretical pulsation model (Wood & Sebo 1996) and observational data suggests that the variable stars on the new sequence are Mira variables pulsating in the first overtone mode.