bluuebunny/crossref_metadata_2025 huggingface dataset:
Detectability of Stellar Companions by Imaging
Authors: Heacox William D. , Gathright John
Published: July 2016

The increasing use of CCD’s and IRCCD’s to detect stellar companions, either by direct imaging or speckle techniques, raises the issue of the fraction of companions whose instantaneous, projected separations lie in the range corresponding to the geometric limits of the detector. The issue is of especial importance to recent surveys employing IRCCD detectors of relatively very small area (projected onto the sky). The distribution of observed separations reflects not only that of orbital semi-major axes, but also distributions of distances to binary systems, orbital eccentricities, tilt of orbital planes with respect to the plane of the sky, and of arguments of periastron. Proper inference of, e.g., binary multiplicity requires estimates of completeness that should incorporate contributions from all these factors.
The Stellar Luminosity Function and Binary Stars
Authors: Kroupa Pavel , Tout Christopher A. , Gilmore Gerard
Published: July 2016

If all stars within a small volume surrounding the sun are counted we obtain an approximation of the low-mass single-star luminosity function. Alternatively, deep photographic surveys cannot resolve most of the binary systems, and consequently we obtain an approximation to the system luminosity function. Comparing the single-star and system luminosity functions we derive the stellar mass function and constrain the properties of binary systems.
Astrometry and Spectroscopy as Tools Toward Visual-Binary Masses
Authors: Heintz W.D.
Published: July 2016

Following the diversified topic of this conference, let me present a variety of comments — not all new, but resulting from a long string of stars drifting across the desk. The chase after visual orbital elements is not exactly a self-purpose but is aiming at further data, in particular, at good masses. The last published lists of high-quality mass determination represent the status of 20 years ago; but a compilation at this time would probably not last long as the progress promises to quicken.

We have 1000 positional (visual/photographic/speckle) orbits, among them about 700 acceptable in the range from fair to definitive. Yet less than 10% of them give good component masses. Most of them are outside the range of parallax measures with the requisite, high precision (that unfortunatly holds for the Hyades); some frustrate the parallax measurer by displaying wedge– and peanut–shaped images, and the more exciting cases of abnormal, non-main–sequence components often cannot get good mass ratios owing to large distances or long periods.
Visual Double Star Catalogs — Past, Present, and Future
Authors: Worley Charles E.
Published: July 2016

The first lists of visual double stars were published by Mayer and Herschel in the late 18th century, but only sporadic lists and catalogs appeared during most of the following century, until Burnham began the systematic collection of such data, which has continued to this day. This contribution discusses the evolution of the visual double star data base over the last centuries and suggests how the data might be ordered to serve future needs.
Systematic Errors in Double Star Observations
Authors: Douglass Geoffrey G. , Worley Charles E.
Published: July 2016

We have examined the visual and speckle observations of visual double stars made by 31 experienced observers in order to evaluate possible systematic errors in these series. Using 57 “definitive” orbits, we find no appreciable errors in position angle. We do find systematic effects in separation for some observers, and, in particular, a “proximity” effect for measurements of pairs closer than 0″.5.

Root-mean-square residuals are:
Very Wide “Visual Double Stars” for the Astrometric Calibration of CCD’s
Authors: Geffert M. , Sinachopoulos D. , Guibert J.
Published: July 2016

We present first results of a catalogue of standard double stars for the astrometric calibration of CCD’s. The data were taken from photographically determined precise positions and proper motions of stars in the region of radio sources and open clusters. In this report, we give preliminary results of stars in the region of 3C 273 and NGC 1647.
Determination of Visual Binary Orbits from Short–Arc Observations Using the Method of Apparent Motion Parameters
Authors: Kisselev A.A.
Published: July 2016

The key formulae of the AMP–method for deriving the orbital elements of wide visual double stars are considered. The usual astrometrical observational data must be supplemented with the values of radius of curvature of observed arc of the binary, its trigonometric parallax and the astrophysical data: the sum of the mass of the components and their relative radial velocity. Thus, the orbital elements can be derived on the basis of short–arc observations.
Cepheid Binaries — an Up-to-Date List
Authors: Szabados L.
Published: July 2016

Cepheid variables are exceptionally useful objects for astrophysics and cosmology but at the same time these stars are normal as far as their duplicity is regarded. A brief summary is given on the relevant data of the known spectroscopic-binary Cepheids and other potential binary Cepheids, duplicity of which is suspected
on the ground of various photometric methods.
The European Network of Laboratories: Visual Double Stars
Authors: Oblak E. , Argue A.N. , Brosche P. , Cuypers J. , Dommanget J. , Duquennoy A. , Froeschle M. , Grenon M. , Halbwachs J.-L. , Jasniewicz G. , Lampens P. , Mermilliod J.C. , Mignard F. , Sinachopoulos D. , Seggewiss W. , Van Dessel E.
Published: July 2016

The study of double stars has since long been recognized as a basic key to the understanding of star formation and stellar evolution. Moreover, close visual double stars have always been systematically neglected in photometric observational programmes although they contain an important part of physically associated systems. It is then timely to organize major observational programmes of these objects for a number of good reasons:

1.

The frequency of double stars is continuously reviewed and the rate of their detection is steadily increasing — both from ground–based and space observations — in such a way that they no longer can be discarded in any models of galactic structure;

2.

Space observations (HIPPARCOS, HST) significantly improve the quality and the importance of stellar samples and permit to better take into account some of the selection effects;

3.

The high–quality astrometric (and also photometric) data that will be provided for such systems by the space observations should be matched with accurate and homogeneous complementary astrophysical information such as colour indices and spectral classification. Such information for close visual double stars is unfortunately almost non-existent but are now being more easily accessible with the use of CCD detectors.
Twenty Years of Speckle Interferometry
Authors: Hartkopf William I.
Published: July 2016

The purpose of my talk is to briefly review the results of two decades of astrometric research using the technique of speckle interferometry. Although speckle, invented by Labeyrie in 1970 (Gezari et al. 1972), is the most well–known and widely–used interferometric technique in the visible and near infra-red, it neither the only technique in use, nor was it the first. Karl Schwarzschild made the first interferometric measurements of binary stars in 1895, using the then–new technique of Michelson interferometry and following a suggestion by Michelson himself that his technique was amenable to binary star astrometry. From 1919 to 1921, Anderson (1920) and Merrill (1922) made a series of measurements of Capella and other bright stars, using a Michelson interferometer of 20-foot baseline, mounted on the Mount Wilson 100-inch. These early measurements have definitely stood the test of time. Figure 1 shows a recently calculated orbit of Capella (Bagnuolo & Hartkopf 1989), using data spanning some 250 full revolutions. Anderson and Merrill’s measurements agree beautifully with observations made 7 decades later. As a result, Capella has probably the most accurately known orbit of any visual binary. Orbital elements calculated in 1981 (McAlister 1981) and again 10 years later differ in period by about 14 seconds, or less than 2 parts per million!
Sub-Milliarcsecond Binary Star Astrometry
Authors: Pan Xiaopei , Shao Michael , Mark Colavita M.
Published: July 2016

Long–baseline optical interferometry has revolutionised binary star astronomy. This paper reviews some recent binary star work done using the Mark III Stellar Interferometer. For the first time, many spectroscopic binaries, eclipsing binaries, triple systems, and binaries with X-ray sources have had their visual orbit, diameter of the primary component, and color index determined. Also, accurate stellar masses, distances, radii, and effective temperatures have been derived. A preliminary distance to the Hyades cluster has also been determined. In addition, preliminary observations provide evidence of a third body in the binary star system ζ Her, which may resolve an 85-year old discrepancy in astronomy.
Interferometric Imaging of Nearby Low–Mass Spectroscopic Binaries. II. ESO Observations
Authors: Perrier C. , Duquennoy A. , Mariotti J.-M. , Mayor M. , Morbey C.
Published: July 2016

We present a preliminary report on infrared interferometric observations, with emphasis on the resolved nearby sources Gl 563.4, Gl 570B and Gl 773.3. We briefly discuss their individual masses inferred from the combination of spectroscopic and visual data.
Mira’s Companion(s)
Authors: Karovska M.
Published: July 2016

Recent high–angular resolution speckle interferometry measurements of the positions of Mira’s companion are presented in context of the previous visual observations. The analysis of the separation measurements since 1923 show evidence for possible third body in the system.
Speckle Data in the New Bright Star Catalogue
Authors: Warren Wayne H. , Hoffleit Dorrit
Published: July 2016

The new fifth edition of the Bright Star Catalogue (BSC5) will include speckle interferometric data in specially allocated columns of the main catalog. Speckle observations have already been included for some 1,800 “bright” stars and more are expected from recent sources. In addition to the separations for resolved pairs, upper limits will be included for stars that have not been resolved. This paper describes how the speckle data have been incorporated into the catalog and gives examples of the new format.
Secondary Spectrophotometric Standards: Results and Future Observational Programme
Authors: Glushneva I.N.
Published: July 2016

Three sets of spectrophotometric standards are presented: eight bright B and A stars of 00 - 265, fourteen B - A stars of 3m-4m from the catalogue of 238 secondary spectrophotometric standards and 24 A0-G0 stars of 7m-8m. For all of these stars UBV photometry was produced and brightness variations exceeding O01 were not found.
New Techniques
Authors: Tinbergen Jaap
Published: July 2016

Routine millimagnitude photometry may require a new approach to reduction of photometric errors. Such an approach is outlined in this paper; it stresses elimination of each error as close to its source as possible. The possibilities provided by modern technology are reviewed in this light. An engineering design group dedicated to photometry is a prerequisite and an on-site photometric technician may be necessary. In this concept, observers are mainly remote users of a database. Implied is the idea of accurate photometry necessarily developing into a single but multi-site astronomical facility (cf. VLBI) and the communal discipline that goes with it.
The Strömgren Automatic Telescope
Authors: Florentin-Nielsen Ralph
Published: July 2016

Copenhagen University Observatory operates a 52cm Cassegrain telescope at ESO, La Silla (Chile) for photoelectric photometry in a completely automatic mode. Alternatively, the telescope may be operated, remotely, from Europe. We report on the operational experience from more than four years of successful use and on the decision by ESO to establish a similar system on their photometric telescope.
Archiving of photometric data
Authors: Hauck B.
Published: July 2016

Lausanne University’s Institute of Astronomy has been collecting stellar photometric data since 1970. Our collection contains data for some 170,000 stars in 78 photometric systems. This database has been used in various applications: comparison of systems, Hipparcos Input Catalogue, studies of star samples, etc. With CCD detectors we are facing a new challenge, since a great deal of information is obtained, mainly for star clusters. But unfortunately, a policy for archiving these data has not yet been established. This is an urgent problem to solve, all the more so as in many cases only a part of the data is published. A solution to this problem is discussed here.
Photometry with CCDs
Authors: Walker Alistair R.
Published: July 2016

Characteristics of telescopes, photometers, CCDs and data acquisition systems relevant to achieving high quality photometry are discussed.
Tycho Photometry: Calibration and First Results
Authors: Großmann V.
Published: July 2016

The star mappers on board the ESA Hipparcos satellite will be used as one part of the Tycho project to obtain photometric data of a quasi B and V band magnitude for the 500,000 brightest stars and one broad-band magnitude T for a further 500,000 stars. Approximately 150 million single observations of these stars will be collected during a 4.5-year mission of the satellite.

The accuracy of the photometric data gained is expected to be 0.03 mag on the average at B = 10.5 mag for non-variable stars. We shall get T magnitudes for stars down to a limiting magnitude of about B = 12 mag depending on the galactic latitude. We will give an overview of the calibration procedure and present some of the first results.
Stellar Photometry with the Optical Monitors
Authors: Antonello E. , Cropper M.
Published: July 2016

The Optical Monitors are small optical telescopes which will fly on board of the X-ray satellites SPECTRUM-X-GAMMA (JET-X experiment) and XMM. Their main scientific applications are the simultaneous observations (imaging) in the optical and UV band of the optical counterparts of X-ray sources, with limiting magnitudes of about mv=22 (JET-X) and 24 (XMM). The OMs are developed in order to perform also serendipitous observations with high photometric precision of bright stars falling in the field of view, which should allow the detection of stellar microvariability at a level better than 10−5. The main characteristics of the instruments are presented and the problems to be solved in order to reach the scientific goals are briefly discussed.
High-Precision Photometry with Small Telescopes on the Moon
Authors: Zeilik Michael
Published: July 2016

I explore the scientific gains that can be achieved by siting small (1 to 2-meter), special-purpose telescopes on the moon with the goal of high- precision observations.
Individual Light Curve Fits of SN la and H0
Authors: Höflich P. , Müller E. , Khoklov A.
Published: July 2016

In order to study the question whether the appearance of SNIa should be uniform from theoretical point of view, we present light curves (LC) for a broad variety of models using our elaborated LC scheme, including implicit LTE-radiation transport, expansion opacities, MC-γ transport, etc. For more details see Khokhlov (1991), Höflich et al. (1992), Höflich et al. (1993), Khokhlov et al. (1993), and Müller et al. (1993).

We consider a set of 19 SNIa explosion models, which encompass all currently discussed explosion scenarios. The set consists of three deflagration models (DF1, DF1MIX, W7 o), two detonation models (DET1, DET2 *), two delayed detonation models (N21, N32 •), detonations in low density white dwarfs (CO095, CO10, CO11 *), six pulsating delayed detonation models (PDD3, PDD5-9 Δ) and three tamped detonation models (DET2ENV2, DET2ENV4, DET2ENV6 Δ). We also included the widely-used deflagration model W7 of Nomoto et al. (1984)
Spectrophotometry of SN 1987A from the Kuiper Airborne Observatory
Authors: Wooden Diane H.
Published: July 2016

Explosion calculations of SN 1987A generate pictures of Rayleigh-Taylor fingers of radioactive 56Ni (56Ni → 56Co → 56Fe) which are boosted to velocities of several thousand km s-1. From the KAO observations of the mid-IR iron lines, a picture of the iron in the ejecta emerges which is consistent with the ‘frothy iron fingers’ having expanded to fill about 50% of the metal-rich volume of the ejecta (vm ≤ 2500 km s-1). The ratio of the nickel line intensities I([Ni I]7.5µm)/I([Ni II]6.6µm) yields a high ionization fraction of xNi ≥ 0.9 in the volume associated with the iron-group elements at day 415, before dust condenses in the ejecta.
A Determination of the Properties of the Peculiar SNIa 1991T through Models of its Early-time Spectra
Authors: Mazzali Paolo A. , Danziger I. J.
Published: July 2016

A series of early-time optical spectra of the peculiar SNIa 1991T, obtained from 2 weeks before to 4 weeks after maximum, have been computed with our Monte Carlo code.

The earlier spectra can be successfully modelled if 56Ni and its decay products, 56Co and 56Fe, dominate the composition of the outer part of the ejecta. This atypical distribution confirms that the explosion mechanism in SN 1991T was different from a simple deflagration wave, the model usually adopted for SNe Ia.

As the photosphere moves further into the ejecta the Ni Co Fe fraction drops, while intermediate mass elements become more abundant. The spectra obtained 3–4 weeks after maximum look very much like those of the standard SN Ia 1990N. A mixed W7 composition produces good fits to these spectra, although Ca and Si are underabundant. Thus, in the inner parts of the progenitor white dwarf the explosion mechanism must have been similar to the standard deflagration model.

The fits were obtained adopting a reddening E(B – V) = 0.13. A Tully-Fisher distance modulus μ = 30.65 to NGC 4527 implies that SN 1991T was about 0.5 mag brighter than SN 1990N. At comparable epochs, the photosphere of SN 1991T was thus hotter than that of SN 1990N. The high temperature, together with the anomalous composition stratification, explains the unusual aspect of the earliest spectra of SN 1991T.

The model results allow us to follow the abundances as a function of mass. In particular, spectroscopic evidence is found that about 0.6M⊙ of 56Ni must have been synthesized in the outermost 1M⊙ of the exploding white dwarf. This implies that almost twice as much 56Ni was produced in SN 1991T than in normal SNe Ia, and explains the unusual brightness of this SN.
The SN1987A Environment
Authors: Wang Lifan , Wampler E. Joseph
Published: July 2016

The environment of the SN1987A is quite complex but also very regularly structured. Detailed analyses of direct images taken under good seeing conditions (0.3—0.8 arcsec) from the European Southern Observatory (ESO)'s New Technology Telescope (NTT) show that there are two nebular loops within the 3 arcsec environment of the SN. The inner loop is elliptical in shape. The kinematics of this loop as revealed by spectroscopic data with a spectral resolving power λ/Δλ « 30 000 provide further clues for the three dimensional structure of these two loops. The data show that the overall structure of the nebulosity can be understood by an hourglass-shaped shell with significant mass enhancement on its equatorial plane. A diffuse nebulosity called Napoleon's Hat is observed at a distance of about 5 arcsec to the north of the SN. It showed little size evolution since the first observation on Aug. 1989, until it disappeared on Jan, 1992. The Napoleon's Hat nebula appears to be a bow-shock coming from an interaction between the supernova progenitor's stellar wind and the interstellar medium, as the supernova progenitor moved through the interstellar medium with a velocity of around 5 kms-1. On an even larger scale, there is a huge dark bay of size around 100 arcsec in diameter, we suggested that this bay was also formed by interactions between the supernova progenitor and the interstellar medium.

The narrow emission lines indicate that the electron density and temperature of the emission gas in the loops are steadily decreasing. However, the temperatures inferred from the [OIII] nebular lines remained persistently higher than 2 × 104K. They were around 104cm−3 and 2 × 104K on Aug. 30, 1990. In addition, a global difference in the electron density of the two major axis of the inner loop is observed in the images and spectra taken five years after the supernova explosion. We have also studied the two neighboring stars surrounding the supernova. We find that star 2 is a B star with Hα and Hβ emission lines.

The supernova circumstellar nebulosity is remarkably similar to certain types of planetary nebula, e.g. NGC2392. Asymmetric wind interaction models for the formation of planetary nebula are applied to produce a model in the form of an hourglass shaped shell. This model invokes both a slow wind while the star was in its red supergiant phase and a fast wind during the later blue supergiant stage before explosion. Although such wind interaction models fit the observed nebular structures satisfactorily, they are so idealized that they tell us little about the origin of the seed asymmetry or the amount of seed asymmetry needed to produce the observed real nebula.
Radio Emission from Supernova Remnants
Authors: Strom Richard G.
Published: July 2016

Most of the supernova remnants known in the Galaxy have only been detected at radio frequencies. The reason for this is absorption in the Galactic plane at both optical and X-ray wavelengths. All available evidence suggests that the shock fronts which accompany supernova remnants accelerate enough cosmic rays to GeV energies to produce readily detectable radio emission. This is fortunate, for it enables us to study remnants throughout the Galactic disk, although existing catalogues may be anywhere from 50 to 90 % incomplete. Cosmic rays and the magnetic fields in which they gyrate are the essential ingredients for producing the synchrotron radiation which is observed at radio frequencies. Various methods for estimating magnetic field strengths can be applied to a small number of remnants, and produce values not far from those based upon equipartition between the energy contents of particles and fields. From this, the particle energy content is derived for a number of objects.
Red Dwarf Masses
Authors: Heintz Wulff D.
Published: July 2016

When a project finds enough material from the brighter stars, without high demands on instruments and observing effort, so much the better. But the very red dwarf stars certainly are not in that category. To show how limited the knowledge still is: Assume optimistically that the star count to 5 pc is complete. Extend the distance merely to 7 or 8 pc, i.e., scan a 3 or 4 times larger volume, and the present count is already short by several dozens of stars—practically the entire dM5–M8 range.

At these objects—with very little luminosity in the visible range—the observationally accessed relationship between mass and luminosity ends, and the peak in the luminosity function need not mean a peak of the mass-frequency function.
First Orbits for New Pairs
Authors: Muller P.
Published: July 2016

The discovery of new pairs in a given class of separation normally brings new orbits; the problem is to know how the number of such orbits will increase with time from the discoveries. A study of the Lick stars (A and Hu) leads to an estimate of the future of Nice pairs in this respect and could also give some idea of what to do with discoveries made from space vehicles.
A Systematic Review of Aperture Shapes
Authors: Schultz A. B. , Frazier T. V.
Published: July 2016

This paper discusses the application of apodization to reflecting telescopes. The diffraction pattern of a telescope, which is the image of a star, can be changed considerably by using different aperture shapes in combination with appropriately shaped occulting masks on the optical axis. Aperture shapes studied were the circular, square, and hexagonal. Polaris (α-UMin) was used as the test system.
New Method for Measuring Photographic Binaries
Authors: Pannunzio R. , Scardia M.
Published: July 2016

Preliminary results of a new photographic technique applied to visual double stars are given.

This technique consists in the determination of the ϱ, θ and Δ m from measurements made on two pairs of trails left by the components of a binary on a photographic plate, obtained through an adequate movement of the telescope in R.A. and declination.
Blended Visual Binaries as Tests of Low Amplitude Orbit Detection and Determination Capability in Long-Focus Photographic Astrometry
Authors: Lippincott Sarah Lee , Hershey John L.
Published: July 2016

Photocentric orbital motions from 60-year Sproul plate series are shown for three visual binaries, ζ Her, 85 Peg and Ho 296. Mass ratios of the first two pairs, which have large-amplitude blended orbits, carry internal errors at the level of one percent. Orbital elements computed independently from the blended photographic observations agree closely with the well-determined visual orbits. Ho 296 serves as a test of the Sproul plate series to detect a 20-year orbit with an amplitude of two, or one, micron. Simulations of orbital motion in single star residual series confirm this detection capability, which corresponds to planetary mass for dark objects around nearby stars. A mass-luminosity diagram of the lower main sequence is shown, including one for invisible astrometric companions.
Accuracy of Spectral Classification
Authors: Abt Helmut A.
Published: July 2016

A knowledge of the spectral types of visual components is still basic to most intensive studies of visual systems. Although there are photoelectric techniques that give good quantitative information on certain classes of stars, the only way at present to identify most classes of stars, from mercury-manganese stars to barium stars, is by obtaining their spectra. The spectra can be obtained from objective prisms, slit spectrographs, or spectrum scans, but the important things are that they (1) show a large portion of the spectra, preferrably in the blue-violet for most classes of stars, (2) have sufficient resolution and signal-to-noise to identify many spectral lines, and (3) be standardized as an independent system. The last is important because if spectral type standards are changed so that they will agree with other information, such as colors, we lose the benefits of a comparison, such as deriving interstellar reddening.
The Detection of Triple Systems Through the Precession of the Nodes Effect
Authors: Mazeh T. , Mayor M.
Published: July 2016

This paper is a report on a new technique for detecting close triple stars and on a current observational project with some preliminary results, using this method. The goal of the project is to discover new triple systems where the ratio between the long and the short orbital period is small. A system will be called a close triple system if its short orbital period is of several days.

In most of the known triple stars (Fekel 1981), the period ratio is very large. This can be attributed to the fact that the wide orbit has been detected visually in most cases. In the few exceptions (e.g. λ Tau, Ebbighausen and Struve 1956), the wide orbit was discovered by detecting additional periodicity in the derived velocity of the close pair mass center γ As this small modulation is imposed on the large radial velocity variation associated with the orbit of the close pair, many triple systems could have escaped this kind of detection. Consequently, the present typical or averaged period ratio might be highly overestimated.
Speckle Interferometry and Speckle Holography; Techniques and Limitations
Authors: Weigelt Gerd
Published: July 2016

We discuss speckle interferometry and speckle holography measurements of double and triple stars. Speckle holography with the ESO 3.6m telescope yielded direct images with a resolution of 0.03 arc second (diffraction limit). Finally we discuss the speckle rotation method, which can be used to reconstruct high-resolution images from Space Telescope data.
Double Star Measurement with the Cerga Two Telescope Interferometer
Authors: Koechlin L. , Vakili F. , Bonneau D.
Published: July 2016

The CERGA interferometer is made of two 25 cm aperture telescopes with a variable north-south baseline, spanning from 5.5 to 35 meters. In addition to stellar diameters, it has provided binary stars measurements with a 0.5 milliarcsecs precision for separation down to 2.5 milliarcsoconds (Labeyrie 1971).

The visual limiting magnitude is presently 3.5. Large separation binaries will be observed with one milliarcsecond precision using a slightly different technique. This should provide a mean of detecting possible planetary induced orbital perturbations.
An Image Reconstruction for Capella with the Steward Observatory/AFGL Intensified Video Speckle Interferometry System
Authors: Cocke W. J. , Hege E. K. , Hubbard E. N. , Strittmatter P. A. , Worden S. P.
Published: July 2016

In the decade since its invention by Labeyrie in 1970, speckle interferometric techniques have evolved from simple optical processing of photographic images to high-speed digital processing of quantum-limited video data. This progress has been summarized in preceeding papers by McAlister and Weigelt in this colloquium.

The basic hardware of our system has been described in Hubbard, et al. (1979 – The basic speckle camera) and in Hege et al. (1980 – The intensified video system). These capabilities have been successfully applied to observations over a dynamic range of 16 magnitudes, from Betelgeuse (Goldberg, et al. 1982) and Capella (this paper), at one extreme, to Pluto/Charon (Hege, et al. 1981a) and the 16th magnitude resolved QSO system PG1115+080 (Hege, et al. 1981b) at the other. To accomodate this dynamic range two distinct data-recording/data-processing modes have been implemented. The Analoue mode records the image intensity for each pixel in the speckle interferogram. This is applicable for objects brighter than 7th to 10th magnitude, depending upon telescope aperture, observing band-pass and detector image scale. For fainter objects the Event mode records individual photoelectron addresses in the speckle interferogram.
Recovery of Intensity Information from Speckle Data
Authors: Hege E. K. , Hubbard E. N. , Cocke W. J. , Strittmatter P. A. , Worden S. P. , Radick R. R.
Published: July 2016

The achievements of speckle interferometry in recovering diffraction limited spatial information, primarily by optical processing of photographic data, have been well summarized by McAlister in a preceeding paper. In general, the recovery of intensity information has received less attention mainly because of complications such as the need for accurate deconvolutions and noise bias corrections.

Methods for producing image power spectra (or the equivalent image autocorrelation functions) from digitally recorded speckle interferograms, as well as methods for correcting these functions for seeing effects, are described in our previous paper, Cocke, et al. in this colloquium. In this paper we discuss effects of instrumental response and photon statistics, the so-called noise bias, and procedures for correcting these effects in order to recover binary star relative intensity information from speckle interferometric data. We find for Capella δmv = 0.48.
The Reconciliation of Visual and Spectroscopic Observations of Binary Systems
Authors: Batten Alan H.
Published: July 2016

The special problems presented to the computer of orbits by radial-velocity observations of visual binaries are discussed under three heads: (i) problems caused by the small range of velocity variation, (ii) problems caused by the long periods, (iii) inconsistency between visual and spectroscopic observations. It is pointed out that radial-velocity observations, even when they are insufficient for independent determinations of orbital elements, impose constraints on possible values of those elements which may in fact be helpful to the computer of visual orbits. In particular, as is illustrated by reference to ADS 8189, even a few observations of the radial-velocity are sufficient to destroy the mutual independence of the elements e, and ω.
Fourier Techniques for Binary Star Orbit Determination
Authors: Monet David G.
Published: July 2016

The use of the Fourier transform in the computation of binary star orbits has many advantages over traditional (configuration space) analysis. The method can be applied to visual, spectroscopic and astrometric binaries, as well as to visual binaries where only the separation or position angle is known. While this technique requires the use of a digital computer, the algorithms for implementation of the solutions for the various types of binary star motion are quite similar. A description of the implementation of the astrometric binary solution will be presented along with a discussion of the various estimators for the significance of the derived orbital elements obtained in the course of the solution. If time permits, a summary of some Monte Carlo investigations of the effects of observational noise and temporal sampling on the derived orbital elements will be presented.
Programmes for Computing Visual Binary Orbits from Three Fundamental Points and the Apparent Areal Constant (*)
Authors: Nys O.
Published: July 2016

A complete overview on the programmes that are used at the Royal Observatory of Belgium, for conducting the computation of the orbit of a visual binary based on three fundamental points and the apparent areal constant is given. They include the necessary investigations of all incompatibilities that may be encountered during the computation, for instance - when resolving the Thiele-van den Bos equations – the recognition of the nature of the solution (elliptic, parabolic or hyperbolic) and the identification of trivial solutions. Some particular computations are made when necessary, for guidance to the best choice of the three fundamental points and the areal constant.
Red variables in the OGLE-II database: first results for the LMC
Authors: Kiss L.L. , Bedding T.R.
Published: July 2016

We present a period analysis of more then 23 000 red giants in the Large Magellanic Cloud observed by the OGLE-II microlensing project. Periods combined with the single-epoch 2MASS J H KS magnitudes revealed the complex distributions of stars in the period-luminosity plane. Besides four different sequences corresponding to different modes of pulsation in AGB stars, we also discovered two distinct and well-separated sequences below the tip of the Red Giant Branch, consisting of almost 10000 short-period and low-amplitude red variable stars. We propose that the majority are likely to be first ascent red giants, showing radial pulsations in the second and third overtone modes.
Distance scale, variable stars and stellar populations in Local Group galaxies
Authors: Clementini G. , Baldacci L. , Bragaglia A. , Carretta E. , Di Fabrizio L. , Gratton R.G. , Greco C. , Gullieuszik M. , Held E.V. , Maio M. , Marconi M. , Matonti F. , Momany Y. , Poretti E. , Rizzi L. , Saviane I. , Taribello E.
Published: July 2016

We present an overview of our study of the short period variable stars in the Large Magellanic Cloud, and in the dwarf galaxies Fornax, Leo I, and NGC 6822. Light curves are presented for RR Lyrae stars, Anomalous Cepheids and, for the first time, for Dwarf Cepheids in the field and in the globular cluster #3 of the Fornax galaxy.
Variable star monitoring in local group dwarf irregular galaxies
Authors: Snigula Jan , Gössl Claus , Hopp Ulrich , Barwig Heinz
Published: July 2016

Dwarf galaxies in the local group provide a unique astrophysical laboratory. Despite their proximity some of these systems still lack reliable distance determinations as well as studies of their stellar content and star formation history. We present first results of our survey of variable stars in a sample of six local group dwarf irregular galaxies. Taking the Leo A dwarf galaxy as an example we describe observational strategies and data reduction. We discuss the light curves of two newly found Cepheids and place them into the context of a previously derived P-L relation. Finally we discuss the LPV content of Leo A.
RR Lyrae variables in globular clusters and nearby galaxies
Authors: Catelan M.
Published: July 2016

I point out that the Oosterhoff dichotomy for globular cluster and field RR Lyrae stars may place the strongest constraints so far on the number of dwarf spheroidal-like protogalactic fragments that may have contributed to the formation of the Galactic halo. The first calibration of the RR Lyrae period-luminosity relation in I, J, H, K taking evolutionary effects into account is provided. Problems in the interpretation of RR Lyrae light curves and evolutionary properties are briefly reviewed.
WWW-Based Fourier coefficient database – A status report
Authors: Morgan Siobahn M.
Published: July 2016

The status of the WWW-based Fourier Coefficient web site is presented. Currently the database has coefficients for not only galactic field variables, but also those found in globular clusters and other galaxies, including the Magellanic Clouds. The database can be used to show various correlations between physical characteristics of the stars and the coefficients, as well as inter-relationships between the coefficients themselves. The database is accessible at http://nitro9.earth.uni.edu/fourier/.
Asteroseismology of the β Cep star ν Eri: initial results
Authors: Handler G. , Aerts C. ,   an international team of 50 astronomers
Published: July 2016

We have acquired about 1200 hr of both spectroscopic and photometric measurements of the β Cep star ν Eri with 22 telescopes around the world, detecting and identifying seven independent pulsation modes. They are the radial fundamental mode, an l = 1, g1 triplet, an l = 1, p1 doublet and an l = 1, p2 singlet. Seismic model calculations by two independent teams suggest that it is not possible to explain the pulsational behaviour of ν Eri with standard stellar models. Some modifications of the input physics are required.
Mode Selection Mechanism in B-Type Pulsators: Observational Clues
Authors: Jerzykiewicz Mikołaj
Published: July 2016

Linear nonadiabatic calculations for models of B-type pulsators predict many more unstable modes than actually observed, therefore a mode selection mechanism must operate in these stars. To investigate this problem quantitatively, available data for singly-periodic and multi-periodic β Cephei variables are compared. No clear-cut differences are found. The slight difference in [m/H], noted recently by Daszyńska et al. (2003), may indicate the solution.
Nonadiabatic observables in main sequence δ Scuti stars
Authors: Moya A. , Garrido R. , Dupret M.-A.
Published: July 2016

Using a theoretical nonadiabatic pulsation model, phase differences and amplitude ratios between the relative effective temperature variation and the relative radial displacement have been calculated. These quantities, when compared with photometric observations in different colours, provide an efficient instrument for mode identification, the first step to understand the internal structure of the stars. The theoretical results presented in this paper show a dependence for δ Scuti stars on the mixing length parameter α used to treat the convection using the standard Mixing Length Theory. The nonadiabatic pulsational code developed here includes the pulsation-atmosphere interaction as described by Dupret et al. (2002). The equilibrium models are provided by the CESAM evolutionary code, where a complete reconstruction of non-grey atmospheres (Kurucz models) is included.
Line profile variations in γ Equ: A puzzle
Authors: Shibahashi Hiromoto , Kurtz Don , Kambe Eiji , Gough Douglas
Published: July 2016

Line profile variations in γ Equ show the classic blue-to-red travelling bumps of m-modes resolved by rotation, and they have been identified as l = 2 or 3, m = −l or −l + 1 by characterising the line shapes using the moment method. The mode identifications cannot be correct, however, since γ Equ is an extremely slowly rotating star (Prot > 70 yr). We propose an alternative interpretation, according to which the observed line profile variations are a manifestation of a shock wave in the high atmosphere near the magnetic polar regions; the oscillation mode is then still consistent with the photometric observations.
Properties of AGB variables in the intermediate-age cluster NGC 419 in the SMC
Authors: Tanabé Toshihiko , Ita Yoshifusa , Matsunaga Noriyuki , Nakada Yoshikazu ,   IRSF/SIRIUS team
Published: July 2016

We found that the OGLE database contains most AGB stars associated with the SMC cluster NGC 419. Combining these data with our near-infrared (NIR) data, we obtained the following results: 1) Almost all AGB stars above the TRGB are variables. 2) Large amplitude variables tend to show more regular light curves. 3) Only the tip AGB stars (in this case, carbon stars) increase their amplitudes with their J – K colors and only the most evolved ones can become large amplitude (Mira-like) variables. 4) AGB variables may explain the sequences found by Wood et al. (1999).
Red supergiants in the Small Magellanic Cloud: The effects of metallicity on narrow-band classification indices
Authors: Wing Robert F. , Walker Kyle M. , Jack MacConnell D. , Costa Edgardo
Published: July 2016

Narrow-band classification photometry, on a six-color system that measures near-infrared bands of TiO and CN, has been obtained for a set of red supergiants in the Small Magellanic Cloud. To investigate the effects of metallicity on the band-strength indices, comparisons are made to supergiants in the LMC and the Galaxy. Two new variable stars are reported.
The long secondary periods in semi-regular variables
Authors: Wood P.R. , Olivier A.E. , Kawaler S.D.
Published: July 2016

About 25% of variable asymptotic giant branch stars in the LMC have light curves that are modulated by a long secondary period of length ~ 1–4 yr. Solar-vicinity analogs of these stars show radial velocity curves that are asymmetric and of small amplitude (~3–5km s−1). Possible explanations for the photometric and radial velocity variations include: eccentric motion of an orbiting companion of mass ~0.1 M⊙; radial and nonradial pulsation; rotation of an ellipsoidal-shaped red giant; episodic dust ejection; and star spot cycles. We find that there are severe difficulties with each of these models. Thus, the long secondary periods are the only unexplained type of large-amplitude stellar variability known at this time.
The First Theoretical γ Doradus Instability Strip
Authors: Kaye Anthony B. , Warner Phillip B. , Guzik Joyce A.
Published: July 2016

We present the first theoretical γ Doradus instability strip. We find that our model instability strip agrees very well with the previously established, observationally based, instability strip of Handler & Shobbrook (2002). We stress, as in Guzik et al. (2000), that the convection zone depth plays the major role in the determination of our instability strip. Once this depth becomes too deep or too shallow, the convection zone no longer allows for pulsational instability.
Eigenfunctions of Axisymmetric p-modes in The Presence of A Dipole Magnetic Field: Observational Consequences
Authors: Saio Hideyuki , Gautschy Alfred
Published: July 2016

We calculate the effects of a 3.2-kG dipolar magnetic field on the eigenfunctions of high-order p-mode pulsations and discuss the consequences for pulsation amplitude modulation with rotation phase and for line profile variations.
Nonradial Pulsations in Classical Cepheids of The Magellanic Clouds
Authors: Moskalik Paweł , Kołaczkowski Zbigniew , Mizerski Tomasz
Published: July 2016

We have performed systematic frequency analysis of the LMC Cepheids observed by OGLE project. Several new types of pulsation behaviour are identified, including triple-mode and amplitude-modulated double-mode pulsations. In ~ 10% of the first overtone Cepheids we find low amplitude secondary periodicities corresponding to nonradial modes. This is the first evidence for excitation of nonradial oscillations in Classical Cepheid variables.
The Galactic Cepheid Period-Luminosity Relation from Hipparcos Parallaxes and Proper Motions
Authors: Heacox William D.
Published: July 2016

A Bayesian model of Cepheid kinematics has been applied to the Hipparcos parallaxes and proper motions to obtain an independent estimate of the Galactic Cepheid Period-Luminosity relation for visual magnitudes. The resulting estimate includes a slope that differs significantly from those of Magellanic Cloud Cepheids, suggestive of a lack of universality amongst galaxies in Cepheid P-L calibration.
Preparing the COROT Space Mission: Building A Photometric and Variability Database of Stars in its Field of View
Authors: Amado P.J. , Garrido R. , Poretti E. , Michel E.
Published: July 2016

The CNES/European space mission COROT will monitor asteroseismic targets located in selected fields to probe stellar interiors. Therefore, suitable candidate targets have to be searched for in order to optimize the scientific return of the mission. However, to be able to use the asteroseismic tools on the stars, their physical parameters must be known in advance. In this work, we detail the process of building a photometric database of all the stars brighter than V = 8.0 in the field of view of COROT and the process of selecting suitable δ Sct and γ Dor-type stars for the mission.

For an optimal selection of the seismology targets (for both COROT programs devoted to asteroseismology, i.e., the core and exploratory ones), it is essential to gather a priori as much information as possible on all potential candidates. With this aim, Strömgren-Crawford uvby-Hβ and Ca II H&K photometry were obtained for all of them. These data have been used to derive estimates of their effective temperatures, surface gravities and metallicities. These observations, together with high resolution echelle spectroscopy and high angular resolution imaging observations, are components of an ambitious ground-based program.
The Reliability of Echelle Spectroscopy in Hot Rotating Star Research
Authors: Škoda Petr , Šlechta Miroslav
Published: July 2016

For hot and rapidly rotating stars, the considerably wide line profile is spread over several echelle orders and thus a precise data reduction before merging several spectral orders together is required to obtain reliable results. As we show, the usage of automatic pipelines or wrong application of general reduction procedures may result in periodic ripple disturbances in the shape of the apparent stellar continuum and by this way introduce considerable errors into the determination of fundamental astrophysical quantities as gravity and mass of the stars.