bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Systematic Review of Aperture Shapes
Authors: Schultz A. B. , Frazier T. V. 
Published: July 2016

AbstractThis 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

AbstractPreliminary 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

AbstractPhotocentric 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.
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

AbstractWe 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

AbstractThe 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

AbstractThe 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.
Programmes for Computing Visual Binary Orbits from Three Fundamental Points and the Apparent Areal Constant (*)
Authors: Nys O. 
Published: July 2016

SummaryA 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

AbstractWe 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

AbstractWe 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

AbstractDwarf 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

AbstractI 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

AbstractThe 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

AbstractWe 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

AbstractLinear 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

AbstractUsing 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

AbstractLine 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

AbstractWe 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

AbstractNarrow-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

AbstractAbout 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

AbstractWe 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

AbstractWe 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

AbstractWe 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

AbstractA 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

AbstractFor 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.
The Masses and Pulsation Modes of Classical Cepheids
Authors: Cox Arthur N. 
Published: July 2016

AbstractRecent general observations pertaining to the masses and pulsation modes of classical Cepheids are reviewed. Certain special ones of these variables that display unusual behavior such as long term amplitude variations, overtone pulsations, and double-mode behavior, including one Cepheid in the first and second overtones as well as those in the fundamental and first overtone, are discussed in some detail. I suggest that the amplitude varying supergiant Cepheid HR 7308, which seems to be pulsating in the second radial overtone, is alternating between states where there is enough helium to barely give kappa and gamma effect driving, and where the helium has settled too deep for this driving. Reestablishment of the helium may be due to rapid levitation of the CNONe elements which cause convection and which then dredge-up the helium again to suppress the convection and also to drive pulsations. The use of Fourier fitting to the light and velocity curves have revealed some features that are interesting and are discussed, such as the pulsation mode discrimination and the derivation of accurate Wesselink radii. The seven methods of determining the masses of these stars are presented with a short critique of each. Evolution and pulsation masses depend on uncertain observed luminosities, and these have been revised recently. Evolution masses also depend on the blue looping yellow giant evolution tracks that may need revision because of convective core overshooting and possible opacity, Z, or Y abundance increases. The most discrepant masses, however, are those that depend on period ratios – the “bump” and “beat” masses. The possibility that the Cepheid internal structure can be modified enough by doubling the material opacity seems unlikely. It is suggested, though, that perhaps the period ratio mass anomaly solution can be found in CNONe element enhancement by radiation absorption levitation that would give higher opacities by abundance effects instead of any revisions in the opacity calculations. Some details for this mass anomaly “solution” are presented.