bluuebunny/crossref_metadata_2025_split huggingface dataset:
Model atmospheres and quantitative spectroscopy of luminous blue stars
Authors: Kudritzki R.P. , Gabler A. , Gabler R. , Groth H.G. , Pauldrach A.W.A. , Puls J. 
Published: July 2016

AbstractThe basic physics of model atmospheres for Luminous Blue Stars (LBS) are discussed. The discussion comprises the model description of both subsonic photospheres and supersonic winds and the application of model calculations for the purpose of quantitative spectroscopy.
A Homogeneous Sample of Binary Galaxies: Basic Observational Properties
Authors: Karachentsev I. D. 
Published: July 2016

AbstractA survey of optical characteristics for 585 binary systems, satisfying a condition of apparent isolation on the sky, is presented. Influences of various selection effects distorting the average parameters of the sample are noted. The pair components display mutual similarity over all the global properties: luminosity, diameter, morphological type, mass-to-luminosity ratio, angular momentum etc., which is not due only to selection effects. The observed correlations must be caused by common origin of pair members. Some features (nuclear activity, color index) could acquire similarity during synchronous evolution of double galaxies.Despite the observed isolation, the sample of double systems is seriously contaminated by accidental pairs, and also by members of groups and clusters. After removing false pairs estimates of orbital mass-to-luminosity ratio range from 0 to 30 f⊙, with the mean value (7.8 ± 0.7) f⊙. Binary galaxies possess nearly circular orbits with a typical eccentrity e = 0.25, probably resulting from evolutionary selection driven by component mergers under dynamical friction. The double-galaxy population with space abundance 0.12±0.02 and characteristic merger timescale 0.2 H−1 may significantly influence the rate of dynamical evolution of galaxies.
Blue Ellipticals in Compact Groups
Authors: Zepf Stephen E. , Whitmore Bradley C. 
Published: July 2016

AbstractWe examine the hypothesis that mergers of spiral galaxies make elliptical galaxies by studying galaxies in compact groups. We combine dynamical models of the merger-rich compact group environment with stellar evolution models and predict that roughly 15% of compact group ellipticals should be 0.15 mag bluer in B – R color than normal ellipticals. The published colors of these galaxies suggest the existence of this predicted blue population, but a normal distribution with large random errors can not be ruled out based on these data alone. However, we have new UBVRI data which confirm the blue color of the two ellipticals with blue B – R colors for which we have our own colors. This confirmation of a population of blue ellipticals indicates that interactions are occurring in compact groups, but a blue color in one index alone does not require that these ellipticals are recent products of the merger of two spirals. We demonstrate how optical spectroscopy in the blue may distinguish between a true spiral + spiral merger and the swallowing of a gas-rich system by an already formed elliptical. We also show that the sum of the luminosity of the galaxies in each group is consistent with the hypothesis that the final stage in the evolution of a compact group is an elliptical galaxy.
The Morphology of Sérsic-Pastoriza Galaxies
Authors: Yates G.J. , Pedlar A. , Saikia D.J. , Unger S.W. , Axon D.J. 
Published: July 2016

AbstractIn this paper we present the preliminary results of our radio-continuum and neutral hydrogen observations of Sérsic-Pastoriza (S-P) galaxies. We show that the central regions contain a population of compact features thought to be young supernova remnants (SNRs) and discuss the overall morphology of the nuclei.
Deep Fabry-Perot Imaging of NGC 6240: Kinematic Evidence for Merging Galaxies
Authors: Hawthorn J. Bland , Wilson A. S. , Tully R. B. 
Published: July 2016

AbstractWe have observed the superluminous, infrared galaxy NGC 6240 (z = 0.025) at Ha with the Hawaii Imaging Fabry-Perot Interferometer (HIFI – Bland and Tully 1989). During the past decade, observational evidence from all wavebands indicates that the unusual appearance of NGC 6240 has resulted from a collision between two gas-rich systems, a view which is supported by our spectrophotometnc data. However, the origin of the enormous infrared luminosity (4 × 1011 L0) detected by IRAS remains highly controversial, where opinions differ on the relative roles of large-scale shocks, massive star formation or a buried “active” nucleus. These mechanisms are discussed in the light of our Fabry-Perot observations.
What Determines The Bulge to Disk Ratio of Galaxies
Authors: Roos Nico 
Published: July 2016

AbstractGalaxies having the same luminosity may have very different bulge to disk ratios, while the mean bulge to disk ratio slowly increases with total luminosity (Schechter and Dressier, 1987, Sandage et al., 1985). Such a behaviour is expected if ellipticals and the spheroidal components of disk galaxies are produced by secondary accretion of galaxies by larger galaxies. This is illustrated using a simple toy model of the evolution of the mass function of galaxies due to galaxy mergers.
Induced Starburst and Nuclear Activity: Faith, Facts and Theory
Authors: Shlosman Isaac 
Published: July 2016

AbstractThe problem of the origin of starburst and nuclear (nonstellar) activity in galaxies is reviewed. A physical understanding of mechanism(s) that induce both types of activity requires one to address the following issues: 1) what is the source of fuel that powers starbursts and active galactic nuclei? and 2) how it is channeled towards the central regions of host galaxies? As a possible clue, we examine the role of non-axisymmetric perturbations of galactic disks and analyze their potential triggers. Global gravitational instabilities in the gas on scales ~ 100 pc appear to be crucial for fueling the active galactic nuclei.
CORAVEL Surveys to Study Binaries of Different Masses and Ages
Authors: Mayor M. , Duquennoy A. , Halbwachs J.-L. , Mermilliod J.-C. 
Published: July 2016

AbstractPreliminary results are given for a systematic survey of K-dwarf stars in the solar vicinity. Nine companions to the G and K dwarfs have very low M2 sin i, less than 0.08 M⊙. These detections from a sample of 540 G and K primary stars support the reality of the existence of companions with mass below 0.08 M⊙: brown dwarfs exist.A comparison of the relative mass function distribution f(m)/M1 between low-mass (M1 < 1.3 M⊙) and intermediate-mass (2 < M1 < 5 M⊙) binaries suggests a dependence of the mass-ratio distribution on the mass of the primary: f(q, M1).By combining the photometric information with orbital elements constraints, we have derived the mass-ratio distribution for intermediate-mass stars. As is the case for low-mass stars, this distribution does not have any maximum close to M2/M1 = 1.
Binaries in the Hyades
Authors: Stefanik Robert P. , Latham David W. 
Published: July 2016

AbstractOrbital solutions are now available for 46 binaries which are members of the Hyades. The distribution of eccentricity versus period shows evidence for tidal circularization of the short-period binaries. However, the transition from circular to eccentric orbits is not clean. The first eccentric orbit has a period of 5.75 days, while the last circular orbit has a period of 8.50 days. For longer periods the distribution of eccentricity is the same as for solar-type stars in the field.
Method for the Calculation of Orbits of Spectroscopic-Interferometric Binaries with Mixed Data
Authors: Lanchares V. 
Published: July 2016

AbstractFrom an initial value of the period and a fitted curve for the radial velocities an homotetic plane to that of the relative orbit is constructed from which i, Ω and parallax are deduced. The remaining orbital elements are obtained from the relations of the elliptical motion.
A Catalogue of Nearby Wide Binary and Multiple Stars
Authors: Poveda A. , Herrera M.A. , Allen C. , Cordero G. , Lavalley C. 
Published: July 2016

AbstractNo modern catalogue of wide binary and multiple systems (WBMS) exists for the region of the solar vicinity (stars nearer than ~22 pc), that include updated information on their membership to moving clusters and an age classification. With the aim of filling this gap, and also because of its importance for investigating the dynamical evolution of double and multiple systems, we have compiled a WBMS list extracted from the catalogues of nearby stars of Gliese (1969, also Gliese & Jahreiss 1979), as well as Luyten’s NLTT (Luyten 1979–1980, Luyten & Hughes 1980, see also Warren et al. 1989), the Bright Star Catalogue (Hoffleit 1982), the catalogue of Woolley et al. (1970) and other sources.By comparing the transverse velocities of WBM systems with those expected for members of the Hyades and Sirius Superclusters, membership of some WBMS to them has been established. We have classified as probably young systems (PYS) those with one component satisfying at least one of various criteria of youth. A system that is not a PYS is classified as probably old (POS).The catalogue contains 385 binaries and 85 systems of higher multiplicity. Out of these, 129 binaries are PYS and 256 are POS, while 32 multiples are PYS and 53 are POS.
Statistics of Double and Multiple Stars in the Solar Neighborhood
Authors: Orlov Victor V. , Titov Oleg A. 
Published: July 2016

AbstractWe study the multiplicity function and physical properties of single, double, and multiple stellar systems in the solar neighbourhood (r < 10 pc), using a new preliminary machine–readable version of the Gliese & Jahreiss Catalogue (1991).The ratio of (n+l)-ple to n-ple systems is a constant fraction of about 1/4 for n =1, 2, 3, 4. The luminosity function f(M) for primaries in binaries has an additional peak at M є (6m,8m) that is absent in f(M) for single stars and secondary components. A significant correlation between the absolute magnitudes M1 and M2 of the components in binaries takes place.
Detection and Measurement of Double Stars with HIPPARCOS: Provisional Results from NDAC
Authors: Söderhjelm S. , Lindegren L. , Van Leeuwen F. , Evans D.W. 
Published: July 2016

AbstractThe HIPPARCOS satellite observes 118,000 stars from a predefined list. Some 10% of these are known doubles or multiples, and another 2—3% may ultimately be found to be non-single with separations above 0″.l and magnitude–differences below 4–5. This paper describes briefly the special reduction methods used by NDAC (Northern Data Analysis Consortium) for treating these non-singles. A key feature is the use of the main reduction results to calibrate and collect the data for individual doubles in ‘case history files’. This enables a global solution of both absolute and relative parameters for a double to be carried out in a single step. Using provisional data tapes covering small parts of a 14-month interval, tests have been made of major parts of the double star reductions. These early results are compared with independent HIPPARCOS data and with ground–based speckle interferometry.
How Double Star Astronomy May Develop After HIPPARCOS
Authors: Dommanget J. , Lampens P. 
Published: July 2016

AbstractNow that the HIPPARCOS satellite safely revolves on its “degraded” orbit — after the exploit of the ESA technicians to rescue it from the faulty ignition of its apogeum boost motor — and regularly provides the information expected for reaching the initial aim of the project, one may turn to examine the possible exploitation of the final HIPPARCOS Catalogue.In the present paper, we describe how double and multiple stars have been introduced in the Input Catalogue and what may be expected from their observation. We also try to evaluate how much the final HIPPARCOS data may influence future researches on these celestial bodies and what kind of ground–based observation programmes should be conducted in order to support the space results.
Differential Speckle Interferometry Applied to Double Stars
Authors: Petrov Romain G. , Lagarde Stephane 
Published: July 2016

AbstractDifferential Interferometry (DI) is the application of high angular resolution interferometric techniques to objects observed simultaneously at different wavelengths. When applied to unresolved double stars it makes it possible to measure the variation of the object photocenter with wavelength, which yields angular and spectral information well beyond the classical resolution limits. Signal–to–noise ratio analysis shows that, if DI experiments are limited by photon and speckle noise, the technique can be applied to a large number of double systems for the measurement of vectorial angular separations and of radial-velocity differences. With 4-m telescopes, there are a few tens of binary systems for which DI should permit the resolution and the measurement of the position angle of the rotation axis of at least one of the components. A preliminary experiment permitted a high SNR resolution of the double star Capella with a 1.52-m telescope and showed the current limitations of DI performances resulting from an imperfect correction of detector geometrical distortions.
Speckle–Spectroscopic Studies of Late–Type Stars
Authors: Tokovinin A. 
Published: July 2016

AbstractThe existing and new observing techniques for combined speckle–spectroscopic studies of binary stars are briefly reviewed. The late–type dwarf stars are particularly rewarding since simultaneous spatial and spectroscopic resolution is possible for a large number of systems. A list of new candidates for the interferometric resolution is given. These studies can make an important contribution to the data on stellar masses and also provide some insight into the binary formation mechanisms when applied to multiple systems.
A Search for Trapezium Type Multiple Systems in T-Associations
Authors: Salukvadze G. N. 
Published: July 2016

A high percentage of double and multiple stars among those in T-associations was first paid attention to by Prof V.A. Ambartsumian. Further at the beginning of sixties many investigators of variable stars (Kukarkin, Herbig et al.) paid attention to the necessity of studying duplicity of stars in T-associations. Just then the first lists of wide pairs in T-associations appeared.We set a task to search for the Trapezium type multiple stars in T-associations involving the groupings of T Tau type variable stars from Kholopov’s list at a distance up to 500 pc. Such associations proved to amount 19, but out of them we succeeded in searching only in 12 ones.
Photographic observation of close binaries with large magnitude differences
Authors: Wedel Bernhard 
Published: July 2016

Problems:1.Size of diffraction image2.Ross effect (shrinking of high exposed star images in the photographic emulsion)3.Halo by diffusion of light in the photographic emulsion4. ScintillationMethods of improving the observation conditions are as following:1.Deformation of diffraction image with quadratic or other formed masks2.Diffraction gratings render possible a better measurement but don’t avoid Ross effect and halo of diffusion.The halo of diffusion can reach much more of diameter than the original image.
Study of Spectroscopic Binaries with the Objective Prism Method
Authors: Gieseking Frank 
Published: July 2016

The frequency distribution of SB’s over apparent visual magnitude emerging from the catalogue of Batten et. al. (1978) shows a very steep decrease of the number of spectroscopically detected SB’s already for such bright stars of magnitude 7. Considering the number of all stars in the individual magnitude intervals, we find a kind of completeness parameter of the spectroscopic surveys: If we scale it somewhat optimistically at 100% between 0 and 3 mag, we see a 50% decrease of the completeness of our knowledge of stellar radial velocities already for stars fainter than 4.5 mag.This situation is mainly due to the fact that the measurement of radial velocities with conventional slit spectrographs is extremely laborious, requiring long exposure times at large telescopes for the exposure of only one spectrum at a time. – Therefore more efficient methods for radial velocity determinations of fainter stars are urgently needed.
Binary Star Observations with the Multi-Aperture Amplitude Interferometer
Authors: Currie Douglas G. 
Published: July 2016

The basic goal of the Amplitude Interferometer Program at the University of Maryland has been to achieve very high angular resolution, far beyond the angular resolution which is normally permitted by the Earth’s atmosphere. This program is primarily directed to the observation of objects of astrophysical and astrometrical interest.The initial general science objective has been the measurement of the angular diameters of various single stars at various wavelengths. As shall be discussed later, this has been achieved on the current equipment.The second objective of the Amplitude Interferometer Program is the study of binary and multiple star systems. Some initial tests have been conducted to validate the approach and the expected accuracy using the existing Amplitude Interferometer (AI). However, detailed tests and/or a regular observing program require the multiplexing capablity of the next generation Amplitude Interferometer (the Multi-Aperture Amplitude Interferometer) in order to have a reasonable observing efficiency for the use of the telescopes which would be involved
The Solid State Area Scanner Photometer
Authors: Rakos Karl D. 
Published: July 2016

The accuracy of the area scanning technique depends on observing conditions resulting from seeing, tracking irregularities of the telescope, photon and seeing statistics (integration time and the size of the telescope), and the atmospheric spectral dispersion of the stellar image in the spectral region used. In addition, the reduction method as well as the mechanical and optical quality of the telescope and photometer influence the accuracy of the results.The tracking error of the telescope is usually larger than the observer believes. The amplitude of the periodic error of the worm gear is at best ± 0.5 arc sec with period length between 4 and 10 minutes, depending on the particular telescope. Figure 1 shows the tracking error for the ESO 50 cm and 100 cm telescopes. Other telescopes usually fit in between this two extremes.
Some Aspects of Visual Binary Star Orbit Determination
Authors: Harrington Robert S. 
Published: July 2016

The problem under consideration is that of determining the seven elements (the vector ) characterizing the relative three-dimensional motion of the components of a binary star, using observations of the two-dimensional projection on the sky of the relative positions of those components as a function of time. Sooner or later a differential correction process is employed; therefore, this correction procedure will be reviewed first.The basic approach is to derive a first estimate of the orbital parameters, form residuals from each of the observations, and assume these residuals represent a normally distributed random error, plus systematic errors due to an incorrect initial orbit. Expressing the residuals as functions of the orbital elements, these functions can be expanded in a Taylor series about the initial orbit and truncated after the first-order terms, giving the following approximate linear relation:
First results of Mercator observations of variable B stars
Authors: De Cat P. , De Ridder J. , Uytterhoeven K. , Davignon G. , Raskin G. , Cuypers J. , Schoenaers C. , Daszyńska-Daszkiewicz J. , Aerts C. , Van Winckel H. , Ausseloos M. , Broeders E. , De Meester W. , Vanautgaerden J. , Van Malderen R. , Vandenbussche B. , Acke B. , Decin G. , Decin L. , Kolenberg K. , Maas T. , De Ruyter S. , Reyniers M. , Reyniers T. , Van Kerckhoven C. , Waelkens C. 
Published: July 2016

AbstractWe report on the first results from observations of 28 variable B stars obtained with the new Mercator telescope (La Palma). Besides confirming the pulsational nature of known and candidate β Cephei and slowly pulsating B stars, we also present new candidate ellipsoidal variables and spotted stars.
On application of multi-colour photometry of δ Scuti stars
Authors: Daszyńska-Daszkiewicz J. , Dziembowski W.A. , Pamyatnykh A.A. 
Published: July 2016

AbstractIn δ Scuti star models the photometric amplitudes and phases exhibit a strong dependence on convection, which enters through the complex parameter,f, that describes the bolometric flux variation. We present a new method of extracting l and f from multi-colour data and apply it to several δ Scuti stars. The inferred values of f are sufficiently accurate to yield a useful constraint on models of stellar convection.
Eclipsing binaries in local group galaxies: Physical properties of the stars and calibration of the zero-point of the cosmic distance scale
Authors: Guinan Edward F. , Ribas Ignasi , Fitzpatrick Edward L. 
Published: July 2016

AbstractWe report on the progress of the program to study eclipsing binaries (EBs) in the Local Group galaxies. The primary goals of the program are to determine accurate distances and physical properties of the stars, and to probe the structure and evolution of the host galaxies. In particular, the distance to the Large Magellanic Cloud (LMC) is critically important because this nearby galaxy is used to calibrate most of the important cosmic distance indicators such as Cepheid and RR Lyr variables. Over the last several years, we have demonstrated that the distance of the LMC can be reliably measured using selected eclipsing binaries. The combined analyses of the UV/optical spectrophotometry, radial velocities, and light curves yield the stars’ physical properties (mass, radius, Teff, luminosity, metal abundance) and accurate (2–3%) distances. So far, the physical properties and distances of four LMC EBs have been completed and give a distance to the centroid of the LMC of 48.3 ± 1.6 kpc. Several additional EBs in the LMC and the Small Magellanic Cloud have been observed and are being analyzed. Also several LMC EBs have been observed with FUSE (92 – 119 nm) to further refine values of Teff and interstellar absorption. As an extension of these studies, 19–20th mag EBs in M31 are being observed photometrically and spectroscopically. The results of this extragalactic EB program are discussed along with plans to use EBs to study the host galaxy structure.
Non-Adiabatic Seismic Study of The Thin Convective Envelope of δ Scuti Stars
Authors: Dupret M.-A. , Grigahcène A. , Garrido R. , Montalban J. , Gabriel M. , Scuflaire R. 
Published: July 2016

AbstractFor δ Sct stars, the theoretical predictions of a non-adiabatic pulsation code are very dependent on the characteristics of the thin convective envelope of the models (Balona & Evers 1999). The treatment of the non-adiabatic interaction between convection and pulsation also has a significant impact on the results, particularly near the red edge of the instability strip. The non-adiabatic theoretical predictions can be tested upon observations by comparing them to the amplitude ratios and phase differences as observed in different color passbands (Dupret et al. 2003). In the first part of this paper, we compare the results obtained by adopting different treatments of convection in the interior and atmosphere models: mixing-length theory (MLT) and full spectrum of turbulence (FST) (Canuto et al. 1996, CGM). In the second part, we examine the problem of the interaction between convection and pulsation and compare the mode stability obtained with and without including time-dependent convection in our non-adiabatic code.