bluuebunny/crossref_metadata_2025_split huggingface dataset:
Pre-Main Sequence Binaries: The ESO Imaging Survey
Authors: Zinnecker H. , Brandner W. , Reipurth B. 
Published: July 2016

AbstractWe have observed a complete sample of southern Hα emission line pre-main sequence (PMS) stars associated with the nearby dark clouds Chamaeleon and Ophiuchus in an effort to detect binary companions. We have used the high resolution CCD camera SUSI (0.13″ /pixel) at the ESO 3.5m New Technology Telescope (NTT). The observations were carried out in the Gunn z filter (0.95μ). As a result, we have discovered 28 companions out of 160 objects surveyed in the range of angular separation 0″.5 – 10″. We present histograms of semi-major axes and of brightness ratios of these PMS binaries. Taking small incompleteness corrections into account, the frequency of PMS binaries with semi-major axes in the range 100-1500 AU is 20%, while it is only 15% in same range for solar-type Main Sequence (MS) stars. Extrapolation yields a total PMS binary frequency of 70%. Evolutionary and environmental implications are briefly discussed.
Duplicity Among Young Stars in Chamaeleon
Authors: Chen Wen Ping , Graham J.A. 
Published: July 2016

AbstractWe present infrared imaging results of young stars in Cha I and II clouds that show either extended structure or a nearby neighboring star. Both regions appear to show high incidence rates of pairs. After excluding possible background stars, as judged from their brightness, color, or the local stellar surface number density, a frequency of 10% is deduced for binaries in Cha I with separations 2-5″, which is comparable to that in Taurus and to that of main sequence field stars.
Dusty Disks in the Multiple Systems UZ Tau and GG Tau
Authors: Simon M. , Guilloteau S. 
Published: July 2016

AbstractInterferometric observations of the 2.6 mm dust thermal emission around the T Tauri triple system UZ Tau show that most of it is equally divided between UZ Tau W (the close binary) and UZ Tau E. The emission is at least partially optically thick at 2.6 mm which implies an origin in disks of size ~ 13 AU and mass ~ 0.024 M⊙. The 2.6 mm emission of the GG Tau system, a hierarchical quadruple, is partially resolved. Strong emission extended over ~ 3″ × 5″ is associated with the close binary GG Tau. Weak emission is detected at GG Tau/c, also a close binary. Evidently extensive dusty disks can survive in the environment of close binaries for at least ~ 105 y, and their structure can vary markedly from system to system.
Spectroscopic Studies of Multiple Stars and Speckle Binaries: How to observe ad infinitum
Authors: Fekel Francis C. 
Published: July 2016

AbstractOver the past 16 years at the McDonald Observatory and the Kitt Peak National Observatory, I have obtained high-dispersion spectroscopic observations of roughly 3 dozen multiple systems and 7 speckle or astrometric binaries. The current status of this obviously long-term project is discussed. Although some systems have periods of about 50 to 85 years, most have periods in the range of 1 to 20 years. Thus, many now have been observed for at least one cycle and preliminary spectroscopic orbital elements have been determined. For a number of the systems fundamental data such as the distance to the system, as well as the individual spectral types, absolute magnitudes, and masses can be obtained if accurate visual/speckle orbital elements also are known. These elements and the derived fundamental parameters may be used as constraints on multiple-star formation theory.
Adaptation of Docobo’s Method for the Calculation of Orbits of Spectroscopic-Interferometric Binaries with Mixed Data
Authors: Docobo J.A. , Ling J.F. , Prieto C. 
Published: July 2016

AbstractBased on Docobo’s method for the calculation of orbits of visual binaries, an algorithm is presented for the calculation of short-period orbits when observational data comprise radial velocities and polar coordinates. The method is applied to some examples.
Detectability of Stellar Companions by Imaging
Authors: Heacox William D. , Gathright John 
Published: July 2016

AbstractThe 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

AbstractIf 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

AbstractThe 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

AbstractWe 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

AbstractWe 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

AbstractThe 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

AbstractCepheid 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.
Sub-Milliarcsecond Binary Star Astrometry
Authors: Pan Xiaopei , Shao Michael , Mark Colavita M. 
Published: July 2016

AbstractLong–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

AbstractWe 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.
Speckle Data in the New Bright Star Catalogue
Authors: Warren Wayne H. , Hoffleit Dorrit 
Published: July 2016

AbstractThe 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

AbstractThree 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

AbstractRoutine 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

AbstractCopenhagen 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

AbstractLausanne 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.
Tycho Photometry: Calibration and First Results
Authors: Großmann V. 
Published: July 2016

AbstractThe 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

AbstractThe 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.
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)
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.
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

AbstractThe 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.