bluuebunny/crossref_metadata_2025 huggingface dataset:
The FeII λ5317 line profile of nine Be stars
Authors: Ballereau D. , Chauville J. , Zorec J.
Published: July 2016

Our aim is to analyze the FeII λ5317 emission line of nine Be stars recorded in 1990, to deduce some constraints on the modeling of their envelope and to compare them to the results obtained in 1985 and 1987 by other authors.
First results of an international multisite multitechnique campaign on o micron And
Authors: Sareyan J.P. , Chauville J. , Briot D. , Adelman S.J. , Alvarez M. , Balega I. , Balega Y. , Bardin D. , Belkin I. , Bonneau D. , Bossi M. , Desnoux V. , Espoto M. , Fried R. , Gonzalez-Bedolla S. , Guo X.Z. , Guo Y.L. , Hao J.X. , Huang L. , Klotz A. , Leister N. , Morand F. , Mourard D. , Vakili F. , Valera F. , Zhao F.Y.
Published: July 2016

Omicron Andromedae is a multiple system of at least four stars: a B ↔Be star (component A), a spectroscopic binary (components B1–B2) and a close companion (component a). According to several studies (see Hill et al. 1988, 1989):

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the distance between A and the B1–B2 system decreased from 0.39″ in 1975 to 0.25″ in 1987 (McAlister and Hartkopf 1988)

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the few previous speckle measurements of component a have shown the possibility of a 3.7 years orbit around A, according to the 1975 to 1984 observations (mean distance 0.05″). The calculations with this 3.7 yr orbit lead to the prediction of a maximum distance of 0.77″ at 1992.738, i.e. at the end of september 1992, with a North-South orientation.
Spectroscopic analyses of HdBe stars
Authors: Jeffery C.S.
Published: July 2016

A few hydrogen-deficient B stars (or extreme helium stars: EHes) exhibit Be-type behaviour (the HdBe stars). The principal class members are BD −9°4395, LSE 78 and DY Cen. The hot RCrB stars MV Sgr and V348 Sgr and the hot EHes HD 160641 and LSS 5121 are related to these objects. Since there are wide abundance variations amongst the EHes, as well as wide variations in Be-type behaviour, the principal HdBes have been analysed for atmospheric parameters, including Teff, log g and composition.
Stark widths of astrophysically important four- and five-times charged ion lines
Authors: Dimitrijević Milan S.
Published: July 2016

Important astrophysical applications of Stark broadening of spectral lines of multiply charged ions are in the physics of stellar interiors (Seaton 1987). In subphotospheric layers, the modelling of energy transport requires radiative opacities and thus, certain atomic processes must be known accurately. At these high temperatures (105 K or more) and densities (1017 − 1022 cm-3) Stark broadening of strong multicharged ionic lines plays a non-negligible role in the calculation of the opacities, especially in the UV. Moreover, with the development of spectroscopic investigations from space, UV and extreme UV spectral line research has been further stimulated.
The number of Be stars compared with the number of B stars, taking into account the specific physical characteristics of Be stars
Authors: Briot D. , Zorec J.
Published: July 2016

It is very important for the understanding of the Be phenomenon, and particularly for locating a possible Be phase in the evolutionary track of B stars, to accurately determine the proportion of Be stars among all B stars. This type of study was already made several times in the past. Results obtained generally show a maximum Be frequency around spectral type B2 then a decrease towards late spectral types. Actually Be stars do not have the same characteristics as “normal” B stars and we have to take this into account in the determination of the ratio : number of Be stars / number of B stars. We use the Bright Star Catalogue (Hoffleit & Jaschek 1982) and the Supplement to the Bright Star Catalogue (Hoffleit, Saladyga & Wlasuk 1983) containing stars V= 7.10 and brighter. This study needed to be made separately for the different spectral types because:

- Physical parameters of B stars are very different from B0 to B9;

- Emission characteristics of Be stars vary very much, with a decrease from B0e to B9e.

We successively consider three effects which can influence the frequency of Be stars:

- The over-luminosity of Be stars as compared with B stars;

- Spectral type changes during constant mass evolution;

- Spectral type changes due to the fast rotation of Be stars.
Dust and gas in shells around Herbig Ae/Be stars
Authors: Voshchinnikov N.V. , Il'in V.B. , Kholtygin A.F.
Published: July 2016

Herbig Ae/Be (HAEBE) stars are young objects with strong infrared excesses, variable brightness, intrinsic polarization and complex spectral line profiles. Almost all of these features are due to the presence of circumstellar (CS) shells. We consider the group of HAEBE stars with non-periodic Algol-like minima (UX Ori, WW Vul, etc.). They have irregular brightness drops by 2–3 mag in the visual, accompanied by an increase of linear polarization.
IR-radio spectral indices for Be stars
Authors: Chen H. , Taylor A. R. , Dougherty S.M. , Waters L.B.F.M.
Published: July 2016

Using published data and new data from mm observations, we calculate spectral indices α(12μ-25μ), α(25μ-1.1mm) and α(1.1mm-2cm) for Be stars. The index α(25μ-1.1mm), obtained for 8 stars, shows two characteristics: 1) for “normal” Be stars the index decreases from earlier types towards later types, i.e., later type Be stars tend to have shallower spectra in the IR-radio region than earlier types; 2) the index for shell stars appears to have smaller values than that for normal Be stars with same spectral types.
Continuum flux and polarization in B[e] supergiants
Authors: de Araújo F.X. , Stee Ph. , Lefèvre J.
Published: July 2016

B[e] supergiants constitute one group of stars in the upper left part of the HR diagram. On the basis of their hybrid spectrum and their intrinsic polarization a two components envelope was suggested (Zickgraf & Schulte-Ladbeck, 1989): a “polar wind” and a denser “equatorial disc”.
Transit Search for Exoplanets with the Vulcan Camera
Authors: Caldwell Douglas A. , Borucki W. J. , Jenkins J. M. , Koch D. G. , Webster L. , Showen R. L.
Published: July 2016

The NASA Ames Research Center's Vulcan photometer is being used in a search for close–in giant extrasolar planets. With our current data reduction system we achieve 0.2–0.8% hour–to–hour relative photometric precision on ∽ 6000 stars brighter than 13th magnitude. Three Galactic-plane fields have so far yielded hundreds of variable stars, including ∽ 50 eclipsing or interacting binaries per field. Several candidate detections have been followed up with radial velocity observations. High-resolution spectroscopy revealed many of the strongest candidates to be grazing eclipsing binaries.
Properties of the EXPORT sample: Spectral type determination
Authors: Merín Bruno , Montesinos Benjamín ,   EXPORT TEAM (A. Alberdi, A. Collier Cameron, J.K. Davies, H.J. Deeg, C. Eiroa, R. Ferlet, F. Garzon, C.A. Grady, A. Harris, K. Horne, L.F. Miranda, A. Mora, R. Oudmaijer, J. Palacios, A. Penny, A. Quirrenbach, H. Rauer, J. Schneider, E. Solano, Y. Tsapras, P.R. Wesselius, D. de Winter)
Published: July 2016

In this paper we present the results of the spectral classification of stars included in the EXPORT (EXoPlanetary Observational Research Team) sample and observed during the 1998–1999 International Time campaigns in the Canary Island observatories. Intermediate resolution spectra obtained with the Isaac Newton Telescope (INT) were used in this work. In addition to the confirmation of some spectral types and changes to previous classifications, we report new results for stars whose spectral type had not been accurately assigned before.
Search for Signatures of an Atmosphere of HD209458 b
Authors: Rauer H. , Cameron A. Collier , Barnes J. , Harris A. W.
Published: July 2016

We investigate the prospects of detecting the presence of Na D absorption features during transits of the planet of HD209458 by means of high-resolution spectroscopy.
Bisector analysis as a diagnostic of intrinsic radial-velocity variations
Authors: Santos N. C. , Mayor M. , Naef D. , Queloz D. , Udry S.
Published: July 2016

In this contribution we present the results of the application of the bisector of the cross-correlation function as a diagnostic of activity-related radial-velocity variations. The results show that the technique is very effective. We present examples for which the application of the bisector analysis was essential to establish the planetary nature of the candidate or to exclude an orbital signature. An analysis of the behaviour of the bisector for active dwarfs of different spectral types shows that the relation between the bisector and the radial-velocity variation depends in a great extent on thevsiniof the star. The results may shed a new light on the intrinsic sources of radial-velocity variation for different types of solar-type dwarfs.
Physical parameters for the EXPORT sample. Rotational velocities and effective temperatures
Authors: Solano E. , Montesinos B. , Mora A. ,   EXPORT Team (A. Alberdi, A. Collier Cameron, J.K. Davies, H.J. Deeg, C. Eiroa, R. Ferlet, F. Garzon, C.A. Grady, A. Harris, K. Horne, B. Merfn, L.F. Miranda, R. Oudmaijer, J. Palacios, A. Penny, A. Quirrenbach, H. Rauer, J. Schneider, Y. Tsapras, P.R. Wesselius, D. de Winter
Published: July 2016

The methods used to calculate projected rotational velocities and effective temperatures for the targets observed during the 1998-1999 La Palma International Time campaign are described here. This is part of a project whose main goal is to perform a detailed chemical analysis of these objects and to study their potential implications in the planetary formation phenomenon.
Modes of Gaseous Planet Formation
Authors: Boss Alan P.
Published: July 2016

The discovery of gas giant planets around nearby stars has launched a new era in our understanding of the formation and evolution of planetary systems. However, none of the over four dozen companions detected to date strongly resembles Jupiter or Saturn: their inferred masses range from sub-Saturn-mass to 10 Jupiter-masses or more, while their orbits extend from periods of a few days to a few years. Given this situation, it seems prudent to re-examine mechanisms for gas giant planet formation. The two extreme cases are top-down or bottom-up. The latter is the core accretion mechanism, long favored for our Solar System, where a roughly 10 Earth-mass solid core forms by collisional accumulation of planetesimals, followed by hydrodynamic accretion of a gaseous envelope. The former is the long-discarded disk instability mechanism, where the protoplanetary disk forms self-gravitating, gaseous protoplanets through a gravitational instability of the gas, accompanied by settling and coagulation of dust grains to form solid cores. Both of these mechanisms have a number of advantages and disadvantages, making a purely theoretical choice between them difficult at present. Observations should be able to decide the dominant mechanism by dating the epoch of gas giant planet formation: core accretion requires more than a million years to form a Jupiter-mass planet, whereas disk instability is much more rapid.
The Distribution of Asteroidal Dust in the Inner Solar System
Authors: Grogan Keith , Dermott S.F. , Kehoe T.J.J.
Published: July 2016

In this paper we demonstrate how the action of secular resonances near the inner edge of the asteroid belt strongly effects the inclinations and eccentricities of asteroidal dust particles, such that they lose the orbital characteristics of their parent body and are dispersed into the zodiacal background. As a consequence, it may not be possible to relate the distribution of interplanetary material at 1 AU to given asteroidal or cometary sources with the level of confidence previously imagined.
Disc Modes and Orbital Eccentricity Growth
Authors: Papaloizou John C.B.
Published: July 2016

An eccentric protoplanetary gaseous disc provides a slowly precessing non axisymmetric mass distribution. As a result of self-gravity, the precession frequency may resonate with that of a near circular protoplanet orbit within an inner cavity. A large eccentricity might then be produced.
A Comparative Anatomy of Dusty Disks Imaged by NICMOS
Authors: Schneider Glenn , Hines Dean C. , Silverstone Murray , Weinberger Alycia J. ,   the NICMOS/IDT EONS Team
Published: July 2016

Using the Near Infrared Camera and Multi-Object Spectrometer (NICMOS) on the Hubble Space Telescope we have conducted a coronagraphic imaging survey of 18 main sequence stars with large infrared excesses, searching for circumstellar dust (debris) in scattered light. Dusty disks with radial and hemispheric brightness anisotropies and complex morphologies, both possibly indicative of dynamical interactions with unseen planetary mass companions, were spatially resolved and imaged around three young (≲ 10Myr old) stars. From these observations we describe the debris systems around: a) HR 4796A (A0V), a 70 AU radius ring less than 14 AU wide with unequal ansal flux densities; b) HD 141569A (Herbig Ae/Be), a 400 AU radius disk with a 40 AU wide gap; and c) TW Hya (K7 T-Tauri), a pole-on circularly symmetric disk with a radial break in its surface density of scattering particles. Additionally, our non-detection of scattered light and high precision photometry of a fourth system of similar age, HD 98800 A/B, coupled with mid and thermal IR measurements, greatly constrain a likely model for the debris about the B component.
Density Distribution in Disks around Protostellar Objects
Authors: Bastien Pierre , Hajjar Roger
Published: July 2016

A new method to find the density distribution in disks around protostellar objects, based on linear polarization maps, is presented. This method uses the displacement of the polarization null points as a function of wavelength. Variations in optical depth are converted into density variations with opacity tables for dust grains. The method has been applied with five linear polarization maps obtained at different wavelengths of the classical T Tauri star HL Tau. The slope of the density as a function of radius in the disk is compatible with the model of the standard protosolar nebula. The total mass of the disk is compatible with values determined by other methods. Other objects have been analyzed, with similar results, although with a smaller number of wavelength bands.
Indicator of Exo-Solar Planet(s) in the Circumstellar Disk Around β Pictoris
Authors: Gorkavyi Nick , Heap Sara , Ozernoy Leonid , Taidakova Tanya , Mather John
Published: July 2016

Our efficient numerical approach has been applied to modeling the asymmetric circumstellar dust disk around β Pictoris as observed with the HST/STIS. We present a new model on the origin of the warping of the β Pic disk. We suggest that the observed warp is formed by the gravitational influence of a planet with a mass of about 10 masses of Earth, at a distance of 70 AU, and a small inclination (∽ 2.5°) of the planetary orbit to the main dust disk. Results of our modeling are compared with the STIS observations.
Evidences of protoplanetary disks in a selected sample of weak T Tauri stars
Authors: Gregorio-Hetem Jane , Hetem Annibal
Published: July 2016

A model with two dust components is used do explain the circumstellar structure of weak-T Tauri stars. The IR-excess was calculated and compared to spectroscopic criteria in order to classify the objects according an evolutionary sequence. About 46% of the sample correspond to young main sequence stars showing dust distribution consistent with a disrupted disk, that could be possibly caused by the formation of a planetary system.
STIS Coronagraphic Observations of β Pictoris
Authors: Heap S. R. , Lindler D. J. , Lanz T. M.
Published: July 2016

We present recent coronagraphic observations of β Pictoris obtained with the Space Telescope Imaging Spectrograph (STIS) aboard the Hubble Space Telescope. The superb, high-resolution images show that the inner part of the disk is inclined by about 5° with respect to the main disk. Long-slit coronagraphic spectrograms oriented along the inner disk indicate that the reflectance of the inner disk is neutral over the spectral region, 3000-5600 Å.
The dust composition of discs surrounding isolated Herbig Ae/Be stars
Authors: Meeus G. , Bouwman J. , Waters L.B.F.M. , Waelkens C. , van den Ancker M.E.
Published: July 2016

We present Infrared Space Observatory (ISO) spectra of 14 isolated Herbig Ae/Be stars. The IR spectra were combined with photometric data from the UV to the sub-mm region. We defined two key groups, based upon the spectral shape of the IR region. The results can be summarized as follows (see also Meeus et al. 2001): (1) the continuum of the IR to sub-mm region can be reconstructed by the sum of a power-law and a cool component, which can be represented by a black body. Possible locations for these components are an optically thick, geometrically thin disc (power-law component) and an optically thin flared region (black body); (2) remarkably, some sources lack the silicate bands; (3) PAH bands are present in at least 50% of our sample; with one exception, PAHs are not present in sources which only show a power-law continuum in the IR; (4) the dust in HAEBE stars shows strong evidence for coagulation; this dust processing is unrelated to any of the central star properties.
Masers as probes of proto-planetary discs
Authors: Richards A.M.S. , Cohen R. J. , Crocker M. , Lekht E. E. , Samodourov V. , Berulis I. I. , Lobanov A. , Moscadelli L.
Published: July 2016

Water maser emission from star forming regions has been monitored for several decades using the Puschino radio telescope, showing radial velocity variations consistent with material in Keplerian orbit around protostars. MERLIN and the EVN are now being used to image the 22 GHz emission on au scales and measure proper motions. This will distinguish discs from outflows, and provide an estimate of the central mass and possibly orbiting condensations.
Dust Rings in the Circumstellar Gas Disks
Authors: Takeuchi Taku , Artymowicz Pawel
Published: July 2016

In optically thin gas disks around young Vega-type stars, dust grains are exposed to the stellar radiation pressure and gas drag force. The combination of these forces pushes the grains away from the central star. Typically, 10–100 μm grains migrate outward to become concentrated at the outer edge of the gas disk. A dust ring naturally forms without the help of clearing bodies, such as planets or brown dwarfs.
Protoplanetary disks around Herbig Ae/Be stars: Indications from ISO spectroscopy
Authors: van den Ancker M.E.
Published: July 2016

An analysis of solid-state features in infrared spectra of 46 Herbig Ae/Be stars is presented. The presence of solid-state emission bands is compared to other indicators of circumstellar material, such as Hα emission, optical variability and sub-mm continuum fluxes. The correlation between these different indicators is weak, if present at all, in our sample. However, a strong dependence on spectral type of the central star seems to be present: stars with spectral type earlier than B9 show either amorphous silicate in absorption or infrared spectra dominated by PAH emission, whereas more than 70% of the stars of later spectral type show silicate emission. We conclude that the infrared spectrum of Herbig Be stars is in general dominated by emission from the circumstellar envelope, whereas the lower-mass Herbig Ae stars show a spectrum that is dominated by a disk that is passively heated by the central star.
Planetary System Imaging and Spectroscopy from Earth and Space
Authors: Woolf N. J. , Angel J.R.P. , Lunine J. I.
Published: July 2016

We describe the two main techniques by which planetary systems may be imaged, and by which spectra of the planets may be obtained. There is a discussion of how planetary systems will appear, and of the extreme differences in brightness between stars and their planets Coronography is an extension of Lyot's technique by addition of adaptive optics. Nulling is an interferometric technique originally proposed by Bracewell. Differences between the techniques are emphasized. The paper concludes with a discussion of the problem of training people to develop these technically difficult tasks.
An Adaptive Optics Survey for Companions to Stars with Extra-Solar Planets
Authors: Lloyd James P. , Liu Michael C. , Graham James R. , Enoch Melissa , Kalas Paul , Marcy Geoffrey W. , Fischer Debra , Patience Jennifer , Macintosh Bruce , Gavel Donald T. , Olivier Scot S. , Max Claire E. , White Russel , Ghez Andrea M. , McLean Ian S.
Published: July 2016

We have undertaken an adaptive optics imaging survey of extra-solar planetary systems and stars showing interesting radial velocity trends from high precision radial velocity searches. Adaptive Optics increases the resolution and dynamic range of an image, substantially improving the detectability of faint close companions. This survey is sensitive to objects less luminous than the bottom of the main sequence at separations as close as 1″. We have detected stellar companions to the planet bearing stars HD 114762 and Tau Boo. We have also detected a companion to the non-planet bearing star 16 Cyg A.
The Nuclei of Nearby Radio-Loud Ellipticals
Authors: Verdoes Kleijn G.A. , de Zeeuw P.T. , Baum S.A. , O'Dea C.P. , van der Marel R.P. , Xu C. , Carollo C.M. , Noel-Storr J.
Published: July 2016

We have observed a complete sample of 21 nearby (D < 70h−1Mpc) Fanaroff & Riley Type I galaxies with HST/WFPC2 and detected dust disks and lanes in 19 of them. The radio jets are roughly perpendicular to the dust which is used to constrain the Doppler boosting factors of the radio jet and cores. The VLBA core flux correlates with the central Hα+[NII] flux which might indicate that the VLBA core is dominated by an isotropic component. Twelve galaxies show nuclear optical sources. We discuss various possible origins for this emission.
Analysis of Double-Peaked Profile Lines in 3C390.3
Authors: Nazarova L.S. , Bochkarev N.G.
Published: July 2016

The analysis of the line ratios along the profiles show that CIV/Lα line ratio is low in the center of lines but high in the wings although the Lα/Hβ line ratio has changed the opposite way. The line ratios have been modeled using the photoionization code CLOUDY. On the bases of the photoionization modeling along the line profiles we discuss the possible geometry of the emitted gas.
VLBI and Broad-Band Radio Spectra Study of the Strongly Variable Extragalactic Object 0524+034
Authors: Kovalev Y.Y. , Gorshkov A.G. , Konnikova V.K. , Mingaliev M.G.
Published: July 2016

Results of the first measurements of a VLBI structure of 0524+034 at 6 cm at the EVN+HartRAO in 1999 and recent broad-band spectra monitoring data are reported. We suppose that precession of the relativistic jet can be one of the possible mechanisms to account for the observed milliarcsecond structure and the strong long-term variations of the spectrum. The detected rapid changes may be interpreted as a propagation of a shock in the inhomogeneous jet plasma, but interstellar scintillations can not be ruled out on the basis of available data.
The VSOP project: Space VLBI Imaging of AGN at 1.6 and 5 GHz
Authors: Murata Y. , Hirabayashi H. , Edwards P.G.
Published: July 2016

The VLBI Space Observatory Programme (VSOP) combines an orbiting radiotelescope with arrays of ground radio telescopes to extend the Very Long Baseline Interferometry (VLBI) technique to baselines up to almost three Earth diameters. In this paper, we present results from VSOP observations of active galactic nuclei (AGN) at 1.6 and 5 GHz from the first 3.5 years of the mission.
Space VLBI Observations of PKS 1921-293
Authors: Shen Zhi-Qiang , Edwards Philip G. , Kameno Seiji , Inoue Makoto , E. J. Lovell James
Published: July 2016

We present results of the first space VLBI observations of PKS 1921-293. An inner jet component about 1.5 mas north of the core is revealed for the first time. The compact core is partially resolved, but still has a brightness temperature (at the source rest frame) of 3.0×1012 K. A spectral index map made by combining the 1.6 GHz VSOP image with the 5.0 GHz VLBA+Y image at the first epoch is also presented.
The γ-ray Loud Quasar PKS 1510-089
Authors: Venturi T. , Dallacasa D. , Mantovani F. , Torri S.
Published: July 2016

We performed a multifrequency and multiepoch study of the quasar PKS 1510-089 with ground and space VLBI, in order to study its nuclear properties and test current models for the production of the emission at X- and γ-ray energies. A preliminary analysis of our images suggests that the lower limit to the Lorentz factor γ at the distance of ∼ 12 pc from the central engine is γmin = 5. We used Ho = 100 km s−1 Mpc−1.
A Sub-pc-scale Acceleration of the Radio Jet of NGC 6251
Authors: Sudou Hiroshi , Taniguchi Yoshiaki , Kaburaki Osamu , Ohyama Youichi , Kameno Seiji , Sawada-Satoh Satoko , Inoue Makoto , Sasao Tetsuo
Published: July 2016

In order to investigate the genesis of powerful radio jet, we have mapped the central 10 pc region of the nearby radio galaxy NGC 6251 with a 0.2 pc resolution using VLBI at two radio frequencies, 5 GHz and 15 GHz, we have found the sub-parsec-scale counterjet for the first time in this radio galaxy. This discovery allows us to investigate the jet acceleration based on the relativistic beaming model.
The VLBI core in Radio Loud AGNs
Authors: Jiang D.R. , Cao Xinwu , Zhou J.F.
Published: July 2016

We present statistical results on VLBI cores from large VLBI samples at C, L and S/X bands. Most of the results are consistent with the inhomogeneous jet model. The magnetic field distribution and particle density in the inhomogeneous jet model were estimated. We also found that the flux densities and luminosities of the cores at 5 GHz were correlated with those at optical band in the rest-frame.
Optical Imaging of the Central Kiloparsecs of a Sample of Low Luminosity AGN
Authors: Marchã M.J. , Antón S.
Published: July 2016

Selected with the primary objective of studying the differences between BL Lacs and their closest relatives, a sample of 55 optically bright, low luminosity core dominated radio sources has been studied. The spectroscopy carried out for this sample, however, yielded not only BL Lacs but also a completely unexpected number of sources with strong emission lines (much like those found in Sy galaxies), and almost 50% of galaxies with weak (EW ≤ 30Å), or absent emission lines. Such optical diversity is at odds with the traditional unification schemes for low luminosity AGN and it has prompted an optical imaging campaign. High resolution optical images obtained at NOT are discussed, in particular the central colours and profiles of the different types of sources found in the sample.
Evidence for a Circumnuclear Torus in Edge-On Radio Galaxies
Authors: Peck A.B. , Taylor G.B.
Published: July 2016

We have used VLBI HI absorption imaging to search for evidence for a circumnuclear atomic structure in five radio galaxies. Of these, we have found that two, (PKS 2322-123 and 1946+708), are very symmetric on parsec scales and exhibit strong evidence for a circumnuclear torus, confirming the prediction of the unified scheme. The two nearby extended radio galaxies NGC 5128 and NGC 315, on the other hand, have asymmetric core-jet morphologies on parsec scales, and their HI absorption profiles appear to arise from gas in the host galaxy which is not associated with the AGN at all. This is also consistent with the unified scheme of AGN. One remaining source, NGC 3894, also has symmetric jets, but has a very complicated HI structure which changes on parsec scales. This source requires further study.
HI and OH Absorption of the Nuclear Region of NGC 3079
Authors: Sawada-Satoh S. , Inoue M. , Shibata K.M. , Kameno S. , Nakai N. , Migenes V. , Diamond P.J.
Published: July 2016

We conducted an observation of weak HI and OH absorption features in the parsec-scale nuclear region of NGC 3079 using a global VLBI network; the VLBA, the VLA and the Green Bank 43-m telescope of NRAO. One mas corresponds to 0.076 pc in NGC 3079.
Circumnuclear Disks in Early-type Galaxies as Evidence for Secondary Formation Events
Authors: Sil'chenko Olga K.
Published: July 2016

The phenomenon of chemically distinct galactic nuclei is quite new and hardly studied yet. During the last 10 years we search for chemically distinct nuclei in disk galaxies, and after our first work (Silchenko, Afanasiev, & Vlasyuk 1992) two dozens of those are already found. A question posed now is if the galaxies with chemically distinct nuclei have also distinct circumnuclear disks and if these disks can be identified with chemically distinct areas. An answer for the first part of the question is certainly ‘YES’; the second part is far less clear. The observations presented here are made during 1996-1998, mostly with the Multi-Pupil Field Spectrograph (MPFS) of the 6m telescope (Afanasiev et al. 1990). The MPFS allows to obtain a set of 96 to 240 spectra from an extended area; each spectrum corresponds to an element of 1.3 × 1.3 before mid-1998 and 1.0 ' 1.0 later. Seeings were 1.5 − 2.5. What do we mean when telling about chemically distinct nuclei? We recognize them by a sharp drop of metal absorption-line equivalent widths when passing from the point-like nuclei to the surrounding bulges. Figure 1 presents 4 examples of the radial profiles of the magnesium and iron absorption-line indices in the Lick system (Worthey et al. 1994). The data for M 31 are long-slit data from the 1m telescope of the Special Astrophysical Observatory; the cross-sections are taken in 5 various position angles (for details, Silchenko, Burenkov, & Vlasyuk 1998). The other data are azimuthally averaged measurements from the MPFS (for details, see Silchenko 1999a,b and Afanasiev & Silchenko 2000). All the profiles decrease prominently within the radius comparable to the spatial resolution; in the bulges they flatten off. The metallicity drops between the nuclei and the bulges by a factor of 2 to 10. The behaviours of the magnesium and iron indices can be similar or different. The most interesting feature is revealed by comparing the iron and magnesium profiles in NGC 1023 and NGC 7331: the magnesium peaks in the very center whereas the maxima of the iron index are at the R ≈ 1. We should treat this phenomenon as an evidence for a short-duration star formation burst in the center and a more prolongated one in its neighborhood.
VSOP observations of the X-ray binary LSI + 61°303
Authors: Taylor A.R. , Dougherty S.M. , Scott W.K. , Peracaula M. , Paredes J.M.
Published: July 2016

We have made multi-epoch observations of the unusual X-ray binary star LSI + 61°303 using the HALCA spacecraft in combination with a large array of ground radio telescopes. We present initial analysis of six observing epochs during a radio outburst. The images reveal an apparently stationary pattern of symmetric emission extending about 2 mas on either side of a central source. The central source is observed to expand at a rate of 0.25 mas/day. At the distance to LSI + 61°303, this corresponds to ∼ 860 km/s.
Classification of Ionized Photoevaporation Flows
Authors: Henney W.J.
Published: July 2016

From proplyds to champagne flows, spanning 4 orders of magnitude in size and density, photoevaporation flows are ubiquitous in H II regions. Such flows are also found in planetary nebulae, in the form of cometary knots, although in this case the flows are often “advection-dominated”, unlike the “recombination-dominated” flows that predominate in H II regions.
WB89 520: A Small Isolated High Mass Star Forming Region Associated with an Extremely Metal-poor Nebula
Authors: Wang Jun-Jie , Hu Jing-Yao , Wei Jian-Yan , Testi Leonardo
Published: July 2016

In this paper, by discussing and analyzing the observational results of near infrared imaging, optical spectroscopy and 12CO molecular line, together with IRAS and NVSS data, we conclude that WB89 520 is an UC HII region with a very young compact stellar cluster. The spectrum of the UC HII region shows that it is an extremely metal-poor nebula, which has the lowest line ratio of [NII]/Hα (∼ 1/56) discovered in the nebulae of our Galaxy until now. We give two possible explanations for the low metallicity.
Multiline Study with VLBI of SiO Masers in Evolved Stars
Authors: Colomer Francisco
Published: July 2016

We present preliminary results of our observations of the 7 mm (v=1 and v=2 J=1-0) and 3 mm (v=1 J=2-1) SiO masers in the circumstellar envelopes of evolved stars. The 7mm masers were observed with the Very Large Baseline Array (VLBA) and the European VLBI Network (EVN), and the 3mm ones with the Coordinated Millimeter VLBI Array (CMVA). We find similarities between the maps, despite the non-coincidence in the location of most spots in the different 7 mm lines. The visibilities found for most compact spots are compatible with maser sources as small as 0.13 mas (or 0.023 AU at the distance of R Cas).
Megamaser Dics-Rings in Active Galactic Nuclei
Authors: Zhi-yao Yu
Published: July 2016

We present results from fitting of water-vapor megamaser emission from NGC 4258 and NGC 1068. Using the radiative transfer, velocity, and coordinate equations, we derive parameters of the maser disc-rings.
Astrometry of Supernovae in Recent Years
Authors: Yamaoka Hitoshi
Published: July 2016

The positions (the coordinates and the offset from the nucleus of the host) of extragalactic supernovae (SNe) are very important for further research into their nature. The positions reported in the literature are, however, sometimes erroneous. Here we give the precise coordinates of three SNe based on the recently-developed star catalogs. The standard deviations of the positions are expected to be sub-arcsecond, which can be better than the offsets from the ambiguous nuclei of the host galaxies.
Space VLBI
Authors: Hirabayashi H.
Published: July 2016

Space VLBI enables high angular resolution and high dynamic range imaging through an extension of ground-based VLBI. The TDRSS space VLBI experiments in the 1980s were followed by the first space VLBI imaging mission, VSOP, in the 1990s. The new century holds the promise of the VSOP-2 and ARISE missions, which aim for more sensitive, higher angular resolution and higher observing frequency capabilities. These missions will enable AGNs to be viewed much more clearly and will make broader science areas, including lower brightness sources, accessible. It is noted that in all space VLBI missions, international collaboration in global sense plays an important role.
High Quality Imaging for Space VLBI Observations with Ultra High Angular Resolution
Authors: Likhachev Sergey
Published: July 2016

This presentation focuses on the problems associated with obtaining high quality images from a high orbiting space VLBI (SVLBI) mission. SVLBI intensifies and magnifies all imaging problems, making these problems clearer to understand, though much harder to solve.
Diffraction Limited Imaging of High Redshift Galaxies with Adaptive Optics
Authors: Davies R.I. , Lehnert M. , Baker A.J. , Rabien S.
Published: July 2016

The major cornerstone of future ground-based astronomy is imaging and spectroscopy at the diffraction limit using adaptive optics. To exploit the potential of current AO systems, we have begun a survey around bright stars to study intermediate redshift galaxies at high resolution. Using ALFA to reach the diffraction limit of the 3.5-m telescope at Calar Alto allows us to study the structure of distant galaxies in the near-infrared at scales of 100-150 pc for z=0.05 and at scales 1.0-1.5 kpc at z=1. In this contribution we present the initial results of this project, which hint at the exciting prospects possible with the resolution and sensitivity available using an AO camera on the 8-m class VLT.
Prospects for High Angular Resolution in Gamma-ray Astronomy
Authors: Skinner G.K.
Published: July 2016

It is in the gamma-ray band, the shortest wavelength part of the electromagnetic spectrum, where diffraction limitations are least constraining, that one might hope for the highest angular resolution. The intrinsic limitations of the imaging techniques used in gamma-ray astronomy are reviewed and the feasibility of obtaining diffraction-limited angular resolution in this band discussed. It is argued that by accepting the necessity of extremely long focal lengths, sub micro arc second resolution along with enormously improved sensitivity should be achievable using diffractive lenses.
Binary Stars: Historical Milestones
Authors: Zinnecker Hans
Published: July 2016

This is a brief historical review of the discovery of binary stars, starting in the 18th and 19th century with the work of W. Herschel, W. Struve, and their famous sons. I describe how Ch. Doppler in 1842 found the Doppler effect in connection with the colours of double stars. I also describe how the observation of the stationary Calcium H and K lines in the spectrum of the spectroscopic binary δ Ori led to the discovery of the interstellar medium by J. Hartmann in 1904 with the Potsdam refractor. Some steps in the discovery of young binary stars are recounted, starting with the paper of Joy and van Biesbroeck in 1944. The history of ideas regarding the origin of binary systems is also briefly reviewed, beginning with J. Michell's statistical argument in 1767 that many close visual pairs of stars must indeed form physical systems, and W. Herschel's definition of a binary star as “a real double star - the union of two stars that are formed together in one system, by the laws of attraction”.
Herbig Ae/Be Visual Binaries
Authors: Bouvier Jérôme , Corporon Patrice
Published: July 2016

We present the results of a high-angular resolution spectro-imaging survey of a sample of isolated Herbig Ae-Be (HAeBe) stars aimed at searching for close companions. The fraction of wide binaries is found to be significantly higher in HAeBe stars than in solar-mass field dwarfs, and suggests a companion star fraction possibly larger than 1. The spectral energy distribution of the primaries and secondaries is derived independently from multi-wavelength resolved photometry of the systems. It is found that young low-mass companions usually do not exhibit infrared excesses, which suggests that the lifetime of their circumstellar disk might have been shortened by the influence of the massive primary.
The Properties of Open Cluster Binaries Based on High-Resolution Imaging Surveys
Authors: Patience Jenny , Duchêne Gaspard
Published: July 2016

With known properties such as age, distance and stellar density, young clusters provide ideal samples for binary star studies. We summarize recent results from high-resolution multiplicity surveys of IC 348, α Per, the Pleiades, the Hyades, and Praesepe. The statistics of the resolved companions are used to address binary star formation and evolution in clusters. Over the ranges of ages, densities and stellar masses covered by the clusters, it is found that the binary fraction is correlated with stellar density rather than age, and that both the binary fraction and binary mass ratio distribution depend upon mass. The impact of companions on X-ray emission and stellar rotation is also discussed.
Doppler Imaging as a Test for Binary Star Formation Theories
Authors: Strassmeier Klaus G.
Published: July 2016

Photospheric Doppler images for both stellar components of the double-lined spectroscopic binary V824 Ara reveal surface temperature inhomogeneities of up to 1800 K on both stars. The absolute brightness and the mass of the two stars suggest that they are very close to the main sequence – but not yet on the ZAMS – if an inclination of the orbital plane (and rotational axes) of 52° is adopted as suggested by the Doppler imaging. Since both stars are active, we solve for the inclinations of the rotation axes of both stellar components separately and emphasize that it can be used to test coplanarity predictions from binary star-formation theories. We find that the spin inclinations for the individual components of V824 Ara agree to within their uncertainties.
Can Disks Produce Companions by Gravitational Fragmentation?
Authors: Durisen Richard H.
Published: July 2016

The nonlinear outcome of gravitational instabilities in disks depends critically on the thermal physics of the gas. Under conditions where thermal energy is lost efficiently, disks disrupt into dense arms, arclets, and clumps. However, the evidence about whether clumps can ever become permanent bound objects is currently inconclusive. Under conditions where cooling is less efficient or where a balance between heating and cooling is achieved, the amplitudes reached by gravitational instabilities are relatively modest. The result is disk heating and transport of mass and angular momentum rather than condensation of bound companions. Future numerical simulations need to resolve the disk vertical structure and include more realistic equations of state and energy transport.
Tidally–Induced Angular Momentum Transport in Disks
Authors: Terquem Caroline E. J. M. L. J.
Published: July 2016

We discuss the transport of angular momentum induced by tidal effects in a disk surrounding a star in a pre–main sequence binary system. We consider the effect of both density and bending waves. Although tidal effects are important for truncating protostellar disks and for determining their size, it is unlikely that tidally–induced angular momentum transport plays a dominant role in the evolution of protostellar disks. Where the disk is magnetized, transport of angular momentum is probably governed by MHD turbulence. In a non self–gravitating laminar disk, the amount of transport provided by tidal waves is probably too small to account for the lifetime of protostellar disks. In addition, tidal effects tend to be localized in the disk outer regions.
A Brief Introduction to DQ Tau
Authors: Stassun Keivan G.
Published: July 2016

We review the salient observational properties of DQ Tau, with an emphasis on the photometric and spectroscopic time-variability of the system. We summarize the evidence for this variability being linked to the orbital dynamics of the underlying close, eccentric, binary.
Accretion and the Properties of Protobinary Systems
Authors: Bate Matthew R.
Published: July 2016

We discuss the evolution of the properties of a protobinary system which forms via fragmentation within a collapsing molecular cloud core and grows to its final mass by accreting from the gaseous envelope. We predict how the mass ratio distributions and the masses of the circumstellar and circumbinary discs depend on the binary's separation, the primary's mass, and the properties of the pre-collapse molecular cloud core. We also discuss how the properties of binaries may depend on whether they were formed in isolated molecular cloud cores or in stellar clusters.
Frontiers of Radiative Transfer
Authors: Henning Thomas
Published: July 2016

Detailed radiative transfer calculations are an essential tool for the analysis of observations related to fragmented molecular cloud cores, protobinaries, and circumbinary and circumstellar disks. In this contribution, recent progress in line and continuum radiative transfer models will be reviewed.
The Structure of Symposium 204
Authors: Harwit Martin
Published: July 2016

The extragalactic infrared background touches on many topics: The rate at which energy was generated in stars at different epochs; the corresponding number counts of galaxies observed at different redshifts; the related rate at which non-primordial helium and the heavy chemical elements were produced at these same epochs; the abundances of these elements that can be found in damped Lyman-alpha absorbers at commensurate redshifts; the abundances of the same elements in Galactic stars formed at similar epochs; the integrated supernova rates over all epochs, and the number of neutron stars and black holes in our locale within the Universe today. The distances from which TeV gamma-rays at different energies can reach us are also intimately related to the infrared background spectrum. The purpose of this Symposium was to seek a coherent picture into which all these pieces of observational evidence can be satisfactorily fitted. This was the rationale in setting up the invited talks.
2MASS Star Counts and Galactic Structure
Authors: Ojha D. K.
Published: July 2016

This paper presents a global analysis of the first 2MASS (Two Micron All Sky Survey) data as observed in seven fields at different Galactic latitudes. These new data lead to strong constraints on the radial structure of the Galactic thin and thick disks. The interpretation of star counts and color distributions of stars in the near-infrared with a synthetic stellar population model provides strong evidence that the Galactic thin disk density scale length, hR, is rather short (2.8±0.3 kpc). The Galactic thick disk population is revisited in the light of new data. We find the thick disk to have a local density of 3.5 ± 2.0% of the thin disk, exponential scale height, hz, of 860±200 pc and exponential scale length, hR, of
Far-Infrared Source Counts and the Diffuse Infrared Background
Authors: Puget J. L. , Lagache G.
Published: July 2016

The cosmic far-infrared background is now well measured from 140 μm to 1 mm. Uncertainties remain at 100 μm (and even more at 60 μm). These are dominated by limitations of the zodiacal model. The nature of sources dominating the background near its maximum are beginning to be studied through deep surveys carried out with ISOPHOT. These surveys show very steep number counts and fluctuations of the background due to unresolved sources.
Evidence for Galaxy Formation at High Redshift
Authors: Shanks Tom , Metcalfe Nigel , Fong Dick , McCracken Henry , Campos Ana , Thompson David
Published: July 2016

Metcalfe et al. (1995, 1996) have shown that galaxy counts from the UV to the near-IR are well-fitted by simple evolutionary models where the space density of galaxies remains constant with look-back time while the star-formation rate rises exponentially. We now extend these results, first by using data from the Herschel Deep Field to show that these same models give detailed fits to the faint galaxy r - i : b - r colour-colour diagram. We then use these models to predict the number counts of high redshift galaxies detected by the Lyman break technique. At z ≈ 3 there is almost exact agreement between our prediction and the data, suggesting that the space density of galaxies at z ≈ 3 may be close to its local value. At z ≈ 4 the space density of bright galaxies remains unchanged; however, the space density of dwarf galaxies is significantly lower than it is locally, suggesting that we have detected an epoch of dwarf galaxy formation at z ≈ 4. Finally, significant numbers of Lyman-break galaxy candidates are also detected at z ≈ 6 in the Hubble and Herschel Deep Fields; taking this observation together with a number of recent detections of spectroscopically confirmed z ≈ 6 galaxies suggests that the space density of bright galaxies at z ≈ 6 remains comparable to the local space density, and thus that the epoch of formation of bright galaxies may lie at yet higher redshift.
Evidence for a Morphological Evolution of Spiral Galaxies
Authors: Dutil Yvan , Roy Jean-René
Published: July 2016

A detailed analysis of the oxygen abundance profile has been carried out on a sample of spiral galaxies from which very good data was available. The early-type galaxies of our sample display gradients that are flatter, and overall levels of O/H abundances that are higher, than those of normal late-type galaxies. Early-type galaxies show an identical trend in the behavior of extrapolated central abundance versus morphological type to that shown by late-type galaxies with strong bars, even in the absence of a bar. On a diagram showing extrapolated central abundances versus morphological types, two clearly separated sequences appear: late-type barred galaxies and early-type (barred or unbarred) galaxies clearly fall on a sequence 0.5 dex in abundance below that of normal late-type galaxies. This behavior is consistent with theoretical models of morphological evolution of disk galaxies by the formation and dissolution of a bar over a period of a few 109 yr, where later type galaxies (Sd, Sc, SBc) evolve into earlier-type disk galaxies (Sb, Sa) through transitory SBc and SBb phases.