bluuebunny/crossref_metadata_2025 huggingface dataset:
Mechanisms of Heating and Heat Transfer in the Outer Solar Atmosphere
Authors: Kuperus M. , Chiuderi C.
Published: July 2016

The amount of heat required to maintain the chromosphere and corona can be found from an estimate of the losses. The two processes that transport energy from the corona into interstellar space are electromagnetic radiation and the solar wind. In the Inner corona thermal conduction constitutes the dominant means of energy loss, but convection by the solar wind gradually takes over in the outer corona.
The distance scale within the Local Group
Authors: Van Den Bergh Sidney
Published: July 2016

Toutes les techniques couramment utilisées pour déterminer les distances des galaxies proches sont passées en revue. Les résultats de cette étude sont résumés dans la table V. On remarque que l’augmentation de la distance des Hyades, suggérée récemment, a peu ou même n’a aucun effet sur l’échelle des distances extragalactiques. Ceci provient du fait que cette augmentation de la distance des Hyades est pratiquement compensée par une diminution de l’échelle des distances résultant de la prise en compte d’une abondance en métaux supérieure à la moyenne dans les étoiles des Hyades.
Is there evidence of anisotropy in the expansion of the universe?
Authors: Rubin Vera C.
Published: July 2016

Un échantillon idéal pour la recherche d’une éventuelle anisotropie dans l’expansion de Hubble doit couvrir la totalité de la surface du ciel, de plus les magnitudes et les vitesses ne doivent pas être entachées d’erreurs dépendant de la position des objets choisis. Très peu d’échantillons satisfont ces critères. Toutefois les échantillons de galaxies Se I, de galaxies E et SO, et d’amas riches mettent en évidence une anisotropie provenant soit d’une vitesse du groupe local ~ 500kms-1, (V⊙ ~ 600kms-1), soit du fait que H varie de 20% d’un point à l’autre du ciel, soit du fait que m ou Mo varie de 0.4m. Des explications moins conventionnelles ne semblent pas nécessaires. Seul le mouvement du groupe local est compatible avec les données de l’échantillon de SC I les plus proches. Compte-tenu du mouvement de l’observateur, l’expansion de Hubble ne présente pas d’anisotropie supérieure à 5%. Toutefois, cette interprétation n’est pas compatible avec le rayonnement à 3°K qui impose V⊙ <300kms-1.
Some remarks concerning the velocity and spatial distributions of galaxies
Authors: Fall S. Michael , Jones Bernard J. T.
Published: July 2016

Nous discutons quelques aspects des rapports entre la distribution spatiale et la distribution des vitesses des galaxies en insistant surtout sur la recherche d’anisotropie. Nous incluons à la fois les relations dynamiques et les effets de selection qui pourraient être importants dans de telles études.
The influence of the night sky on velocity determinations from optical absorption lines
Authors: Simkin S.M.
Published: July 2016

L’analyse numérique de spectres d’absorption de galaxies montre que des erreurs systématiques jusqu’à 500-600km/s peuvent apparaitre dans les mesures de vitesses radiales entre 5200 et 9200 km/s. Ces erreurs sont produites par la superposition du spectre du ciel nocturne aux longueurs d’onde de 4020, 4046, et 4078 Å. La “structure de bandes” trouvée par Tifft dans le diagramme mv, VR de l’amas de galaxies dans Coma peut provenir de ce type d’erreur systématique.
Hubble diagram of quasars
Authors: Petrosian Vahe , Soldate Mark A.
Published: July 2016

Nous montrons que le diagramme de Hubble (densité de flux -décalage spectral) des quasars ne peut-être utilisé pour tester l’hypothèse que leur décalage vers le rouge est cosmologique, Toutefois, nous montrons que cette relation peut-être utilisée pour tester l’hypothèse locale dans laquelle le décalage cosmologique des quasars est supposé être petit et la majeure partie du décalage être due à quelque cause non cosmologique. Une telle hypothèse générale et locale peut-être rejetée avec une certitude supérieure à 95%. Nous montrons que ce pourcentage peut augmenter jusqu’à 99% en faisant des suppositions moins générales mais très plausibles.
The Hubble diagram for red magnitudes of bright cluster galaxies
Authors: Kristian J. , Sandage A. R. , Westphal J. A.
Published: July 2016

Nous présentons le diagramme de Hubble des amas brillants de galaxies.
The Hercules cluster of galaxies
Authors: Tarenghi M.
Published: July 2016

De nouvelles observations de décalage spectral et de la morphologie d’un échantillon de galaxies plus brillantes que mpg =15.8 sont pratiquement achevées dans un cercle de 2.5° de rayon autour du centre du complexe de galaxies d’Hercule. Les résultats préliminaires suggèrent l’existence d’un superamas d’Hercule.
The Ho value from luminosity classes and 21 - cm line observations of galaxies
Authors: Bottinelli L. , Gouguenheim L.
Published: July 2016

Nous montrons que la calibration des classes de luminosité les plus brillantes adoptée par Sandage et Tammann dans leur papier IV est trop élevée; nous établissons une nouvelle calibration de la classe I et nous obtenons ainsi une valeur de la constante de Hubble H0 égale à 76 au lieu de la valeur 55 donnée par Sandage et Tammann. Ce résultat est confirmé par une méthode indépendante à partir de nouvelles observations de galaxies en raie 21 cm de l’hydrogène neutre effectuées avec le radiotélescope de Nançay. En appliquant le critère de distance de Tully et Fisher, fondé sur la largeur du profil de la raie 21 cm, nous obtenons une valeur moyenne Ho = 77, pour notre échantillon de galaxies extérieures au Superamas Local. En conclusion, nous sommes conduits à adopter la valeur Ho = 75 qui est en désaccord avec la valeur Ho=55 de Sandage et Tammann, bien que fondée sur une même calibration locale.
The redshift dependence of galaxy surface brightness
Authors: Crane Philippe , Hoffman Alan W.
Published: July 2016

Nous avons déterminé la brillance superficielle moyenne d’amas à l’intérieur d’un diamètre linéaire projeté de 20. 3 kpc en faisant la photométrie de galaxies dans six amas ayant un redshift de z=0. 05 à 0. 20. Pour toutes les cosmologies dans lesquelles le décalage vers le rouge est uniquement dû à l’expansion, la brillance superficielle devrait avoir la forme m (SB)=2. 5 a log (l+z) + b où a≡4 et b est une constante d’échelle. Nous trouvons a=4. 1 ± 1. 6 et b= 22. 12 ± 0. 21. Ces résultats supportent fortement l’interprétation des décalages vers le rouge comme dus à l’expansion de l’univers.
White holes of types II and III
Authors: Lake K. , Roeder R.C.
Published: July 2016

Nous donnons une discussion qualitative des trous blancs dans le contexte d’un espace de Schwarzschild au sein d’un univers de Robertson-Walker (ce sont les solutions fondamentales de trous trouvées par Schücking et al.). Nous montrons que les configurations d’expansion (trous blancs) peuvent être classées en types I, II ou III suivant la région de l’espace de Schwarzschild dans lesquelles elles s’étendent à partir de la région IV. Nous discutons plusieurs propriétés des différents types, et montrons que si le trou est de type II ou III, la radiation reçue par un observateur peut avoir un décalage vers le rouge intrinsèque non lié au décalage cosmologique.
Low Surface Brightness Galaxies in Deep Surveys
Authors: Ferguson Henry C.
Published: July 2016

We examine the constraints that can be placed on the space density of low-surface-brightness galaxies from deep HST images. Such images, while covering only a small solid angle, provide enough depth and spatial resolution to detect LSB galaxies at moderate redshift and distinguish them from galaxies of higher surface brightness.

We consider five simple models of the non-evolving or slowly-evolving population of LSB galaxies, motivated by various discussions in the recent literature. The basic results are (1) models with a large space-density of giant LSB galaxies at moderate redshift do not look like the real world and, (2) models with a large space-density of dwarf LSB galaxies are consistent with HST data (that is, they do not produce more faint LSB galaxies per unit solid angle than are detected at magnitudes I ≳ 23), but these LSB dwarf galaxies do not contribute much to faint galaxy counts unless they formed their stars in a rapid burst.
Morphology and Stellar Populations in the Gas-Rich, Giant LSBGs
Authors: Knezek P.
Published: July 2016

An unexpected characteristic of low surface brightness galaxies (LSBGs) is that a significant number are massive and possess substantial amounts of atomic gas. We present preliminary results of an ongoing program to obtain BVRIJHK imaging, along with some nuclear spectroscopy, of a well-defined sample of LSBGs which are gas-rich and of similar size to giant, high surface brightness spiral galaxies (HSBGs). These LSBGs span the entire range of Hubble disk morphologies. While their disks are bluer, on average, than comparable HSBGs, the optical morphology of massive LSBGs indicates that many of these systems have undergone previous star formation episodes. They typically have long disk scale lengths, and range from MB = −16 to −22 (H0 = 75 km s−1 Mpc−1). About half of the LSBGs with bulges show evidence of nuclear activity, and ~30% appear to be barred. These massive, gas-rich LSBGs apparently have varied, and often complex, evolutionary histories.
Kinematics of Giant Low Surface Brightness Galaxies
Authors: Pickering T.E.
Published: July 2016

High sensitivity H I observations now exist for six giant low surface brightness (LSB) disk galaxies including the two prototypes, Malin 1 (Bothun et al. 1987; Impey & Bothun 1989) and F568-6 (also known as Malin 2; Bothun et al. 1990). Their H I surface brightnesses are generally low, but proportionally not as low as their optical surface brightnesses. Their total H I masses and radial extents are quite large, however, with MHI ∼ 1010M⊙h−275 and with detectable H I out to 100 kpc h−175 or more in a couple of cases. The rotation curves of these systems rise slowly and are consistent with negligible disk contribution, similar to many previously observed dwarf galaxies. However, the peak rotation velocities of these galaxies are high (>200 km s−1) and infer high dynamical masses. These galaxies provide the some of the first examples of galaxies that are both massive and dark matter dominated.
The fate of LSB galaxies in clusters and the origin of the diffuse intra-cluster light
Authors: Moore Ben , Lake George , Stadel Joachim , Quinn Thomas
Published: July 2016

We follow the evolution of disk galaxies within a cluster that forms hierarchically in a standard cold dark matter N-body simulation. At a redshift z = 0.5 we select several dark matter halos that have quiet merger histories and are about to enter the newly forming cluster environment. The halos are replaced with equilibrium high resolution model spirals that are constructed to represent luminous examples of low surface brightness (LSB) and high surface brightness (HSB) galaxies. Whilst the models have the same total luminosity, ~ L*, they have very different internal mass profiles, core radii and disk scale lengths, however they all lie at the same place on the Tully-Fisher relation. Due to their “soft” central potentials, LSB galaxies evolve dramatically under the influence of rapid encounters with substructure and strong tidal shocks from the global cluster potential - galaxy harassment. As much as 90% of the LSB disk stars are tidally stripped and congregate in large diffuse tails that trace the orbital path of the galaxy and form the diffuse intra-cluster light. The bound stellar remnants closely resemble the dwarf spheroidals (dE’s) that populate nearby clusters, with large scale lengths and low central surface brightness.
The Connection Between dE and dI Galaxies
Authors: Miller Bryan W.
Published: July 2016

We combine specific globular cluster frequencies (SN) with newly measured surface brightness profiles to identify dEs that may be stripped dIs. Luminous dEs generally have higher surface brightnesses and steep central light profiles. Conversely, fainter dEs have low surface brightnesses and flatter central light profiles. The most likely candidates for stripped dIs have low SN and low central surface brightnesses.
Star Formation Thresholds in Low Surface Brightness Dwarf Galaxies
Authors: van Zee Liese
Published: July 2016

The results of a comparative study of star formation thresholds in gas-rich, low surface brightness, dwarf galaxies are presented. Approximately half the galaxies in the study were “high MH/LB” galaxies, which appear to have inefficient star formation properties. The comparison sample comprised of otherwise “normal” dwarf galaxies, with moderate current star formation rates. In all systems, sites of active star formation were associated with local peaks in the HI column density. For both types of galaxies, the azimuthally averaged gas column density is low. Similar to other LSB systems, the global gas densities are well below the critical threshold for star formation throughout the system. Thus, star formation is inhibited globally, but occurs locally in these gas-rich dwarf galaxies.
Testing environmental influences on star formation with a sample of Low Surface Brightness dwarf galaxies in the Vigo cluster
Authors: Heller Ana , Almoznino Elchanan , Brosch Noah
Published: July 2016

We analyze the star formation activity of an homogeneous LSB dwarf galaxy sample in the Virgo cluster, as a function of the radial velocity relative to the cluster mean velocity and the projected distance from the center of the cluster, using CCD images obtained at the Wise Observatory. The localized Hα emission in the HII regions of this sample is compared to that of an isolated gas-rich sample of LSB dwarf galaxies and that of a representative sample of Blue Compact Dwarf (BCD) galaxies in the cluster. We report preliminary results on the LSB dwarf star formation histories obtained from surface color distribution.
The Parkes Multibeam Blind HI Survey
Authors: Webster R.L. , Kilborn V. , O’Brien J.C. , Staveley-Smith L. , Putman M.E. , Banks G.
Published: July 2016

A thirteen-beam HI receiver has been constructed for the Parkes radio telescope. When this instrument is used in active scanning mode, it can rapidly survey large areas of sky, with a relatively uniform sensitivity. The Multibeam Working Group, comprising about 30 astronomers from more than a dozen institutions, is undertaking a blind HI survey of the entire southern sky. The status of the survey is described, with some of the first scientific results.
Simulations of Lyα Absorption from Low Surface Brightness Galaxies
Authors: Linder Suzanne M.
Published: July 2016

Using simulations of the low redshift galaxy population based upon galaxy observations, it is shown (Linder 1998) that the majority of Lyα absorbers at low redshift could arise in low surface brightness (LSB) galaxies. The contribution to absorption from LSB galaxies is large for any galaxy surface brightness distribution which is currently supported by observations. Lyα absorbers should become powerful tools for studying the properties and evolution of galaxies, but first it will be necessary to establish observationally the nature of the Lyα absorbers at low redshift. Further simulations, in which the absorbing galaxy population is ‘observed’ with some selection criteria, are used to explore how easy it is for an observer to test for a scenario in which LSB galaxies give rise to most of the Lyα absorbers. It is shown that absorption arising in LSB galaxies is often likely to be attributed to high surface brightness galaxies at larger impact parameters from the quasar line of sight.
First Results from the HI Parkes Zone of Avoidance Survey
Authors: Henning P.A. , Staveley-Smith L. , Kraan-Korteweg R.C. , Sadler E.M.
Published: July 2016

The HI Parkes Zone of Avoidance Survey is a 21 cm blind search with the multibeam receiver on the 64-m radiotelescope, looking for galaxies hidden behind the southern Milky Way. The first phase of the survey has uncovered 107 galaxies, two-thirds of which were previously unknown. The addition of these galaxies to existing extragalactic catalogs allows the connectivity of large-scale structures across the Zone of Avoidance within 3500 km s−1 to become evident. No nearby hidden “Andromeda-class” object was uncovered. Our census of the most dynamically important HI-bearing nearby galaxies is now complete, at least for those objects whose HI profiles are not totally buried in the Galactic HI signal. The full survey is ongoing, and is expected to produce a catalog of thousands of objects when it is finished.
Diffuse Ultraviolet Background Radiation
Authors: Henry Richard C.
Published: July 2016

Diffuse ultraviolet background radiation may contain important information concerning the dark matter of the universe. I briefly review new Voyager observations of the diffuse background, which give a very low upper limit on the background radiation shortward of Lyman α, and I review the capabilities for detection and characterization of diffuse radiation that will be provided by a proposed new NASA mission. Low-surface-brightness radiation remains largely an unexplored frontier, particularly in the ultraviolet.
Southern triplets of galaxies
Authors: Karachentseva V. E. , Karachentsev I. D.
Published: July 2016

Using the ESO/SERC and POSS-I sky surveys we selected 76 isolated triple systems of galaxies with Dec. < −3°. For each triplet the equatorial coordinates, type of configuration, angular diameters, apparent angular separation of the components, morphological types, total magnitudes and some other characteristics are presented. 33 of 76 triplets have the measured radial velocities for all the components. The median values of basic dynamic parameters: a radial velocity dispersion, mean harmonic separation, an absolute magnitude of galaxies, mass-toluminosity ratio are very close to those obtained earlier for 83 northern isolated triple systems from the list of Karachentseva et al. (1979).
Observed isolated galaxy triplets in the Las Campanas redshift survey
Authors: Bērziņš Kārlis
Published: July 2016

Some problems and statistical approaches in studies of galaxy groups are discussed.
The Luminosity Function of Galaxies in Compact Groups
Authors: Hunsberger S. D. , Charlton J. C. , Zaritsky D.
Published: July 2016

From R-band images of 39 Hickson compact groups (HCGs), we use galaxy counts to determine a luminosity function. We find that a single Schechter function is a poor fit to the data, so we use a composite function consisting of separate Schechter functions for the bright and faint galaxies. The decreasing bright end slope implies a deficit of intermediate luminosity galaxies in our sample and the faint end is slightly steeper than that reported for earlier HCG luminosity functions. Furthermore, luminosity functions of subsets of our sample reveal more substantial dwarf populations for groups with X-ray halos, groups with tidal dwarf candidates, and groups with a dominant elliptical or lenticular galaxy. Collectively, these results support the hypothesis that within compact groups, the initial dwarf galaxy population is replenished by “subsequent generations” formed in the tidal debris of giant galaxy interactions.
Objectively selected samples of galaxy multiplets: an analysis of observed properties
Authors: Kelm B. , Focardi P. , Palumbo G. G. C.
Published: July 2016

A method of searching for multiplets in a large catalogue of galaxies with measured redshifts is described. Compact Groups samples having different local and global characteristics are generated when the algorithm is applied to ZCAT catalogue. Both local and environmental galaxy density have been computed thus allowing to define truly isolated compact groups as well as compact groups in dense and medium dense environments. We find 40% of our compact groups to be isolated while as much as 20% are identified in high density structures.
The Nature of Hickson Compact Group 18
Authors: Plana Henri , de Oliveira Claudia Mendes , Amram Philippe , Balkowski Chantal
Published: July 2016

We present new observations of Hα emission of the Hickson Compact Group 18 (HCG 18) obtained with a scanning Fabry-Perot interferometer. The velocity field does not show motions of individual group members but instead a complex common velocity field of H18b, c and d. The gas distribution is very clumpy with blobs coinciding with group members but located also elsewhere. Comparing Hα with H ɪ data we reached the conclusion that HCG 18 seems to be an irregular galaxy containing several clumps of star formation sites.
Morphological Characteristics of Compact High-Velocity Clouds Revealed by High-Resolution WSRT Imaging
Authors: Burton W. B. , Braun R.
Published: July 2016

A class of compact, isolated high–velocity clouds which plausibly represents a homogeneous subsample of the HVC phenomenon in a single physical state was objectively identified by Braun and Burton (1999). Six examples of the CHVCs, unresolved in single–dish data, have been imaged with the Westerbork Synthesis Radio Telescope. The high–resolution imaging reveals the morphology of these objects, including a core/halo distribution of fluxes, signatures of rotation indicating dark matter, and narrow linewidths constraining the kinetic temperature of several opaque cores. In these regards, as well as in their kinematic and spatial deployment on the sky, the CHVC objects are evidently a dynamically cold ensemble of dark–matter–dominated H ɪ clouds accreting onto the Local Group in a continuing process of galactic evolution.
Galaxies and the intergalactic medium in groups
Authors: Ponman Trevor J. , Lloyd-Davies Ed , Helsdon Stephen F.
Published: July 2016

The study of the relationship between the hot gas in groups and the galaxies they contain can help to constrain the evolution of both galaxies and groups. Here we present evidence that the intergalactic medium in groups has been strongly affected by preheating associated with galaxy formation which mostly preceded group collapse. The presence of this effect appears to be unrelated to the morphology of group galaxies, which supports models in which galaxy types are not primordial. We also present preliminary evidence that early-type galaxies in groups are not underluminous in the X-ray compared to isolated galaxies, suggesting that their dark halos may not have been substantially stripped.
Peculiar X-ray features in bright early-type galaxies
Authors: Trinchieri Ginevra
Published: July 2016

IC 1262 and NGC 6159 have been selected for high resolution observations because their X-ray luminosity observed in the ROSAT All Sky Survey (Voges 1992) was higher than that observed from other normal, early type galaxies. The HRI observations confirm both the identification of the X-ray sources with the two galaxies (see Fig. 1; point sources in the field, clearly associated with optical counterparts, further ensure that the absolute pointing is correct), and the very high luminosities. Moreover, they indicate very extended emission, out to ≥ 7′ and ≥ 4′ radius (≥ 400 and ≥ 220 kpc at the galaxies’ distances), respectively, with a relatively regular morphology (although not azimuthally symmetric at large radii), and a smoothly decreasing surface brightness profile. At the center of IC 1262, however, several peculiar features are present (see Fig. 3 and later discussion).
Age Estimates for Galaxies in Groups
Authors: Forbes Duncan A. , Terlevich Alejandro I.
Published: July 2016

We discuss recent developments on the age and metallicity distribution for early type galaxies in different environments.
Las Campanas Compact Groups: Star formation properties
Authors: Allam Sahar S.
Published: July 2016

Using the equivalent width (EW) of [O II]λ3727, I analyse the star formation properties of Las Campanas Redshift Survey galaxies in different environments. The star formation activity in compact groups is found to be depressed relative to that in loose groups and the field.
Ab Initio Formation of Galaxies, Groups and Large-Scale Structure
Authors: Diaferio Antonaldo
Published: July 2016

For the first time, the combination of semi-analytic modelling of galaxy formation and N-body simulations of cosmic structure formation enables us to model, at the same time, both the photometric and the clustering properties of galaxies. Two Cold Dark Matter Universes provide a reasonable fit to the observed properties of galaxies, groups and clusters, including luminosities, colours, density and velocity biases. We show how the properties of galaxies and groups on small scales are inextricably connected with the global properties of the Universe.
The Connection with B[e] stars
Authors: Zickgraf Franz-Josef
Published: July 2016

The characteristics of the various types of B[e] stars are discussed and compared with those of classical Be stars. Both groups of stars are characterized by the presence of emission lines in their spectra, in particular of hydrogen. However, there are also significant differences between these classes. Classical Be stars lack hot circumstellar dust and strong forbidden low-excitation emission lines, which are typical characteristics produced by B[e]-type stars. While classical Be stars are a rather uniform group of early-type stars, B[e]-type stars form a quite heterogeneous group, very often of poorly known evolutionary status, comprising such diverse types of objects as near main-sequence objects, evolved lowmass proto-planetray nebulae and massive evolved hot supergiants. Even pre-main sequence Herbig Ae/Be stars sometimes find their way into the group of B[e] stars. However, despite these dissimilarities classical Be stars and B[e]-type stars, share a common property, namely the nonsphericity of their circumstellar envelopes.
A Spectropolarimetric Atlas of 61 Bright Northern Be Stars
Authors: Bjorkman Karen S. , Meade Marilyn R. , Babler Brian L.
Published: July 2016

We are developing an atlas of spectropolarimetric observations of 61 bright northern Be stars obtained from 1989-94 using the halfwave polarimeter (HPOL) at the 0.9m telescope of the University of Wisconsin Pine Bluff Observatory (PBO). The data cover the wavelength range from about 3400-7600Å, with a spectral resolution of about 25Å. This atlas will contain all data (297 observations total) obtained as part of a survey program with HPOL during the time when the detector in use was a dual Reticon array; the survey observations with HPOL continue, using a new CCD detector which extends the spectral coverage out to 1.05μm and improves the spectral resolution to about 12Å. The CCD observations will be presented later in a second volume of the atlas.

Only a brief summary of the findings of the survey from the first 5 years of the project is presented here. A full analysis of the data will be included in a paper to be published elsewhere. The general wavelength dependence of polarization for classical Be stars can be considered on the basis of these observations, and results on polarimetric variability are available. In particular, we find that 56% (20 of 36) of the Be stars observed 3 or more times from 1989-94 show significantly variable polarization at the level of 0.1% changes (inclusion of preliminary results from the continuing CCD survey indicates that the percentage is even higher). The timescales for these changes range from as short as night-to-night to as long as several months. Several of the stars showed evidence for polarimetric “outbursts” during the time period covered by the observations.
The Connection between Classical Be Stars and Herbig Ae/Be Stars
Authors: Böhm T. , Balona L.A.
Published: July 2016

We use a phenomenological approach to derive new constraints on the mass loss mechanisms working in the classical Be and the Herbig Ae/Be stars, which represent two groups of stars located very nearby in the HR diagram. We discuss observational similarities of classical Be and Herbig Be stars on one side, and stress, on the other side, the major differences between Herbig Ae and Herbig Be stars. For further details and a detailed bibliography, see Balona & Böhm (2000). A more quantitative approach will be needed and is deferred to future work.
Direct Optical Imaging of Be Disks
Authors: Stee Philippe
Published: July 2016

Interferometry in the visible now provides milliarcsecond spatial resolution and thus can be used for studying the circumstellar environment of Be stars. In this review I will first introduce the two basic quantities that an interferometer can access: the modulus and the phase of the visibility. I will illustrate how these two quantities can be used to understand the physics of Be disks through recent results from the VLA, the MkII and the GI2T interferometers. I will insist on the importance and the potential of coupling high angular resolution with high spectral resolution to the study of Be disks. Since the possibility of direct optical imaging of Be disks will be limited due to complexity and time consumption, I will present the role models can play in interpreting high angular resolution observations when direct imaging become difficult. Finally I will draw up a list of challenging objectives for the next generation of synthetic arrays (GI2T/REGAIN, Keck, ST3, VLTI) which will bring new understanding of active hot stars physics.
Pulsations in 66 Oph: Multiperiodicity in He I 6678
Authors: Floquet M. , Neiner C. , Briot D. , Chauville J. , Hubert A.M. , Ballereau D.
Published: July 2016

66 Oph has shown recurrent short-lived outbursts nicely detected from ground-based and space (Hipparcos) photometry.

Spectroscopic observations of He I 6678 and Hα lines were performed in June 1997 and June 1998. Search for short-term periodicities was done in He I 6678 line profiles as in equivalent width EW, radial velocity of the line centroid, and V and R components. At least two frequencies were present: ν = 4.0 c/d and ν = 2.2 c/d. The phase distribution of these frequencies over the line profile corresponds in the nrp frame to g-modes with ℓ ~ 3 − 4 and ℓ = 2 respectively.
The Rise of a Magnetic Flux Tube through the Radiative Envelope of a 9 M⊙ Star
Authors: Cassinelli J. P. , MacGrego K. B.
Published: July 2016

We explore the possibility that the magnetic field generated by a dynamo at the interface between the convective core and radiative envelope of a massive star can be transported to the surface by buoyancy.
The Formation and Structure of Circumstellar Disks
Authors: Bjorkman J.E.
Published: July 2016

Several theories have been proposed to explain the origin of Be star disks. Among them are Wind-Compressed Disks, accretion disks, decretion disks, and “explosive” ejections. In reviewing these mechanisms, I first concentrate on the current status of the Wind-Compressed Disk model. In particular, I discuss how non-radial forces may prevent disk formation and then discuss various physical effects that may restore the disk. Second, I examine the observational evidence and what it tells us about the structure of the disk. Of particular interest is evidence in favor of Keplerian disks. Finally, I discuss theories for Keplerian disk formation and some of the constraints such theories must satisfy.
Physical Properties of Circumstellar Envelopes in Be Stars Derived from their Long-term Spectrophotometric Variations
Authors: Moujtahid A. , Zorec J. , Hubert A.M.
Published: July 2016

The long-term visible spectrophotometric variations depicted by the following parameters: V the apparent visual magnitude; Φrb the gradient of the observed Paschen energy distribution and D the total Balmer discontinuity (BD) of 49 Be stars in different spectrophotometric phases (SPh-E: spectrophotometric phase where the second component of the BD is in emission; SPh-A: spectrophotometric phase where the second component of the BD is in absorption) were translated into CE physical parameters. These parameters are: R/R* the mean extent of the CE zone that produces the visible energy distribution; Tenv its mean temperature; τ the continuum opacity at λ0.56μm. The results obtained show that the triplet of parameters (V, Φrb, D) do not depend on the (R/R*, Tenv, τ) set of parameters in the same way if Be stars are in a SPh-E or in a SPh-A phase. Independently of the spectrophotometric phase, Tenv always decreases as a linear function of (R/R*)−1. In SPh-E it is (R/R*,)−1 ≤ 0.7, and in SPh-A it is (R/R*)−1 ≥ 0.7. All SPh behaviours can be summarized by the relation ∂Tenv/∂(R*/R) = ∂Tenv/∂τ × ∂τ/∂(R*/R) ≥ 0, which describes different spectrophotometric behaviours in both SPh-E and SPh-A phases.
Line Formation in Be Star Disks: Shell Absorption and Rotation Law
Authors: Hummel W. , Vrancken M.
Published: July 2016

We constrain the rotation law in Be star circumstellar disks. We show that Keplerian rotation is a valid approximation.
Variability of the Hα Emission in the Be Star o Andromedae
Authors: Panko E. , Tarasov A.
Published: July 2016

The parameters of the Hα line profile of the Be star o And were determined from observations carried out during the period 1985 - 1998. At this time the line has undergone significant changes – from a pure absorption photospheric profile with no sign of an envelope in 1985 to the transition into the shell phase with a very narrow and deep absorption component in 1989. During 1991 - 1998 the Hα emission remained at the level achieved in 1989. The line profile showed short-term changes. The envelope development in the time interval 1985 - 1998 does not confirm the previously found period of 8.5 years.
Stellar and Circumstellar Activity in the Be Star EW Lac from the Multi-site 1993 Campaign
Authors: Hubert A.M. , Floquet M. , Hirata R. , McDavid D. , Zorec J. , Gies D. , Hahula M. , Janot-Pacheco E. , Kambe E. , Leister N.V. , Stefl S. , Tarasov A.
Published: July 2016

The Be shell star EW Lac was observed in September 1993 during a multi-site campaign. Results from visual spectroscopy and polarimetry are summarized here. He I 6678 profiles have been compared to previous observations held in 1989 and show an additional complex and highly variable circumstellar component which can due to material expelled from the star just prior to these observations. Two groups of frequencies are found again in 1993 observations compared with 1989 ones. In the frame of nrp, they could be associated to low degree g-modes.
Photometry and Spectroscopy of X Per During the Years 1996-1999
Authors: Piccioni A. , Bartolini C. , Bernabei S. , Galleti S. , Guarnieri A. , Valentini G.
Published: July 2016

UBVRI photoelectric monitoring of the Be star X Per, a transient X-ray binary, during the last four years, along with some optical spectra are presented and briefly discussed in the context of the long term behaviour of the system.
Ionization Structure and Mass Loss for Rapidly-Rotating Near Main-Sequence B Stars
Authors: Bjorkman J.E. , Abbott B.P.
Published: July 2016

Using the wind-compressed disk model to determine the density and velocity of a rapidly rotating wind, we calculate the 2-D ionization structure and corresponding line profiles. We find that previous estimates of the mass-loss rate based on spherically symmetric models may be a factor of 5–10 too small.
New Radiation Driven Wind Solutions Including Stellar Rotation: Applicability to Be stars
Authors: Curé Michel
Published: July 2016

The theory of radiative-line driven wind including stellar rotation is re-examined. After a suitable change of variables, new analytical equations for the mass loss rate and position of the critical point are derived. A non-linear equation for the position of the critical point is obtained, in order to solve it, a β-field is used, and in addition to the standard CAK critical point two other critical points as function of star’s rotational speed (Vϕ) are founded. When the stellar rotation velocity is approximate or greater than 0.8 × Vbreak–up, the CAK critical point is located far away in the wind (r > 4R*) and there we have again only one critical point. Numerical solutions from this new critical point are obtained, they have very low terminal velocities (approx. 400 km/sec). The applicability of this new solution in the frame of Be stars are discussed.
Glimpses of Be Binary Evolution
Authors: Gies Douglas R.
Published: July 2016

Models of close binary evolution predict that mass gainers will be spun up to speeds close to the critical rotational velocity while the mass donors will appear as stripped down He stars, white dwarfs, or neutron stars. I argue here that the mass gainers are closely related to the Be stars. I present a list of the known Be binary systems which consists of those with bright, Roche-filling companions and those with faint or undetected companions. Notably absent are Be + B systems which are expected if the Be phase is a stage in the life of a single star. We now have the first example of a Be + He star system in the binary, ϕ Per, and taken together with the well known Be X-ray binaries, there is clear evidence that some fraction of Be stars are created in binaries; whether all such rapid rotators are so formed remains unknown.
Origin of Circumstellar Matter in the Spectroscopic Binary CX Dra
Authors: Iwamatsu Hidetoshi , Hirata Ryuko , Masuda Seiji
Published: July 2016

We examine the periodic component in the polarization of CX Dra, a spectroscopic binary with an orbital period of 7 days. We find that this component originates in dense matter located in the direction preceding the secondary by about 4.5° from the primary-secondary direction. This dense scattering region is attributable to the region where the Hα emission peak is formed, i.e. the gas stream or hot spot on the accretion disk of the primary. Its mass is estimated as 1.3 · 10−11M⊙ in its well developed phase.
The Spectral Distribution of Be/X-ray Transients Implies Supernova Kicks
Authors: Negueruela Ignacio
Published: July 2016

Be/X-ray binaries are generally assumed to have formed as the result of the evolution of moderately massive binaries in which mass is transferred semi-conservatively from the originally more massive component on to its companion. An alternative model proposes a binary system with a very massive component which loses a large fraction of its mass via very unconservative mass transfer. This scenario allows the formation of Be/X-ray binaries without requiring an asymmetric supernova explosion. We show that the observed properties of most Be/X-ray binaries for which an orbital solution has been found are incompatible with this model.
Summary and Future Directions
Authors: Marlborough J. M.
Published: July 2016

A summary of the Alicante meeting, entitled The Be Phenomenon in Early Type Stars, is presented here. The emphasis at this meeting was on Be stars, but possible connections to other types of stars were also considered. Some suggestions for the directions of future approaches are provided. The meeting was dedicated to the late Mercedes Jaschek, Carlos Jaschek, and Arne Slettebak, all of whom made significant contributions to our current understanding of Be stars.
New Pulsars from Arecibo Drift Scan Search
Authors: Somer A.
Published: July 2016

We report the discovery of 3 pulsars, PSR J0030+0451, PSR J0711+09, and PSR J1313+09 that were found in a three dimensional (DM, period, position) search at 430 MHz using the 305m Arecibo telescope. PSR J0030+0451 is a nearby 4.8-millisecond solitary pulsar. Spin and astrometric parameters are presented for the three new pulsars. We have measured significant polarization in the millisecond pulsar, PSR J0030+0451, over more than 50% of the period and use these data and also a morphological decomposition of the profile to briefly discuss magnetospheric models.
The Effelsberg Search for Pulsars in the Galactic Centre
Authors: Kramer M. , Klein B. , Lorimer D. , Müller P. , Jessner A. , Wielebinski R.
Published: July 2016

We report the status of a search for pulsars in the Galactic Centre, using a completely revised and improved high-sensitivity double-horn system at 4.85-GHz. We also present calculations about the success rate of periodicity searches for such a survey, showing that in contrast to conclusions in recent literature pulsars can be indeed detected at the chosen search frequency.
Pulsar Timing at the Radiotelescope Effelsberg
Authors: Lange Ch. , Wex N. , Kramer M. , Doroshenko O. , Backer D.C.
Published: July 2016

We present results of timing observations, obtained at the 100 m-Radiotelescope Effelsberg since 1994. The quality of the pulse arrival times, recorded with the coherent de-disperser EBPP since October 1996, is excellent. Our TOAs are well suited for the measurement of binary parameters of binary pulsars with short orbital periods. Some results are presented.
The microlensing probability of the pulsars located in globular clusters
Authors: Larchenkova Tanya
Published: July 2016

We have used the effect of Shapiro delay of the pulsar radiation in the gravitational lensing approximation. The microlensing probabilities for pulsars located in globular clusters 47 Tuc (NGC 104) and M15 (7078) in the case of rather large impact parameters was calculated.
Evidence for Free Precession in the Pulsar B1642–03
Authors: Shabanova T.V. , Urama J.O.
Published: July 2016

The phase residuals of PSR B1642-03 obtained during a 30-yr interval since 1969 to 1999 are discussed. Interpretation of observed cyclical residual changes in terms of free precession gives a wooble angle of 0.3 - 0.7 degrees.
Glitches in Southern Pulsars
Authors: Wang Na , Manchester R. N. , Pace R. , Bailes M. , Kaspi V. M. , Stappers B.W. , Lyne A. G.
Published: July 2016

Parkes timing observations of 31 mostly young pulsars over nearly nine years are described. A total of 29 glitches were detected, of which 19 are previously unreported. Twelve glitches were seen in PSR J1341–6220, making this the most frequently glitching pulsar known, and the largest known glitch was detected in PSR J1614–5047. Distributions of glitch parameters were investigated.
Geodetic Precession and the Binary Pulsar B1913+16
Authors: Karastergiou A. , Kramer M. , Wex N. , von Hoensbroech A.
Published: July 2016

A change of the component separation in the profiles of the binary pulsar PSR B1913+16 has been observed for the first time (Kramer 1998) as expected by geodetic precession. In this work we extend the previous work by accounting for recent data from the Effelsberg 100-m telescope and Arecibo Observatory and testing model predictions. We demonstrate how the new information will provide additional information on the solutions of the system geometry.
Numerical solution of the spin angular momenta of millisecond pulsar PSR J0751+1807
Authors: Gong B.P. , Cheng K.S.
Published: July 2016

The motion of the binary pulsar PSR J0751+1807 is assumed to satisfy the gravitational two-body equation (Barker and O’Connell 1975). Then by studying the motion of the binary system from initial state which determined by 3 precession phases of angular momenta (the orbit, the pulsar and the companion star) to the current state which determined by the observations on the orbital inclination. The spin angular momenta of the pulsar and the companion star are obtained.
VLBI Neutron Star Astrometry: Techniques and Initial Results
Authors: Chatterjee Shami , Cordes James M.
Published: July 2016

We outline some new techniques being used and present initial results from a pulsar astrometry program at the NRAO Very Long Baseline Array (VLBA). We find a proper motion of 89.0±0.4 mas/yr and a preliminary parallax of 1.05±0.25 mas for B0919+06.
Timing noise as a source of discrepancy between timing and VLBI pulsar positions
Authors: Rodin A. E. , Ilyasov Yu. P. , Oreshko V. V. , Sekido M.
Published: July 2016

Pulsar positions obtained by VLBI and timing are compared. The difference between these positions is proven to be mainly due to timing noise. A new method which significantly reduces the difference have been developed.
Parameters of microstructure and noiselike intensity fluctuation in pulsar radio emission measured with submicrosecond time resolution provided by the S2 VLBI recording/playback system
Authors: Popov M.V. , Kondrat’ev V.I. , Altunin V.I. , Bartel N. , Cannon W. , Novikov A.Yu.
Published: July 2016

Three bright pulsars (B0950+08, B1133+16, and B1929+10) were observed with the 70-m radio telescope in Tidbinbilla at a frequency of 1650 MHz using the S2 Data Acquisition System which provided continuous recording of pulsar signals in two conjugate bands of B=16 MHz each. Parameters of microstructure have been analyzed using the predetection dispersion removal technique.
Ha, ha, ha, ha, staying alive, staying alive: A radio pulsar with an 8.5-s period challenges emission models
Authors: Young M. D. , Manchester R. N. , Johnston S.
Published: July 2016

We report the discovery of the longest known radio pulsar period. PSR J2144–3933, previously thought to have a period of 2.84 s, actually has a period of 8.51 s. Under the usual assumptions about the stellar equation of state, this pulsar has an average surface dipolar magnetic field strength of ~ 2.0 × 1012G. According to popular theories of the emission mechanism this pulsar should not be emitting radio waves because its long period and magnetic field strength make pair creation impossible for all reasonable magnetic field configurations. Either assumptions about the equation of state are incorrect, or the emission theories must be revised.
Measuring the Size of the Vela Pulsar’s Radio Emission Region
Authors: Gwinn C.R. , Reynolds J.E. , Jauncey D.L. , Hirabayashi H. , Kobayashi H. , Murata Y. , Edwards P.G. , Carlson B. , Dougherty S. , Rizzo D. Del , Britton M.C. , McCulloch RM. , Lovell J.E.J.
Published: July 2016

We describe the expected distribution of intensity for a scintillating source of finite size observed through a scattering medium, including systematic and instrumental effects. We describe measurements of the size of the Vela pulsar, using this technique.
Finding Pulsar Emission Heights from Dual–Frequency Observations
Authors: Nowakowski Leszek A.
Published: July 2016

We present a method that allows to find the radial separation of regions emitting individual components of pulsar average profiles at two radio frequencies. It may also be used for single–frequency observations in pulsars that have intensity–dependent average profiles and/or mode–switching. Preliminary results for three radio pulsars are presented, obtained using average profiles from non-simultaneous observations.
A VLA Search for the Geminga Pulsar at 74 and 326 MHz
Authors: Kassim Namir E. , Joseph T. , Lazio W.
Published: July 2016

We have used the VLA to image the location of the gamma-ray pulsar Geminga at 74 and 326 MHz. Upper limits to the pulse-averaged flux density, taking diffractive scintillation (DISS) into account, areS< 56 mJy (2σ; DISS quenched) at 74 MHz andS< 5 mJy (95% confidence) at 326 MHz. Intrinsic variability appears to be required in order to reconcile our upper limits with previous low-frequency detections.
Single Pulse Polarimetry of the Vela Pulsar
Authors: Kern Jeffrey S. , Hankins Timothy H. , Rankin Joanna M.
Published: July 2016

Multi-frequency, single-pulse polarimetric observations of the Vela pulsar have been made using the VLA. These high time resolution measurements allow us to probe the geometry, and the time dependent characteristics of the radio emission region. Evidence for multiple emission components with differing spectral indices is found.
Evolution of Multipolar Magnetic Fields in Isolated Neutron Stars and its effect on Pulsar Radio Emission
Authors: Mitra D. , Konar S. , Bhattacharya D. , Hoensbroech A. V. , Seiradakis J. H. , Wielebinski R.
Published: July 2016

The evolution of the multipolar structure of the magnetic field of isolated neutron stars is studied assuming the currents to be confined to the crust. Lower orders (≤ 25) of multipole are seen to evolve in a manner similar to the dipole suggesting little or no evolution of the expected pulse shape. We also study the multifrequency polarization position angle traverse of PSR B0329+54 and find a significant frequency dependence above 2.7 GHz. We interpret this as an evidence of strong multipolar magnetic field present in the radio emission region.