bluuebunny/crossref_metadata_2025 huggingface dataset:
The CTIO objective-prism survey and its vidicon observations of southern quasars
Authors: Osmer Patrick S. , Smith Malcolm G.
Published: July 2016

Nous avons étudié des quasars de grand décalage spectral avec deux nouvelles techniques: l’utilisation de plaques obtenues avec un prisme objectif de faible dispersion pour la découverte des quasars par la détection de Lα en émission, puis un tube vidicon SIT pour la spectrophotométrie des raies d’émission. Sur les 45 candidats observés jusqu’à présent, 24 ont des décalages spectraux compris entre 1.9 et 2.5 et 9 entre 2.5 et 3.1. Deux nouveaux quasars de magnitude 16 et de z~ 2.2 ont été découverts. Nous comparons la distribution des intensités et des largeurs des raies d’émission observées avec les modèles de photoionisation. Un des principaux résultats du programme du prisme objectif sera d’améliorer la détermination de la densité spatiale des quasars de z >2.5.
Optical Galaxy Selection
Authors: McGaugh Stacy
Published: July 2016

Our view of the properties of galaxies is strongly affected by the way in which we survey for them. I discuss some aspects of selection effects and methods to compensate for them. One result is an estimate of the surface brightness distribution. I believe this is progress, but considerable uncertainty remains.
Dwarf Galaxies as Low Surface Brightness Galaxies
Authors: Skillman Evan D.
Published: July 2016

Because of the weak correlation between surface brightness and luminosity, as galaxy surveys reach to lower surface brightnesses, increasing numbers of dwarf galaxies are found. Thus, studies of dwarf galaxies are relevant to our understanding of the low surface brightness universe. In particular, studies of nearby LSB dwarfs may help to answer questions concerning: (1) star formation in low abundance and low mass surface density envrionments, (2) star formation histories of galaxies and the relative youth of LSB galaxies, and (3) the chemical evolution of LSB galaxies. HST WFPC2 photometry of the resolved stars in nearby dwarf galaxies is particularly useful for all three questions.

H II region abundances remain the best probe of current ISM abundances. Current evidence favors total mass (or luminosity) as the primary factor for determining the present day chemical abundance in both LSB and HSB galaxies. It remains possible that mass surface density (or surface brightness) may be a second controlling parameter.
Gas-rich LSB Galaxies – Progenitors of Blue Compact Dwarfs?
Authors: Salzer John J. , Norton Stuart A.
Published: July 2016

We analyze deep CCD images of nearby Blue Compact Dwarf (BCD) galaxies in an attempt to understand the nature of the progenitors which are hosting the current burst of star formation. In particular, we ask whether BCDs are hosted by normal or low-surface-brightness dI galaxies. We conclude that BCDs are in fact hosted by gas-rich galaxies which populate the extreme high-central-mass-density end of the dwarf galaxy distribution. Such galaxies are predisposed to having numerous strong bursts of star formation in their central regions. In this picture, BCDs can only occur in the minority of dwarf galaxies, rather than being a common phase experienced by all gas-rich dwarfs.
Morphological aspects of star formation in dwarf galaxies
Authors: Brosch Noah , Heller Ana , Almoznino Elchanan
Published: July 2016

We studied the morphology of star formation in dwarf irregular galaxies and found that, in general, this takes place on one side of a galaxy and far from the center. This is mainly true for low surface brightness galaxies; in high surface brightness dwarf irregulars the star formation tends to be more centrally concentrated, as well as being more intense. We discuss possible star formation triggers in dwarf irregular galaxies, and evaluate the reasons for the peculiar distribution of star forming regions of these galaxies. Stochastic star formation, interactions with external gas, and tidal interactions appear to be ruled out as responsible for the asymmetric pattern of star formation. We conclude that asymmetry of a dark matter halo or of an asymmetric underlying stellar distribution may trigger an asymmetric pattern of star formation.
HI in Karachentsev Objects Properties of new nearby Dwarf Galaxies
Authors: Huchtmeier W.K.
Published: July 2016

This is a report on HI observations of newly discovered nearby dwarf galaxies, most of which of low surface brightness, from the first section of the Karachentsev catalog. Observations were performed using the 100-m radiotelescope at Effelsberg, the Nançay radiotelescope, and the compact array of the Australia Telescope. We observed 220 galaxies with a detection rate of about 60%. 35 of the observed galaxies are located within the Local Volume (i.e., within 10 Mpc). The smallest detected galaxies have diameters around 0.3 kpc and HI-masses of a few times 106 solar masses. We confirm a correlation between HI column density and surface brightness of gas-rich disk galaxies.
Using weak Mg II lines to chart Low Surface Brightness Galaxies
Authors: Le Brun V. , Churchill C.W.
Published: July 2016

We report the detection, based on HST and Keck data, of two peculiar absorbers in the Lyα forest of the quasar PKS 0454+039. These clouds, at redshiftsz= 0.6248 and 0.9315 respectively, display both Mg II and Fe II absorption lines in addition to the Lyα line. Based upon photoionization models, these are inferred to be photoionized by the intergalactic UV background, and to have H I column densities in the range 15.8 ≤N(H I) ≤ 16.8. Furthermore, if one supposes that the relative abundances of heavy elements is similar to that of depleted clouds of our galaxy, the abundances of these two absorbers are greater than the solar value, which is a unique case for absorbers which are not associated to the quasar. We tentatively suggest that these absorbers may select giant low surface brightness galaxies.
What We Don’t Know About the Universe
Authors: Impey Chris
Published: July 2016

Despite progress on many fronts in cosmology, outstanding questions remain. What is the nature of the dark matter? Is the inflationary big bang model viable? Must we accept a non-zero cosmological constant? Do we know the true population of galaxies? What is the range of star formation histories in the universe? Can gravity alone explain the large scale structure we observe? Studies of the low surface brightness universe may provide the answers to many of these questions.
A new compact groups sample in the southern sky
Authors: Iovino A.
Published: July 2016

Compact groups of galaxies are an extreme class of object, ideal for the study of galaxy interactions and their effects. In this paper we present a new algorithm, devised to select compact groups from digitized catalogues of galaxies and especially suited to reach fainter magnitudes. We present also the results obtained from the redshift survey of the bright subsample of such groups.
Properties of Dust in Giant Elliptical Galaxies: The rôle of the Environment
Authors: Goudfrooij Paul
Published: July 2016

The properties of dust in giant elliptical galaxies are reviewed, with particular emphasis on the influence of the environment.

After normalizing by the optical luminosities, a strong anticorrelation between the masses of dust and hot gas in X-ray bright ellipticals is found. Furthermore, large-scale, regularly-shaped dust lanes (which are symmetric with respect to the galaxy nucleus) are only found to be present in ellipticals with the lowest ratios of the mass of hot gas to the blue luminosity (Mhot/LB ≲ 0.04 in solar units). This can be explained by the short time scale for the destruction of dust grains within the hot, X-ray- emitting gas compared to the formation timescale of such dust lanes in early-type galaxies.

Dust within ellipticals in “loose” environments (i.e. in the field or in loose groups) is typically characterized by small values of RV ≡ AV/EB−V (i-e. small characteristic grain sizes), and distributed in dust lanes with a smooth, relaxed morphology. On the other hand, dust in ellipticals that are in or near the center of dense groups or clusters is typically much more irregularly distributed, and characterized by RV values that are close to the Galactic one.

I predict that ellipticals containing “relaxed” dust lanes with typical dust masses of 106 − 107M⊙ do not contain hot, X-ray-emitting gas.
Observational properties of galaxies in small systems
Authors: Jõeveer M.
Published: July 2016

The mean absolute luminosities and diameters of galaxies in double and triple configurations are compared with the same characteristics for single galaxies. Members of optical pairs and triplets are used as the sample of single galaxies. The mean luminosities of galaxies in physical pairs and triplets are found to be the same as for single galaxies. At the same absolute luminosity, single galaxies have larger diameters compared to galaxies in pairs and triplets.
Deep Optical Imaging of the Compact Group “Seyfert’s Sextet”
Authors: Nishiura S.
Published: July 2016

The compact group of galaxies “Seyfert’s Sextet” shows irregularly shaped soft X-ray morphology. In order to understand its origin, we have obtained a deep optical (VR + I) image of the group. Our image shows that a faint envelope surrounds the member galaxies. We find that optical and soft X-ray images are significantly similar in morphology. This similarity provides direct morphological evidence that the dark matter in Seyfert’s Sextet was originally associated with the individual galaxies and is now spreading out around the group.
On the Verge of Coalescence: a Dusty Group of Galaxies
Authors: Temporin S. , Weinberger R. , Kerber F.
Published: July 2016

We have found a new, very compact group of galaxies characterized by a median projected separation between galaxies of 5.2/h kpc and a very low velocity dispersion. All the observed member galaxies show emission line spectra and a disturbed morphology. From these properties it emerges that this compact group is in an extremely advanced stage of evolution.
Inventory of Galaxy Properties in Small Scale Structures
Authors: Tanvuia L. , Kelm B. , Focardi P. , Rampazzo R. , Zeilinger W. W.
Published: July 2016

We report on a broad-band R surface photometric and low resolution spectroscopic study of a set of galaxies located in small groups and pairs of galaxies considered to be in low density environment. Groups span a wide range in density and show different morphological mix. We are analyzing systemic velocities, photometric parameters and spectral properties of the dominant galaxies in the groups. Our aim is to investigate the connection between interaction and induced galaxy activity, from star formation to AGN activity.
Detection of hot plasma around M96 in the Leo-I group
Authors: Pedersen K.
Published: July 2016

The nearby (D = 11 Mpc) sparse group of galaxies, Leo-I, is in many respects unique. It is the nearest group containing both bright spirals (M96 and M95) and a bright elliptical (M105). A giant (diameter ca. 200 kpc) intergalactic Hɪ ring orbits the central M105/NGC3384 galaxy pair and appears to interact with M96. If M96 is really in the group core, the Leo-I group provides an unusually “clean” route to determining the Hubble constant. In our 22 ksec ASCA SIS exposure of M96 we have detected diffuse X-ray emission extending more than 10 arcminutes North of M96, in the direction of the Hɪ ring. The morphology and spectral characteristics of the diffuse emission shows that M96 has recently interacted with the Hɪ ring, indicating that M96, the Hɪ ring and the central galaxy M105 are at the same distance within a few percent.
Understanding low and high velocity dispersion compact groups
Authors: Mamon G. A.
Published: July 2016

A galaxy system must have a minimum velocity dispersion for its mass to be greater than the sum of the masses of its galaxies. Nearly half of the nearby Hickson compact groups (HCGs) have too low a velocity dispersion in comparison with the rotational velocities of their spiral galaxies and internal velocity dispersions of their early types.

A detailed study of the low velocity dispersion group, HCG 16 – the only known group of late-type galaxies with diffuse intergalactic X-ray emitting hot gas – reveals that half of the diffuse X rays are associated with foreground/background sources and the remaining gas is clumpy and mostly associated with the bright galaxies of the group. The large-scale environment of the group suggests that HCG 16 lies where a cosmological filament falls perpendicularly onto a large-scale sheet.

The observed frequency of compact groups is lower than predicted from the extended Press-Schechter formalism, which also predicts that most 1013 M⊙ objects in the Universe must be fairly old and hence have already coalesced into single objects, reminiscent of elliptical galaxies over-luminous in X-rays that are now being discovered.

Thus, the low survival time of dense groups against the merging instability is no longer a worry for compact groups, as they form in large enough numbers. I show why other arguments against the reality of HCGs no longer hold, partly because of the biases of Hickson’s sample.
Stephan’s Quintet: Implications for Compact Groups
Authors: Sulentic Jack W.
Published: July 2016

We review old and new observational data for Stephan’s Quintet (SQ), the most famous compact galaxy group. Recently obtained multi-wavelength data has helped to clarify the past and present evolutionary history of this group. If SQ is typical of the compact group phenomenon, then: 1) the groups evolve slowly, resisting merging, due to the injection of energy from high velocity intruders and 2) show low levels of enhanced star formation because individual component ISM’s are quickly stripped via intruder collisions with resultant gas either too hot or cold/diffuse to form many stars. Infall of residual near nuclear gas may also stimulate the development of AGN.
Minor Mergers and the Formation of Shell Galaxies
Authors: Charmandaris V. , Combes F.
Published: July 2016

We present a new mechanism which can explain the observed radial displacement between the stellar and gaseous shells observed around early type galaxies. Our model is based on the well-known phasewrapping process taking into account that a fraction of the interstellar medium is clumpy and consequently it experiences a low dynamical friction during a merging event. Moreover, our recent detection of cold molecular gas associated with the outer shells of Centaurus A is in agreement with the proposed model. This suggests that a considerable fraction of molecular gas in minor mergers may be distributed away from the nuclear regions and remain undetected.
Masaai warrior shield: The life time of a three body system
Authors: Lehto Harry J. , Heinämäki Pekka , Chernin Arthur D. , Valtonen Mauri J.
Published: July 2016

We have investigated the behavior of a general Newtonian three body system using the simplest initial conditions. We calculated the evolution of about a million bound three body systems. Within our resolution these cover all the possible initial states. All these systems eventually decay with one body being ejected from the residual binary system. The overall pattern representing the decay time scales projected on a homology map is dominated by resonances. In general appearance it reminds us of a traditional Masaai warrior shield.
NGC 7479 — the Rosetta stone of minor mergers?
Authors: Laine S.
Published: July 2016

The overall morphology of the barred spiral galaxy NGC 7479 was modelled numerically in a simple minor merger scenario. I paid special attention to the morphology and features of the velocity field along the dominant spiral arm. The mass of the merging companion was 1/30 of the total mass of the primary. The companion was started in a circular prograde orbit at six disk scale lengths from the centre of the primary. I followed the evolution of the merger until the companion had reached the nuclear region of the primary. A comparison between the modelled and observed morphologies of the stellar and the ionized and neutral gas distributions and velocity fields suggests that the transient look of NGC 7479 is a result of a minor merger. I also tested the effects of variations in several initial parameters of the merger. See Laine and Heller, 1999, for further details.
Star Formation and Environment in Compact Groups of Galaxies
Authors: Iglesiás-Paramo J. , Vílchez J. M.
Published: July 2016

Hα luminosities are presented in order to study the Star Formation Rates (SFRs) of a sample of galaxies in compact groups from Hickson's (1982) catalogue. Although the comparison of the SFRs of the disk galaxies in our sample with those of a sample of field galaxies yielded no difference between the average SFRs for disk galaxies in compact groups and in the field, environmental effects seem to influence the Hα luminosities of late and early-type galaxies in compact groups. No relationship was found between the total normalized Hα luminosities of the groups and some dynamical parameters, indicating that the dynamical state of the group does not influence the SFR of the group. The lack of dominant interaction induced starbursts in our sample is compatible with a scenario for compact groups of galaxies in which the dark matter of the group is arranged in a common halo, thereby preventing a fast collapse of the galaxies.
Milky Way Rotation Models from Neutral Hydrogen and Molecular Clouds: Galactic Constants, Common Details and Differences
Authors: Nikiforov Igor’ I.
Published: July 2016

Kinematic data from neutral hydrogen observations provide information to solve the interdependent problems of the determination of the main Galactic constants (the Solar-Galactic center distance R0, the Oort constant A and others) and the Galactic rotation curve (Nikiforov & Petrovskaya 1994, hereafter NP94, and references therein). However, in the standard method for finding R0 by comparing the rotations of HI clouds and some other objects (typically HII regions/CO clouds), the kinematic model, constructed typically solely from HI data, is considered to be the same for both galactic subsystems (e.g. Merrifield 1992). In practice a discrepancy between their rotation curves can produce strongly erroneous results (Merrifield 1992, NP94). Establishing the common rotation law from HI plus HII/CO data in NP94 is only a part of attacking the problem.
On the Initial Mass Function of Be Stars and the Missing Be Stars of Late Spectral Types
Authors: Zorec J.
Published: July 2016

This is an attempt at determining the IMF (Initial Mass Function) of Be stars relative to that of B stars in the vicinity of the Sun. We have represented the IMF as a power function of the stellar mass Mβ, so that the relative IMF is then proportional to Mβ(Be)–β(B). Allowing for systematic differences in the counting of Be stars due to their apparent overluminosity, a difference β(Be) – β(B) ~ 0 is found, which may indicate that there are no huge intrinsic differences between the two types of objects. In these calculations changes of spectral types due to high rotation were not taken into account. This effect may still strongly affect the results obtained. By extrapolating the MβBe) – β(B) curve to spectral types later than B7, we reckon that in a volume limited to the apparent magnitude V = 7 there may be about 150 still undetected Be stars of late spectral types.
Spectroscopic Investigations of the Main-Sequence B Stars in the Association Cas OB2 and the Open Cluster Platais 1 (C2128+488)
Authors: Usenko I.A. , Kovtjukh V.V. , Andrievsky S.M. , Klochkova V.G. , Panchuk V.E. , Ermakov S.V.
Published: July 2016

A spectroscopic investigation of four main-sequence stars in the association Cas OB2 (HD 17327A and B, HD 16893, HD 17443) and of two stars in the open cluster Platais 1 (No. 1 (1921) and No. 111 (1600)) was carried out using high-resolution CCD spectra, obtained with echelle-spectrometer ”LYNX” (6-m telescope, Special Astrophysical Observatory, Russian Academy of Sciences). We have determined the atmospheric parameters for the program stars, their projected rotational velocities and elemental abundances in their atmospheres. Two new HgMn stars - HD 17327A and Platais No. 1 - were detected. HD 17443 is not a Be star.
The Be Phenomenon in A-type Supergiants
Authors: Verdugo Eva , Talavera Antonio , de Castro Ana I. Gómez
Published: July 2016

Multiwavelength observations of a large sample of A-type supergiants reveal that these stars display several features associated with the classical Be phenomenon.
Long-Term Variability in the Winds of λ Eridani and 66 Ophiuchi
Authors: Peters Geraldine J.
Published: July 2016

Variations in the winds of the Be stars λ Eri and 66 Oph during the lifetime of the IUE spacecraft and the response of the Hα-emitting disk to these changes are briefly discussed. Common behavior is identified and evidence for cyclical variability on a time scale of ∼1 yr is presented.
Multiperiodic Variability and Outbursts of 28 Cygni
Authors: Tubbesing S. , Rivinius Th. , Wolf B. , Kaufer A.
Published: July 2016

28 Cygni was observed during two seasons spectroscopically. The radial velocities of more than 15 spectral lines were measured and searched for periodic variability. Two closely spaced periods were found. A two-dimensional analysis of the line profile variability yielded the same periods and provided the power and phase distribution across the line profiles. An outburst covered by our data coincides with the time of constructive interference of both periods. 28 Cyg is the second case for which outbursts seem to be triggered by multi-mode beating.
On the Excitation Mechanism for the Nonradial Pulsations in ϵ Persei
Authors: Kambe Eiji , Saio Hideyuki , Lee Umin
Published: July 2016

We have examined whether the kappa-mechanism at the ”Z” opacity bump can excite overstable nonradial pulsation (NRP) modes such as those responsible for the line-profile variations (lpv) observed for ϵ Persei (Gies et al. 1999).

From the lpv modeling with realistic stellar parameters and the state-of-the-art codes, we confirmed that the observed lpv can generally be explained by the modes with l values suggested by Gies et al. (1999). We have also found that some tesseral modes, which have smaller m than those of sectoral modes, can reproduce the observed lpv well for the periods of 3.51hr/3.84 hr and 4.06hr/4.54 hr. Our linear non-adiabatic nonradial pulsation analysis applied to massive (13M⊙––14M⊙) stars shows that the periods of higher |m| values in the co-rotating frame are too long to be excited by the Z-bump kappa-mechanism while the smaller |m| values give marginal consistency.
Recent Spectroscopic Evidence for Aperiodic Activity in Classical Be Stars
Authors: Smith Myron A.
Published: July 2016

This review focuses on aperiodic line profile activity in several Be stars, ignoring attributes of pulsations probably occurring in any of the stars studied. Herein, I discuss spectroscopic evidence of heating (and cooling) of regions of Be star atmospheres, of line profile transients called dimples and high velocity absorptions. These features will be interpreted in terms of mass ejections (not necessarily permanent). Some of these events are violent and spasmodic, some are ordered and quasisteady, and some are associated with downflows. I close with new evidence for time-varying, corotating clouds suspended over a few Be stars.
Can Magnetic Fields Be Detected in Be Stars?
Authors: Mathys Gautier , Smith Myron A.
Published: July 2016

The results of observations aimed at detecting magnetic fields in the Be star λ Eri are reported. The observational data are analyzed both through application of an approximate analytical method and through computation of a number of simple numerical models in view of deriving constraints on the magnetic fields. General conclusions are drawn about future prospects for magnetic field detections in Be stars.
Surface Magnetic Fields in Early-Type Stars
Authors: Airapetian V. S.
Published: July 2016

Recent observations imply magnetic activity in atmospheres of early-type stars. We explore the possibility that stressed surface magnetic fields can be driven by inertial oscillations, such as r-modes which are vorticity waves. We show that vorticIAL MOTIOns are able to supply helicity to drive magnetic activity in stellar atmospheres.
Chinese and Japanese Participation in B/Be Star Campaigns
Authors: Hao J.
Published: July 2016

In the early 1980’s, astronomers at the Beijing Astronomical Observatory (BAO) entered a collaboration in a long term photometric observing project on Be stars which included about 30 stars. For example, in 1983 the group at BAO organized a multi-site campaign to measure the short term variability of EW Lac, KX And, KY And, o And, and LQ And. In 1989, 48 Per was selected to be one of the targets of MuSiCoS campaign in which many stellar astronomers at the BAO participated. In 1991, the Be group at the BAO joined a campaign on the prototypical nonradially pulsating B star, 53 Per. In 1992, French & Chinese astronomers proposed a joint campaign on o And and EW Lac. Astronomers in Japan are also active in Be star campaigns and in 1993-5 they organized several campaigns on few well known Be stars (ζ Oph, EW Lac, ϒ Cas, λ Eri and 28 Cyg).
Results from MuSiCoS Campaigns on Be stars
Authors: Henrichs H.F. , Neiner C. , Hubert A.M. , Floquet M. , Team MuSiCoS ,   and MuSiCoS Team
Published: July 2016

The contribution of the MuSiCoS project (a multisite network of 2m class telescopes) to Be-star research is summarized. Some preliminary results of the 1998 campaign on ω Ori are shown.
Polarization from Be Disks with 1-Armed Density Waves
Authors: Ignace R.
Published: July 2016

The polarization of Be disks that are not axisymmetric is discussed, with results given for one-armed density waves or global disk oscillations (GDO). Polarimetric diagnostics of electron scattering Be disks are presented, including the expected behavior at (a) optical wavelengths where the star is the dominant source of luminosity and (b) infrared wavelengths where the disk is more luminous than the star. Results for detached disks are given. A qualitative discussion of polarization at Hα is also presented.
Reflections on Scattered Light: Monte Carlo Simulations of the Flux and Polarization Curves of β Lyrae
Authors: Hoffman Jennifer L. , Whitney Barbara A. , Nordsieck Kenneth H.
Published: July 2016

Polarimetry has proven to be a useful observational tool in the study of Be stars. In recent years, Monte Carlo radiative transfer methods have often been used in modeling polarimetric measurements, since they allow accurate predictions of flux and polarization via numerical simulation of the interaction of light with matter, even in systems with complex configurations. We have extended these two complementary techniques to the investigation of binary Be stars by developing a Monte Carlo code that models the flux and polarization phase curves of a binary-disk system. We here present the latest results matching geometrical model configurations with our own spectropolarimetric observations of the Algol binary β Lyrae.
On the Characteristics of Circumstellar Envelopes in Be Stars near the Central Object
Authors: Moujtahid A. , Zorec J. , Hubert A.M.
Published: July 2016

Observed visible energy distributions of Be stars were studied with analytic flux distributions produced by flattened circumstellar envelopes. The theoretical representation of emitted fluxes also allows for density distribution effects in the region where the visible continuum emission/absorption is raised. Two main conclusions were reached: (a) regions responsible for spectrophotometric ”shell” phases have, on average, steeper density distributions than those producing the spectrophotometric ”Be” phases; (b) the mean temperatures of the studied circumstellar envelope regions shows a linear relation with their mean ”inverse” extent R*/R.
Correlated Spectroscopic and Spectrophotometric Behaviours of Be Stars
Authors: Moujtahid A. , Hubert A.M. , Zorec J. , Ballereau D. , Chauville J. , Floquet M. , Mon M.
Published: July 2016

Correlations between long-term spectrophotometric and optical spectroscopic variations are investigated in some Be stars. Using spectrophotometric variations as a function of time and a compilation of spectroscopic measurements, we investigated temporal variations of emission and shell line parameters. In some cases time lags between spectroscopic and spectrophotmetric variations could be estimated. We could not find precise relations between the spectroscopic and spectrophotometric behaviours, but a number of tendencies could be derived which give information on physical parameters of circumstellar envelopes in Be stars.
The Emitting Envelope of Pleione between 1987 and 1998
Authors: Ballereau D. , Chauville J. , Zorec J. , Morrell N.
Published: July 2016

We analyze a series of spectroscopic observations of the Hβ and Fe II λ4924Å lines of the Be-shell star Pleione (HD23862), which entered a new Be phase since 1988. Their evolution show that the Hβ-emitting envelope expands regularly from 1987 to 1996 (r/r*=8.6 to 25.0), then diminishes slightly in 1997-98 (r/r*=20.0). The Fe II-emitting envelope expands regularly between 1987 and 1998 (r/r*=6.7 to 13.4), but remains always inside the Hβ-one. The evolution of the emitting envelope of Pleione is similar to the one observed between 1954 and 1972, and this one should decrease regularly in the next years, if the former scenario is repeated.
IUE Spectra of Be Star CX Dra: Evidence for Winds
Authors: Škoda Petr , Koubský Pavel
Published: July 2016

The Be binary star CX Dra has been observed with the IUE satellite over a period of 14 years. More than 60 SWP high resolution spectra were obtained. After processing the quotient flux spectra of the Al III and Si IV lines show very complicated behaviour. The most important features are the violet shifted components in these lines which show very negative velocities (up to −800 km/s) in a particular phase interval.
X Per in 1996 - 1999: the Variability of Hydrogen and Helium lines
Authors: Kolka I. , Eenmäe T. , Puss A. , Leedjärv L.
Published: July 2016

We present the results of high-resolution (0.24Å/pix) monitoring of the variability of Hα and He I 6678 lines in the spectrum of X Per in 1996-99 at Tartu Observatory. The main characteristics of the line variability distinguishable in our data are:

1) the intensity of emission peaks in both lines varies with a cycle-length ≈450 days, and displays a phase-lag between curves of two lines considered,

2) in a cycle, both violet or red emission peaks emerge at high Doppler velocities but attain their maxima and disappear gradually at much lower velocities,

3) despite of the considerable variability of equivalent width (EW) of both lines, the “relative emission measure” (EW(Hα)/EW(HeI)) behaves more constantly.
Energy Balance in Circumstellar Envelopes
Authors: Millar C. E. , Marlborough J. M. , Sigut T. A. A.
Published: July 2016

We have successfully determined the kinetic temperature of the electron gas as a function of position in the circumstellar envelopes of Be stars. Our method yields a self-consistent solution of the equation for energy conservation, thus eliminating the necessity to assume arbitrarily a temperature for the gas. Our technique has been applied to Be stars of differing spectral classes, and we have also used several models for the distribution of the circumstellar material. The observed shape and relative line strength of the Hα line for several Be stars were matched successfully with these models. Recently we have begun to investigate the role of the diffuse radiation field in the Lyman continuum using the on-the-spot approximation. As a preliminary step to including metallic line cooling by the circumstellar gas, we have determined iron ionization fractions throughout the disks of both an early-type and a late-type Be star.
A Simple Spectropolarimetric Temperature Diagnostic for Circumstellar Disks
Authors: Bjorkman Karen S. , Bjorkman Jon E. , Wood Kenneth
Published: July 2016

We describe a technique for estimating average temperatures of Be star disks from analysis of ultraviolet spectropolarimetry. The technique utilizes the fact that the spectrum of the scattered starlight is sensitive to the circumstellar opacity, and hence temperature, since the signature of the disk material is imprinted on the scattered light spectrum. Analysis of the polarization spectrum thus allows us to disentangle the relative contributions of the star and disk, and thereby obtain an estimate of the average disk opacity as a function of wavelength. Using an LTE line-blanketed model (containing about 106 spectral lines) for the opacity, we determine a theoretical opacity as a function of temperature. By comparing this to the opacity deduced from the spectropolarimetry, we can estimate the average disk temperature. For classical Be stars, the relative strengths of the Fe II and Fe III multiplets at around 2400Å and 1900Å, respectively, are a sensitive temperature diagnostic, so that the temperature estimate can be made within ±1000K. We demonstrate our technique with analysis of UV spectropolarimetry (from WUPPE) of the classical Be star ζ Tau, for which we infer an isothermal disk temperature of14000K.
Be Star Discs: Inflow or Outflow?
Authors: Porter John M.
Published: July 2016

It is assumed that the dynamics of Be star discs is dominated by the effects of viscous stresses. By examining angular momentum transport in discs, we show that many, if not all observed Be star discs should be accretion discs unless (i) the disc is acted upon by another agent (e.g. magnetic fields or the stellar radiation field), or (ii) the disc cools significantly as it flows outwards.
Searching for New Be/X–ray Binaries in the SMC: the case of 1SAXJ0103–7209, XTEJ0055–724, RXJ0052–7319, XTEJ0111–7317 and 2E0050–7247
Authors: Covino S. , Israel G.L. , Polcaro V.F. , Campana S. , Mereghetti S. , Stella L.
Published: July 2016

We obtained X–ray (ROSAT, BeppoSAX and ASCA) and optical observations of a sample of newly discovered X–ray pulsars. We here report on the discovery of the likely optical counterpart of five of them in the Small Magellanic Cloud: 1SAXJ0103–7209, XTEJ0055–724, RXJ0052–7319, XTEJ0111–7317 and 2E0050–7247.
Gas-Dynamical Modelling of Circumstellar Matter in β Lyr A
Authors: Bisikalo D. V. , Boyarchuk A. A. , Harmanec P. , Hadrava P. , Kuznetsov O. A.
Published: July 2016

Available spectroscopic evidence of various circumstellar gaseous structures in the well-known binary β Lyr is confronted with the results of 3-D gas-dynamical simulations of mass transfer between the binary components, obtained for the currently best available basic physical properties of the system. It appears that the gas-dynamical model is capable to explain, at least qualitatively, the formation of all basic observed components of the circumstellar matter, including the jet-like structures, recently found from interferometry and polarimetry of the object.
Searching for New Be/X-ray Binaries in the Galactic Plane: the Case of GS 0834 – 43, 1WGA J1958.2+3232 and AXJ1820.5–1434
Authors: Israel G.L. , Covino S. , Polcaro V.F. , Campana S. , Mereghetti S. , Pizzella A. , Roche P. , Stella L. , Verrecchia F.
Published: July 2016

Over the last year we obtained X-ray (ROSAT, BeppoSAX and ASCA) and optical (at ESO and at the Astronomical Observatory of Loiano) to infra-red (AAO) observations of a sample of newly discovered X-ray pulsars. Among this sample we discovered the likely optical counterpart of three of them located in the Galactic plane: GS 0834–43, 1WGA J1958.2+3232 and AX J1820.5–1434.
The Parkes Multibeam Pulsar Survey Data Release
Authors: Bell J.F. , Manchester R.N. , Crawford F. , Lyne A.G. , Camilo F. , Kaspi V.M. , Stairs I.H. , Morris D.J. , D’Amico N. , McKay N.P.F. , Kramer M. , Sheppard D.C. , Possenti A.
Published: July 2016

The Parkes multibeam pulsar survey which began in 1997 and is now about 50% complete. It has discovered more than 400 new pulsars so far, including a number of young, high magnetic field, and relativistic binary pulsars. Early results, descriptions of the survey and follow up timing programs can be found in papers by Lyne et al. (1999 MNRAS in press), Camilo et al. (this volume), and Manchester et al. (this volume). This paper describes the data release policy and how you can gain access to the raw data and details on the pulsars discovered.
Science with PuMa, the new Dutch PulsarMachine
Authors: Kouwenhoven M.L.A. , Stappers B.W. , Ramachandran R. , Voûte J.L.L.
Published: July 2016

We have built a pulsar machine (PuMa) for operation at the Westerbork Synthesis Radio Telescope. The combination of PuMa and WSRT is capable of many types of pulsar research. We show the coherent dedispersion capabilities and the flexible frequency resolution. We discuss pulsar searching and simultaneous multifrequency observations.
The Bologna submillisecond pulsar survey
Authors: D’Amico Nichi
Published: July 2016

Since the discovery of the original millisecond pulsar, no pulsars with a shorter spin period (P<1.56 ms) were found. However, according to the most popular equations of state, the theoretical limiting spin period of a neutron star can be much shorter. On the other hand, most of the large scale searches for millisecond pulsars carried out so far were strongly biased against the detection of ultrashort periodicities. In this paper we describe a new large scale pulsar survey with a minimum detectable period much shorter than previous searches.
A Search for Sub-millisecond Pulsations in Unidentified FIRST and NVSS Radio Sources
Authors: Crawford Fronefield , Kaspi Victoria M. , Bell Jon F.
Published: July 2016

We have searched 92 unidentified sources from the FIRST and NVSS radio catalogs for pulsations at 610 MHz. The selected sources are bright, have no identifications, are unresolved and have significant linear polarization. Our search was sensitive to sub-millisecond pulsations from pulsars with a large range of dispersion measures. We have detected no radio pulsations from these sources and conclude that they are unlikely to be a population of previously undetected pulsars.
Pulsar timing measurements with the 32-m TCfA radiotelescope
Authors: Lewandowski W. , Konacki M. , Redmerska M. , Feiler G. , Wolszczan A.
Published: July 2016

Accurate, long-term timing measurements of pulsars provide a powerful method to study a variety of astrophysical phenomena. For “normal”, slow pulsars, the dominant factors that limit the timing precision are the intrinsic timing noise and single pulse “jitter” (e.g. Cordes 1993). In fact, because the pulse jitter surpasses radiometer noise for sufficiently strong pulsars and no further improvement of the timing precision can be achieved by increasing the antenna gain, the timing of such sources can be very efficiently conducted with suitably equipped medium-size radiotelescopes.

We have been timing slow pulsars with the 32-m TCfA radiotelescope in Toruń, Poland, since July 1996, using a dual-channel, circular polarization L-band receiving system at frequencies around 1.7 GHz, and a 2 × 64 × 3 MHz channel pulsar backend, the Penn State Pulsar Machine - 2 (PSPM-2; for more details, see Konacki et al. 1999). Our gradually expanding source list currently includes 88 pulsars timed once a week with a millisecond precision using the observatory’s UTC-calibrated H-maser clock. Data analysis is routinely performed with the TEMPO software package. With a particularly dense, weekly sampling and a ≤1 ms timing precision, the TCfA program has a sensitivity to detect previously overlooked short period, low orbital inclination binaries, as well as very low-mass, planetary companions. In addition, it will be very useful in identifying and monitoring pulsar timing glitches and other forms of the timing noise.
Binary Eclipsing Millisecond Pulsars: A Decade of Timing
Authors: Nice David J. , Arzoumanian Zaven , Thorsett Stephen E.
Published: July 2016

We present results of long-term timing of eclipsing binaries PSR B1744–24A and PSR B1957+20 at Arecibo, the VLA, and Green Bank. Both pulsars exhibit irregularities in pulsar rotation and orbital motion. Increases and decreases of the orbital period of PSR B1957+20 are of order ΔPb/Pb∼ 10−7, varying on a time scale of a few years. Over a decade of observations, the orbital period of PSR B1744–24A has only decreased, with time scale |Pb/Ṗb| ∼ 200Myr. When the effects of orbital motion are removed from the timing data, long-term trends remain in the pulse phase residuals, with amplitudes of order 30 and 500μs, respectively, for B1957+20 and B1744–24A. Such large “timing noise” is not seen in other spun-up pulsars (isolated or binary), leading us to conclude that it is a consequence of mass flow in the system. Possible causes include variations in the rotation of the pulsars and movement of the binary systems along the line of sight (perhaps due to gravitational interactions with outflowing matter).
Semi-analytical theory of motion for the PSR B1257+12 planetary system
Authors: Konacki Maciej , Maciejewski Andrzej J. , Wolszczan Alex
Published: July 2016

A planetary system around the pulsar B1257+12 has three planets A, B and C with the orbital periods of 25, 66 and 98 days, respectively (Wolszczan 1994). Dynamical properties of the system have been thoroughly studied by Rasioet al. (1993) and Malhotra (1993). They demonstrated that the gravitational interactions between planets B and C are significant enough to be detected. In such case, the motion of the system is no longer Keplerian and it is necessary to use a more precise description of motion in order to model the data properly. In this paper we derive a semi-analytical theory of motion assuming that the relative inclination of the orbits is small. We perform numerical simulations to show that our theory sucessfully predicts times of arrival of pulsar pulses and allows a determination of orbital inclinations and hence the masses of planets B and C.
Pulsar timing noise spectra of pulsars 0834+06, 1237+25,1919+21, 2016+28 from 1978 – 1999 yrs. observations
Authors: Ilyasov Yu.P. , Potapov V.A. , Rodin A.E.
Published: July 2016

The long time series of observations of four pulsars made by the Pushchino Large Phased Array are analyzed to describe a pulsar timing noise. The analysis was made after making a standard fitting procedure.
The Noise Structure of Pulsar Clocks
Authors: Kundt Wolfgang
Published: July 2016

Pulse arrival times of pulsars have a high – though limited – degree of predictability: they show both discrete ‘glitches’, and continuous deviations from an analytic extrapolation of earlier data spans; they are ‘noisy’. This noise shows a strong dependence on a pulsar’s spindown age. Both types of noise can be understood as due to a loose coupling of the charged component of a pulsar’s moment of inertia to a neutral superfluid component, of relative moment of inertia usually below 1%, but reaching 10% in extreme cases. Differential spin ratesδΩ/Ω of the two components are ≲ 10−3, usually only ≲ 10−5.
Binary Pulsar Tests of General Relativity in the Presence of Low-Frequency Noise
Authors: Kopeikin Sergei M. , Potapov Vladimir A.
Published: July 2016

The influence of the low-frequency timing noise on the precision of measurements of the Keplerian and post-Keplerian orbital parameters in binary pulsars is studied. Fundamental limits on the accuracy of tests of alternative theories of gravity in the strong-field regime are established. The gravitational low-frequency timing noise formed by an ensemble of binary stars is briefly discussed.
Pulse Properties of a few Southern Pulsars at 150 MHz
Authors: Issur Nalini H. , Deshpande Avinash A.
Published: July 2016

We present 150 MHz observations of the bright millisecond pulsar J0437-4715, and pulsars J1453-6413 and J1752-2806, made with the Mauritius Radio Telescope (MRT). We use single-pulse sequences to derive some preliminary results on the pulse morphologies.
The Geometry Asymmetry of Mean Pulse Profile of Pulsar
Authors: Wu X.J. , Pan J. , Xu X.B.
Published: July 2016

In this paper, the effects of aberration, retardation and magnetic field sweep back, which are caused by pulsar’s rapid rotation, are estimated to see their influences on the pulse shape of pulsars and geometry asymmetry of the mean pulse profile. The width of mean pulse profile is modified only slightly, but the geometry asymmetry appears and will exhibit different behaviors at different cases. The pulsars of B1451-68 and J0437-4715 are analyzed as examples.
Limits on the optical magnitude of PSR 1821-24 in M28
Authors: Sutaria F. K.
Published: July 2016

The detection of a pulsed X-ray counterpart (RX J1824.2-2R52P) of the 3.05 ms pulsar PSR 1821-24, suggests the possibility of a part of the rotational energy loss of this high spindown rate pulsar being in the optical band. Archival HST data for M28 is used here to set upper limits on the optical V-band magnitude of PSR 1821-24. The optical limit extends the multiwavelength observations for this source and provides a constraint for theoretical models of pulsar emission.
ASCA and RXTE Upper Limits to Pulsed Emissions from PSR B1951+32
Authors: Chang Hsiang-Kuang , Guo Tz-Feng
Published: July 2016

We report upper limits to pulsed X-ray emissions from PSR B1951+32 in 0.5 - 250 keV based on observations of ASCA in 1993 and RXTE in 1996. Together with earlier ROSAT report, these upper limits strongly suggest a thermal pulsed component below about 1 keV. These upper limits also indicate a spectral bending occurring in 100 keV - 3 MeV, which favors an outer-magnetosphere origin for gamma-ray emissions from PSR B1951+32.
Timing and spectral Properties of PSR B1509–58 observed with BeppoSAX
Authors: Cusumano G. , Mineo T. , Nicastro L. , Massaro E. , Massaglia S. , Trussoni E. , Becker W.
Published: July 2016

We present some preliminary results of a BeppoSAX observation of the pulsar PSR B1509–58. We discuss in detail the spectrum energy distribution and show that the high energy data can be explained by a steepening continuum spectrum.
ASCA observations of Galactic rotation-powered pulsars
Authors: Pivovaroff M. J. , Kaspi V. M. , Gotthelf E. V.
Published: July 2016

We have examined several archivalASCAobservations of Galactic radio pulsars, including PSRs B1046–58 and B1610–50. X-ray emission is detected from PSR B1046–58 with a significance of ∼5σ. We find no evidence for pulsations. We argue that the emission is from a spatially unresolved synchrotron nebula powered by the pulsar. The location of the X-ray counterpart within the 95% position error ellipse of the gamma-ray source 3EG J1048–5840 strengthens the claim of Kaspi et al. (2000) that PSR B1046–58 emitϒ-rays. X-ray emission from PSR B1610–50 is not detected. We use the X-ray luminosity upper limit to constrain the pulsar’s velocity ≲ 200km s−1, arguing against an association with the nearby supernova remnant Kes 32. Our results for these radio pulsars contradict previous reports of detections of large (tens of arc minutes) associated synchrotron nebulae.
Applications of Ohm’s Law to the pulsar magnetosphere
Authors: Kunzl Thomas , Lesch Harald , Jessner Axel
Published: July 2016

We show that in the inner magnetosphere of a pulsar mildly relativistic particles can flow out steadily under two assumptions: i) all vacuum fields are completely shielded by copious amounts of particles drawn out by thermal and field emission (which is likely as shown in Jessneret al, 1999) ii) particles emitted from the neutron star surface have weakly relativistic energies (βϒ≈ 1). The results are consistent with the typical particle energies predicted in the radio emission model by Kunzlet al., 1999.
Generation of pulsar radio emission
Authors: Lyubarskii Yu.E.
Published: July 2016

The generation of radio emission from plasma waves excited by two-stream instability in pulsar magnetospheres is considered. Induced scattering transforms the excited longitudinal waves into waves that escape freely in the form of transverse electromagnetic waves. It is shown that the spectrum and the luminosity of the generated radio emission are compatible with those observed.
Formation of beam-plasma structures in pulsar magnetosphere
Authors: Mel’nik V.N.
Published: July 2016

Formation of beam-plasma structure, a new non-linear object, in pulsar magnetosphere is considered.