bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Variable Stars in NGC 6229
Authors: Borissova J. , Valchev T. , Catelan M. , Ferraro F. R. , Sweigart A. V. 
Published: June 2019

AbstractWe present results of a variability survey in the outer-halo globular cluster NGC 6229. Our main goal is to shed light on the origin of the bimodal horizontal branch (HB) of this cluster.
Theoretical UBVI Light Curves of Pulsating Stars
Authors: Feuchtinger Michael U. , Dorfi Ernst A. 
Published: June 2019

AbstractBy performing detailed frequency-dependent radiative transfer computations we are able to calculate light curves in particular bandpasses from stellar pulsation models calculated by the Vienna nonlinear convective pulsation code. As a sample application we discuss UBVI light curves of RR Lyrae stars. The properties of these light curves are analyzed by means of standard Fourier decomposition, and a comparison to recent observations is performed. As main results we find a good agreement with important observed RR Lyrae properties like pulsation amplitudes and Fourier parameters in B, V, and I bands. Additionally, from the synthetic color curves we derive linear transformation laws between amplitudes as well as Fourier parameters in the different bandpasses.
Oscillations of Rapidly Rotating Stars
Authors: Dintrans B. , Rieutord M. 
Published: June 2019

AbstractWe present numerical simulations of gravito-inertial waves propagating in radiative zones of rapidly rotating stars. A first model, using the Boussinesq approximation, allows us to study the oscillations of a quasi-incompressible stratified fluid embedded in a rapidly rotating sphere or spherical shell. In a second step, we investigate the case of a γ Doradus-type star using the anelastic approximation. Some fascinating features of rapidly rotating fluids, such as wave attractors, appear in both cases.
Upgrading the MHD Equation of State to Include Relativistic Electrons
Authors: Gong Zhigang , Däppen Werner 
Published: June 2019

AbstractSo far, the effect of relativistic electrons has not been included in the Mihalas-Däppen-Hummer (Hummer & Mihalas 1988; Mihalas, Däppen, & Hummer 1988; Däppen et al. 1988; hereinafter MHD) equation of state, although degeneracy was taken into account. Following the findings about the detectability of the relativistic effect in helioseismological data of the solar center (Elliot & Kosovichev 1998; hereinafter EK98), we have upgraded the MHD equation of state to include relativistic degenerate electrons. Our numerical calculation confirms the result of EK98.
A List of Stars in the β Cephei and SPB Instability Strips
Authors: Blay P. , Fabregat J. 
Published: June 2019

For the purpose of observing β Cephei and SPB stars with optical telescopes on board future space missions, we have developed an automatic photometric search of stars falling inside the β Cephei and SPB instability strips. A list has been compiled which is available upon request from the authors (blay@castor.daa.uv.es;juan@pleione.daa.uv.es).The boundaries of the instability strips have been defined by observational β – c0 HR diagrams based on Stræmgren photometry (Sterken & Jerzykiewicz 1993 = SK93). The ZAMS has been set as the lower limit of both strips. Low and high temperature limits are set as those given by SK93 and the upper limit is fixed by the photometry β of Cep stars found in the literature. For the SPB stars we have followed the same procedure. We have found the following boundaries: β Cephei: 0.2295c0 + 2.6263 > β > 0.0394c0 + 2.5656; 0.17 > c0 > –0.1; SPB: 2.630 > β > 0.2642co + 2.6207; 0.8 > c0 > 0.17.
Periods of β Cephei and SPB Stars from Hipparcos Photometry
Authors: Molenda-Żakowicz J. 
Published: June 2019

AbstractFor the β Cephei variables, we compare the periods derived from ground-based observations with those given in the Hipparcos catalogue. For the SPB stars, of which most have been discovered by Hipparcos, we examine the question of multiperiodicity.
The Radial Velocity Projection Factor in the Pulsating Helium Star V652 Her
Authors: Rodriguez P. Montañés , Jeffery C. S. , Cuadrado R. Aznar , Pollacco D. 
Published: June 2019

AbstractThe behavior of the velocity projection factor was studied for three individual Lines, He ɪ 4438 Å, Si ɪɪɪ 4553 Å, and N ɪɪ 4442 Å, and for the complete spectrum in the radially pulsating helium rich star V652 Her. It is shown that the projection factor is itself a function of expansion velocity.
Driving g-mode Pulsations inγDoradus Variables
Authors: Guzik J. A. , Kaye A. B. , Bradley P. A. , Cox A. N. , Neuforge C. 
Published: June 2019

AbstractWe suggest that the modulation of radiative flux by convection at the base of a deep envelope convection zone during the pulsation cycle is responsible for driving high-order g modes with periods 0.4 to 3 d observed inγDoradus variables.
g Modes in F Stars – A Non-adiabatic Investigation of the Stability of g Modes in ϒ Doradus Stars
Authors: Löffler Wolfgang 
Published: June 2019

AbstractWe investigate a sequence of 1.5 M⊙ models for g-mode instabilities. For the computation of the nonradial, non-adiabatic oscillations we make use of the Riccati method introduced by Glatzel & Gautschy (1992) to integrate the pulsation equations as given by Unno et al. (1989).
Excitation Mechanism in roAp Stars
Authors: Balmforth N. J. , Cunha M. S. , Dolez N. , Gough D. O. , Vauclair S. 
Published: June 2019

AbstractIn the present work we develop a theoretical model for roAp stars characterized by the suppression of convection around the magnetic poles. When calculating the growth rates of acoustic oscillations in models of this type we find that most models whose positions in the HR diagram coincide with that of the observed roAp stars are unstable against high-order pulsations.
Solar-Like Oscillations of Procyon A: Stellar Models and Time Series Simulations versus Observations
Authors: Barban C. , Michel E. , Martic M. , Schmitt J. , Lebrun J. C. , Baglin A. , Bertaux J. L. 
Published: June 2019

AbstractThe aim of this paper (further developed in Barban et al. 1999) is to present new evidence of the possible stellar origin of the observed excess power in the power spectrum of Procyon A presented in Martic et al. (1999) by comparing these observational data with theoretical predictions and numerical simulations.
New Progress in Mode Detection and Identification in δ Scuti Stars by the Analysis of Line Profile Variations
Authors: Mantegazza L. , Poretti E. , Bossi M. , Nuñez N. S. , Sacchi A. , Zerbi F. M. 
Published: June 2019

Abstractδ Sct stars are among the most promising targets to perform ground-based asteroseismology. High resolution spectroscopy offers us a powerful technique to identify radial and nonradial pulsation modes, since we can easily detect oscillations and travelling features in the line profiles.
A Photoelectric Study of the Am δ Scuti Variable 60 Tau
Authors: Zhiping Li , Yanying Liu , Aiying Zhou 
Published: June 2019

AbstractFive nights of photoelectric photometric observations through v and y filters confirm the pulsation of the Am δ Scuti variable 60 Tau. Power spectra of the light curves show multiple periods; two modes f1 = 13.0364 d−1 and f2 = 11.8521 d−1 are definitely identified. The phase differences, ϕv − ϕy, suggest that 60 Tau pulsates in low-degree modes; the pulsation constants, Q, suggest these are low overtone modes; and the frequency ratio implies that at least one mode is nonradial.
Ten Years of STEPHI Multisite Campaigns on δ Scuti Stars
Authors: Michel E. , Chevreton M. , Belmonte J. A. , Li Z. P. , Alvarez M. ,   the STEPHI Team
Published: June 2019

AbstractSTEPHI is a photometry network that aims to obtain data to reach a better understanding of the physics of stellar interiors by seismology of δ Scuti stars. For ten years now STEPHI has been harvesting multisite rapid photometry data of δ Scuti stars on the main sequence. With 12 δ Scuti stars observed during three-week, three-site campaigns, STEPHI has produced a significant amount of the data available on δ Scuti stars for seismological study of this stage of evolution. The STEPHI data have already been basis of several theoretical interpretations (see http://dasgal.obspm.fr/˜stephi). Here we focus on some aspects of our observational strategy and results.
Radial Pulsation of the roAp Star HD 122970?
Authors: Handler G. , Paunzen E. , Garrido R. , Guzik J. A. , Beach T. E. , Medupe R. , Chagnon F. , Shobbrook R. R. , Matthews J. M. , Ryabchikova T. A. , Hatzes A. P. 
Published: June 2019

AbstractWe acquired multisite observations of the newly discovered rapidly oscillating Ap star HD 122970. A frequency analysis shows the presence of two independent modes, one singlet and one equally spaced triplet. By applying the oblique pulsator model and asymptotic theory we infer that the triplet originates from a distorted dipole mode and that the singlet most probably corresponds to a radial mode.
Oscillation Patterns of SX Phœnicis Variables in Globular Clusters
Authors: Petersen J. O. , Quaade M. , Andersen M. I. , Freyhammer L. M. 
Published: June 2019

AbstractBased on new analyses of light curves of SX Phœnicis variables in globular clusters and on results taken from the literature, an overview of oscillation patterns in this subgroup of δ Scuti variables is given. Belonging to the Blue Straggler stars, they are expected to have a more complicated life history than “normal” δ Scuti stars in the field or in open clusters. The overall picture is that the patterns found in this SX Phe group seem to be similar to the patterns that are well established for standard field δ Set stars.
Excitation of Gravity-Mode Pulsations in DA & DB White Dwarfs
Authors: Wu Yanqin 
Published: June 2019

AbstractOscillations in white dwarfs of hydrogen or helium envelopes are believed to be excited close to the surface, where convective energy transport dominates the stellar luminosity. The convective motion in these stars is fast and can respond instantaneously to the pulsation state. In this limit, we find the convective envelope to be the seat of mode excitation because it acts as an insulating blanket with respect to the perturbed flux that enters it from below. This retaining of the flux leads to driving. Driving exceeds radiative damping providedωτc≥ 1, whereωis the radian frequency of the mode andτc≈ 4τthwith τthbeing the thermal time constant evaluated at the base of the convective envelope. We follow Brickhill (1991) in naming this mechanism as ‘convective driving’. We also studied the dynamical interaction between turbulent convection and pulsation. In the limit of fast convection, turbulent damping inside the convective region is negligible, while that coming from the overshoot region is more significant. I discuss the application of ‘convective driving’ in other types of pulsating stars.
The Potential for Astronomy in the Infrared
Authors: Storey John W. V. 
Published: June 2019

AbstractInfrared Interferometry promises to be a useful astrometric technique. Preliminary measurements of the star α Orionis made with a heterodyne interferometer exhibit phase coherence over a period of at least 1000 seconds. The measurements were equivalent to a positional determination of 60 second accuracy every 5 seconds of integration.
Observations of High-Density Corrections to VUV Line-Wing Shapes in a Plasma with a Few Particles Per Debye Sphere
Authors: Baker E.A.M. , Burgess D.D. 
Published: June 2019

Observations of high density effects on spectral line shapes are reported for neutral, singly- and doubly-ionized emitters in a dense plasma with a small number of particles per Debye sphere. The source used in these experiments was a well-diagnosed linear pinch,run in argon, producing a plasma with electron density between 0.5 x 1018 and 3 x 1018 cm–3, and temperature between 22,000 K and 27,000 K.Satellite-like features observed in the wings of H I Lyman α are attributed to the influence of unbound quasimolecular states. A number of the satellites are apparently due to states of H–Ar+ (similar to two such Lyman α satellites observed by Preston 1977). However, it seems likely that at least one of the satellite features observed should be attributed to the influence of Ar++ perturbers. Such quasimolecular features might be expected to become increasingly important at higher densities, and for more highly-ionized perturbing ions.
Bandwidth Requirements in Spectral Line Transfer Calculations
Authors: Athay R. Grant 
Published: June 2019

AbstractAccurate evaluation of a line source function, S, requires that the frequency bandwidth be sufficiently large to include properly transfer effects in the line wings. The bandwidth required to achieve a given level of accuracy in the evaluation of S can be specified, in units of the Doppler width, in terms of three parameters: the ratio of continuum to line opacity, ro, the probability for collisional deexcitation, ε, and the Voigt wing parameter . Bandwidths required to give S to an accuracy of 2 percent are given for values of ε and ro from 10-2 to 10-8 and for values of from 10-2 to 10-5.
What Do We Know Through Spectral Information on Stellar Chromospheres and Coronas?
Authors: Praderie Françoise 
Published: June 2019

AbstractFour problems in interpreting spectra to infer chromospheres-coronas are summarized. (1) The a priori difficulties in interpreting spectra lie in uncertainty on the range of possible models, coming from uncertainty as to which conservation equations may be applied, and from lack of an exhaustive list of spectral indicators that may be used for uniqueness tests. (2) As spectral indicators we consider: emission lines, self-reversed emission cores, the presence of He I lines in stars not of early type, coronal-type high ionization, excess continuum emission in the rocket UV and the far infrared. (3) To determine what we can infer from observations, we summarize information: inferred by comparison of models to data, on velocity fields, and on spectral variability which might suggest chromospheric activity. (4) We summarize the evidence for chromospheres in A stars, as being those where convection-induced acoustic heating is marginal.
An X-Ray View of Interacting Binaries Outside The Galaxy
Authors: Prestwich Andrea H. 
Published: June 2019

AbstractChandra and XMM-Newton are revolutionizing our understanding of compact binaries in external galaxies, allowing us to study sources in detail in Local Group Galaxies and study populations in more distant systems. In M31 the X-ray luminosity function depends on the local stellar population in the sense that areas with active star formation have more high luminosity sources, and a higher overall source density (Kong. Di Stefano. Garcia, & Greiner 2003). This result is also true in galaxies outside the Local Group; starburst galaxies have flatter X-ray luminosity functions than do spiral galaxies which are in turn flatter than elliptical galaxies. These observational results suggest that the high end of the luminosity function in star forming regions is dominated by short-lived high mass X-ray binaries.In Chandra Cycle 2 we started a Large Project to survey a sample of 11 nearby (< 10Mpc) face-on spiral galaxies. We find that sources can be approximately classified on the basis of their X-ray color into low mass X-ray binaries, high mass X-ray binaries and supersoft sources. There is an especially interesting class of source that has X-ray colors softer (“redder”) than a typical low mass X-ray binary source, but not so extreme as supersoft sources. Most of these are probably X-ray bright supernova remnants, but some may be a new type of black hole accretor. Finally, when we construct a luminosity function of sources selecting only sources with low mass X-ray binary colors (removing soft sources) we find that there is a dip or break probably associated with the Eddington luminosity for a neutron star.
Bowen Fluorescence from Companion Stars in X-Ray Binaries
Authors: Casares J. , Steeghs D. , Hynes R. I. , Charles P. A. , Cornelisse R. , O'Brien K. 
Published: June 2019

AbstractThis paper will review a new technique of detecting companion stars in LMXBs and X-ray transients in outburst using the Bowen fluorescence NIII lines at 4634-4640. These lines are very efficiently reprocessed in the atmospheres of the companion stars and, thereby, provide estimates of the K2 velocities and mass functions. The method has been applied to Sco X-1, X1822-371 and GX339-4 which, in the latter case, provides dynamical evidence for the presence of an accreting black hole. Preliminary results from a VLT campaign on V801 Ara, V926 Sco and XTE J1814-338 are also presented.
A ULX in NGC 4559: A “Mini-Cartwheel” Scenario?
Authors: Soria R. , Cropper M. S. , Pakull M. W. 
Published: June 2019

AbstractWe have studied the peculiar environment around a ULX in NGC 4559 (with Lx ≈ 2 x 1040 erg s–1 and MBH ≳ 50M⊙). The X-ray source is located near the rim of a young (age < 30 Myr), large (diameter ≈ 700 pc) ring-like star forming complex possibly triggered by the impact of a dwarf satellite galaxy through the gas-rich outer disk of NGC 4559. We speculate that galaxy interactions (including the infall of high-velocity clouds and satellites on a galactic disk) and low-metallicity environments offer favourable conditions for the formation of compact remnants more massive than “standard” X-ray binaries, and accreting from a massive Roche-lobe filling companion.
Simultaneous Integral/RXTE Observations of GRS 1915+105
Authors: Rodriguez J. , Hannikainen D. , Vilhu O. , Fuchs Y. , Shaw S. E. 
Published: June 2019

AbstractWe present the first results of simultaneous INTEGRAL and RXTE observations of the microquasar GRS 1915+105. We focus on the analysis of the unique highly variable observation and show that we might have observed a new class of variability. We then study the energetic depenelence of a low frequency QPO from our steady observations.
Using X-Rays to Probe the Compact Binary Content of Globular Clusters
Authors: Webb N. A. , Gendre B. , Barret D. 
Published: June 2019

AbstractGlobular clusters (GCs) harbour a large number of close binaries which are hard to identify optically due to high stellar densities. Observing these GCs in X-rays, in which the compact binaries are bright, diminishes the over-crowding problem. Using the new generation of X-ray observatories, it is possible to identify populations of neutron star low mass X-ray binaries, cataclysmic variables and millisecond pulsars as well as other types of binaries. We present the spectra of a variety of binaries that we have identified in four GCs observed by XMM-Newton. We show that through population studies we can begin to understand the formation of individual classes of binaries in GCs and hence start to unfold the complex evolutionary paths of these systems.
On the Nature of the Binary Components of RX J0806.3+1527
Authors: Reinsch K. , Burwitz V. , Schwarz R. 
Published: June 2019

AbstractWe present imaging circular polarimetry and near-infrared photometry of the suspected ultra-short period while-dwarf binary RX J0806.3+1527 obtained with the ESO VLT and discuss the implications for a possible magnetic nature of the white dwarf accretor and the constraints derived for the nature of the donor star. Our V-filter data, show marginally significant circular polarization with a modulation amplitude of ≈ 0.5% typical for cyclotron emission from an accretion column in a magnetic field of order 10MG and not compatible with a direct-impact accretor model. The optical to near-infrared flux distribution is well described by a single blackbody with temperature kTbb = 35000 K and excludes a main-sequence stellar donor unless the binary is located several scale heights above the galactic disk population.
Mass-Capture Rate by the Neutron Star in Be/X-Ray Binaries
Authors: Okazaki A. T. , Hayasaki K. 
Published: June 2019

AbstractWe study the interaction between the Be-star disk and the neutron star in Be/X-ray binaries by three dimensional SPH simulations. We find that, the resonant, truncation of the Be disk works except for systems with extremely high orbital eccentricity or large misalignment angles between the Be disk and the orbital plane. Owing to the truncation, the mass-capture rate by the neutron star is sensitive both to the orbital eccentricity and to the angle of misalignment. It is single-peaked in coplanar systems and in systems with small misalignment angles, whereas it, becomes double-peaked in systems with large misalignment angles.
Physical Interpretation of Dwarf Nova Primary Effective Temperatures
Authors: Townsley Dean M. , Bildsten Lars 
Published: June 2019

AbstractWe have undertaken a theoretical study of the impact of the accumulating envelopes on the thermal state of the underlying white dwarf (WD). This has allowed us to find the equilibrium WD core temperatures, the classical nova ignition masses and the thermal luminosities for WDs accreting at rates of 10–11 – 10–8M⊙ yr–1. These accretion rates are most, appropriate to WDs in cataclysmic variables (CVs) of (Porb ≲ 7 hr), many of which accrete sporadically as Dwarf Novae. Over twenty Dwarf Novae have been observed in quiescence, when the accretion rate is low and the WD photosphere is detected and Teff measured. Comparing our theoretical work to these observations allows us to constrain the WD mass and the time averaged accretion rate, ⟨Ṁ⟩. If ⟨Ṁ⟩ is that given by gravitational radiation losses alone, then the WD masses are > 0.8 M⊙. An alternative conclusion is that the masses are closer to 0.6M⊙ and ⟨Ṁ⟩ is 3-4 times larger than that expected from gravitational radiation losses.
Chemical Abundances of the Secondary Stars in the Black Hole Binary A0620-00 and the Neutron Star Binary Cen X-4
Authors: González-Hernández J. I. , Rebolo R. , Israelian G. , Casares J. 
Published: June 2019

We have determined abundances in the secondary stars of the black hole X-ray binary A0620-00 and the neutron star Binary Cen X-4. These are K type stars veiled by the emission produced by the respective accretion discs. We searched for evidence of nucleosynthetic products from the progenitor of the compact object that could have contaminated the secondary stars (as in Israelian et al., 1999).Using high resolution spectra obtained with VLT/UVES, we have derived in a consistent way stellar parameters and the veiling caused by the accretion disc.
The effect of the compositional quality of milk on new product development
Authors: Tow G. J. 
Published: June 2019

In recent years, the average consumer has become much more aware of the composition of food. Medical opinion, that diets high in fibre and low in fat are likely to result in longer and healthier lives, has provided the food industry with new market sectors and, hence, the need for new product development.The dairy industry in the United Kingdom has, in the main, been slow to react to this challenge and has left the remainder of the food industry to manipulate the composition of the final product. At one time, the inclusion of 100 g butter per kg margarine was deemed to be a sales advantage but today the consumer believes it is a disadvantage. The cholesterol and saturated fats discussion has obviously been put forward with great fervour by members of the food industry who have sought to gain advantage. The reaction of the dairy industry has been to take a defensive stand rather than to conduct research and promote the nutritional advantage of milk and milk products. This attitude is changing, fortunately, and new dairy products are being developed and marketed aggressively. The belief of the dairy industry, that only new products containing milk ingredients alone would be manufactured, is no longer true and a whole range of new dairy-based products, incorporating varying amounts of other food ingredients, is appearing.The latest developments in dairy technology are resulting in some new raw materials derived from milk, specially designed for specific uses in the food industry. This paper reviews some of these developments against the background of milk composition, industrial production and market consumption.