bluuebunny/crossref_metadata_2025_split huggingface dataset:
A Study of the Orbital and Intrinsic Variability of the Double-Lined Spectroscopic Binary β Centauri
Authors: Ausseloos M. , Aerts C. , Uytterhoeven K. 
Published: July 2016

AbstractWe introduce our observational study of the orbital motion of β Cen. Using 463 high signal-to-noise, high-resolution spectra obtained over a timespan of 12 years it is shown that the radial velocity of β Cen varies with an orbital period of 357.0 days. We derive for the first time the orbital parameters of β Cen and find a very eccentric orbit (e = 0.81) and similar component masses with a mass ratio M1/M2 = 1.02. Both the primary and the secondary exhibit periodic line-profile variations.
Asteroseismology and Forced Oscillations of the Simultaneous p-Mode and g-Mode Pulsator HD 209295
Authors: Handler G. , Balona L.A. , Shobbrook R.R. , Koen C. , Bruch A. , Romero-Colmenero E. , Pamyatnykh A.A. , Willems B. , Eyer L. , James D.J. , Maas T. , Crause L.A. 
Published: July 2016

AbstractWe report the discovery of both intermediate-order gravity mode and low-order pressure mode pulsation in the same star, HD 209295. It is therefore both a γ Doradus and a δ Scuti star, which makes it the first confirmed member of two classes of pulsating star.This object is located in a close binary system with an unknown, but likely degenerate companion in an eccentric orbit, and some of the γ Doradus pulsation frequencies are exact integer multiples of the orbital frequency. We suggest that these pulsations are tidally excited. HD 209295 may be the progenitor of an intermediate-mass X-Ray binary.
Rapid Light Variations of the Bright Be Star ϕ Per
Authors: Sudar D. , Ruždjak D. 
Published: July 2016

AbstractAn analysis of the UBV photometric measurements obtained at Hvar Observatory and Hp HIPPARCOS photometry has been performed in order to disclose the suspected rapid periodic variations of the Be star ϕ Per. The reliability of the derived 0.5 day period is examined and the difficulties of detecting the period due to the complex character of the light variations on the longer time-scales are outlined. Possible explanations of these rapid variations are briefly discussed.
Multi-Site Observations of the Delta Scuti Stars V624 Tauri and HD 23194
Authors: Machado L. Fox , Álvarez M. , Michel E. , Li Z.P. , Pérez Hernández F. , Chevreton M. , Belmonte J.A. , Alonso R. , Barban C. , Dolez N. , Fernandez A. , Guo J.P. , Haywood M. , Liu Y.Y. , Pau S. , Planas H. , Servan B. , Suárez J.-C. 
Published: July 2016

AbstractSome results of the photometry multi-site observations of two δ Scuti stars, V624 Tau and HD 23194, are presented. The observations were carried out in the framework of a STEPHI network in 1999. We collected 343 hours of useful data and detected seven frequencies in V624 Tau and two frequencies in HD 23194.
A Photometric Study of the δ Scuti Star UV Trianguli
Authors: Liu Z.L. , Zhou A.Y. , Rodríguez E. 
Published: July 2016

AbstractUV Tri was observed photometrically from 1999 to 2000. A period analysis of the data reveals two pulsation frequencies at 9.3299 and 10.8483 c d-1. From uvbyHβ data we derive V = 11.085, b – y = 0.215, m1 = 0.169, c1 = 0.783, and β = 2.775 mag. With these color indices and some calibrations, we obtain Mv = 2.44 mag, Mbol = 2.27 mag, Teff = 7500 K, log L/L⊙ = 0.99 and a distance of ∼536 pc.
Time Resolved Spectroscopy of the Pulsating sdB Star PG 1605+072
Authors: O’Toole S.J. , Bedding T.R. , Kjeldsen H. , Dall T. , Stello D. 
Published: July 2016

AbstractWe present analysis of rapid spectroscopy of PG 1605+072, a pulsating sdB star that is believed to have evolved off the extreme horizontal branch. Using a cross-correlation technique on five Balmer lines (Hβ to H8), we have been able to study the Doppler variations in this star over one year. Preliminary results for about 25% of the time-series were presented by O’Toole et al. (2000). We find evidence for amplitude variation between 1999 and 2000. We have also examined of equivalent widths of the Balmer lines looking for variation. Preliminary results are intriguing, with the amplitude of the equivalent width oscillations strongly dependent on wavelength.
Nonradial Pulsations of the DA Type White Dwarf Star G 255-2
Authors: Fu J.-N. , Vauclair G. , Dolez N. , Jiang S.-Y. , Chevreton M. 
Published: July 2016

AbstractPhotometric data obtained on the DA type white dwarf star G255-2 between 1991 and 1997 were reduced and the pulsation spectrum was explored with the standard process. The further analysis provides 10 normal, probably l = 1, independent nonradial eigenmodes.
Effects of a New Equation of State on Cepheid Pulsation Models
Authors: Petroni S. , Castellani V. , Bono G. , Marconi M. 
Published: July 2016

AbstractWe present the results of several numerical experiments aimed at testing the dependence of theoretical observables predicted by Cepheid hydrodynamical models on the equation of state (EOS). We focus our attention on nonlinear and time-dependent Cepheid convective models at solar chemical composition. We find that current predictions for both the blue and red edge of the instability strip present a mild dependence on the EOS. The same outcome applies to the morphology of the lightcurves.
Stochastic Excitation in Solar-Type Stars
Authors: Houdek G. 
Published: July 2016

AbstractThe most convincing evidence to date of solar-type oscillations in other stars comes from recent observations of β Hydri (Bedding et al., 2001) and α Cen A (Bouchy & Carrier, 2001). It is the current belief that the convection dynamics in the outer layers of sun-like stars is the source for driving the intrinsically stable modes to the observed amplitudes. Comparing such observations with theoretical models will help us improve our understanding of the interaction between convection and pulsation.In this contribution I review the mechanisms responsible for mode damping in stars with convective envelopes, and the basic mechanism of stochastic driving by turbulent convection. The application of a stochastic excitation formalism to the Sun is discussed and compared with recent measurements and numerical simulations. Amplitude predictions for models of Procyon, α Cen A and β Hydri are compared with observations.
A Proposed Pulsation Driving Mechanism for γ Doradus Variable Stars
Authors: Guzik J.A. , Kaye A.B. , Bradley P.A. , Cox A.N. , Neuforge-Verheecke C. , Warner P.B. 
Published: July 2016

AbstractWe propose a pulsation driving mechanism for γ Doradus variable stars. This mechanism requires that the local convective timescale at the base of the envelope convection zone be comparable to or longer than the pulsation period. This mechanism explains both the red and blue edges of the γ Dor instability strip. We predict that some candidate γ Dor stars summarized by Handler (1999) may actually be too hot or too cool to be γ Dor variables.
Stellar Parameters of the Post-AGB Star HD 56126
Authors: Le Coroller H. , Gillet D. , Fokin A.B. , Lèbre A. 
Published: July 2016

AbstractWe discuss the stellar parameters (M, L, Teff) of a post-AGB star, HD 56126, deduced from observations and non-linear radiative pulsation models. We show that pure radiative pulsation models are in contrast with stellar evolution.
Gravitational-Wave Asteroseismology as a Tool to Reveal the Equation of State of Relativistic Neutron Stars
Authors: Ruoff Johannes 
Published: July 2016

AbstractThe equation of state (EOS) is still the big unknown in the physics of neutron stars. An accurate measurement of both the mass and the radius of a neutron star would put severe constraints on the range of possible EOSs. I discuss how the parameters of the oscillation modes of a neutron star, measured from the emitted gravitational waves, can in principle be used to infer its mass and radius, and thus reveal its EOS.
The MONS Sky
Authors: Pijpers F.P. , Teixeira T.C. 
Published: July 2016

AbstractThe MONS project on the Rømer satellite aims at studying properties of stellar interiors through observations of oscillations in stellar luminosity and surface temperature. The main targets are stars exhibiting oscillations similar to those observed in the Sun, with very low amplitudes. During the planned two-year lifetime of the mission, around 20 such stars will be observed with the MONS Main Telescope. Additional data on variability of a large number of stars of a broad range of types may be obtained from the Star Trackers. In order to assist in planning of both ground-based science as well as mission science itself, various tools and databases have been or are being developed. These tools are/will be accessible through the MONS Information System (MIS) which can be queried through a WWW interface. One such tool is a clickable map of the full sky with on it the various fields around the designated main targets of MONS. A click on a field leads to information on the stars within those fields which can be of interest for asteroseismic studies.
Outside the Stars
Authors: Longair Malcolm S. 
Published: July 2016

It is a great pleasure and privilege to give the opening lecture at this IAU Colloquium “Inside the Stars”. It is particularly appropriate that it is held in Austria, the country of Ludwig Boltzmann whose name will appear explicitly or implicitly in every lecture.My task is to describe the astrophysical and cosmological setting within which our discussions will take place. I emphasise that I am an outsider at this colloquium in all possible senses. My own research interests are in the areas of high energy astrophysics, extragalactic research and astrophysical cosmology. In lecturing to my students, however, I emphasise that the subject of the present colloquium is at the very heart of virtually all astrophysics and these studies are quite essential in order to make sense of galaxies and extragalactic systems. If we did not have this confidence in our ability to understand the stars, at least in principle, we would worry about the reliability of the enormous astrophysical edifice which has been built up to explain the large scale features of our Universe. I also emphasise to my students that the study of the stars is among the most exact of the astrophysical sciences — in my enthusiastic moments, I claim that, in the very best of these studies, astrophysics approaches the precision of laboratory experiment. I hope to find many examples this week to reinforce this belief.From my perspective, what I need is a User’s Guide to Stars and Stellar Evolution, in other words, a reliable set of rules about the origin and evolution of stars in order to diagnose the physical properties of the systems I am trying to understand. I will illustrate the types of information we need by discussing three case studies in the areas of (i) high energy astrophysics, (ii) classical cosmology and (iii) astrophysical cosmology and the origin of galaxies. Necessarily, these studies will be far from complete, but I hope they will illustrate some of the issues which come up in these disciplines. In the course of the discussion, it will become apparent that I will touch upon essentially all branches of contemporary astrophysics. I will take very different approaches to the three case studies.
Steady and Fluctuating Parts of Sun’s Internal Magnetic Field
Authors: Gokhale M.H. , Hiremath K.M. 
Published: July 2016

AbstractWe have modeled the ‘steady’ part of sun’s internal poloidal magnetic field in the form of a central dipole and a central hexapole with strengths (0.6±0.1)andembedded in an asymptotically uniform field Bo. A small deviation from isorotation seems to indicate:(i) a slow build-up of toroidal field near the base of the convection zone and (ii) presence of torsional MHD perturbations in the outer radiative core, with latitudinal structure and time scales which may be similar to those of solar activity.
Activity Cycle in the Solar Core
Authors: Grandpierre Attila 
Published: July 2016

AbstractI analyze here the recent solar seismology data relevant to the core regarding the energetics. The result is that the magnetic torsional oscillations are hardly able to support the observed rate of change of the solar core rotation. Interpreting the solar neutrino data as directly coming from the core and showing the activity cycle of the core, the energetics of the core can be balanced. I show here a simple model for the global and local activity-related changes of the solar core. The parameters of this model are consistent with the values derived by the Convective Flare Theory. This model is able to interpret the anticorrelation of the sunspot number with the neutrino flux, the related changes in the rotation of the core and the first which interprets the observed activity-related element abundance anomalies with a model for the solar core.
Asymmetry and Periodicities in Solar Activity
Authors: Carbonell M. , Oliver R. , Ballester J.L. 
Published: July 2016

AbstractThe historical record of daily sunspot areas (1874 - 1989) has been analysed, looking for the short (155 days) and intermediate (323 and 540 days) term periodicities. Also the North - South asymmetry during those years has been studied.
Observational Patterns of Lithium Depletion in Pre-Main Sequence Stars
Authors: Martin Eduardo L. , Rebolo Rafael , Lopez Ramon J. Garcia , Magazzu Antonio , Pavlenko Yakov V. 
Published: July 2016

AbstractWe present results based on the analysis of lithium abundances in a sample of ~ 50 pre-main sequence stars covering a wide range of masses (from 2 to 0.3 M⊙) and luminosities (corresponding to ages of 1-100 Myr). Stars with masses estimated to be ≳ 1 M⊙show lithium abundances close to cosmic with little scatter (± 0.3 dex). Stars with masses less than Solar present a wide range of lithium abundances, with a clear trend to lower abundances for lower luminosities (greater age). The observed Li abundances constrain theoretical predictions of lithium depletion in rotating pre-main sequence stars.
The Importance of Molecular Opacities in Stellar Atmospheres
Authors: Sharp Christoper M. 
Published: July 2016

Opacities are of vital importance in astrophysics necessary to model stellar atmospheres and interiors, and below about 6000 K diatomic molecules make an increasing contribution to that opacity. Moreover, at around 3000 K polyatomic molecules, such asH2Ofor an oxygen rich solar composition, start playing an important rôle, and additionally at high pressures collision inducedH2–H2andH2–Heabsorption is important for late-type main sequence stars.In order to investigate the importance of molecular opacities, in Sharp (1992) we computed and compared opacities for a solar and a three times enhancedCNOabundance, and some further comparisons were made in Sharp et al. (1992). Some of these results are briefly summarised here.
Measurements of Masses and Radii of Eclipsing Binaries
Authors: Ferluga S. , Floreano L. , Mangiacapra D. 
Published: July 2016

AbstractWe report the detection of 10 new double–line eclipsing binary systems, with first measurements of masses and radii. These results are the preliminary outcome of an observational campaign for detecting new double–line eclipsing systems, carried out at the Observatoire de Haute Provence (OHP) in France, with the 1.52-m telescope and its CCD high–resolution spectrograph Aurelie.
Mode Selection and Other Nonlinear Phenomena in Stellar Oscillations
Authors: Dziembowski W.A. 
Published: July 2016

AbstractNonlinear effects determining the amplitudes of unstable modes of oscillations in stellar modes, are reviewed. The two basic processes - saturation of the driving mechanism and resonant mode coupling - are discussed within the framework of the amplitude equation formalism. There are difficult problems in the theory of multiple mode interaction that must be solved to make a prediction of amplitude spectra possible. The observed spectra for δ Scu stars and other multiperiodic variables, exhibit no simple pattern that would suggest a solution of the theoretical problems.
Solar-Like Oscillations on α Centauri A
Authors: Pottasch Edward M. , Butcher Harvey R. , Van Hoesel Frans H.J. 
Published: July 2016

AbstractDetection of individual modes of oscillation near 5 minutes period is proposed, based on the comb-like signature which is similar to that found in the sun. The mean peak amplitudes (ap) of the strongest individual modes are 75 ≤ ap ≤ 120 cm/s, and the mean separation between alternate modes is 55.3 ± 3.6 μHz. Apparent modal lifetimes are on the order of 2 days, but we suggest this may be caused by interference of adjacent modes.
New Limits on the Instability Strip of the HRD: Observations from a Northern Sky Survey of Ap Stars for Rapid Variability
Authors: Nelson Matthew J. , Kreidl Tobias J. 
Published: July 2016

AbstractThe search for pulsational variables that occupy the hotter realms of the instability strip in the Hertzsprung-Russel diagram (HRD) have been traditionally restricted to the regions where models indicated that pulsation is tractable. Recent surveys of stars have revealed, however, that stars that were thought not to lie in the instability strip do indeed pulsate. This raises questions about the extent of the instability strip.While this has implications for all hot pulsating stars, we use here primarily our survey results of Ap stars to compare with the models. We report results here from a high-speed photometric survey of 120 Ap stars that was conducted between 1985 and 1991 to search for rapid variability. The absence of pulsations in the hotter Ap stars (roughly B8-A3) is noted and deemed significant on the basis of the number of stars observed in this temperature range, as well as the overall quality of the data. This, however, does not preclude their existence, especially since HD 218495 was recently discovered to be a rapidly oscillating Ap (roAp) star (Martinez, Kurtz and Kaufmann 1991), and has a spectral type of about A3.Color-magnitude diagrams of the survey stars are presented, with the known roAp stars included for reference. The diagrams are presented in the Strömgren and Geneva systems. The color-magnitude diagrams demonstrate the completeness of the survey in covering Ap stars at a wide range of temperatures. We find no obvious means of using color indices to differentiate roAp stars from non-pulsating Ap stars.
A Compact SIS Receiver Cooled By 4 K GM Refrigerator
Authors: Kuriyama Toru , Hatakeyama Hideo , Takahashi Masahiko , Nakagome Hideki , Kawabe Ryohei , Iwashita Hiroyuki , McCulloch Gerrard , Shibata Katsunori , Ukita Nobuharu 
Published: July 2016

SIS receivers have higher sensitivity than Schottky diode receivers. The SIS mixer, however, must be cooled at 4 K level, and either a GM (Gifford-McMahon) + JT (Joule- Thomson) refrigerator or liquid helium is used. Therefore, SIS receivers are usually much larger and heavier than Schottky diode receivers which are usually cooled by a GM refrigerator only.Kuriyama et al. developed a GM refrigerator using Er3Ni as a regenerator material which achieved to cool at 4 K level.In this work, the SIS receiver was constructed and investigated, which was cooled below 4 K by the GM refrigerator with Er3Ni. It resulted in the SIS receiver which was about the same size and weight as a usual Schottky diode receiver.
High Resolution Observations of CO in Planetary Nebulae
Authors: Shibata K.M. , Deguchi S. , Kasuga T. , Tamura S. , Hirano N. , Kameya O. 
Published: July 2016

AbstractIn order to examine the structure and kinematics of the molecular gas around planetary nebulae, we have made aperture synthesis observations of I2CO(J=1-0) emission in three planetary nebulae, IRAS 21282+5050, CRL 618 and M 1-7, using Nobeyama Millimeter Array.
Molecular Cloud Core and CS Outflow Associated with Haro 4-255 FIR
Authors: Tatematsu K. , Umemoto T. , Murata Y. , Chen H. , Hirano N. , Takaba H. 
Published: July 2016

AbstractThe region containing Haro 4-255 FIR is studied in CS (1-0) with the 45 m telescope and the Nobeyama Millimeter Array. We have detected intense CS outflow. The CS abundance is found to be enhanced in the outflow lobe. The aperture synthesis data show two groups of emission, one of which is likely to impede the blueshifted CS lobe.
Interferometric Observations for O-Containing Organic Molecules Towards Orion-KL
Authors: Minh Y. C. , Ohishi M. , Roh D. G. , Ishiguro M. 
Published: July 2016

AbstractHigh spatial resolution observation (~ 5 arcsec) were made for CH3OH, HCOOCH3, and (CH3)2O toward Orion-KL using the Nobeyama Millimeter Array. The spatial distribution of CH3OH appears to be well elongated along the line connecting IRc2 and “the southern condensation (SC)”. The HCOOCH3 and (CH3)2O emissions appear to be well concentrated to SC with an angular size of ~ 6.5 arcsec. We derive the total column densities 6.8 × 1017cm−2, 1.4 × 1016cm−2 and 2.7 × 1016cm−2 for CH3OH, HCOOCH3, and (CH3)2O, respectively, at the core of SC.
SiO in Star Forming Regions: Barnard 1 and Orion KL
Authors: Yamamoto Satoshi , Mikami Hitomi , Saito Shuji 
Published: July 2016

AbstractInterferometric observations of the SiO (J = 2 − 1) line are carried out toward a low-mass-star forming region, Bl, and a massive star forming region, Ori KL. Production mechanisms of SiO in these regions are discussed.
The Large Millimeter Array
Authors: Ishiguro M. , Kawabe R. , Nakai N. , Morita K.-I. , Okumura S. K. , Ohashi N. 
Published: July 2016

AbstractIn Japan, there is a plan for Large Millimeter Array proposed by Nobeyama Radio Observatory. The proposed array may consist of 50 10-m antennas distributed in a 2 − 3 km area at very high altitude. In this paper, scientific directions, planned system, and site survey for the LMA are reported.
Millimeter and Submm-Interferometry on MT. Graham, Arizona
Authors: Bieging J.H. , Martin R.N. , Walker C. , Angel J.R.P. , Hill J.M. , Woolf N.J. , Baars J.W.M. 
Published: July 2016

AbstractThis paper draws attention to the potential for use of telescopes now under construction or planned for the near future as part of the Mt. Graham International Observatory, located in the Pinaleño Mts. east of Tucson, Arizona, for interferometer observations at mm-and submm-wavelengths. The Submillimeter Telescope (SMT) should be completed by early 1993. A collaboration between the Max-Planck-Institut für Radioastronomie and Steward Observatory, the SMT is a high-precision 10-m diameter telescope which will be useful for short-wavelength VLBI observations. A large optical telescope, consisting of two 8.4-m diameter mirrors on a common mount, is in the early design stages. When completed, it will provide for short-baseline (approx. 20-m) interferometry between the two optical mirrors, as well as interferometry with the SMT over baselines of a few hundred meters.
Abundance Correlations in Mercury-Manganese Stars
Authors: Smith K.C. , Dworetsky M.M. 
Published: July 2016

AbstractElemental abundances from recent spectrum-synthesis analyses of the ultraviolet spectra of normal and HgMn-type late-B stars are examined for inter-correlations and for correlations with stellar parameters by use of standard statistical techniques. A few marginally significant correlations are apparent in the normal-star sample. In the HgMn sample, significant correlations with Teff are identified for Mn, Cu, and Ga. Strong inter-correlations are also identified in this sample for the abundances of two triads of elements (Mg-Al-Cr and Mn-Cu-Ga). Trivariate correlation analysis is used to demonstrate that these element-element inter-correlations are statistically independent of both Teff and log g. The correlated behaviour of these characteristically anomalous elements casts new light on the apparent heterogeneity of the HgMn class of peculiar stars, and may have important implications for the diffusion model which has been advocated as an explanation of the HgMn phenomenon.