bluuebunny/crossref_metadata_2025 huggingface dataset:
Hydrogen Cyanide Polymers as Prebiotic Sources of Biological Compounds in Terrestrial and Extraterrestrial Environments
Authors: Negrón-Mendoza Alicia , Ramos-Bernal Sergio
Published: July 2016

Aqueous solutions of cyanides are frequently used in experiments related to prebiotic chemistry. CNcontaining molecules are key compounds in this type of synthesis. This is due to the high chemical reactivity of the CN group, their abundance in the interstellar space, in comets, and the facility of their formation from simulated experiments. Implications for prebiotic chemistry are profound mainly because these polymeric materials upon hydrolysis release compounds of biological significance such as amino acids, purines, carboxylic acids, etc. Since the products formed from a CN-containing compound have different chemical groups, and a great variety of molecular weights, the potentiality and versatility for prebiotic synthesis is enormous. The gamma irradiation of very diluted aqueous solutions of HCN yields oligomeric material among the radiolytic products. These oligomers are constituted of polyamides and substituted ureas. However, radiation-induced polymers have different characteristics than the polymers formed by thermal polymerization.
Violent Primitive Earth Might have Harmonized with the Origin of Life
Authors: Shimizu Mikio
Published: July 2016

At the end of the planetesimal infall on the surface of the primitive earth, hot dry beaches might have been useful for the formation of various activated monomers and oligomers (peptides and small RNAs). We discuss the possibility that a small system composed of small RNAs (∼ 10 mers) and dipeptides might have mimicked the contemporary biosystem, based on experimental results suggesting the presence of previously overlooked weak but specific interactions between three bases and one amino acid (of genetic code type) and also those between a dipeptide and a biosubstrate (of ligase, transferase, hydrolase, lyase, isomerase and dehydrogenase type). The Kms obtained for these dipeptide enzymes were of the order of 1M, in accord with the association constant for the binding of guanosine to cytocine in water. In this oligomer world, the genotype and phenotype evolution was closely coupled, resulting in a very rapid rate of evolution.
Redox Reactions in Lipid Membranes as a Model for Primordial Energy-Conserving Systems
Authors: Di Bernardo Salvatore , Fato Romana , Lenaz Giorgio
Published: July 2016

One of the peculiar aspects of living systems is the production and conservation of energy. This aspect is provided by specialized organelles, such as the mitochondria and chloroplasts, in developed living organisms. In primordial systems lacking specialized enzymatic complexes the energy supply was probably bound to the generation and maintenance of an asymmetric distribution of charged molecules in compartmentalized systems. On the basis of experimental evidence, we suggest that lipophilic quinones were involved in the generation of this asymmetrical distribution of charges through vectorial redox reactions across lipid membranes.
Self-Reproduction of Chemical Structures and the Question of the Transition to Life
Authors: Luisi Pier Luigi
Published: July 2016

The principles which underlay the chemical approach to the origin of life are discussed, beginning with Oparin’s notion of molecular evolution, whereby the minimal living emerged from the non livingviaa natural increase of molecular complexity and organization. The philosophical and methodological difficulties inherent in such a view are briefly examined. The scenario of the origin of life provided by the RNA-world is then reviewed, and the great difficulties inherent in this view are emphasized, particularly the one according to which a RNA family is createdex-novoin an enzymefree world in a way which is capable to self-replicate, mutation is concluded that the view of the RNA world for the origin of life, despite its popularity, is not very realistic at all; however it has a great importance as it has introduced a series of fundamental new concepts into the field of origin of life. Particularly important is the notion of self-reproduction, and in the paper the self-reproduction of vesicles is reviewed, pointing to the fact that it is a thermodynamically driven process based on spontaneously self-assembling macromolecualr aggregates. The possible relevance of these experiments for assessing a prebiotic «pre-RNA» world is discussed.
Results from Project Phoenix: Looking up from down Under
Authors: Tarter Jill C.
Published: July 2016

We used the Parkes and Mopra antennas of the Australia Telescope National Facility (ATNF) and observed 209 solar-type stars in the Southern hemisphere over much of the frequency range 1200-3000 MHz. The sensitivity of these observations was sufficient to rule out any narrow-band transmitters stronger than 5 × 1012Watts (the power of strong terrestrial radars) broadcasting during our observations. The use of two widely separated antennas, linked together as a pseudo-interferometer, proved to be an extremely effective discriminant against RFI. This mode of observing will be continued by Project Phoenix. Observations begin again in October of 1996, with the 140 foot antenna at NRAO Green Bank linked to an old AT&T Earth Station at Woodbury, Georgia that has been resuscitated by students and faculty at Georgia Tech Research Corporation. Later observations will make use of the Arecibo Observatory and the Nançay Observatory, each linked with a second site.
A Search for Artificial Signals from the Newly Discovered Planetarty Systems
Authors: Biraud François , Heidmann Jean , Tarter Jill C. , Airieau Sabine
Published: July 2016

We conducted a search for narrowband artificial signals from the regions of stars around which planetary companions have been recently found: 51 Pegasi, Gliese 229, 70 Virginis and 47 Ursae Majoris. We used the large Nançay decimetric telescope, with a frequency resolution of 50 Hz, and we scanned over 0.64 MHz and 2.24 MHz respectively around the hydrogen and hydroxyl lines.
A Call for Seti well into the 21st Century S for Search/Survey/Study/Sociology of ExtraTerrestrial Intelligence
Authors: Heidmann Jean
Published: July 2016

As soon as we unravel a first signal (if ever!), this will be the immediate proof that extraterrestrial civilizations are numerous in the cosmos and, within a few years, we should discover tens of them, as this happened often, e.g. for quasars, pulsars, gravitational lenses, and now for extrasolar planets. Then the drive to investigate them, in all of their expected varieties, will get very strong. We shall show that this prodigious perspective raises a large number of long-term issues whose investigations and solutions require an immediate call for collaborations at many interdisciplinary and international levels over the next quarter century. In particular, we witness both a remarkable increase of SETI technology efficiency – which over the last 30 years doubled every 8 months – and a sharp rise of man-made radio frequency interference. Thus we ought to save a dedicated lunar farside locale for the next generation (project SAHA). In addition we propose to use gravitational focuses of the Sun to investigate in tremendous detail some selected interesting extraterrestrial technologies (project FOCAL). We ought to think that SETI, after standing for SEARCH, will mean SURVEY, then STUDY, then SOCIOLOGY of ExtraTerrestrial Intelligences. It is time for some to abandon the idea that in case we do not get a signal «before next election year», SETI should be killed. Humankind is engaged, firmly now, into a long-term and far-sighted enterprise.
Unsolved Problems in Stellar Pulsation Physics
Authors: Cox Arthur N.
Published: July 2016

Unsolved problems of theoretical stellar pulsations are briefly reviewed for pulsators in six regions of the Hertzsprung-Russell diagram. Only a small selection is included in the discussion of them, and the emphasis is mostly on theoretical problems. The problem of the pulsations of Mira stars, and the mode in which it pulsates is reviewed in more detail together with some new calculations that illustrate the difficulties. Finally an extensive discussion is made for the pulsation mechanism of the white dwarf (DA and DB) pulsators. A new interpretation is advocated, which unfortunately is not tractable by linear nonadiabatic calculations because during the pulsation cycle it involves the turning off and on of Convection with a short time scale relative to the pulsation period. Most of the theoretical problems involve the time dependence of convection, a topic still without any concise and practical way of convenient implementation.
Tidal Modulation of Radial Oscillations in Components of Circular-Orbit Close Binaries
Authors: Reyniers T. , Smeyers P.
Published: July 2016

A theoretical description is presented of the modulation of a radial oscillation in a uniformly rotating star in a close binary that is subject to the tidal action of a companion moving in a circular orbit. The star is assumed to rotate non-synchronously with the companion’s orbital motion. A tidal modulation of a radial oscillation has been observed in the star θ Tucanae by Sterken (1997) and De Mey et al. (1998).
Multiperiodicity in the Line-Profile Variations of the Spectroscopic Binary β Cep Star λ Scorpii
Authors: Uytterhoeven K. , Aerts C.
Published: July 2016

A study of the rapid variations of the line profiles of λ Scorpii leads to the following new result: we find evidence for the presence of at least 5 periodicities in the intrinsic variations of λ Scorpii, which seem to be part of an equidistant multiplet. The modes associated to these periodicities are interpreted as non radial pulsation modes.
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

We 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

We 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.
Asteroseismology of β Cep: Influence of Updated Microphysics
Authors: Shibahashi H. , Koshikawa T.
Published: July 2016

With updated microphysics such as opacity, we revise the result of asteroseismic investigations for β Cephei and show the tolerable range of the physical parameters of the star.
Rapid Light Variations of the Bright Be Star ϕ Per
Authors: Sudar D. , Ruždjak D.
Published: July 2016

An 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.
Pulsations in roAp Stars
Authors: Cunha M.S.
Published: July 2016

The current status of the research concerning rapidly oscillating Ap stars is reviewed, paying particular attention to the interplay between recent developments in the theoretical and observational aspects of these stars.
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

Some 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

UV 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.
Do the Pre-Main Sequence δ Scuti Stars Really Exist?
Authors: Peña J.H. , Peniche R. , Plascencia J.C. , Hobart M.A. , de la Cruz C. , Garcia Cole A. , Cervantes F. , Sareyan J.P. , Parrao L. , Carrillo M. , Valdes T. , Prada I.
Published: July 2016

Recently, new views of the current status of δ Scuti stars have been developed by Rodríguez & Breger (2001) who carried out an excellent review, listing 8 pre-main-sequence (PMS) δ Scuti candidates and examined the possibility of the existence of PMS δ Scuti variable stars. Here we discuss the nature of 4 stars from their list: 2 said to be members of NGC 2264 and 2 of NGC 6823.
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

We 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

Photometric 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

We 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

The 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

We 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.
Aperiodic Ordered Sequences and Multiperiodicity in Semiregular Variable Stars
Authors: Escudero Juan García
Published: July 2016

The use of aperiodic ordered sequences described by Lindenmayer systems in the study of the strings of periods for multiperiodic semiregular variables is proposed. Fibonacci sequences play a central role in the light curve analysis of UW Herculis.
Stellar Parameters of the Post-AGB Star HD 56126
Authors: Le Coroller H. , Gillet D. , Fokin A.B. , Lèbre A.
Published: July 2016

We 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

The 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

The 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

We 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

I 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

The 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.
Solar 5-min Oscillations at 2.23 μm
Authors: Leifsen Torben
Published: July 2016

Large amplitude infrared 2.23 μm solar intensity oscillations were detected in photometer observations obtained at Oslo Solar Observatory in 1987 and 1988. Five wavelength regions ranging from 0.67 μm to 2.23 μm and 7 circular entrance apertures ranging from 0.5 to 4.3 arc min were observed simultaneously at all wavelengths with the same detector. The 2.23 μm region showed remarkably higher amplitudes than the other 4 wavelength-regions. The observed power was concentrated to the 2.5 - 3.5 mHz region suggesting that we observe the well known 5 min oscillations (Leifsen and Maltby, 1990).
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

We 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.
Observed and Computed Features around Li I 6708 in Normal A and Early F Stars
Authors: Gerbaldi M. , Faraggiana R. , Castelli F.
Published: July 2016

For a set of normal A and early F type stars, we discuss the possible contributors which can affect the Li feature and their effect on the determination of the Li abundance.
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.
On the Influence of the Treatment of Heavy Elements in the Equation of State on the Resulting Values of the Adiabatic Exponent Γ1
Authors: Däppen W. , Gough D.O. , Kosovichev A.G. , Rhodes E.J.
Published: July 2016

Helioseismology and asteroseismology put high demands on the accuracy and consistent numerical realization of the equation of state (for a review see Däppen, these proceedings). This is explicitly illustrated by the helioseismic determination of the helium abundance of the solar convection zone in a recent investigation by Kosovichev et al. (1992). In that work it was observed that details of the treatment of the heavy elements matter more than is intuitively expected. Naively, one would expect an uncertainty of less than 10−4 in the key thermodynamic quantity, the adiabatic gradient Γ1. This is because in material of solar composition the heavy-element abundance is less than about 1.5 × 10−3 by number, and under solar conditions the dominant nontrivial contributions to the seismically relevant thermodynamic quantities predicted by modern equations of state agree to a few per cent, even for the much more abundant hydrogen and helium. However, Kosovichev et al. (1992) found that uncertainties in the treatment of the heavy elements translate into discrepancies in Γ1 of the order of 10−3, which is enough to disturb the helioseismic helium-abundance determination significantly. We briefly present the reason below. A forthcoming paper will show more detailed results, though some further information can already be found in papers by Kosovichev et al. (1992) and Christensen–Dalsgaard & Däppen (1992).
Measurements of Masses and Radii of Eclipsing Binaries
Authors: Ferluga S. , Floreano L. , Mangiacapra D.
Published: July 2016

We 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.
Comparing Catalogues of Stellar Absolute Magnitudes and Estimating their Accuracy
Authors: Malyuto V.
Published: July 2016

The accuracy of spectral, photometric and astrometric catalogues of stellar absolute magnitudes of F-subgiants and dwarfs has been estimated from a comparison of the data for stars in common.
Pulsation Theory and Stellar Structure
Authors: Christensen-Dalsgaard J.
Published: July 2016

Observed periods of pulsating stars provide information about the properties of the stars. As examples I here consider double-mode pulsators, solar-like oscillations and δ Scuti stars. The ongoing expansion in the observational efforts in this area may be expected to lead to increasingly detailed tests of stellar evolution theory.
Mode Selection and Other Nonlinear Phenomena in Stellar Oscillations
Authors: Dziembowski W.A.
Published: July 2016

Nonlinear 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

Detection 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

The 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.
CCD Asteroseismology of Open Clusters
Authors: Vidal Inmaculada , Belmonte Juan A.
Published: July 2016

In the last few years Asteroseismology has contributed to the knowledge of stellar interior, in some extend. This contribution has been done with -observations, providing the characteristics of the acuostic modes of stellar oscillations; and with theory relating them to inner parameters, locating stars in the JCD diagram (Christesen-Dalsgaard J., 1989). At the beginning only classical pulsating stars had high enough amplitudes able to be detected. But techniques have been improved and now the goal is the detection of oscillations in all kind of stars, specially solar-like ones. Up to now, few cases of possible detections have been reported, the best evidences are: Belmonte et al (1990) in an FV star, Brown et al (1991) on the subgigant Procyon, and Pottasch et al (1992), in α Cen.
Stellar Evolution and Mass Transfer in Binaries
Authors: Bojarchuk A.A. , Chechetkin V.M. , Kuznetzov O.A. , Popov Yu.P.
Published: July 2016

The problem of angular momentum loss in binaries and its influence on stellar evolution is considered. The results of 2D hydrodynamics computer simulation of mass transfer is presented.
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

In 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

The 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

High 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

Interferometric 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.
Supplying Gas for Nuclear Star Formation: The Central Molecular Spiral of IC 342
Authors: Levine D. A. , Turner J. L. , Hurt R. L.
Published: July 2016

IC 342 is a large nearby (1.8Mpc) spiral galaxy undergoing a moderate nuclear starburst. Previous maps of the inner arc minute in 13CO (1→0) show that the nuclear molecular gas forms spiral arms approximately 500 pc in extent in a density wave pattern (Turner & Hurt, 1992).
CS(3-2) in Nearby Starburst Galaxies M82 and NGC253
Authors: Ishizuki Sumio , Kawabe Ryohei , Ishiguro Masato
Published: July 2016

Dense gas in molecular cloud cores is essential in researches of extragalactic star formation (e.g. Solomon, Downes, and Radford). To determine the physical relations between star-forming regions and dense gas, we have observed CS (J=3→2) in starburst galaxies M 82 and NGC253. The J = 3 level of CS is 14.1 K and the critical density for excitation is 4 × 105 cm−3.
The Large Millimeter Array
Authors: Ishiguro M. , Kawabe R. , Nakai N. , Morita K.-I. , Okumura S. K. , Ohashi N.
Published: July 2016

In 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

This 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

Elemental 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.
Chemically Peculiar Stars Among Spectroscopic Binaries – Revisited
Authors: Seggewiss Wilhelm
Published: July 2016

This paper presents a new statistical investigation of peculiar A-type stars (Am, Ap, Hg-Mn) among spectroscopic binary (SB) stars. The relative frequency of Am (CP 1) stars is 55% in the spectral range A1 to A6 of main-sequence stars. The Ap (CP 2) stars amount to 15% in the range B9 to A2. The Hg-Mn stars are concentrated to the spectral types B8 to AO and reach a relative frequency of 23%. The Am SB stars have the shortest orbital periods and the smallest eccentricities (30% circular) whereas the Ap SB stars show a strong tendency to long periods and highly eccentric orbits (only 10% circular). The masses of the Am stars agree with the masses of non-peculiar SB stars of corresponding spectral type.
Li in Clusters: A and Am Stars
Authors: Burkhart C. , Coupry M.F.
Published: July 2016

A and Am stars were observed in open clusters for their Li content. The Li abundance is therefore studied on the hot side of the Li gap along isochrones. It is discussed in relation to evolutionary model atmospheres including particle transport processes.
Magnetic Fields: Observations and Topology
Authors: Landstreet J. D.
Published: July 2016

To understand the complex physical processes revealed by the wide variety of surface chemical abundances and the inhomogeneous distributions of various elements over the surfaces of magnetic Ap and Bp stars, it is important to be able to describe the surface magnetic field structure. For most magnetic stars, the available observations are far from sufficient to define the surface magnetic structure even with low resolution, but more extensive and constraining observations are gradually becoming available for a small set of stars. This paper discusses the extent to which the surface field structure can be defined for stars for which only the usual measurements (essentially the variation of the mean longitudinal field strength Bɩ with rotational phase) are available, and how further information (variation of mean field modulus Bs with phase, line profile observations, and circular and linear spectropolarimetry of absorption lines or broad-band radiation) can be used to obtain a much more detailed picture of the magnetic field structure.
Broadband Measurements of the Transverse Magnetic Field of Cool Ap Stars
Authors: Leroy J.-L. , Landstreet J.D. , degl’Innocenti E. Landi , Landolfi M.
Published: July 2016

Observations of variable broadband linear polarization in magnetic Ap stars (due to the transverse Zeeman effect), when combined with measurements of the mean longitudinal field Bɩ can in some cases allow one to determine the angles i and β (which describe the inclination of the stellar axis of rotation and the obliquity of the magnetic axis to the rotation axis) much more accurately than these angles can be determined from observations of Bɩ alone. Such variable intrinsic linear polarization has been observed for a number of stars; the effect is generally detectable only in cool Ap stars of unusually large field strength. We discuss the data and simple modelling for the stars HD 24712 = HR 1217, HD 137909 = β CrB, and HD 62140 = 49 Cam.
Broadband Linear Polarization in Ap Stars
Authors: Landolfi Marco , Degl’Innocenti Egidio Landi , Degl’Innocenti Maurizio Landi , Leroy Jean-Louis , Bagnulo Stefano
Published: July 2016

Broadband linear polarization in the spectra of Ap stars is believed to be due to differential saturation between σ and π Zeeman components in spectral lines. This mechanism has been known for a long time to be the main agent of a similar phenomenon observed in sunspots. Since this phenomenon has been carefully calibrated in the solar case, it can be confidently used to deduce the magnetic field of Ap stars.

Given the magnetic configuration of a rotating star, it is possible to deduce the broadband polarization at any phase. Calculations performed for the oblique dipole model show that the resulting polarization diagrams are very sensitive to the values of i (the angle between the rotation axis and the line of sight) and β (the angle between the rotation and magnetic axes). The dependence on i and β is such that the four-fold ambiguity typical of the circular polarization observations ((i,β), (β,i), (π-i,π-β), (π-β,π-i)) can be removed.
Variations of Ultra-Violet Lines for C, N, and O in the Ap Stars HD 18296 and HD 25823
Authors: Gonzalez Jean-François , Artru Marie-Christine
Published: July 2016

From the rotational variation of UV resonance lines of carbon, nitrogen, and oxygen, we study the irregular distribution of these elements upon the surface of two magnetic Ap stars: HD 18296 (21 Per) and HD 25823 (41 Tau).
Search for λ Bootis Stars in Open Clusters
Authors: Pavlovski K. , Schnell A. , Maitzen H.M.
Published: July 2016

It was shown by Maitzen & Pavlovski (1989) that a majority of λ Bootis stars stand out by negative Δα indices. Using this as detection tool, three candidate stars with λ Bootis characteristics are picked up in open cluster Praesepe.
Determination of Luminosity, Atmospheric Structure, and Magnetic Geometry from Studies of the Pulsation in roAp Stars
Authors: Kurtz D. W. , Martinez Peter
Published: July 2016

For several of the rapidly oscillating Ap stars the best luminosity estimates available come from the asteroseismological interpretation of their pulsational frequency spectra. We give a list of the 23 currently known roAp stars along with their Strömgren photometric indices, Teffestimated from the Hβindex, and luminosity estimated asteroseismologically. In one case,ϒEqu, we have an asteroseismological luminosity and a parallax luminosity which are in good agreement. Some of the roAp stars pulsate with frequencies greater than the critical frequency calculated for standard A-star models. This plus multi-colour high-speed photometry of HR 3831 indicate that the temperature gradients in the atmospheres of these stars are substantially steeper than in standard A-star models. We advocate a fine analysis of HR 3831 to see if there is consistency with the pulsational conclusions about T-τin this star. Further fine analyses and multi-colour pulsational analyses on other roAp stars are then called for. The pulsation mode in HR 3831 can be decomposed into primarily an axisymmetric dipole mode with small radial, quadrupole and octupole perturbations. If the magnetic field is governing the distortion of this mode from a purely dipole mode, then the pulsation can be used to infer the magnetic field geometry. Comments on our current knowledge of all 23 roAp stars are made.
Growth Rate in the Study of Normal and Chemically Peculiar Stars of the Upper Main Sequence
Authors: Jugaku Jun
Published: July 2016

The research papers on normal and chemically peculiar stars of the upper main sequence are counted in the “Astronomy and Astrophysics Abstracts” for eight sample years in the period 1970-1990.
Computation of Frequencies and Linestrengths for Triatomic Molecules of Astronomical Interest
Authors: Miller Steven , Tennyson Jonathan , Jones Hugh R.A. , Longmore Andrew J.
Published: July 2016

Molecular bands have been used as a diagnostic of spectral type since the 1860's. TiO was first identified as the dominant feature in optical spectra of cool giants in 1904 (Fowler 1904). Many diatomic molecules have now been included (e.g. Jørgensen & Larsson 1990) in detailed calculations of stellar opacity and attention is starting to focus on the incorporation of accurate data for triatomics. Triatomic molecules have a much greater density of states than diatomics; bending vibrational bands - generally lower in frequency than bond-stretching modes - may contribute considerably to “filling in” spectral gaps.
CCDs on the Curtis Schmidt Telescope
Authors: Seitzer Patrick , Houk Nancy
Published: July 2016

The University of Michigan’s Curtis Schmidt Telescope at CTIO has recently been equipped for CCD imaging at the Newtonian focus. A review is presented of the current status of this telescope, future upgrades, and some of the science being conducted.