bluuebunny/crossref_metadata_2025_split huggingface dataset:
Search for Life in the Universe with terrestrial microbes which Thrive under Extreme Conditions
Authors: Seckbach Joseph 
Published: July 2016

AbstractIt is reasonable to believe that life exists in many places throughout the Universe. Among the many billions of heavenly bodies, there are galaxies with millions of stars that may harbor lower or even higher forms of living organisms («life» in the meaning as we know it, e.g., carbon chemistry, liquid water etc.). This article lists Extremophiles and their various terrestrial enigmatic environments. We discuss the possibilities of Martian life and the origin and evolution of the eukaryotic cell and present some early protists and the Acidothermophilic algae. Among several microbes which can «fit» for extraterrestrial life, one eukaryotic algal group (Cyanidiophyceae) is treated here. The hot springCyanidium caldariummembers (there are three genera and several species in this family) thrive in excessive growth conditions like in acidic medium (close to IN H2SO4), under pure CO2atmosphere, in elevated temperature and auto or heterotrophic conditions. These hot spring unicellular algae do not require oxygen for such conditions of growth. Studies have shown that they present one of the earliest and simplest eukaryotic algae. Also, these microbes may be candidates for existing on planets with similar ecological conditions which might support life forms.
On the Existence of Stable Isolated Ecosystems outside the Earth
Authors: Benci Vieri , Galleni Lodovico , Santini Francesco 
Published: July 2016

AbstractThe planetary biosphere can easily be recognised because, according to the British scientist James Lovelock, living beings maintain the atmosphere of a planet far from chemical equilibrium. According to this idea it is thought that within the solar system there is no life outside the planet Earth. But this is true if we suppose that all the ecosystems are interconnected and easily detectable, because their presence would have effects at a planetary level. After the discovery since the end of the seventies of a series of ecosystems that do not have their source of energy in solar light and which are more or less isolated from other ecosystems is it possible to hypothesize the existence of biospheres being smaller than the planetary biosphere?
Non-Repeatable Seti Signals due to Gravity-Plasma Lenses of Stars
Authors: Eshleman Von R. 
Published: July 2016

AbstractIt is possible that signals from other technological societies have been received at radio listening sites on Earth, but their artifactual nature was not recognized. Such unrecognized SETI detections could come about if the amplitudes of the signals were above receiver thresholds only because of strong focusing by the compound gravity-plasma lens of a star. Variations in time and space of the plasma envelope of the star, and the temporary geometry of a star being situated directly on the line between Earth and the source, results in lensed signals that may never be repeated. Perhaps the only hope of recognizing a SETI source by means of transitory lensing rests with the attainment of a detailed understanding of the characteristics of the gravity-plasma lenses of stars. These lenses produce extended focal surfaces, a semi-infinite focal line, and a single point double-caustic focus, all of which vary in position and strength with the wavelength of the radiation. If the direction to a SETI source were to be determined, it might be possible to maintain the connection by use of spacecraft sent far from the sun so as to employ its gravity-plasma lens.
On a Broader Concept of Circumstellar Habitable Zones
Authors: Illés-Almár Erzsebet , Almár Ivan , Bérczi Szaniszlo , Lukács Bela 
Published: July 2016

AbstractWe suggest the possibility of a broader circumstellar habitable zone than considered so far. The factors taken into account – in addition to greenhouse effect – are tidal heating, and the role of ammonia (A) as a possible solvent instead of water (W) for biogenic materials. These factors can push the outer limit of the circumstellar habitable zones even further from their central stars.
δ Sct-Type Pulsators in Eclipsing Binary Systems: the Case of RZ Cas
Authors: Rodríguez E. , Costa V. , López-González M.J. , García J.M. , Kim S.L. , Lee J.W. , Yoon J.H. , Hintz E. , Mkrtichian D.E. , Gamarova A.Y. , Kusakin A.V. 
Published: July 2016

AbstractRZ Cas is an Algol-type eclipsing binary system where the primary component was recently discovered as a δ Set pulsator. A three-continent multisite photometric campaign was carried out during 1999. Preliminary results are reported here indicating a semi-detached system where the secondary fills its Roche lobe. The light curves also suggest a hot spot on the surface of the primary component as a consequence of the impact of the mass stream from the secondary. The pulsational behaviour can be well described with only one frequency.
The Carina Dwarf Galaxy Variable Star Population
Authors: Ripepi V. , Dall’Ora M. , Pulone L. , Castellani M. , Corsi C. , Monelli M. , Bono G. , Brocato E. , Caputo F. , Castellani V. , Marconi M. , Nonino M. , Smith H. , Walker A.R. 
Published: July 2016

AbstractWe present some preliminary results based on new observations of the variable stars belonging to the Carina Dwarf Galaxy (DG). Photometric data were collected with the two wide field imagers available at ESO (WFI@2.2.) and CTIO (4m prime focus).
Search for New γ Doradus Variable Stars in Open Clusters: Praesepe and α Persei
Authors: Martín S. , Rodríguez E. 
Published: July 2016

AbstractPhotometric observations of A-F stars in the uvbyβ system have been performed in order to detect γ Doradus variables in open clusters of different ages. In the clusters Praesepe and α Per, several stars show some type of variability but only three of them, KW370 (Praesepe) and HE104 and HE876 (α Per), can be classified as γ Doradus-type pulsators.
WWW Archive of Fourier Coefficients
Authors: Morgan S. 
Published: July 2016

AbstractFourier coefficients are a valuable tool in the study of a wide variety of pulsating stars. They can be used to derive various physical parameters, including mass, luminosity, metallicity and effective temperature and are frequently used to discriminate between different pulsation modes. With the increase in large-scale surveys and the availability of data on the Internet, the number of Fourier coefficients available for study has expanded greatly and it is difficult to find all current data for individual stars or a subset of stars. To assist others in obtaining and making use of Fourier coefficients, an archive of published values of Fourier coefficients has been set up. Users can search for data on individual stars or for a range of parameters. Several Java programs are used to display the data in a variety of ways. The archive is located at the Web site http://www.earth.uni.edu/fourier/.
Primary Observational Distributions of δ Scuti Variables
Authors: Rodríguez E. , Breger M. 
Published: July 2016

The distribution of the known δ Scuti-type variables (R00 catalogue, Rodríguez et al., 2000) is analysed on the basis of some primary observational properties such as visual amplitude, period, visual magnitude and rotational velocities. The present distributions are also compared with those resulting from the earlier catalogue by Rodríguez et al. (1994, R94). The contributions from the Hipparcos, OGLE and MACHO long-term monitoring projects are also discussed. These contributions are quite different in the N-ΔV and N-V diagrams, in the sense that the variables discovered by the Hipparcos satellite are much brighter and with shorter periods than those discovered by the OGLE and MACHO projects.Concerning the N-ΔV diagram, we find that the gap, which was evident in the R94 catalogue for variables with visual amplitudes between 0.m1 to 0.m3, has disappeared. Thus, it seems that there is not a strict separation in two groups relative to the amplitude (low amplitude for variables with ΔV<0.m1 and high amplitude for variables with ΔV>0.m3) for the δ Scuti-type pulsatore.
Multiperiodicity in the Delta Scuti Star HR 4047
Authors: Rolland A. , Rodríguez E. , Costa V. , Olivares I. , García-Pelayo J.M. , de Coca P. López , Hobart M.A. 
Published: July 2016

HR 4047 (HD 89343, EN UMa, V = 592, A7Vn) was found to be variable (Plume & Percy, 1988) with an amplitude of hundredths of a magnitude. Since then, this star has been observed by HIPPARCOS. Koen (2001), analysing those data, obtained two frequencies 6.43185 c d-1 and 4.31308 c d-1.Our observations were made at the Observatorio de Sierra Nevada in Spain in 1997 and 1998 with the telescope of 0.9m. The comparisons stars for 1997 were C1 = HD 88983 (V = 577, A8III) and C2 = HD 88815 (V = 642, F2V), while for 1998 we add the check star C3 = HD 90838 (V = 7.30, F2). The photometric data obtained were analyzed using the Fourier Transform method in the Strömgren v filter. The periodogram of the v band data is shown in Fig. 1. The periodogram presents six clear frequencies and after prewhitening these there is still more power, but the frequencies found are not consistent between the different bands. Applying these frequencies to the data of the 1997 and 1998 separately, we obtain the results shown in Table 1. Note that the amplitudes have changed from one year to another. The results of 1998 agree with the two frequencies found by Koen (2001). Fig. 1 shows the light curves of the observed data for both campaigns in the v filter. The points represent the observations while the solid lines represent the fit for the frequencies listed in Table 1. Further observations are needed to obtain a more detailed pulsational behaviour of this star.
Identifying Modes in a Pulsating sdB (EC 14026) Star
Authors: Reed M.D. ,   the Whole Earth Telescope Xcov 17 and 21 teams
Published: July 2016

AbstractWe present a preliminary analysis of time series photometry on the pulsating subdwarf B star PG 1336-018 acquired as part of two Whole Earth Telescope runs. PG 1336-018 is a multi-mode pulsator with at least 15 periods centered around 175 seconds. It is also an HW Vir-type eclipsing binary with a period of 2.4 hours. Although over 20 pulsating subdwarf B stars have been discovered, only a few have resolved temporal spectra and still fewer have identified pulsation modes. We analyze features unique to the eclipsing binary system of PG 1336-018 as a means of identifying pulsation modes.
Seismic Constraint on the Plausible Explanations of the Metal Rich Feature of Planetary System Stars
Authors: Shibahashi H. , Watanabe S. 
Published: July 2016

AbstractFrom Spectroscopic observations showing that the parent stars of planetary systems are metal rich, it is suspected that this feature results from the accompanying planetary system. With the rich helioseismic data so far obtained, we determine the metal abundance distribution in the solar interior with respect to the distance from the center. This result gives constraints on the possible explanations about the metal rich feature of the stars accompanied by a planetary system.
Wavelet Analysis of the RV Tauri Star U Mon
Authors: McSaveney J.A. , Cottrell P.L. , Pollard K.R. , Mattei J.A. 
Published: July 2016

AbstractWavelet analysis has been performed on the American Association of Variable Star Observers (AAVSO) visual estimates of the RV Tauri star U Mon from 1961-2000 using the AAVSO WWZ wavelet analysis program. Periods of 46.07, 92.40 and 2498 days are present but the 92 day period is not always detectable. A constant ratio between the amplitudes of the 46 and 92 day periods is found during one single long-term deep minimum but not another.
Constraints on 12C(α,γ)16O from White Dwarf Seismology
Authors: Metcalfe T.S. , Salaris M. , Winget D.E. 
Published: July 2016

AbstractFor many years, astronomers have promised that the study of pulsating white dwarfs would ultimately lead to useful information about the physics of matter under extreme conditions of temperature and pressure. We can now make good on that promise. Using observational data from the Whole Earth Telescope and a new analysis method employing a genetic algorithm, we empirically determine the central oxygen abundance of the helium-atmosphere variable white dwarf GD 358. We use this value, combined with detailed evolutionary calculations of the internal chemical profiles, to place constraints on the 12C(α, γ)16O nuclear reaction cross-section.
Energy Distributions and Fundamental Parameters of 6 A Stars
Authors: Monier R. 
Published: July 2016

AbstractThe energy distributions (EDs) of 6 peculiar (3 Aps and 3 λ Bootis) stars are presented from 1200Ȧ up to about 12000Ȧ. For those stars having infrared photometry, the integrated flux from 1200& to 22000Å has been calculated and the Infrared Flux Method (IRFM, Blackwell and Shallis, 1977) applied to derive effective temperatures and angular diameters. For all stars, the effective temperature Teff, the surface gravity logg and metallicity [M/H] were also derived by matching the EDs to a grid of model atmospheres. A chisquare techniques is used to sort out the best fit to the observed EDs.
Beryllium in Lithium–Deficient F Stars: Constraints on Stellar Evolution
Authors: Deliyannis Constantine P. , Pinsonneault M.H. 
Published: July 2016

AbstractStandard stellar evolution predicts that F stars should retain their initial surface lithium (Li) abundance because their convection zones are too shallow to destroy it at their base. Yet, observations reveal a severe Li depletion (the “Boesgaard Gap”), perhaps by as much as about two orders of magnitude, in a narrow Teff range. Several physical mechanisms, not usually included in stellar evolution calculations, have been proposed to account for this Li deficiency. These include diffusion, mass loss, meridional circulation, and rotationally-induced mixing driven by angular momentum loss. Identifying which of these (if any) might really be at work is not only of vital interest to stellar evolution, but may also have serious implications elsewhere (e.g. cosmology, Deliyannis et al. 1991). We bring attention to beryllium (Be) observations in F stars, which are crucial for discriminating between scenarios. Particularly important is the star 110 Her, which is depleted in Be by about a factor of 5 -10, but still has a detectable Li abundance (depleted by a factor of 100 - 200). Depleting surface Be without having depleted nearly all of the surface Li requires specific circumstances; we discuss how this depletion property severely constrains or eliminates most of the proposed mechanisms. One mechanism, rotationally-induced mixing, predicts relative depletions for these elements that agree well with what is observed.
Oxygen Abundances in LI-Depleted F-Type Stars
Authors: Lopez Ramon J. Garcia , Rebolo Rafael , Herrero Artemio , Beckman John E. 
Published: July 2016

AbstractWe have obtained the oxygen abundance in a sample of 44 F-type dwarfs in the Ursa Major group and the Hyades open cluster, using an NLTE analysis of the O I infrared triplet at λλ 7771-7775 Å. These clusters show the “lithium gap” in the F spectral range, and it has been suggested that if this phenomenon were due to microscopic diffusion, their Li-depleted stars could also show oxygen and/or nitrogen depletion. Our results here show a substantial measure of uniformity in the oxygen abundances. The data might indicate a very small dip (< 0.1 dex) in the O abundance for stars located in the Li gap. Microscopic diffusion seems to be the only known mechanism able to produce an oxygen dip. If this mechanism were responsible for the Li gap, it would have to account for a depletion of up to two orders of magnitude in Li and, at the same time, less than 0.1 dex in oxygen. We note that turbulent mixing could modify a microscopic diffusion pattern in order to yield the observed abundances of the two elements.
Evolution of massive stars: main sequence and close to it
Authors: Langer Norbert 
Published: July 2016

AbstractWe discuss the status of current models for the early evolutionary stages of stars in the initial mass range 10-40 M⊙. Effects of the pre-main sequence evolution, mass loss, internal mixing, and changes in atomic and nuclear data are outlined and confronted with several basic observational facts, which are unexplained by standard models. We conclude that especially internal mixing processes deserve much more attention in future investigations, and we show why convective mixing may be less efficient than generally assumed, but more mixing should be present in the radiative zones of at least a fraction of all massive stars.
About Seismological Properties of Intermediate Mass Stars
Authors: Audard N. , Provost J. 
Published: July 2016

AbstractStars more massive than about 1.2M⊙ are characterised by a convective core, which induces at its frontier a rapid variation of the sound speed and of the Brunt-Väissälä frequency, close to a discontinuity. We present preliminary results about the search of the signature this core could have on the p-mode spectra. For a set of frequencies of three stars of 1, 1.5 and 2 M⊙, we study in particular the small frequency separation Δν0,2, ~ νn,l, νn-1,l+2 for high order and low degree oscillation modes, which is particularly sensitive to the interior of stars. We underline characteristic behaviours of the 1.5 and 2 M⊙ stars, through the comparison between computed frequencies and their approximation obtained by asymptotic and polynomial fittings, and also through second order quantities relatively to the frequencies.
Dust Driven Winds from Pulsating Stars
Authors: Dorfi E.A. , Feuchtinger M.U. , Höfner S. 
Published: July 2016

The cool extended atmospheres of late type giants are sites where dust formation takes place. Radiation pressure on the dust grains is an important force for driving the slow but massive winds observed in such objects. Existing calculations of dust driven stellar winds (e.g. Bowen 1988, Fleischer et al. 1991) suffer from the fact that they include approximations at various levels for different parts of the problem like the hydrodynamics or the dust formation. Furthermore they do not include time-dependent radiative transfer.In order to overcome these insufficiencies we plan to calculate self-consistent models of dust driven winds with a full description of both the radiation hydrodynamics and the time-dependent dust formation. As a first step, however, we concentrate our investigations on the self-consistent description of the radiation hydrodynamics adopting only a simple description of the dust opacities.
Asteroseismology From The Ground
Authors: Frandsen S. 
Published: July 2016

AbstractIn stars which pulsate in more than one mode, be it acoustic or gravity modes, radial or non-radial, we have a chance to study the interior structure by use of seismic techniques. Generally the greater the number of modes observable the greater the chances will be to obtain valuable direct information about the stellar interior not accessible by any other technique.The observational problem of acquiring high quality data divides the stars where seismic techniques can be applied into two groups: A group of stars with intensity amplitudes in the range of millimagnitudes and the stars with very small amplitudes around 10 μmagnitudes or less. The first group contains the white dwarfs, the rapidly oscillating Ap stars, the δ-Scuti stars and the β-Cephei stars. The modes are excited directly or indirectly by some form of к-mechanism due to an opacity source which vary from class to class. The second group is made up of stars with outer convective envelopes which generate acoustic noise that may excite resonant modes, often a very large number.This paper is a discussion of the possibilities for observing these stars with ground based techniques, and also a statement about what can not be done from the ground.
The AFOE—A New Instrument for Asteroseismology
Authors: Noyes R.W. , Brown T.M. , Horner S. , Korzennik S. , Nisenson P. 
Published: July 2016

AbstractWe describe technical aspects and performance characteristics of an Advanced Fiber Optic Spectrograph (AFOE), planned for the Mt. Hopkins 1.5 m telescope for asteroseismology of sun-like stars.
SOHO: A Prisma Precursor
Authors: Lemaire P. 
Published: July 2016

AbstractProbing the interior of the Sun, a slow rotator G2 V main sequence star, and connecting the atmospheric structure to inside phenomena is one of the objectives of the SOHO mission. An overview of the helioseismology and of the coronal instruments is given. It furnishes a guide line for missions that are dedicated to the probing of stellar interiors in using microvariability and activity as tracers, such as the PRISMA study.
Signal Processing Developments for the OVRO Array
Authors: Padin Stephen , Soares Schubert F. 
Published: July 2016

Abstract An optical fiber IF transmission and tracking delay system and a wideband continuum correlator have been developed for the Owens Valley (OVRO) Millimeter Array. The IF system processes two 1-2 GHz bands which are frequency multiplexed through an optical fiber link. This allows simultaneous dual wavelength observations in the 2.7 and 1.3-mm bands or dual polarization observations in either band.
Inclination of the HCO+ Torus in the NGC7027 Molecular Envelope
Authors: Yamamura Issei , Deguchi Shuji 
Published: July 2016

AbstractWe have determined the inclination of the axis of the HCO+torus in NGC 7027 to the line of sight, based on interferometrie observations and model calculations. We found that the deduced inclination of the HCO+ torus is misaligned with the inclination of the major axis of the ionized core. The result may imply the precession of the axis of the axisymmetric mass loss.
Disks Around T Tauri Stars
Authors: Sargent Anneila , Beckwith Steven 
Published: July 2016

AbstractA variety of evidence suggests that at least 50% of T Tauri stars are surrounded by disks of gas and dust. Inferred disk properties are compatible with those generally attributed to the solar nebula, before the formation of planets. Millimeter-wave aperture synthesis mapping of molecular line and dust continuum emission from T Tauri stars provides a direct way to ascertain if disks are present. The technique enables detailed studies of disk temperature and density distributions, chemical properties and velocity fields. These results inform our understanding of both star formation and solar system evolution. We review the observations to date and discuss directions for future research.
Fine Structure of Shocked Photodissociation Regions in the Orion Bright Bar
Authors: Omodaka Toshihiro , Murata Yasuhiro , Hayashi Masahiko , Kitamura Yoshimi , Ohishi Masatoshi 
Published: July 2016

The Orion bright bar is a prominent ionization front located approximately 2’ southeast of the Trapezium stars. Because this ionization front is seen almost edge-on, it provides an opportunity to study the interaction between the HII region and the adjacent molecular cloud. The molecular bar has been thought to be a narrow layer of ~ 50” (0.1 pc) in width parallel to the ionization front with enhanced temperature, density and column density. The molecular gas outside the ionization front was redshifted with respect to the ambient molecular cloud by 1-2 kms−1 (Omodaka et al. 1984, 1986, 1992), suggesting that the expanding HII region generated by the Trapezium stars had driven a shock wave into the molecular cloud at the southeast of the bar. This layer is exposed to intense UV radiation from the Trapezium stars, resulting in the formation of photodissociated regions.We have made aperture synthesis observations of CS(J=1-0) line and 49 GHz continuum in the Orion bright bar with the Nobeyama Millimeter Array. Figure 1, a map of integrated intensities of CS, clearly revealed fine structures of the molecular bar and more than six prominent features are confirmed. It is noted that these features are lined up at 30” from the ionization front inside the molecular cloud.