bluuebunny/crossref_metadata_2025_split huggingface dataset:
HRSP — A dedicated echelle reduction software package for Hercules
Authors: Skuljan Jovan 
Published: July 2016

AbstractA collection of computer programs called the Hercules Reduction Software Package (HRSP) has been developed in the Department of Physics and Astronomy, University of Canterbury, for the data reduction of échelle spectra obtained with the Hercules spectrograph. The main goal in writing a dedicated software package for Hercules was to achieve a highly-optimized reduction process that would provide the basis of a pipeline reduction performed at the Mt John University Observatory. Since the spectrograph has no moving parts, the spectrum produced in the focal plane does not move or change, so that the same reduction procedure can be applied to all CCD images. An optimized routine written especially for Hercules is always much more efficient and reliable than any general-purpose software available. HRSP is written in C and the whole reduction procedure is performed on standard FITS files. A standard échelle reduction is applied, including the background and cosmic ray subtraction, order extraction, flat-fielding, normalization and wavelength rebinning. A special feature is the radial velocity determination by cross-correlation, which has been tested extensively over the past two years proving that Hercules is capable of delivering the high-precision radial velocities needed for detailed studying of binary stars, stellar pulsations, extra-solar planets and other related fields.
The Distance and Age of the Globular Cluster M5
Authors: Carney Bruce W. , Latham David W. , Jones Rodney V. , Beck Judy A. 
Published: July 2016

AbstractUsing optical and infrared photometry and echelle spectroscopy of variable V8 in the globular cluster M5, we derive a cluster distance of 6.8 kpc using the Baade-Wesselink method. This agrees with the prediction obtained for the cluster’s metallicity using a sample of 19 field stars studied by us and by Liu and Janes (this volume). It also agrees well with estimates for Mv obtained from statistical parallaxes of field stars. It agrees as well with the main sequence fitting procedure where we have used only HD 103095, the field halo dwarf with the most accurate trigonometric parallax (3% error), and which has a metallicity almost identical to that of M5. The star is also cool, hence unevolved, and is not a binary. Using the luminosity of the cluster’s main sequence, both Yale and Victoria isochrones yield a cluster age of 18 ± 3 Gyrs.
Period Doubling in Variable Stars: A Tentative Interpretation of Oberved Light Curves of Variable White Dwarfs and Mira Stars
Authors: Goupil M.J. , Baglin A. , Auvergne M. 
Published: July 2016

AbstractIrregular pulsations are commonly observed in many groups of pulsating stars. An interpretation in terms of superposition of modes of pulsation is sometimes barely convincing when too many modes have to be considered and when unexpected ratios of frequenceis are observed.
The Luminosities of 13 Field RR Lyrae Stars: The Correlation with Metallicities
Authors: Liu T. , Joens K.A. 
Published: July 2016

AbstractWe have obtained UBVRI and JK photometry and radial velocities for 13 field RR Lyrae stars with a large range of metallicity. Our sample includes eleven ab-type and two c-type variables. The surface brightness method is applied to these RR Lyrae stars to determine their mean absolute magnitudes <MV> as well as their distances and radii. We have used the Kurucz’s model atmospheres to provide metallicity- and gravity-dependent color-temperature transformations and bolometric corrections. Our results indicate a clear correlation between the luminosities of the RR Lyrae stars and their metallicities such that metal-poor RR Lyrae stars are more luminous.
Globular Cluster Distances from the RR Lyrae Log (Period) – Infrared Magnitude Relation
Authors: Longmore A.J. , Dixon R. , Skillen I. , Jameson R.F. , Fernley J.A. 
Published: July 2016

AbstractThe log (Period) – infrared (2.2 micron) magnitude relationship has been measured for 7 clusters (M3, M4, M5, M15, M107, ω Cen and NGC 5466). For the clusters where there are several observations for each of the variables, enabling a good mean magnitude to be derived, there is no evidence for scatter in the relation outside observational error. This conclusion applies also to ω Cen, even though the variables observed covered a range of metallicity. It is argued that very accurate relative distances can be obtained which are insensitive to reddening errors and the effects of metallicity. Any mass difference between variables in different clusters may still introduce uncertainties in the relative distances. Recent Baade-Wesselink results by Fernley et al. have been used as an absolute calibration, including a small residual correction for metallicity effects. On this scale, the mean distance modulus for 6 of the clusters (excluding NGC5466) is essentially the same as that derived by Buonanno, Corsi and Fusi-Pecci (preprint) using a combination of horizontal branch magnitudes and main sequence fitting. However, individual distance moduli differ by typically 0.09 magnitudes. There is no clear correlation of this residual with metallicity.
An EXOSAT Observation of Spectral Variability From the RS CVn Binary AR LAC
Authors: White N.E. , Shaffer R.A. , Parmar A.N. , Horne K. , Culhane J.L. 
Published: July 2016

AbstractThe eclipsing RS CVn system AR Lac (G2IV+K0IV) has been observed continuously for one 2 day binary cycle with the EXOSAT observatory. Below 1 keV a factor of two intensity modulation is seen with a flat bottomed minimum around the time of primary eclipse and a shallow dip preceeding primary eclipse. Above 1 keV, where only emission with temperatures > 107 K would be detected, no orbital modulation or eclipse is seen. This suggests that the > 20 million degree emission comes from a large region, comparable in size to the binary seperation. The modulation in the < 1 keV lightcurve has been modelled by x2 fitting to X-ray bright spots and by using maximum entropy deconvolution. The lower temperature emission is found to orginate in compact regions with a pressure and temperature similar to that of the flaring sun.
X-ray Spectroscopy of the Ultra-soft Transient 4U1543-47
Authors: Woerd H. van der , White N.E. , Kahn S.M. 
Published: July 2016

AbstractThe X-ray transient 4U1543-47 was observed in 1983 by the EXOSAT observatory near the maximum of an outburst. The X-ray spectrum was measured using a gas scintillation proportional counter (GSPC) and a transmission grating spectrometer (TGS). Two emission line features are resolved. A broad (FWHM ~2.7 keV) line at 5.9 keV is detected in the GSPC, which we interprete as a redshifted and broadened iron Kα line. The Une broadening and redshift may arise from either Compton scattering in a cool plasma with small optical depth (τ ≈ 5), or from Doppler and relativistic effects in the vicinity of a compact object. The spectrum below 2 keV, obtained with the TGS, shows evidence for a broad emission line feature at 0.74 keV, which may be an iron L-transition complex. However, we find that such an emission feature could be an artifact caused by an anomalously low interstellar absorption by neutral Oxygen. The continuum emission is extremely soft and is well described by an unsaturated Comptonized spectrum from a very cool plasma (kT = 0.84 keV) with large scattering depth (τ ≈ 27). The continuum spectrum is strikingly similar to that of black hole candidate LMC X-3.
Clusters of Galaxies and the Hot Intracluster Medium
Authors: Jones C. , Forman W. , David L. 
Published: July 2016

AbstractThe luminous material in clusters of galaxies falls primarily into two forms — the visible galaxies and the X-ray emitting intracluster medium. The hot intracluster medium is the major observed baryonic component of clusters with a mass equal to or greater than that of the stellar matter. In this paper we discuss changes in the efficiency of galaxy formation for different clusters and the origin of the intracluster medium.
The Thermal History and Structure of Cometary Nuclei
Authors: Rickman Hans 
Published: July 2016

Abstract.Cometary nuclei are often considered to be the most primitive bodies of the solar system. Thus it is particularly important to find out what structural changes may have been brought about as a result of their thermal evolution. Is there reason to believe that the bulk composition of the nucleus of a present-day short-period comet may differ from that of the original planetesimal in the solar nebula? Apart from the development of a non-volatile surface layer (‘dust mantle’), what further depth-dependent differentiation can we expect in such a nucleus? These are the ultimate questions addressed in this paper, and attention is focused on the two most active stages of thermal evolution: the early planetesimal stage with internal heating basically due to radioactive decay, and the recent or present cometary phase with strong external heating due to insolation of the surface.
Physical Properties of Cometary Dust
Authors: McDonnell J.A.M. , Lamy P.L. , Pankiewicz G.S. 
Published: July 2016

AbstractPrior to the 1986 apparition of comet Halley, all attempts to determine the physical properties of cometary dust were limited to remote observations and the analysis of various particles captured by the Earth’s atmosphere. The in situ measurements made by the three spacecraft that passed within 10,000 km of the nucleus provided the first opportunity to investigate both the full size-range of particles and the complete process of dust production. Information on composition is derived through mass spectra and the scattering and emission of light from the grains, whilst the dynamics of the dust coma can be modeled from the three separate sets of measurements made over a period of eight days.
Chemical Properties of Cometary Dust and A Note on Carbon Isotopes
Authors: Jessberger Elmar K. , Kissel Jochen 
Published: July 2016

AbstractOn board the space probes Giotto and VEGAs and 2, which were sent through the coma of comet Halley, were the mass spectrometers PIA and PUMAs 1 and 2 for the in situ analysis of cometary dust. This paper summarizes the results obtained up to now, about four years after the flybys. It is sought to make the reader aware of the significance, but also of the limitations, of these unprecedented data gathered within a few hundred seconds with an innovative instrument about 1.5 x 108 km away from Earth. The first part of this paper shows how the bulk properties of the dust are derived—the main constituents CHON and silicates, the core-mantle structure, the molecular composition of the organic component, the average composition of the dust and of the whole comet, and the gas/dust ratio. The second part reviews what can safely be said about the properties of the individual grains—their similarity to a certain class of interplanetary dust particles and their distinction from others, and their density and masses. The final part of this paper shows that some cometary grains contain isotopically ultra-light carbon (12C/13C up to 5000), a finding that is significantly substantiated by reports of similar carbon isotopic composition in meteoritic graphite.
Global Fringe Fitting applied to Mk3 VLBI data
Authors: Bååth Lars B. 
Published: July 2016

AbstractA system has been developed where data from a Mk3 VLBI processor can be read into the AlPS-package. Multiband and singleband delays can then be fitted globally by station. The technique has been used to phaserefence a background quasar to two radiogalaxies in the Abell cluster A2634.
Giant Metrewave Radio Telescope (GMRT)
Authors: Swarup Govind 
Published: July 2016

AbstractThe Giant Metrewave Radio Telescope (GMRT) is being set up near Pune in India consisting of 30 numbers of 45-m diameter parabolic dishes. Twelve of these are being placed in a central array, about 1 × 1 km2 in size, and the remaining eighteen along three 14-km long arms forming a Y-shaped array. GMRT will operate at six frequency bands near 38, 153, 233, 327, 611 and 1420 MHz. It is expected to be completed progressively by 1993, and will be the world’s largest radio telescope operating at metre and decimetre wavelengths.
Supergiant Variables: Recent Observational Results
Authors: Percy J. R. 
Published: July 2016

AbstractRecent observations of several types of supergiant variable stars are reviewed: massive blue, yellow and red supergiants; classical and population II Cepheids; RV Tauri stars; yellow semi-regular (SRd) variables, including UU Herculis stars; and R Coronae Borealis stars. The emphasis is on non-linear aspects such as: amplitude and shape of the light and velocity curves; multiperiodicity, irregularity and chaos; long-term changes in period and amplitude; episodic and continuous mass loss.
Variability in Active Galactic Nuclei
Authors: Matsuoka M. 
Published: July 2016

AbstractAGN (Active Galactic Nuclei) have their profound time variability over a wide range of time scales. Although many results of AGN variability have been provided from wide band wavelength observations, I would like to concentrate the recent problems concerning a nearby region of their central engine based on the X-ray observations which are most efficient to investigate this region. In this paper we will investigate mainly the result of Seyfert galaxies which would be generalized to other AGN.
The Coupling Coefficients of Pulsation for Radiative Stellar Models
Authors: Yamakawa F. , Ishida T. , Takeuti M. 
Published: July 2016

AbstractThe second order theory of coupling is discussed regarding the radial pulsation of stellar models which are constructed ignoring convection. The formula including the nonadiabatic effect is presented. Numerical values given for model classical cepheids are considerably greater than the adiabatic values.
Radiation Chemistry Approach to Cometary Chemistry
Authors: Ramos-Bernal Sergio , Negrón-Mendoza Alicia 
Published: July 2016

AbstractThe chemistry of comets is analyzed in the light of radiolytic processes occurring in the life-time of the comet due to its interaction with radiation. A simple model of a cometary nucleus is carried out at the laboratory which simulates as a first approximation the behavior of the organics in the comet. Most of the results obtained confirm that the parent molecules of the observed ones can be deduced from these simple simulated experiments. A variety of molecules were obtained (amino acids, carboxylic acids, gaseous products, etc.), even in frozen solutions the formation of oligomers was observed. The simplified mixture consisted of five compounds in a proportion in which they appear in a dense interstellar cloud (HCN/CH3OH/CH3CN/C2H5CN/HCOOH = 1:0.6:0.2:0.1:0.05). The total amount was adjusted to correspond to a C/N ratio 1.8. At this end, radiation chemistry can be a very precise and useful tool to simulate the evolution of organic molecules exposed to high energy radiation, as cosmic rays, during the life time of a comet.
The Impacts of D/Shoemaker-Levy 9 and Bioastronomy
Authors: A’Hearn Michael F. 
Published: July 2016

AbstractThe impacts of comet D/Shoemaker-Levy 9 into Jupiter provided the first chance to actually observe the effects which may be important in causing mass extinctions. The widely predicted global deposition of dust, leading to the phenomena associated with «nuclear winter», was readily observed, although Jupiter’s internal heat source causes a different response deep in the atmosphere than occurs on Earth. Less widely anticipated, despite recognition that global wildfires occurred during the K-T event on Earth, was the fact that material ejected above the stratosphere fell back onto the stratosphere producing a major heat pulse over a scale of 104km, by far the most easily and widely observed phenomenon during the impacts.
Accretion of the outer Planets and its Influence on the Surface Impact Process of the Terrestrial Planets
Authors: Fernández Julio A. , Ip Wing-H. 
Published: July 2016

AbstractWe study numerically the scattering of residual icy planetesimals towards the terrestrial planets zone during the accumulation of proto-Uranus and proto-Neptune. Our results show that an amount of icy material of severalM⊕(Earth mass) could have reached the terrestrial planets zone in a time scale of a few 108years. An already-formed Earth would have received an amount of about 3 × 1022kg of volatiles (this is about 20 times the amount of water contained in the oceans). Mars would have experienced a similar large volatile injection of about 5 × 1021kg. Yet, it is possible that part of the material injected by the accreting outer planets arrived to the inner planetary region before the terrestrial planets finished to sweep all the massive planetoids of their influence zones. If this was the case, the accreted volatile material would have subsequently been lost in megaimpacts. Moreover, massive icy planetesimals impacting at velocities much greater than the escape velocity might have led to a net erosion of volatile material, rather than accretion. Our numerical results show that the outer planets could have grown to sizes comparable to their current ones in time scales of a few 108years. The tail of residual material injected in the terrestrial planets zone lasted for several 108years, so it might have greatly contributed to the heavy bombardment of the Earth during the period 4.4-3.8 Gyr (before present). The material coming from the outer planetary region might have played a pivotal role in the development of the early atmosphere and life on Earth, though how much volatile material was retained is still an open question whose answer depends on several uncertain parameters.
The Infancy of Solar-Type Stars and its Relevance for the Origin of Life
Authors: Montmerle Thierry 
Published: July 2016

AbstractFor life to develop, planets are a necessary condition. Likewise, for planets to form, stars must be surrounded by circumstellar disks, at least some time during their pre-main sequence evolution. Much progress has been made recently in the study of young solar-like stars. In the optical domain, these stars are known as «T Tauri stars». A significant number show IR excess, and other phenomena indirectly suggesting the presence of circumstellar disks. The current wisdom is that there is an evolutionary sequence from protostars to T Tauri stars. This sequence is characterized by the initial presence of disks, with lifetimes ~ 1-10 Myr after the intial collapse of a dense envelope having given birth to a star. While they are present, about 30% of the disks have masses larger than the minimum solar nebula. Their disappearance may correspond to the growth of dust grains, followed by planetesimal and planet formation, but this is not yet demonstrated.
Detection and Characterization of earth-like Planets
Authors: Mariotti Jean Marie , Léger Alain , Mennesson Bertrand , Ollivier Marc 
Published: July 2016

AbstractIndirect methods of detection of exo-planets (by radial velocity, astrometry, occultations,...) have revealed recently the first cases of exo-planets, and will in the near future expand our knowledge of these systems. They will provide statistical informations on the dynamical parameters: semi-major axis, eccentricities, inclinations,... But the physical nature of these planets will remain mostly unknown. Only for the larger ones (exo-Jupiters), an estimate of the mass will be accessible. To characterize in more details Earth-like exo-planets, direct detection (i.e., direct observation of photons from the planet) is required. This is a much more challenging observational program. The exo-planets are extremely faint with respect to their star: the contrast ratio is about 10−10at visible wavelengths. Also the angular size of the apparent orbit is small, typically 0.1 second of arc. While the first point calls for observations in the infrared (where the contrast goes up to 10−7) and with a coronograph, the latter implies using an interferometer. Several space projects combining these techniques have been recently proposed. They aim at surveying a few hundreds of nearby single solar-like stars in search for Earth-like planets, and at performing a low resolution spectroscopic analysis of their infrared emission in order to reveal the presence in the atmosphere of the planet of CO H2O and O3. The latter is a good tracer of the presence of oxygen which could be, like on our Earth, released by biological activity. Although extremely ambitious, these projects could be realized using space technology either already available or in development for others missions. They could be built and launched during the first decades on the next century.
The Origin of Biological Structures: Information Theory and the Creation of Order. Some New Insights
Authors: Bauer Carlo , Morelli Roberto , Spanedda Andrea , Paolini Moreno 
Published: July 2016

AbstractSome concepts in thermodynamics and information theory are selected for their importance in the study of the spontaneous formation of structures in closed systems at constant temperature and pressure, and are reexamined in order to clarify the origin of the information needed and its dynamics. If there is a spontaneous creation of order in the system (ΔSsys&lt; 0), a generously compensating increase of entropy in the environment (−ΔHsys/T) must be produced. The net decrease of total (or statistical) information (I = −S) in the universe is thus ΔGsys/T, otherwise stated as ΔGsys= −TΔSuniv. Remembering the existence of two types of entropy: geometric and energetic entropy, we explain the spontaneous formation of order with a draft of geometric information by the destruction of a suitable amount of energetic information. Thus the original chaos was a geometric chaos, but rich in energetic information. We propose finally that if there is a variation in the degrees of freedom in the system, due to some quantum restrictions, the ensuing variation of microscopic kinetic energy at constant T must be subtracted from both the enthalpic and entropic terms of ΔG, resulting in a restatement of the conditions of spontaneity which may even be very great. This (ΔEk)Tcorrective term is linked to the difference of heat capacities ΔCp in the process. Biochemical examples are given in the main text.
Homochirality as the Signature of Extra-Terrestrial Life
Authors: MacDermott Alexandra J. , Barron Laurence D. , Brack Andrè , Buhse Thomas , Cronin John R. , Drake Alex F. , Emery Roger J. , Gottarelli Giovanni , Greenberg J Mayo , Haberle Robert , Hegstrom Roger A. , Hobbs Kevin , Jones Brad T. , Kondepudi Dilip K. , Matthews Clifford N. , McKay Christopher P. , Moorbath Stephen , Raulin François , Sandford Michael C.W. , Schwartzman David W. , Thiemann Wolfram , Tranter George E. , Zarnecki John C. 
Published: July 2016

AbstractThe most characteristic hallmark of life is its homochirality: all biomolecules are usually of one hand, e.g. on Earth life uses only L-amino acids for protein synthesis and not their D mirror images. We therefore suggest that a search for extra-terrestrial life can be approached as a Search for Extra- Terrestrial Homochirality (SETH). The natural choice for a SETH instrument is optical rotation, and we describe a novel miniaturized space polarimeter, called the SETH Cigar, which could be used to detect optical rotation as the homochiral signature of life on other planets. Moving parts are avoided by replacing the normal rotating polarizer by multiple fixed polarizers at different angles as in the eye of the bee. We believe that homochirality may be found in the subsurface layers on Mars as a relic of extinct life, and on other solar system bodies as a sign of advanced pre-biotic chemistry. We discuss the chiral GC-MS planned for the Roland lander of the Rosetta mission to a comet and conclude with theories of the physical origin of homochirality.