bluuebunny/crossref_metadata_2025_split huggingface dataset:
Statistics of CP Stars in a Magnitude-Limited Sample: The Bright Star Catalogue
Authors: Schneider H. 
Published: July 2016

AbstractIn the past several authors investigated the incidence of CP Stars among field stars of the upper main sequence, e.g. Jaschek&Jascheck (1967), Wolff (1968), Abt (1979), or in open clusters e.g. Young&Martin (1973), Hartoog (1976), North&Cramer (1981). But the published values seem not to be very precise or universal because of the use of incomplete data bases like Osawa’s list (1965) or the old version of the Bright Star Catalogue or the concentration on selected samples e.g. open clusters. Only Smith (1973) gave realistic values in the case of CP1 stars.In the meantime two decades passed and many new observations were obtained. In 1982 a new version of the Bright Star Catalogue with better spectral classifications was issued and a supplement to the BS catalogue was published (1983). Furthermore, Renson and co-workers presented 1991 their General Catalogue of Am and Ap Stars (in the following abbreviated to GCAAS). Now the moment has come to establish new and hopefully more precise values of the incidence of CP Stars using the new version of the Bright Star Catalogue and its supplement as the data base.
Dissociation Energies and Partition Functions of Small Molecules
Authors: Costes Michel , Naulin Christian 
Published: July 2016

For a simple dissociation equilibriumthe equilibrium constantKpat temperatureTcan be written in terms of partial pressurespor densitiesnin the form given by Equation 6 of Tatum (1966)wheremis the reduced mass of AB,kthe Boltzmann constant,hthe Planck constant,QA,QB,QABthe internal partition functions of the species, andD0the dissociation energy of AB. This equation derives from a more general expression ofKp(T) for a chemical reaction that is demonstrated in all physicalchemistry textbooks treating statistical thermodynamics (see for example Atkins 1990). Partition functions are weighted Boltzmann factorswith ϵncorresponding to the energy of the eigenstates of degeneracygn. Provided all the eigenvalues are known,Qvalues can be calculated exactly. Derivations and calculations of the partition functions can be found in textbooks or in reviews relating to astrophysics.
Computation of Opacities for Diatomic Molecules
Authors: Kurucz Robert L. 
Published: July 2016

In this section I briefly describe my efforts to improve the atomic and molecular line data. This work is described in more detail in Kurucz (1992a). In subsequent sections I briefly describe three methods for computing opacity and the models and spectra that result from using them.My model calculations in the 1970s used the distribution-function line opacity computed by Kurucz (1979a,b) from the line data of Kurucz &amp; Peytremann (1975). We had computedgfvalues for 1.7 million atomic lines for sequences up through nickel using scaled-Thomas-Fermi-Dirac wavefunctions and eigenvectors determined from least squares Slater parameter fits to the observed energy levels. We also collected all published data ong fvalues and included them in the line list whenever they appeared to be more reliable than the computed data (that work is ongoing, but I am running behind).
The MORBID Method
Authors: Jensen Per 
Published: July 2016

The present communication is concerned with the problem of calculating the rotation-vibration energies and the absorption intensities of a triatomic molecule from the effective nuclear potential energy function and the dipole moment surfaces within the Born-Oppenheimer approximation (Born &amp; Oppenheimer 1927). There are at least two astrophysical applications of such calculations:— Detailed spectra of triatomic molecules can be computed under the conditions prevailing in stellar atmospheres and compared with observed spectra.— Such spectra can also be used for constructing a wavenumber-dependent absorption coefficient which can be employed for opacity calculations as outlined, for example, by Jørgensen &amp; Jensen (1993).
The Use of CCDs on Schmidt Telescopes
Authors: Armandroff Taft E. 
Published: July 2016

AbstractThe implementation of CCDs on Schmidt telescopes is discussed, including the capabilities of such systems and the new types of observations that they facilitate. An analysis of the demand for and use of the CCD system on the Burrell Schmidt is presented. Some examples of scientific investigations accomplished with Schmidt CCD systems are given. The future evolution of CCD capabilities on Schmidt telescopes is discussed.
A Southern Sky Survey of Low Mass Stars and Brown Dwarfs
Authors: Thackrah Andrew D. , Hawkins Michael R. S. 
Published: July 2016

AbstractWe are conducting a survey of the southern sky to study the properties of the lowest mass stars and the sub-stellar brown dwarf population thought to exist at masses below 0.08 M⊙. The survey makes use of plates from the UK and ESO Schmidt telescopes, using the new SuperCOSMOS plate measuring machine at Edinburgh to provide a catalogue of photographic BRI colours and proper motion measurements. Candidates are selected by extreme R–I colour (> 2.5) to a plate-limited magnitude of I ≈ 19.0 and R ≈ 21.0. The size of the survey is only limited by the progress of the UK Schmidt I band survey and the availability of photometric data for calibration of SuperCOSMOS measurements. It is anticipated that the survey will form part of a multi-colour proper motion database of southern sky objects.
Why We Need a Deep Spectral Survey of the Milky Way
Authors: Kurtanidze Omar M. , Nikolashvili Miriam G. 
Published: July 2016

AbstractIn this short review we briefly discuss all the extensive low dispersion objective-prism spectral surveys carried out in the last fifty years for the study of the surface and space distributions of late-type giant stars, namely C stars. In the light of data obtained and new discoveries, the expediency of undertaking a deep mI low dispersion spectral survey in the near-infrared spectral region is considered.
The Star Forming Regions of Orion
Authors: Kogure Tomokazu 
Published: July 2016

AbstractThe distribution of emission line stars in Orion is presented, based on our recent surveys and other previous ones. Particular attention is given for the central 10 × 10 square degrees to compare some properties of emission line stars and OB association stars. As a result, a possibility of bimodal star formation is suggested in this region.
Survey Catalogues of Kiso Ultraviolet-Excess Galaxies
Authors: Miyauchi-Isobe Nagako , Takase Bunshiro , Okamura Sadanori 
Published: July 2016

AbstractOur survey for KUGs (Kiso Ultraviolet-excess Galaxies) is based on the multi-colour method applied to photographic plates taken with the Kiso Schmidt telescope. In total, 8,968 KUGs were detected on 170 plates covering some 5,100 square degrees. They are listed in 17 separate catalogues, where morphological type and UV-excess degree are given for each object together with position, size, and magnitude. After the appropriate editing of multiple entries of the same object detected on different plates, we produced a merged catalogue where 8,162 KUGs were arranged in order of right ascension. The accuracy of the position of KUGs was examined using the data of 806 KUGs whose positions were measured on different plates.
The UNAM Scanning Fabry-Perot Interferometer (PUMA) for the Study of the Interstellar Medium
Authors: Angeles F. , Bernal A. , Cobos F. , Garfias F. , Gutiérrez L. , Langarica R. , Rosado M. , Tejada C. , Tinoco S. 
Published: July 2016

AbstractWe describe recent advances in the development of a scanning Fabry-Perot interferometer applied to the study of the kinematics of the interstellar medium at the Observatorio Astronómico Nacional at San Pedro Mártir, B.C. México.
High Resolution Studies of Molecular Hydrogen by Means of Near-Infrared Fabry-Perot Imaging
Authors: Chrysostomou Antonio , Burton Michael , Axon David , Brand Peter , Hough James , Bland-Hawthorn Joss , Geballe Tom 
Published: July 2016

AbstractWe present a study of the velocity profiles of the v=l-0 S(1) transition of molecular hydrogen (H2) towards the star forming region of OMC-1. A three dimensional data cube is presented which displays the spatial distribution as well as the velocity structure of the H2 emission. A brief description of the data acquisition, reduction and analysis is given.The three dimensional aspect of the data has allowed us to re-examine the kinematic nature of the region. The results reveal a number of isolated sources which posses asymmetric velocity profiles which can be modelled by bow C-shocks. The implication is that these sources are compact knots of material which were involved in some explosive event, possibly associated with the luminous source IRc2, and are ploughing into the dense molecular disk around IRc2. It is likely that these bullets are associated with those discovered by Allen & Burton (1993).
3-Dimensional High-Resolution Solar Spectro-Polarimetry
Authors: Volkmer Reiner 
Published: July 2016

AbstractIn order to obtain information on the magnetic field on the sun in two spatial dimensions, a spectro-polarimeter of high spatial, spectral, and temporal resolution was built in the German Vacuum Tower Telescope (VTT) at the Observatorio del Teide/Tenerife. The two-dimensional spectrometer in the VTT, using a Universal Birefringent Filter (UBF) and a Fabry-Perot Interferometer (FPI) to obtain narrow-band nltergrams with a spectral resolution of the order of 3.105 (approx. 22 mÅ at CE5; at 6303 Å) and a spatial resolution of 0.2 arcsec/pixel (Bendlin et al. 1992, Bendlin and Volkmer 1993), was extended to work as a spectropolarimeter for measuring Stokes-I and Stokes-V profiles.
Stellar dynamics of galactic nuclei with TIGER
Authors: Emsellem Eric , Bacon Roland , Monnet Guy 
Published: July 2016

AbstractWe conducted an observational program using the TIGER integral field spectrograph to study the dynamical structure of nearby galactic nuclei. We already obtained new original results on three of the best ”Black Holes Candidates”: M 32, M 31 and M 104. Their nuclei exhibit complex morphologies and unusual dynamical properties such as: asymmetries, anisotropy, triaxiality which would have been impossible to detect with a ”classical“ spectrograph.
A comparison of Imaging Fourier Transform with Grating Spectrometry for Tridimensional Spectroscopy
Authors: Smith Peter L. , Thorne Anne P. , Parkinson W. H. 
Published: July 2016

AbstractWe compare the relative merits of four different types of instrument for tridimensional spectrometry at visible and ultraviolet wavelengths: the echelle and long-slit spectrographs and two types of Fourier transform spectrometer (conventional scanning and fixed tilt spatially heterodyned). Each of these instruments requires different spatial and spectral scanning modes. It is shown that in certain limiting conditions all four are equally efficient, but that they differ in other important characteristics.
Distance and Chemical Composition of High-Velocity Clouds
Authors: van Woerden Hugo , Schwarz Ulrich J. , Wakker Bart P. 
Published: July 2016

AbstractThis contribution reports results of recent absorption-line studies on La Palma and reviews earlier work done elsewhere. CaII has been found in absorption in five HVCs, mostly against extragalactic background sources. The CaII/HI ratios differ strongly, from 0.002 to 0.1 times solar, suggesting different origins of HVCs. Nondetections of CaII absorption in stellar spectra may provide lower limits to HVC distances, or be caused by small-scale structure or a low CaII/HI ratio in the HVC. Proper interpretation requires comparison of CaII/HI ratios in stellar and extragalactic probes, and use of high-resolution HI maps. No solid direct distance determinations of HVCs are available yet. The distance of Complex C is controversial.
Observations of Global Solar Magnetic and Velocity Fields
Authors: Hoeksema J. Todd 
Published: July 2016

The Sun’s magnetic field varies on time scales of minutes, months, decades, and centuries. These changes drive variations in solar irradiance. Characteristics of the changing magnetic field reveal, at some level, how the solar cycle works. The basic 22-year magnetic cycle and corresponding 11-year activity cycle of the Sun are driven by the emergence of active regions. The frequencies of solar oscillations that probe the convection zone vaxy on the same time scale. While plausible explanations for the statistical properties of solar activity can be made, the details of flux emergence cannot be predicted. Global activity varies on other intermediate time scales as well.Defining elements of a cycle as those sharing a common bipolar field orientation, the first signs of a cycle can appear at high latitudes up to 5 years before solar minimum and the final elements disappear at the equator several years after the following minimum - a span as long as 18 years. At a particular latitude waves of activity are spaced by 11 years. The torsional oscillation in solar rotation rate has similar characteristics.The spatial distributions of total flux and large-scale polarity evolve quite differently: the total flux map resembles the butterfly diagram, moving from mid latitudes toward the equator during the cycle, while the net zonal flux has two maxima in each hemisphere that expand away from mid latitudes.While each solar cycle shares these basic features, fixed by the action of the solar dynamo working within the convection zone, the details of each cycle are determined by the apparently random timing and placement of emerging flux and by the changing convective flow patterns.
General Structure of the X-ray Corona
Authors: Acton L. W. 
Published: July 2016

AbstractX-ray images have revealed the corona to comprise four basic morphologies. In order of X-ray luminosity these structures are: (1) Bright, relatively short, X-ray loops in active regions, (2) Less bright and larger X-ray structures of the so-called quiet corona, (3) X-ray bright points, and (4) Coronal holes. The soft X-ray telescope (SXT) onYohkohprovides good angular resolution with much improved time resolution and continuity of coverage as compared to the earlier observations. In the SXT movies these structures often appear to be interacting and change appearance on time scales from seconds to weeks. Flare, flare-like, and eruptive processes continuously alter the general structure of the corona. This paper will comment on the structure, changes and heating of the X-ray corona as revealed by theYohkohobservations.
The Mass Ejection Event of 1986 May 4 and the Associated Phenomena
Authors: Garczyńska I. N. , Rompolt B. , Aurass H. , Burkepile J. T. , Cader-Sroka B. , Chertok I. M. 
Published: July 2016

AbstractA sequence of structural changes in the low and high corona observed in Hαand white light is investigated in details. Relatively slow Hαmass ejections have been accompanied by X-ray and radio bursts as well as CME. Some interconnections between all these events are analysed.
Very Large Array Observations of Large-Scale Coronal Structures
Authors: Lang K. R. 
Published: July 2016

AbstractVery Large Array (VLA) observations indicate that electrons accelerated in one active region can travel along otherwise-invisible, large-scale coronal loops to trigger flares in another widely-separated active region, as well as from the magnetic loops connecting them. The VLA provides high-resolution, full-disk images of quiescent, or non-flaring, coronal loops within individual active regions (at 20 cm) and between or beyond them (at 90 cm). Both ground-based radio telescopes and spaceborne X-ray telescopes provide high-resolution images of the ubiquitous coronal loops whose hot, dense magnetically-trapped plasma emits thermal bremsstrahlung. Radio observations can be used to specify the strength and structure of the magnetic fields in the low solar corona. We find a high magnetic field strength in the million-degree plasma above large sunspots – 75 to 80 percent of the value in the underlying photospheric sunspots; as well as coronal regions of non-potential, current-amplified magnetic fields. Some long-lasting (hours) coronal radio sources found on the Sun and other active stars require nonthermal radiation and nearly continuous acceleration of energetic electrons.
Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak
Authors: Minarovjech M. , Rybanský M. 
Published: July 2016

AbstractThis paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:1.heating of the solar corona2.course of the global cycle in the corona3.rotation of the solar corona and development of active regions.There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.
Theoretical Correlations Between Various Prominence Parameters
Authors: Heinzel P. , Gouttebroze P. , Vial J.-C. 
Published: July 2016

AbstractStarting from our extensive numerical modeling of the NLTE conditions in solar prominences, we present here some examples of important correlations between the prominence plasma parameters and radiation properties. For example, the plasma emission measure was found to be closely related to the integrated Hα line intensity which provides a new diagnostic tool for determination of plasma densities.
The Diamagnetic Effect: Misconception about Its Vanishing Average
Authors: Steinitz R. 
Published: July 2016

AbstractIt has been argued in the past that while the diamagnetic effect (DME) is well apparent for single particles (i.e. motion of charged particles in the Earth’s ionosphere), it is not relevant for fluid descriptions of plamas.In this paper we show that this is a misconception due to a wrong averaging procedure. Taking the DME into account, we obtain speed filters which function as heat and momentum pumps, resulting in cool sunspots, a hot corona and solar winds.
MHD Spectrum of Coronal Rays
Authors: Matsuura O. T. , Shigueoka H. , Azevedo C. A. , Lavras W. O. 
Published: July 2016

AbstractThe MHD spectrum of discrete kink modes is derived for a cylindrical, static and isothermal plasma with spatial variations in radial direction only. Such a configuration models, in first approximation, the long and almost radially oriented fine structures of the solar corona denominatedcoronal rays, whenever cylindrical symmetry holds. Since here gravity is not taken into account, the application of the results is limited to longitudinal wavelengths not greater than the density scale of height. The predicted eigenfrequencies of slow magnetoacoustic modes are potentially observable in eclipses and may constitute a diagnostics of the axial electric current and the degree of twisting of the magnetic field.
On the Optical Polarization of the White-Light Coronal Structures
Authors: Filippov B. P. , Molodensky M. M. , Koutchmy S. 
Published: July 2016

AbstractA special experiment was designed to measure the orientation of the polarization plane in the solar corona during the total eclipse of July 11, 1991. Rotating polaroids with the axes directed at +45° and at −45° of the radial direction in all directions were used. The polarization plane was found to be tangential to the solar limb everywhere with an accuracy within 1°, in agreement with the Thomson scattering theory.
Gravitational Collapse versus Thermonuclear Explosion of Degenerate Stellar Cores
Authors: Isern J. , Canal R. 
Published: July 2016

AbstractIn this paper we review the behavior of growing stellar degenerate cores. It is shown that ONeMg white dwarfs and cold CO white dwarfs can collapse to form a neutron star. This collapse is completely silent since the total amount of radioactive elements that are expelled is very small and a burst of γ-rays is never produced. In the case of an explosion (always carbonoxygen cores), the outcome fits quite well the observed properties of Type Ia supernovae. Nevertheless, the light curves and the velocities measured at maximum are very homogeneous and the diversity introduced by igniting at different densities is not enough to account for the most extreme cases observed. It is also shown that a promising way out of this problem could be the He-induced detonation of white dwarfs with different masses. Finally, we outline that the location of the border line which separetes explosion from collapse strongly depends on the input physics adopted.
Neutron Star Crusts With Magnetic Fields
Authors: Yakovlev D.G. , Kaminker A.D. 
Published: July 2016

AbstractThe properties of plasma in neutron star crusts with strong magnetic fields B = 1010 − 1013 G are reviewed: thermodynamic properties (equation of state, entropy, specific heat), transport properties (electron thermal and electrical conductivity of degenerate electron gas, radiative thermal conductivity of very surface nondegenerate layers) and neutrino energy losses. Classical effects of electron Larmor rotation in a magnetic field are considered as well as quantum effects of the electron motion (Landau levels). The influence of the magnetic fields on density and temperature profiles in the surface layers of neutron stars and on neutron star cooling is briefly discussed.
The Equation of State of Fluid Hydrogen at High Density
Authors: Chabrier G. 
Published: July 2016

AbstractWe present a free energy model for fluid hydrogen at high-density and high-temperature. This model aims at describing pressure dissociation and ionization, which occur in partially ionized plasmas encountered in the interiors of giant planets and low-mass stars. The model describes an interacting mixture of H2, H, H+ and e− in chemical equilibrium. The concentrations of H2+ and H− ions are found to be negligible for equation of state purposes. Our model relies on the so-called chemical picture approach, based on the factorization of the partition function into translational, internal and configurational degrees of freedom. The present model is found to be unstable in the pressure-ionization regime and predicts the existence of a first-order plasma phase transition (PPT) which ends up at a critical point given by Tc = 15300 K, Pc = 0.614 Mbar, and ρc = 0.35 gem−3. The transition occurs between a weakly ionized phase and a partially ionized (~ 50%) phase.
White Dwarf Seismology: Influence of the Constitutive Physics on the Period Spectra
Authors: Fontaine G. , Brassard P. 
Published: July 2016

AbstractWe present the results of numerical experiments aimed at demonstrating how theg-mode period spectra of pulsating DA white dwarfs depend on the various components of the input physics. We take advantage of recent developments on many fronts of physics (equation of state, opacity, convection) to compare the theoretical pulsation periods of models with different pieces of the constitutive physics, but with otherwise fixed values of their stellar parameters. This exercise is necessary to assess the reliability of the pulsation analyses of white dwarfs which have started to come out.
Helioseismology: the Sun as a Strongly-Constrained, Weakly-Coupled Plasma
Authors: Däppen W. 
Published: July 2016

AbstractAccurate measurements of observed frequencies of solar oscillations are providing a wealth of data on the properties of the solar interior. The frequencies depend on the solar structure, and on the properties of the plasma in the Sun. Except in the very outer layers, the stratification of the convection zone is almost adiabatic. There, the sound-speed profile is governed principally by the specific entropy, the (homogenous) chemical composition and the equation of state. It is therefore essentially independent of the uncertainties in the radiative opacities. The sensitivity of the observed frequencies is such that it enables to distinguish rather subtle features of the equation of state. An example is the signature of the heavy elements in the equation of state. This opens the possibility to use the Sun as a laboratory for thermodynamic properties.