bluuebunny/crossref_metadata_2025_split huggingface dataset:
Realization of the Local Inertial Geocentric Frame in Relativity
Authors: Miao-Fu He , Cheng Huang 
Published: July 2016

There are two kinds of geocentric frames: local inertial and non-inertial geocentric frames. Ashby et al successfully constructed a local inertial geocentric frame in the neighborhood of the gravitating Earth. In the frame with origin at the Earth's center, the gravitational effects of the sun and of planets other than the Earth are basically reduced to their tidal forces, with very small relativistic corrections.However, the spatial base vectors of the local inertial frame essentially experience the geodesic (or deSitter) precession with respect to the solar system barycentric frame. Hence the realization of the local inertial frame requires that the general precession should exclude the geodesic precession. This requirement is inconsistent with the convention that the amount of geodesic precession is included in that of the general precession given by Lieske et al.
Astrometry With the Tautenburg Schmidt Telescope
Authors: Steinert K.-G. 
Published: July 2016

The realization of an optimum astronomical reference frame depends on well-defined connection between the systems of optical and radio positions of objects. For this the physics of radio objects are to be studied carefully. Besides this it is necessary to investigate how to get accurate positions of the optical counterparts of these objects as benchmarks for establishing a radio-optical reference frame. As the optical sources are very faint, photographic telescopes with robust light-gathering power are to be used.For 15 years research work has been done using plates of the 134/200/400 Tautenburg Schmidt telescope for determinations of photographic positions of stars and extragalactic objects. An overview of some special results obtained at Dresden Lohrmann Observatory and Potsdam Central Institute of Astrophysics of the GDR Academy of Sciences will be given.
CCD Parallaxes for Faint Southern High Proper Motion Stars
Authors: Anguita C.A. , Ruiz M.T. 
Published: July 2016

In April 1985, we started a program to measure trigonometric parallaxes for faint southern high proper motion stars, using a CCD at the Cassegrain focus of the Cerro Tololo Interamerican Observatory (CTIO) 1.5-m telescope. The program stars (mR > 16; μ ≥ 1 arcsec/year) were selected from the LHS Catalogue and the University of Chile proper motion program.The X and Y positions of the stellar image centroids were obtained using the algorithms of DAOPHOT program packages. The precision of the measurement of one stellar image is about 6 milliarcseconds (0.02 pix). For stars with 16 < mR < 19.5 a precision of 2 milliarcseconds in the parallax determination can be obtained in a one year period. Trigonometric parallaxes for some stars common to other parallax programs are given, showing an agreement with those results within the quoted mean errors.Several technical aspects of the present program are also discussed.
An Astrometric Catalog of Four Million Stars
Authors: Nesterov V. V. , Kisliuk V. S. , Potter H. I. 
Published: July 2016

The goal of the present study is
(1)Completion of a general reduction of the Carte du Ciel astrophotographic catalogs, measurement of the positions in them on modern astronegatives, derivation of proper motions and compilation of a catalog of stars to magnitude 12.5.(2)Copying the data of all 272 volumes of astrophotographic catalogues onto magnetic tapes (all together 8.5 million measurements).(3)Measurement of modern astronegatives on FON-OBZOR-S and FOKAT-Y programs.(4)Studies of the magnitude equation of the AGK3 catalog and other catalogs which will be presumably used as reference catalogs.(5)Development and comparative studies of several methods of determination of equatorial coordinates on the basis of full information on astronegative measurements. Application of these methods to compilation of the catalog of 4 million stars.
Modernization of Chinese Photoelectric Astrolabes and Improvement of Optical Reference System
Authors: Dong-Ming Li , Hong-Qi Wang , Gang Zhao , Ze-Zhi Wang , Rui Wang 
Published: July 2016

The features of the astrolabe are that:(1) a span of 6 hour of R.A. of star positions can be tied in a group of observation of 2 hours, all-night observation can cover more than half of the sky, and(2) the declination system can be set up with high precision without the need of a precise circle (Li 1987).
A Search for Main-Sequence Binaries in Globular Clusters
Authors: Liller Martha H. 
Published: July 2016

It is becoming increasingly clear that no (or only one or two) binaries occur among the evolved stars in globular clusters. Therefore, if binaries exist at all in these systems, they must be found on or near the main sequence. I have chosen 6 clusters to search for faint eclipsing binaries by the following criteria:
(1)the apparent visual distance modulus (Harris 1976) (m-M)V ≤ 14.5 mag;(2)the Peterson and King (1975) concentration class c ≤ 1.5, so that the search can be conducted near or at the cluster center where binaries would most likely be found; and(3)the galactic latitude is sufficiently large to avoid problems of extreme contamination by field stars.
The clusters thus chosen are NGC3201, 5139 (Omega Cen), 6121 (M4), 6218 (M12), 6254 (M10), and 6809 (M55). The plate material obtained on three nights with the 4-m telescope at CTIO in 1979, consists of seven to nine plates of each cluster on IIIa-F emulsion with an RG610 filter; the search is being conducted with a blink microscope.
Optical Observations of Pulsars
Authors: Smith F. Graham 
Published: July 2016

Optical identification of radio pulsars has only been achieved for the Crab and Vela Pulsars. The luminosity limits for others could be considerably improved: better astrometry and time-resolved photometry could reach mv = 27. The limits for pulsars with unknown periods, for example in extragalactic nebulae, are usually about mv = 20. The luminosity falls rapidly with increasing period: if it follows a power law the index is minus ten at least.The optical spectrum of the Crab Pulsar falls toward the infra-red and is flat in the ultra-violet. No self-absorption effect is seen in the infra-red. New observations of the minimum intensity and of the polarisation show a highly linearly polarised component continuing through the whole pulse cycle.
9. New Spectroscopic Results on Subluminous Stars, V
Authors: Greenstein J. L. 
Published: July 2016

Determination of temperature and surface gravity by colors and hydrogen-line profiles have been carried out for hot halo stars. A narrow horizontal branch is found stretching to above 40000 K; the hot O subdwarfs show a nearly vertical sequence, dropping towards the hot white dwarfs.Spectra for 285 white dwarf stars have been obtained, and the classification scheme is reviewed. Theoretical problems of these spectra remain, largely, unsolved.The red subluminous stars found by Eggen were studied spectroscopically; among 68 stars only one new red degenerate star was found. The others are very metal-poor, high-velocity stars with large ultraviolet excess.
An Explanation of the Polar Motion by a Rigid Core-Mantle Model
Authors: Kubo Yoshio 
Published: July 2016

The Earth with a rigid core and a rigid mantle is considered and a recovering force is assumed between the constituents.The equations of motion in canonical form are derived in terms of the Andoyer's variables. Applying the perturbation theory, the phenomenon of the polar motion is investigated.The polar motion obtained with this model is a circular motion of the rotational axis on the mantle's surface with its radius gradually changing.
Kimura's Z-Term and the Liquid Core Theory
Authors: Wako Yasujiro 
Published: July 2016

Kimura (1902) pointed out that there might be an unknown cause other than polar motion which would produce an apparent latitude variation, and introduced the Z-term as, Δϕ = Xcos λ + + Ysin λ + Z.The theoretical results by Jeffreys-Vicente (1957) and Molodensky (1961) have shown that the effect of a liquid core of the Earth may increase the coefficients of the semi-annual solar nutation term (2 ⊙) which is involved in the diurnal nutation (the so-called Oppolzer term) by 0″.02. It is reasonable to accept this correction which will appear in the Z-term with an argument of (2 ⊙ −α).From comparison of the observed amplitudes and the phase angles of the annual Z-terms derived from the ILS data, it is concluded that the argument of the principal annual term in Z is (2 ⊙ −α) and not ⊙. The following results were obtained for the annual Z-term for 1955-1966 from the analysis of data by two independent methods (Wako, 1970): 0″.0137 sin (2 ⊙ −α + 2°.2), 0″.0203 sin (2 ⊙ −α + 4°.3).Melchior (1970) proposed another effect of the Earth's liquid core for the annual nutation in obliquity, thus a term such as a sin (⊙ +α + A) would appear in the Z-term and it might cause a part of semi-annual Z-term. For the determination of these corrections, analysis of Kimura's Z-term is the most effective method.
Photometric Investigation of IC 2944
Authors: Ardeberg A. , Maurice E. , Rickard J. 
Published: July 2016

An investigation has been made of the central region of the cluster IC 2944. For about 70 stars UBV photometry has been made. For the brighter of those stars also Hβ has been measured. Slit spectra of intermediate dispersion (73 Å mm-1) have been made for the 40 brightest stars. Coudé spectra (12 Å mm-1) have been obtained for 8 stars. Fabry-Pérot measurements have been made in 5 points within the nebulosity. The number of blue stars is shown to be extremely high. Down to visual magnitude 11.5 the cluster seems to contain only O and B stars, the majority of spectral class earlier than B3. The Fabry-Pérot measurements give evidence of high internal gas motion. Evidently the gas is thin, visible only because of the great number of hot stars.Details will be published elsewhere.
Models for Compact Pulsing X-Ray Sources
Authors: Ostriker Jeremiah P. , Davidson Kris 
Published: July 2016

Cen X-3 is probably a neutron star, releasing the infall energy of accreted matter. Sufficient material for accretion will be provided by a conventional stellar wind from its more massive companion star. That star is not likely to rotate synchronously; therefore a ‘Roche lobe’ analysis of the eclipses is not valid. A ‘tidal lobe’ analysis allows the neutron star to have a mass of the order of one solar mass. Overflow of the ‘Roche lobe’ is neither necessary as a source of mass nor probable in view of the observed stellar line widths of the two identified X-ray companions.The mass flow onto the condensed star is very small in all cases. It is limited, for an object of m solar masses by the Eddington Limiting Luminosity to Ṁac < 10–7.4m(M⊙ yr−1), which limit applies even if the accreting object contacts or traverses its companion star.The observed 4.84 s rotation period of the Cen X-3 neutron star is very simply explained as the critical value where a centrifugal barrier regulates the rate of infall to the surface. The X-ray spectrum is understood as blackbody radiation coming from a well-defined area near each magnetic pole of the neutron star.
The Properties of Extragalactic X-Ray Sources from Visible Light Observations
Authors: Sargent Wallace L. W. 
Published: July 2016

We describe the optical properties of the radio galaxy NGC 5128, the Seyfert galaxy NGC 4151 and the QSO 3C 273 all of which appear to be point sources of X-rays. We emphasize how the X-ray observations, particularly the low energy absorption cutoff, may help us to understand the detailed structure and source of energy in these diverse objects.The clusters of galaxies in Virgo, Perseus, Coma and Centaurus, all associated with extended X-ray sources are described. They have diverse shapes, central concentrations and galactic populations, but all contain a radio galaxy and, in several cases, a low frequency radio halo around it. It is concluded that the X-ray emission is likely to be non-thermal in origin.
Radio observations of interstellar molecules
Authors: Robinson B. J. 
Published: July 2016

Investigations of the 18-cm lines of the16O1H radical are still in an exploratory phase. The detection of the strongest line of the18O1H radical has just been reported. Searches for the microwave lines of CH and SiH are in progress.OH absorption has been observed for a few of the stronger radio sources, for a dozen galactic H 11 regions and for the source complex at the galactic centre. The ratio τOH/τHvaries by three orders of magnitude between these sources. In most cases the intensity ratios for the four OH lines are anomalous, which indicates that the populations of the energy levels are perturbed.No thermal emission from OH has been found, even where τ ≈ 1. It thus becomes exceedingly difficult to estimate excitation temperatures and to derive surface densities.Strong non-thermal emission is seen from about a third of the H 11 regions observed. The line profiles are composed of many narrow spikes, quite different for each of the four lines. The intensity ratios of the emission peaks are highly anomalous. The OH emission comes from exceedingly small areas (&lt; 0·1 pc) on theedgeof the ionized regions, with brightness temperatures higher than 106°K.It has been suggested that the populations are inverted. Maser amplification of the background continuum then occurs. Power gains of 104to 105are required. To produce such a gain in a very small region would require high OH densities and a considerable degree of population inversion.In at least eight sources the emission is highly polarized. Complete circular polarization is common, and the sense varies rapidly between adjacent spikes in the profile. The observed polarization is incompatible with Zeeman multiplets.
Theories of spiral structure*
Authors: Prendergast K. H. 
Published: July 2016

This will be rather an unusual introductory talk: I have no slides, almost no equations, and I will not be talking about my own work. I am supposed to speak about the theories of spiral structure, and I will have to begin by redoing some quite ancient considerations.Obviously the first thing that has to be decided is: what is a spiral arm? I am not going to attempt to answer this, but I would like to point out that one can split opinions to a certain extent between those people who would like to think of spiral arms as largescale coherent structures, extending almost from the nucleus to the edge of the Galaxy, and those who would like to think of spiral structure as a combination of many detached features (Figure 1), where the structures that one can really follow do not extend over a considerable fraction of the radius of the Galaxy. For the most part I shall be speaking about people who attempt to explain something by the first picture.
The ultraviolet background (intergalactic gas, the Galaxy, and subcosmic rays)
Authors: Kurt V. G. , Sunyaev R. A. 
Published: July 2016

(1)Observations. – A survey is made of observations of the background radiation at UV wavelengths from above the atmosphere. Sources of the background radiation and ways of determining the extragalactic component of the background are discussed. Future observations are also discussed.(2)Cosmology. – Limits to the properties of the intergalactic gas follow from observations of the UV background. The problem of detecting galaxies at early stages in their evolution is considered.(3)The Galaxy. – Observations and theoretical estimates are given for the integrated brightness of the Galaxy at UV wavelengths beyond the Lyman-α line. Also discussed are the nature of the Lyman-α emission from the Milky Way and the principal ways of constructing the luminosity function of stars in the Galaxy from observations of the integrated UV spectrum.(4)Subcosmic Rays in the Interstellar Medium. – Fast neutral excited hydrogen atoms can be formed from charge-exchange interactions between subcosmic-ray protons and neutral interstellar gas. Upper limits are given to the energy density of subcosmic rays having E ~ 100 keV.(5)Limits on the Background Radiation in the range <912 Å. – The distribution of neutral hydrogen in the peripheries of galaxies allows limits to be obtained for the flux of metagalactic ionising radiation. The heating and ionisation of the interstellar medium by X-rays is considered.
Water on Venus?
Authors: Libby W. F. , Corneil P. 
Published: July 2016

It is proposed that Venus may have polar seas which are acidic and thus cannot precipitate calcium carbonate. This leaves the carbon dioxide in the atmosphere. The argument is that the great equatorial land masses always have been too hot for liquid water and thus could not be weathered to give the sea salts necessary to form the precipitate. The action of steam on rocks is to liberate acids which are volatile and would dissolve in the polar seas. The volcanic vapors issuing in the early times consisting mainly of water and carbon dioxide would have begun polar seas at once since the expected equatorial (black body) surface temperature of the bare planet is too high (464 K) due to proximity of the sun. The accumulation of carbon dioxide in the atmosphere would have ensured the continued increase of the temperature due to the greenhouse effect. On earth, on the contrary, condensation over most of the planetary surface probably was possible from the beginning. Liquid water, ice-weathering, and river transport of salts to the seas all probably occurred from the beginning.As the pressure at the surface probably approximates 100 atm (Venera 5 and 6) we can expect the polar seas to be below the boiling point although possibly hot. An isothermal layer of some thickness is naturally established over liquid water heated by infrared from above. Evaporation and condensation to form rain constitutes an efficient heat transport mechanism. Such a layer naturally would move toward lower latitude carrying moisture which then will rise and eventually move poleward in the high atmosphere causing rain and possibly the planet wide cloud cover. The atmosphere containing volatiles such as hydrochloric and hydrofluoric and sulfurous and sulfuric acids as well as carbon dioxide will form clouds which might be expected to consist of concentrated acid solutions. The main rain over the poles probably falls from altitudes well below the cloud top seen from earth. It is possible that the Venus clouds seen from earth are non aqueous just as our stratosphere carries dust clouds apparently of ammonium sulfate. At the moment it is very difficult to decide between these alternatives.In the more polar regions the seas might conceivably be as cool as 50 °C.
A Gas Proportional Chamber for use in Cosmic X-Ray Research
Authors: Serlemitsos P. 
Published: July 2016

Multi-anode gas proportional counters, when used in cosmic X-ray research, offer several advantages over more conventional large area detectors. Some of these are:1.Low detector background, effected by excluding from the sensitive volume, areas in the proximity of the counter walls, and by requiring that the region of interaction is localized inside the counter.2.Uniform response which makes possible energy resolution limited primarily by the statistics on the number of electron-ion pairs in the interaction, rather than by partial charge collection due to weak field regions inside the counter.3.Information relating to the interaction depth within the gas, which may be used in applying consistency checks regarding the nature of the incident radiation.Methods have been devised for the modular construction of such counters, with particular emphasis on such items as, large areas, ease of assembly, matching of the many counter modules, accurate collimation, window supports, and shape integrity under differing amounts of differential pressure. Detector background at rocket altitudes was found to be flat above 2 keV, and less than 10−3 cm−2 s −1keV−1.
A Tunable Birefringent Filter for the UV Region
Authors: Fredga Kerstin , Högbom J. A. 
Published: July 2016

In the near ultraviolet part of the spectrum filters with narrow bandpasses (smaller than a few Ångströms) are difficult to manufacture. Ordinary birefringent filters suffer from low transmission because of the great number of polarizers usually needed. From this point of view the Šolc-type birefringent filter offers a solution since it only employs two polarizers. With a suitable arrangement of the angles of the optic axes of the birefringent plates adjacent secondary maxima can be suppressed to any desired value.It is shown that by modulating the distribution of the angles by a cosine function a normal transmission peak may be split into two peaks. The distance of the two peaks depends on the frequency of the modulation function. In this manner the filter can easily be tuned over half the free spectral range without appreciable change of the transmission profile. The theoretical results have been experimentally verified.
Solutions of Some High Potential Problems in Rocket Experiments
Authors: Hessberg H. , Niekerke J. 
Published: July 2016

Corona-problems severely can effect absolute calibrated photomultiplier-experiments in sounding rockets. Solutions in case of experiment R-130 (absolute spectral photometry of B-stars in the vacuum UV-region) are presented.(To be published in Raumfahrtforschung, Berlin/Stuttgart/München.)
The VLT Interferometer
Authors: Bedding T. R. , Beckers J. M. , Faucherre M. , Hubin N. , Koehler B. , von der Lühe O. , Merkle F. , Zhu N. 
Published: July 2016

One of the observing modes available with the ESO Very Large Telescope will be coherent combination of the light received by up to four 8 m unit telescopes and several 1.8 m auxiliary telescopes. The location of the main telescopes is fixed, while auxiliary telescopes can be moved among some 30 observing stations. The locations of these stations were chosen to augment the (u, v) coverage of the unit telescopes as well as to function as an independent interferometric array.The 8 m telescopes will be equipped with adaptive optics to correct for seeing-induced wavefront aberrations. This wavefront correction will be complete at near-infrared wavelengths, giving the interferometer very high sensitivity in this spectral regime. This paper gives a brief description of the VLT Interferometer and an update on its status.
Abundances in a Hot Horizontal-Branch Star in the Old Open Cluster NGC/6791
Authors: Peterson R.C. , Green E.M. 
Published: July 2016

The open cluster NGC 6791 is more metal-rich than any other open cluster, yet several hot blue horizontal branch (BHB) stars are probable members. We have performed an abundance analysis of the coolest such star, 2-17, which has a radial velocity and a proper motion which support cluster membership. We find parameters typical of a metal-rich BHB star, with rotational velocity = 16 ± 1 km/s, an effective temperature Teff = 7250 ± 150 K, log gravity = 3.5 ±0.5 dex, and an iron abundance more than twice solar, [Fe/H] = +0.4 ± 0.1 dex. The light even-Z elements Mg, Ca, and Si are further enhanced, ruling out A-star peculiarities. Its analysis thus establishes the cluster metallicity accurately, free from serious blending which is problematical in metal-rich giants. Abundances of C, N, and O suggest little mixing. Visual comparison of the spectra of red HB stars in the cluster with that of the field star μ Leo indicates that the spectra are indistinguishable except for stronger CN in the former.The high iron abundance, the light-element overabundances, the spectral similarity to strong-lined field giants, and the extensive presence of hot stars all highlight the fact that this old open cluster provides an excellent template for the study of metal-rich extragalactic systems. Properties of cluster members should establish not only accurate abundances for comparison with scenarios of nucelosynthesis and star formation, but also provide a testbed for ideas of the production of hot stars in a metal-rich environment, and so for the generation of the ultraviolet upturn in elliptical galaxies.