bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Older Clusters in the Magellanic Clouds
Authors: Gascoigne S.C.B. 
Published: July 2016

We begin with Fig. 1, which somewhat aged though it may be still illustrates important aspects of the subject (Gascoigne 1971)
(i)There is a clear division of cloud clusters into a blue and red group. The division corresponds to the mass around 2.51M⊙, at which core degeneracy first develops in stars approaching the giant branch. Such stars spend about three times as long on the giant branch and travel higher up it than the slightly heavier non-degenerate stars, and so dominate the colours of the clusters in which they occur.(ii)The red clusters are somewhat less luminous than the globular clusters in the galaxy. Freeman and Chun (1972) have shown from dynamic arguments that the cloud clusters are also less massive, by enough to keep the M/L ratios roughly the same as those in the galaxy.(iii)For a long time it has been taken that the blue clusters are young and the red clusters old. Thus the clouds present us with a truly two-parameter family of globular-like clusters, the parameters being of course age and abundance.
The Radio Interpulse from PSR 0950+08
Authors: Hankins T. H. , Cordes J. M. 
Published: July 2016

Two hypotheses exist to explain the radio interpulse of PSR 0950+08 within the context of polar cap emission models:
1)The emission originates at a single magnetic pole as for other two-component pulsars, except that the component spacing is much wider.2)The interpulse emission originates at the opposite magnetic pole. We discuss here some new observations and their implications for the single and double pole hypotheses.
Old and New Methods of Observing Polar Motion
Authors: Vicente R. O. 
Published: July 2016

The motion of the pole has been observed by means of visual telescopes, employed by the ILS, photographic zenith tubes and astrolabes. It is pointed out the difficulties of combining the results of different types of instruments employing several observation techniques.The new astronomical methods of Doppler observations on satellites and laser pulses sent to the Moon give another possibility of determining polar motion with greater precision. It is forecast that the results will not agree with the older ones and, in order to compare the methods, it is suggested that stations should be equipped with both techniques of detecting polar motion.
Some Results from the Automatic PZT at Richmond, Florida
Authors: Monger Don R. 
Published: July 2016

Automatic operation of the PZT located at the U.S. Naval Observatory Time Service Substation, Richmond, Florida was initiated February 1, 1970. A comparison of one year's automatic operation with the previous year's operation has shown a significant increase in the number of time and latitude sights obtained.Based on an improved ventilating system within the PZT, the probable error of a single night's observation has been reduced.
Motion of the Core, and Its Influence on the Earth's Axis
Authors: Mateo Jose 
Published: July 2016

After the advent of artificial Earth satellites, an accurate knowledge of the harmonic coefficients of the Earth's potential has enabled us to determine the size and shape of the Earth with extraordinary accuracy.The gravitational force between the core and the rest of the Earth, which makes both centers of mass tend to coincide, is so enormous that there is a strong possibility of a very slow motion of the core forcing its way into the mantle. It includes secular variations in both latitude and the time of rotation of the Earth.
Nearly Diurnal Nutation Derived from the Observations of Time and Latitude
Authors: Débarbat Suzanne 
Published: July 2016

The results, given below, of investigations are based on 14 yr of observations carried out with the Danjon astrolabe at the Paris Observatory; such observations allow the measurement of time and latitude.Previous analysis, based on 6,5 yr showed some periodic terms and, in particular, it had been possible to determine values of the nearly diurnal nutation (results presented at the 6th Symposium on Earth Tides, 1969).
Remark in Regard to Bidelman's Data-Bank Project
Authors: Bidelman W. P. 
Published: July 2016

The concept of a general stellar data bank is not a new idea, but the desirability of this project at the present time has been emphasized by a number of astronomers (Bidelman, Jaschek, Cayrel, Hauck and others) and work is proceeding both in the United States and elsewhere. The status of my own activities in this direction is as follows:The general stellar data file now at the Warner and Swasey Observatory is continually being updated and much more of the astronomical literature is being systematically searched and the resulting data and references entered into the file. However this project is still largely unfunded and progress is far slower than desirable. In particular the file is still not available in machine-readable form, though several of the newer large data catalogues, such as the Warner and Swasey southern OB-star survey of Stephenson and Sanduleak, will be entered into the file in IBM card-form rather the entire file will be converted to punched cards.
The Southern Objective Prism Survey
Authors: Stock J. , Wroblewski H. 
Published: July 2016

Five thousand sq deg of the Southern sky of intermediate to high galactic latitude have been surveyed with deep objective prism plates, taken with a UV-transparent prism. The plates reach on the average the 13th photographic magnitude and have been searched for the following types of objects: (1) high luminosity stars, (2) planetary nebulae, (3) metal weak late-type giants, (4) Me stars, (5) carbon stars, (6) early-type subdwarfs, (7) peculiar objects. Catalogues containing a total of over 3200 objects of these types have been compiled and will soon be published in Publ. Dpto. Astron. Univ. de Chile.Of particular interest are the metal-weak late-type giants, which are believed to be members of the galactic halo population. Slit spectra were obtained for a number of these stars and radial velocities derived. In each case the object was found to be a high velocity star. In view of the large number of such objects found in the survey, a method of determining relative radial velocities from pairs of objective prism plates was developed. The method, which is described in detail in the following paper, was tested successfully on several plate pairs, confirming the high velocities for the metal weak stars and showing that the method could be used for an exhaustive search for high velocity stars.
Observations of Stellar Spectra Related to Extended Atmospheres
Authors: Wright K. O. 
Published: July 2016

Although the Struve Symposium was planned to discuss conditions in binary stellar systems, it is necessary to consider the observations of extended atmospheres in single stars in order to compare them with those of binary systems. The Sun, being the closest star, has the first chromosphere that was observed, and we can assume that the many features observed on the Sun will be much enhanced in giant stars with more extended atmospheres. Among the early-type stars, the hydrogen emission lines in the spectra of Be stars are known to vary and this suggests the atmospheres are unstable. Similar, even more pronounced effects, are seen in the spectra of shell stars such as 48 Librae. The supergiant stars have also been shown to have spectral lines that change, often quite rapidly, with time. Smolinski has observed in the spectra of some F and G-type supergiants much-broadened absorption lines that also vary with time. Wilson's systematic studies of the H and K emission lines in late-type stars have greatly extended our knowledge of stellar chromospheres, and the ionized magnesium lines at 2800 Å should give additional information as more extra-terrestrial observations are obtained. Numerous observations of the ζ Aur stars have been obtained near eclipse; ζ Aur and 31 Cyg seem to be similar systems and show similar phenomena – a rise in temperature outward from the photosphere and an extensive, variable calcium chromosphere, but a viable theory for these chromospheres has not yet been given. VV Cep and 32 Cyg probably are larger and more complex systems. The emission lines in the ultraviolet spectra of the M-type stars may be indicators of coronae in these cooler atmospheres. Most variable stars seem to have extended atmospheres and, when detailed studies are made, show changes in both light and spectrum. Shock-wave phenomena are undoubtedly important in the analysis of many of these stars, as also are fluorescent, selective-excitation processes. Flare stars, though generally dwarfs, are of great interest in studies of stellar atmospheres.Extended atmospheres can be detected from observed gross deviations from local thermodynamic equilibrium, as in the study of emission lines, large velocity fields, and dilution effects. It is probable that the presence of a companion affects the atmosphere of the primary star in close double stars, but in stars like ζ Aur and 31 Cyg, the atmospheric effects produced near eclipse may be among the best clues for the interpretation of extended stellar atmospheres.
Black Holes in Binary Systems: Observational Appearances
Authors: Shakura N. I. , Sunyaev R. A. 
Published: July 2016

The outward transfer of angular momentum of accreting matter can lead to the formation of a disk around the black hole. The structure and radiation spectrum of the disk depends, in the main, on the rate of matter inflow Ṁ into the disk at its external boundary. Dependence on the efficiency of mechanisms of angular momentum transport (connected with the magnetic field and turbulence) is weaker. If Ṁ = 10−9–3 × 10−8 M⊙/yr, the disk around the black hole is a powerful source of X-radiation with hv ∼ 1–10 keV and luminosity L ∼ 1037–1038 erg s−1. If the flux of the accreting matter decreases, the effective temperature of radiation and the luminosity will drop. At the same time when Ṁ > 10−9M⊙ yr−1, the optical luminosity of the disk exceeds the solar one. The main contribution to the optical luminosity of the black hole is due to the re-radiation of that part of the X-ray and ultraviolet energy which is initially produced in the central high temperature regions of the disk and which is then absorbed by the low temperature outer regions. The optical radiation spectrum of such objects must be saturated by the broad emission recombination and resonance lines. Variability is connected with the character of the motion of the black hole and the gas flow in binary systems and possibly with eclipses. For well defined conditions, the hard radiation can evaporate the gas. This can counteract the matter inflow into the disk and lead to autoregulation of the accretion.If M ≫ 3 × 10−8 (M/M⊙) M⊙ yr−1, the luminosity of the disk around the black hole is stabilized at the critical level of Lcr = 1038 (M/M⊙) erg s−1. A small fraction of the accreting matter falls under the gravitational radius whereas the major part of it flows out with high velocities from the central regions of the disk. The outflowing matter is opaque to the disk radiation and completely transforms its spectrum. As a consequence, a black hole in a supercritical regime of accretion can appear as a bright star with a strong outflow of matter.
UHURU Results on Extragalactic X-Ray Sources
Authors: Kellogg Edwin M. 
Published: July 2016

Data from the UHURU satellite have provided a list of more than forty high latitude sources (|b| > 20°). X-rays have been detected from among the nearest normal galaxies, giant radio galaxies, Seyferts, QSOs and clusters of galaxies. The cluster sources appear to be extended by several hundred kiloparsecs as well as being very luminous. These cluster sources have systematic differences in their X-ray spectra from individual galaxies.About twenty sources are not reliably identified so far. A few of these are located near undistinguished 3C or MSH radio sources. The rest are either located near distant clusters or undistinguished bright galaxies, or are too far south, so that we have not sufficient optical data to allow a thorough search for possible association with clusters or unusual individual galaxies.The luminosity function for weak, high latitude X-ray sources is determined, and the contribution of sources just below the UHURU threshold of detectability to observed fluctuations in the diffuse X-ray background is evaluated. The total contribution of all observed types of extragalactic sources to the X-ray background is estimated.
Absorption and Production of Soft X-Rays in the Galaxy
Authors: Hayakawa S. 
Published: July 2016

The column densities of interstellar hydrogen to X-ray sources derived from their spectra are compared with those obtained from 21 cm radio observations. Referring to several observed results on Cyg X-2, Cygnus Loop etc., the interpretation of the low energy cut-off of the spectrum in terms of the interstellar absorption is subject to ambiguities due to a modification of the emission spectrum by Compton scattering in the sources and the contribution of emission lines.The result of soft X-ray sky surveys indicates that the diffuse component of soft X-rays consists of the extragalactic and the galactic components. The former has a hard component with a power law spectrum and a soft component which may be represented by an exponential spectrum. The galactic component is so soft that its spectrum may also be explained by thermal bremsstrahlung of temperature of about 0.1 keV. Its generation rate may account for the heating and ionization of interstellar matter. It is suggested that galactic diffuse soft X-rays are produced by active stars of a rather high number density.
The non-thermal radio-emission from the Galaxy
Authors: Baldwin J. E. 
Published: July 2016

In this review of the non-thermal continuum radiation from the Galaxy, the following issues are discussed:(1)The non-thermal continuum radiation in the disk.(2)Evidence for spiral arms in the non-thermal continuum, and the origin of the radiation in sources or in large-scale magnetic fields.(3)The nature of the spurs extending to high galactic latitudes.(4)Evidence for the existence or absence of a radio halo.(5)The galactic radio spectrum and its relation to the cosmic-ray electron spectrum.(6)Supernova remnants, their structure and spectra.(7)A comparison of the Galaxy with other normal galaxies.(8)Observational needs.
Spectral data for galactic X-ray sources and their implications for gamma-ray observations
Authors: Tanaka Y. 
Published: July 2016

The available information on the spectra of Sco X-1, Tau XR-1, Cyg XR-1 and of the background X-ray emission is summarized. Sco X-1 has an exponential spectrum; the other spectra can be represented by simple power laws. Possible mechanisms for the X-ray emission of the sources are briefly discussed.Comparison of gamma-ray observations with extrapolations of X-ray spectra suggests that gamma-ray emitters may be found among X-ray sources. The importance of gamma-ray observations to studies of interstellar matter is stressed.
Far-ultraviolet intensities of Orion stars
Authors: Carruthers George R. 
Published: July 2016

Photometric data in the 1050–1180 Å and 1230–1350 Å wavelength ranges, and electronographic spectra in the 1000–1600 Å wavelength range, were obtained in an Aerobee rocket flight on January 30, 1969. The spectral intensities derived from these data for main-sequence stars are in good agreement with the model atmospheres of Morton and co-workers. Giant and supergiant stars, however, appear to be up to one magnitude weaker, at 1115 Å, than main-sequence stars of the same spectral class.The correction for interstellar reddening appears to be not inconsistent with a 1/λ extrapolation of earlier determinations of Smith (1967) and Stecher (1965), except in the case of θ Ori, in which the predicted color excess appears to be much too great, confirming the existence of a peculiar reddening law in the Orion Nebula region.
A discussion of the theory for interpreting ultraviolet stellar spectra
Authors: Underhill Anne B. 
Published: July 2016

The observed spectral distribution from a star will, in principle, give information about the parts of the atmosphere from which the radiation comes. Most detailed theoretical studies assume that the atmosphere may be represented by plane parallel layers, but in the case of very strong absorption lines and weak continuous absorption, a case which is encountered in the ultraviolet spectral region of B stars, the radiation received from the centers of the lines may come from an entirely different part of the star than does that from the far wings of the lines or from the continuous spectrum. In the case of strong lines, because stars are three dimensional objects and because a field of motion may occur in the outermost part of the atmosphere, the appearance of the ultraviolet line spectrum may be poorly predicted using the hypothesis of stationary plane parallel layers.Some numerical examples are presented demonstrating that with the UV resonance lines the opacity in the centre of a line may exceed the continuous opacity by a factor 106–108. A summary is given of the chief factors which should be taken into account in any theory of line formation when the hypothesis of LTE is not valid. A detailed description of the interactions between radiation and matter which can occur is necessary. Some examples of the distribution in energy of the lower energy levels of the ion are presented for typical ions of interest. This distribution and the presence of metastable levels are important factors in determining the significance of non-LTE physics. The paper concludes with remarks indicating that ultraviolet spectra of stars should be obtained with a spectral purity of at east 0.1 Å if progress is to be made in understanding the physical state of stars.
The spectral characteristics and probable structure of the cloud layer of Saturn
Authors: Teifel V. G. , Usoltzeva L. A. , Kharitonova G. A. 
Published: July 2016

Spectrophotometric (photographic and photoelectric) measurements of the intensity of CH4 absorption bands at 6190 and 7250 Å over different regions of Saturn's disk show an increase in intensity toward the poles and a decrease toward the equatorial limb. In the bright equatorial belt of Saturn the methane absorption is about 25–28% less than in the south temperate belt (latitude about −20°).Absolute photoelectric spectrophotometry of Saturn's disk gives a value for the single-scattering albedo of the aerosol particles at λ 6200–6500 Å at the center of the disk. Calculations of the curves of growth for the absorption lines formed in the thin gas and in the cloud layer were made and the comparison with observations of Jupiter and Saturn lead to the mean value of the volume scattering coefficient of the aerosol layer σa < 5 × 10−6 cm−1. In the equatorial region of Saturn σa is larger than in the temperate region by a factor 1.3 to 1.8.The models of Saturn's atmosphere that fit well the observational data preclude the condensation of methane. An aerosol layer of ammonia is more probable in the atmosphere of Saturn. Calculations of the distribution of the ammonia aerosol volume density (Qa) give Qa ≃ 10−9 to 10−7 gm/cm3 for relative abundances of ammonia A = 10−6 to 10−4. Observational estimates of Qa derived from the values of σa give Qa < 10−9 gm/cm3. Apparently Saturn's atmosphere departs from conditions of ordinary convection.Some very interesting variations in the spectral reflectivity of the different regions of Saturn are observed, especially in the ultraviolet. These data, as well as a systematic study of the methane absorptions in the near infrared strong bands are needed in future studies of Saturn's atmosphere.
Gamma-Ray Spectrometry in the Energy Range 0.5–5 MeV
Authors: Albernhe F. , Doulade C. , Martin I. M. , Talon R. , Vedrenne G. 
Published: July 2016

A stilbene scintillator detector allowing gamma-ray spectrometry in the range 0.5–5 MeV is presented. A complete elimination of charged particles is obtained by a plastic scintillator anticoïncidence jacket. Separation of gamma rays from neutrons is made by pulse shape discrimination technique with over 99% efficiency. This detector which has a 4 π field of view has been made as light as possible to avoid perturbation due to secondary production in the apparatus. The correction of the edge effects and the method of conversion from experimental Compton electron spectrum to gamma-ray spectrum are explained.Results from balloon launchings at three latitudes (Kourou Guyana: 10 N, Aire sur l'Adour: 46°N and Oboziersky U.S.S.R.: 62 °N) are briefly presented. The detection possibility with balloons of galactic gamma rays at equatorial latitude is shown. The atmospheric part of the flux at the equator is deduced from the measurements at higher latitudes, (46 °N and 62 °N) where the galactic component is of negligible importance. Assuming a power law spectrum and after correction of the atmospheric absorption we obtain for the galactic spectrum the expression dN/dE = 1.1 × 10−5E−1, 2 photons/cm2 s sr keV. This spectrum agrees with the results of ERS 18 satellite given by Vette et al. showing an excess of flux for energies higher than 1 MeV.
Rocket Experiment by Electronic Camera for Studying the Metallic Discontinuities in the Ultraviolet Spectrum of ‘A’ Stars
Authors: Combes M. 
Published: July 2016

1.Ultraviolet spectra (1400–1800 Å) of Ap, Am and normal A stars are needed by F. Praderie, R. Bonnet and R. Cayrel.The spectral resolution has to be nearly 1 Å. Accurate relative photometry (5%) and absolute calibration (30–50%) are required.A rocket experiment, proposed to ESRO by M. Combes and P. Felenbok is planned for launch in 1972.2.As neutral silicon and magnesium are very efficient ultra-violet absorbents, A stars ultraviolet fluxes are very faint (Praderie, 1968).Then a very luminous optical set-up and a high efficiency receiver have to be used. A 30 cm in diameter concave objective grating is associated with a Lallemand electronic camera. The grating (2000 //mm; //l) is holographically made (Labeyrie, 1969). The electronic camera is electrostatically focussed. A semi-transparent solar-blind CsL photocathode is used (Carruthers, 1966).3.A little mirror, placed against the grating and forming a direct view of the sky, permits to establish an absolute wavelength scale.During the fly, before and after stellar observations, a little concave mirror mounted into the opening side-door is used to form on the photocathode a spectrum of a Deuterium calibrated lamp. Two photomultipliers, one on each side of the electronic camera, control the lamp stability.The complete mounting is calibrated in the laboratory using a thermopile as reference, before the launch and after the recovery of the waterproof payload.4.The chosen stars are the brightest Ap and Am stars: α Dra (Ap; mv = 3.64; equivalent type A 0) and α2 Lib (Am; mv = 2.75; equivalent type A3-A7).It seems to be possible to obtain spectra (1400-1800 Å) of the Ap star with a spectral resolution of 1 Å and a signal to noise ratio better than 40. But at a pinch one may accept a resolution of 2 Å and a signal to noise ratio of 15 for the shortest range of the Ap star spectrum.