bluuebunny/crossref_metadata_2025_split huggingface dataset:
On Coronal Instability and Moving Radio Features Associated with a Flare Spray
Authors: Daigne G. 
Published: July 2016

A solar radio outburst with its different parts well seen on metric wavelengths is described. A stable source shows successively two kinds of emission before the flash-phase of the event, and a moving type IV burst (V ≃ 1000 km/s), initiated 1/4 solar radius high, is directly associated with a spray-type prominence. Parameters of this radiating source are discussed.A type II burst seen on lower frequencies with a spectrograph (V ≃ 3200 km/s) seems to start after the flash phase. Two possible cases are considered for the generation of the shock-wave responsible for type II burst.
Fine Structure Within the Redshift-Magnitude Correlation for Galaxies
Authors: Tifft W. G. 
Published: July 2016

Previous work on the redshift-magnitude banding correlation is briefly reviewed. New tests of the concept are applied successfully to a second cluster (A2199) and the outer portions of the Coma cluster. Using more than 200 redshifts in Coma, Perseus, and A2199 the presence of a distinct band-related-periodicity in redshift is indicated. Finally, a new sample of accurate redshifts of bright Coma galaxies on a single band is presented, which shows a strong redshift periodicity of 220 km s−1. An upper limit of 20 km s−1 is placed on the internal Doppler component of motion in the Coma cluster.Redshift-magnitude bands are, therefore, now recognized to consist of discrete ‘spin states’ organized into ‘spin groups’ which show strong morphological associations. Bands are probably in turn organized into band systems. The individual spin states are suggested to represent distinct configurations of matter at the nuclear or fundamental particle structure level. Transitions between states in a time systematic sense of decreasing redshift (increasing internal binding) are suggested to occur in galaxy nuclei. Energy released in such transitions may be the driving energy in radio sources and related objects.
Structures of Central Bulges and Nuclei of Galaxies
Authors: De Vaucouleurs G. 
Published: July 2016

The isophotal surfaces of central bulges of normal spirals, often described as ‘spheroidal’, are shown to depart from ellipsoids of revolution and to resemble MacLaurin or Jacobi spheroids with zonal distortion; two typical examples, NGC 4565, 5746, are illustrated. Weaker examples are NGC 2683, 4594 and 891. Stronger examples are NGC 7332 and 128.The true nucleus of an ordinary spiral is at most a very small object (~ 10 pc) resolved only in the nearest galaxies. The apparently larger nuclei seen in more distant spirals and lenticulars, in particular the so-called N-types, are probably artifacts due to insufficient resolution. It is possible that even in M31 the small ‘nucleus’ is merely the seeing-convolved image of the central peak in the r1/4 luminosity distribution of the spheroidal component.In the nearest barred lenticulars and early spirals each large ellipsoidal ‘nucleus’ (~ 1.0 × 1.5 kpc) in the centre of the bar or central lens is found to include a second bar and inner nucleus on a smaller scale, in the approximate ratio of the corresponding Jeans' lengths. This is illustrated by high resolution photographs of NGC 1291; another example is NGC 1326.
On the Equation of State of Hydrogen and its Use in Models of Major Planets
Authors: Hawke R. S. 
Published: July 2016

Since Jupiter and Saturn are considered to be composed primarily of hydrogen, its pressure-density equation of state is needed for computational models of their interiors. Until recently, experimental data were limited to 20 kbar statically and 40 kbar dynamically. Since the majority of a major planet is at a pressure in excess of this, there were only theoretical calculations available for modeling.Wigner-Seitz type calculations have been shown to be accurate at determining the equations of state of the alkali metals. Hence, it has been assumed that the equation of state of metallic hydrogen can be calculated in the same way with fair confidence. However, the molecular hydrogen equation of state has been much more ellusive. The many attempts at modeling the interatomic forces have led to rather scattered pressure density relationships.The planetary model situation is further complicated by the expectation that the transition from the molecular to the metallic phase will be in conjunction with a relatively large density change.Recently, data from new experiments have become available; in one case up to 8 Mbar. The data are not in disagreement with many calculations on hydrogen, but the resolution is not yet adequate to determine accurately and confidently, the pressure and the densities of the molecular to metallic phase transition. The accuracy of these parameters in turn affect the models of the planetary interiors, such as the radii of the metallic sphere and high density core.This paper will discuss the details of these relations and the possible affects of the speculative properties of metallic hydrogen.
Jupiter's Radiation Belts and Upper Atmosphere
Authors: Degioanni Joseph J. , Dickel John R. 
Published: July 2016

Models of Jupiter's radiation belts have been constructed to determine the distribution of particles and their energies which will produce the observed decimetric radio emission. Data on the spectrum and the variation of emission with Jovian longitude have been used to show that the relativistic particles have a nearly isotropic distribution with high energies (of order 100 MeV) within 2 Jovian radii and a very flat distribution in the equatorial plane of low energy particles further out in the magnetosphere.Subtraction of the emission predicted by this model from the total radio emission shows that the thermal contribution in the frequency range between 3000 and 10000 MHz is somewhat less than had been previously expected. (The brightness temperature of the planetary disk is 180 K at 3000 MHz, for example.) This suggests that the ammonia mixing ratio in Jupiter's upper atmosphere may be as high as 0.002.
The Galactic Centre at 408 MHz
Authors: Little A. G. 
Published: July 2016

The Molonglo radio telescope has been used to map the galactic centre region with a resolution of 2.9′. Although similar to microwave maps of comparable resolution, there are differences. In particular, the source G1.05-0.1 is not visible at microwaves, and the source G0.1-0.0 is not visible at 408 MHz. The flux values of all the other sources around Sgr A confirm that they are thermal and that the sources G0.7−0.0, G0.5 − 0.0, and G0.2−0.0 are optically thick.A more extensive galactic background survey with the cross shows the existence of a peak in the background emission with a brightness temperature of about 500 K at the galactic centre. This is probably the nonthermal source observed at 85 MHz. The higher-resolution observations of this map show the narrower, hotter region which appears on the microwave map and which surrounds Sgr A. This has a brightness temperature of 2100 K, which cannot be accounted for by a simple thermal spectrum extrapolated from microwaves.
The Galactic Distribution of Wolf-Rayet Stars
Authors: Hidayat B. , Supelli K. , van der Hucht K.A. 
Published: July 2016

On the basis of the most recent compilation of narrow-band photometry and absolute visual magnitudes of Wolf-Rayet stars, and adopting a normal interstellar extinction law in all directions, the galactic distribution of 132 of the 159 known galactic WR stars is presented and discussed.The spiral structure is found to be more clearly pronounced than in earlier studies. Furthermore we find an indication of two spiral arms at r=4 and 6 kpc. There appears to be an asymmetry of the z-distribution of single stars with respect to galactic longitude.The location of the WC8.5 and WC9 stars between 4.5 and 9 kpc from the galactic center is discussed in the context of Maeder's red supergiant to WR star scenario.
Corrections for Hydrostatic Atmospheric Models: Radii and Effective Temperatures of Wolf Rayet Stars
Authors: De Loore C. , Hellings P. , Lamers H.J.G.L.M. 
Published: July 2016

With the assumption of planparallel hydrostatic atmospheres, used generally for the computation of evolutionary models, the radii of WR stars are seriously underestimated. The true atmospheres may be very extended, due to the effect of the stellar wind. Instead of these hydrostatic atmospheres we consider dynamical atmospheres adopting a velocity law. The equation of the optical depth is integrated outwards using the equation of continuity.The “hydrostatic” radii are to be multiplied with a factor 2 to 8, and the effective temperatures with a factor 0.8 to 0.35 when Wolf Rayet characteristics for the wind are considered, and WR mass loss rates are used. With these corrections the effective temperatures of the theoretical models, which are helium burning Roche lobe overflow remnants, range between 30 000 K and 50 000 K. Effective temperatures calculated in the hydrostatic hypothesis can be as high as 150 000 K for helium burning RLOF-remnants with WR mass loss rates.
An Analysis of the Rotational Acceleration of the Earth
Authors: McCarthy Dennis D. , Percival Donald B. 
Published: July 2016

The nature of the irregular fluctuations in the speed of the Earth's rotation was investigated using ninety-day means of UT2 - A.1 determined at the U. S. Naval Observatory. Data from June 1955 to April 1978 were included in this study. Statistical analysis of the excess length of day shows no evidence for the persistence of discrete values for periods on the order of five years. No statistical basis for the existence of discrete “turning points” in the rotational speed could be found.Spectral analysis of the acceleration data shows that the rotational acceleration of the Earth during this period of time may be represented by a constant term plus random changes in acceleration occurring with a frequency greater than once per year. The magnitude of these changes appear to be consistent with estimates of meteorologically induced changes in the rotational acceleration.An autoregressive integrated moving average (ARIMA) model was fit to the excess length of day data. This model permits simulated series of excess length of day data to be constructed. These simulated series show a statistical similarity to observations made since 1820. However the apparently large changes in the acceleration which occurred around 1870 and 1900 are twice that which can be reasonably accounted for by this model. The details of this analysis will be published later.
Concept for Reference Frames in Geodesy and Geodynamics: The Reference Directions
Authors: Grafarend Erik W. , Müller Ivan I. , Papo Haim B. , Richter Burkhard 
Published: July 2016

Modern high accuracy measurements of the non-rigid Earth are to be referred to four-dimensional, i.e., time and space-dependent reference frames. Geodynamics phenomena derived from these measurements are to be described in a terrestrial reference frame in which both space and time-like variations can be monitored. Existing conventional terrestrial reference frames (e.g., CIO, BIH) are no longer suitable for such purposes.The ultimate goal of this study is the establishment of a reference frame, moving with the Earth in some average sense, in which the geometric and dynamic behavior of the Earth can be monitored, and whose motion with respect to inertial space can also be determined.The study is conducted in two parts. In the first part problems related to reference directions are investigated, while the second part deals with positions, i.e., with reference origins. Only the first part is treated in this paper.The approach is based on the fact that reference directions at an observation point on the Earth's surface are defined by four fundamental vectors (gravity, Earth rotation, etc.), both space and time variant. These reference directions are interrelated by angular parameters, also derived from the fundamental vectors. The interrelationships between these space and time-variant angular parameters are illustrated in a commutative diagram–tower of triads, which makes the derivation of the various relationships convenient.In order to determine the above parameters from observations (e.g., laser ranging, VLBI) using least squares adjustment techniques, a model tower of triads is also presented to allow the formation of linear observation equations. Although the model tower is also space and time variant, these variations are described by adopted parameters representing our current knowledge of the Earth. For details, see Bulletin Géodésique, end of 1978.
Reasons and Possibilities for an Extended Use of the Transit System
Authors: Pâquet P. , Devis C. 
Published: July 2016

Observations of Earth rotation and polar motion are now performed on a routine basis by classical astronomical methods and by the satellite Doppler technique.In the near future the laser is likely to realize its old objective of determining ER and PM with an accuracy of a few milliseconds of arc through ranging to Lageos. VLBI is still in development.To permit investigation of possible systematic differences, all these techniques should be used simultaneously for a period whose length should not be set in advance.The Doppler method can still be improved and could be easily introduced at many observatories in support of the Medoc campaign. We present here two possible methods of data condensation which, if implemented, would permit much of the data analysis to be done at the tracking stations and would reduce to a very few the number of parameters required by the central computing agency.
The Geophysical Interpretation of Changes in the Length of the Day and Polar Motion
Authors: Runcorn S.K. 
Published: July 2016

The data on the irregular fluctuations in the length of the day and the motion of the pole is of great significance in the geophysicist's task of constructing a model of the earth's interior.Short term instabilities in the dynamo generating the earth's magnetic field produce what is observed at the surface as the secular variation. These changes induce currents in the lower mantle and the resulting torques appear to be the cause of the irregular fluctuations in the length of the day, although some quantitative problems remain.The excitation of the Chandler wobble could result from impulsive torques applied to the mantle by very short period (a year or less) local magnetic field disturbances coming to the surface of the core. The alternative mechanism by earthquakes has been much investigated and the possibility of this is still obscure. A test however is available in the polar motion data: a disturbance in its path displaces the subsequent centre of its Chandler motion in the latter theory, but only its amplitude on the former theory. The behaviour of the pole around 1968 supports the core theory, but much more analysis of the polar motion is required.
A Statistical Investigation of Microwave Burst Spectra for the Determination of Source Inhomogeneities
Authors: Schoechlin W. , Magun A. 
Published: July 2016

SummaryThe spectra of a set of 77 microwave bursts of July 1971 to September 1974 as published in Solar Geophysical Data have been fitted with an idealized spectrum of triangular shape. The spectral index of the low frequency part α, the maximum flux density and the associated frequency have been determined. A cluster-analysis carried out on these parameters showed that the sample consists of only one class of events. In the histogram of the spectral index we found a most frequent value of 1.4. Such a low value cannot be explained by the mechanisms normally assumed to account for the low frequency attenuation, as gyroresonance absorption and the Razin effect.
Satellite Observations of Solar Radio Bursts
Authors: Steinberg J.L. 
Published: July 2016

Space observations of solar radio bursts have provided the following information:– From a single spacecraft:Measurements within the burst source or close to it: fundamental and harmonic type III radio emission, the corresponding plasma waves and spectra of the exciting electrons.– From a spacecraft and the earth or from two spacecrafts:A better evaluation of the influence of the ionosphere on some ground-based observations.Measurements of the beaming of the emission which yield constraints on the radiation mechanism and/or the role of coronal propagation in determining the source size and directivity (type I and III's).Measurements of the differential time delay which yield for type III:At short (m- and dam-) wavelengths, some evidence of group delays,At long (hm- and km-) wavelengths one coordinate of the source.Complete (3-dimensional) localization of the source at long wavelengths and therefore maps of the heliosphere magnetic field and electron density as well as the source size and, in the future, its polarization.The results of these observations and their interpretation are reviewed and discussed.
Decametric Radio Bursts Associated with Coronal Loop Structures
Authors: Gergely T. E. , Kundu M. R. , Golub L. , Webb D. 
Published: July 2016

The soft x-ray (2–54 Å) pictures obtained by the S-054 experiment aboard SKYLAB provide an excellent opportunity to study the association of x-ray loop structures with radio bursts. We report here on the properties of meter-decameter wavelength radio bursts which appear to be associated with two different types of loop structures:
a)Relatively short lived small scale loops, which are observed to link magnetic fields of opposite polarity, called x-ray bright points (XBPs); andb)Longer lived loop systems which appear to connect opposite magnetic polarities of an active region and active region complexes as well.
Le Spectre des Etoiles Oe dans le Rouge et le Proche Infrarouge
Authors: Andrillat Y. , Vreux J. M. , Dennefeld M. 
Published: July 2016

Among the 0 stars, Conti and Leep (1974) define the Oe class as those stars showing emission in the hydrogen lines but without emission in N III or 4686 He II.In the blue-red region, aside from the presence of Lambda 4542 in absorption, the overall appearance is similar to Be stars. So far no Oe star has been observed until 1.1 μ: the aim of this paper is to fill this gap. We present observations of Oe stars in the near infra-red region as well as new observations of Hα profiles.
Apparent Rotation of the Galactic Globular Cluster System
Authors: Colin J. 
Published: July 2016

We use the radial velocities of galactic globular clusters, corrected for solar motion to calculate their apparent angular momentum. Comparing the apparent angular momentum with a numerical simulation we show, with 90% confidence, that the globular cluster system is in prograde rotation. The distribution of angular momentum with Fe/H reveals three distinct groups of clusters with different kind of rotation:1) 19 clusters with Fe/H > −0.8 have a solid-body rotation in the direct sense.2) 33 clusters with −1.75 < Fe/H < −0.8 do not exhibit any rotation (80%. confidence).3) 27 clusters with Fe/H < −1.75 have a uniform rotational velocity in the direct sense (90% confidence).
Globular Clusters as Extragalactic Distance Indicators: Maximum Likelihood Methods
Authors: Hanes David A. , Whittaker Donna G. 
Published: July 2016

We have explored the use of maximum likelihood estimation techniques in the use of globular cluster luminosity functions (LFs) as distance indicators. In particular, we have tested size-of-sample effects through the analysis of Monte Carlo simulations of LFs drawn from an assumed universal population like that characterizing the globular clusters in the Local Group. Our working assumption, following others before us, is that the underlying LF is adequately well described by a Gaussian normal in a number vs. absolute magnitude representation.For typically observable sample sizes in studies which are limited to the bright half of the LF, statistical limitations preclude a precise determination of the attributes which fully describe the LF, even in the absence of field object contamination. In particular, the intrinsic dispersion (the shape parameter of the LF) must be taken to be a universal constant, independent of galaxy type; only then may the turnover magnitude (which contains the distance information) be derived with good precision. Some data exist for nearby galaxies (including ellipticals) which permit an assessment of the universality of the intrinsic dispersion: they are not inconsistent with the hypothesis. However, it will be important to test this point in future as more data are secured.Real globular clusters in remote galaxies are unresolved, and the samples are contaminated with foreground field stars and remote background objects. This contamination necessitates corrections which are statistical in nature, applicable to binned LFs. Through numerical simulations, we have tested the limitations imposed by realistic numbers of field objects in globular cluster LFs in remote galaxies, testing for systematic biases and assessing the attainable precision in derived distance as a function of the sample size and the limiting magnitude.
10. Radio observations of interstellar neutral hydrogen clouds
Authors: Lawrence R. S. 
Published: July 2016

The detailed relationship between optical interstellar absorption lines and 21-cm. observations is investigated in this paper.Dr Guido Münch, of the Mount Wilson and Palomar Observatories, provided the list of six intermediate-latitude stars shown in Table 1. The spectra of these stars all show complex absorption lines due to interstellar Ca 11. The 21-cm. line is measurable in four of the six regions, although the peak intensity is low in each case. It is noteworthy that for the first two stars on the list the radio velocity agrees closely with the velocity of an intense optical component. In view of the great difference in angular resolution, the failure to find correspondence in every case is not surprising.
Les sources d'emissions radioelectriques du soleil
Authors: Denisse J. F. 
Published: July 2016

Si les émissions radioélectriques du soleil sont dépourvues de la richesse d'informations apportée par les spectres optiques, elles se révèlent, par contre, particulièrement bien adaptées à l'étude d'une très grande variété de perturbations solaires, dont bien souvent les observations optiques n'avaient même pas permis de soupçonner l'existence, et ceci pour plusieurs raisons:1. Ces émissions, souvent transitoires, intéressent particulièrement la couronne, ou la haute chromosphère, où les observations optiques sont discontinues et difficiles en raison de l'éblouissement par le disque photosphérique qui n'existe pas en radio.2. Certaines ne sont pas d'origine thermique: le plasma coronal possède diverses possibilités de rayonnement (oscillations de plasma, rayonnement synchrotron ou Čerenkov) plus aisément ou seulement perceptible dans le domaine radioélectrique.Les sources solaires d'émissions radioélectriques sont multiples et se distinguent essentiellement par leur stabilité plus ou moins grande et la nature de leur rayonnement; pour le moment on ne possède pas beaucoup d'indications sur leurs dimensions, encore moins sur leur structure.