bluuebunny/crossref_metadata_2025_split huggingface dataset:
Secular and Long-Term Variations of the Polar Motion
Authors: Proverbio E. , Carta F. , Mazzoleni F. 
Published: July 2016

An analysis on the secular motion of the pole has been carried out utilising the latitude observations of the ILS stations reduced to the ØII(i) system (Proverbio et al., 1969).The existence of long periodic terms in the polar motion as found out by Markowitz (1960) was confirmed.The secular displacement of the polar motion calculated abstracting from long period terms results 0″.00294 for year along the meridian 65°.6 W.A probable drift of continental blocks with average Northward rate of 1–2 cm/year for Eurasia and 1 cm/year for North America has been suggested. The possible drift emphasized for Japan is on the contrary of 1 cm/year southwards.
The ATS-F/NIMBUS-E Tracking Experiment
Authors: von Bun F. O. 
Published: July 2016

In this paper the objective of the ATS-F/NIMBUS-E Tracking Experiment, the first of such kind, is presented. Specifically, this experiment has a two-fold purpose: First, to gain experience in the practical use of satellite-to-satellite range and range rate data for very accurate orbit determination (this was its original intent); and second, to evaluate the real usefulness of such a technique for geodetic studies despite the fact that the 1000 km NIMBUS orbit is not ideally suited for such a purpose.The accuracies of the tracking systems of the satellite-to-satellite and satellite-to-ground link (ATS-F to the Rosman, N.C. ground station) will be ~ 0.035 cm/s in range rate and ~ 1 m in range – utilizing a 10 s integration time. With these values one obtains, based upon performed error analyses, orbit height errors in the order of 0.1 to 0.3 m for the near earth orbiting NIMBUS spacecraft. This experiment will therefore hopefully prove to be a significant first step for future Earth applications spacecraft carrying altimeters systems for measuring ocean height variations.In addition, laser corner reflectors placed on board the ATS-F will make a total independent position determination of this spacecraft to approximately 15 m to 30 m possible, assuming that the location errors of four laser tracking stations used to determine the orbit are about 3 m or 5 m in each component respectively, with laser ranging system noise errors of 1.2 m and bias errors of 0.15 m. A small position error of the ATS-F, the ‘orbiting tracking station’ is essential in order to make full usage of the small satellite-to-satellite tracking errors mentioned.For purpose of geodetic studies, one of the final goals, range rate variations of 0.1 cm/s or less corresponding to surface gravity anomaly of 20 mgal or less (over a half-width of 100 km on the Earth surface), will have to be measured during a time interval of approximately, say, 30–60 s. These values are within the range of the planned tracking systems accuracies for ATS-F and NIMBUS-E.
On the Determination of Anomalous Refraction out of Astrometrical Measurements in the Zenith Zone
Authors: Teleki G. , Ševarlić B. 
Published: July 2016

The method is given for the analysis of the anomalous refraction in the zenith zone. Connected with this the observations of the same zenith stars in the meridian and the prime vertical are used. The moment of passage through the eastern and western part of the prime vertical is registered, while the difference of zenith distances in the meridian passage is measured – always in two instrument position.The method practically eliminates coordinate errors influences of observed stars. For the succesful employment of this method, we must use the high quality instruments and, especially, correct apparatuses for the carreful determination of the inclinations of instrumental parts.
On the Automatic Electronic Astrolabe
Authors: Tsubokawa Ietsune , Hokugo Shunro 
Published: July 2016

The pendulum astrolabe with an electronic transit detector after the principle proposed by I. Tsubokawa has comparable accuracy to those of the Danjon astrolabe and P.Z.T. even in the field. After the same principle, an instrument for observatory use is being constructed, in which all observational processes are done automatically under the predetermined programs. The necessary mechanisms for automatic operation are as follows:(1) Azimuth setting mechanism for respective stars observed.(2) Mechanism which turn the telescope through 180° during the passage of a star near the mean altitude.(3) Tracking mechanism in azimuth direction.(4) Tracking mechanism in altitude direction.(5) Read-out mechanism of the times of passages of a star on respective altitude circles.Of these, the altitude tracking mechanism directly affects the observational accuracy. The rotation of a plane parallel glass compensates the diurnal motion of a star and keeps its image in the state of repose on the edge of a prismatic knife of the electronic detector. The rotating mechanism gives to the plane glass combined rotation of the two parts; the servo-system of the electronic detector and the system of generating the variable rotational velocity corresponding to the diurnal motion of a star. The extreme accuracy in the earth's atmosphere is expected.
Two-Dimensional Classification of the HD Stars
Authors: Houk N. , Cowley A. 
Published: July 2016

The major project of assigning spectral and luminosity classes to the Henry Draper stars south of +30° is underway. The high-quality objective-prism plates have been taken with the Michigan Curtis Schmidt telescope at Cerro Tololo Inter-American Observatory. The spectra, widened to .8 mm, have a dispersion of 108 Å mm-1 at Hγ. Plates exposed for 20m and for 4m + 1m yield classifiable spectra between 4 and 10 mpg.Star identification is completely automatic, using a computer-generated plot to the Schmidt plate scale for each plate center. This plot, having the HD stars identified by number, is copied onto transparent material and placed under the Schmidt plate while the stars are visually classified.Classification is being carried out by one person (N.H.) to maintain a uniform system. MK spectral standards of similar quality and density, also taken with the Schmidt, are continually referred to. Intercomparison of the new types with existing spectral types shows no systematic differences. However, the HD types themselves are systematically earlier in the range A to F.Stars between the south celestial pole and δ = −55° are being classified first, with the first volume of results to be published late in 1973. It is expected that the catalogue of spectral types and remarks will be published in 6 volumes containing all HD stars south of +30°.This research is being supported by the National Science Foundation.
The David Dunlap Observatory (DDO) Photometric System for Classification of Late-Type Stars
Authors: McClure R. D. 
Published: July 2016

An intermediate bandpass filter system is described that is useful for classification of G and K stars in terms of effective temperature (spectral type), surface gravity (luminosity class), heavy element abundance, and interstellar reddening. The system measures the strength of the cyanogen band in the region shortward of λ4216, the break in the continuum at the G band, and a colour index in the λ4500–λ4900 region of the spectrum. The surface gravity parameter is independent of the cyanogen index, and the cyanogen band strength, after a surface gravity correction, is used as a measure of heavy element abundance.Application of the system to the determination of the atmospheric parameters of open cluster giants, as well as of field stars, is discussed. The system has been used to isolate stellar populations among field stars without any prior knowledge of their distances. From observations on this system, the only open cluster found so far to have giants with stronger cyanogen band absorption than the Hyades giants is the intermediate age southern cluster NGC 2477.
Low Dispersion Spectrophotometry of Late Type Stars
Authors: Moreno H. 
Published: July 2016

Low dispersion (slit 60 Å wide) spectrophotometric observations of late type stars have been made. The sample of stars observed cover from K0 to M8 and luminosity classes V to I.A selection of these stars including each luminosity class and spectral type is being analyzed. The observed intensity distributions have been corrected for atmospheric extinction and have been normalized to a common maximum intensity. The resulting instrumental intensity distributions are being studied for the best parameters for spectral classification.
Formation of the Galaxy
Authors: Lynden-Bell D 
Published: July 2016

From observations it is deduced that the disk and halo were formed about the same time and that most of the previously gaseous Galaxy became stars then. Dimensional analysis indicates that the flattening of a galaxy is related to its energy,E, angular momentum,H, and mass,M, by the dimensionless number - 2EH2/G5M5. Emphasis is placed on the binding energy, -E, and the energy loss mechanisms of the proto-galaxy, with the aim of explaining Fish's relation -E∝M3/2.Free-bound and free-free emission of hydrogen leads to rapid cooling of proto-galaxies, and dynamical collapse ensues, in which gravitational potential energy is converted into kinetic energy of collapse. As the system becomes flat, this energy is dissipated in violent shocks, behind which zones some 10 to 20 pc thick reach temperatures of 106·5°K and emit strongly in the X-ray region and the ultraviolet. If surrounded by more than a fraction of a gram per cm2, the X-rays will be trapped within the system and eventually converted into Balmer lines, which escape, and Lyman α, which is trapped. About half the total energy of collapse may be left in Lyman α, and it is possible that the system may bounce on this light energy.The readily observed surface brightnesses of galaxies are related to surface densities by the relationship: magnitude 20 per (sec of arc)2= 1·5 gram cm-2, for an assumed mass-to-light ratio of 10.
Measurement of interstellar extinction in emission line stars
Authors: Viotti R. 
Published: July 2016

Usually selective interstellar extinction is derived by comparing the spectrum of a reddened star with an unreddened nearby star, preferably of the same spectral type. But in many cases this comparison is not possible, so that new methods have to be used.A direct measure of this quantity is possible when a spectrum shows a number of emission lines as for the peculiar stars (novae, nova-like objects, symbiotic stars, etc.) and for nebulae. From a statistical point of view there are a small number of objects but they are of very high interest as far as stellar evolution is concerned.
Ultraviolet photometry of stars obtained with the Celescope experiment in the Orbiting Astronomical Observatory
Authors: Davis Robert J. 
Published: July 2016

We have used the television photometers in the Celescope OAO experiment to measure the far ultraviolet brightnesses of several thousand stars, including parts of the constellations Draco, Lyra, Puppis, Vela, Taurus, and Orion; and the Moon. As of this date (22 July 1969), three of our four cameras continue to operate satisfactorily, and we are making measurements in additional star fields distributed throughout the sky. Our shortest wavelength band, which includes the Lyman α line of atomic hydrogen, provides information on the Earth's outer atmosphere, as well as on star brightnesses. The intensity of the Lyman α radiation from the geocorona is a maximum when the Sun is near the horizon as seen by the OAO, and a minimum when the Sun is in the nadir. The direction that the telescope points does not much affect the measured intensities.Because of the heavy logistic problems of identification, calibration, and measurement for so many stars and because of the survey character of the program, the scientific interpretation of the results is, as expected, lagging the measurement program. However, one consistent picture beginning to emerge from our data is that our observed stars are about equally divided between those that fall within 0.5 magnitude of the predicted ultraviolet brightnesses and those that are significantly fainter than predicted. Most of the giant stars we observe exhibit these ultraviolet deficiencies. Since some of these giants are stars for which little or no interstellar reddening is predicted, we attribute the observed deficiencies to the stars themselves.Many of the objects we observe do not have accurate ground-based published data regarding magnitude, color, and spectral type; new ground-based observations of these objects are required to ensure satisfactory interpretation of our results.
Stellar-wind theory for O and B stars
Authors: Solomon Philip M. 
Published: July 2016

The rocket-ultraviolet observations of strong Doppler-shifted absorption lines of Siiv, Civ, Nv and other ions in the spectrum of O and B supergiants clearly indicate a high velocity outflow of matter from these stars. The presence of moderate ionisation stages in the stellar wind is conclusive evidence that the flow cannot be due to a high temperature corona as is the case for the solar wind. It is shown that the driving mechanism for the hot-star mass loss is radiation pressure exerted on the gas through absorption in resonance lines occurring at wavelengths near the maximum of the star's continuum flux. In the upper layers of these stars the outward force per gram of matter due to the radiation pressure can greatly exceed the gravitational acceleration making a static atmosphere impossible.The problem of a steady-state moving reversing layer is formulated and the solution leads to predictions of mass-loss rates as a function of effective temperature and gravity for all hot stars. These results are in substantial agreement with the observations.
Geochemical problems in the production of the Venus clouds
Authors: Sill Godfrey T. 
Published: July 2016

Spectroscopic evidence is strong that the clouds of Venus are composed of ferrous chloride hydrate. At the surface of the planet it appears as though the vapor pressure of ferrous chloride may be quite low (10−6 atm), especially if such vapor is allowed to come to equilibrium with the other constituents of the Venus atmosphere. The formation of magnetite (Fe3O4) may be favored, and the spectrum of magnetite is shown in relation to the spectrum of the Venus cloud cover. The presence of ferrous chloride in the upper atmosphere may be due to a non-equilibrium condition.The spectrum of volatiles, such as the halides of mercury, are considered vs the albedo of Venus. The presence of these volatiles seems incompatible with the spectroscopic evidence. It is suggested that the planet has been depleted of its volatiles, as it has been depleted of its water.
Cloud motions on Mars
Authors: Baum W. A. , Martin L. J. 
Published: July 2016

A search of several thousand plates in the Lowell Observatory collection yielded 28 groups of plates on which the positions of well-defined transient bright spots (often assumed to be clouds) could be followed on a nearly daily basis. These groups of plates were from 15 different oppositions of Mars, starting from 1907 and ending with 1958. All but two of these spanned four nights or more, and the maximum interval covered was thirty nights. Whether they appeared to show motion or not, the successive positions and shapes of all apparently associated bright spots or clouds were plotted on Mercator projections with the use of a projection plate reader especially designed at the Planetary Research Center for planet image studies of this kind. Clouds near the limb were avoided.The 28 groups of plates yielded 95 cloud histories. More than half appeared to be relatively stationary. Others showed definite motion well in excess of observational error but sometimes followed paths that partly doubled back upon themselves. The mean velocity for non-stationary clouds was found to be 5.6 km per hour, and the most commonly occurring direction of motion was eastward, particularly at high latitudes. The range of velocities found by this mapping procedure is nearly an order of magnitude smaller than values that have been estimated earlier by others from visual observations. These earlier observations are evidently in error, unless there exist clouds at high elevation, visible only on the limb, that can move much faster than those that were mapped from this photographic survey. More clouds were found in the northern hemisphere than in the southern, and there seemed to be an avoidance of the relatively darker areas of the Martian surface. Certain regions seem to be more favored than others. A few recurrences at identical positions suggest the existence of related topographic features.
Gamma-Ray Spectrometry of Galactic Sources in the Energy Range 0.2–3.0 MeV
Authors: Bui-Van A , Vedrenne G. , Mandrou P. 
Published: July 2016

A low energy gamma-ray telescope (0.2–3 MeV) has been studied in our laboratory. It is made up of an active honeycomb collimator of Nai(T1), with a geometrical angular aperture of 1.5°, and of a detector composed of 73 Nai(T1) sticks (0.5 cm diam.–5 cm length) incorporated in a plastic gabarit used in anticoincidence.The directivity of the telescope is obtained at low energy by the collimator, and at higher energy by the directivity which exists in the gamma-ray interaction through the Compton and photoelectric effects. The electrons emitted in these interactions which are not contained in the sticks of Nai(T1) are detected by the plastic anticoincidence scintillator. Only laboratory tests are presented here, for the study of the galactic gamma-rays, however, the system must subsequently be protected by a 4 cm thick anticoincidence well. In fact the detector directivity enables a great increase in the signal to noise ratio to be expected without greatly increasing the thickness of the shielding.According to the results obtained the estimation of the minimum exposure time for the ‘Crab Nebula’ would be about 2h30m to have a signal at 1 MeV with 2σ of confidence above the background.
Survey On New Techniques for X-Ray Astronomy
Authors: Giacconi Riccardo 
Published: July 2016

The limitations imposed in X-ray astronomy observations by the use of sounding rockets with their inherent short time for observations and restricted payload capabilities will soon be surmounted when the new generation of X-ray experiments carried aloft by earth orbitting satellites is launched.In the early 1970's several payloads included in the spacecrafts SASA, OSOH, SAS C, OSO 1, UK 5 and ANS will perform high sensitivity surveys of the entire celestial sphere. As a result of these experiments we expect to: increase the sensitivity of our observations by a factor of approximately 100; to improve the measurement of location on all known sources and on newly discovered ones to an accuracy of ½ to 6 arc min; to acquire more definite information on rapid time variations of the X-ray sources; to measure the polarization of the incoming X-ray radiation to several per cent for the strongest sources; and, finally, to determine for the strongest sources the existence of emission lines or absorption edges to the accuracy required to confirm or disprove present theories of source of emission processes and interstellar absorption.Beyond these surveys a new generation of X-ray instrumentation utilizing focussing X-ray telescopes is in the planning stage. These instruments will yield a qualitative advance in the type of observations that can be performed. Location and structure of X-ray sources can be determined with these techniques to precisions of a few arc seconds to a limiting surface brightness of 10−14 erg/cm2 s (arc s2). Spectroscopy of the strongest sources can be carried out with energy resolutions λ/Δλ of 103 to 104. Polarization measurements can be carried out to a few per cent on the Crab and rapid varying events can be followed with a time resolution of 10−4 s.A summary of the instrumentation will be given from the point of view of the developments and improvements which are being carried out to achieve the observational goals mentioned above.
A Rocket-Borne X-Ray Spectrometer/Monochromator System for Mapping the Solar Corona
Authors: Acton L. W. , Catura R. C. , Culhane J. L. , Meyerott A. J. 
Published: July 2016

A rocket payload is being prepared for the purpose of examining the spatial distribution of line emission from two important ions, Ovii and Neix, in the solar corona. The payload will contain the following integrated set of instruments.(1) A pair of X-ray spectrometers utilizing KAP crystals of approximately 100 cm2 area.(2) An optical aspect camera with a 1 Å bandpass H-α filter to measure the location of the field of view of the X-ray systems on the sun through out the rocket flight.(3) A collimated proportional counter spectrometer operating in the 3 to 15 keV range.
On the determination of the oscillation frequencies in the meridian plane of galactic stellar orbits
Authors: Ollongren A. 
Published: July 2016

First a review is given of the general properties of orbits belonging to one family computed by numerical integration. Then the method by which it is possible to derive the ratio of frequencies of oscillation of an orbit which is topologically equivalent to a Lissajous figure is explained. It is shown that the assumption that the ratio of oscillations is a constant must be regarded as a first approximation. In a second approximation this ratio is taken to be variable.The discussion of the orbital inclinations during passage of the galactic plane for the computed orbits, suggests a periodic form for this variability, which would explain the occurrence of the main types of orbits found.
On nearly-commensurable periods in the restricted problem of three bodies, with calculations of the long-period variations in the interior 2:1 case
Authors: Message P. J. 
Published: July 2016

An analytical discussion of that case of motion in the restricted problem, in which the mean motions of the infinitesimal, and smaller-massed, bodies about the larger one are nearly in the ratio of two small integers displays the existence of a series of periodic solutions which, for commensurabilities of the typep+ 1:p, includes solutions of Poincaré'sdeuxième sortewhen the commensurability is very close, and of thepremière sortewhen it is less close. A linear treatment of the long-period variations of the elements, valid for motions in which the elements remain close to a particular periodic solution of this type, shows the continuity of near-commensurable motion with other motion, and some of the properties of long-period librations of small amplitude.To extend the investigation to other types of motion near commensurability, numerical integrations of the equations for the long-period variations of the elements were carried out for the 2:1 interior case (of which the planet 108 “Hecuba” is an example) to survey those motions in which the eccentricity takes values less than 0·1. An investigation of the effect of the large amplitude perturbations near commensurability on a distribution of minor planets, which is originally uniform over mean motion, shows a “draining off” effect from the vicinity of exact commensurability of a magnitude large enough to account for the observed gap in the distribution at the 2:1 commensurability.