bluuebunny/crossref_metadata_2025_split huggingface dataset:
Concurrent Astronomical Observations for Studying Continental Drift, Polar Motion, and the Rotation of the Earth
Authors: Markowitz Wm. 
Published: July 2016

The analysis of 66 years of concurrent latitude observations of the ILS shows that the mean pole has a secular motion which consists of a progressive component of about 0′′.0035/yr (10 cm/yr) along the meridian 65°W and a librational component (oscillation) of 24-year period along the meridian 122°W (or 58°E). Crustal displacements in latitude are not found within the errors of observation, about 1 cm/yr.Comparable, concurrent observations for time (longitude) have not been made but programs are being organized. From 30 to 50 years will be needed for detection of continental drift with PZT's and astrolabes if relative drifts in longitude of 3 cm/yr are occurring.
27. On the radiant distribution of sporadic meteors
Authors: Carrara N. , Consortini A. , Ronchi L. 
Published: July 2016

A research is described which had the purpose of deriving information about the physics and astronomy of sporadic meteors from the range distribution of radar echoes from meteor trails experimentally observed under given conditions.The method is based on the comparison of the experimental distribution with a number of different theoretical distributions, corresponding to different sets of assumptions about the characteristics of sporadic meteors and the law of trail formation.The quantities which can be derived by this method are: (1) the distribution of heliocentric radiants, (2) the type of meteors (stone, iron, dustballs), (3) the distribution of heliocentric velocities.In the present paper are described the results of the first part of the theoretical computations. Evidence is obtained that, in order to fit the experimental curve, both the uniform distribution of heliocentric radiants over the celestial sphere and in the plane of the ecliptic must be taken into account.
33. Meteor shower mass distribution from radar echo counts
Authors: Elford W. G. 
Published: July 2016

Theoretical hourly rates of radar echoes from meteor showers observed with narrow- and wide-aperture systems are calculated in terms of equipment parameters and the distribution of the number of meteors as a function of mass. From a comparison of the echo rates in selected range intervals, it is shown that it is possible to determine the value of the exponent in a simple inverse power flux law.The effect on the echo rate of a change in the value of the exponent in the flux law with magnitude is described and the probability of detecting showers at different stations is discussed.It is suggested that simple radar echo counts in several range intervals can be used to determine the mass distribution of meteor showers over a range of two or three magnitudes above the limiting magnitude of the system. The analysis is applied to some observations made at Christchurch and Ottawa.
Origine des régions actives solaires ‘anormales’
Authors: Martres M. J. 
Published: July 2016

Solar active regions are considered ‘anomalous’ when they belong to magnetic classes γ,βγ and βf-αf. The study of the solar activity of the region where, later on, these groups are born shows an evident correlation between the presence of an old active center and the complexity of the new active region.It is found that the complexity is greater if the old active center is younger, and the superposition better. We also observe that the birth of anomalous sunspots groups occurs much more frequently on the western side of the magnetic inversion line of the old center.When the birth of an active center occurs outside and on the West of the faculae, we observe the weakly anomalous groups βf-αf. The ‘perturbation’ decreases with distance and is extended at least to 10 heliographic degrees of the boundaries of the old faculae.
On the magnetic structure of an active region
Authors: Ermakov F. A. , Mogilevsky E. I. , Shelting B. D. 
Published: July 2016

(1)A scheme of magnetic-field generation in an active region within the subphotospheric convective zone is discussed. Magnetic-field amplification is considered to result from the interaction of the local cyclonic motion and the turbulent motion of the subphotospheric plasma.(2)A model of the magnetoplasma of an active region is considered consisting of a current-free magnetic field, whose lines of force stretch deeply under the photosphere in the form of subgranules (force-free fine-scale plasma elements). The explanation of some peculiarities in the development of an active region with the considered structure is discussed.(3)Some peculiarities of the general structure of the magnetic field and the motion within photosphere and chromosphere obtained by the analysis of observations with the IZMIRAN two-channel magnetograph is discussed.
Analysis of some solar flares from optical, X-ray, and radio observations
Authors: Falciani R. , Landini M. , Righini A. , Rigutti M. 
Published: July 2016

Using an improved isodensitometric technique it has been possible to study in great detail the photometric structure and the evolution of eight flares. A comparison has been made between the evolutive curves and the ones obtained from measurements of solar X-rays and radio fluxes at λλ 3·2 and 21 cm.A reduction of the flare areas (and of the emitted energies) before the flash phase and a continuous pulsation of the flare have been observed. Further it seems that the flares associated with radio bursts or X-ray events are those which show regions of a sufficiently high intensity, the emitting areas not being a very important parameter.The correlation in time between the various examined aspects of the AR seems to indicate that the sequence for the beginning of the different phenomena is, in general: optical flare, X-ray events, radio events.
80 MHz Radioheliograph Evidence on Moving Type IV Bursts and Coronal Magnetic Fields
Authors: Smerd S. F. , Dulk G. A. 
Published: July 2016

The characteristics of 12 moving type IV bursts observed with the 80 MHz radioheliograph at the Culgoora Observatory between February 1968 and April 1970 are summarized.Three classes of moving sources can be recognized; they are described as: (1) Expanding arch; (2) Advancing front; (3) Isolated source.The first class has been identified (Wild, 1969) with the expansion of a magnetic arch or loop; the second class is here identified with an advancing MHD disturbance which may accelerate the radiating electrons in situ when moving at greater than Alfvén speed; the third with solar ejecta in the form of magnetized plasma clouds, or plasmoids. In all cases the radiation mechanism is probably synchrotron radiation from mildly relativistic electrons; energies in the range ∼0.1 to ∼1 MeV could account for the observed strong circular polarizations.With an expanding magnetic arch, source and magnetic-field movement are inseparable; the field remains a closed loop throughout the event. The MHD front probably moves largely along and the plasmoids between the open magnetic-field lines of unipolar regions or helmet structures. In the latter case it is the internal magnetic field – possibly toroidal – of the moving plasmoid that determines the polarization of the synchrotron radiation. A preliminary comparison of moving type IV sources with Newkirk-Altschuler maps of coronal magnetic fields shows suitably located closed loops for 2 events identified as expanding magnetic arches and unipolar open field lines along the path of a moving source identified as a plasmoid.
Intergalactic Matter and Radiation and its Bearing on Galaxy Formation and Evolution
Authors: Burbidge G. R. 
Published: July 2016

An up-dated review is given of the evidence for the presence of intergalactic matter and radiation in the Universe. It is concluded that the only important constituents which may make a sizable contribution to the total mass-energy are intergalactic gas and condensed objects with a very high mass-to-light ratio. If the QSOs are not at cosmological distances, cold atomic hydrogen may still be the most important constituent and may contribute much more mass than do the galaxies. The X-ray observations still do not unambiguously show that very hot gas is present, though it is very likely on general grounds that some hot gas is present in clusters of galaxies.The question of whether or not large amounts of matter, enough to close the Universe, are present, remains unsettled. From the theoretical standpoint the answer depends almost completely on the approach taken to the problem of galaxy formation and to the cosmological model which is favoured.
Differences Between Galaxies
Authors: Van Den Bergh Sidney 
Published: July 2016

It is pointed out that the metallicity of galactic and extragalactic globular clusters correlates with the density of the regions in which they were formed. Within individual galaxies the regions of highest density have the highest metallicity.Some of the differences in family traits between the globulars in the Andromeda Nebula, the Galaxy and the Magellanic Clouds might be understood if the M31 cluster system is ~ 1 × 109 yr older and the SMC cluster system ~ 1 × 109 yr younger than galactic globular clusters.
TD1A Satellite Spectroscopic Observations of Jupiter in the Ultraviolet
Authors: Duysinx R. , Henrist M. 
Published: July 2016

Three spectra of Jupiter were recorded by TD1A satellite between 1350 and 2600 Å. From these data, the geometrical albedo of the planet was computed.From 2600 to 2100 Å, the value of the albedo matches the simple diffusing models of Jupiter's atmosphere (Greenspan and Owen, 1967).From 2100 to 1800 Å, a broad absorption can be assigned to NH3 molecule (2168 Å transition).Another absorption commences below 1800 Å. The absorbing molecule involved will be determined at a later date.
Galactic and extra-galactic radio frequency radiation due to sources other than the thermal and 21-cm emission of the interstellar gas
Authors: Brown R. Hanbury 
Published: July 2016

At wave-lengths greater than about one metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form:
where TA is the equivalent black-body temperature of a region of sky and A is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore the value of TA is about 1050 K at 15 m and thus greatly exceeds the electron temperature expected in H 11 regions.At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 m to 10 m where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.
Comparison of the galactic system with other stellar systems
Authors: Oort J. H. 
Published: July 2016

A comparison of the Galactic System with other stellar systems might be based on:
(a)the regular aspect (the population 11);(b)what we might call the semi-chaotic aspect, presented by the gas and the other population 1 objects;(c)the spherical corona of continuous radio-emission.As far as (a) is concerned we are not yet in a position to say very much. The only type of objects of extreme population 11 that we have recognized with certainty in the Galactic System as well as in other comparable systems are the globular clusters. They are very incompletely known in the Galaxy, perhaps somewhat more completely in the Andromeda nebula, but few systematic studies have been made in other systems. So far as we can tell, the Andromeda nebula and the Galactic System are comparable in the number and general distribution of globular clusters.
The Observed Characteristics of the Local Magnetic Field
Authors: Whiteoak J. B. 
Published: July 2016

The main investigations of the local magnetic field are reviewed and are found to contain some conflict in interpretation. At radio wavelengths, studies have been made using both the Faraday rotation of the polarized radiation from extragalactic sources and pulsars, and the polarization of the galactic background radiation. With the former type of observation, although more data are available for extragalactic sources, any interpretation may be complicated by the influence of distant field structure. The results are consistent with a large-scale field parallel to the galactic plane, with a field strength of about 2 µG, and which is directed towards l=90°. This field contains irregularities in direction and strength on a scale of about 100–200 pc. The polarization of galactic background radiation may yield the most detailed information about the local field structure – the results to date show loops of magnetic fields extending along the radio spurs.The interpretation in terms of small-scale irregularities embedded in a large-scale field parallel to the galactic plane differs from that proposed to explain the optical polarization of starlight, in which a helical field configuration near the Sun was preferred to a more disordered pattern.
Polarization Variability of Some Compact Radio Sources
Authors: Komesaroff M. M. , Milne D. K. , Rayner P. T. , Roberts J. A. , Cooke D. J. 
Published: July 2016

Figure 1 shows observations for four sample sources from the Parkes 5 GHz polarization monitoring programme. Interesting features illustrated include
•Sudden changes of the position angle of the linear polarization by ≳ 70° in PKS 0537-441 and 1253-055 (3C279).•A linear increase in the position angle of the polarization of PKS 2134+004 through 70° over 3/12; years.•Distinct bursts of circular polarization in PKS 0430+052, 0537-441 and 1253-055. In PKS 0430+052 (3C120) such a burst coincides with the possible superluminal expansion (Walker et al., 1981). In PKS 1253-055 (3C279) a burst of circular polarization is currently occurring at a time of very low linear polarization.
Time-Dependent X-Ray Observations of Wolf-Rayet Binaries with 0-Type and with Suspected Compact Companions
Authors: Moffat A.F.J. , Firmani C. , McLean I.S. , Seggewiss W. 
Published: July 2016

Each of four WR binaries has been observed in the 0.1 −5 keV range on four consecutive days for a total of ∼ 104 sec with the IPC on the Einstein Observatory. One of the stars is the well-known WN5 + 06 binary V444 Cyg; the other three have suspected compact companions; all have periods close to four days.Neither HD 197406 (WN7) nor HD 96548 (WN8) was detected; hence Lx (0.5–3.0 keV) ≲ 1032 erg s−1, which is on the low side, even for 0-stars. EZ CMa (WN5) and V444 Cyg are moderately strong, variable X-ray sources with Lx (0.5–3.0 keV) ≃ 1033 erg s−1, kT ≃ 0.5 keV and NH ≃ 1022 cm−2. These values suggest that the X-ray flux arises in the outer part of the wind. The variable component may be produced by collision of two winds.There is no evidence of harder X-rays coming from accretion onto a compact star. Nevertheless, the presence of a collapsar is not excluded at hv ≲ 5 keV, where absorption in the WR wind would likely reduce the X-ray flux to a level which is masked by the flux coming from the hot stellar wind.
Variability of Some Be Stars on High-Resolution, High S/N Spectra
Authors: Hubert A. M. , Hubert H. , Dagostinoz B. , Floquet M. 
Published: July 2016

Rapid variability in Be stars could be understood by non radial pulsations or by rotation of an inhomogeous surface brightness distribution…The structure and the variability of the Hα and of the HeI λ6678 lines have been investigated with an optical fiber spectrograph and a CCD camera. The signal to noise ratio, measured in the continuum, is between 300 and 500.Weak changes in the Hα emission line profile of γ Cas have been detected on time-scale of hours and days. This line has an asymmetric profile exhibiting only one blue-shifted maximum while the HeI λ6678 has a double-peak emission, superimposed to the photospheric contribution, with a violet to red peak ratio V/R >1.The Hα emission line of φ Per exhibits a complex structure with significant changes in its core, from night to night and on a short time scale <lhr. The HeI λ6678 presents a blue-shifted asymmetric emission (red-winged) superimposed to the photospheric contribution.Furthermore the Hel photospheric line λ6678 of the B6 star o And has presented notable variations in its profile during the 2 observational campaigns, which do not seem correlated to the photometric period of 1.57 day.
Digitally Recorded Type I Bursts and Some Theoretical Aspects of Continuum and Burst Generation
Authors: Kattenberg A. , van Hees R.M. , van Nieuwkoop J. 
Published: July 2016

In the first part we present the analysis of digitally recorded type-I bursts. The reduction procedure is described and some typical examples and results are presented.In the second part we propose a model for type-I emission, compatible with low magnetic field strengths.Incoherent langmuir waves, spontaneously emitted by trapped fast electrons are converted to transverse radiation by coalescence with low frequency whistlers. Recurrent upper hybrid instability in strong m.h.d. pulses explains the bursts in this model.
Temporal and Spectral Investigation of Two Thermal Impulsive Microwave and X-ray Bursts of 1972 May 18 for the Determination of Source Parameters
Authors: Wiehl H.J. , Schoechlin W.A. 
Published: July 2016

SummaryIn order to study the dynamical burst process we investigated two bursts of 1972 May 18 at 14:05 UT and at 16:16 UT in the microwave (1–15 GHz, Berne and Sagamore Hill), the hard X-ray (28–102 keV, ESRO TD-1A) and the soft X-ray (0.5–20Å, Solrad 11) frequency ranges. For both flares a thermal interpretation was adopted.
37. Galactic radio emission and the distribution of discrete sources: Introductory Lecture
Authors: Brown R. Hanbury 
Published: July 2016

At wave-lengths greater than about 1 metre the majority of the radio emission which is observed from the Galaxy cannot be explained in terms of thermal emission from ionized interstellar gas. This conclusion is widely accepted and is based on observations of the equivalent temperature of the sky and the spectrum of the radiation. The spectrum at metre wave-lengths is of the general form:
where TA is the equivalent black-body temperature of a region of sky and λ is the wave-length. The exponent n varies with direction but lies between about 2·5 and 2·8, and is thus significantly greater than the value of 2·0 which is the maximum to be expected for thermal emission from an ionized gas. Furthermore, the value of TA is about 1050K. at 15 metres and thus greatly exceeds the electron temperature expected in H 11 regions.At centimetre wave-lengths it is likely that the majority of the radiation observed originates in thermal emission from ionized gas; however, the present discussion is limited to a range of wave-lengths from about 1 to 10 metres where the ionized gas in the Galaxy is believed to be substantially transparent and where the origin of most of the radiation is believed to be non-thermal.
Accurate spectral classification by objective-prism techniques
Authors: Bidelman W. P. 
Published: July 2016

The performance of moderate dispersion objective-prism equipment, and in particular that of the 10°-prism combination of the Michigan Curtis Schmidt, has been evaluated through a direct comparison of objective prism and slit spectrograms of a number of standard stars. The results suggest that one should seriously consider using objective-prism equipment rather than slit spectrographs for large scale programs of accurate classification of fairly bright stars.A survey of 171 high-quality Curtis Schmidt plates covering 105 different fields has resulted in the discovery of 46 new peculiar A stars and 66 new metallic-line stars. In addition, 17 stars of later type have been classified as “weak-metal” objects. The most interesting stars detected were HD 3473, which is greatly overabundant in both silicon and magnesium, and the G-type star HD 2665 (mv= 7 · 6), which has subsequently been found to have a radial velocity of approximately – 390 km/sec. This is the brightest star known to have such a large radial velocity.(The above paper appears in full in the volume entitledBasic Data Pertaining to the Hertzsprung-Russell Diagram, a symposium dedicated to Ejnar Hertzsprung and sponsored by the U.S. Office of Naval Research, to be published by Pergamon Press asVistas in Astronomy, vol. 8).
Equivalent widths of Hγ in the Magellanic Clouds
Authors: Hutchings J. B. 
Published: July 2016

J. B. Hutchings has measured equivalent widths of Hγin the large stock of Radcliffe spectra of stars in the Magellanic Clouds. The maximum equivalent width occurs at spectral type Fo due to the very low pressures in the atmospheres of these supergiants. Curves relating equivalent width (reduced to types Ao and B3) with apparent magnitude are presented and agree reasonably well with the corresponding galactic calibration of absolute magnitudes. Among the stars of highest luminosity, measured equivalent widths may be affected by both (a) emission, and (b) presence of expanding shells.Hutchings has also detected in some of these spectra the presence of 4430Å absorption originative within both Clouds.
The Class 0 Outflow Hammered Out?
Authors: Smith Michael D. , Völker Roland , Suttner Gerhard , Yorke Harold W. 
Published: July 2016

Dense molecular jets cutting through dense molecular clouds are simulated here using a ZEUS-type hydrodynamics code extended with molecular physics. H2 ‘hot snapshots’ and CO ‘historical views’ are nicely modelled with overdense uniform jets. Attention is drawn to some remaining hot problems: observed jet knots are bow shaped, bipolar outflows can be highly asymmetric, some proper motions within jets are enigmatically low and H2 excitation can be exceedingly uniform.We present the Hammer Jet, in which the nozzle introduces high velocity variations, as well as a strong ripping and spray action. Prominent jet bow shocks in H2 and CO emission lines are then produced. Wide tubular CO structures with concave bases show up. Proper motions are simulated. The asymmetries are modelled by jet break-out from a molecular core into a diffuse atomic environment.
Research into astronomical refraction - today and tomorrow (A Survey Paper)
Authors: Teleki G. 
Published: July 2016

SummaryProceeding from the present-day and future needs of astrometry, current researches into astronomical refraction as well as its prospective development are analysed. Particular attention is dedicated to the constructing of new refraction tables, determination of the refractional influences by way of experiments, site selection of the observing stations and to the preventive measures to be taken at them. Need and usefullness are emphasized of the cooperation of experts specialized in astronomical, terrestrial, photogrammetric, radio and other kinds of refractional influences.
Possibilities of increasing the accuracy in the determination of refractional angles with Tengström's IDM
Authors: Milewski J. 
Published: July 2016

The main purpose of the IDM research of prof. Tengström was to confirm the possibility of determining instrumentally the refraction angle in the field even over long distances.An appreciable increase of the accuracy could only be achieved by further improvement of the instrument. Even with the first laboratory model it seems possible to achieve an increase of the accuracy in the final results. This paper discusses the above possibilities and proposes some methods to achieve this improvement in the accuracy.