bluuebunny/crossref_metadata_2025_split huggingface dataset:
The effect of compression and expansion of plasma on the generation of synchrotron radiation
Authors: Gopasyuk S. J. , Erushev N. N. , Neshpor Y. I. 
Published: July 2016

We consider the variation of the synchrotron-flux density of relativistic electrons with the power law spectrum when the region of generation of this emission initially experiences a homogeneous compression and then an expansion. Ionization losses have been taken into account. The velocities of compression and expansion have been taken as constant. It is shown that in the cases of compression or expansion the flux density at a given frequency changes asS(t) ~ S0Kγ(t)where S0 = flux density before the compression, γ = index of the power law spectrum, K(t) = (H(t))/(H0 (t = 0)), and H is the magnetic-field strength. In the case of compression K(t) > 1·0 and in the case of expansion K(t)< 1·0.The results obtained are applied to an explanation of the increasing and decreasing parts of impulsive bursts of the centimeter range. Such a description of the impulsive bursts has allowed us to estimate both the parameters of the radiating region and the parameters of the differential energetic spectrum of relativistic electrons.
The Magnetic Fields at Different Levels in the Active Regions of the Solar Atmosphere
Authors: Tsap T. T. 
Published: July 2016

The strengths of the longitudinal magnetic fields recorded at different depths of active regions with a double magnetograph of the Crimean Astrophysical Observatory are compared.The recordings of the magnetic fields were made in the lines Fe Iλ5250Å, Ca Iλ6103Å, Na I D1, BIIλ4554Å, Mg Iλ5184Å, Hα, Hγ, Hδ.It is shown, that there is a close correlation between the longitudinal magnetic field at different levels.
On the Circular Polarization in Active Regions
Authors: Wiehr E. 
Published: July 2016

Advantages of ‘circular polarimetry’ (determination of the Stokes parameter V) in active regions as compared to ‘elliptical polarimetry’ (determination of all Stokes parameters) are discussed:
(1)Complicated and doubtful reduction procedures by means of line formation theory generally are needed for ‘elliptical polarimetry’. This is not the case for ‘circular polarimetry’.(2)Even if the difficulties (1) could be removed, ‘elliptical polarimetry’ would not help to determine the total magnetic vector outside the disc center. This is due to the fact that the azimuth φ of the linear polarization is only defined for 0° ⩽ φ < 180°. When converting the measured inclination Ψ to the line-of-sight into the true inclination γ to the solar surface normal for active regions outside the disc center, the ambiguity of φ always yields an ambiguity of γ. The normal field component and thus the flux can therefore not be determined without making an important assumption on the unknown field structure (see Wiehr, 1970a).(3)For active regions near the disc center, however, where the difficulty (2) disappears, ‘circular polarimetry’ is sufficient for the determination of the normal field component and flux. It furthermore avoids the difficulty (1).
The Relation Between Dashes and Flares (Physical Nature of the Dash Phenomena)
Authors: Kuznetsov D. A. , Shpitalnaya A. A. 
Published: July 2016

The phenomenon of dashes in the eruptive loop prominences is found to represent the part of the solar flare process which includes all the levels of the Sun's atmosphere. For 75% of observations a coincidence of dashes and flares in space and time was discovered. The rest of the dash observations may be interpreted as the excitation of dashes by the flares arising outside the limb.Following the solar flare theory of Alfvén and Carlquist, the possibility to interpret the dashes as the eruptive instability of the pinch-effect is discussed. The computation of flare-current magnetic field gives the value H ∼ 3·104 oersted, its order being in agreement with the observed value.
Distribution of the Magnetic Force in the Surface Layers of Sunspots
Authors: Jakimiec J. 
Published: July 2016

At the beginning the problem of constructing the three-dimensional magnetohydrostatic models of the photospheric layers in sunspots is discussed in some detail. It is pointed out that the construction of such models by solving the set of equations of magnetohydrostatics cannot be effectively carried out.In order to solve the difficulties a suitable method of determining the distribution of the magnetic force in sunspots from measurements of the magnetic field has been worked out. Tentative results of the computations are presented.General features of the distribution of the magnetic force in the photospheric layers of stable sunspots are discussed. It is pointed out that significant magnetic forces are necessary in the penumbra; they secure its transversal equilibrium, but are rather unimportant for its vertical structure. And it is quite probable that the magnetic field in the umbras of stable spots is nearly potential or force-free down to the photospheric level.
Optical and Radio Observations of Large Scale Magnetic Fields on the Sun
Authors: Daigne G. , Lantos-Jarry M. F. , Pick M. 
Published: July 2016

It is possible to deduce information concerning large scale coronal magnetic field patterns from the knowledge of the location of radioburst sources.As the method concerns active centers responsible for corpuscular emission, the knowledge of these structures may have important implications in the understanding of corpuscular propagation in the corona and in the interplanetary medium.
Optical Observations of Nuclei of Galaxies
Authors: Ulrich Marie-Helene 
Published: July 2016

Several problems concerning the nuclei of galaxies are particularly interesting at present, either because new data have become available from advances in observational techniques, or else because recent observations suggest that earlier conclusions should be revised. These problems are discussed in this article.Spectrophotometry in the near infrared shows that the late-type stars in the nucleus of M31 are mostly late giants; the M/L ratio in the nucleus is approximately 15, a value in agreement with that calculated independently from the velocity dispersion of the stars.Infrared emission at 10µ has now been detected in 50 galaxies; the Seyfert-type galaxies are the brightest at 10 µ and there is evidence of variations of the 10 µ flux in NGC 4151, which rules out re-radiation by dust as the mechanism of infrared emission. In each of the galaxies NGC 253 and NGC 3034 an infrared source of dimension ~ 200 pc is present in the centre which coincides in position and dimension with the central component of the radio source at 1415 MHz; since both galaxies are rich in dust and in early-type stars it is plausible that, in these cases, re-radiation by dust is the origin of the infrared emission. Most of the other galaxies detected at 10 µ are spirals with intense and narrow emission lines.Comparison of the optical and radio properties of nuclei of galaxies show that galaxies with compact nuclear radio sources are more likely to have optical spectra with emission lines than are galaxies without central radio sources. This correlation holds for elliptical and spiral galaxies. Its cause is not understood at present.The relatively accurate profiles now available for the permitted lines of several Seyfert galaxies show that mass motions are the main broadening agent for these lines. Variations of line intensities have been observed in several Seyfert galaxies. The most likely explanation of these variations is that they are due to the variations of the photoionizing flux; in some cases, however, weakening of the permitted lines could be caused by high-velocity mass motions present in the region emitting the broad component of these lines.From the investigation of the relatively nearby galaxies it is estimated that at least 5 % of galaxies have expansion motions or non-thermal optical fluxes.
Recent Radio Studies of Bright Galaxies
Authors: Oort J. H. 
Published: July 2016

Some results are discussed of recent – still largely unpublished – high-resolution studies of bright spirals, both in the radio continuum and in the 21-cm line radiation. Special emphasis is given to observations of M51, M81 and NGC 4258.The most important new data are (1) Estimates of the contrast in gas density between arms and interarm regions (M81 and M101); the contrast appears to be quite strong. It provides an important parameter for the density wave. (2) Evidence for a pronounced decrease of gas density along the arms when these are followed towards the centre. Considerable line radiation is observed from outer regions where the optical intensity of the arms is very low. (3) Extension of rotation curves to larger distances from the centre. (4) Data on the motions in the spiral waves. (5) Determination of the shift between synchrotron and optical arms, providing direct evidence for the formation of stars as a consequence of the passage of the interstellar gas through the spiral density wave. From the shift measured in M51 the formation time is found to be roughly ten million years. If the data for (2) are ascribed to the depletion of the gas by star formation, the average net fraction of the gas consumed in star formation is found to be between 2% and 3% per passage through the spiral wave (Table I). (6) Separation of nuclear and disk synchrotron radiation in spirals. (7) Evidence for a recent expulsion of about 108 solar masses from the nuclear region of NGC 4258.
The Spectrum of Mars in the Region 1800–3200 cm−1
Authors: Beer Reinhard 
Published: July 2016

During the 1971 opposition of Mars, new infrared spectra covering the region 1800–3200 cm−1 (3.1–5.6μ) were taken at a resolution of 0.095 cm−1 using a Connes'-type Fourier spectrometer on the 2.7 m telescope, McDonald Observatory. Spectra were obtained near 6° and 33° phase and were calibrated against the Sun, standard stars and an internal black body.No new trace constituents have, as yet, been found in the spectra, but several previously unobserved combination and isotopic bands of CO2 are visible. It has also been found possible to fit fairly well defined kinetic temperatures and Bond albedos to the two sets of data. The kinetic temperatures have been determined by a new technique. It is found that the albedo at 33° phase, which was determined a few days after the onset of the great dust storm of 1971, was significantly higher than for the clear atmosphere. The explanation for this phenomenon must await detailed radiative transfer calculations for a dust-laden atmosphere.
The Saturnian ‘Gas-Doughnut’ Hypothesis
Authors: McDonough Thomas R. , Brice Neil 
Published: July 2016

It is hypothesized that constituents escaping the atmosphere of Titan are unlikely to have sufficient velocity to escape from Saturn. Thus most of the material will enter into elliptical orbits which, at some point, cross Titan's orbit at a small angle. In total, this matter will form a ‘doughnut’ shaped feature, roughly centered on Titan's orbit and having dimensions of about 20 Rs (Saturn radii) in the Saturnian-equatorial plane and 10 Rs normal to this plane. It is assumed that the material is lost from the doughnut when it is ionized or is recaptured by Titan's atmosphere. The upper limit on the density of hydrogen in the ring is estimated to be about 103 cm−3, with up to 99% of the particles in the doughnut being recaptured by Titan.A brief summary of the work which has been done on this problem is given, and areas needing further research are suggested.
Relation Between Light Variations of Solar System Satellites and Their Interaction with Interplanetary Medium
Authors: Blanco C. , Catalano S. 
Published: July 2016

The behaviour of the available light curves of Jupiter and Saturn satellites is shown to change steadily from inner to outer satellites.The change in reflectivity of satellites with orbital motion could be explained assuming that dark meteoroidal material accumulates on a given portion of the satellite's surface, which was once mainly covered with ice or snow. The preferential impact location on the satellite's surface could be a consequence of the perturbing action of the planet on the motion of interplanetary material.
The Theory of Radiation Driven Stellar Winds and the Wolf-Rayet Phenomenon
Authors: Abbott David C. 
Published: July 2016

Peter Conti has a tradition of always talking about 0-type stars at Wolf-Rayet symposia, and Wolf-Rayet stars at 0 star symposia. Since there is no well-developed theory for the origin of the winds of WR stars, it is my pleasure to join Peter's tradition, and to talk mainly about the theory of radiation driven winds in OB stars. The advantage of OB stars is that there exists a fairly complete wind theory, which agrees well with the available observations. The question is, can the mass loss observed from Wolf-Rayet stars be explained by a version of this wind theory which is scaled to the conditions found in the envelopes of Wolf-Rayet stars? The topics I consider are:
—The calculated radiation pressure in OB stars, and its dependence on temperature, density, and chemical composition.—A comparison between predicted and observed mass loss rates and terminal velocities for OB stars.—The applicability of the standard radiation driven wind models to Wolf-Rayet stars.—Speculations on how Wolf-Rayet stars achieve their enormous mass loss rates within the context of the radiation pressure mechanism.
On the Properties of Wolf-Rayet Stars and Their Mass Loss
Authors: Panagia N. , Felli M. 
Published: July 2016

From consideration of the observed properties of the envelopes produced by mass loss in WR stars we find that:
a)The velocity at the optical photosphere is in the range 200–800 km sb)The effective photospheric radius for the continuous radiation capable to ionize helium twice (γ < 228 A) is typically 5 to 15 times the optical photospheric radius.c)The radiation temperature in the Lyman continuum (γ < 912 Å) is around 5 × 104K. Therefore, most of the stellar radiation is emitted in the far UV and the total luminosity is considerably higher than currently estimated.d)Multiple scattering (N ≃ 20) of radiation in the interval 228–504 Å can provide most of the momentum needed to accelerate the wind up to the observed terminal velocities.
Time-Variations of 17GHz Radio Bursts by Multi-Source Structures
Authors: Kosugi Takeo 
Published: July 2016

Four multi-source radio bursts observed with the new 17GHz interferometer at Nobeyama are analyzed and presented from the point of view of their time-variations.Three of them (Sep. 6, 1978; Oct. 9, 1978; and Feb. 17, 1979) were essentially of an impulsive nature and all showed distinct double-source structures. Their polarization structures and time-variations are discussed and compared with type III and type II burst occurrences. The results of the comparison suggest either that electron accelerating regions moved across magnetic lines of force or that a rapid magnetic field rearrangement occurred near an accelerating region.A quite different type of multi-source radio bursts was observed on Nov.10,1978. It had a long duration of several hours and was associated with type IV bursts at metric and decimetric wavelengths. At least five radio sources were observed to appear at 17GHz. A detailed description of this event is presented in comparison with the evolution of both Hα-flare and type IV bursts.
Flare of 1970 March 01: A Review and Further Evidence for Adiabatic Heating
Authors: Mätzler C. , Wiehl H.J. 
Published: July 2016

SummaryThe microwave and hard-X-ray burst of 1970 March 01, 11:27 UT was found to originate from a common thermal plasma with a maximum temperature of 57 keV. The low coronal plasma with an average electron density of about 3.108cm−3 covered a projected area of 5.1018 cm2. In Fig. 1 the time profiles of the emission measure and the temperature are compared with the 10.5 GHz flux while Fig. 2 shows the reversible relationship between the hard X-ray emission measure and temperature during the impulsive phase. The arrows indicate the direction of increasing time. The dashed-dotted line, representing an adiabatic process with an index χ = 5/3, agrees well with the observations showing a compression followed by an expansion (Mätzler et al. 1978).
Absolute Magnitudes and Intrinsic Colours of Non-Supergiant Be Stars
Authors: Kozok J. R. 
Published: July 2016

101 normal Be stars, probable members of 56 galactic clusters and OB-associations, and more than 20 extreme Be stars in the Large Magellanic Cloud were used to derive intrinsic colours of 09-B9 (III-V)e stars. Furthermore, the correlation between the intrinsic colour (U-B)0 and the absolute magnitude of non-supergiant Be stars was confirmed to be

and
The aim of the present investigation is to enlarge the basis for the determination of intrinsic colours and absolute magnitudes by providing a large sample from the southern sky.
The Overall Abundances of Globular Clusters
Authors: Bell R. A. 
Published: July 2016

At a meeting on globular clusters held five years ago, Zinn (1981) made the following comments:“In summary, there are clearly large differences in metal line strength between 47 Tuc giants and the giants in the other clusters. These differences suggest that there are substantial differences in metal abundance, which conflicts with the measurements obtained from echelle spectrograms, and there appears to be no simple way of reconciling these results. Until this is done, the metallicity scale for globular clusters hangs in limbo.”
Interstellar Matter in Globular Clusters
Authors: Roberts Morton S. 
Published: July 2016

“Is there any point to which you would wish to draw my attention?”“To the curious incident of the dog in the night-time.”“The dog did nothing in the night-time.”“That was the curious incident,” remarked Sherlock Holmes.Memoirs of Sherlock HolmesThe source for intracluster matter is seen in various mass loss processes ongoing within clusters and is supported by the theoretical need for mass loss to explain the morphology of cluster colormagnitude diagrams. A variety of techniques ranging from X-ray to radio wavelengths have been employed to search for such matter but with few exceptions has not been found. The amount of material expected to collect between cleansing passages through the galactic plane has variously been estimated at between ∼ 102 and ∼ 103 M⊙. In contrast, observed upper limits for many clusters are well below these values, often > 1 M⊙. The few detections are at levels of ≲10−2 M⊙.
The Integrated Spectra of Metal-Rich Galactic Globular Clusters: A Two-Parameter Family
Authors: Rose James A. , Tripicco Michael J. 
Published: July 2016

Integrated photographic image-tube spectra have been obtained for the central regions of a number of metal-rich Galactic globular clusters with a wavelength resolution of 2.5 å over the wavelength region λλ3400-4500 å. The spectra have been analyzed using a variety of quantitative spectral indices that compare the strengths of neighboring absorption features. Our main result is that two parameters are needed to describe the integrated spectra of metal-rich globular clusters. The second parameter is manifested in two ways:(1) In a diagnostic diagram sensitive to surface-gravity the metal-rich clusters do not form a well-defined linear sequence. Instead, we find large differences from one cluster to another in the mean surface gravity of the stars contributing to the integrated light at 4000 å. It appears that the relative amounts of light contributed by dwarfs and giants varies considerably from one cluster to another.(2) In a diagram that discriminates CN strength we find large differences from one cluster to another in the mean CN strengths of clusters having similar “spectral type”. It is inferred that the mean CN anomaly varies from one cluster to another and that the anomalous CN strengths are present in main sequence stars as well as in giants.The above two second parameter effects are shown to be strongly correlated in the sense that the “dwarf-dominated” clusters have the largest CN anomalies. Hence, our study indicates that no more than two independent parameters are required to explain the integrated spectra of metal-rich globular clusters.Details of the above findings can be found in Rose and Tripicco (1986, A.J. 92, 1610).
High Precision Photometry of 10,000 Stars in M 3
Authors: Buonanno R. , Buzzoni A. , Corsi C. E. , Pecci F. Fusi , Sandage A. R. 
Published: July 2016

A new color-magnitude diagram for M 3 is presented. 10,000 stars have been measured down to V = 22 with an internal accuracy better than 0.03 mag to get complete and very accurate samples over well defined areas.More than 10,000 stars have been measured down to V = 22 in two different areas. In the first, with 3.5 < r < 6.0 arcmin, photometric completeness has been achieved down to V = 21.5 and an algorithm to correct for losses due to unrecoverable crowding and blending has been experimentally computed. In the second, within a square field of 15 × 15 arcmin, completeness has been extended only to V = 18, well below the horizontal branch.Many tests made on the data guarantee an internal photometric accuracy better than 0.03 mag at V = 21. Therefore, both the total population of each branch and the relative star-number ratios are “bona fide” representatives of the corresponding evolutionary time-scales. Here we simply present: 1) the color-magnitude diagram (see Fig. 1) obtained from the reduction of a wide collection of Palomar plates; 2) a table which presents the contribution of the various branches to the integrated cluster light; 3) the preliminary indication that, within the annulus we have considered, the blue stragglers seem to be slightly less centrally concentrated than the subgiants in the same magnitude interval.
Non-circular motions in the galaxy as exhibited by very young stars
Authors: Weaver H. F. 
Published: July 2016

I. Expansion of the Gaseous and Stellar Components of the GalaxyIf the gaseous component of the Galaxy is expanding as observed by Rougoor and Oort in the centre of the Galaxy and as postulated by Kerr in his early interpretation of spiral structure, the expansion must represent a phenomenon of fundamental importance in the Galaxy which has, in all probability, been operative for a significant fraction of the age of the Galaxy. Presumably, very young stars formed from this gas and having ages less than 1 % of the age of the Galaxy might be expected to retain in their motions the general character of the large-scale expansion of the gas from which they originated.