bluuebunny/crossref_metadata_2025_split huggingface dataset:
VW Hydri, a U Geminorum-Type Star with Periodic Variations During Outbursts
Authors: Vogt N. 
Published: July 2016

Extensive photoelectric observations of VW Hyi have been carried out during minimum light and eruptions. In the minimum stage VW Hyi shows a periodically repeating hump (similar to that of U Gem) from which an orbital period of has been derived. No eclipses are present. The two types of eruptions known previously for VW Hyi correspond to different physical processes: the short eruptions (lasting ∼4d) resemble again those of U Gem; the minimum hump disappears during bright phases. During the long eruptions (lasting ∼ 17d) a light curve with pronounced peaks has been observed with periodicities of . Significant colour variations with this period are also present. During one long maximum, the repeating feature separated into two peaks. A first attempt has been made to interpret qualitatively the observed facts by an interaction between gas streams from the inner Lagrangian point and ejected matter from the white dwarf component.The detailed results were published in Astronomy and Astrophysics36 (1974), 369.
A Search for Super-Rapid Variability of X-Ray Sources and Other Peculiar Objects
Authors: Evseyev O. A. , Mansurov V. N. , Pavlova V. S. , Pustil'Nik L. A. , Shvartsman V. F. , Tsarevsky G. S. , Yakushev A. K. 
Published: July 2016

At the Special Astrophysical Observatory of the U.S.S.R., an experiment to detect super-rapid variability of brightness and polarization in a number of peculiar objects is being carried out. This includes the optical stars identified with X-ray sources, specifically Cyg X-1, Her X-1 and Sco X-1, as well as the so-called DC-dwarfs and some BL Lac-type objects (that is optical objects possessing a continuous spectrum). The time range of measurements varies for different objects; however as a rule, it lies within 10−5 to 10 s.At the time of our observations no rapid and super-rapid fluctuations of radiation exceeding in amplitude 10% have been detected.
RR Lyrae- and W Virginis-Type Stars
Authors: Kukarkin B. V. 
Published: July 2016

RR Lyrae stars: Normalized period-frequency diagrams are discussed, see Table I and Figure 1. Two ‘standard’ period-frequency relations were derived: one for − 1.17 and the other for − 1.72. The peculiarity of the diagrams for some clusters is pointed out. Various metallicity criteria are discussed together with other features of globular clusters. Some unexplained anomalies are found.W Virginis stars: Properties of these stars are discussed. They too seem not to form a homogeneous group. The lack of accurate observations is stressed.
Stellar Photometric Observations at Hα Through a Narrow-Band Interference Filter
Authors: Butler Hugh E. 
Published: July 2016

The paper describes the results of stellar photoelectric observations made with a small telescope and a 3 1/2 Å wide filter centred at Hα.The method proved to be a sensitive one for detecting change in the spectrum but did not allow differentiation between changes in the Hα profile and wavelength changes due only to the Doppler effect. It was possible, however, to recognise and qualitatively to eliminate the Doppler changes due to the Earth's Annual Motion.Of ten Be stars examined three, although in strong emission, showed little change over the periods of observation, the longest of which was 9 months. The other seven showed large and random changes.Warnings are given about the difficulty of tuning such a filter exactly to Hα and the need to monitor accurately the filter for long term changes in passband and throughput.
Tidal Interactions in Compact Binary Systems
Authors: Wheeler J. C. , Lecar M. 
Published: July 2016

An analytic model has been constructed for the change of orbital elements because of tidal drag in a binary system where one of the components is compact (Lecar et al., 1976). The basic assumptions are (i) tides on the compact object are neglected (ii) only P2 deformations of the non-compact star are considered (iii) the lag angle is linearly proportional to the difference between the instantaneous orbital angular velocity and the spin angular velocity of the non-compact star (iv) the semi major axis a and eccentricity e do not change significantly in a single orbit. The results are exact solutions for a and ė as a function of e and the ratio of primary star to orbital angular velocity, Ω/ω.Tidal instability in this model is manifest by the dynamical inability to attain or sustain synchronism. An analysis to second order in e and first order in (Ω/ω−1) shows that the criterion for instability is the same as in the work of Counselman (1973), namely ma2 > I where m is the reduced mass and I the moment of inertia of the primary star. This criterion is shown to apply to eccentric orbits and is thus more general than the criterion derived from the energetics of circular orbits. Stable systems may overshoot the condition of synchronism before settling into the final circular synchronous orbit.
The effective temperatures of the O stars
Authors: Pottasch S. R. , Wesselius P. R. , van Duinen R. J. 
Published: July 2016

Far ultraviolet photometric observations (in 5 bands between λ = 1550 Å and 3300 Å) are presented for ten O stars which are also the exciting stars of diffuse nebulae. Since the number of photons shortwards of the Lyman limit is known for these stars, sufficient information on the total flux is available to determine the effective temperature without making any assumptions concerning a model atmosphere. Conversely, the distribution of flux with wavelength can be used to determine the applicability of a given model. A detailed discussion of this is presented.A comparison of these ‘normal’ O stars and stars with O type spectra which excite planetary nebulae is given. It is concluded that the atmospheres of these two types of O stars are very similar; probably they have the same effective gravity. Further, a discussion of the Zanstra He II temperature is presented.
Theoretical considerations of the warp and thickening
Authors: Saar E. 
Published: July 2016

As a theoretical subject, the study of the bending of the gaseous planes of galaxies has not been extremely popular. It seems that this is due to an excellent and thorough paper on the subject, published by Hunter and Toomre in 1969. At that time there existed three (or four) rival theoretical mechanisms:(1)vertical oscillations of the galactic disk, considered first by Lynden-Bell (1965);(2)asymmetrical pressure on the disk due to intergalactic wind (Kahn and Woltjer 1959);(3)tidal influence of the Magellanic Clouds, from(a)the case of Stationary Clouds, and(b)the case of Clouds orbiting around the Galaxy (Elwert and Hablick 1965, Avner and King 1967).
Vibrations of Non-Uniform Spherical Systems
Authors: Severne G. , Kuszell A. 
Published: July 2016

Dispersion relations have been obtained and analyzed for a non-uniform, non-rotating spherical gravitational system. A restriction to short wavelengths makes it possible to consider a linearized form of the collisionless Boltzmann equation, differing from that for homogeneous systems by the appearance of a term expressing the effect of the mean self-gravitational field upon the motion. The mean field affects the radially directed wave perturbations, with a breaking of symmetry.Inwardly and outwardly directed modes have quite different propagation characteristics, inward modes being preferentially propagated. Locally, the stability of the system is enhanced due to the effect of the mean field.
The Angular Diameter-Redshift Relation for Scintillating Radio Sources
Authors: Hewish A. , Readhead A. C. S. , Duffett-Smith P. J. 
Published: July 2016

Observational evidence on the angular diameter-redshift relation using radio sources has, until recently, been confined to studies of the overall angular size. In this paper a different approach is described in which the very compact hot spots in radio sources are used as standard measuring rods. Such hot spots appear to be especially suitable for cosmological studies for the following reasons.
(a)Hot spots which contain one half or more of the total flux density are generally found only in the most powerful sources (P178 ≳ 1027 W Hz−1 sr−1).(b)Hot spots appear to show a smaller dispersion in physical size than the overall source dimensions.
Presupernovae
Authors: Imshennik V. S. , Nadyozhin D. K. 
Published: July 2016

A survey is given of the present state of theories concerned with the mechanism of supernova outbursts. Special attention is paid to the state of the star immediately before the supernova explosion (presupernova).The following topics are discussed.(1) The thermonuclear model of supernova explosions.(2) The gravitational collapse model of supernova explosions.(3) The characteristics of presupernova models resulting from the comparison of theoretical light curves with observational ones.
On RW Aurigae Type Stars and Related Types
Authors: Hoffmeister C. 
Published: July 2016

First of all it will be necessary to say a few words on terminology. Different names are now in use either for the same group of variables or for different variants of a rather heterogeneous class. Let me list the following:
RW Aurigae stars,RR Tauri stars,T Tauri stars,Nebular type variables,Orion type variables,Nova-like variables,Main sequence variables.
11. Some unusual spectra of meteors from the Palomar 18-inch Schmidt file
Authors: Barbon R. , Russell J. A. 
Published: July 2016

Five meteoric spectra have been studied that were obtained during the period mid-June to mid-December, 1966. They include spectra of a Perseid, a Geminid, and three sporadic meteors. Four were photographed on Royal Pan emulsion without a filter; the Geminid on Tri X Aerecon with a GG11 filter.Lines in the spectrum of one of the sporadic meteors indicate that two meteoroidal fragments were involved which diverged with increasing atmospheric penetration and which flared at different altitudes, indicating that the flares were not the result of atmospheric stratification.The second sporadic and the Perseid were photographed about 2½ hours apart. The sodium D line is strong in the Perseid but does not appear in the sporadic spectrum. If present, it is blended with the diagonal sequence Δv = + 4 of the first positive group of the neutral nitrogen molecule, which appears in both spectra. A line questionably identified as the forbidden line of oxygen at 5577 Å appears faintly in the sporadic. The strength of the N2 sequence in these two spectra, and the absence of the D line in the sporadic, are very unusual. The proximity in time of appearance of these two spectra, and the absence of the N2 bands from the other two sporadic spectra, suggest that a temporary atmospheric condition may be responsible for the strength of the nitrogen radiation.The Geminid has as its principal feature the Δv = + 3 sequence of the first positive group of N2. We have not previously observed this band in meteors as low in velocity as the Geminids.
25. Orbits of photographic meteors
Authors: McCrosky R. E. 
Published: July 2016

New photographic observations of meteors in the brightness range −5 > Mp > −18 (?) and with a median value of M = −8·5 have yielded orbits with a precision of better than 1° in the angular elements and of about 0·05 in e and 1/a. A comparison of 100 of these fireball orbits with Super-Schmidt orbits shows:
(1)A class of orbits, comprising about 25% of the faint meteors, of long period, is almost completely absent among the fireballs.(2)Small perihelion distances (q < 0·2 AU) are not found. A maximum at q ~ 0·7 AU, which also appears in the Super-Schmidt orbits of short period, corresponds to the perihelion distances of all but two of the Apollo objects.(3)The distribution of aphelia shows a marked decrease at Jupiter when compared to a similar distribution of small, faint meteor orbits. With the existing material, we cannot determine whether this represents an important evolutionary distinction between meteoroids of different mass or is simply the result of an inappropriate choice of the division between ‘large’ and ‘small’ orbits in the faint meteor data.Provisional values of the bulk density of 28 of the fireballs as determined from the photometric mass and the observed mass-area ratio indicate that these meteoroids do not differ significantly from those observed with the Super-Schmidt cameras. Evidence of gross fragmentation of these large objects at high elevation and evidence of small or negligible terminal masses suggest that the material is friable. There is no certain evidence that any appreciable fraction of fireballs is produced by high-density, cohesive material.If the above analysis is correct, we should expect an occasional (1 year−1 106 km−2?) meteorite fall of discoverable size originating from a low-density meteoroid.
37. Structure and evolution of meteor streams
Authors: Kresák Ľ. 
Published: July 2016

Our present knowledge of meteor streams is based on three types of meteor showers:
(1)About one or two dozen major showers that recur annually in optical and radar records of meteor activity.(2)An indefinite number of minor showers, hardly distinguishable from the sporadic background, which can be traced only by comparing individual meteor orbits.(3)Rare appearances of temporary showers, sometimes producing extraordinary meteor displays. These include prominent concentrations of meteors within some of the annual streams, meeting the Earth under specific conditions.
Magnetic classification of active regions
Authors: Smith Sara F. , Howard Robert 
Published: July 2016

All the active regions observed on the Sun with the Mount-Wilson magnetograph between August 1959 and December 1962 have been given magnetic classifications in a system similar to the Mount-Wilson sunspot-classification scheme. The flare productivity of regions classified as unipolar, bipolar, and complex bipolar, as well as regions composed of multiple bipolar components has been studied. It has not been necessary to provide a classification corresponding to the γ class of sunspots. Although the relatively poor angular resolution employed in the magnetograms limits somewhat the accuracy of the data, it is clear that both complex bipolar regions and regions with multiple bipolar components produce more than three times the number of flares than the simple bipolar regions produce. The most flare-productive class of regions is the reversed polarity complex classification.The statistical relation of the spot magnetic-field classification to the classification of the corresponding plage fields has been studied and found to be poor for these data.The distribution of the magnetic regions in latitude shows that many of the regions with polarities reversed from the usual orientation are confined to the equatorial zone.
Some patterns in the development of centers of solar activity, 1962–66
Authors: Dodson Helen W. , Hedeman E. Ruth 
Published: July 2016

A graphical representation of the 66 solar rotations (Carrington) between January 1, 1962 and December 31, 1966 has been prepared. It includes all centers of activity for which the calcium plage attained an area of at least 1000 millionths of the solar hemisphere and/or intensity 3 (McMath scale). In this study the antecedents, descendents, and neighbors of each region can easily be discerned. The work shows clearly that zones of activity, apparently closely related and much larger than single plages existed for long intervals of time. For example, the significant increases in solar activity in February, May, and October of 1965 occurred in a ‘family’ of calcium plages apparently related through similarities of position and strong radio emission.The members of ‘families’ of centers of activity are found at systematically changing longitudes. For some ‘families’ the change of longitude appears to be primarily a consequence of differential rotation; for others, the pattern of formation of active centers dominates.According to the data for 1962–66 a meaningful study of the development of a center of activity may require consideration not only of the past history of the zone of the Sun in which it occurs but also of the zone approximately 180° away on the opposite hemisphere.
Oscillatory convection in strong magnetic fields and origin of active regions
Authors: Syrovatsky S. I. , Zhugzhda Y. D. 
Published: July 2016

The convection in a compressible inhomogeneous conducting fluid in the presence of a vertical uniform magnetic field has been studied. It is shown that a new mode of oscillatory convection occurs, which exists in arbitrarily strong magnetic fields. The convective cells are stretched along the magnetic field, their horizontal dimensions are determined by radiative cooling. Criteria for convective instability in a polytropic atmosphere are obtained for various boundary conditions in the case when the Alfvén velocity is higher compared with the velocity of sound.The role of oscillatory convection in the origin of sunspots and active regions is discussed.
Fluctuations of the magnetic-field strength of sunspots within one day
Authors: Künzel H. 
Published: July 2016

In the period of May-June 1965, the magnetic-field strengths of twenty sunspots were measured in order to investigate fluctuations within one day. The results of spectrograms, which were taken in the interval of one hour, are given in graphs. The mean error of one value has the size of ± 169 gauss. The graphs show the general tendency in the behaviour of field strength. Fluctuations of magnetic-field strength up to 800 gauss within a few hours were found. The short-time fluctuations shown in the graphs are mostly smaller than the mean error and therefore probably not real.For more details see Astron. Nachr., 289 (1967), 233.
Correlation between Ca plages and longitudinal magnetic fields of the CSSAR active regions
Authors: Bumba V. , Godoli G. 
Published: July 2016

The shapes of K2,3,2 Ca plages and longitudinal magnetic fields are compared for CSSAR active regions during their first transit on the solar disk.The bipolar magnetic regions follow the Hale polarity law.Often the region of inversion of the magnetic field corresponds to a gap in the Ca plage structure.Bright patches of plages may coincide with magnetic inclusions, magnetic hills, and occasionally also with regions of inversion of the magnetic field. The outline of Ca plages follow well the isogauss of 20–40 oersted.Histograms of the distances of individual magnetic field intensity peaks do not only correspond to the geometry of the supergranular network but also seem to indicate a difference in the organization of these peaks between the leading and following polarities.
X-radiation studies of the corona
Authors: Pounds K. A. , Evans K. , Russell P. C. 
Published: July 2016

The coronal X-ray emission has been studied in a series of sunpointed Skylark-rocket flights over the period August 1964 to August 1967. Two types of instrument have been used, namely, an array of pinhole cameras, to study the distribution of X-ray sources across the solar disk, and a set of Bragg crystal spectrometers, to examine the detailed spectrum of the emission.Six rocket flights in all (Skylarks 301, 302, 303, 306, 307, and 406) have provided solar X-ray photographs, covering the wave-band 12–60 Å. The main conclusions of this work may be summarised as follows:
(1)Of over twenty separate calcium-plages areas, all those having an area-intensity product greater than 300 were associated with enhanced coronal X-radiation, this ‘threshold’ being merely a function of X-ray camera sensitivity.(2)The plages studied were of from 1st to 4th rotation, indicating the enduring nature of the local coronal X-ray enhancement.(3)Crude spectral analysis, derived from different filters used in a given camera array, showed an increasing contrast between the active region and disk emissions below 25 Å, indicating the probability of the active region coronal material being rather hotter.(4)Photographs of regions on the disk and on the limb showed a typical coronal active region to produce more than 50% of its total X-ray flux from a region within 1 arc minute cube. Electron densities up to 10 times the normal coronal values are required by the measured X-ray brightness of the larger regions.(5)The major part of the emission above 20 Å arises from the (cooler) background corona. Examination of this coronal disk emission revealed strong limb brightening, polar darkening (particularly in the 1964–65 photographs) and a band of slightly enhanced X-radiation near latitude 35 °N. The latter observation was noted on successive flights, in October 1965 and February 1966, and clearly followed the tilt in aspect angle of the solar disk.Skylarks 304 and 305 were equipped with uncollimated Bragg crystal spectrometers. The former payload, flown in May 1966, revealed strong line emission down to the scan limit at 11 Å. Emission lines of O VII and VIII, Ne IX and X, Fe XVII and XVIII and NI XIX have been identified. All but the O VII series were found to have dominant components arising from a large active region on the solar disk, and an analysis has shown that the complete active-region spectrum is consistent with an electron temperature of 3 million degrees. Intercomparison of the different emission lines indicated coronal abundances of iron, nickel and neon comparable to those derived earlier by Pottasch from an analysis of the solar UV spectrum.Provisional analysis of the latest flight (Skylark 305 in August 1967), employing crystals of beryl and EDDT in addition to the KAP flown on Skylark 304, has shown strong emission lines of the helium-like ions Mg XI and Si XIII, with weaker but significant intensity in Lyman-α of Mg XII (8·4 Å) and Si XIV (6·2 Å), the latter emission requiring the presence of active region material at a temperature of near 107°K.
The observation of 10–50 KeV solar flare X-rays by the OGO satellites and their correlation with solar radio and energetic particle emission
Authors: Arnoldy R. L. , Kane S. R. , Winckler J. R. 
Published: July 2016

More than 70 cases have been observed of energetic solar flare X-ray bursts by large ionization chambers on the OGO satellites in space. The ionization chambers have an energy range between 10 and 50 KeV for X-rays and are also sensitive to solar protons and electrons. A study has been made of the X-ray microwave relationship, and it is found that the total energy released in the form of X-rays between 10 and 50 KeV is approximately proportional to the peak or total energy simultaneously released in the form of microwave emission. For a given burst the rise time, decay time and total duration are similar for the 10–50 KeV X-rays and the 3 to 10 cm radio emission. Roughly exponential decay phases are observed for both emissions with time constants between 1 and 10 min. All 3 or 10 cm radio bursts with peak intensity greater than 80 solar flux units are accompanied by an X-ray burst greater than 3 × 10−7 ergs cm−2 sec−1 peak intensity. The probability of detecting such X-ray events is low unless the radio spectrum extends into the centimetric range of wavelengths. The best correlation between cm-λ and energetic X-rays is observed for the first event in a flare. Subsequent structure and second bursts may not correspond even when the radio emission is rich in the microwave component. The mechanism for the energetic X-rays is shown to be bremsstrahlung probably of fast electrons on a cooler plasma. If the radio emission is assumed to be synchrotron radiation then a relationship is developed between density and magnetic field which meets the observed quantitative results. One finds, on the average, that 5 × 10−54 joules m−2 (CPS)−1 of microwave energy at the Earth are required per electron at the Sun to provide the radio emission for the various events.A strong correlation between interplanetary solar flare electrons observed by satellite and X-ray bursts is shown to exist. This correlation is weak for solar proton events. One may infer a strong propagation asymmetry for solar flare electrons along the spiral interplanetary magnetic field.