bluuebunny/crossref_metadata_2025_split huggingface dataset:
Polarization of bursts of solar radio emission at microwave frequencies
Authors: Tanaka H. , Kakinuma T. 
Published: July 2016

The intensity and polarization of solar radio bursts at 9400, 3750, 2000, and 1000 Mc/s have been continuously observed since 1957 July. At 3750 Mc/s, the linearly polarized components were also measured during 4 months from 1957 October till 1958 January [1]. The analysis of observations to 1958 May reveals the following points:1. Many bursts at these frequencies show a difference in the intensity of two circularly polarized components. Frequency distributions of maximum degree of polarization of bursts are shown in Fig. 1, where weak bursts are excluded to reduce errors. At 3750, 2000, and 1000 Mc/s, particularly at 3750 Mc/s, the bursts of small degree of polarization are predominant. Circularly polarized bursts are occasionally observed at 2000 and 1000 Mc/s, but at higher frequencies the degree of polarization is usually less than 50 per cent.2. At 3750 Mc/s, no linearly polarized components could be detected in 117 bursts for a bandwidth of 10 Mc/s. The burst at this frequency is usually composed of a small degree of circularly polarized component and a randomly polarized one.3. Sometimes the sense of polarization varies with frequency. An example is shown in Fig. 2. On this occasion, the degree of polarization is small at 3750 Mc/s and the sense of polarization reverses between 2000 and 3750 Mc/s. Roughly grouped in Table I are 129 bursts simultaneously observed at four frequencies. The reversal of sense was found in 64 per cent of such bursts. Sometimes the sense of polarization varies with time, as may be found in our monthly report. Some of such phenomena may be interpreted by the motion of the source from the preceding part of a bipolar spot group to the following one or vice versa [4].4. In Fig. 3, the bursts associated with flares are classified in three types as regards the sense of polarization, and they are allocated to each of four quadrants on the solar disk according to the position of the flares. At higher frequencies, the sense of polarization seems to correlate with the position of the source as in the case of S component [2, 3]. A precise distribution map at 9400 Mc/s is shown in Fig. 4.
On the polarization of solar radio emission at 1.5-m wavelength
Authors: Alekseev U. J. , Vitkevich V. V. 
Published: July 2016

1. Solar radio emission is usually characterized only by the intensity, i.e. by a single value at a given frequency.In polarization measurements the radio emission is characterized by four values (for example, by the unpolarized-component intensity and three components of the polarization ellipse).Here we see that observations of solar radio emission with a polarimeter give us considerably more extensive information than the usual observations give. It is a very important fact that the polarization of the radio emission is determined by the strength and direction of the magnetic field of emitting regions. Thus, we connect the polarized radio emission with a magnetic field that is noticeably higher than the field in the region which we can study by optical methods.It should also be noticed that one of the most interesting unsolved problems is establishing the nature of the disturbed solar radio emission. It is clear that new information on the polarization of radio emission will contribute to the solution of this problem; but in spite of its importance and urgency, investigations to solve it are being carried on only in a small number of observatories. The observations in Australia and the work in Japan may be mentioned.
Cosmic X-Rays and Interstellar Dust
Authors: Hayakawa Satio 
Published: July 2016

Observational results of cosmic diffuse X-rays are reviewed with particular emphasis on soft X-rays. The intensity distribution of soft X-rays over the celestial sphere indicates that the diffuse component of soft X-rays consists of an extra-galactic and a galactic component. The absorption of the soft X-rays in the interstellar medium results in heating and ionization of interstellar matter. The ionization rate by X-rays is estimated as about 10–16 s–1 per H atom.The scattering of X-rays by interstellar dust grains produces a halo of an X-ray source and smears out the pulsation of X-ray emission. The scattering coefficient and the halo size are given for some typical grain models.The possibility that the dust grains gain relativistic energy is suggested. It is speculated that the relativistic dust grains in metagalactic space may be responsible for cosmic rays of ultrahigh energies and also for the diffuse X-rays by the interactions with cosmic black-body radiation.
Observational Properties of Molecular Outflows
Authors: Padman Rachael , Bence Stephen , Richer John 
Published: July 2016

Molecular outflows are intimately related to the highly collimated Herbig–Haro jets emanating from young stars. In consequence, the usual dynamical timescale significantly underestimates the true age of an outflow. If we correct for this factor, and assume an intrinsic outflow speed similar to that of the underlying jet, we predict that molecular outflows should have an overall extent of several parsecs, in accordance with recent results. It seems likely therefore that outflows are a major source of interstellar turbulence, and have a profound impact on the process of star formation.Whilst interpretation of jet-like outflows is relatively straightforward, the origins of shell-like outflows, such as that from L 1551–IRS5, are less obvious. We discuss the current observational status of both types of flow, and hypothesize an evolutionary connection between them. A large and well-defined outflow sample is urgently required, to permit the establishment of an age-sequence; such a sample would also provide the basis for a proper investigation of outflow energetics and interaction with the ISM.
Numerical Simulations of Optical Knots in YSO Outflows
Authors: Rubini F. , Lorusso S. , Giovanardi C. , Leeuwin F. 
Published: July 2016

The aim of this work is to show that, though 3D effects should be invoked to explain the less regular arc-like regions, the internal knotty emissions may be explained through a roughly axisymmetric pattern of oblique shocks.To this purpose, numerical simulations of non-equilibrium, radiative, hydrodynamical jets in axisymmetric geometry have been performed. After showing that the internal reflecting waves, travelling in the beam of a stellar jet, steepen into oblique shocks, we verify that the optical emission arising from the shocked regions is in good agreement with observations.Since the optical emission strongly depends on the physical and chemical parameters, (namely temperature and electron densities inside the emitting regions), special care is devoted to solving the energy transport equation.
A New Method of Light Curve Analysis: Application to V444 Cygni
Authors: Smith S.A.H. , Theokas A. C. 
Published: July 2016

A new method of light curve analysis is introduced for systems involving an atmospheric eclipse. Occultation or partial eclipses may be treated, with or without the presence of transparency effects. Besides admitting an arbitrary degree of transparency to the eclipsing component, an arbitrary law of limb darkening may also be given the eclipsed star.The method has successfully been applied to the study of narrow band continuum light curves of V444 Cygni obtained by Cherepashchuk and Khaliullin. Primary and secondary minima are examined separately.
The Be Star Φ Persei
Authors: Poeckert R. 
Published: July 2016

He II (λ 4686) emission has been detected in the spectrum of the binary Be star ɸ Persei. The He II emission has velocity variations which are 180° out of phase with the velocity variations of the primary. The primary velocity curve is determined from the broad He I and H lines, and the Fe II emission lines. The amplitude of the primary velocity curve (K1) is 16 ± 2 km s−1. The amplitude of the He II velocity curve is 121 ± 9 km s−1.If one assumes that the He II emission arises from the secondary, minimum masses for the primary and secondary are 29 ± 14 M⊙ and 3.8 ± 1.7 M⊙, respectively. We suggest that the secondary is a hot compact star, either the remaining helium core of a once more massive star, or a neutron star. The primary is too cool, Bl IIIe, to have any appreciable He II emission.
Structure of the Gaseous Disk in RX Cas
Authors: Kříž S. 
Published: July 2016

RX Cas appers to be a long-period Algol-like binary with very fast mass exchange (Struve 1944). In the period 1975-1977, this star was observed photometrically by Arsenijevič, Grygar, Harmanec, Horn, Koubský, Kříž and Pavlovski at Hvar Observatory (Yugoslavia) and by Zverko at Skalnaté Pleso Observatory (Czechoslovakia). The resulting UBV light curves seem to be rather peculiar, for the following reasons:1) Combining our observations with the older ones, we obtain the following formula for the times of minima:
The period increase is surprisingly high.2) The scatter of observed points is considerable (about 0.2 mag.) and cannot be caused by observational errors. It corresponds to short period light variations on the time scale of several days.3) After J.D. 24422660, the brightness of the whole system decreased in all colours. This decrease is about 0.2 mag. in V colour and 0.5 mag. in U colour. Only after J.D. 2442900 the brightness increased again. Such a behaviour confirms the reality of old observations by Gaposchkin (1944) and Martynov (1950) who found a long-term light variation with a period of approximately 500 days.4) The part of the light curve around the phase 0.75 is definitely much lower than the corresponding part around the phase 0.25. This effect is most pronounced in the ultraviolet; the depression around the phase 0.75 is much deeper than the secondary minimum. This behaviour is opposite to the behaviour of dwarf novae. Instead of a bright shoulder connected with a bright spot, we observe some darkening.
Out-of-Eclipse Light Variation of RS CVn Stars
Authors: Catalano S. , Frisina A. , Rodonò M. 
Published: July 2016

The photoelectric observations of the close binary RS CVn carried out at Catania Observatory from 1963 to 1973 are presented. A new period of 9.48 years for the retrograde migration of the wave-like distortion on the light-curve has been determined. The wave amplitude is found to undergo cyclic changes with a period of about 4.74 years.Possible correlation between the wave amplitude and the inclination of the rotational axis and the spectral type of the spotted component for several RS CVn and BY Dra binaries is investigated.
Upper Limits for the Luminosity of a dM Companion in AM Herculis Objects
Authors: Tapia S. , Coyne G. V. 
Published: July 2016

SummaryThe quest for optical identification of X-ray sources has revealed a new class of variables currently formed by AM Her, AN UMa, VV Pup, and the most recent member, 2A 0311-227 (for which a variable star designation will be available soon). These objects show many of the variations common to close binary systems where mass transfer is under way. However, they are distinguished by the high degree (10 to 35 %) of linear and circular polarization observed in the optical and near infrared spectral regions. Apparently the polarization is due to cyclotron emission of electrons located in a region where the magnetic field strength is about 108 gauss.
Method for the Determination of Density and Phase Functions of Interplanetary Dust
Authors: Mujica A. , Lôpez G. , Sánchez F. 
Published: July 2016

SummaryA method of determination of the scattered light intensity, , by a unit-volume of interplanetary space is presented. From ground base Zodiacal Light measurements and the experimental results of Pioneer X the density, ρ(r), and phase, σ(θ), functions are obtained without any previous assumptions about them.
Physical Characteristics of Cometary Dust from Dynamical Studies: A Review
Authors: Sekanina Z. 
Published: July 2016

In this review attention is focused on those areas of the dynamical investigation of cometary dust in which significant progress has been achieved since the previous review papers (Sekanina 1976a, 1977). Much of the progress stems from work based on the model of dust comets formulated by Finson and Probstein (1968a). Their introduction of a new technique for dust-tail studies has made it possible for the first time to gain insight into such properties of cometary dust as the size distribution function of particles shortly after emission from the comet nucleus, the distribution of particle ejection velocities, and the production of dust versus time. Since the Finson-Probstein approach is of a combined dynamical/photometric type, information on particle sizes and masses is provided indirectly, through parametric functions determined from the observed distribution of light intensity in the tail. The basic limitation is that particle radius a cannot be separated from particle density ρ, as their product is related to a directly observed quantity β, the acceleration exerted on the particle by solar radiation pressure. Expressed in units of solar attraction, β for a spherical particle is given by
where c0 = 0.585 × 10−4 g/cm2 and Qpr is the integrated scattering efficiency of the particle for radiation pressure, which varies significantly with a for particles whose dimensions are smaller than the effective wavelength of solar radiation.
Dynamics of Micrometeoroids
Authors: Grün E. , Zook H. A. 
Published: July 2016

Recent observations of zodiacal light have established a reliable and consistent picture of the spatial distribution of interplanetary dust in the ecliptic plane. The spatial density nr varies with heliocentric distance r according to a power law nr ∝ r−ν. From Helios observations an exponent v = 1.3 is derived for the distance interval from 0.08 A.U. to 1 A.U. (Link et al. 1976). Outside the earth's orbit the Pioneer 10 and 11 results suggest a higher exponent v = 1.5 for the distance interval from 1 A.U. to 3.3. A.U. (Hanner et al., 1976). Giese and Grün (1976) showed that the results from zodiacal light observations are compatible with the micrometeoroid fluxes derived from in situ measurements and lunar crater statistics. They found that micrometeoroids in the size range from 10 μm to 100 μm radii (corresponding roughly to 10−8g to 10−5g) contribute most to the zodiacal light brightness.The orbital distribution of large interplanetary particles (10−6 g < m < 10−3g) is known from meteor observations. Sekanina and Southworth (1975) reported average orbital elements of these particles: ā ∼ 1.25 A.U., ē ∼ 0.4 and ī ∼ 20°. Orbital information on micrometeoroids (m < 10−8g) is obtained from in situ detectors on board the Pioneer 8 and 9 and Helios 1 spaceprobes and the HEOS-2 satellite. Characteristics of the different micrometeoroid experiments are given in Table 1. There is almost no time overlap in the data taking intervals of the experiments. Therefore one has to assume that there are no time variations of the meteoroid flux on the time scale of 1 to 10 years if one compares the results from the different experiments. This assumption may be violated for the smallest of the observed particles (m < 10−13g) due to strong electromagnetic interaction of these particles with the interplanetary magnetic field (Morfill and Grün 1979).
A Probable BL Lac Object with Absorption Redshift 1.49
Authors: Hunstead R. W. , Blades J. C. , Murdoch H. S. 
Published: July 2016

The radio source 1309–216 is identified with an 18m stellar object having a steep non-thermal continuum (α = 2.6, fν α ν−α) with no emission features. High resolution spectra obtained with the AAT reveal strong absorption due to the CIV doublet at redshifts 1.361, 1.489 and 1.491. In the strongest absorption system (za = 1.489) the SiIV doublet and possibly SiII are also detected. No information on the optical polarization is available but spectrophotometry at several epochs shows evidence for optical variability and the object is therefore classified tentatively as a BL Lac object.The species found in absorption in 1309–216 are consistent either with ejection from a central source or absorption in the haloes of intervening galaxies. The velocity dispersions and column densities derived for the absorbing regions are comparable to those for gas in the LMC and in the halo of the galaxy.
Ray Trapping in Stellar Envelopes, Pulsational Instabilities and Heating of External Layers
Authors: Souffrin Pierre 
Published: July 2016

The relation between local criteria for hydrodynamic instabilities and stellar stability is reconsidered. This leads to a discussion of the classical problem of stellar pulsation with a special emphasis on the pressure modes of high order spherical harmonics. It is shown that within the frame of the geometrical approximation, acoustic rays exist which are trapped inside any specified slab of a stellar envelope. The pressure modes associated with such rays are conjectured to give rise to small scale instabilities whenever a region exists in an envelope where anylocalcriterium indicates pulsational instability. The model is expected to support and somewhat extend the recent developments concerning the role of pressure non-radial modes on the dynamics of the solar atmosphere and the heating of external layers.Preliminary report available from Observatoire de Nice.
Dynamical Friction Effects on the Motion of Stars in Rotating Spherical Clusters
Authors: Baranov A. S. , Batrakov Yu. V. 
Published: July 2016

Effects of dynamical friction on star orbits in a spherical cluster uniformly rotating with small angular velocity about a fixed axis are considered, deformations of the cluster due to the rotation being neglected. The test star is supposed to move in a noncircular restricted orbit under the influence of both the attraction of the cluster with the smoothed-out distribution of stellar matter and dynamical friction due to random encounters of the test star with other stars of the cluster.The approximate formula for dynamical friction has been deduced, the encounters being supposed to be the binary ones. The differential equations for the osculating elements of the star orbit have been obtained for the two cases of the density distribution - the uniform and the exponential ones. The numerical results demonstrate the complicated character of dynamical friction effects on the evolution of the orbit. The orbit tends to become circular, and its inclination decreases. These effects are proportional to the mass of the test star. This leads to the conclusion that dynamical friction contributes noticeably to the concentration of massive stars near the center of the cluster.
Fe XXIV Emission in Solar Flares Observed with the NRL/ATM XUV Slitless Spectrograph
Authors: Widing Kenneth G. 
Published: July 2016

During the Skylab Mission, the NRL slitless spectrograph photographed a number of flares in the 170–600 Å region with a spatial resolution approaching 2″. At flare maximum the 2s2S1/2— — 2p2P1/2, 3/2transitions of Fe XXIV are present, and show the location of the (approx.) 20 × 106deg plasma with respect to the surface magnetic field and chromospheric (He iiemissions. Three examples are discussed (two only briefly).In the small, intense disk flare of 1973, August 9 the high temperature region appears at the foot of a low altitude arch. The estimated electron density is 5 × 1011cm–3.In the limb flare of 1974, January 15 the hot X-ray emitting component is at a very low altitude compared to the flare loops.In the impulsive double ribbon flare of 1973, June 15 the Fe XXIV emission is centered over the neutral line, forming a bridge-like structure between magnetic regions of opposite polarity. The estimated electron density is 5 × 1010cm–3.The Fe XXIV emission was visible 8 to 10 min as compared with a calculated cooling time by conduction of only 5 min. The lengthened life of the emission may be associated with the observed ‘turbulence’, which inhibits the heat conduction, or alternatively, with a slower energy release prolonged beyond the end of the burst phase.
Rise Time of Hard X-Ray Bursts
Authors: Vorpahl Joan , Takakura Tatsuo 
Published: July 2016

SummaryA study was made of the hard X-ray component in the impulsive phase of solar flares. In 36 randomly chosen events the value for the slope in the differential electron power spectrum E−δ electrons cm−2 s−1 keV−1, was related to the 20–32 keV spike rise time (e-folding) as trise = 0.56 exp (0.88δ) in the thin target model and tfrise = 0.10 exp (0.88δ) in the thick target picture. In the thin target model, the above empirical relation would imply that the acceleration of electrons can be longer when the acceleration rate is smaller. An alternative interpretation would be that an impulsive hard X-ray burst is a superposition of two components emitted from thin and thick targets; when the former predominates, the duration is longer and the photon spectral index is larger, while when the latter predominates, the duration is shorter and the photon spectral index is smaller; 3 ≲δ ≲4 is required (Figure 1). The uncertainty in δ is 0.5 while that in the rise time is 1 s.
Inference of the Hard X-Ray Source Dimensions in the 1972, August 7 White Light Flare
Authors: Rust David M. 
Published: July 2016

SummaryBroadband photographs and spectra of the white light flare of 1972, August 7 have been compared with hard X-ray spectra from the same event. There is a very close temporal correspondence between the hard X-ray and white light emission curves, and these emissions come from layers that are separated by a height of less than 2000 km. The flare shows at least two distinct particle acceleration phases: the first, occurring at a stationary source, gave very bluish continuum emission from 4 bright stationary knots while the X-ray (E > 60 keV) spectrum hardened and reached peak intensity. This phase occurred between 1520 and 1523 UT. In the second phase (1524–1537 UT) the bright knots dissolved and a faint wave moved out from the flare center at 40 km s–1. The spectrum of the wave was nearly flat in the range 4950–5900 Å and analysis of the spectrum indicates that the emission was probably due to heating and ionization by 20–100 keV electrons. The X-ray spectrum, as derived from Interkosmos 7 and ESRO TD-1A satellite data, becomes softer during the wave phase. The close correspondence between the X-ray and continuum emission events shows that, in effect, the hard X-ray source has been resolved. It consists of several changing patches approximately 3″ × 5″ in area, consistent with the upper limit of 1′ from balloon observations (Takakura et al., 1971).