bluuebunny/crossref_metadata_2025 huggingface dataset:
A review of space helioseismology
Authors: Toutain T.
Published: July 2016

The helioseismology started in 1960 with the discovery of oscillations of the velocity field on the solar surface by Leighton, 1960. The mechanism producing these oscillations remained unexplained for the next ten years until Ulrich, 1970, and independently Leibacher and Stein, 1971, demonstrated that acoustic waves trapped beneath the solar surface could generate such oscillations. According to that theory the Sun should oscillate globally and not only locally as seen in the pionnering observations. First Deubner, 1975, and then Claverie et al., 1979, and Grec et al., 1980, demonstrated the existence of global oscillations of intermediate and low degrees. These observations analysed in terms of k-ω diagram and power spectrum led to the famous p-modes ridges and spectrum lines which are at the base of any inference of the solar structure. All these observations where carried out from the ground. Nevertheless ground-based observations at that time (early eighties) were suffering some limitations which could be over taken from space. This is the reason why the eighties saw the intensive development both of ground-based networks and space missions for helioseismology resulting in 1995 in the existence of four networks: BISON, IRIS, GONG and TON (see Pallé, 1996) and the launch of the SOHO satellite (Domingo et al., 1995). In the next section I review the limitations of ground-based observations and those of space missions. In section 3, I describe in a chronological order the past space helioseismology missions (from 1980 to 1994). Furthermore I discuss, in section 4, the present status of space helioseismology with SOHO and finally in section 5 the co-ordination of space missions and ground-based solar observations. In the last section the future and the prospects of space helioseismology are reviewed.
Theoretical solar models
Authors: Provost J.
Published: July 2016

In the last two decades the large amount of accurate helioseismic data has open a new possibility to sound the stellar interiors and to test the stellar evolution theory. This has particularly impulsed a critical reexamination of the basic assumptions and physical inputs in solar modelling. The present status of theoretical solar models is presented and discussed in relation with the observational constraints: helioseismology, lithium depletion and measured neutrino fluxes.
Stellar rotation and mixing
Authors: Zahn Jean-Paul
Published: July 2016

Many observations indicate that some mixing occurs in stellar radiation zones: in massive stars, chemical elements resulting from nuclear burning in the core are detected at the surface, and in solar-type stars lithium is depleted with age. Since all mixing processes transport also momentum, the depletion of lithium should be linked with the loss of angular momentum through the stellar wind, and there are indeed signs of such a correlation in the behavior of tidally-locked binaries. Moreover, any transport process leaves its signature in the internal rotation profile, and this can help greatly in its identification. After reviewing the main transport mechanisms which have been considered so far, our present conclusion is that the uniform rotation observed in the radiative interior of the Sun is probably achieved by the action of internal waves emitted at the base of the convective envelope. It remains to be verified whether these waves contribute directly to the mixing, or whether they act only through the shaping of the rotation profile, which in turn determines the mixing through meridian circulation and turbulent diffusivity.
Excitation of solar acoustic oscillations
Authors: Kumar Pawan
Published: July 2016

The stochastic excitation of solar oscillations due to turbulent convection is reviewed. A number of different observational results that provide test for solar p-mode excitation theories are described. I discuss how well the stochastic excitation theory does in explaining these observations. The location and properties of sources that excite solar p-modes are also described. Finally, I discuss why solar g-modes should be linearly stable, and estimate the surface velocity amplitudes of low degree g-modes assuming that they are stochastically excited by the turbulent convection in the sun.
Asteroseismology of white dwarf stars
Authors: Vauclair G.
Published: July 2016

The theoretical potential of white dwarf asteroseismology is summarized. It is shown how one can derive fundamental parameters on the internal structure and evolution of these stars. The analysis of the non-radial g-modes permits in principle to determine the total mass, the rotation rate, the magnetic field strength. The mass of the outer layers, left on top of the carbon/oxygen core, can be determined as well as the structure of the transition zone between the core and the outer layers, giving an “a posteriori” unique information on the efficiency of the previous mass loss episodes. When measurable, the rate of change of the pulsation periods gives direct access to the evolutionary time scale and to the chemical composition of the core. These theoretical expectations are compared with the observations of variable white dwarfs in the three known instability strips for the planetary nebulae nuclei and PG1159 stars, for the DB and DA white dwarfs. Emphasis is put on results obtained from multi-sites photometric campaigns. Prospects on both theoretical developments and observations conclude the review.
Giant Herbig-Haro Flows
Authors: Bally John , Devine David
Published: July 2016

Recent observations with wide field-of-view CCDs have shown that over 20 Herbig-Haro flows extend for more than one parsec from their driving sources. We review the observed properties of these giant HH flows and discuss the physical consequences for star formation, and for the physics and chemistry of the surrounding interstellar medium.
Spectroscopic Signatures of Microjets
Authors: Solf J.
Published: July 2016

High-resolution long-slit spectroscopy of forbidden emission lines is used to investigate on a sub-arcsecond scale the spatial and kinematic properties and the physical conditions of the mass outflows from T Tauri stars in the immediate vicinity of the outflow source (microjets). Special attention is given to the case of DG Tau. The data permit us to distinguish physically different outflow components: (1) a high-velocity component (HVC) attributed to a fast jet, (2) a low-velocity component (LVC) attributed to gas entrained by the jet, and (3) a near-rest-velocity component (NRVC) attributed to a slow disk wind and/or disk corona.
The Ionization State along the Beam of Herbig-Haro Jets
Authors: Bacciotti Francesca
Published: July 2016

An original spectroscopic diagnostic technique has been recently developed that allows to estimate in a model-independent way the ionization fraction xe and the average excitation temperature in the beam of Herbig-Haro jets (Bacciotti, Chiuderi and Oliva 1995). The procedure is based on the fact that in the low excitation conditions present in this region the ionization state of oxygen and nitrogen can be assumed to be regulated by charge exchange with atomic hydrogen. The application of this technique to long-slit spectra of several well-known stellar jets indicates that the hydrogen ionization fraction xe starts from 0.2-0.4 at the beginning of the flow and gently decreases along the whole jet or along sections of it as a result of time-dependent recombination. The average temperature stays almost constant, ranging from 4500 to 7000 K. The momentum transfer rates evaluated with the derived total number densities (nH ∼ 103–104 cm–3) give support to the picture in which the jet is responsible for the acceleration of a surrounding molecular outflow.
Far-IR Spectrophotometry of HH Flows with the ISO Long-Wavelength Spectrometer
Authors: Liseau R. , Giannini T. , Nisini B. , Saraceno P. , Spinoglio L. , Larsson B. , Lorenzetti D. , Tommasi E.
Published: July 2016

Full Iso-Lws spectral scans between about 45 to 190 μm of 17 individual HH objects in 7 star forming regions have revealed essentially only [O I] 63 μm line emission, implying that the Fircooling of these objects is totally dominated by this line alone. In this case, J-shock models can be used to determine the mass loss rates of the HH exciting sources. These mass loss rates are in reasonably good agreement with those estimated for the accompanying CO flows, providing first observational evidence that HH and molecular flows are driven by the same agent. The Lmech – Lbol relation, based on our results with the Lws, implies that young stellar objects of lower mass are loosing mass at relatively higher rates than their more massive counterparts.
The Physical and Chemical Effects of C-Shocks in Molecular Outflows
Authors: Des Forêts G. Pineau , Flower D.R. , Chièze J.-P.
Published: July 2016

The bow shocks which are observed in jets associated with low-mass star formation probably have C-shock characteristics over at least part of their extent. We show that ion-neutral streaming in C-type shocks can give rise to the release of significant amounts of silicon from the refractory cores of dust grains and hence to the formation of SiO in the gas phase. The computed profiles of SiO emission lines are found to be qualitatively similar to those observed in molecular outflow regions such as L1448. The question of the validity of the stationary-state assumption, adopted in all previous studies of C-shocks in the interstellar medium, is addressed. Time-dependent calculations of the evolution of a C-type shock propagating in low-density gas suggests that steady state is unlikely to be attained under the dynamical conditions in outflows.
Protostellar X-Rays, Jets, and Bipolar Outflows
Authors: Shu Frank H. , Shang Hsien
Published: July 2016

We review the theory of x-winds in young stellar objects (YSOs). In particular, we consider how a model where the central star does not corotate with the inner edge of the accretion disk may help to explain the enhanced emission of X-rays from embedded protostars. We argue, however, that the departure from corotation is not large, so a mathematical formulation that treats the long-term average state as steady and axisymmetric represents a useful approximation. Magnetocentrifugally driven x-winds of this description collimate into jets, and their interactions with the surrounding molecular cloud cores of YSOs yield bipolar molecular outflows.
Numerical Simulations of Jets from Accretion Disks
Authors: Pudritz Ralph E. , Ouyed Rachid
Published: July 2016

Hydromagnetic disk winds have great potential as a general theory for the production and collimation of astrophysical jets in both protostellar and black hole environments. We first review the analytic stationary theory of these outflows as well as recent numerical simulations of MHD disk winds. We then focus on simulations that we have done on winds from magnetized disks using the ZEUS 2-D code of Stone and Norman. We treat the Keplerian disk as a fixed platform throughout the simulations. We show that both stationary and episodic, jet-like outflows are driven from disks depending upon their magnetic structure and mass loss rates.
NMA Imaging of Envelopes and Disks around Low Mass Protostars and T Tauri Stars
Authors: Kitamura Yoshimi , Saito Masao , Kawabe Ryohei , Sunada Kazuyoshi
Published: July 2016

We are intensively studying low mass star formation with the radio telescopes at Nobeyama in Japan. Using both the Nobeyama 45 m dish equipped with a 2 × 2 array receiver and the Nobeyama Millimeter Array (NMA), we can cover a very wide spatial range from overall molecular clouds down to compact protoplanetary disks. With the 45 m dish we are investigating hierarchical structures of molecular clouds including star-forming cores. With NMA we are imaging disklike structures (i.e., envelopes, accretion disks, and protoplanetary disks) around protostars and T Tauri stars. Recently, we have completed our survey for dense disklike envelopes around eleven Class 0 & I protostars by NMA. In this paper, we will present our recent results of the disklike envelopes in addition to the previous NMA results of the disks around three T Tauri stars. On the basis of the data, we will discuss the evolution of the disklike structures (dense envelopes → tenuous ones → dispersing ones → accretion disks → protoplanetary ones), and propose a new scenario for the formation of low mass stars.
The Observational Evidence for Accretion
Authors: Hartmann Lee
Published: July 2016

Outflows from low-mass young stellar objects are thought to draw upon the energy released by accretion onto T Tauri stars. I briefly summarize the evidence for this accretion and outline present estimates of mass accretion rates. Young stars show a very large range of accretion rates, and this has important implications for both mass ejection and for the structure of stellar magnetospheres which may truncate T Tauri disks.
Circumstellar Molecular Envelopes
Authors: Fuller G. A. , Ladd E. F.
Published: July 2016

The results of C17O and C18O observations of low luminosity young stars are discussed and the derived properties of the circumstellar molecular envelopes described. Much of the circumstellar material is quiescent and cold. The youngest sources have envelopes which contain up to ∼ 0.3 M⊙ of material within 3000–4000 AU of the central star. From a survey of sources in Taurus, both the timescale and mechanism of clearing of the circumstellar region are investigated. Neither the observed outflows nor standard infall models alone are capable of clearing the circumstellar regions quickly enough. Maps of the circumstellar material around two very young sources suggest that the stars form from flattened configurations of material.
Water Masers toward Low-Luminosity Young Stellar Objects
Authors: Claussen Mark J , Marvel Kevin B. , Wootten H. Alwyn , Wilking Bruce A.
Published: July 2016

A review of the importance of water maser observations toward young stellar objects (YSOs) is presented. Also, we present recent, differing types of observations of water masers near YSOs. Single antenna observations, taken regularly, characterize the variability of the masers and allow estimates of time and spatial scales. High resolution (∼ 1 mas) multi-epoch observations allow proper motions to be studied. Detailed analysis of such proper motions will allow the placement of the masers in the circumstellar (a disk) or near-stellar environment at the base of the outflow. Radio interferometric techniques are the best method of making estimates of the kinematics of the gas in these regions.
Introductory Address
Authors: Plavec Mirek J.
Published: July 2016

Four years ago, in 1975, we met in Cambridge, England for our first IAU Symposium devoted entirely to binary stars. Most of the talks given there were theoretical, and at the end some of us felt that it would be appropriate to organize yet another Symposium soon, this time oriented more towards observations and their immediate interpretation. This is why we have come together here in Toronto. Four years is not a long interval of time, and few disciplines of astronomy repeat their Symposia on such a short time scale. While the need for another Symposium was clear to the binary stars investigators, it is not so obvious to other colleagues. We must therefore be very grateful to the Executive Committee of the International Astronomical Union for their great understanding of our needs. This understanding went far beyond approving and sponsoring this meeting: We have received a substantial financial assistance, which all went to the support of the travel expenses of some of the participants. Many more travel grants were possible thanks to a most generous support by the University of Toronto. I would like to thank both institutions.
The Formation of Close Binaries
Authors: Lucy L. B.
Published: July 2016

Although the formation of close binaries has been the subject of numerous investigations in the last 100 years (for a recent review, see Tassoul 1978), we cannot yet claim decisive observational support for any theory, a state of affairs probably reflecting insufficient development of the various theories, rather than a failure to propose the correct mechanism(s). If this is indeed so, we can look forward to significant progress soon, since numerical techniques now allow us - albeit crudely - to follow through to completion binary formation by the two most likely mechanisms, fission and fragmentation. (Herein a binary will be described as having formed by fission if it results from the bifurcation of a rotating protostar as it contracts quasi-statically towards the main sequence and by fragmentation if it results from a rotating protostar's break up into two or more components during, or immediately following, a phase of dynamical collapse).
Binarity as a Factor in Stellar Radio Emission
Authors: Gibson D. M.
Published: July 2016

A simple examination of Table I which lists the 26 positively detected “active” radio stars reveals that 21 are interacting binaries. Thus, on face value, membership in a close binary system would appear to be an important factor in producing conditions which favor stellar radio emission. However, this conclusion ignores the considerable biases which have characterized most of the surveys (c.f., references in Wendker 1978) made to date wherein selection criteria such as binarity itself, evidence for mass exchange, strong magnetic fields, optical activity, and similarity to previously detected systems have been cited. In very few cases (c.f., Gibson 1977) have complete samples (i.e., a uniform survey of all stars in a particular class to a given luminosity limit) been observed. Therefore, it is difficult to examine the role of binarity in stellar radio emission and draw conclusions which have statistical support. However, the body of radio star data does include observations of about 700 objects and thoughtful analyses of a carefully selected subset should reveal trends which, if they do not lead to firm conclusions, should at least point out the direction for future study.
Observations of Spectroscopic Binaries with a Solid-State Detector
Authors: Fekel Francis , Lacy Claud H. , Tomkin J.
Published: July 2016

The recent installation of a solid-state 1024-element silicon photodiode array detector (Reticon) at the coude focus of the 2.7 m McDonald Observatory reflector has greatly extended its limits of observation for binary and multiple systems which have weak and/or broad-lined components. This detector can produce extremely high signal-to-noise ratio observations and has high quantum efficiency over the wavelength region 3000-11000Å. The observational programs of three users of this device are described below.
Evolution of Early-Type Contact Binaries
Authors: Sugimoto Daiichiro , Miyaji Shigeki
Published: July 2016

SV Centauri is an early-type contact binary for which detailed physical data have been obtained from observations (Wilson and Starr 1976). The orbital period is p = 1.659 days and the separation is a = 16.1 R⊙. The radii of component Stars A and B are, respectively, R = 7.2 and 6.9 R⊙ so that they are in overcontact. The masses and the luminosities are M = 11.1 and 9.3 M⊙, and L = 2830 and 10900 L⊙ for Stars A and B, respectively. The more massive Star A is called the primary star but its luminosity is fainter than Star B. This implies that it is in the phase of rapid mass transfer and mass is outflowing from Star A. Indeed one of the most interesting and important points of this system is that the rate of period change is measured to be dP/dt = −9.4 × 10−8 (Irwin and Landolt 1972) which corresponds to the mass transfer rate of dMA/dt = −4 × 10−4 M⊙ yr−1.
What Do We Know About Algol?
Authors: Söderhjelm S.
Published: July 2016

A comprehensive analysis of previously published observations of Algol has been submitted to Astronomy&Astrophysics under the title “Geometry and Dynamics of the Algol System”. The main results can be summarized as follows:

The masses of the three components are mA = 3.6±0.1, mB=0.79±0.01, mC=1.6±0.1 solar masses.

The orbit of Algol C is co-planar with the AB-orbit within some 3°, but polarimetry of the eclipsing pair indicates that the senses of revolution are opposite.

The close orbit is circular, thus the 32 year period in the times of minima can not be explained by apsidal motion.
Time-Resolved Spectroscopy of RW Tau and X Per
Authors: Kaitchuck R. H. , Honeycutt R. K. , Mufson S. L.
Published: July 2016

Time-resolved spectroscopy of the gaseous ring of RW Tau has revealed characteristics of its structure. Observations of H-alpha emission during one eclipse show a partial eclipse of the ring which is brighter at second contact than at third contact. The radial velocities became nearly constant after mideclipse. During two other eclipses the emission continued to strengthen after second contact. X Per has shown variability on a time scale of minutes. On one occasion H-alpha emission decreased in strength by a factor of two in 90 seconds.
Polarization Observations of U Cephei
Authors: Piirola V.
Published: July 2016

Polarimetric and photometric observations of U Cephei during the 1974-75 outburst are discussed. An optically thin envelope or disk cannot explain the observations. The polarization too small by a factor of 10, when compared with the amount of additional light during the totality of the eclipse of the B-star. This suggests that most of the additional light came from optically thick matter around the B-star, i.e. the effective radius of the photosphere of the B-star, rB, was increased by 15-20 % during the period of high mass transfer. The polarization observations could then be explained by a simple model containing an optically thin spherical envelope of outer radius 1.1 rB and an equatorial disk of outer radius 1.7 rB surrounding the expanded B-star. The mean electron density is about 1.4 × 1012 e/cm3 in the spherical envelope and 1.6 × 1012 e/cm3 in the preceding and 0.9 × 1012 e/cm3 in the trailing side of the disk, the thickness of which is assumed to be 0.1 rB normal to the orbital plane. The variations in the position angle can be explained if the inclination of the orbit is about 83°. The details will be published elsewhere.
Hα Observations of Algol-Type Interacting Binary Systems
Authors: Peters Geraldine J.
Published: July 2016

An observational study of the Hα feature in Algol type binary systems has revealed the presence of emission in nearly all systems with periods greater than 6 days. The disks which produce this emission are generally thin and can extend out to 90% of the Roche surface of the primary star. If emission is found in the systems of shorter period, it tends to be transient, lasting only a few orbital cycles. In several systems, there is evidence of mass loss from the vicinity of the primary at phase 0.5.
Non-Conservative Mass Exchange and Origin of X-Ray Close Binaries
Authors: Sugimoto Daiichiro , Miyaji Shigeki
Published: July 2016

Recently, masses of component stars have been determined for many X-ray close binaries (XCBS). For relatively well determined sources the masses of X-ray components are plotted against the masses of their optical components in Figure 1 and their orbital periods are summarized in Table 1 (Cowley 1977; Bradt, Doxsey, and Jernigan 1979; Wheeler 1978; and references quoted therein). Cowley (1977) prepared a table and noticed that there are two distinct types of XCBS. The Type I XCBS consists of an X-ray star and an early type star more massive than about 12 M⊙. On the contrary, the Type II XCBS consists of an X-ray star and a star less massive than about 2 M⊙. As seen in Figure 1, there is not any distinct intermediate type for which the mass of the optical component lies in the range of about 2-12 M⊙. The aim of the present paper lies in interpreting the origin of these types of XCBS on the bases of the conditions for the formation of a neutron star and of mass exchange in close binary systems.
Optical Observations of X-Ray Sources in the LMC
Authors: Pakull M.
Published: July 2016

Photoelectric and spectroscopic observations of optical counterparts of X-ray sources in the LMC are described.
Evidence for a 6 Year Periodicity in X Persei
Authors: Dorren J. D. , Guinan E. F.
Published: July 2016

Intermediate and narrow-band photoelectric observations obtained at Biruni and Villanova Observatories from 1977 to the present, when combined with previous data, strongly suggest that light increases of about 0.5 mag occur at 6 year intervals. Possible explanations are considered.

The X-ray pulsator X Persei (4U 0352+30) is an intriguing object at both X-ray and optical wavelengths. From the X-ray data a period of 13.9 minutes now appears well-established, but early suggestions of a 22.4 hour periodicity remain unconfirmed (White et al.,1976, Becker et al., 1979). The nature of the X-ray emission is unusual; the source is about 3 orders of magnitude weaker than other X-ray binary pulsars, and the spectrum contains a strong high-energy X-ray component (Mushotzky et al., 1977). Long known as an irregular variable, X Per has been classified as a Be star with an 09.5 (III-IV)e spectral type and showing broad hydrogen emission and absorption features (Brucato and Kristian 1972, Hutchings et al., 1975). A 581-day period is indicated by the radial velocity study of Hutchings et al., (1975). This has been variously interpreted as an orbital period (about a black hole) or an apsidal period, the models having in common accretion on to a neutron star as the source of the pulsed X-rays. In 1977 an increase in brightness of the star was observed by Kalv (1977) and Guinan et al., (1978), and by April 1979 we had accumulated sufficient evidence to suggest that X Per undergoes periodic (≃ 6-year) outbursts (Dorren et al., 1979a).
The Coronae of RS CVn Systems
Authors: Walter Frederick M. , Charles Philip A. , Bowyer Stuart
Published: July 2016

RS CVn systems [1] are close binaries consisting of two late-type stars, one of which has evolved to the base of the giant branch. In most cases, the systems appear to be the product of normal stellar evolutionary processes [2,3]. These systems have attracted much recent attention because they exhibit greatly exaggerated stellar activity in the form of strong chromospheric emission [1]. There is evidence that a large fraction of the surface is covered by dark spots [4]. They also exhibit radio emission [5,6], and quiescent and flaring soft X-ray emission [7-12]. If these stars are undergoing normal evolution, why then are they so peculiar?
Current Work on Cataclysmic Variables at Oxford and Cambridge
Authors: Bath G. T. , Brunt C. C. , Eggleton P. P. , Fabian A. C. , Harkness R. , Mayo S. K. , Papaloizou J. , Pringle J. E. , Rayne M. , Savonije G. S. , Whelan J.A.J. , Whyte C. A. , Wickramasinghe D. T.
Published: July 2016

This talk summarizes recent work that has been done on cataclysmic variables at Oxford and Cambridge. Full details should be sought elsewhere, either from the authors concerned or from the references given below.
IUE Observations of WZ Sagittae in Outburst
Authors: Holm Albert V. , Wu Chi-Chao , Sparks Warren M. , Schiffer Francis H. , Boggess Albert
Published: July 2016

The International Ultraviolet Explorer was used to obtain spectra at both 7 Å and 0.2 Å resolution of the recurrent nova WZ Sagittae during its 1978 outburst. The first spectra were obtained on 1978 Dec 1.8 UT, approximately 0.7 days after discovery. The decay from outburst was followed until 1979 Jan 1, after which it was too near the Sun to be observed. A post-outburst spectrum was obtained on 1979 July 11. In this paper, preliminary results from the analysis of the low resolution spectra are discussed. These observations will be used to support the similarity between WZ Sge and dwarf novae and to test accretion disk models.
Solar Type Contact Binaries - The Initial Mass Ratio Distribution Function.
Authors: Van 'T Veer Frans
Published: July 2016

From a study of the mass ratio function of magnetically active contact binaries it is shown that the great majority of newly formed systems must possess nearly equal components.
On Sudden Period Changes in Contact Binaries
Authors: Havnes Ove
Published: July 2016

We propose that sudden period jumps in contact binaries can be caused by the action of a third companion in a highly eccentric orbit of small periastron distance. Time jumps as observed are easily reproduced for a wide range in mass of the third body but observations may restrict the possible mass range to less than a few times 0.1 Mo.
The Symbiotic Binary System AG Pegasi
Authors: Keyes Charles D. , Plavec Mirek J.
Published: July 2016

A complete coverage of the spectrum of AG Peg has been obtained between wavelengths 1200 − 7000 A by us, and can be supplemented by IR photometric observations by others. Our IUE observations yield a lower value of E(B-V), about 0.12. The two stellar components are easily recognized, but their characteristics are still rather uncertain.

The cool component may be a normal M1.7 III giant, but the temperature and luminosity of the hot star remain largely indeterminate. Firstly, there are no good models for a hot subdwarf, and secondly, it is difficult to determine the relative contribution of the star itself and the surrounding hydrogen cloud.

The emission lines observed in the UV have double or triple structure, indicating two or three distinct emitting regions.
HD137569, a Population II Remnant of Mass Exchange Evolution
Authors: Bolton C. T. , Thomson J. R.
Published: July 2016

The temperature, surface gravity, and abundances derived for this halo B star by Danziger and Jura (1970, Ap.J., 161, 997) show that it is a field suprahorizontal branch star very similar to B29 in M13. The only difference is that HD137569 has a higher (solar) C abundance. We find that HD137569 is a spectroscopic binary with P=529.8(2) days, Vo=45.0(2) km/s, K=16.2(3) km/s, e=0.12(2), ω=233°(10), and T=JD2441922(14). The parenthesized quantities are the uncertainties (probable errors) of the last digits of the elements.
Some Thoughts on Interacting Binary Systems
Authors: Ulrich Roger K.
Published: July 2016

I present here some thoughts on the theory and observation of interacting binary systems. The complex physical processes possible in these systems make our present understanding inconclusive. New types of observation (X-ray, EUV, radio) present new challenges to the theoretician. I discuss here those problems which seem to me to hold the most promise for future progress and relate the papers in this conference to these problems.
Numerical filtering of refraction coefficients
Authors: Kahmen H.
Published: July 2016

The fluctuations of refraction coefficients can be described by a stochastic process: a two-component process. One component of the process is caused by short-periodic (daily) climatic variations. The other component is influenced by long-periodic (yearly) climatic variations. The central moments of these two components are used to estimate the covariance matrix of time series of refraction coefficients. Different functional and stochastic models are tested in connexion with time averaging of refraction coefficients.
Application of refractional effects in geodetic framework of Iraq by continuous trilateration
Authors: Pazus R.
Published: July 2016

Terrestrial refraction effect has been of considerable interest to many geodesists for many decades and there is a rich litterature on the subject, of long standing. Due to its local character this problem is still topical. Geodetic determination of how far terrestrial refraction influences geodetic observations is, therefore, very often studied.
Refractional effects in photogrammetry
Authors: Larsson J
Published: July 2016

A brief description of photogrammetric procedures are made to show how it has been and today is possible to make correction to photogrammetric measurements for the effect of refraction.

Then a review of how refractional effects have been calculated is made.

Finally some suggestions are made of how to meet the demands for improved accuracy in photogrammetric measurements.
Planned Observations of the Diffuse Sky Radiation During Shuttle Mission STS-4
Authors: Weinberg J. L. , Hahn R. C. , Giovane F. , Schuerman D. W.
Published: July 2016

The Skylab flight spare 10-color photopolarimeter (Weinberg, et al., 1975; Sparrow, et al., 1977) is being refurbished for use in Space Shuttle mission STS-4, a test flight currently scheduled for October 1980. Observations will be made of zodiacal light, background starlight, and the Shuttle-induced atmosphere (spacecraft corona), with emphasis on regions of sky closer than 90° to the sun.
Change in the Zodiacal Light with Solar Activity
Authors: Robley R.
Published: July 2016

The Gegenschein observed at the Pic du Midi Observatory during a solar cycle has a behaviour similar to that of the brightness of the eclipsed Moon. It is assumed that in both cases the solar wind ejected through the polar coronal holes is responsible for these variations.
Two Station Television Meteor Studies
Authors: Hawkes R. L. , Jones J.
Published: July 2016

Single station studies cannot provide detailed information such as zenith angle, velocity, heights and magnitude for individual meteors and Ceplecha (1976) has stressed the need for two station television observations which could provide such information through triangulation analyses. This paper deals with some of the results of the first two station television intensifier study of faint meteors, and the implications of these results concerning the validity of the current theories of the structure and ablation of dustball meteors.
On the Mass Distribution of Meteorites and Their Influx Rate
Authors: Hughes David W.
Published: July 2016

The problem of calculating the mass distribution of meteorites and their influx rate can be resolved into three sections; (a) the flux of meteorites hitting the surface of the Earth must be calculated (b) the mass distribution of these meteorites must be assessed, care being taken to include the effect of fragmentation in the atmosphere and (c) atmospheric ablation, which is a function of mass, velocity, composition and zenith angle must be taken into account. The final result will give the meteoritic influx to the Earth's upper atmosphere and its mass distribution.
Sources of Interplanetary Dust
Authors: Kresák Ľubor
Published: July 2016

It is generally assumed that ejections from active cometary nuclei are the major source of replenishment of the interplanetary dust complex. Conjectures against this concept are usually based on comparison of the quantitative efficiency of the dust production by comets with the efficiency of all the dissipative processes involved. The present paper discusses this problem from the dynamical point of view, tracing the evolution of swarms of cometary ejecta as they pass through different evolutionary stages. It is concluded that the contribution of the present population of active comets, of all revolution periods, is not only inadequate to explain the abundance of interplanetary particles, but also inconsistent with the distribution of their orbits. Other potential sources and their implications for the equilibrium problem are reviewed.
Nature of Dust Grains in the Atmosphere of Comet Ashbrook
Authors: Dobrovolsky O. V. , Kiselev N. N. , Chernova G. P. , Tupieva F. A. , Narizhnaja N. V.
Published: July 2016

Anomalous polarization at small phase angles is confirmed as a common feature of dusty cometary atmospheres. The opposition effect is detected and interpreted as evidence of similarity between grains covering interplanetary, cometary and asteroidal surfaces. The prevailing radii of dust grains in the comet's atmosphere are estimated to be 0.15-0.19 μm.
In Situ Measurements of Interplanetary Dust in the Inner Solar System
Authors: Grün E.
Published: July 2016

The Helios 1 spacecraft was launched in December 1974 into a heliocentric orbit of 0.3 AU perihelion distance. It carries on board a micro-meteoroid experiment which contains two sensors with a total sensitive area of 121 cm2. The ecliptic sensor measures dust particles which have trajectories with elevations from −45° to +55° with respect to the ecliptic plane. The south sensor detects dust particles from −90° to −4°. The ecliptic sensor is covered by a thin film (3000 Å parylene coated with 750 Å aluminium) as protection against solar radiation. The other sensor is shielded by the spacecraft rim from direct sunlight and has an open aperture. Micrometeoroids are detected by the electric charge produced upon impact and the ions are mass analysed in a time-of-flight-spectrometer. During the first 6 orbits of Helios 1 around the sun the experiment registered a total of 168 meteoroids, 52 particles were detected by the ecliptic sensor and 116 particles by the south sensor. Most impacts on the ecliptic sensor were observed when it was pointing in the direction of motion of Helios (apex direction). In contrast to that the south sensor detected most impacts when it was facing in between the solar and antapex directions. Orbit analysis showed that the “apex” particles which are predominantly detected by the ecliptic sensor have eccentricities e < 0.4 or semimajor axes a < 0.5 AU. From comparison with corresponding data from the south sensor it is concluded that the average inclination of these particles is below 30°. The excess of impacts on the south sensor have orbit eccentricities e > 0.5 AU. β-meteoroids which leave the solar system on hyperbolic orbits are directly identified by the imbalance of outgoing (away from the sun) and ingoing particles. Mass analyses of the spectra showed that 40% of the observed spectra have the peak abundance above mass 35 amu which are preliminarily identified as iron meteoroids. 40% of the spectra have the peak abundance below mass 35 amu which correspond to chondritic composition. 20% of the spectra could not be identified in either class.
Electromagnetic Effects on the Zodiacal Dust Cloud
Authors: Grün E. , Morfill G. E.
Published: July 2016

Electromagnetic effects on charged zodiacal dust particles were investigated. It can be shown that: 1) stochastic variations induced by electromagnetic forces are unimportant for the zodiacal dust cloud except for the lowest masses, 2) systematic variations in orbit inclinations are unimportant if orbital radii are larger than 10 A.U. This is due to the solar cycle variation in magnetic polarity which tends to cancel out systematic effects, 3) systematic variations in orbital parameters (inclination, longitude of ascending node, longitude of perihelion) induced by electromagnetic forces inside 1 A.U. tend to shift the plane of symmetry of the zodiacal dust cloud somewhat towards the solar magnetic equatorial plane, 4) inside 0.3 A.U. there is a possibility that dust particles may enter a region of “magnetically resonant” orbits for some time. Changes in orbit parameters are then correspondingly enhanced, 5) the observed similarity of the plane of symmetry of zodiacal light with the solar equatorial plane may be the effect of the interaction of charged interplanetary dust particles with the interplanetary magnetic field. Numerical orbit calculation of dust particles show that one of the results of this interaction is the rotation of the orbit plane about the solar rotational axis.
Thermomagnetic Study of Chondrules
Authors: Lang B. , Pekala M. , Krôl E. , Nowakowski A. , Martin P. , Stakheev Yu. , Baryshikova G.
Published: July 2016

Thermomagnetic and saturation magnetization curves were obtained for separate chondrules and fine matrix grains from one H- (Allegan) and four L-type (Bjurböle, Elenovka, Saratov, Nikolskoe) chondrites. Mineralogical and petrological data were recovered from chondrule thin sections. The differences observed in the obtained curves seem to suggest episodes in the story of chondrules predating their incorporation into matrices.
Radiation induced Rotation of Interplanetary Dust Particles; a Feasibility Study for a Space Experiment
Authors: Ratcliff Keith F. , Misconi Nebil Y. , Paddack Stephen J.
Published: July 2016

Irregular interplanetary dust particles may acquire a considerable spin rate due to two non-statistical dynamical mechanisms induced by solar radiation. These arise from variations in surface albedo as discussed by Radzievskii (1954) and from irregularities in surface geometry as discussed by Paddack (1969). We report on an experiment which will lead to an evaluation in space of the effectiveness of these two spin mechanisms. We utilize the technique of optical levitation in an argon laser beam to provide a stable trap for particles (10-60 microns in diameter). The spin rate and direction of the spin axis are measured in a straightforward manner. The objective is to design an optical trap for dielectric particles in vacuum which can be used to study these rotation mechanisms in the gravity-free environment of a Spacelab experiment.
Search for Giant Cells in the Solar Convection Zone
Authors: Labonte B. J. , Howard R.
Published: July 2016

The Mount Wilson Observatory has obtained daily full disk digital magnetograms of the Sun since 1966, with 12 to 17 arcsecond resolution. As each magnetogram is taken, the position of the Doppler line shift compensator is also recorded, thus giving a full disk map of the longitudinal velocity. This entire dataset is currently being rereduced on a uniform basis (Howard et al., 1980), and daily arrays of residual velocities are being formed by removing large scale patterns, e.g., Earth's motions, solar rotation, limbshift. Data from the years 1972 through 1978 are used here.
Solar Observations with a New Earth-Orbiting Coronagraph
Authors: Sheeley N. R. , Howard R. A. , Michels D. J. , Koomen M. J.
Published: July 2016

Since March 28, 1979, the Solwind coronagraph has been observing the Sun's white light corona (2.6 − 10.0 R⊙) routinely with a spatial resolution of approximately 1.25 arc min and a repetition rate of 10 minutes during the one-hour sunlit portion of each 97-minute satellite orbital period. These are the first satellite observations of the outer corona near the peak of a sunspot cycle when coronal transients and high-latitude streamers are common.
X-Ray Structures Associated with Disappearing Hα Filaments in Active Regions
Authors: Kahler S. W.
Published: July 2016

Several studies using data from Skylab instruments have been carried out to determine the spatial and temporal relationships between disappearing Hα filaments and the associated coronal emission features. Webb et al. (1976) studied 30 transient coronal X-ray enhancements which could be associated with the disappearances of Hα filaments outside active regions. They found that in the early phase of the transient X-ray brightening, emitting structures appeared at or near the filament location with shape and size resembling the filament. Sheeley et al. (1975) examined a long-lived X-ray enhancement of expanding loops associated with an active region filament which disappeared. Rust and Webb (1977) found a good statistical correlation in time and position between large scale (length > 60, 000 km) active region X-ray enhancements and Hα filament activity, in particular, events of an eruptive nature.
Solar Radar Observations
Authors: Benz A. O.
Published: July 2016

Radar observations of the sun have been made extensively at decameter and low meter wavelengths (Eshleman et al., 1960, and James, 1966). Their interpretation by specular reflection on high density structures with “corner reflector” shape is unlikely from the echo spectral broadening and range depth. Gordon's (1973) interpretation of the scattering by a 4 wave interaction between radar and coronal Langmuir waves requires a level of 10−2nKT (thermal energy density) of the Langmuir waves. A radar experiment in microwaves with the 300 m dish in Arecibo*) is described, which was able to test this hypothesis. It was based on the idea of scattering radar waves on Langmuir waves by the much more efficient 3 wave interaction. The echo at the beat frequency of the radar (2380 MHz) and the Langmuir wave (170 −270 MHz) is then to be expected at 2600 MHz. The results, however, show the absence of echos, from which an upper limit of 6.10−4nKT for the level of Langmuir waves is derived. First results will soon be published (Benz and Fitze, 1979).
Spicules and Macrospicules
Authors: Van Tend W.
Published: July 2016

The transition zone overheating model and the melon seed model are compared with observations of spicules, macrospicules, surges and sprays.
Recent Observations of Energetic Electrons in Solar Flares
Authors: Kane S. R.
Published: July 2016

It has been apparent for the last few years that a large fraction of the total energy released during a solar flare appears initially in the form of energetic electrons accelerated during the impulsive phase. An estimate of the energy of these electrons is based on the observed hard x-ray spectra as well as the assumed form (thermal or non-thermal) of the electron distribution. Even after the basic form of the electron distribution is assumed, additional assumptions, such as the low energy cut-off in the case of the power law energy spectrum or existence of a multi-thermal source in the case of the thermal spectrum, are usually required. In order to test these assumptions, measurements of the hard x-ray spectrum with spatial resolution and covering a wide range of x-ray energy are essential. In absence of good spatial resolution, as is the case with most of the presently available hard x-ray observations, the impulsive x-ray emission at energies hv ≲ 10 keV is often unobservable because of the presence of a large background of relatively intense gradual emission associated with most flares. Observations made in the past suffered either because of the lack of a clearly identifiable impulsive x-ray emission at low energies (Peterson et al, 1973) or an adequate spectral resolution (Kahler, 1973). Thus so far it has not been possible to measure unambiguously the spectrum of impulsive x-rays ≲ 10 keV and hence to deduce a possible low energy cut-off in the energetic electron spectrum. Here we report briefly such an observation made with the ISEE-3 x-ray spectrometer experiment and its implications with regard to the characteristics of energetic electrons in solar flares.
An Energy Storage Process and Energy Budget of Solar Flares
Authors: Tanaka K. , Smith Z. , Dryer M.
Published: July 2016

The flare energy is generally considered to be stored in stressed (twisted or sheared) magnetic fields. Origin of the stress may be either intrinsic or due to horizontal shear motion (Tanaka and Nakagawa 1973) or due to propagation of twist from below (Piddington 1974). Characteristic magnetic configurations in the great activities (inverted, twisted δ-configuration; Zirin and Tanaka 1973) suggest an inherent shape of fluxtube for these regions: a twisted magnetic knot. Further, evolutionary characteristics such as rapid growths of spots and growth of twist in parallel with apparent shear motion of spot, together with the fact that the shear motion is associated with upward velocity (Tanaka and LaBonte 1979), suggest a continuous emergence of such a twisted knot from below throughout the activity (Tanaka 1979). In this model (Fig. 1) the flare energy may be supplied directly into the corona as the twisted portion of the fluxtube emerges out. The amount of energy supplied between t0 and t may be equated to the energy contained in the twist (ɸ) between z1 and z2,
Evidence for Open Field Lines from Active Regions: Short Communication
Authors: Sheridan K. V.
Published: July 2016

A paper that has considerable relevance of the subject matter of this symposium is the following: “Evidence for Extreme Divergence of Open Field Lines from Solar Active Regions,” by G. A. Dulk (Division of Radiophysics, CSIRO, Sydney, Australia and Department of Astro-Geophysics, University of Colorado, Boulder, Colorado), D. B. Melrose (Department of Theoretical Physics, University of Sydney, Australia) and S. Suzuki (Division of Radiophysics, CSIRO, Sydney, Australia).