bluuebunny/crossref_metadata_2025 huggingface dataset:
Relative CNO Abundances in Upper AGB Stars of the Magellanic Clouds. A Search for Envelope Burning
Authors: Brett J.M. , Bessell M.S.
Published: July 2016

We have investigated the atmospheric abundances of upper AGB stars of the SMC, searching in particular for evidence of the hypothetical envelope burning process. To this end we have computed synthetic spectra with varying C, N, and 0 abundances selected by considering the effect of the processes of the 3rd dredge up and envelope burning of a degree sufficient to prevent C star formation. The synthetic spectra (covering 0.5 μm to 2.5 μm) were analysed for observable effects of these two atmospheric enrichment processes. By analysis of band strengths of TiO, CO and CN we have found that substantial envelope burning is detectable for stars with Teff ≥ 3000 K but not below, due to the temperature dependence of CN bands. The synthetic spectra were compared to near-infrared and infrared observations of a small sample of SMC upper AGB stars thought to be prime candidates for the occurrence of envelope burning. This comparison indicated that envelope burning, of the extent considered here, is not occurring in these stars but rather the spectra are consistent with mild C enhancements produced by the 3rd dredge up alone.
S-Process Deficiencies in Low-Mass Supergiant Variables
Authors: Bond Howard E. , Luck R. Earle
Published: July 2016

We have carried out abundance analyses of four low-mass supergiant variable stars (the RV Tauri or RV Tau-like variables AI Cmi, RU Cen, and U Mon, and the Type II Cepheid Kappa Pav) and two Population I Cepheids (CO Aur and V378 Cen). We used model atmospheres in which hydrostatic equilibrium, plane-parallel geometry, and local thermodynamic equilibrium (LTE) were assumed. Discussion of the results, and of published analyses of additional low-mass variables, leads to the following conclusions. (1) The Population I Cepheids show normal, solar elemental abundance ratios (except for the CNO elements, which have been altered by hydrogen burning), lending some support to the validity of the above assumptions for analyses of luminous variable stars. (2) The low-mass variables show metallicities ranging from solar down to [Fe/H] values typical of thick-disk and, in a few cases, of halo stars. (3) Most low-mass variables show a systematic underabundance of the heavy s- and r-process elements. In a few cases this may indicate that the stars were initially of extremely low metal content, and are now hydrogen deficient. However, most of the variables do not appear to belong to the halo population, nor do they show other abundance patterns seen in halo stars. The origin of these underabundances, and their apparent confinement to luminous variables, are difficult to understand in the context of nuclear processing. (4) The heavy-element underabundances correlate with second ionization potential in a manner suggesting that they are non-LTE phenomenan arising from overionization by Lyman-continuum photons. Why a similar effect is not seen in Population I Cepheids is unclear, but may be related to their generally weaker hydrogen emission. (5) Several low-mass variables, including RU Cen and V553 Cen, show carbon enhancements and solar s-process abundances. Relative to the majority of the Type II variables, these stars are s-process enhanced, and we argue that they are related to the Ba II and CH stars.
s-Process Enrichment in Low-Mass Agb Stars
Authors: Gallino R.
Published: July 2016

After a brief description of the developments of the theory of s-process nucleosynthesis, the difficulties recently encountered in envisaging reliable astrophysical conditions for obtaining a solar-system distribution of s-isotopes are discussed. In particular, while the reaction 22Ne(α, n)25Mg may account for the nucleosynthesis of the weak s-component in massive stars, it fails to reproduce the main s-component in intermediate mass stars. The efficiency of the alternative reaction 13C(α, n)160 occurring in low mass stars during recurring thermal instabilities of the He shell is then analyzed. It is shown that, contrary to previous expectations, the 13C source well reproduces the main component, provided that realistic physical conditions are assumed for the temporal behaviour of the pulse and the effect of the light n-absorbers (especially 12C) is properly taken into account. The results satisfactorily compare with the constraints of the classical s-analysis. Key observational evidences also appear to be in agreement with this scenario.
Evolution of a Star of 7 MΘ With Mass Loss
Authors: Runqian Huang , Suyun Jiang
Published: July 2016

The evolution of a Population I star of 7 MΘ with mass loss has been followed. The mass-loss rates of the star are calculated by using the empirical relation of Waldron (1984) and the formula introduced in this paper. In the red supergiant stage there occur thermal pulses of the He-burning shell source either for the evolution with constant mass or for the evolution with the mass loss rate calculated by Waldron's relation. The rate of mass loss will become very large before the occurence of thermal pulses of He-burning shell source and the envelope of the star can be lost in a short period of time, if the introduced formula of the mass loss rate is used. The effects of mass loss on the internal structure and the evolution of the star, especially on the He-burning shell source are considered in detail.
5 Ceti: A Long-Period Binary Evolving Through Mass Exchange
Authors: Eaton Joel A.
Published: July 2016

Binaries with very wide spearations are thought to evolve to small separations through a catastrophic form of mass exchange/loss known as common-envelope evolution. The theory of this process is fairly well developed, but proper tests remain elusive. Simply put, the theory argues that the rapidly shrinking Roche lobe of the mass losing giant will strip away the giant's main-sequence companion. Loss of mass from the system during the process carries away orbital angular momentum, thereby strengthening the effect.
The N/O-Core Mass Relation in Planetary Nebulae
Authors: Kaler J.B. , Shaw R.A. , Kwitter K.B.
Published: July 2016

We define the relationship between nitrogen enrichment in planetary nebulae and the mass of the nucleus. N/O remains flat at about 0.3 (double solar) from a core mass of 0.55 M(sun) to 0.8 M(sun), whereupon it rises quickly to values that approach and may exceed 2. The rate of increase of N/O with core mass exceeds that predicted for giant stars by standard dredge-up and mass-loss theories.
Irregular Red-Giant Variable Stars
Authors: Querci M. , Querci F.
Published: July 2016

Aperiodic intrinsic variability becomes increasingly evident for a greater number of red giant and supergiant stars as observations become more technically refined and extended over a longer time. All red variables show an erratic temporal behavior to some degree. Even Miras, with their temporal changes in maximum brightness and irregular fluctuations in the cycle length, are not perfect clocks.
IRAS LRS Spectral Class and Light Curve of M & S Miras
Authors: Vardya M.S.
Published: July 2016

A large sample of 177 Miras, comprising 164 M and 13 S stars, has been examined to determine the dependence of 9.7 μm silicate emission, as revealed by their IRAS LRS Spectral class, on the visual light curve asymmetry factor, f. It is found that the silicate feature occurs not only in M (Vardya et al. 1986; Onaká & de Jong 1987) but in S Miras also only for f ≤ 0.45. This, however, is only a necessary condition, as about one fifth of Miras with f ≤ 0.45 do not show the 9.7 μm emission. This non-detection shows dependence on other parameters like the mean visual light amplitude. Non-detection is highest in the region 0.43 < f ≤ 0.45, as well as when mean amplitude is ≤ 5m.0. Though strong emission features in M Miras may occur for any value of f, very weak features are absent for small values of f, and the strongest feature tends to appear for large values of f. Infrared excess tends to increase with increase in the strength of the silicate emission and with decrease in the value of f.
Molecular Radio Line Observations of Mass Loss From Red Giants
Authors: Olofsson H.
Published: July 2016

The number of molecules detected at radio wavelengths in envelopes around red giants stands presently at 36. Among these OH and CO have proven to be the most useful for the study of the physical characteristics of a circumstellar envelope. The mass loss rate of the central star can be relatively accurately estimated and it appears possible to trace its evolution with time. Also fascinating objects in transition from the red giant phase to the planetary nebula phase are becoming observationally accessible.
ER Del: A True Symbiotic S Star?
Authors: Johnson Hollis R. , Ake Thomas B.
Published: July 2016

ER Del = BD+8:4506 is a faint (m ≈ 10) irregularly variable PRG star classified spectral type S5.5/2.5 (Ake 1979). Spectra show H alpha in emission and a strong UV continuum with emission lines of C IV, Si III], and C III] — characteristic of symbiotic-like stars. Although a few other MS and S stars have hot companions, this is the first to show hydrogen emission lines in the optical region. It has been suggested (Smith & Lambert 1986; Little et al. 1987) that all Tc-deficient PRG stars are accidental; that is, they arose by mass transfer when the currently degenerate companion was itself an AGB star. Indeed, the Tc-deficient S stars HR 1105 (Ake, Johnson and Peery 1988) and HD 35155 (Ake and Johnson 1988) and the R8 star HD 59643 (Johnson et al. 1988) not only have hot, subluminous companions, but also are interacting systems - a sign the components are close enough for mass transfer to have occurred. An accretion disk is probably present.
Possible Proto-Planetary Nebulae
Authors: Parthasarathy M.
Published: July 2016

IRAS data for high-galactic-latitude F supergiants, a few luminous F-G stars, and a few peculiar (forbidden) emission-line stars reveal they have dust shells with characteristics similar to those observed in planetary nebulae. The objects described here appear to have experienced severe mass loss in the recent past on the AGB. These stars are most likely post-AGB stars or evolving from the tip of AGB towards the left in the H-R diagram and may be described as possible proto-planetary nebulae. From the IRAS data we find ten additional possible proto-planetary nebulae. From the IRAS data of HD 56126, -53° 5072, HD 168625 and -59° 6723 the luminosities, temperatures and masses of the dust shells are derived. HD 56126 (F5I), HD 168625 (B8Iae), and -59° 6723 (B8Iae) appear to be in an evolutionary stage (post-AGB) similar to that of HD 161796 and HR 4049.
IRAS Observations of Symbiotic Stars
Authors: Parthasarathy M. , Bhatt H.C.
Published: July 2016

Of the 129 symbiotic stars in Allen's (1984) catalogue, 42 were found to be IRAS sources. Of these 42 IRAS sources, 22 are D-type (symbiotic Miras), 5 are D'-type (yellow symbiotics) and 15 are S-type. The separation of S, D and D’ types into three distinct groups is clearer in the log[fλ(25μm)/fλ(12μm)] versus (H-K) diagram. The IRAS fluxes of S-type symbiotics are consistent with that observed from normal M giants. This result suggests that mass-loss rate from most of the S-type symbiotics is similar to that from normal M giants. The IRAS data of D-type symbiotics shows evidence for the presence of dust envelopes. The masses of the dust envelopes (10-6 to 10-7 Mo) around Miras in D-type symbiotics are similar to that observed in field Mira variables. These results suggest that mass-loss rates in symbiotic Miras are similar to those from field Mira variables and also that the mass loss from symbiotic Miras is pulsationally driven similar to that found in field Mira variables by Whitelock, Pottasch and Feast (1987). Analysis of IRAS data of yellow symbiotics Ml-2, AS201, Cnl-1, Wray 157. and HD149427 suggests that they are young planetary nebulae containing a binary nucleus. Ml-2, AS201 and Cnl-1 show evidence for the presence of evolved hot companions. The evolutionary stage of the late type (F-G) companions is not clear.
Activity Report of the IAU Working Group on Reference Systems Sub-Group on Astronomical Constants
Authors: Fukusfflma T.
Published: July 2016

The IAU Working Group on Reference Systems (WGRS) Sub-Group on Astronomical Constants (SGAC) was established in June, 1989, as a consequence of resolutions adopted by Commissions 4, 7, 8 and 24 at the IAU General Assembly at Baltimore in 1988. The given missions of this sub-group were stated clearly by J. Hughes, the chairman of the WGRS, as:

“Provide numerical values for the primary constants and specify the relationships between these and other, secondary constants within the framework of general relativity. This task will involve the documentation of the constants themselves as well as of the procedures and algorithms associated with their use. Recognition must be given to the fact that approaches which are specific to various techniques exist. The group must recommend the best estimates which can meet the varied requirements of astronomy. The apparent dichotomy between adopting fixed values for various quantities on the one hand, and the need for current, highly accurate values on the other hand, must be addressed by the group. Indeed, the crafting of effective procedures for incorporating new determinations into the values assigned to the constants, and the setting up of a mechanism for disseminating information regarding new determinations as an interim measure, are important tasks for this group.”

This is a report of the activity of the SGAC prior to IAU Colloquium No.127. Section 2 summarizes the questionnaire prepared in trie course of discussion. In Section 3, the discussions on major issues are introduced. The drafts of Recommendations from the SGAC prepared before the Colloquium are shown in Section 4. Note that these drafts were very different from the final form as indicated in this Proceeding. Sections 5 and 6 deal with the current status of astronomical constants used widely now and the best estimates of some major constants which are available now, respectively. I believe these will serve as a guideline for current astronomical constants.
The Necessary Procedures to Reach an Agreeable Reference Frame: –Counter-Proposal to the Circular Letter N° 4 of Kovalevsky–
Authors: Aoki Shinko
Published: July 2016

The procedures are summarized in order to obtain a reference system which is available at the present moment and in the near future for the astronomical purposes. The target of the present discussions is the IAU General Assembly to be held in the summer of year 1991, in order to find out an agreeable result there. Discussions beyond this are postponed to a further occasion.
The Linkage Between Radio and Optical Coordinate Systems: Program Confor
Authors: Kumkova I.I. , Tel“njuk- Adamchuk V.V. , Bashtova L.I. , Dick W.R. , Inasariose R.Ya. , Irkaev B.N.
Published: July 2016

The present status and prospects of program CONFOR-Connection of Frames in Optic and Radio, are described. It is supposed that positions of extragiactic objects and intermediate stars in 200 areas will be obtained in FK5 system.
Stability of the Extragalactic Reference Frame Realized by VLBI
Authors: Ma C. , Shaffer D.B.
Published: July 2016

The 318 compact extragalactic radio sources with positions derived from dual frequency Mark III VLBI data acquired by the geodetic and astrometric programs of NASA, NOAA, NRL and USNO form a celestial reference frame with stability in orientation and relative position at the 1 mas level. This paper examines the reference frame realized using 461,000 observations from 1021 observing sessions between 1979 August and 1990 August in the NASA Crustal Dynamics Project VLBI data base. Catalogs of positions estimated from subsets of data (annual, seasonal, network) show differences in orientation typically less than 1 mas provided precession and nutation are adjusted using a reference day. For 17 sources with >5 year time span and >200 one-day position estimates, the rates of change of right ascension and declination are generally less than 5 mas/century, giving upper limits on real motion.
The Orientation of the Dynamical Reference Frame
Authors: Williams J.G. , Dickey J.O. , Newhall X X , Standish E.M.
Published: July 2016

We summarize the current status of the JPL ephemerides, focusing on the various data types utilized, especially the impact of the modern ranging data, and the resulting accuracies obtained. The dynamical equinox, as determined from the analysis of Lunar Laser Ranging data, is determined with an accuracy of 5 mas and the obliquity to a 2 mas level in ~1983, the weighted center of data. Knowledge of the lunar and planetary positions with respect to the dynamical equinox degrades to 10 mas at J2000. Twenty years of LLR data allow for the separation of the 18.6 yr nutation terms from the precession constant. The correction to IAU precession is found to be −2.7 ± 0.4 mas/yr, while the 18.6 yr nutation of the pole is 3.0 ± 1.5 mas larger in magnitude than the 1980 IAU series. The necessity of different reference systems and the accurate knowledge of the interconnections between frames is addressed.
A Terrestrial Reference System Consistent with WGRS
Authors: Boucher C. , Altamimi Z.
Published: July 2016

The IAU and IUGG has jointly established in 1988 an International Earth Rotation Service (IERS) which is in charge of the realization of conventional celestial and terrestrial reference systems, together with the determination of earth orientation parameters which connect them.

The theoretical definition of the terrestrial reference system which is realized by IERS through a conventional terrestrial reference frame formed by SLR, LLR, VLBI and GPS stations is presented. In particular its origin, scale, orientation and evolution with time are reviewed, taking into account relativistic and deformation effects.
Present Status of Work on the FK5 Extension
Authors: Corbin Thomas E. , Schwan Heiner
Published: July 2016

The FK5 Extension, consisting of 3117 new fundamental stars selected from the FK4 Sup catalogue and the IRS list, will extend the FK5 system to about 9.5th visual magnitude. The construction of the FK5 Extension is briefly described and the main characteristics are given.
Optical Astrometry and the Global Positioning System
Authors: Kammeyer P.C. , Fliegel H.F. , Harrington R.S.
Published: July 2016

Astrometric accuracies of a few tens of milliarcseconds are expected to be attainable within five years by calibrating astrograph plates with optical observations of Global Positioning System (GPS) satellites against a stellar background. The line of sight from an observer on the Earth’s surface to a GPS satellite may be calculated with high accuracy. Motion on each day of the line of sight to the satellite and changes from day to day in the apparent path of the satellite are sufficiently slow to make it possible to reduce atmospheric errors by averaging. Advanced ground-based optical sensors, probably using charge coupled device technology, will be required for GPS optical astrometry.
Third General Catalogue of Stars Observed with the Photoelectric Astrolabes
Authors: Lizhi Lu
Published: July 2016

On the basis of the data observed with the Photoelectric Astrolabes in China observed during the period from 1982 to 1990, the general catalogue is compiled. With magnitudes ranging from 0m.l to 7m.3, the general catalogue consists of 2577 stars spreading from δ=−3° to δ= 69°, in which 955 are FK5 stars and 1622 are GC stars. The mean precisions of 2577 Δα’s and 1892 Δδ’s are ±4.0 ms and ±0”.065, respectively. The mean epoch of the catalogue is 1987.4. Finally systematic corrections of (CAT—FK5) are given.
Precession Theory Using the Invariable Plane of the Solar System
Authors: Owen W.M.
Published: July 2016

Standard precession theory builds up the precession matrix P, which rotates coordinates from the mean equator and equinox of epoch to the mean equator and equinox of date, by a sequence of three elementary rotations by the accumulated Euler angles ϚA, θA and zA: P = R3(−zA)R2(θA)R3(−ϚA). This scheme works well provided both the epoch and the date are within a few centuries of J2000. For long-term applications, the alternative formulation using the accumulated luni-solar and planetary precession, P = R3(ᵡA)R1(−ѡA)R3(−ψA)R1(ɛ), is more stable.

Yet another formulation for P is possible, using the invariable plane of the Solar System as an intermediate plane: P = R3(−L) R1(−I) R3(−Δ) R1(I0) R3(L0). The angles I0 and L0 are the inclination and ascending node of the invariable plane at epoch; I and L are the same quantities at the date. Only the angle Δ is a function of both times. This scheme works for both short-term and long-term applications.

For the short term, polynomial coefficients for I, L, and Δ are derived from the currently-accepted coefficients of the angles ϚA, θA and zA. For the long term, these angles are expressed as sums of Chebyshev polynomials obtained from analysis of a million-year numerical integration.

If the intersection of the mean equator and the invariable plane were adopted as the origin of right ascensions, the theory would be simplified further: since L0 and L would no longer be required, P would again consist of the minimum three rotations.
New High Resolution Observations of the Solar Diameter from Space and Ground with the Microsatellite Program PICARD
Authors: Damé Luc
Published: July 2016

The PICARD microsatellite mission will provide 2 to 6 years simultaneous measurements of the solar diameter, differential rotation and solar constant to investigate the nature of their relations and variabilities. The 100 kg satellite has a 40 kg payload consisting of 3 instruments which will provide an absolute measure (better than 10 milliarcsec) of the diameter and the solar shape, a measure of total solar irradiance, and UV and visible flux in selected wavelength bands. Now in Phase B, PICARD is expected to be launched before mid-2003. The engineering model of the diameter telescope will be used on ground simultaneously with the satellite to investigate the atmospheric bias and state on the possible accuracy of the ground measurements carried up to now. We review the scientific goals linked to the diameter measurement, present the payload, and give a brief overview of the program aspects.
Solar Filaments as Tracers of Subsurface Processes
Authors: Rust D. M.
Published: July 2016

Solar filaments are discussed in terms of two contrasting paradigms. The standard paradigm is that filaments are formed by condensation of coronal plasma into magnetic fields that are twisted or dimpled as a consequence of motions of the fields’ sources in the photosphere. According to a new paradigm, filaments form in rising, twisted flux ropes and are a necessary intermediate stage in the transfer to interplanetary space of dynamo-generated magnetic flux. It is argued that the accumulation of magnetic helicity in filaments and their coronal surroundings leads to filament eruptions and coronal mass ejections. These ejections relieve the Sun of the flux generated by the dynamo and make way for the flux of the next cycle.
Polar Magnetic Field Reversals of the Sun in Maunder Minimum
Authors: Makarov V. I. , Tlatov A. G.
Published: July 2016

A possible scenario of polar magnetic field reversal of the Sun during the Maunder Minimum (1645–1715) is discussed using data of magnetic field reversals of the Sun for 1880–1991 and the14Ccontent variations in the bi-annual rings of the pine-trees in 1600–1730 yrs.
On the Possibility of Radio Emission from Quasi-parallel and Quasi-perpendicular Propagation of Shocks
Authors: Shanmugaraju A. , Umapathy S.
Published: July 2016

A set of 21 solar type II radio bursts observed using Hiraiso radio spectrograph have been analysed to study the direction of propagation of coronal shocks. A simple analysis is carried out to find the approximate angle between the shock normal and magnetic field by solving the Rankine-Hugoniot MHD relation with assumption of Alfven speed and plasma beta. From this analysis, it is suggested that both quasi-parallel shocks (favourable) and quasi-perpendicular shocks can generate type II bursts depending upon the circumstances of the corona.
Infrared Photometry of Solar Active Regions
Authors: Sobotka M. , Vázquez M. , Cuberes M. Sánchez , Bonet J. A. , Hanslmeier A.
Published: July 2016

Simultaneous time series of broad-band images of two active regions close to the disk center were acquired at the maximum (0.80μm) and minimum (1.55μm) continuum opacities. Dark faculae are detected in images obtained as weighted intensity differences between both wavelength bands. The elements of quiet regions can be clearly distinguished from those of faculae and pores in scatter plots of brightness temperatures. There is a smooth transition between faculae and pores in the scatter plots. These facts are interpreted in terms of the balance between the inhibition of convective energy transport and the lateral radiative heating.
Electron Density and Temperature Measurements, and Abundance Anomalies in the Solar Atmosphere
Authors: Mohan Anita , Dwivedi Bhola N. , Landi Enrico
Published: July 2016

Using spectra obtained from the SUMER (Solar Ultraviolet Measurements of Emitted Radiation) spectrograph on the spacecraft SOHO (Solar and Heliospheric Observatory), we investigate the height dependence of electron density, temperature and abundance anomalies in the solar atmosphere. In particular, we present the behaviour of the solar FIP effect (the abundance enhancement of elements with first ionization potential < 10 eV in the corona with respect to photospheric values) with height above an active region observed at the solar limb, with emphasis on the so-called transition region lines.
Ulysses Observations of Nonlinear Wave-wave Interactions in the Source Regions of Type III Solar Radio Bursts
Authors: Thejappa G. , MacDowall R. J.
Published: July 2016

The Ulysses Unified Radio and Plasma Wave Experiment (URAP) has observed Langmuir, ion-acoustic and associated solar type III radio emissions in the interplanetary medium. Bursts of 50–300 Hz (in the spacecraft frame) electric field signals, corresponding to long-wavelength ion-acoustic waves are often observed coincident in time with the most intense Langmuir wave spikes, providing evidence for the electrostatic decay instability. Langmuir waves often occur as envelope solitons, suggesting that strong turbulence processes, such as modulational instability and soliton formation, often coexist with weak turbulence processes, such as electrostatic decay, in a few type III burst source regions.
Ca+ (H and K), Hα and Hβ Emission Observed Simultaneously in Quiescent Prominences
Authors: Stellmacher G.
Published: July 2016

Integrated total emissions of the lines Ca+H, Ca+K, Hα and Hβ observed simultaneously in quiescent prominences are discussed. While the total line emission calculated with the recent, most advanced prominence model by Heasley and Milkey (1978) fits well the observed means, the observed“fine-structure”of the emission relations is not reproduced. This“fine-structure”is best seen in Engvold’s (1978) data, where the observed brightness relation E(Ca+K) vers. E(Hα) shows a pronounced branching, (Figure 1).
Orientation of Prominence Microstructure Relative to the Direction of the Magnetic Field
Authors: Engvold O. , Leroy J.L.
Published: July 2016

Recent measurements of the polarization of the Hel D3 line (λ5876Å) in solar prominences (Hanle effect) have been used to infer new data about prominence magnetic field (Leroy 1977, Leroy et al. 1977, Sahal-Brèchot et al. 1977). The derived field strengths are in good agreement with previous magnetographic measurements obtained at several observatories in USA (Rust 1972). Using the Hanle effect also gives the direction of the magnetic field, which is a crusial parameter in theories of prominences (Kippenhahn and Schlüter 1957, Anzer 1968, Malville 1976). Some theories require a horizontal oriented magnetic field in the prominences. High quality optical observations, on the other hand, resolve predominantly vertically oriented prominence microstructure (Dunn 1972, Engvold 1976).
A Modified Kippenhahn-Schlüter Model for Quiescent Prominences
Authors: Priest E.R. , Milne A.M. , Roberts B.
Published: July 2016

In this paper we consider the effect of varying magnetic field strengths and shears on a model quiescent solar prominence. Following Kippenhahn and Schlüter (1957) the prominence is modeled by a one-dimensional slab configuration. Their work extended to include thermal effects, using an energy equation which expresses a balance between thermal conduction, radiative loss and wave heating. At some specified distance from the center of the prominence, the coronal temperature and pressure p1are prescribed while at the prominence center there are two symmetry conditions, so that we have a two-point boundary value problem. For a detailed discussion of the model the reader is referred to Milne, Priest and Roberts (1979).
A Magneto-Hydrodynamic Study of Pre-Flare Loops
Authors: Hasan S.S.
Published: July 2016

The aim of this paper is to discuss the equilibrium and stability of a configuration which may apply to pre-flare loops on the Sun. The analysis is based on the following working scenario:

a)

The loops exist much prior to the flare and in equilibrium with their surroundings.

b)

Gradually, starting probably a few hours before the flare, the configuration acquires energy in the form of currents.

c)

During the period of energy build-up, the loops are MHD stable.

d)

The flare occurs only after there is adequate energy in the currents.
On the Rotational Velocity of Fine Solar Structures Deduced from the Inclination to the Direction of Dispersion of Their Spectral Streaks
Authors: Rompolt B. , Mzyk S.
Published: July 2016

Observational material indicates that matter in some streamers and knots of prominences rotates (Rompolt, 1975a). We would like to propose a method which enables evaluation of the rate of rotation of such structures from their spectral streaks inclined to the direction of dispersion. These considerations concern fine prominence structures, the image of which is comparable with the width of the spectrograph slit. The matter in these structures is assumed to rotate as in a solid rod.
X-Ray Emission Associated with Filament Activity
Authors: Acton L.W. , Mosher J.M.
Published: July 2016

The purpose of this research is to investigate the temporal and spatial relationships of activated filaments, soft X-ray production, and Ha flares. The X-ray data are from the Lockheed Mapping X-Ray Heliometer (MXRH) on 0S0-8 (Wolfson et al., 1975, 1977). This instrument has been operating continuously since July 1975. It responds to radiation from solar plasma above about 2 × 106K, provides a time resolution of 20 sec, a spatial resolution of 2-3 arc min and has a basic sensitivity roughly equivalent to the 1-8 Å full disc monitors of, e.g., the SOLRAD and SMS/GOES satellites (threshold ≈ 2 × 10-9W/m2). However, because of its spatial resolution the MXRH permits study of small X-ray events in individual active regions even when the integrated solar X-ray emission is high.
Estimates of the Magnetic Energy Densities of two Eruptive Prominences from Their Close Association with Moving Type IV Radio Bursts
Authors: Stewart R.T. , Hansen R.T. , Sheridan K.V.
Published: July 2016

During 1977 October 3-5 two eruptive-prominence and moving-type-IV radio events occurred above the east limb of the Sun when the active region McMath No. 14979 was ≈20° and ≈7° behind the east limb. No flares or microwave events were reported but long-duration soft X-ray events were recorded by OSO-8 and SMS-2 in the 1-8 Å range (Lemen, Wolfson and Grubbe, private communication).
Energy and Mass Balance in Prominences
Authors: Maltby P.
Published: July 2016

In his book “Solar Prominences” Tandberg-Hanssen (1974) reviewed several papers related to the energy balance, some of which assumed that a continuum description is valid. A sufficient condition for the application of the magneto-hydrodynamic equations is that the plasma be collision dominated. This corresponds to requiring that the mean free paths for particle collisions for all species be much smaller than the characteristic length scale for macroscopic change and that the particle collision intervals be much shorter than the characteristic time scale for macroscopic change.
Prominences and Solar Activity
Authors: Švestka Z.
Published: July 2016

The following subjects were discussed:

(1)

Filament activation

(2)

Post-flare loops.

(3)

Surges and sprays.

(4)

Coronal transients.

(5)

Disk vs. limb observations.

(6)

Solar cycle variations of prominence occurrence.

(7)

Active prominences patrol service.

Of all these items, (1) and (2) were discussed in most detail and we also pay most attention to them in this report. Items (3) and (4) did not bring anything new when compared with the earlier invited presentations given by RUST and ZIRIN and therefore, we omit them.
Chaos
Authors: Bhatnagar K.B.
Published: July 2016

This is an introductory article on Chaos giving the definition of Chaos, source and tools of Chaos, routes to chaos, measurement of chaos, chaos through resonance. The Duffing equation has been mentioned as a problem of double resonance leading to chaos and finally some problems relating to chaos in the Solar system have been described.
Algorithms for Controlling chaos: Application to BVP Oscillator
Authors: Rajeskar S.
Published: July 2016

We discuss how chaotic dynamics can be converted into regular motion in Bonhoeffer-van der Pol oscillator. Using a control signal proportional to the actual and desired outputs we study the control of fixed points and limit cycles by making time-dependent perturbations of amplitude of external force. We show the round-off induced periodicity in the digital computer simulations of orbits on chaotic attractor. We illustrate the stabilization of unstable periodic or bits by adding periodic pulses of small magnitude.
Chaotic Stellar Dynamics During Collective Interactions
Authors: Subbarao D. , Uma R.
Published: July 2016

We prove a basic result for collisionless galactic models that collective motion not only introduces Landau damping but also intrinsic chaos of typical star dynamics in the phase plane when a small perturbative wave disturbance is present. The Melnikov method is used; the consequences of the chaos and quasilinear diffusion are pointed out.
Dynamical Instability of Trapezium Type Multiple Stars
Authors: Mirzoyan L.V.
Published: July 2016

The properties of the Trapezium type multiple stars are discussed. The existing data confirm the dynamical instability of the Trapeziums. They show that because of the specific space configurations of components the Trapezium type multiple stars are disintegrated completely or partly (becoming ordinary systems with smaller number of components). The disintegration time is estimated some million years for Trapeziums with negative total energies and much shorter when their total energies are positive. There are some evidences in favour of the existence of Trapeziums possessing positive total energies.
The Effect of Multiplicity of Stellars Encounters and the Convergence of Collision Integral in the Stellar System
Authors: Petrovskaya Irina V.
Published: July 2016

The multiplicity factor of stellar encounters in the infinite homogeneous layer with the constant thickness H has been studied. It is seen that simultaneous effect of Chaotically distributed distant field stars leads to the convergence of the collision integral for the great distances in the plane disk and in the layer of the constant finite thickness.
On Gravothermal Instability of Anisotropic Self-Gravitating Gas Spheres: Singular Equilibrium Solution
Authors: Spurzem R.
Published: July 2016

A reinvestigation of the linear perturbation theory is presented, which examines the hydrostatic readjustment of an isolated self-gravitating gas sphere to a redistribution of energy. The here presented model describes a stellar system by the common equations of gas in hydrostatic equilibrium but with the effect of the anisotropic velocity distribution on the pressure gradient. We take as equilibrium models the singular isothermal solution with and without anisotropy. The total variation of the Boltzmann entropy resulting from a perturbation of the system caused by a redistribution of heat (i.e. r.m.s. kinetic energy of the stars) is calculated for anisotropic solutions to first order as well as to second order for the isotropic equilibrium. The extremized eigenfunctions which represent the entropy and anisotropy perturbation functions, are determined analytically. They exhibit gravothermal behaviour in the central region where heat is removed. It is also found that the anisotropy readjusts non-thermally in the sense that the system departs from isotropy although the total entropy increases.
Stability of the Triangular Lagrangian Solutions of the Photo Gravitational Restricted Three-Body Problem in the Three-Dimensional Case
Authors: Murtuza Md. Ghulam , Kumar Vijay , Choudhry R.K.
Published: July 2016

The stability of the triangular Lagrangian solutions for the photo-gravitational restricted three-body problem in the three-dimensional case is investigated for the case when the resonances are absent and also when the resonances are present. Stability is proved for most (in the sense of Lebesgue) initial conditions for all μ < μ0 except for the resonance cases.
Tidal Force of Sun Due to Planetary Radial Alignment and Sun-Spot Cycle
Authors: Verma S.D.
Published: July 2016

It is well known that the Sun’s radiation and a large number of phenomena occurring on the sun have influence on the Earth’s near environment i.e. Atmosphere, Ionosphere, Magnetosphere, etc. These manifest themselves as day-night, seasons, tides and many changes in the neutral atmosphere; changes in meteorological parameters. These changes are directly or indirectly related to variations in solar parameters, such as solar flares, magnetic storms, variations in sunspot number occurring in solar photosphere. Sunsports are observed, their number counted and their accurate records maintained for long time (many centuaries). The sunspot number seems to follow periodic changes with several periods; mainly 11 years and 23.5 years. Recently it has been shown that the combined tidal force of the inner planets and two largest planets, Jupiter and Saturn, have periodic change of 11 and 23.5 years. It was proposed that this small force may be having a tiny influence on the surface of the Sun and causing some nonlinear effect which results into formation of sunspots and thus causes the variations in the number of sunspots. In the present work it is shown that whenever the combined tidal force on sun increases then sunspot number seems to increase and when force decreases sunspot number decreases. This is shown for Solar Cycle number 21.
Particulate Detection in the Near Earth Space Environment Aboard the Long Duration Exposure Facility Ldef: Cosmic or Terrestrial?
Authors: McDonnell J.A.M. , Sullivan K. , Stevenson T.J. , Niblett D.H.
Published: July 2016

Examination of surfaces exposed for more than five and a half years, from detectors with unique attitude stabilisation relative to the orbital velocity vector, offers scope for examining definitively the sources of hypervelocity space particulates. Surfaces reveal discrete crater morphologies, crater size distributions and incident flux distributions. Discrete crater studies will later also reveal the chemistry of residues which can, especially via the capture cell principle, lead to elemental analysis of micron dimensioned particles.

First analyses of the flux data from the thin foil perforation experiments (MAP) involve a study of the statistics of the forward (ram) direction, the rear (trailing) direction and the space pointing direction. Modelling of the dynamics of geocentrically bound and unbound orbits yields evidence that the characteristics of the particles, and hence probably their source, change over the particle size range measured by the experiment. Smaller particles (< 1 μm diameter) have lower velocities which could include geocentrically bound particulates, whereas the larger particles (5-10 μm diameter) can be identified with “cosmic” particles of interplanetary or interstellar origin.
The Nasa Solar Probe Mission: In Situ Determination of Interplanetary Out-of-The Ecliptic and Near-Solar Dust Environments
Authors: Tsurutani Bruce T. , Randolph James E.
Published: July 2016

The NASA Solar Probe mission will be one of the most exciting dust missions ever flown and will lead to a revolutionary advance in our understanding of dust within our solar system. Solar Probe will map the dust environment from the orbit of Jupiter (5 AU), to within 4 solar radii of the sun’s center. The region between 0.3 AU and 4 Rshas never been visited before, so the 10 days that the spacecraft spends during each (of the two) orbit is purely exploratory in nature. Solar Probe will also reach heliographic latitudes as high as ~ 15 to 28 above (below) the ecliptic on its trajectory inbound (outbound) to (from) the sun. This, in addition to the ESA/NASA Ulysses mission, will help determine the out-of-the-ecliptic dust environment. A post-perihelion burn will reduce the satellite orbital period to 2.5 years about the sun. A possible extended mission would allow data reception for 2 more revolutions, mapping out a complete solar cycle. Because the near-solar dust environment is not well understood (or is controversial at best), and it is very important to have better knowledge of the dust environment to protect Solar Probe from high velocity dust hits, we urgently request the scientific community to obtain further measurements of the near-solar dust properties. One prime opportunity is the July 1991 solar eclipse.
A Cosmic Matter Accretion Event Around 660,000 Years Before Present Found in Two Dated, Central Pacific Cores
Authors: Yamakoshi Kazuo , Nogami Ken’ichi , Omori Rie , Jianguo Ma , Shulan Ma
Published: July 2016

In order to study large-scaled cosmic matter accretion events in the past, Ir enriched layers at C-T and other geological boundaries and dated sedimental cores have been searched by many scientists. In this work, Iridium contents and the ratios of (Co/Fe) in two dated, respective layers of the cores are determined. These samples were dated fortunately with the paleomagnetic and also with the cosmogenic Be-10 methods. Ir enrichments are found at (0.660 ± 0.030) My before present.
Noble Metal Enrichments in Cosmic Spherules
Authors: Nogami K. , Misawa K. , Omori R. , Jianguo M. , Yamakoshi K.
Published: July 2016

In this work, studies on relationships of chemical compositions between fusion crust and nucleus in iron spherules are reported. More than 10% of the iron spherules which were picked out from deep sea sediment, have cores and crusts. We were able to divide three of them into cores and crusts. Each cores and crusts were analyzed individually by INAA. The core mainly consists of iron and nickel. Other trace elements, especially noble metal Au and Ir were concentrated in the core. The mechanism of core formation in the iron spherules shows us the origin of them.
Spatial Distribution and Orbital Properties of Zodiacal Dust
Authors: Kneißel Bernhard , Mann Ingrid
Published: July 2016

Within the recent years the spatial distribution of Zodiacal dust has been subject to a variety of modelling approaches. Whereas models derived from observations in the visual range tend to demand for an increase of interplanetary matter above the solar poles (bulges), models based on infrared measurements and extended to small r seem to favor a decrease there (holes). The models are reviewed, and the dynamical structure implicated in the models is outlined.
The Infrared Zodiacal Light
Authors: Hanner Martha S.
Published: July 2016

Thermal emission from interplanetary dust is the main source of diffuse radiation atλ5-50 μm. Analysis of infrared sky maps from IRAS and ZIP lead to the result that the average optical properties of the dust change with heliocentric distance. The present uncertainties in calibration should be resolved by COBE. Existence of a dust sublimation zone at 4 solar radii awaits confirmation at the next solar eclipse.
Fine Resolution Brightness Distribution of the Visible Zodiacal Light
Authors: Kwon S. M. , Hong S. S. , Weinberg J. L. , Misconi N. Y.
Published: July 2016

Applying time-dependent corrections of the atmospheric diffuse light to the observed night sky brightness, we have determined brightness of the zodiacal light over the region 40° ≤λ − λ⊙ ≤;320ΰand − 20°≤β≤20ΰ. The resulting map of equal brightness contours has an angular resolution of two degrees, and exhibits east-west and north-south asymmetries.
Modeling Dust Fragmentation in Comets
Authors: Konno I. , Huebner W.F.
Published: July 2016

We developed a 1-D hydrodynamic model of dusty gas flow with dust fragmentation in a cometary atmosphere and performed calculations for a dust-size distribution with radiia =10−4— 10 cm and densities variable with dust size. A comparison was made with Giotto observations of dust jet intensities within 100 km of the nucleus of Comet Halley. We found that dust fragmentation cannot be solely responsible for the flattening of the dust intensity near the nucleus with respect to the 1/R law. We conclude that a combination of geometric effects and grain fragmentation may explain the observed intensity profiles.
The Contribution of Long Period Comets to the Interplanetary Dust Cloud
Authors: Fulle M. , Cremonese G.
Published: July 2016

The numerical analysis of cometary dust tails (Fulle 1989) allows to obtain the mass loss rate, the size distribution, the ejection velocity and the orbital eccentricity of the dust grains ejected by the parent comets. All these physical quantities are necessary and sufficient to compute the comet mass contribution to the interplanetary dust cloud. We apply this method to three long period comets, namely C∕Bennett 1970II, C∕Bradfield 1987XXIX and C∕Liller 1988V, and obtain that each long period comet injects in bound orbits at least half of the total produced mass. When we consider that a typical long period comet can produce more than 1014g of dust along each perihelion passage, we obtain that the considered long period comets alone injected a input mass rate of about 106g s−1of meteoroids in bound orbits during the last 20 years, a contribution which is very close to that from all short period comets.
Chemical Composition of an Emanation from Comets: Identification of the 3 Micron Comet Feature
Authors: Sakata A. , Wada S. , Tokunaga A.T.
Published: July 2016

Recent high resolution observations of comets revealed a detailed spectral shape of the 3.4μfeature. We measured IR spectra of simple 14 hydrocarbon molecules and made ”synthesized comet spectrum”. Peak wavelength and spectral shape of the synthesized spectrum are well in agreement with the observed comet features.
Scattering Properties of Cometary Dust Based on Polarimetric Data
Authors: Mukai Sonoyo , Mukai Tadashi , Kikuchi Sen
Published: July 2016

Referring to the dust model in Mukai and Mukai(1990), where the scattering by large rough particles and Mie scattering by small particles are taken into account, a phase function of linear polarization of several comets is examined, especially in a region of phase angles α near a maximum polarization. A lower maximum polarization observed in comet Austin(1989c1) than those in comets West(1975n) and P/Halley leads a speculation that a mixing ratio of rough scattering to Mie scattering in comet Austin increases from a sun-comet distance r of 0.6 AU to 1.2 AU. This implies that a shortage of large particles in comet Austin occured in r <1 AU.