bluuebunny/crossref_metadata_2025 huggingface dataset:
The UNAM Scanning Fabry-Perot Interferometer (PUMA) for the Study of the Interstellar Medium
Authors: Angeles F. , Bernal A. , Cobos F. , Garfias F. , Gutiérrez L. , Langarica R. , Rosado M. , Tejada C. , Tinoco S.
Published: July 2016

We describe recent advances in the development of a scanning Fabry-Perot interferometer applied to the study of the kinematics of the interstellar medium at the Observatorio Astronómico Nacional at San Pedro Mártir, B.C. México.
A Detailed Study of High Redshift Radio Galaxies
Authors: Hippelein H. , Meisenheimer K. , Neeser M.
Published: July 2016

We report on an ongoing survey of the extended line emission in high redshift radio galaxies, using a tunable Fabry-Perot etalon. Some results and suitable models are presented for individual sources.
High Resolution Studies of Molecular Hydrogen by Means of Near-Infrared Fabry-Perot Imaging
Authors: Chrysostomou Antonio , Burton Michael , Axon David , Brand Peter , Hough James , Bland-Hawthorn Joss , Geballe Tom
Published: July 2016

We present a study of the velocity profiles of the v=l-0 S(1) transition of molecular hydrogen (H2) towards the star forming region of OMC-1. A three dimensional data cube is presented which displays the spatial distribution as well as the velocity structure of the H2 emission. A brief description of the data acquisition, reduction and analysis is given.

The three dimensional aspect of the data has allowed us to re-examine the kinematic nature of the region. The results reveal a number of isolated sources which posses asymmetric velocity profiles which can be modelled by bow C-shocks. The implication is that these sources are compact knots of material which were involved in some explosive event, possibly associated with the luminous source IRc2, and are ploughing into the dense molecular disk around IRc2. It is likely that these bullets are associated with those discovered by Allen & Burton (1993).
3-Dimensional High-Resolution Solar Spectro-Polarimetry
Authors: Volkmer Reiner
Published: July 2016

In order to obtain information on the magnetic field on the sun in two spatial dimensions, a spectro-polarimeter of high spatial, spectral, and temporal resolution was built in the German Vacuum Tower Telescope (VTT) at the Observatorio del Teide/Tenerife. The two-dimensional spectrometer in the VTT, using a Universal Birefringent Filter (UBF) and a Fabry-Perot Interferometer (FPI) to obtain narrow-band nltergrams with a spectral resolution of the order of 3.105 (approx. 22 mÅ at CE5; at 6303 Å) and a spatial resolution of 0.2 arcsec/pixel (Bendlin et al. 1992, Bendlin and Volkmer 1993), was extended to work as a spectropolarimeter for measuring Stokes-I and Stokes-V profiles.
Stellar dynamics of galactic nuclei with TIGER
Authors: Emsellem Eric , Bacon Roland , Monnet Guy
Published: July 2016

We conducted an observational program using the TIGER integral field spectrograph to study the dynamical structure of nearby galactic nuclei. We already obtained new original results on three of the best ”Black Holes Candidates”: M 32, M 31 and M 104. Their nuclei exhibit complex morphologies and unusual dynamical properties such as: asymmetries, anisotropy, triaxiality which would have been impossible to detect with a ”classical“ spectrograph.
A comparison of Imaging Fourier Transform with Grating Spectrometry for Tridimensional Spectroscopy
Authors: Smith Peter L. , Thorne Anne P. , Parkinson W. H.
Published: July 2016

We compare the relative merits of four different types of instrument for tridimensional spectrometry at visible and ultraviolet wavelengths: the echelle and long-slit spectrographs and two types of Fourier transform spectrometer (conventional scanning and fixed tilt spatially heterodyned). Each of these instruments requires different spatial and spectral scanning modes. It is shown that in certain limiting conditions all four are equally efficient, but that they differ in other important characteristics.
Variable HII Regions
Authors: Hughes V.A.
Published: July 2016

Initial CO observations of the Cepheus OB cloud by Sargent (1977), identified the condensation known as Cepheus A. Other observations have shown that it has the normal empirical indications of a star forming region. In the radio continuum, using the WSRT, it consists of two thermal components (Hughes and Wou-terloot 1982). The West component is associated with the Herbig-Haro object GGD-37, and will not be considered further here. The East component when observed further with the VLA, is seen to consist of two strings of about 14 compact HII regions, and is the subject of the present paper.
A Swept-Up Molecular Bubble in L1551
Authors: Hayashi Saeko S. , Hayashi Masahiko , Kaifu Norio
Published: July 2016

The environment of the young stellar object IRS5 in L1551 dark cloud is a representative of the “protostellar disk and outflow” systems found in star forming regions. The bipolar molecular outflow there was discovered as the first of its kind a decade ago (Snell, Loren, and Plambeck 1980). Its location in the sky, that is, its proximity (160 pc), isolation, and its almost edge-on inclination have favored the observation in great detail. IRS5 is thought to have the spectral type G - K (Mundt et al. 1985) similar to the Sun, with its dominant activity in the stellar wind, and not in the UV radiation as in massive protostars. The blueshifted and redshifted outflow lobes are clearly resolved into a pair of shell structures. The successive studies, mostly in CO lines, have led to a model of the outflow in which the molecular material is accelerated at the edge of a cavity evacuated by the protostellar wind (e.g. Uchida et al. 1987, Rainey et al. 1987, Moriarty-Schieven and Snell 1988).
A Remarkable Bipolar Flow in the Center of the Rho Ophiuchi Cloud
Authors: Andre Ph. , Martin-Pintado J. , Despois D. , Montmerle T.
Published: July 2016

Using the IRAM 30-m telescope in August and December 1988, we have discovered the first molecular outflow in the central part (L1688) of the nearby ρ Ophiuchi dark cloud. This outflow, found in the J = 2 — 1 line of 12CO near the cloud core A, is an extreme case, weak (outflow mass-loss rate ≈ 5 x 10−8M⊙yr−1) and highly collimated (lenght to width ratio > 14), which explains why it has escaped previous detections with smaller telescopes. The high-velocity molecular gas is hot and optically thin, making the J = 2 — 1 line of 12CO ≈ 3-4 times stronger than the J = 1 — 0 line. Unexpectedly, this outflow does not appears to be driven by any of the embedded near-IR sources known in this region previous deep VLA surveys of the cloud (André, Montmerle, and Feigelson, 1987; Stine et al., 1988; André et al., in prep.). The outflow exciting source is thus probably a very low-luminosity ((L < 0.1L⊙) young stellar object. Using the 30-m equipped with the MPIfIR bolometer, we have very recently found (March 1989) that this object is the strongest continuum point source of L1688 at 1.3 mm. By analogy with L1551-IRS5 and HL Tau, the radio properties of this source suggest that it possesses a weak, possibly collimated, ionized wind and a relatively massive, cold circumstellar disk (Mdisk ≈0.1M⊙).
Massive Dust Disks Surrounding Herbig Ae/Be Stars
Authors: Sandell G.
Published: July 2016

I present preliminary results from a small mm/submm continuum survey, mostly photometry (1.1mm, 800µm, 450µm and 350µm), but also some mapping at 800µm of Herbig Ae/Be stars and a few peculiar stars. These observations were commenced on the 15m JCMT submillimetre telescope on Mauna Kea, Hawaii.
The Structure of Molecular Clouds from Large Scale Surveys of CO and CS
Authors: Bally John
Published: July 2016

The molecular gas lying in the interior of the Orion superbubble consists of sheets, filaments and bubbles in which the dense active star forming cloud cores are embedded. Many regions have a wind-swept or cometary appearance suggesting strong interaction with the Orion OB association. External heating dominates the cloud energy budget, resulting in cold (˜10K) cloud cores surrounded by hot (>20K) envelopes. Non-ionizing UV radiation emitted by late B and A stars may be the source of the kinetic energy needed to form some of the large scale cavities and contributes to the supersonic line widths seen in many clouds.
Distance and Chemical Composition of High-Velocity Clouds
Authors: van Woerden Hugo , Schwarz Ulrich J. , Wakker Bart P.
Published: July 2016

This contribution reports results of recent absorption-line studies on La Palma and reviews earlier work done elsewhere. CaII has been found in absorption in five HVCs, mostly against extragalactic background sources. The CaII/HI ratios differ strongly, from 0.002 to 0.1 times solar, suggesting different origins of HVCs. Nondetections of CaII absorption in stellar spectra may provide lower limits to HVC distances, or be caused by small-scale structure or a low CaII/HI ratio in the HVC. Proper interpretation requires comparison of CaII/HI ratios in stellar and extragalactic probes, and use of high-resolution HI maps. No solid direct distance determinations of HVCs are available yet. The distance of Complex C is controversial.
Irradiance Variations of Stars
Authors: Lockwood G. Wesley
Published: July 2016

Using a nine-year time series of photometric observations of 33 stars similar in temperature and mass to the Sun, but covering a wide range of age and mean chromospheric activity, we found that a majority varies from year to year, some by as much as several percent. We describe the methodology, circumstances of the observations, and photometric results. Stars most similar in mean chromospheric activity to the Sun varied by amounts several times greater than the Sun over a comparable time interval. Thus, the Sun’s present low level of variability, as measured from 1980 to 1989 by the Solar Maximum Mission, appears unusual.
Solar Absolute Reference Spectrum
Authors: Neckel Heinz
Published: July 2016

Requirements and problems in establishing an absolute solar spectrum, which could serve equally well all concerned sciences (e.g. solar physics, atmospheric physics, astrophysics) as a qualified reference, are illustrated by means of a high resolution spectral atlas with absolute intensity and irradiance scales. Also the organizational aspects are pointed out: the desire for one worldwide reference spectrum involves its recommendation by a competent team of scientists and the agreement of the relevant, official organizations.
Summary of Future Space Observations of Solar Irradiances at Different Wavelengths
Authors: Domingo Vicente
Published: July 2016

The variations of solar irradiance can only be measured with a reasonable precision from space for almost all wavelengths. Yet the history of solar irradiance determinations is, with few exceptions, the history of efforts to patch the infrequent or too discontinuous space-based measurements by devising mechanisms for proxy determination of solar irradiance fluxes from ground-based obtained parameters. Although it appears that in the near future the situation will not be too different, there is some increase in the coverage of the spectral range that will be monitored. From gamma-rays to infrared light there are instruments that are now operating (e.g. GOES, Yohkoh, UARS) or are planned to operate in approved space missions (e.g. SOHO, ATLAS), or form part of proposed, not yet approved, missions. New techniques are being developed specifically for the measurement of solar irradiance variations with increased precision (e.g. cryogenic radiometer) in the next generation of space-borne measurements.
Observations of Global Solar Magnetic and Velocity Fields
Authors: Hoeksema J. Todd
Published: July 2016

The Sun’s magnetic field varies on time scales of minutes, months, decades, and centuries. These changes drive variations in solar irradiance. Characteristics of the changing magnetic field reveal, at some level, how the solar cycle works. The basic 22-year magnetic cycle and corresponding 11-year activity cycle of the Sun are driven by the emergence of active regions. The frequencies of solar oscillations that probe the convection zone vaxy on the same time scale. While plausible explanations for the statistical properties of solar activity can be made, the details of flux emergence cannot be predicted. Global activity varies on other intermediate time scales as well.

Defining elements of a cycle as those sharing a common bipolar field orientation, the first signs of a cycle can appear at high latitudes up to 5 years before solar minimum and the final elements disappear at the equator several years after the following minimum - a span as long as 18 years. At a particular latitude waves of activity are spaced by 11 years. The torsional oscillation in solar rotation rate has similar characteristics.

The spatial distributions of total flux and large-scale polarity evolve quite differently: the total flux map resembles the butterfly diagram, moving from mid latitudes toward the equator during the cycle, while the net zonal flux has two maxima in each hemisphere that expand away from mid latitudes.

While each solar cycle shares these basic features, fixed by the action of the solar dynamo working within the convection zone, the details of each cycle are determined by the apparently random timing and placement of emerging flux and by the changing convective flow patterns.
General Structure of the X-ray Corona
Authors: Acton L. W.
Published: July 2016

X-ray images have revealed the corona to comprise four basic morphologies. In order of X-ray luminosity these structures are: (1) Bright, relatively short, X-ray loops in active regions, (2) Less bright and larger X-ray structures of the so-called quiet corona, (3) X-ray bright points, and (4) Coronal holes. The soft X-ray telescope (SXT) onYohkohprovides good angular resolution with much improved time resolution and continuity of coverage as compared to the earlier observations. In the SXT movies these structures often appear to be interacting and change appearance on time scales from seconds to weeks. Flare, flare-like, and eruptive processes continuously alter the general structure of the corona. This paper will comment on the structure, changes and heating of the X-ray corona as revealed by theYohkohobservations.
The Mass Ejection Event of 1986 May 4 and the Associated Phenomena
Authors: Garczyńska I. N. , Rompolt B. , Aurass H. , Burkepile J. T. , Cader-Sroka B. , Chertok I. M.
Published: July 2016

A sequence of structural changes in the low and high corona observed in Hαand white light is investigated in details. Relatively slow Hαmass ejections have been accompanied by X-ray and radio bursts as well as CME. Some interconnections between all these events are analysed.
Very Large Array Observations of Large-Scale Coronal Structures
Authors: Lang K. R.
Published: July 2016

Very Large Array (VLA) observations indicate that electrons accelerated in one active region can travel along otherwise-invisible, large-scale coronal loops to trigger flares in another widely-separated active region, as well as from the magnetic loops connecting them. The VLA provides high-resolution, full-disk images of quiescent, or non-flaring, coronal loops within individual active regions (at 20 cm) and between or beyond them (at 90 cm). Both ground-based radio telescopes and spaceborne X-ray telescopes provide high-resolution images of the ubiquitous coronal loops whose hot, dense magnetically-trapped plasma emits thermal bremsstrahlung. Radio observations can be used to specify the strength and structure of the magnetic fields in the low solar corona. We find a high magnetic field strength in the million-degree plasma above large sunspots – 75 to 80 percent of the value in the underlying photospheric sunspots; as well as coronal regions of non-potential, current-amplified magnetic fields. Some long-lasting (hours) coronal radio sources found on the Sun and other active stars require nonthermal radiation and nearly continuous acceleration of energetic electrons.
Solar Corona Investigation by the Coronal Line Photometer at Lomnický Peak
Authors: Minarovjech M. , Rybanský M.
Published: July 2016

This paper deals with a possibility to use the ground-based method of observation in order to solve basic problems connected with the solar corona research. Namely:

1.

heating of the solar corona

2.

course of the global cycle in the corona

3.

rotation of the solar corona and development of active regions.

There is stressed a possibility of high-time resolution of the coronal line photometer at Lomnický Peak coronal station, and use of the latter to obtain crucial observations.
Theoretical Correlations Between Various Prominence Parameters
Authors: Heinzel P. , Gouttebroze P. , Vial J.-C.
Published: July 2016

Starting from our extensive numerical modeling of the NLTE conditions in solar prominences, we present here some examples of important correlations between the prominence plasma parameters and radiation properties. For example, the plasma emission measure was found to be closely related to the integrated Hα line intensity which provides a new diagnostic tool for determination of plasma densities.
The Diamagnetic Effect: Misconception about Its Vanishing Average
Authors: Steinitz R.
Published: July 2016

It has been argued in the past that while the diamagnetic effect (DME) is well apparent for single particles (i.e. motion of charged particles in the Earth’s ionosphere), it is not relevant for fluid descriptions of plamas.

In this paper we show that this is a misconception due to a wrong averaging procedure. Taking the DME into account, we obtain speed filters which function as heat and momentum pumps, resulting in cool sunspots, a hot corona and solar winds.
MHD Spectrum of Coronal Rays
Authors: Matsuura O. T. , Shigueoka H. , Azevedo C. A. , Lavras W. O.
Published: July 2016

The MHD spectrum of discrete kink modes is derived for a cylindrical, static and isothermal plasma with spatial variations in radial direction only. Such a configuration models, in first approximation, the long and almost radially oriented fine structures of the solar corona denominatedcoronal rays, whenever cylindrical symmetry holds. Since here gravity is not taken into account, the application of the results is limited to longitudinal wavelengths not greater than the density scale of height. The predicted eigenfrequencies of slow magnetoacoustic modes are potentially observable in eclipses and may constitute a diagnostics of the axial electric current and the degree of twisting of the magnetic field.
On the Optical Polarization of the White-Light Coronal Structures
Authors: Filippov B. P. , Molodensky M. M. , Koutchmy S.
Published: July 2016

A special experiment was designed to measure the orientation of the polarization plane in the solar corona during the total eclipse of July 11, 1991. Rotating polaroids with the axes directed at +45° and at −45° of the radial direction in all directions were used. The polarization plane was found to be tangential to the solar limb everywhere with an accuracy within 1°, in agreement with the Thomson scattering theory.
Gravitational Collapse versus Thermonuclear Explosion of Degenerate Stellar Cores
Authors: Isern J. , Canal R.
Published: July 2016

In this paper we review the behavior of growing stellar degenerate cores. It is shown that ONeMg white dwarfs and cold CO white dwarfs can collapse to form a neutron star. This collapse is completely silent since the total amount of radioactive elements that are expelled is very small and a burst of γ-rays is never produced. In the case of an explosion (always carbonoxygen cores), the outcome fits quite well the observed properties of Type Ia supernovae. Nevertheless, the light curves and the velocities measured at maximum are very homogeneous and the diversity introduced by igniting at different densities is not enough to account for the most extreme cases observed. It is also shown that a promising way out of this problem could be the He-induced detonation of white dwarfs with different masses. Finally, we outline that the location of the border line which separetes explosion from collapse strongly depends on the input physics adopted.
Neutron Star Crusts With Magnetic Fields
Authors: Yakovlev D.G. , Kaminker A.D.
Published: July 2016

The properties of plasma in neutron star crusts with strong magnetic fields B = 1010 − 1013 G are reviewed: thermodynamic properties (equation of state, entropy, specific heat), transport properties (electron thermal and electrical conductivity of degenerate electron gas, radiative thermal conductivity of very surface nondegenerate layers) and neutrino energy losses. Classical effects of electron Larmor rotation in a magnetic field are considered as well as quantum effects of the electron motion (Landau levels). The influence of the magnetic fields on density and temperature profiles in the surface layers of neutron stars and on neutron star cooling is briefly discussed.
The Equation of State of Fluid Hydrogen at High Density
Authors: Chabrier G.
Published: July 2016

We present a free energy model for fluid hydrogen at high-density and high-temperature. This model aims at describing pressure dissociation and ionization, which occur in partially ionized plasmas encountered in the interiors of giant planets and low-mass stars. The model describes an interacting mixture of H2, H, H+ and e− in chemical equilibrium. The concentrations of H2+ and H− ions are found to be negligible for equation of state purposes. Our model relies on the so-called chemical picture approach, based on the factorization of the partition function into translational, internal and configurational degrees of freedom. The present model is found to be unstable in the pressure-ionization regime and predicts the existence of a first-order plasma phase transition (PPT) which ends up at a critical point given by Tc = 15300 K, Pc = 0.614 Mbar, and ρc = 0.35 gem−3. The transition occurs between a weakly ionized phase and a partially ionized (~ 50%) phase.
White Dwarf Seismology: Influence of the Constitutive Physics on the Period Spectra
Authors: Fontaine G. , Brassard P.
Published: July 2016

We present the results of numerical experiments aimed at demonstrating how theg-mode period spectra of pulsating DA white dwarfs depend on the various components of the input physics. We take advantage of recent developments on many fronts of physics (equation of state, opacity, convection) to compare the theoretical pulsation periods of models with different pieces of the constitutive physics, but with otherwise fixed values of their stellar parameters. This exercise is necessary to assess the reliability of the pulsation analyses of white dwarfs which have started to come out.
Helioseismology: the Sun as a Strongly-Constrained, Weakly-Coupled Plasma
Authors: Däppen W.
Published: July 2016

Accurate measurements of observed frequencies of solar oscillations are providing a wealth of data on the properties of the solar interior. The frequencies depend on the solar structure, and on the properties of the plasma in the Sun. Except in the very outer layers, the stratification of the convection zone is almost adiabatic. There, the sound-speed profile is governed principally by the specific entropy, the (homogenous) chemical composition and the equation of state. It is therefore essentially independent of the uncertainties in the radiative opacities. The sensitivity of the observed frequencies is such that it enables to distinguish rather subtle features of the equation of state. An example is the signature of the heavy elements in the equation of state. This opens the possibility to use the Sun as a laboratory for thermodynamic properties.
Coulomb Corrections in The Nuclear Statistical Equilibrium Regime
Authors: García D. , Bravo E.
Published: July 2016

The ionic contribution to the Equation of State (EOS) of a multicomponent plasma of nuclei in the nuclear statistical equilibrium regime is studied, and a method to compute the coulombic corrections within the framework of the linear mixing hyphothesis is proposed. Some consequences of including these corrections in the EOS are briefly analysed in relation with two concrete astrophysical scenarios, the Supernovae Ia explosion and the Accretion Induced Collapse of a massive white dwarf.
Plans for the Naval Observatory of Buenos Aires
Authors: Marpegán J.
Published: July 2016

The Naval Observatory of Buenos Aires was founded In 1860 as a marine observatory to satisfy the needs of nautical and geodetic astronomy in the aid of marine navigation and hydrography. It has provided the official – national time for 50 years.

The Observatory carries out computations for the Argentine Nautical Almanac and provides an abridged ephemeris for hydrographic and – topographic work. Since 1955 it has provided standard frequency and time on – the frequencies 5, 10, and 15 MHz through Its transmitting station LOL. During the last two years specific plans were developed for modernizing and – improving the precision of this service. Some of these plans have already been carried out.
The Variation of the Mean Latitude of the Hamburg PZT
Authors: Enslin H.
Published: July 2016

The Orlov mean latitudes of the Hamburg PZT show a rather regular increasing trend which cannot be attributed to the motion of the mean pole. A check with mean latitudes from FK4 stars of the PZT program proves that the drift can hardly be a reproduction of errors in proper motions.
Structure of Close Binaries. I: Polytropes
Authors: Naylor M. D. T. , Anand S. P. S.
Published: July 2016

An extension of the method devised by Monaghan and Roxburgh (1965) for rapidly rotating polytropes is used to study the structure of the primary component of a synchronous close binary system. Results are presented for polytropes of index 1.5, 2.0, 3.0, 4.0 and 4.9. We conclude that the extended Monaghan and Roxburgh method can be applied to real stars which are perturbed by both tidal and rotational forces.
Discovery and Measurement of Double Stars by Lunar Occultations
Authors: Nather R. Edward , Evans David S.
Published: July 2016

When a star is occulted by the dark limb of the Moon its apparent intensity drops to zero very quickly. MacMahon (1909) proposed that the time of disappearance would measure the diameter of the star, but Eddington (1909) demonstrated that diffraction effects at the lunar limb would lengthen the apparent time of disappearance to about 20 msec, and suggested that these effects would greatly limit the usefulness of the technique. MacMahon’s paper indicates that he was aware that stellar duplicity could be detected from occultation observations, but he did not amplify the point and Eddington did not comment on it. While it has been demonstrated theoretically by Williams (1939) and experimentally by Whitford (1939) and others that stellar diameters of a few arcmsec can be measured by this technique, its use for the discovery and measurement of double stars has been only incidental to other programs (O’Keefe and Anderson, 1952; Evanset al., 1954). Properly exploited, the method can contribute materially to the study of double stars.
Transient Phenomena on the Moon
Authors: Moore Patrick
Published: July 2016

The occurrence of short-lived, localized colour phenomena on the Moon has long been supported by amateur observers, but it is only in comparatively recent times that there has been satisfactory confirmatory evidence. In view of the recent results from the seismometer left on the Moon by Apollo 12, it seems appropriate to give a summary of the present situation with regard to these transient lunar phenomena now known generally as T.L.P.s.
On the Correction to Precession from Proper Motions Referred to Galaxies
Authors: Vasilevskis S. , Klemola A. R.
Published: July 2016

One of the principal aims of the Lick proper motion program, as conceived and initiated by Wright (1950), was to derive the correction to precession. Ideally, proper motions of stars from a fundamental catalogue should be measured with respect to galaxies. Unfortunately, these stars are too bright for a direct reference to faint galaxies, even with an objective grating and two systems of exposures (2 h and 1 min) on every plate, as employed at Lick. For this reason a cooperative project with the U.S. Naval Observatory was initiated in 1953 (Scott, 1954; Vasilevskis, 1954), with an intention to establish a direct relationship between meridian circle and Lick observations. When Heckmann (1954) proposed the formation of the AGK3, it was agreed to discontinue the cooperation mentioned, so as to make the resources of the U.S. Naval Observatory available for observing the AGK3 reference stars, and then to use the AGK3 as an intermediary for relating the Lick proper motions to a fundamental system. An obvious advantage of this change was offered by the abundance of AGK stars for measurement on Lick plates; a disadvantage is the absence of the AGK3 data south of declination –2.°5.
The Use of Integrals in Numerical Integrations of theN-Body Problem
Authors: Nacozy Paul E.
Published: July 2016

The numerical integration of systems of differential equations that possess integrals is often approached by using the integrals to reduce the number of degrees of freedom or by using the integrals as a partial check on the resulting solution, retaining the original number of degrees of freedom.

Another use of the integrals is presented here. If the integrals have not been used to reduce the system, the solution of a numerical integration may be constrained to remain on the integral surfaces by a method that applies corrections to the solution at each integration step. The corrections are determined by using linearized forms of the integrals in a least-squares procedure.

The results of an application of the method to numerical integrations of a gravitational system of 25-bodies are given. It is shown that by using the method to satisfy exactly the integrals of energy, angular momentum, and center of mass, a solution is obtained that is more accurate while using less time of calculation than if the integrals are not satisfied exactly. The relative accuracy is ascertained by forward and backward integrations of both the corrected and uncorrected solutions and by comparison with more accurate integrations using reduced step-sizes.
Dynamics of Plane Stellar Systems
Authors: Hohl Frank
Published: July 2016

The evolution of initially balanced rotating disks of stars is investigated with a computer model for isolated disks of stars. An isolated, initially cold balanced disk is found to be violently unstable. Adding a sufficient amount of velocity dispersion will stabilize all small-scale disturbances. However, the disks are still unstable against slowly growing long wave-length modes and after about two rotations most disks tend to assume a bar-shaped structure. It is found that the final mass distribution over most of the disk can be closely approximated by an exponential variation, irrespective of the initial mass distribution. The gravitational two-stream instability is investigated by means of a modified computer model for infinite doubly periodic stellar systems.
The Monte Carlo Method
Authors: Hénon M.
Published: July 2016

We give here a detailed technical description of a Monte Carlo scheme for the dynamical evolution of spherical stellar systems. The philosophy of the method, as well as a few illustrative results, are given elsewhere (Hénon, 1971, hereafter called I).
High Resolution Magnetic Field Measurements in the Sunspot Photosphere
Authors: Hofmann Axel , Schmidt Wolfgang , Balthasar Horst , Tarbell Theodore T. , Frank Zoe A.
Published: July 2016

We analysed calibrated Stokes V magnetograms and simultaneously measured Stokes I spectra of high spatial and spectral resolution taken in a medium sized sunspot. We found a clear (anti-) correlation between the brightness variation of penumbral structures and the longitudinal component (B*cosγ) of the magnetic field. No azimuthal variation of the amount of the magnetic field strength (B) was observed across dark and bright structures. There the field is more vertical in bright filaments compared to dark ones.
Coherence Analysis of Photospheric Line Parameters in Active and Non-Active Solar Regions
Authors: Hanslmeier Arnold , Mattig Wolfgang , Nesis Anastasios
Published: July 2016

Examples of coherence functions between continuum intensity and line center velocity fluctuations are discussed for non active and active regions. It seems that the magnetic field leads to a different phase shift between intensity and velocity fluctuations than for non active regions.
Magnetohydrodynamic Simulation of the Evolution of Bipolar Magnetic Regions
Authors: Wu S. T. , Yin C. L. , Mcintosh P. , Hildner E.
Published: July 2016

It has been recognized that the magnetic flux observed on the solar surface appears first in low latitudes, and then this flux is gradually dispersed by super granular convective motions and meridional circulation. Theoretically, the magnetic flux transport could be explained by the interactions between magnetic fields and plasma flows on the solar surface through the theory of magnetohydrodynamics.

To understand this physical scenario, a quasi-three-dimensional, time-dependent, MHD model with differential rotation, meridional flow and effective diffusion as well as cyclonic turbulence effects is developed. Numerical experiments are presented for the study of Bipolar Magnetic Regions (BMRs). When the MHD effects are ignored, our model produced the classical results (Leighton, Astrophys. J., 146, 1547, 1964). The full model’s numerical results demonstrate that the interaction between magnetic fields and plasma flow (i.e., MHD effects), observed together with differential rotation and meridional flow, gives rise to the observed complexity of the evolution of BMRs.
Formation of Solar Prominences with Normal and Inverse Polarities
Authors: Choe G. S. , Lee L. C.
Published: July 2016

Numerical simulations of solar prominence formation are presented employing photospheric horizontal motions as boundary conditions. Three different combinations of magnetic field configurations and footpoint motions are considered: (1) a bipolar arcade with a footpoint shear, (2) an arcade exposed to a shearing and converging motion, (3) two adjacent arcades undergoing a shearing and converging motion. In each case, it is found that the dynamic evolution of magnetic fields can force the plasma into a thermal instability leading to the formation of a prominence.
THEMIS Telescope: Prospects in High Resolution Magnetic Field Observations
Authors: Rayrole J. , Mein P.
Published: July 2016

The THEMIS telescope will provide high resolution observations of the solar vector magnetic field. We present some capabilities of this instrument, concerning the polarization analysis, the correlation tracker and the two spectrographs. THEMIS is expected to come into operation in 1995–1996.
A Method on Measurements of Solar Velocity Fields
Authors: Gu Xiao-Ma , Lin Jun , Li Ke-Jun
Published: July 2016

A new method of ‘multi-cloud model’(MCM) is proposed and two application examples are given in the paper.
Measurements of Solar Magnetic Fields Using Radio Observations with the RATAN-600
Authors: Gelfreikh G. B. , Bogod V.M. , Abramov-Maximov V. E. , Tsvetkov S.V.
Published: July 2016

Three ways of measuring magnetic fields in the corona and chromosphere have been developed based on spectral polarization observations with high spatial resolution using the radio telescope RATAN-600. The methods rely on effects from the theory of the generation and propagation of microwaves in the solar atmosphere: thermal bremsstrahlung, thermal cyclotron emission, and inversion of the polarization sign in quasi-transverse field regions. The new radio spectrograph (PAS) at the RATAN-600 resulted in higher accuracy measurements of the strength and structure of coronal magnetic fields. Using observations made with the PAS on 1992 January 10, we show that the magnetic field strength in the lower corona above all large sunspots can be measured with an accuracy ≈ 3%. The correlation with photospheric magnetic fields is good, ‘radio’ magnetic fields being weaker by ≈ 20%.
Magnetic Tube Scale and Electron Acceleration from the Fine Structure of Microwave Bursts
Authors: Guang-Li Huang
Published: July 2016

A typical microwave burst with fine structures (type Hand) observed by the Dwingloo multi-channel spectrometer is proposed as evidence of a magnetic tube with a small scale and acceleration of electron beams with a short time scale at the source. It is predicted from the observations and theory that the average velocity of non-thermal electrons is about 0.1c and the density of the beam is about 104 cm−3. There is a micro-magnetic tube with a scale length of six hundred kilometers at the microwave source. There is also a quasi-periodic (~ 20 ms) evolution of the beam energy, which may be accelerated by tearing modes. The spectrum of the burst can be explained by the non-uniformity of the magnetic field. The evolution of the spectrum during a single pulse may result from the electron cyclotron maser instability. Hence, information from the fine structure of the spectrum of solar radio bursts is very important for understanding the mechanism of solar flares.
Evidence for Reality of Rapid Solar Radio Fluctuation
Authors: Qijun Fu , Chumin Hu , Bing Zhao , Shenzhen Jin , Yurovsky Yu. , Stepanov A. , Magun A. , Schanda E.
Published: July 2016

Since fast fine structures (FFS) superimposed on microwave bursts were found with high time resolution observations, they have been observed in extensive frequency range (Slottje 1978; Fu, et al. 1986; Stähli and Magun 1986; and Stepanov and Yurovsky 1991), and these results make understanding of the emission deepening. But, at the same time, the puzzling problem, these phenomena originate from sun or are only artificial, is often concerned and disputed (Benz and Fürst 1987). As it was pointed out by Benz and Fürst (1987), “the only really reliable way to study solar microwave fluctuation is to use two or more widely separated radio telescopes”.

In this paper, some of FFS events superimposed on microwave bursts simultaneously obtained at Beijing Astronomical Observatory (BAO), Crimea Astrophysical Observatory (CAO) and Institute of Applied Physics, University of Bern (IAP), are presented at first time. It is a conclusive evidence of rapid radio fluctuation originating from sun and associated with flare appearance.
Structural and Evolutionary Features of Flare-Producing Active Regions During 1988-1990
Authors: Golovko A. A.
Published: July 2016

During the period of high solar activity (1988-1990) the Sayan and Baikal Observatories of the ISTP carried out observations of the chromosphere in the H-alpha line, the photosphere and of sunspot magnetic fields; at the Siberian Solar Radio Telescope, solar radio emission observations at 5.2 cm wavelength were made. Using those observations a study is made of the evolution of “centers of magnetic activity” (Bumba, 1986) in nine active regions with different flare productivity, for which the most complete observations were available. In three cases (NOAA Nos. 5229, 5643 and 5669) they were the targets of the cooperative international Max’91 program.
Study of Calcium-K Network Evolution from Antarctica
Authors: Singh Jagdev
Published: July 2016

To study the evolution and decay of large convective cells known as supergranules, a solar telescope was set up at Maitri, Indian permanent station in Antarctica region during the local summer months (December 1989 through March 1990). A continuous sequence of calcium-K-line filtergrams for 106 hours with an interval of about 10 minute was obtained. The analysis of this data indicates that most probable life time of the calcium K network is about 20 hours. The life time depends upon the size of the cell and is larger for bigger cells. The data also show that cells (of given size) associated with remanent magnetic field regions live longer than those in the region free from magnetic field regions.
Rotation Rate of Active Nests on the Sun
Authors: Van Driel-Gesztelyi Lidia , Van Der Zalm ED B.J. , Zwaan Cornelis
Published: July 2016

We analyse Greenwich sunpot group position data for one solar cycle (1952-1963) in order to study the rotation rate of clusters of sunspot groups, so-called active nests. We find that the latitude-dependent rotation rate of nests shows an intrinsic spread. This spread appears to be caused by extensive and dense clusters of sunspot nests (superclusters or nested nests), and by very compact single nests of short duration. The ‘best’ rotation rate is defined as the rate at which the highest number of sunspot groups appear to form nests. This latitude-dependent best rotation is close to the rotation rate of individual recurrent sunspots, although nests seem to rotate slightly more rigidly than sunspot groups.
Dynamical Effects in Solar Photospheric Flux Tubes
Authors: Hasan S.S.
Published: July 2016

The interaction of an intense flux tube, extending vertically through the photosphere, with p-modes in the ambient medium is modelled by solving the time dependent MHD equations in the thin flux tube approximation. It is found that a resonant interaction can occur, which leads to the excitation of flux tube oscillations with large amplitudes. The resonance is not as sharp as in the case of an unstratified atmosphere, but is broadened by a factor proportional to H−2, where H is the local pressure scale height. In addition, the inclusion of radiative transport leads to a decrease in the amplitude of the oscillations, but does not qualitatively change the nature of the interaction.
Seven Samples of SBS Galaxies in Selected Fields
Authors: Hakopian S. A. , Balayan S. K.
Published: July 2016

The results of follow-up spectroscopy completed for seven samples of SBS galaxies in selected fields are briefly presented.
Search for Obscured IRAS Galaxies
Authors: Mickaelian A.M. , Hakopian S.A. , Balayan S.K.
Published: July 2016

We have discovered a number of sources still remaining in the IRAS catalogs with no convincing optical identification. Their IR colors and high galactic latitudes indicate faint galaxies (fainter the DSS limit). These empty fields have been observed with the Byurakan Obs. 2.6m telescope in VRI. 22m–23m faint formations have been revealed.
Optical Identification of Weak and Compact Radio Sources
Authors: Artyukh V. S. , Hovhannisyan M. A. , Mahtesyan A. P. , Movsesyan V. H.
Published: July 2016

A sample of 289 compact radio sources selected from the 7C Catalogue, covering an area of 0.097 steradian, was surveyed at 102 Mhz by the scintillation method. The observations show that the sizes of these sources are less than 0.1” and their flux densities do not exceed 2 Yn. These sources are identified with objects from the FIRST catalogue of radio sources. 99 of these objects have scintillations and have no neighbor in the surrounding 5’. 34 of those 99 are identified with objects on the POSS within 10”×10” areas. 17 of the last 34 are closer to identified POSS objects (within 2”×2” areas). So we suppose that these 17 radio sources are clearly identified with optical sources. Most of them are probably bright quasars. The other 17 will not be discussed here, as we didn’t succeed in their optical identification. There are no POSS objects brighter than 21m in the close surroundings of the remaining 65 radio sources. We have started optical observations of areas close to those 65 objects with the 2.6-m telescope of the Byurakan observatory. Up to now 15 areas were observed. In 5 cases optical objects were found fainter than 22m — 24m within 3” of the compact radio sources (one example is shown in Fig. 1). We are sure that there are no optical objects brihgter than 25m that may be identified with the remaining 10 objects. Those five identifications give us an opportunity to suppose that they are remote quasars. More powerful telescopes than the 2.6-m are needed to perform photometric and spectral observations of similar objects in order to prove our suggestion.
5-GHz VLBI Imaging Observations of 7 Equatorial AGNs
Authors: Shen Z.-Q. , Jiang D. R. , Chen Y.J. , T.-S. Wan
Published: July 2016

Since 1992 we have been conducting a 5-GHz VLBI imaging survey of southern and equatorial radio sources. So far, we have published the results of two observing sessions with 26 southern radio sources imaged in total (Shen et al. 1997; 1998). In this paper, we present the preliminary results of the third session of observations of 7 equatorial sources in the sample.
IRAS F02044+0957: A Radio Source in an Interacting System of Galaxies
Authors: Verkhodanov O. V. , Chavushyan V. H. , Mújica R. , Valdés J. R. , Trushkin S. A.
Published: July 2016

The steep spectrum of IRAS F02044+0957 was obtained with the RATAN-600 radio telescope at four frequencies. Optical spectroscopy of the system components was carried out with the 2.1m telescope of the Guillermo Haro Observatory. The observational data allow us to conclude that this object is a pair of interacting galaxies, a LINER and an H II galaxy, at z = 0.093.
New Statistical Methods for Analysis of Large Surveys: Distributions and Correlations
Authors: Petrosian Vahé
Published: July 2016

The aim of this paper is to describe new statistical methods for determination of the correlations among and distributions of physical parameters from a multivariate data with general and arbitrary truncations and selection biases. These methods, developed in collaboration with B. Efron of Department of Statistics at Stanford, can be used for analysis of combined data from many surveys with different and varied observational selection criteria. For clarity I will use the luminosity function of AGNs and its evolution to demonstrate the methods. I will first describe the general features of data truncation and present a brief review of past methods of analysis. Then I will describe the new methods and results from simulations testing their accuracy. Finally I will present the results from application of the methods to a sample of quasars.
Digitization of the FBS: Its Future Use and Expected Results
Authors: Mickaelian Areg M.
Published: July 2016

The First Byurakan Survey (FBS) is the largest spectral survey in the Northern sky. Its plates contain low-dispersion spectra for some 20,000,000 objects. The FBS spectra allow selection of objects by their color, broad emission or absorption lines, or SED; to discover, classify and investigate them. The FBS was conducted originally to search for UVX galaxies (1500 Markarian galaxies were discovered). Selection of blue stellar objects, red stars, and identification of IRAS sources have also been done by means of the FBS spectra. All these projects have been carried out by visual inspection of the plates. Digitization will give new possibilities to search for many new objects: new bright QSOs (m<18m), new Markarian (UVX) galaxies, BCDGs, optical counterparts of IR, radio, X-ray and other sources, late-type stars, planetary nebulae, emission-line stars, and white dwarfs; and to study star clusters and clusters of galaxies. The digitized FBS will be available via the Internet and on CDs. Software and an appropriate interface for working with the data will be provided.
Asteroidal recovering in the DENIS survey. A contribution of near-infrared for classifications
Authors: Baudrand A. , Bee- Borsenberger A. , Borsenberger J. , Barucci A.
Published: July 2016

The Deep European Near-Infrared southern sky Survey (DENIS) has been observing the sky since december of 1995, in the three bands I, J, K of the near-infrared, in order to provide to the community a deep and extensive photometric catalogue of stars and galaxies. In addition, the asteroids will be included in the catalogue as any other regular point sources. Therefore, in the frame of asteroidal taxonomies, this project appeared as a good opportunity to enlarge the asteroid colorimetry data base to new colours and more objects. In order to use the DENIS data for our case, we had, as a first step, to determine all the asteroids observed during the survey to recover them in the catalogue of magnitudes. We present here our recovery procedure and our final expectations. The ultimate aim of this study will be to improve our knowledge on the compositional structure of the asteroidal population.