bluuebunny/crossref_metadata_2025 huggingface dataset:
The RATAN-600 - VLA − 6m Russian telescope: Early Universe Project
Authors: Parijskij Y.N. , Soboleva N.S. , Goss W.M. , Kopylov A.I. , Verkhodanov O.V. , Temirova A.V. , Zhelenkova O.P.
Published: July 2016

We present the preliminary results of the “BIG TRIO” project of penetration into the “Dark Age” of the Universe, between the recombination epoch and the epoch of the first QSO using RATAN-600 “Cold Experiment” deep (few mJy) multi-frequency strip survey (Parijskij, Korolkov, 1986; Parijskij et.al,1991,1992). Our general approach is close to the classical SS FRII RG selection rules of very distant galaxies with old stellar population (McCarthy, 1993) with small improvements. Details may be found in (Kopylov et al, 1995). Mean estimated z of our SS FRII RG's is about 1.5, 20% of all objects have z larger than 3. Before the direct spectroscopy of all SS FRII objects we have estimated their redshifts by different methods: using the updated Hubble diagram, θ-z and flux density-z relations and now begun to use multi-color measuring all our objects to estimate “color z” and a stellar age of the parent galaxies using available models of stellar population evolution in such objects (gE class). The first subgroup of 16 objects (not the weakest ones) measured in BVRI gave us the following preliminary results using Bruzual-Charlot model (Bruzual et al., 1993). Looking at this Table, we can make the following statements: mean color z occurred to be very close (within 15%) to the photometric z, but individual redshifts may differ. A mean age of the stellar population is about 1 Gyr, and, at least in some objects, star formation began when the Universe was only 1 Gyr old (Ω0 = 1, H0 = 50), that is older than the most distant QSOs. One object, RC0934+0505, happened to be the oldest object found up to now. We estimate, that there are about 10000 objects with such an age on the sky which can be easily selected (especially with new generation of radio and optical catalogs now in preparation) and fully studied spectroscopically even by present day facilities. The only evolution effect we have noticed is that more distant objects have smaller ages of stellar populations. There is weak z-dependence of the ratio of radio to optical luminosities in the objects of our list, which disappears when we take into account the K- correction to the SED in gE.
Eclipse mapping at X-ray wavelengths
Authors: Schmitt J.H.M.M.
Published: July 2016

Stellar coronae cannot be spatially resolved, and yet stellar coronae are likely to exhibit a similar amount of structure as the solar corona. Currently, the only way to infer structure from spatially unresolved data is to look for rotational modulation of the X-ray emission or eclipses in the case of binary systems. I will discuss some of the observations obtained and critically review the methods used to infer structure from these data. Particular emphasis will be placed on the ill-conditioned nature of the inversion problem, that makes it next to impossible to infer the possibly three-dimensional structure of stellar coronae.
O and B-star surface mapping
Authors: Gies D. R.
Published: July 2016

The massive O and B-type stars will be among the first targets of the new generation of long baseline optical interferometers (such as the CHARA Array, a 400-m diameter distributed array of five 1-m telescopes). Many of these objects are binary stars for which joint astrometric and spectroscopic observations will provide masses and distances (e.g., 15 Mon; Gies et al. 1993), but there is also great interest in resolving disks of single stars. Early interferometric observations have already resolved the flattened circumstellar disks around some Be stars (Quirrenbach et al. 1994).
Solar and stellar magnetic flux tubes
Authors: Solanki Sami K.
Published: July 2016

The magnetic field of the Sun is mainly concentrated into intense magnetic flux tubes having field strengths of the order of 1 kG. In this paper an overview is given of the thermal and magnetic properties of these flux tubes, which are known to exhibit a large range in size, from the smallest magnetic elements to sunspots. Differences and similarities between the largest and smallest features are stressed. Some thoughts are also presented on how the properties of magnetic flux tubes are expected to scale from the solar case to that of solar-like stars. For example, it is pointed out that on giants and supergiants turbulent pressure may dominate over gas pressure as the main confining agent of the magnetic field. Arguments are also presented in favour of a highly complex magnetic geometry on very active stars. Thus the very large starspots seen in Doppler images probably are conglomerates of smaller (but possibly still sizable) spots.
The determination of temperature from spectral lines
Authors: Gray David F.
Published: July 2016

Some stellar spectral lines are quite sensitive to temperature. With current techniques, we can, for example, measure temperature modulation of a few degrees. But high temperature sensitivity can also be a detriment when it masks variations in other physical parameters of interest. In such cases, we must have a way of determining the temperature precisely so that the residual differences or variations can be seen and interpreted. The situation with stellar surface features is particularly challenging because several physical variables interact simultaneously, each impressing their signature on the spectral lines. It is frequently a good plan to compare a highly temperature sensitive line to one that is insensitive or to one that has an inverse sensitivity. A good way to find suitable lines is to compare exposures of hotter and cooler stars, as illustrated in Fig. 1. Here we see lines that hardly vary (Si I), some that show modest changes (Fe I), some that show large changes (V I), and one that shows a reverse change (Fe II). Some caution is needed because differences in surface gravity and metallicity can also produce changes in line strengths. So the general idea is to play off the differences of one line compared to another and avoid any direct dependence on absolute line strengths. Yes, this is indeed nothing more than a careful refinement of determining a spectral type.
On the believability of polar spots
Authors: Byrne P. Brendan
Published: July 2016

Polar spots in Doppler Imaging maps of rapidly rotating late-type stars, especially the active components of RS CVn binaries, represent a major break with the solar paradigm, within which spots are only found at low latitudes. I examine critically the evidence for polar spots and point out that they are particularly sensitive to a number of systematic effects relating to determining reference “zero-points”.
Doppler imaging results for Ap stars
Authors: Hatzes Artie P.
Published: July 2016

Doppler imaging results for the surface abundance distribution on Ap stars are reviewed. The silicon distribution on these stars is often characterized by depleted spots near the magnetic poles and enhancements in ring-like structures at intermediate magnetic latitudes. These results are consistent with the predictions of diffusion theory. On two stars, γ Ari and CU Vir, the silicon enhancements appear very close to a magnetic pole. This can be explained if silicon is enhanced where the magnetic field has its maximum horizontal field strengthandthese stars possess a decentered dipole field. Doppler images of abundance distributions on Ap stars may be used to accurately measure the obliquity angle and to estimate the decentering parameter for a dipole field. The chromium distribution on at least four Ap stars show a depleted band coincident with the magnetic equator and depleted spots at the magnetic poles. Such a distribution can only arise if the star has a predominantly quadrupole field, or if horizontal diffusion is playing a role in the distribution of elements.
Thermal bifurcation as a driver of stellar surface inhomogeneities It's Probably Not Too Important, But Read On!
Authors: Ayres T.R.
Published: July 2016

Cool gas in the heart of the hot solar chromosphere betrays itself through anomalously strong absorptions of 4.7 μm CO lines at the extreme limb, and off-limb emissions. The origin of the “cool clouds” is thought to be a thermal instability driven by the CO itself. Questions concerning the pervasiveness and detailed structure of the “thermally-bifurcated” zones are being addressed through stigmatic spectroscopy of the solar CO bands with the NSO McMath-Pierce telescope. Here, I report recent progress, and implications for surface thermal inhomogeneities on other stars.
Photometric and Hα modulation on active stars
Authors: Catalano S. , Rodonò M. , Frasca A. , Cutispoto G.
Published: July 2016

Systematic photometric monitoring of active RS CVn binaries carried out at Catania with the automatic telescope APT-80, is being complemented with Hα low- and high-resolution spectroscopy. The relationship between photospheric and chromospheric activity is investigated in order to shed light into the complex three-dimensional structure of surface activity. Preliminary results on the photometric and Hα monitoring of the active binaries, UX Ari, RS CVn, BM CVn, HK Lac, IM Peg, V 711 Tau, and EI Eri, are here reported.
The spatial association of spots and plages
Authors: Butler C. J.
Published: July 2016

We review the evidence, from rotational modulation, for association of plages and spots on active binaries. We find reasonably convincing support for such an association from IUE SWP observations of RS CVn stars, but little or no evidence from MgII line fluxes. There is a similar lack of evidence for BY Dra systems. The results can be interpreted as evidence for: (a) the presence of active longitudes which persist on some RS CVn stars for several years, (b) high filling factors in MgII emission and (c) lower filling factors, and therefore greater contrast, in SWP emission. There is a suggestion that the association between plages and spots is more clearly seen in longer period RS CVn stars than the very active, short period, systems favoured by IUE observers.
A general confrontation between solar data and solar models
Authors: Bell R. A. , Tripicco M. J.
Published: July 2016

Since its effective temperature, surface gravity and chemical composition are well established, the Sun has often been used for tests of model stellar photospheres. There are two important potential tests – firstly, comparisons of observed and calculated line spectra and, secondly, comparisons of observed and calculated fluxes. If solar model calculations can successfully reproduce both of these data sets, then it gives confidence in the quality of models of other cool stars. However, different observations of solar fluxes do not agree with one another with the precision required in testing solar models.
The Past, Present and Future of Reference Systems for Astronomy and Geodesy
Authors: Wilkins G.A.
Published: July 2016

Standard values of astronomical and geodetic constants were adopted in the late nineteenth century for use in the determination of terrestrial and celestial coordinates, and their values were changed subsequently as better values became known. The great improvements in the precision of observation during the past decade has made it necessary to develop reference systems that also include the models and procedures that are used for the analysis of observations by particular techniques. The accurate detemination of the connections between the corresponding reference frames and the adoption of unified standards are major tasks for the future.
On the Photographic Vertical Catalog
Authors: Naumov V.A.
Published: July 2016

The Photographic Vertical Circle (PVC) was constructed in Pulkovo shops in 1962 according to idea of M. Zverev for absolute determinations of declinations of stars. Observations were made at the observatory Serro-Calan in Chile by Chilean and Soviet astronomers in 1964-1966. The PVC is an experimental instrument: it is the first reflector and the first photographic instrument for absolute observations. It has two circles and each circle has four photographic microscopes.
On the Creation of a New Catalogue for USSR Time Service
Authors: Gorshkov V.L. , Polozhentsev (Ii) D.D. , Popov A.A. , Shcherbakova N.V. , Polozhentsev A.D.
Published: July 2016

The R.A. system KSV [1] has been used in the USSR Time Service for observations with small transit instruments since 1970. Some methodological errors were made when creating the KSV [2] and the use of the proper motion system, distorted with the position errors of GC and KSV [3], make it necessary to improve the KSV system. Work on the creation of a new system KSV-2 was organized for this purpose. The catalogue included about 0.3 million computer-readable observations with small transit instruments of the USSR Time Service with mean standard deviations σ = 11 sec δ ms.
On Δδα Systematic Errors of the FK5
Authors: Kosin G.S.
Published: July 2016

An estimation of Δδα systematic errors of the FK5 has been made. Systematic differences between the FK5 and FK4 and Δδα corrections to the FK4 derived at Pulkovo have been used as given in the following series: Δδα = A′ sin α + B′ cos α + C′ sin 2α + D′ cos 2α.
On the Organization of Absolute Coordinate Determination of the FK5 Stars
Authors: Bagildinsky B. K. , Fomin V. A. , Guseva I. S. , Kirian T. R. , Nemiro A. A. , Petrov G. M. , Pinigin G. I. , Shkutov V. D.
Published: July 2016

The present-day realization of inertial coordinate system by means of traditional optical astrometry is the Fifth Fundamental Catalogue (FK5). The series of observations with new meridian instruments (CAMC, PMC-190, BAMC, HMC) show the significant correlated differences (up to 0.″1) of observational catalogues from the FK5. Moreover, FK5 mean epoch appears to be old (about 50 years ago) and FK5 proper motions would have essential errors owing to the fact that not many new original catalogues (only 25 in RA and 15 in DEC) were used when compiling FK5. It should be noted also that FK5 has a dissimilar accuracy of positions and proper motions of “old” and “new” stars.
On the Progress of the Construction of the Sukharev Meridian Automatic Horizontal Instrument (MAHIS)
Authors: Gumerov R.I. , Kapkov V.B. , Kirian T.R. , Liadovoi N.S. , Pinigin G.I. , Pozhalov A.A. , Sibilev V.P. , Schumacher A.W. , Shkutova N.A. , Shornikov O.E.
Published: July 2016

The MAHIS is the L.A. Sukharev meridian automatic horizontal instrument. It has all the advantages of the Pulkovo HMC and is devoid, or nearly devoid, of its disadvantages. A scheme of the MAHIS includes a flat mirror of D = 300 mm and two immovable horizontal tubes of D = 190 mm, focal length 8000 mm. There is a pavilion for the central unit and 2 roofed pavilions for eyepiece parts of the tubes. The MAHIS is provided with an automatic registering device, a system for meteorological data collection, and is computer controlled. The work on this telescope is being carried out at the Pulkovo, Kazan and Nikolaev observatories. The expected precision of the instrument is ±0.″05 in both coordinates with respect to systematic errors.
On the Tie of Astrometric Radio Sources to the FK4 System With Zenith Telescope ZTL-180 Observations
Authors: Prudnikova E. Ya.
Published: July 2016

A programme of Talcott pairs has been compiled at Pulkovo in order to tie bright radio sources to the FK4 system. The programme includes FK4 stars and radio stars to mag 9 (Radio stars for astrometry, Abh. Hamb. Sternw., 1982). About 150 observations of 18 pairs were made during 1985-1989. The correction

to the declination of a radio pair has been found as a difference between the “reference” latitude and the latitude derived from the observation of the radio pair. The value of the “reference” latitude was determined from observations of ordinary Talcott pairs. The standard deviation does not exceed 0.09 arcsec. A radio star can be tied to the FK4 with an accuracy not worse than 0.1 arcsec.
The Problem of the Leveling of the Reserved Net of Arcs at the Celestial Sphere by the Construction of the Reference Coordinate System
Authors: Yagudina E. I.
Published: July 2016

The methods of the rational leveling of the results of the observations of the angular distances between quasars by VLBI method were suggested. The application of these methods on the model of reserved net on sphere shows a descrease of the standard error of the quasers' coordinates after leveling by a factor of three times. We employed 10 elementary configurations constructed on 20 chosen quasars in the Northern hemisphere.
A New Concept of Constructing an Accurate Coordinate System From Ground-Based Optical Observations
Authors: Wei Mao , Xiaochun Hu , Xinjian Guo , Yu Fan
Published: July 2016

Based on the expected precision and characteristics of the Low Latitude Meridian Circle (LLMC), and the development of CCD astrometry at Yunnan Observatory, an internally consistent and non-rotating optical celestial coordinate system can be set up through observations with the LLMC and CCDs. To obtain this goal, the main work we plan to do are (1) to establish a fundamental stellar reference system of several thousand stars based on the absolute obsrvations with the LLMC; (2) to provide the accurate zero-point corrections for the system from observations of minor planets with the LLMC and CCDs; (3) to determine the precessional rotation of the system with respect to an extragalactic reference system with the LLMC and CCDs, thus transforming the system into a quasi-inertial coordinate system; and (4) to obtain the atmospheric refraciton corrections from the observations with the LLMC.
The Role of Observation With Horizontal Meridian Circle in China for Establishing an Inertial Frame
Authors: Zhi-gang Li , Guan-Rong Qi
Published: July 2016

While HIPPARCOS is expected to measure positions and proper motions with more accuracy than those obtained by ground-based instruments, what can we do in the future for ground-based instruments? The observations with them still are important for establishing an inertial frame because of the long history of observations with them and improvements in the instruments. Moreover, it is necessary to have data of observations from them for research on problems related to the Earth. The horizontal meridian circle in China (DCMT) is expected to have advantage over the classical meridian circles. The DCMT will be assembled and tested this year. It should work in the following fields: (1) observing radio stars, (2) observation of minor planets, (3) absolute determinations of IRS.
On the Problem of the Development of Astronomical Refraction Methodology on the Basis of New Technology
Authors: Sergienko V. I.
Published: July 2016

The work on construction and operation of automated systems for collection and processing astrometric and meteorological information and also of automated television systems with remote control have placed before us a number of fundamental difficulties in that hundreds of correct solutions to these problems require a systematic approach.

The most suitable cybernetics-mathematical composite for solving the problems of astronomical refraction may become the so-called hybrid-expert systems — a union of traditional expert systems with calculation-logical ones. In these systems logical-linguistic models are used together with mathematical ones.

The basic problem of ARA-C consists in obtaining a model of the environment in which light propagates and also to give a notion of interaction between electrons (environment) and photons (light).

It is proposed to use in this system a model of light interaction with environment built up on special formalisms of artificial intellect (logical-linguistic model). The basic principal in hybrid-expert system ARA-C operation must be mathematical modelling and calculation experimentation. In the proposed hybrid-expert system knowledge is presented on three levels—object, mathematical and programmed. Functioning of the lower levels of ARA-C is connected with formulation of the calculation problems. A calculation problem presented to a technical model determines a partial order on a twopart column of mathematical correlations.
The Study of the Structure of 142-Year Series of Pole Coordinates
Authors: Rykhlova L.V. , Kurbasova G.S.
Published: July 2016

The 142-year series of pole coordinates in the system of mean pole of epoch of observation are used for the investigation of the Chandler period. The method of the best approximation of the initial data with the step of 1.5 years by means of quasi-polynomials is used.
Effect of the New Equinox Definition on the Zero-Point of Longitude of the Indian Calendar
Authors: Bhatnagar A. K.
Published: July 2016

Indian calendars follow a sidereal system of astronomy taking a fixed initial point on the ecliptic as the origin from which the longitudes are measured. Its position for the official Indian Calendar has been defined by the Calendar Reform Committee (1955) as the point on the ecliptic whose true tropical longitude was 23°15′00″ as on 21 March 1956, 0h UT. Its position was determined upto the year 1984 in accordance with Newcomb's value for general precession using the relation

where T is in centuries of 36525 ephemeris days from 1900 January 0.5 ET. Recent changes in the location and the motion of the equinox with reference to the epoch J2000.0 have necessitated corresponding changes to be included in the determination of the mean and true positions of the above initial point. The new algorithm worked out is

where T is in Julian centuries of 36525 days from J2000.0.
The Construction of a Frame of Homogeneous Accuracy Based on Space Observations
Authors: Vlasov B. I.
Published: July 2016

A definition of the initium-method of spherical arcs is proposed. Theoretical and operational aspects of the method are discussed. Geometrical homogeneity is achieved by measuring arc distances between vertices of the octant (a right-angle spherical triangle) and the object in question. The measurements are made with the use of the standard angle γ on board a satellite with rotation rate reconstructions with splines. The chosen standard angle is discussed. The accuracy estimations are given.
High Accuracy Algorithms of Numerical Prediction of the Motion of Solar System Bodies
Authors: Bordovitsyna T.V. , Shefer V.A.
Published: July 2016

A brief summary of results obtained by the authors for investigations of the efficiency of numerical prediction algorithms for natural and artificial minor bodies using regularizing and stabilizing transformations is given.
On the Errors of the Ephemerides Derived From Optical Observations of Planets
Authors: Kharin A.S. , Kolesnik Yu.B.
Published: July 2016

On the basis of about 40 000 optical observations of the Sun and major planets obtained with 33 meridian and photographic instruments during last 3 decades a comparative consistency analysis of old and new ephemerides with these observations has been made.

For the inner planets significant improvement in RA is confirmed while in DEC it is less apparent. For outer planets the improvement is strongly marked in DEC for Jupiter and Saturn and espesially for Neptune in both coordinates. Significant systematic differences between meridian and photographic observations are detected.
On The lunar Secular Acceleration: A Possible Approach
Authors: Protitch-Benishek V.
Published: July 2016

The secular quadratic term in the expression of the Moon's longitude has been introduced empirically after the conclusion that its mean motion is not constant (Halley, 1695).

But, the explanation of this term and also of its numerical evaluation presented and still presents in our time great difficulties. All efforts, namely, to obtain an exact agreement between observed and theoretical value of Moon's secular acceleration were unsuccessful: the first of these two values exceeds always the second one by a very large amount. This discordance and unexplained residuals (O – C) in the mean longitude of the Moon gave rise finally to the statement that these are due to a retardation and irregularity in the Earth's rotation. But, after hardly a fifty years, this hypothesis revealed even more new difficulties and questions concerning also the problem of stability of the Earth-Moon system. It seems that there is a true reason for which this problem occurs as one of the unsolved problems of Celestial Mechanics (Brumberg and Kovalevsky, 1986; Seidelmann, 1986).
Pulsar Astrometry—Availabilities and Relativistic Aspects of a Pulsar Reference Frame
Authors: Doroshenko O.V. , Ilyasov Yu.P. , Kopejkin S.M. , Sazhin M.V.
Published: July 2016

We propose a quasi-inertial four-dimensional reference frame in the solar system asymptotically-flat spacetime on the basis of pulsar astrometry techniques. The Pulsar Reference Frame (PRF) consists of the Pulsar Time Scale (PT) and the the Pulsar Reference System (PRS) on the sky.
The Definition and Stability of Local Inertial Reference Frames
Authors: Treuhaft R. N. , Lowe S. T.
Published: July 2016

Inertial reference frames spanning approximately 10°-30° square on the sky and capable of locating objects to few-hundred microarcsecond accuracies are useful for a broad class of astrometric measurements. Deep space tracking and general relativistic angular deflection experiments are examples of astrometric measurements which can profitably reference the positions and/or motions of objects to a field of radio sources in a local frame. A method for defining local inertial reference frames has been developed based on Very Long Baseline Interferometry (VLBI) measurements of extragalactic radio sources. By observing the radio emission from the object to be located in the frame, as well as that from about five radio sources which define the frame, dominant systematic astrometric errors can be minimized through parameter estimation. The entire reference frame measurement is of the order of 30 minutes including all the sources in a frame. The limiting error for single-epoch position determination in a local frame is the unknown structure of both target and reference objects. Structure can cause systematic milliarcsecond-level errors. The limiting error for epoch-to-epoch differential position measurements is tropospheric fluctuations, assuming that the radio source structures do not change from one epoch to the next. Preliminary results of an epoch-to-epoch measurement of relativistic gravitational deflection by Jupiter, in which the total deflection was about 600 microarcseconds, suggest that the local reference frame is stable at the 240-microarcsecond level over twelve days. Data have been taken at longer time intervals to determine the annual stability of the frames. At the time of preparation of these proceedings, those data have not yet been analyzed.
An Extragalactic Reference Frame From DSN VLBI Measurements–1989
Authors: Sovers O. J.
Published: July 2016

Assessment of the impact of recent improvements in Deep Space Network (DSN) instrumentation, as well as of joint data analyses, provide a prognosis for the accuracy level to be expected in future realizations of an inertial radio reference frame. Intercontinental dual-frequency radio interferometric measurements during 68 sessions (including two recent sessions employing Mark III instrumentation) from 1978 to 1989 using NASA's DSN stations in California, Spain, and Australia give 8900 pairs of delay and delay rate observations. Analysis yields a catalog of positions of 200 extragalactic radio sources north of —45° declination. The resulting source position formal uncertainty distributions peak below 1 milliarcsecond, with three fourths being smaller than 2 mas. Comparison with independent measurements shows some evidence for systematic errors at the milliarcsecond level.
Corrections to the Luni-Solar Precession From Radio Positions of Extragalactic Objects
Authors: Walter H. G.
Published: July 2016

In an attempt of a realization of the radio reference frame a compilation catalogue of positions is derived from independent observation catalogues of extragalactic objects the coordinates of which had been determined by means of Very Long Baseline Interferometry. The compilation catalogue comprises 209 objects which are divided into a core consisting of 50 objects having mean positional accuracies of 0.5 milliseconds of arc (mas) and an extension with positional accuracies better than 2 mas. Comparison of this catalogue with an independent compilation catalogue led to confidence limits at the 1 mas level. - The compilation catalogue is supposed to represent a static reference frame of fixed extragalactic points. As the epochs of the contributing observations span nearly 10 years it was tried to interpret the apparent motion of the fixed points recognizable in the observation catalogues as an effect of luni-solar precession. The pilot study points at a reduction of the conventional value of about 2 mas per year.
In-Orbit Status of the Hipparcos Astrometry Mission
Authors: Perryman M.A.C.
Published: July 2016

The Hipparcos satellite was successfully launched by Ariane 4 flight 33, from French Guyana, on 8 August 1989. However, the apogee boost motor, designed to place the satellite into its intended geostationary orbit, failed to function, and the satellite was left in a highly elliptical transfer orbit. After a perigee raising manoeuvre, using the hydrazine propulsion system, the orbital parameters are approximately: apogee 35900 km, perigee 526 km, eccentricity 0.72, inclination 6.8°, orbital period 10h 40m.

Operational procedures have had to be revised during the first weeks of satellite operations, due to the non-nominal orbit. Commissioning and calibrations have taken longer than foreseen because of the operational difficulties and observational overheads, but routine observations commenced on 27 November. The essential differences between the nominal and the present missions are that observations can only be conducted for about 30-40 per cent of real time in the present mission, and the fact that the actual lifetime of the mission is still rather uncertain, and possibly somewhat shorter than anticipated. This paper gives a summary of the present satellite status, measurement results obtained so far, and in indication of the scientific goals that may be achievable with the present mission.
The Reference Frame Determined From the Observation of Minor Planets by Hipparcos
Authors: Morando B. , Bec-Borsenberger A.
Published: July 2016

The observation of minor planets by Hipparcos offers the opportunity to obtain high precision positions for some minor planets. About fifty minor planets are on the programme. Their ephemerides had to be improved in order to reach a precision of 1 arsec and occultations by the Earth and the Moon had to be predicted.

From the position of a minor planet on reference great circles at different times better values of the initial position and velocity will be deduced but the reduction of the observations of the minor planets have to take into account the displacement of the photocentre relative to the centre which is due to the shape, the phase effect and the scattering properties of the surface. For some very small planets considered as star like this diplacement will be small and the precise positions obtained will allow to position the dynamical reference system relative to the Hipparcos system. For the bigger minor planets the observations by Hipparcos may give informations on the shape and scattering properties of the surface.
Proper Motions With Respect to the Extragalactic Reference Frame
Authors: Klemola A. R.
Published: July 2016

The Lick proper motion program, one of several using galaxies as a reference frame, is summarized with a statement of work accomplished for the non-Milky Way sky. The problem of identifying relatively transparent regions at low galactic latitudes is discussed, with tabular results presented for 41 windows from the literature having observable galaxies. These fields may be helpful for attaching stellar proper motions directly to the extragalactic frame.
The Yale-San Juan Southern Proper Motion Program (SPM)
Authors: Van Altena W.F. , Girard T. , López C.E. , López J.A. , Molina E.
Published: July 2016

The Southern Proper Motion Program (SPM) is described and progress in the execution of the second-epoch is outlined, as are the reduction methods. Recent changes in the instrumentation, including the addition of a computer control room to the astrograph building and the construction and operation of a new survey machine are discussed.
The General Catalogue of Stellar Proper Motion With Respect to Galaxies With Astrophysic Supplement
Authors: Kharchenko N.V.
Published: July 2016

Within the limits of the programme of studying of the Main Meridional Section of the Galaxy the General Catalogue of astrometric data of 26500 stars has been compiled. Corrections to the precession constants and stellar secular parallaxes have been determined.
Individual Star Catalogues of the Unified Time Service of Kharkov Scientific and Research Institute and Kharkov University Astronomical Observatory
Authors: Izmailov S. P. , Litkevich N. G. , Simonenko V. D. , Turenko V. I.
Published: July 2016

The Time Service Catalogue (TSC), which is obligatory for use in all USSR Time Services, was created for the epoch 1958 in the 1970s. Research done in the succeeding years detected a seasonal variation of TSC errors. Thus, a new Time Service Catalogue (TSC2) was required, in order to remove the seasonal errors as well as to satisfy the increasing demands for accuracy in the determination of universal time. During 1986-88 the data of Kharkov Common Time Service for 1980-1987 were reanalyzed using the new system of astronomical constants and two new catalogues were produced.
A Presentation of the Work Performed With the Belgrade Large Meridian Circle During the Period 1968-1988
Authors: Sadžakov S. , Cvetković Z. , Dačić M.
Published: July 2016

The work performed with the Belgrade Large Meridian Circle and the results obtained during the last twenty years are presented.
The Flagstaff Measuring Machine
Authors: Westerhout Gart , Monet Dave
Published: July 2016

The U.S. Naval Observatory is building a measuring machine which will hold four PSS plates simultaneously and will automatically measure them, in a highly controlled environment, in about 12 hours. The images will be recorded by two camera subsystems with a scale of 0.9 arcseconds/pixel on a 0.33 × 0.26 degree CCD frame. The original glass plates of the PSS-II and glass copies of the PSS-I will be measured. This is a joint CALTECH-USNO program.
Interior Structure of the Sun
Authors: Christensen-Dalsgaard Jørgen
Published: July 2016

Observations of solar oscillations have provided us with detailed information about the solar interior. Here I consider three examples of results obtained in such helioseismic investigations: i) the effect of the equation of state on the comparison between observed and theoretical frequencies; ii) a determination of the depth of the solar convection zone; and iii) indications of deviations from standard models of the structure of the solar core.
Mechanisms for Dynamo Mode Excitation
Authors: Hoyng P.
Published: July 2016

Dynamo theory of the solar magnetic field finds itself in a period of reappraisal since about 1980. There are two reasons for this: (1) The required increase of the angular speed Ω, with decreasing r is neither found in numerical simulations nor measured by helioseismology. (2) Mean field modeling shows often little regard for inherent physical restrictions and selfconsistency.
Plasma Damping of Gravitational Waves
Authors: Sivaram C.
Published: July 2016

The possibility of the damping of plane gravitational waves while propagating in a plasma medium is considered. The gravitational plasma frequency, is for a neutron star medium ~ 103Hz, which is the same as the frequency of the gravitational waves emitted by a collapsing star. So resonant damping of such waves within a collapsing star is probable. Estimates are made for the damping length for dense and dilute plasmas (also in the presence of magnetic fields). Analogies with Landau damping are made. Applications to other astrophysical situations are outlined.
Energy Release in Stellar Flares
Authors: Pallavicini R.
Published: July 2016

Flare-like events similar to those observed on the Sun occur on many different types of stars, particularly on late K and M dwarfs. Although the physical mechanisms responsible for these events remain largely unknown, it is likely that the flare energy derives from dissipation of magnetic fields as is the case for solar flares. We review the basic observational facts that suggest an analogy between solar and stellar flares and we discuss how the different physical conditions occurring on stars may affect the application of current solar-type models to the stellar case. We show that, in spite of a qualitative agreement found between model predictions and observations, there is still no convincing evidence that stellar flares are simply scaled-up versions of solar flares. Major advances in the observations of stellar flares are required before this fundamental question can be safely addressed.
Chromospheric and Coronal Heating Mechanisms
Authors: Ulmschneider P. , Narain U.
Published: July 2016

Stellar chromospheres lose energy, predominantly, via radiation and coronae via conduction, radiation and stellar wind flows. To prevent these hot layers from rapidly cooling down to photopsheric temperature some source of heating must be present.
Sunspot Motions from a Study of Kodaikanal and Mount Wilson Observations
Authors: Howard Robert F. , Sivaraman K. R. , Gupta S. S. , Gilman Pamela I.
Published: July 2016

A study of the daily motions of individual sunspots and of sunspot groups has been undertaken using Kodaikanal and Mount Wilson white-light observations. The Mount Wilson measurements were completed several years ago, and the Kodaikanal measurements have recently been started, using a technique identical to that used for the Mount Wilson data. Both data sets started early in this century, and both have continued to the present time. Preliminary results of a comparison of the two data sets are presented which show a good agreement between them in spot areas and motions. Analysis of the combined data set for the years that are available so far indicates that many more spots are available in such a reduction because the 12-hour time difference between the two sites allows for a more certain identification of individual spots from one observation to the next than in the case when data from only one site are used. This greatly increases the number of sunspots available for motion studies, particularly the smaller sunspots. Preliminary rotation and latitude drift reduction from the combined data set confirm earlier results from the Mount Wilson data alone.
Observations of Magnetic Features with the German Solar Telescopes at the Observatorio del Teide/Tenerife
Authors: Kneer F. , Soltau D. , Wiehr E.
Published: July 2016

The German solar facilities at the Obsrvatorio del Teide are described first. Then, a few examples of recent results from magnetic features are given: spatial variation and velocity fluctuation of small-scale magnetic fluxtubes in the quiet Sun, Evershed flow and magnetic field in connection with penumbral fine structure, and magnetic field variation in sunspot umbrae.
A Case For Alfven Wave Heating
Authors: Califano F. , Chiuderi C. , Einaudi G.
Published: July 2016

The resistive dissipation of Alfvén waves in magnetically structured media is examined within the framework of an analytically solvable model in plane geometry. A new class of rapidly oscillations solutions is found, for which the role of resistivity extends to the whole system.
Implications of Tension Free Equilibria for Pre-Flare Energy Buildup
Authors: Venkatakrishnan P.
Published: July 2016

The downward tension force is known to be extremely small at the locations of highly sheared magnetic fields. The free energy in such tension free fields is shown to be dependent on the plasma density. The excess of this free energy over that available in a force free configuration is estimated and shown to be sufficient to drive instabilities which could possibly initiate a solar flare.
Energy Balance in Prominence-Corona Transition Regions
Authors: Chiuderi C. , Chiuderi Drago F.
Published: July 2016

Prominences are sheets of cold (< 104 K) plasma totally imbedded in the hot (> 106 K) coronal plasma. A Prominence-Corona Transition Region (PCTR) is therefore present all around it.
Numerical Simulations of Solar Disturbances and their Interplanetary Consequences
Authors: Dryer M. , T. Wu S. , R. Detman T.
Published: July 2016

Responses of the solar atmosphere and interplanetary medium to simulated solar disturbances were studied by time-dependent, MHD numerical simulations. This deterministic initial-boundary value problem was attacked in the classical way: a representative steady state is first established, then input parameters at the lower near-Sun boundary are perturbed. We discuss a number of 2- and 3-dimensional examples of coronal mass ejection (CME) simulations and some current controversies concerning the basic process of CME initiation. Footpoint shearing motion is tested to see whether it can provide a reasonable mechanism for CME development from arch filament configurations.

We also demonstrate possible interplanetary consequences to CME-like disturbances by using 3-D simulations to determine the dynamic response of the solar wind to a plasmoid injection from an eruptive filament or prominence. We also discuss the separate possibility whereby a plasmoid may be generated in the interplanetary medium by a solar-generated shock that propagates through a heliospheric current sheet. Application of the 3-D model for the interpretation of interplanetary scintillation observations is also discussed.
Nature of Large-Scale Solar Magnetic Field and Complexity of HCS as Observed in Interplanetary Plasma
Authors: Girish T E , Prabhakaran Nayar S R
Published: July 2016

The properties of the interplanetary plasma and magnetic field near 1 AU is determined by the nature of large-scale solar magnetic field and the associated structure of the heliospheric current sheet (HCS). Magnetic multipoles often present near the solar equator affect the solar wind plasma and magnetic field (IMF) near earth's orbit. The observation of four or more IMF sectors per solar rotation and the north-south asymmetry in the HCS are observational manifestations of the influence of solar magnetic multipoles, especially the quadrupole on the interplanetary medium (Schultz, 1973; Girish and Nayar, 1988). The solar wind plasma is known to be organised around the HCS. In this work, we have investigated the possibility of inferring i) the relative dipolar and quadrupolar heliomagnetic contributions to the HCS geometry from the observation of four sector IMF structure near earth and ii) the properties of the north-south asymmetry in HCS geometry about the heliographic equator from IMF and solar wind observations near 1 AU.
Coherent Radiation from Electrostatic Double Layers
Authors: Kuijpers Jan
Published: July 2016

The radiation properties of electrostatic double layers (DLs) are of potential significance for cosmic magnetic explosions. If the emission is sufficiently intense it can serve as a diagnostic tool for particle acceleration by localized strong potential drops in current-carrying plasmas. Moreover such intense emission may form the explanation of some of the observed intense and narrow-band bursts of radiation from stellar and planetary magnetospheres. Here we study the efficiency of two coherent radiation processes: antenna radiation and a maser process. It is found that both processes can operate in the DL to produce intense and narrow-band emission. Antenna radiation occurs if the dimensions of the double layer are smaller than the wavelength of the emitted radiation. This process is therefore relevant to laboratory rather than to astrophysical plasmas. The maser on the other hand requires an amplification length inside the double layer much larger than the emitted wavelength, and can lead to observable emission in astrophysical circumstances. The growth is exponential and the rate depends only on the electric field energy density of the DL. Since the latter is externally controlled by the electric circuit it is a constant for the emission process so as to constitute a true maser. The maximum brightness temperature is of order 1025K.Masing radiation from electrostatic DLs is therefore a candidate for some of the observed intense narrow-band cosmic radio emission.
Electrons and X-Ray Emission of Solar Flares
Authors: Kurt V. G.
Published: July 2016

A statistical analysis of solar flare X-rays and interplanetary particle fluxes, measured onboard VENERA-13, 14 Spacecraft, was performed. The correlation of fluences for different manifestations of solar flares is strong, especially for fast electrons and hard and soft X-ray emissions. Frequency dependence on fluence value ϵi for practically all Kinds of solar flare emission can be described by power law ν (ϵ > ϵO) ∼ ϵ−0.45±0.15 which does not change significantly with solar activity. For different Hα flare importances the values of ϵi were obtained. It is proposed that appearance of certain energy flare frequency is strongly dependent on some scale factor.
Energetic Particles in a Flare Loop: Spectra and Radiation Signatures
Authors: Bespalov P. A. , Zaitsev V. V. , Stepanov A. V.
Published: July 2016

It has been shown that high energy particle spectra, particle dynamics, and radiation in a flare loop are determined by wave-particle interactions. The electron-whistler interaction occurs under conditions of strong pitch angle diffusion that makes the particle distribution function isotropic. The flare loop electrons retain information about the particle source spectrum. The interaction of energetic ions with Alfven waves is characterized by strong, moderate, and weak diffusion. The time delays in hard X-ray and gamma-ray emission during one-step acceleration processes might be understood in terms of a trap-plus-turbulent propagation model. The density of precipitating particles is less than or equal to the trapping one. Radiation signatures of flare loop electrons are discussed.
Role of Beam Foil Spectroscopy in Understanding Basic Plasma Processes on the Sun
Authors: Krishnamurty G. , Raja Rao P. Meenakshi , Sarswathy P. , Raja Sekhar B.N.
Published: July 2016

Beam-Foil spectroscopy(BFS) has proved to be a valuable technique for the determination of radiative lifetimes of excited atomic levels leading to the evaluation of the transition probabilities. The time- resolved nature of the decay process in a collisionless environment is a unique characterstic of the beam-foil light source. The relevance of BFS to astrophysics comes from the importance of radiative transition probabilities in the quantitative analysis of optical spectra. Stellar abundances are obtained from the intensity of a spectral line which essentially is a product of the abundance of the element in the source and the probability of the transition. Thus the evaluation of accurate values of transition probabilities contribute significantly to stellar abundance analysis.