bluuebunny/crossref_metadata_2025_split huggingface dataset:
Some Problems of Wide-Field Astrometry by a Short-Focus CCD-Astrograph
Authors: Guseva I. S. 
Published: June 2019

The worldwide application of CCDs in astronomy is concerned mainly with the problems of photometry and spectrophotometry. Astrometry with CCDs is limited by the small fields of view and now is used to solve some special tasks such as parallax determination of faint stars, observations of QSOs, etc. Very interesting results were obtained using a CCD with a meridian circle in a drift scanning mode to solve the problem of the extension of the reference system to stars of 16th–17th mag and the linkage between radio and optical reference frames (Stone 1994).Based on the preliminary results of our observations, some proposals on astrometry with CCDs are discussed in the paper. The aim is to show the use of short-focus telescopes with CCDs in the mode of traditional astrographs. Numerous tasks may be solved with such instruments more simply and correctly than with meridian instruments in a drift scanning mode.The problems of the application of CCDs with short-focus optics are also discussed. Some effects of CCD properties on the accuracy of astrometric and photometric measurements are also considered.
Performance of a 2048 × 2048 Pixel Three-Side-Buttable CCD Designed for Large Focal Planes in Astronomy
Authors: Cortiula J. A. 
Published: June 2019

TH78997M is a 2048 × 2048 pixel full-frame CCD sensor featuring 15 × 15 micron pixels, MPP operating mode, four parallel outputs and buttability on three sides. This new device makes it possible to build very large focal plane detectors for telescopes (two × n butted CCDs) with less than a 25 dead pixel zone between adjacent sensors. Other features are high full-well capacity (typically 180 Ke−) and very low dark current thanks to four phase MPP clocking which allows a very long exposure time together with a high S/N ratio.The readout of a complete frame is achieved through four parallel outputs running at frequencies ranging from ten KHz up to five MHz per output. The four on-chip amplifiers have been designed to be completely user controlled and to meet most of terrestrial and spaceborne astronomy requirements: very low noise (less than 4e− at 50 KHz, −40 degrees C), very low power consumption (150 micro-W/amplifier at 10 KHz/output), linearity better than 0.5% together with high conversion factor (4.2 micro-V/e−) over 2.5 V output range. The packaging of the device is compatible with the good flatness of the chip and with the low parasitic “cosmic event” rate thanks to specific care in selecting the packaging material.
Solar Microwave Emission in Active Regions
Authors: Lokanadham B. , Subramanian P. K. , Reddy M. Sateesh , Reddy B. M. , Lakshmi D. R. 
Published: June 2019

Multi–frequency Observations of Solar Microwave bursts recorded during solar maximum period 1980–81 are analysed and compared with x–ray data for studying the nature of microwave emissions from active regions. Most of the microwave burst spectra showed that the spectral index below the peak frequency is always less than 2.The magneto-ionic conditions of the burst sources and the electron energies as obtained from these multi-frequency observations of the bursts showed that the centimetric and x-ray observations are satisfactorily explained, if the emitting regions are dense, hot and compact associated with strong magnetic fields of a few hundred gauss, suggesting that the thermal gyroresonance process is the most likely emission mechanism involved in the emission of microwave and x-ray radiations from the active regions of sun.
Concepts of Reference Systems
Authors: Guinot Bernard 
Published: June 2019

With the atomic clocks and VLBI catalogues of extragalactic sources, the theory-independent references for both space and time will be quasi ideal in their underlying principles (non-rotation of very distant objects, constancy of the frequencies associated to atomic transitions). The paper is an attempt to clarify the role of these natural references with respect to those which are implicitly defined by the dynamical theories.The example of time is discussed, since it already gave rise to serious difficulties, but similar problems may occur about the space references. Such complexities are suprising: one could have expected simplifications from the use of references which are not entangled with theory. Some suggestions are made for the use of these natural references.
Design Characteristics of the 1.56 m Astrometric Telescope and its Usage in Astrometry
Authors: Lai Wan , Neng-Hong Zhu , Lan-Juan Wang , Zheng-Hua Yang , Yi-Jin Zheng 
Published: June 2019

The 1.56m astrometric telescope (Fig. 1) is designed mainly for determining trigonometric parallaxes of faint stars.In order to keep the design as simple as possible, the telescope has only a Ritchey-Chretien focus and will accomodate plates 200 × 200 mm. We also plan to design several pieces of auxiliary equipment such as a medium dispersion grating spectrograph, a photometer, a reducing camera, and an electrographic camera, all of which are in the second stage of engineering. The whole project consists of four parts.
The Oscillating Slit Micrometer of the Meridian Circle PMC 190 Tokyo
Authors: Kühne C. , Miyamoto M. , Yoshizawa M. 
Published: June 2019

The meridian circle installed at the Tokyo Astronomical Observatory in 1982/83 is equipped with a photoelectric Double Slit Micrometer which is one of the basic prerequisites for fully automatic observation. A slit plate is located in the image field of the telescope. It oscillates parallel to right ascension while being guided at the mean traveling speed of the star.The paper describes the procedure by which the moment of the star passage through the instrument's meridian and declination is determined. Furthermore, the autocollimation devices are described which are an essential prerequisite for the determination and periodical checking of the instrumental errors.Also, the measuring devices for the passage of the sun and the moon are dealt with briefly.
The Global Mass, Energy and Photoionization Balance of the Disk-Halo Interaction
Authors: Norman C. A. 
Published: June 2019

The observational evidence for chimney models of the interstellar medium is reviewed. The variation of the state of the interstellar medium of an external galaxy between the three-phase mode, the chimney mode and the two-phase mode as a function of: galaxy type, galactocentric radius within a given galaxy, and the time varying star formation rate is discussed.In the context of the chimney models it is shown how the photoionization of the halo can be achieved by utilizing both direct ionizing rays from the central OB association and diffuse reradiation from the chimney walls that will create an extended low ionization halo around chimneys with SII/Hα ~ 0.5.A number of considerations for future studies that are a direct result of the work discussed at this conference are outlined.
Some Recent Results from UV Observations
Authors: Seaton M. J. 
Published: June 2019

UV observations with IUE have led to recognition of the importance of di-electronic recombination in PN, for the calculation of ionization equilibria and for production of the features C II λ1335 and C III λ2297.The determination of C abundances is discussed. In high-excitation nebulae one must allow for absorption of C IV λ1549 by dust. It has been shown that C/O ≤ 0.5 for five PN with a silicate IR feature and that C/0 ≳ l for four with a SiC feature.Dust opacities τD have been deduced from observed ratios (C IV λ1549)/(C III λ2297) and (C II λ1335)/(C I λ4267). The values obtained, τD ≃ 0.1, are consistent with the observed strength of thermal infra-red emission.Earlier UV observations of PN were made by Pottasch et al. (1978) using ANS. Results obtained using IUE support neither their downward revisions of star temperatures nor their claim that a number of stars with TZ(He II) >> TZ (H I) are optically thick for H I.From IUE observations it is concluded that the planetary κ 648 in M 15 has C/O = 2.4 and that its central star has a temperature of 30 000 κ and a luminosity of 1700 L⊙.
A Neutral Hydrogen Cloud in the Vicinity of the Elliptical Galaxy NGC 4318
Authors: Bottinelli L. , Fraix-Burnet D. , Gouguenheim L. 
Published: June 2019

NGC 4318, in the Virgo Cluster, has the following optical properties:
—morphological type: E (Nilson, 1973)—BoT magnitude : 13.8 (Nilson, 1973)—photometric axis : 0.8′ × 0.6′ (Nilson, 1973)—heliocentric radial velocity:
−300 km s−1 (Arakelian et al., 1975)1247± 15 km s (Tonry, 1981)1215 km s−1 (Huchra et al., 1983)
Coordinate system in general relativity
Authors: Fukushima Toshio 
Published: June 2019

The proper reference frame comoving with a system of mass-points is defined as a general relativistic extension of the relative coordinate system in the Newtonian mechanics. The coordinate transformation connecting this and the background coordinate systems is presented explicitly in the post-Newtonian formalism. The conversion formulas of some physical quantities caused by this coordinate transformation are discussed. The concept of the rotating coordinate system is reexamined within the relativistic framework. A modification of the introduced proper reference frame named the Natural Coordinate System (NCS) is proposed as the basic coordinate system in the astrometry. By means of the concept of the natural coordinate system, the relation between the solar system barycentric coordinate system and the terrestrial coordinate system is given explicitly. To illustrate the concept of NCS, we quote in the following the definition of the non-rotating NCS comoving with the Earth, i.e. the Terrestrial Coordinate System (TCS) (Fukushima et al., 1986a, 1986b):1) Consider a fictitious spacetime with the metric obtained by subtracting the direct terms due to the Earth from the true metric in the solar system Barycentric Coordinate System (BCS).2) The time coordinate axis of the TCS is defined as the worldline of the geocenter, i.e. the timelike geodesic of the geocenter in the above ficititious spacetime.3) The unit of time in the TCS, terrestrial second sT, is defined as the unit of time in the BCS, barycentric second, multiplied by a certain factor so that there exist periodic differences only between the time coordinate of any event in the TCS, i.e. TDT, and the corresponding time coordinate in the BCS, i.e. TDB.4) The space coordinate axes of the TCS are defined as three geometrically straight lines satisfying that they and the time coordinate axis of the TCS are orthogonal to each other at the geocenter in the above fictitious spacetime, and that the coordinate triad constructed by them is symmetric.5) The unit of length in the TCS, terrestrial meter mT, is defined as the length so that c = 299792458 mT/sT.
Comparisons of ET(solar), ET(lunar), UT, and TDT
Authors: Markowitz Wm. 
Published: June 2019

SummaryA fundamental dynamical scale, ET(solar), was formed from absolute, meridian circle observations, from 1835 to 1982. At 1967.0 the ET(solar) and SI seconds were equal to 1 part in 109 and, from Morrison's (1979 a) ET(lunar) scale, the ET(ILE) and SI seconds were equal to 1 part in 1010. The long term fluctuation in the Earth's rotation has been parabolic, instead of sinusoidal, for at least 350 y.
Effects of variations in Earth rotation on extended use of GPS orbits
Authors: Klepczynski W. J. 
Published: June 2019

SummaryTime transfer data, derived from single frequency observations of GPS satellites, have shown a unique bowing characteristic in the residuals with an amplitude which sometimes amounts to about 80 ns. Investigations attempting to explain this characteristic have so far been unsuccessful. The studies have been concerned with hardware and software effects. The hardware studies have:(a) compared data obtained with single frequency receivers with data obtained simultaneously with dual frequency receivers which eliminate the effects of the ionosphere;(b) compared data obtained with different kinds of single frequency receivers; and(c) compared data obtained simultaneously with different kinds of antennas, including one designed to minimize the effects of multipath.
Aspects of Mass Loss and Angular Momentum Loss in Binaries Containing Cool Components
Authors: Eggleton Peter P. 
Published: June 2019

Cool stars show evidence of dynamo activity which is stronger with more rapid rotation. Tidal friction in a moderately close binary can be a cause of relatively rapid rotation, so that cool components in such binaries are presumably liable to stronger stellar winds than single cool stars. As a consequence, the binary can be subject to orbital angular momentum loss. Both the mass loss and the orbital angular momentum loss can be on a timescale comparable to nuclear evolution in a red subgiant, or even faster. RS CVn stars probably give the best possibility of measuring these processes, although some observational data are difficult to reconcile with simple theories.Barium stars, and symbiotics, may both be affected by these processes. They must be the products of evolution of moderately wide binaries, as must such objects as cataclysmic variables. I attempt to define the ranges of zero-age parameters necessary to produce such varied objects. A simplistic model of the distribution of stars brighter than 6th magnitude (a ‘Theoretical Bright Star Catalogue’) suggests that for every three Ba stars with a measurable orbit, there should be one main sequence ‘Ba star’.
A Cut of Large-Scale Structure Across the Coma Supercluster
Authors: Karachentsev I.D. , Kopylov A.I. 
Published: June 2019

SummarySpectral survey of 245 galaxies with mB⩽17.5 in the narrow strip {+28° 20′>DEC>+28°10′, 15h28m0>R.A>10h42Mm0} confirms a bubble-like type of the large-scale structure around the coma supercluster, have been founded by Lapparent et al. (1986). A correlation function in the volume has the power index γ=1.5 and the correlation radius rO= 29 Mpc (H=75 Km/s Mpc). For the sample of 14 voids their mean diameter <DV> equals to (33±3) Mpc. This value coincides with the correlation scale rO= 32 Mpc for Abell clusters, and also with the mean length of “God finger” for a rich cluster, 2√ 3σvH−1 = 32Mpc. We note a presence of a preferential orientation of voids toward the Coma supercluster, <Dvrad>/<Dvtan>= 1.15±0.8, that corresponds to a possible peculiar flow toward/outward Coma with Vpec∼400±200 (Km/s) at a scale ∼100 Mpc.
A New Catalog of Superclusters of Galaxies
Authors: Kalinkov M , Kuneva I. 
Published: June 2019

A technique developed by us for searching for superclusters of galaxies (Kalinkov and Kuneva, 1985, 1986) has been applied to the both main catalogs of clusters of galaxies, as well as to some subcatalogs:
(i)all Abell (1958) clusters,(ii)rich A-clusters (RG > 0),(iii)very rich A-clusters (RG > 1),(iv)X-ray A-clusters,(v)Zwicky et al. (1961–1968) clusters,(vi)A-clusters, identified in the Zwicky catalog.
Some Remarks on Observational Problems for Disk-Galaxy Evolution
Authors: Sanromà M. , Salvador-Solé E. , Solanes J.M. 
Published: June 2019

Observational objections against an important role of evolution in morphological differentiation of disk - galaxies (Burnstein 1979, Dressier 1980b, Kent 1985) are summarized together with the results of their det ailed analysis (Salvador-Solé et al. 1987a and 1987b):
i)Morphological segregation is independent on cluster characteristics.
Astrometry And Data Centers
Authors: Jaschek C. 
Published: June 2019

SummaryThe paper tries to provide some background to answer the problem if old astrometric data should be stored. The cases of the AC and the CdC are examined, as well as the storage of some more recent catalogues on optical disc. Finally the necessity of producing general catalogues (of the SAO type) for non-astrometrists is underlined, to satisfy the needs of the astronomical community.
Comparison Of The Effect Of Various Solar System Ephemerides On Equator And Equinox Solutions From Six-inch Transit Circle Observations Of The Sun
Authors: Yao Zhen-Guo , Smith Clayton 
Published: June 2019

Using observations of the sun made with the Washington six-inch transit circle from 1911 to 1971, equator and equinox corrections based on Newcomb's, DE102, and DE200 ephemerides are given for each of six catalogs of results of observations made during that period. Each of these catalogs was observed and discussed fundamentally, that is, in such a way as to decouple the system of the catalog positions from dependence on previously given systems of catalog positions and proper motions.Variations of the solutions for the equator and equinox corrections and of earth orbital parameters including corrections to the ephemeris mean longitude of the sun, the mean obliquity of the ecliptic, the mean longitude of perihelion, and the mean eccentricity of the earth's orbit are discussed for solutions based on the independent catalog systems and on the catalog systems referred to the FK4 and to an improved FK4 in which an epoch dependent correction to the right ascension zero point has been applied.
Brightest Stars in Galaxies as Distance Indicators
Authors: Sandage Allan 
Published: June 2019

The current status of the absolute magnitude calibration of the brightest blue and red supergiants in galaxies of different absolute magnitudes shows trends of M(star) with M(parent galaxy). Red supergiants show a more shallow correlation than the blue stars for galaxies brighter than MB = −14. For fainter galaxies, the red supergiant method appears to become totally degenerate.Four areas of application of the brightest star data are discussed as (1) determining MB of the Eddington limit to be ∼−10 for blue supergiants, (2) calibration of MB(max) = −20.0±0.4 for type I supernovae, leading to a Hubble constant of HO = 43±10 km s−1 Mpc−1, (3) detection of the deceleration of the cosmological expansion by the Local Group leading to a Local Group mass of 4×1011 M⊙ and a mass-to-blue light ratio of 3, and (4) use of the brightest stars to map the Virgo cluster velocity perturbation of the Hubble flow.
Chemistry in the Early Universe
Authors: Dalgarno A. , Lepp S. 
Published: June 2019

The chemical processes which led to the formation of molecules in the early universe are described. Molecular hydrogen is formed by two sequences. in one, radiative attachment to form H− is followed by associative detachment and in the other radiative association to form H2+ is followed by a chemical reaction with H. Trace amounts of HD and the molecular ion LiH+ are formed by the reaction of D+ with H2 and by the radiative association of Li+ and H. The H2 molecular fraction in the expanding universe is about 10−6.Because they are cooling agents, hydrogen molecules are significant in the collapse of pre-galactic clouds. With increasing density the hydrogen gas is converted to molecular hydrogen by three-body recombination and emission from the rotational and vibrational levels cools the cloud and slows the rise in temperature of the gravitationally collapsing object. Ultimately though, the radiation is trapped and the temperature rises. The H2 molecules are then destroyed by collision-induced dissociation. At still higher temperatures collisional ionization occurs, initiated most probably by the process of associative ionization.Molecules may be significant also in galaxy formation if the explosive amplification model is correct. Heavy elements may be present in the shell of gas swept up by the blast waves of the exploded seed galaxies and chemical processes leading to the formation of molecular hydrides may take place, in a scenario analogous to the aftermath of an interstellar dissociative shock.
Low Frequency Cutoffs in the Spectra of Radioquiet Quasars
Authors: Antonucci R. , Barvainis R. 
Published: June 2019

Radio-quiet and normal radio-loud quasars have very similar spectral properties in the ultraviolet, optical and near infrared regions, but their radio powers differ by several orders of magnitude. Somewhere between the near infrared and the radio their spectra must diverge dramatically.The IRAS survey detected 17 radio quiet quasars and luminous Seyfert 1's with −29. 5 ≤ Mv ≤ −21.6 (for Ho = 75). By coadding the survey data and using pointed observations, we have detections of most of these objects in all four IRAS passbands. The spectra are all rising with wavelength all the way to 100μ. We are measuring fluxes in the centimeter, millimeter, and, together with R Cutri, the near infrared and optical regions for each of these objects. Our goal is to constrain the location, shape, and spectral context of the low frequency cutoffs. Here we present the IRAS, millimeter and centimeter data. Measurements at the other wavelengths are still in progress.Although the spectra are rising steeply between 60μ and 100μ, we find that all of our objects are undetectable at 1.3 mm with the NRAO 12-m telescope. Our limits are typically an order of magnitude below the 100μ fluxes. (Ennis et al (1982) and Robson et al (1985) have already shown that the 1 mm fluxes of some radio quiet quasars must be below the extrapolation of the near infrared continuum.) Our objects are all extremely weak or undetected with the VLA at 2 cm and 1.3 cm, at levels typically three orders of magnitude below the 100μ fluxes. The sharpness of the required cutoffs allows us to rule out the hypothesis that the infrared is synchrotron radiation with the cutoff due to an absence of low energy electrons. The high frequency of the cutoffs makes free-free absorption implausible, but not impossible. It is possible that synchrotron self-absorption is suppressing the radio. There is circumstantial evidence that the far infrared is thermal dust emission. This would require a lower cutoff in the distribution of dust temperatures, which we think we can explain.