bluuebunny/crossref_metadata_2025_split huggingface dataset:
CCD Photometry — Present and Future
Authors: Walker Alistair R. 
Published: June 2019

I will briefly treat some of the developments relating to CCD photometry which have taken place over the last two to three years, and speculate on those which can be anticipated to take place in the near future. CCDs have been in widespread use as astronomical detectors for slightly more than a decade. For the majority of visual-light projects they have displaced the photographic plate and the photomultiplier as the detector-of-choice, except in applications requiring large area coverage or high time resolution, but even here the development of arrays and the use of more sophisticated electronics has permitted encroachment into these domains. The use of large, low-noise detectors for CCD photometry places stringent demands on telescope optics, instruments, controllers, calibration procedures, data reduction methods and data storage, and forces a holistic approach to managing the data flow from detector to final storage medium.For an earlier review on this field see Walker (1993); other papers presented at IAU Colloquium No. 136 and IAU Symposium 167 (these proceedings) should be consulted for different topics, alternative viewpoints, and more in-depth discussions of specific subjects.
Astrometric Characteristics of the Abastumani Astrophysical Observatory 125 cm Reflector (AZT-11) of Ritchey-Cretien Optical System
Authors: Salukvadze G. N. 
Published: June 2019

Quite a number of instances are known when Schmidt, mirror-lens system telescopes and generally reflectors are used for solving the problems of photographic astrometry.This paper describes the use of the Ritchey-Cretien telescope (AZT-11) at the Abastumani Astrophysical Observatory for determining relative positions of the members of multiple systems.
Impersonal Techniques of Transit Circle Observations. “The Carlsberg Automatic Meridian Circle”
Authors: Helmer L. 
Published: June 2019

The conventionel reversible meridian circle of Copenhagen University, has over the last years been fully automated, and equipped with a new photoelectrical transit micrometer and a revised photoelectric circle recording system. Setting, observation and data recording is completely controlled by two minicomputers, therefore the presence of an observer is needed only for emergency situations, and for the reduction procedure. The telescope has been succesfully tested over a two year period in Brorfelde, resulting in two published catalogues with mean errors similar to those previously obtained with the photographic micrometer. The magnitudes were also measured and the limiting magnitude in Brorfelde was mv = 12.In the autumn of 1983 the telescope was moved to the Canarian island La Palma, where it is currently being installed.
The Seven-Inch Transit Circle and its New Zealand Program
Authors: Hughes J. A. , Robinson M. D. , Gauss F. S. , Stone R. C. 
Published: June 2019

The modernization of the seven-inch transit circle is an important aspect of the envisioned Naval Observatory observing effort. This task has been carried out on the basis of the following desiderata:1) The basic sensor should be photoelectric2) Point sources observable at night down to at least m=103) Venus, Mercury and stars down to m=4 observable in the daytime4) Mars, Jupiter, Saturn, Uranus, Neptune and the Moon observable5) The Sun must be observable6) The instrumental parameters: azimuth, level, collimation, nadir, and so on must be determined so as to allow absolute observations7) The system should operate essentially autonomously, but an observer should be kept in the observing “loop”.It appears that all of these objectives have been achieved by the system now to be briefly described.
Spatial Structures of a Complete Sample of Extragalactic Radio Sources North of Declination 70°
Authors: Eckart A. , Witzel A. 
Published: June 2019

With the aim of studying the spatial structures of a complete sample
of radio sources found at 6 cm wavelength we selected 13 sources from the
“S5–survey” (Kühr et al., 1981) which fulfil the following criteria1) δ > 70°, |bII| > 10°2) S5 GHz > 1 Jy (at the epoch of the S5–survey)3) α5 GHz2.7 GHz > − 1.5 (S ∝ να)6 of these sources are identified by means of optical spectroscopy with QSOs, 6 are BL Lac-type objects, and the identification of 1 source is presently unknown. Observations at frequencies ranging from radio to X-ray have been reported (Biermann et al., 1981; Biermann et al., 1982; Eckart et al., 1982).
Standard Astronomical Sources for the Space Telescope
Authors: Bohlin Ralph C. 
Published: June 2019

The Space Telescope (ST) will require many types of standard sources for a diverse range of calibrations to be performed after launch. The scientific instruments are sensitive to a wide range of wavelengths from 1050 to 11,000Å and encompass a broad range of measurement capabilities including astrometry, photometry, imaging, polarimetry, and spectroscopy. To verify proper operations of each instrument and to provide quantitative calibrations, a diverse range of standard sources and fields are required. In order to select targets that satisfy the requirements of the Instrument Definition Teams and the long term responsibilities of the Science Institute, six groups containing a total of 25 astronomers are defining the calibration targets to be observed after launch. The six categories of ST standard sources are:
1)Ultraviolet Spectrophotometric2)Ground Based Spectrophotometric and Photometric3)Wavelength4)Astrometric5)Polarimetric6)Spatially Flat FieldThe data in these categories will be collected from the literature or through new observing programs as appropriate. These six reports of the working groups outline the calibrations and proposed targets for all of the scientific instruments on ST. The collected data on each set of standard sources should be published in the refereed literature.
Are Bipolar Jets Precessing?
Authors: Fukue Jun , Yokoo Takeo 
Published: June 2019

No one has drawn attention as to whether bipolar jets precess or not. We examine here the possibility of precession of bipolar jets from a theoretical point of view (Fukue and Yokoo 1986).We first characterize various models proposed for bipolar jets in the light of precession. That is, can they admit precession? If they can, how long is a precessional period P?
Improving the dynamical reference frame through minor planet orbit correction using crossing point observations
Authors: Whipple Arthur L. , Duncombe Raynor L. , Hemenway Paul D. 
Published: June 2019

We have begun a program to establish a dynamical reference frame based on the motions of minor planets. The program will utilize observations from the Hubble Space Telescope, and will ultimately tie the HIPPARCOS reference system to a dynamical base. Thirty-four minor planets, 20 of which are suitable for observation with the Hubble Space Telescope, have been selected. Ground based observations, particularly crossing-point observations with long focus reflectors, have been initiated.A computer program to simultaneously solve for the corrections of the orbits of the 34 minor planets including the crossing-point observations, was successfully run. The observations are treated by the method of W. H. Jeffreys. Using simulated data, solutions with and without crossing point observations demonstrate the value of those observations to produce a homogeneous and coherent set of results.
Vers Un Nouveau Catalogue General Astrolabes
Authors: Chollet F. 
Published: June 2019

In the context of the future Hipparcos astrometric satellite which will give a high precision catalogue, the ground based astrometry will have new possibilities of research, particularly in the field of the stellar and the dynamical reference systems. The modern astrolabes should give, as new photoelectric meridian circles, an important contribution.Since 1956, the Danjon astrolabe was used to determine the Earth rotation parameters. Very rapidly it was demonstrated (S. Débarbat, J. Kovalevsky, 1963) that this instrument was able to give very good planetary positions, relatively to the FK4. New studies shown, later, that it was also possible to observe the Sun (F. Laclare 1975, N. Leister 1979, F. Chollet 1981). The major contribution of the astrolabe was the observation of stellar catalogues (Billaud 1978) and now, the determination of the variations of the solar diameter.In these conditions, it is now possible to use polyvalent astrolabes, able to give good positions of stars, planets and Sun. The Hipparcos catalogue, connected to the extragalactic reference system by VLBI, will constitute a very precise “interpolation system”. The main problem will be to save this high precision during a long time. Without other Hipparcos satellite or other method, this problem can be solved only by the ground based astrometric observations. At the same time, some other fields of research can be initiated if the astrometric observations are directly connected to Hipparcos catalogue, such as the local effects, the refraction, the motions of the vertical, which will improve in the future the ground based astrometric results.Concerning the astrolabes, some studies are made in France to improve the instrument and the methods of reduction. At the same time, the astrolabe community has to use the same procedures of observation and reduction to be able to connect the results coming from several different stations.
A Statistical Study of the Correlation Between Galactic SNRS and Spiral Arms
Authors: Li Z.W. , Wheeler J.C. , Bash F.N. 
Published: June 2019

Based on the statistical studies of external galaxies, our Galaxy is expected to produce Type I and Type II supernovae in closely equal number. There are as of this writing 162 known galactic SNRs.The basis for our investigation is the observations that SN II are tightly correlated with spiral galaxies and that SN I do not correlate with spiral arms, but are roughly of old disk population.We seek a method by which a correlation of SNR with spiral arms can be determined. For this preliminary exercise we use only information on the positions of the SNR in galactic coordinates.As a test, we compared the angular distribution of SNR and giant HII regions which are presumed to define the location of the spiral arms. To the eye, there did seem to have a correlation.We thus faced a host of questions.Do SN I still occur in spiral arms, implying that they have massive progenitors?Is the rate of formation of SN I in Galaxy (and M31) considerably less than that of SN II?Do SN I not produce long lived radio SNRs?We have developed a quantitative approach to investigate these questions. Using the observed angular distributions of SNRs and giant HII region, we form a cumulative distribution with respect to angle. Two observed distributions can be compared then, and the Kolmogrov-Smirnov statistics was used to determine the probability that the two samples are not drawn from the same distribution.In addition, we have constructed Monte-Carlo models in which sample objects are distributed in a prescribed pattern in the spiral arms and the galactic disk. The parameters of the Monte-Carlo simulation, such as the opening angle of the spiral arms and the fraction of objects in the disk vs arm population, can be adjusted to obtain the best fit to the observed distribution.We also study the influence of the selection effects, if the surface brightness of SNR falls below a threshold for detectability (as 1/r2).
Astrometry with the HST Fine Guidance Sensors
Authors: Lattanzi M. G. , Bucciarelli B. , Holfeltz S. T. , Taff L. G. 
Published: June 2019

This paper presents an overview of the current status of astrometry with the Fine Guidance Sensors (FGSs) on the Hubble Space Telescope. The FGSs have two astrometric modes of operation, one for positional (POS) and one for transfer function (TRANS) astrometry. The positional mode is intended for parallax and angular velocity work. Owing to optical aberrations in the Optical Telescope Assembly (OTA) (i.e., the main telescope optics) beyond the spherical aberration, and instabilities within the combined OTA/FGS optical system, it is undergoing additional feasibility review. Preliminary engineering tests showed changes in stellar pair positions of ∼ 100 milli-arc seconds which are far too large to allow for the expected ∼ 1 mas calibration. Alternate calibration procedures and data reduction algorithms are currently being developed to maximize the scientific potential of this mode which can be fulfilled at the ∼ 3 mas level.The other operational mode-primarily intended for work on double stars but also usable for angular diameter determination-has proven more stable. Even the deleterious effects of the thermally induced solar array jitter have mostly been overcome. A large collection of reduction and analysis software is available to support this measurement technique (Lattanzi, Bucciarelli, Holfeltz, and Taff 1992) and its calibration is proceeding apace. Interesting scientific work from the FGSs on bright Hyades binaries and the highly eccentric double star ADS 11300 has already been published (Franz et al. 1991, 1992).Finally, a new FGS Instrument Handbook (Taff 1992a) has been prepared which should minimize the complications of dealing with the General Observer Proposal Forms.
The Third Catalogue of Nearby Stars — Results and Conclusions
Authors: Jahreiß Hartmut , Gliese Wilhelm 
Published: June 2019

The nearby stars constitute the statistically most complete and therefore most representative sample of stars in our Galaxy. Only this sample allows a direct investigation of luminosity function and kinematics of low-mass stars.A study of the Third Catalogue of Nearby Stars reveals a considerable increase — not only in quantity but also in quality — in our knowledge of the immediate solar neighbourhood, and reflects very nicely the progress achieved during the last decades — especially in astrometry and photometry. Expectations for the near future (HIPPARCOS) and desiderata for further astrometric and photometric work will be discussed.
Sub-luminous blue stars and white dwarfs
Authors: Greenstein Jesse L. 
Published: June 2019

Sub-luminous stars of high temperature show a wide variety of spectra and physical properties. Vorontsov-Velyaminov has called this region of the HR diagram the “blue-white sequence”. I wish to discuss the fainter members of this class. The growth of knowledge of colors and spectra has been rapid compared to that of the luminosities, and unfortunately only rough location in the HR diagram is yet possible. Figure 1 shows the general location and subdivision of sub-luminous stars. I shall discuss:
(1)Old novae.(2)Horizontal-branch stars.(3)Hot subdwarfs.(4)White dwarfs.
Commissioning the Very Small Array
Authors: Rusholme Ben. 
Published: June 2019

The Very Small Array (VSA) is a fourteen-element interferometer for sensitive measurement of the CMB anisotropies on scales of three degrees to ten arcminutes. The telescope is now observing on site in Tenerife after a period of commissioning, including the first map of the Sunyaev-Zel'dovich effect in the Coma cluster.A distinguishing feature of the instrument is that each antenna in the array tracks quasi-independently, providing a characteristic fringe rate per baseline which can be used to reject many systematics. This effect has been optimised in the antenna array design.
Improvement of Star Positions by a New Axial Meridian Circle with Negligible Systematic Errors
Authors: Pinigin G.I. , Shulga A.V. , Fedorov P.N. , Kovalchuk A.N. , Mazhaev A.E. , Petrov A.G. , Protsyuk Yu.I. 
Published: June 2019

The Mykolayiv axial meridian circle (AMC) consists of a horisontal telescope with a pentagon prism of ‘CITALL’ in front of the objective of D=180mm and F=2480mm in the meridian, and a fixed aligned vacuum collimator of D=180mm and F=12360mm.Investigations of the AMC parameters show that: horizontal flexure is negligible and about −0.037″; collimation is stable and can be described by the formula C = C′ + a · t, where t[C] is the temperature, a = 0.026″ and C′ const. The variation of collimator inclination is of the order 0.09″ per 1°C Test observations of FK5 stars show variations of the AMC intrumental system of not more than 0.1″.A CCD micrometer is being developed. Test observations with a pilot micrometer with a CCD of 288 × 256 pixels have started. It appears that the AMC magnitude limit (with cooling) will be about 14 and the positional accuracy 0.1 arcsec.Finally, the expected capabilities of the fully automatic Mykolayiv AMC permit its efficient use for extention of the stellar reference frame to fainter magnitudes, for linking the optical/radio reference frames. In particular, for future observations a programme of 12–14m reference stars around extragalactic radio sources is being prepared.
Astrometric Plate Reduction with Orthogonal Functions and Milliarcseconds Accuracy in Deep Proper Motion Surveys
Authors: Ojha Devendra , Bienaymé Olivier 
Published: June 2019

We have been doing a sample survey in UBV photometry and proper motions as part of an investigation of galactic structure and evolution. The 3 fields in the direction of galactic anticentre (l = 167°, b = 47°), centre (l = 3°, b = 47°) and antirotation (l = 278°, b = 47°) have been surveyed. The high astrometric quality of the MAMA machine (CAI, Paris) gives access to micronic accuracy (leading to < 2 mas per year) on proper motions with a 35 years time base. The kinematical distribution of F and G–type stars have been probed to distances up to 2.5 kpc above the galactic plane. We have derived the constrain on the structural parameters of the thin and thick disk components of the Galaxy (Ojha et al. 1994abc):
• The scale lengths of the thin and thick disks are found to be 2.6±0.1 and 3.3±0.5 kpc, respectively. The density laws for stars with 3.5≤MV≤5 as a function of distance above the plane follow a single exponential with scale height of ∼ 260 pc (thin disk) and a second exponential with scale height of ∼ 800 pc (thick disk) with a local normalization of 5–6% of the disk.• The thin disk population was found with (〈 U+W〉, 〈V〉) = (1±4, −14±2) km/s and velocity dispersions (σU+W, σV) = (35±2, 30±1) km/s. The thick disk population was found to have a rotational velocity of Vrot = 177 km/s and velocity dispersions (σU, σV, σW) = (67,51,42) km/s. No dependence with r and z distances was found in the asymmetric drift measurements of the thick disk population.
Confor Program: Determination of Relative Orientation Parameters Between VLBI and FK5 Reference Frames
Authors: Kumkova Li , Tel'nyuk-Adamchuk V.V. , Babenko Yu.G. , Vertypolokh O. Ya. 
Published: June 2019

The primary goal of the CONFOR Program (CONnection of Frames in Optics and Radio) is to study the connection between VLBI and traditional optical reference frames as well as to study regional features of the FK5 (Gubanov, Kumkova & Tel'nyuk-Adamchuk, 1990). The main concept of this program is the usage of fixed systems of reference stars in field containing the extragalactic radio sources (ERS) and as a result the creation of a reliable base for astrometric reduction of photographic plates with ERS images. Fulfillment of the Program is embracing several stages.1. Star lists have been prepared of 2575 both intermediate reference stars and radio stars for meridian observations and about 7 thousand stars of 12-14 mag. for astrographic observations in 238 fields with extragalactic compact radio sources.2. Observations have been organized of these stars with meridian circles and astrographs in several Eastern observatories (Kyiv, Odesa, Bucharest, Mykolaiv, Kharkiv). The meridian observations are finished in Kyiv and Odesa. Positions of radio stars were determined from Kyiv meridian observations (two epochs: 1984 and 1990).3. Databases of both the optical and radio interferometric observations have been compiled of radio stars, ERS as well as optical observations of intermediate stars in the fields centered in ERS.4. Observations were carried out with several astrographs (Kyiv, Bucharest, Abastumany, Tautenburg, Kitab, Sanglok) and positions were determined of 57 ERS.5. Determination was carried out of the angles of relative orientation between VLBI and FK5 reference frames as well as estimation of regional features of the FK5. For this purpose both collected and original radio source coordinates were used.This work was supported by grant of Academy of Sciences of former Soviet Union and ISF grant U52000.
Scalar Waves in the Exterior of a Schwarzschild Black Hole
Authors: Persides S. 
Published: June 2019

Fourier and Laplace transforms are used to study rigorously the properties of a test scalar field PS in the exterior of a Schwarzschild black hole of the mass m. In the Fourier analysis we examine the properties of the solutions of the radial wave equation and the relations of the exterior and interior solutions of the following four cases: (i) ω ≠ 0, m≠0, (ii) ω=0, m≠0, (iii) ω≠0, m=0, (iv) ω=0, m=0.In the Laplace analysis we show rigorously the following theorem: If ψ(t, r, τ, ϕ) is the field of a point test particle falling into the black hole,
and lim Ψ exists, then lim Ψ = 0. The proof of this theorem is based on the facts that (a)t+2m ln (r − 2m) is finite for the particle even on the horizon, and (b) the behavior of Ψ as t → + ∞ is related to its Laplace transform near the origin of the complex plane.
The Microwave Background Radiation
Authors: De Zotti G. , Danese L. , Toffolatti L. , Franceschini A. 
Published: June 2019

We review the data on the spectrum and isotropy of the microwave background radiation and the astrophysical processes that may produce spectral distortions and anisotropies. As yet no fully satisfactory explanation has been found for the submillimeter excess observed by Matsumotoet al.(1988). The most precise data at λ > 1 mm disagree with nonrelativistic comptonization models which match the excess. Distortions produced by a very hot intergalactic medium yielding the X-ray background do not fit the submillimeter data. Very special requirements must be met for the interpretation in terms of high-redshift dust emission to work.Reported anisotropies on scales of several degrees and of tens of arcsec may be produced, at least in part, by discrete sources. Because the best experiments at cm wavelengths are close to the confusion limit, they provide interesting information on the large-scale distribution of radio sources.
The Distribution of Separations of DMSA Hipparcos Catalogue
Authors: Ling J.F. , Magdalena P. , Prieto C. 
Published: June 2019

AbstractWe have constructed volume-limited samples of wide binaries in the Hipparcos Catalogue Double and Multiple Systems Annex (DMSA, Section C), out to distances of 100 pc and 200 pc. We study the distribution of linear separations for these samples of binaries. We find that they closely follow Öpik’s distribution in the interval of separations between about 10 and 800 AU (for the 100 pc sample), and between 15 and 1400 AU (for the 200 pc sample)
Molecular Gas Kinematics and High-Mass Star Formation in the Spiral Arms of the Milky Way
Authors: Luna A. , Carrasco L. , Ortega L. , Bronfman L. , Yam O. 
Published: June 2019

AbstractWe study the kinematic of the molecular gas using observations of the rotational line 12CO(J=1→0), and also the star formation traced by Ultra-Compact HII regions in the IV galactic quadrant (270° ≤ l ≤ 360°). Our results show that there is a connection between 1) high-mass star formation in the spiral arms of the Milky Way, 2) molecular gas of high column density, and 3) the large-scale rigid-body-like motion of the gas. The large-scale rigid-body-like motions observed in the arms imply that there is less angular momentum to dissipate in the formation processes of stellar systems. We show a multiple stellar system under study, embedded in its parent molecular cloud in the Carina arm region.