bluuebunny/crossref_metadata_2025_split huggingface dataset:
The night sky brightness measured from satellites Kosmos 51 and 213
Authors: Dimov N. A. , Severny A. B. , Zvereva A. M. 
Published: July 2016

(1)The minimum measured brightness of the night sky (in the visual region) is about 100 stars of the 10th magnitude per square degree near the galactic poles.(2)The ratio of fluxes in the ultraviolet (2300–3000 Å) and visual regions is approximately in agreement with expected theoretical data based on the models of stellar atmospheres for spectral classes B0 to G5 and on the distribution of stars of the different spectral classes over the sky.(3)The nature of possible deviations (theory minus observation) is discussed.
High altitude interferometer spectra of Mars
Authors: Fink Uwe , Kuiper G. P. 
Published: July 2016

Spectra of Mars were presented which were taken as part of the LPL high altitude program [1] with the NASA CV990 jet. The spectra were taken at about 40 000′ (12 km) altitude. Two sets of five flights each were made around May 1, 1969 and June 1, 1969. In each case the first flight was a Moon comparison flight and the other four were Mars flights, with some Moon if the Moon could be observed.A 12″ telescope received light from a gyroscopically controlled heliostat and directed it into a Block Associates rapid scan interferometer. (For details see Reference [2].) The interferometer had a resolution of 5 cm−1. The present spectra are, however, only reduced for a resolution of 8 cm−1 due to limitations in our computer operations.The spectra taken around June 1 are of better quality since Mars was brighter at that time. The CO2 bands at 1.4 μ, 1.6 μ, 2.0 μ, and 2.7 μ all show up very nicely. The isotopic C13 companion band of 003 as well as the ordinary forbidden isotopic band of O16C12O18 (002) can be detected. No water vapor at 1.4 μ or 1.8 μ remains after taking the ratio with the Moon. Some possible trace remains at 2.7 μ. Quantitative analysis as well as reductions of the interferograms to higher resolution are in progress.
Mariner 1969: results of the infrared radiometer experiment
Authors: Münch G. , Neugebauer G. , Chase S. C. 
Published: July 2016

The energy radiated by Mars in the wavelength bands 8–12 and 18–25 μ has been measured during the flyby of Mariner 1969 with linear resolution of 50 km at closest approach. From the laboratory energy calibrations and assuming unit emissivity, the temperature of the surface materials has been derived. The main results are summarized as follows:(a)The temperatures near the equator (Mariner 6), as function of local time, on the average agree with the values expected on the basis of the gross thermophysical properties of the soil determined from ground-based measurements.(b)The temperature fluctuations around their mean seem to correspond to variations in albedo over the classical features of the planet, with the possible exception of one area.(c)The lowest temperatures measured by channel 2 of Mariner 7, during the polar swath, were 148 K, while at the edge of the polar cap the temperature was 230 K.A small amount of instrumental responsivity to off-axis radiation will change these nominal temperatures slightly, in the general sense that the low temperatures, when properly corrected, will decrease by a few degrees, while the high temperatures will increase by a similar amount.
Mariner 6 and 7 television pictures: Preliminary analysis
Authors: Leighton R. B. , Horowitz N. H. , Murray B. C. , Sharp R. P. , Herriman A. H. , Young A. T. , Smith B. A. , Davies M. E. , Leovy C. B. 
Published: July 2016

Before the space era, Mars was thought to be like the earth; after Mariner 4, Mars seemed to be like the moon; Mariners 6 and 7 have shown Mars to have its own distinctive features, unknown elsewhere within the solar system.The successful flyby of Mariner 4 past Mars in July 1965 opened a new era in the close-range study of planetary surfaces with imaging techniques. In spite of the limited return of data, Mariner 4 established the basic workability of one such technique, which involved use of a vidicon image tube, on-board digitization of the video signal, storage of the data on magnetic tape, transmission to the earth at reduced bit rate by way of a directional antenna, and reconstruction into a picture under computer control. Even though the Mariner 4 pictures covered only about 1% of Mars's area, they contributed significantly to our knowledge of that planet's surface and history [1, 2, 15, 17].
Spectral Analysis of Gamma Rays with the COS-B Satellite
Authors: Van De Hulst H. C. , Scheepmaker A. , Swanenburg B. N. , Mayer-Hasselwander H. A. , Pfeffermann E. , Pinkau K. , Rothermel H. , Schneider H. , Voges W. , Labeyrie J. , Keirle P. , Paul J. , Bellomo G. , Bignami G. , Boella G. , Scarsi L. , Hutchinson G. W. , Pearce A. J. , Ramsden D. , Wills R. D. , Wright P. J. 
Published: July 2016

The ESRO satellite COS-B carries one single experiment aiming at the measurement of arrival direction and energy of celestial gamma rays with energies between 25 MeV and 10 GeV. The experiment is conventional in design and consists of a veto counter, a wire spark chamber, a telescope and an energy calorimeter.The energy measurement is obtained by a CsI scintillation crystal of 4.7 radiation length thickness. The expected energy resolution at 100 MeV is 50% FWHM. The other detector elements are designed as to cause the least possible degradation of the energy measurement.The possibilities for the detection of a small contribution of π -origin gamma rays in the presence of a power-law type background spectrum will be discussed.
X-Ray Spectrometry of Galactic Sources in the Energy Range 30–200 keV
Authors: Bui-Van A , Vedrenne G. , Cezac Y. , Bouigue A. , Sabaud L. 
Published: July 2016

We describe a detection unit for X-rays in the energy range 30-200 keV of high directivity (2° FWHM). This directivity is obtained by the use of a honeycomb collimator and completed by an efficient passive shielding. The angular resolution of the detector necessitates the use of a solar sensor so as to track the sources observed during the balloon flight and to localize them with an accuracy of 3.8 arc min. This experiment was launched with balloon at Aire-sur-L'Adour and Gap (France) and the results obtained must permit the flux limit detected to be reduced.The performances of this detector are analysed as well as their consequences in the study of galactic discrete sources.
Nutation as derived from latitude observations
Authors: Fedorov E. P. 
Published: July 2016

The results of several long series of latitude observations have been used for a separate determination of the coefficients of some nutational terms in obliquity and longitude.The derived value of the constant of nutation is essentially smaller—and those of the coefficients of the semiannual and semimonthly terms larger—than the respective theoretical values, determined on the supposition that the earth as a whole is an elastic body. The theoretical value of the ratio of the axes of the nutational ellipse evidently does not need any correction.On the basis of these data some conclusions of a qualitative character are made on the interaction between the core and the shell of the earth.
Variations périodiques et aléatoires de la rotation de la Terre
Authors: Stoyko Nicolas 
Published: July 2016

Etude de la periode 1952–1958 a montré la stabilité assez grande de la variation saisonnière de la rotation de la Terre par rapport à l'heure definitive. Nous avons trouvé
où j est exprimé en jours moyens à partir du Ier janvier.La comparaison avec le temps terrestre des étalons atomiques de fréquence à césium a permis de trouver que la vitesse moyenne de la rotation de la Terre varie d'une façon aléatoire pendant les trois derniéres années. Pour la période du juin au novembre 1955 la durée du jour diminue (la Terre accélere) de 2 × 10−6 sec. par mois, du decembre 1955 au mai 1957 la durée du jour augmente progressivement (la Terre retarde) en moyenne de 4 × 10−6 sec. par mois et à partir du mai 1957 elle est presque constante.Ainsi, I'extrapolation du temps rotationnel terrestre par rap portau temps atomiques présente des grandes difficultés
Etalons de fréquence
Authors: Decaux B. 
Published: July 2016

De récents progrès ont été obtenus sur les horloges à quartz et les étalons atomique de fréquence.L'amortissement des cristaux a pu être notablement diminué par le choix de tailles spéciales et également par l'emploi de températures voisines du zéro absolu; le vieillissement se trouve en même temps très réduit. L'asservissement d'un oscillateur par un cristal fonctionnant comme résonateur permet d'obtenir une stabilité accrue.Le résonateur à jet atomique de césium a fourni de remarquables résultats dans divers pays, et a permis d'affectuer des comparaisons internationales montrant un accord à quelques 10-10 près. Des mesures régulières sont effectuées par rapport aux déterminations horaires. Un de ces appareils est réalisé sous forme industrielle.Le Maser à jet moléculaire d'ammoniac constitue un générateur de courant. Il a donné lieu à de nombreuses réalisations. Certains de ces étalons sont comparés aux horloges d'observatoires, et par l'intermédiaire de signaux horaires, aux étalons à césium. Certaines différences ont été constatées.Les étalons atomiques de fréquence permettent d'améliorer considérablement la conservation du temps par les horloges à quartz.
On periodic motions of stars within ellipsoidal stellar systems
Authors: Abalakin V. K. 
Published: July 2016

L. PerekThe existence of periodic motions of stars belonging to an ellipsoidal stellar cluster has been proved, the effect of medium resistance being neglected. The density distribution is assumed to depend on the polar semi-axis of the ellipsoidal system, the surfaces of equal density being homothetical ellipsoidal surfaces. By applying Lindstedt–Lyapounov's method of frequency variation the generating solutions have been obtained in an explicit form. Following H. Poincaré's method the first terms of power developments relative to a small parametervhave been found corresponding to several commensurabilities between the mean motion of the star and that of the peri centre of its orbits as well as the angular velocity of rotation of the cluster.
Measuring Subclusters in Galaxy Clusters
Authors: Shao Z.Y. 
Published: July 2016

We assume that there are Kc subclusters and Kf fields (foreground or background) in a cluster region. Then, the distribution of all galaxies in this region can be described as follow:
where, nc and nf are normalized numbers of subcluster members and field galaxies. φc, φf, are their normalized distributions in radial velocity space. Both of them can be assumed as Gaussian. μc and μf are normalized distributions in the projected surface of the celestial sphere. For field galaxies, it's uniform, and for subcluster members, usually we use the King's approximate formulae. Distribution parameters and their uncertainties can be found by using the standard maximum likelihood method. And membership probabilities of the ith galaxy belonging to the cth subcluster can be calculated as Pc(i) = φc(i)/φp(i).
Determination of NGC 4151 Nucleus Mass from Parameters of Narrow Satellites of Broad Lines
Authors: Bochkarev N.G. 
Published: July 2016

The paper considers the possibility of AGN mass estimation from observations of spectral lines emitted by jets. Jets are a typical for AGNs.Similar to SS433 the inner parts of AGN jets may emit spectral lines. 88433 spectra show that jet lines are week in comparison with those of slowly outflowing gas. Consequently the proper time for AGNs jet lines observations is the deep brightness minima (so-called transition from Sy1 type to Sy2 type of spectra). It is possibly the only chance for jet lines observations, because on the Sy1 stage gas surrounding the central object can. be optically thick in the broad lines wings or at least light up the week jet lines. The only well studied case of A(;N transition from Sy1 to Sy2 with evidence of jets is NGC 4151 when this galaxy was in a deep minimum of brightness during the 1984-1987.
ASCA Observations of Narrow Line Seyfert 1 Galaxies
Authors: Hayashida K. 
Published: July 2016

Study of nine Narrow Line Seyfert 1 galaxies (NLS1) observed with ASCA is presented. The X-ray spectra are fitted with a two component model. The soft component can be represented by a blackbody model with kT~100eV. To make the observed luminosity below the Eddignton limit, we have to assume the emission region has a size much smaller than 3Rs. The X-ray variabilities of the NLS1s have systematically shorter time scale than the typical (broad line) Seyferts 1 (BLS1), which suggests lower black hole masses in the NLS1s.We also study the the X-ray spectral structure around 1.1 keV, which has been reported for some NLS1s. Although the structure has been interpreted as an absorption feature, we propose an alternative model employing emission lines. One possible origin of the emission lines is preprocessing from a highly ionized accretion disk.
Star Cluster Encounters in the Magellanic Clouds
Authors: de Oliveria M.R. , Dottori H. , Bica E. 
Published: July 2016

The study of star cluster pairs in the Magellanic Clouds (MCs) has been explored extensively in the past years (Bhatia & Hatzidimitriou 1988; Rodrigues et al. 1994; de Oliveira et al. 1998). The evolution of these pairs can provide fundamental insight into the past history of cluster formation in the MCs.We have selected MC clusters (Bica & Schmitt 1995; Bica et al. 1998) with morphologies resembling those of the present models. The images in this selection of pairs were obtained from the Digital Sky Survey (DSS). We have also performed N-body simulations of star cluster encounters under different initial conditions, with the total number of particles per simulation ranging from 1024 to 20480.
Evolution of Ephemerides Representation and Diffusion
Authors: Seidelmann P.K. 
Published: July 2016

There has been, and continues to be, a close interaction between celestial mechanics used for the generation of ephemerides, mathematical techniques, and computer technology. As the computer capabilities of the ephemerides offices and the users of ephemerides have improved, the methods of determining and the accuracies of ephemerides have changed and the medium and representation of the ephemerides provided to the user have evolved.Ephemerides have been provided in the form of theories, tables, tabulations, polynomials, graphics, and subroutines by means of the printed page, punched cards, magnetic tape, floppy disks, CD/ROMs, and electronic mail. As mathematical techniques and computer technology continue to develop and the requirements for ephemerides evolve, the methods of representing and diffusing ephemerides will continue to improve.
Photographic Sky Surveys
Authors: Reid I.N. 
Published: July 2016

Photographic surveys have played a vital role in virtually every area of astronomical research over the last 50 years. Indeed, one can make a strong case that Schmidt telescopes in general, and the Palomar 48-inch Schmidt in particular, have made the most substantial contribution to our understanding of the Universe—at least at optical wavelengths. The all-sky atlases compiled since the initiation of the POSS I O/E survey in 1949 will continue to provide fundamental reference catalogues and potent research tools for many years to come (for our children's children's children), particularly when combined with the second epoch surveys currently under way. However, as far as undertaking new, large-scale sky surveys are concerned, it is clear that we have reached the end of an era. Alternative detector technology and new instrumentation (i.e., CCD mosaics) can now match and, indeed, exceed the capabilities of the photographic Schmidt telescopes in undertaking effective wide-field photometric surveys.In this review, I report on the progress being made in completing the all-hemisphere photographic surveys currently being undertaken from Siding Spring with the UK Schmidt and from Palomar with the Oschin Schmidt. I also provide a summary of the availability of machine scans and/or object catalogues derived from the various surveys. Photographic survey work is not confined to these atlases, however, and section 3 provides discussion of other more specialised projects currently being undertaken. Finally, I consider the future possibilities for photographic Schmidt surveys.
Prospects for Future Astrometric Missions
Authors: Seidelmann P.K. 
Published: July 2016

Hipparcos and the Hubble Space Telescope have demonstrated the astrometric capabilities in space. SIM and GAIA are being studied for future missions. There have been many proposals for new astrometry missions from many different countries, but most of them have not been funded.The best possibility for a mission within the next five years would be through a collaborative effort for a small, fast, cheap spacecraft which could be a precursor for future, larger, more accurate missions, which are under study.
Luminosity Density Evolution in the Universe and Cosmological Parameters
Authors: Totani Tomonori 
Published: July 2016

Star formation history in galaxies is strongly correlated to their present-day colors and the Hubble sequence can be considered as a sequence of different star formation history. Therefore we can model the cosmic star formation history based on the colors of local galaxies, and comparison to direct observations of luminosity density evolution at high redshift gives a new test for the cosmological parameters which is insensitive to merger history of galaxies. The luminosity density evolution in 0 < z < 1 observed by the Canada-France Redshift Survey in three wavebands of 2800Å, 4400Å, and 1μm indicates that the Λ-dominated flat universe with λ0 ∼ 0.8 (> 0.53 at 95%CL) is strongly favored.The cosmic star formation rate (SFR) at z > 2 is also compared to the latest data of the Hubble Deep Field including new data which were not incorporated in the previous work of Totani, Yoshii, & Sato (1997), and our model of the luminosity density of spiral galaxies taking account of gas infall is consistent with the observations. Starbursts in elliptical galaxies, which are expected from the galactic wind model, however overproduce SFRs and hence they should be formed at z ≳ 5 or their UV emission has to be hidden by dust extinction. The amount of metals in galactic winds and escaping ionizing photons are enough to contaminate the Lyα forests or to reionize the universe.
Spectroscopic Distances to Central Stars of Planetary Nebulae
Authors: Méndez R. H. , Kudritzki R. P. , Herrero A. , Husfeld D. , Groth H. G. 
Published: July 2016

We present spectroscopic distances for 22 central stars of planetary nebulae. These distances have been determined using information provided by our non-LTE model atmosphere analyses of the stellar H and He absorption line profiles. In this way, no assumptions about nebular properties are necessary.Our spectroscopic distances turn out to be larger than many other frequently cited values. We show that our distances are not in contradiction with the available information about the interstellar extinction, and we describe additional evidence supporting them.
Magnesium Abundances in Planetary Nebulae and Interstellar Absorption of Mg II λ2800 A
Authors: Middlemass D. 
Published: July 2016

SummaryHigh-resolution IUE images have provided line profiles of emission cut by interstellar absorption in the magnesium II lines λλ2795, 2802 A in nine objects. The underlying emission has been reconstructed in seven of these by fitting Gaussian profiles to the remaining line wings. Estimates of the ratio of intrinsic to observed emission ranging from 1.5 to 23 have been obtained. Photo-ionization models of IC 418, IC 4997 and NGC 2440 have been used to obtain Mg/H ratios from the corrected Mg II line strengths. The logarithmic magnesium abundances obtained were 7.6±0.12, 6.96±0.3 and 6.5±0.3 respectively. These results indicate that depletion of Mg into grains is less than previously thought and reduce the observed gradient in the magnesium abundance. The Mg depletion may be related to the C/O ratio within the nebula; carbon-rich planetary nebulae may have less magnesium depletion than those with C/0 < 1.
The Central Star of NGC 7027
Authors: Walton N.A. , Pottasch S.R. , Reay N. K. , Spoelstra T. 
Published: July 2016

We have detected the central star of NGC 7027 by imaging the nebula through a narrow band ‘continuum’ filter onto the IPCS detector at the 2.5m Isaac Newton Telscope. We obtain an apparent visual magnitude for the central star of mv = 17.7 ± 0.5 mags.Assuming that the central star radiates approximately as a blackbody, which is reasonable for the case of a hot star, then Zanstra temperatures for the central star can be calculated. We find TZ(H) = 3.9 × 105K and Tz(HeII) = 2.6 × 105K. Using the correction due to Stasinska & Tylenda (1986) we estimate the central star of NGC 7027 to have a temperature, Teff = 3.1 × 105K.The luminosity and radii are found assuming a distance of d=1.2 kpc., giving L = 12,600 L⊙ and R = 0.039 R⊙. Placing the central star on the Log L - Log T diagram and comparing with evolutionary tracks for central stars with various masses from Wood & Faulkner (1986), indicates that the central star of NGC 7027 must have a mass, M ≥ 0.8 M⊙.Radio observations of NGC 7027 have been taken using the Westerbork Radio Synthesis Telesocpe at 21cm. Self calibration techniques have been employed to give a radio continuum map of high dynamic range. These observations are being compared with a deep optical Hβ map to study the nature of the faint halo seen around NGC 7027 (Atherton et al. 1979)
Cosmic Distribution of Optically Selected Quasars
Authors: Schmidt Maarten 
Published: July 2016

Counts of optically selected quasars as a function of magnitude and redshift show the effects of strong evolution. If quasars have relatively short life times, then the observed numbers at a given redshift are mostly determined by their birth rate and mean luminosity over their lifetime. In this case the evolution of the luminosity function can be described by density evolution, where the rate of evolution may depend on luminosity and other properties. On the other hand, if all quasars were formed at large redshift and have been decaying in luminosity since that time, then the evolution of the luminosity function is best described in terms of luminosity evolution. We discuss some of the consequences of luminosity evolution for the mass of quasars and for the X-ray background.We explore the observational aspects of the redshift cutoff of quasars. The situation is complicated by the unavoidable bias in slitless surveys against weak-line objects. Since quasar emission lines show a wide range of equivalent widths, a spectral survey will be characterized by a distribution of limiting continuum magnitudes rather than by a single value. The decline in the space density of quasars at large redshift may depend on luminosity, and may also have structure, such as a steep drop, but not a total cutoff, in density at a redshift near 3.
Particle Acceleration in Solar Flares and Coronal Mass Ejections
Authors: Lin R. P. 
Published: July 2016

The Sun accelerates ions up to tens of GeV and electrons up to 100s of MeV in solar flares and coronal mass ejections. The energy in the accelerated tens-of-keV electrons and possibly ~1 MeV ions constitutes a significant fraction of the total energy released in a flare, implying that the particle acceleration and flare energy release mechanisms are intimately related. The total rate of energy release in transients from flares down to microflares/nanoflares may be significant for heating the active solar corona.Shock waves driven by fast CMEs appear to accelerate the high-energy particles in large solar energetic particle events detected at 1 AU. Smaller SEP events are dominated by ~1 to tens-of-keV electrons, with low fluxes of up to a few MeV/nucleon ions, typically enriched in3He. The acceleration in gamma-ray flares appears to resemble that in these small electron-3He SEP events.