bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Dynamics of Meteoroid Streams
Authors: Wiliams I. P. 
Published: June 2019

Meteor showers are seen at regular and frequent intervals on Earth. They are caused by meteoroids (that is small dust grains) in a coherent stream, all moving on similar heliocentric orbits, burning up on encountering the atmosphere of the Earth. Such streams contain 1012 or more meteoroids, with the mass of the visible meteoroids ranging up to about 1 g. The main evolutionary effect on such streams is gravitational perturbations by the planets. Though grain-grain collision may be catastrophic for the two grains involved, it has no effect on the remainder of the stream, other than the fact that there are now two less grains in it. Solar radiation has some effect, but this can be included in the equations of motion. Because of the large numbers of particles involved, meteoroid streams represent a laboratory where many of our dynamical concepts can be tested.At a basic level, meteoroid streams represent a collective dynamical phenomenon in which all members display roughly the same behavior. One of the fundamental questions which can be investigated is whether the behavior of the mean orbit of the whole stream represents the mean behavior of the stream members. Within the boundaries of some meteor streams lie regions where the orbits are in high order resonance with Jupiter. This also represents a phenomenon of interest. Finally, the possibility exists that some streams are in chaotic regions and it is interesting to investigate whether or not meteoroids in such regions do display chaotic behavior.
Populations in the z=0.23 Rich Cluster Abell 2390
Authors: Hutchings J.B. , Abraham R. , Smecker-Hane T. , Morris S. , Davidge T. , Rigler M. , Carlberg R. , Yee H. , Ellingson E. 
Published: June 2019

We have spectra, colours and morphologies from the CFHT for 240 cluster members and 80 field galaxies over a 7 × 46 arcmin field. The cluster galaxies show strong radial gradients in colour, morphology, and spectrum. The central group has only red early-type galaxies of high central concentration, which must have formed at least 5 Gy ago. The population becomes bluer and shows an increasing fraction of disk morphology and recent star-formation with clustocentric radius, and eventually blends into the field. However, the fraction of blue galaxies is significantly lower than in Butcher-Oemler clusters, and there are only two starburst galaxies (one of which is the cluster cD). Fitting of line measures with stellar population models indicates that star-formation has been truncated in the 15-20% of the cluster galaxies that have strong Hδ absorption, and that these galaxies are not all blue. There is evidence that cluster galaxies are dusty compared with the field. The morphology gradient can be fit with models of disk fading. However, there is a small fraction of interacting and merging galaxies, which must play a part in the population evolution. The cluster is accreting from the field in a non-violent way, including some distinct subgroups. This is different from what is seen at both higher and lower redshift, and if generally true, suggests a high Omega universe.These results are being published in detail elsewhere.
Forecasting short-term changes in the Earth's rotation
Authors: Hide Raymond 
Published: June 2019

Summary of PosterIt has long been appreciated that atmospheric motions must contribute to the excitation of fluctuations in the Earth's rotation (Munk and MacDonald 1960, Lambeck 1980, Rochester 1984) but the exploitation of modern meteorological data, collected largely to meet the demands of daily global weather forecasting, in the routine evaluation of angular momentum exchange between the atmosphere and the solid Earth was not initiated until comparatively recently (Hide et al. 1980). This procedure constitutes a necessary step towards the accurate separation of these features of the observed non-tidal changes in the length of day and polar motion and that are of meteorological origin from those that must be attributed to other geophysical processes, such as angular momentum transfer between the solid Earth and other fluid regions of the Earth (liquid metallic core, oceans, etc.), and to changes in the inertia tensor of the solid Earth associated with earthquakes, melting of ice, etc.
A new research for the secular polar motion in this century
Authors: Ming Zhao , Danan Dong 
Published: June 2019

A new research for the secular drift of the Earth's pole was made based on nine long sequences of latitude observations and led to the following conclusions.
1.During this century, the Earth's pole has been moving with a mean rate of about 0″.0016/yr along the meridian about 70° (W). This drift rate is much less than the 0″.0035/yr derived from the ILS sequence.2.Relative to the North American continent, the Ukiah station located on the west coast of the U.S. shows a local drift of about 6 cm/yr northward, which coincides well with that determined by new techniques.3.Referring to the Europe-Asia plate, the whole North American continent shows a drift northward with a rate of about 8 cm/yr. The Mediterranian shows a similar drift of about 6 cm/yr. Perhaps these drifts are the consequences of plate motion and/or deflection of local vertical. It is useful for ascertaining the sources of the drifts to intercompare longer sequences observed with different techniques, including classical and new ones.4.Three of five ILS stations, Ukiah, Gaithersburg, and Carloforte, show significant local drifts. Therefore, the Conventional International Origin (CIO), which is defined by the 1903.0 mean latitudes of five ILS stations, is far from fixed on the Earth's surface. It is necessary to re-define an origin of the pole of the Conventional Terrestrial System (CTS).5.The quasi-30-year libration showed by the ILS data is not the real pattern of the Earth's polar motion, but results from both the irregular polar motion over some period and the local motion of Ukiah.
The Structure of Umbral Fluxtubes
Authors: Degenhardt D , Lites B. W. 
Published: June 2019

Subsurface filamentation of sunspot magnetic fields has been postulated as a source of the visible small-scale structure of sunspot umbrae. We examine this possibility by investigating the magnetohydrodynamic structure of thin, vertical magnetized gas columns embedded in sunspot umbrae. These umbral fluxtubes are assumed to have weaker field strengths than the surrounding umbral atmosphere. The steady-state magnetohydrodynamic equations are solved numerically in the slender fluxtube approximation, thus allowing for stationary internal mass flows. We include the radiative exchange of heat between the umbral fluxtube and the ambient medium using a simple relaxation time approach.The geometric shape of the steady flow solution is a gas column converging with height. We discuss the relationship of our results to observed properties of umbral brightenings (umbral dots). We show that, even if there is a large difference in magnetic field strength between the dot and the ambient medium in deeper layers, the field strengths are nearly equal in the observable layers, a result required by the observations. We also show that either high temperatures at the lower boundary of the dots or strong upflows are needed in order to produce bright continuum structures.
Status Of Photographic Catalogs: Available Material And Future Developments
Authors: de Vegt Chr. 
Published: June 2019

Starting with the Astrographic Catalogue as the first example of an all sky coordinated international astrometric project, a considerable number of large photographic catalog projects has been accomplished in the last decades on both hemispheres. The accuracy properties and possible improvements of some catalogs by remeasurement, application of modern reduction techniques and the use of improved reference star catalogs will be discussed.The optimal use of modern photographic technology and instrumentation for the construction of new global catalogs, capable of positional accuracies on the level of a few 0.01 arcsec, will be outlined with special view to an extension to fainter limiting magnitudes.
A Very Special Catalogue: The Hipparcos Input Catalogue
Authors: Turon C. 
Published: June 2019

The various characteristics of the HIPPARCOS Input Catalogue are described:–How to select 110 000 stars for HIPPARCOS observation from the 210 000 proposed stars, taking into account the following sometimes conflicting requirements : satisfy a maximum of scientific programmes and respect the observational constraints inherent in the HIPPARCOS satellite operation ?–What are the present results regarding the principal astrometric programmes ?–How to process the specific problems which are raised by the HIPPARCOS observation of double and multiple stars and of stars in dense areas ?–Which compilations and observations have been undertaken and are in progress within the frame of the Input Catalogue preparation ? What will be the quality of the final data ?Finally, the contents of the catalogues and annexes that will be published are briefly presented.
Evidence of a circumstellar dust cloudlet orbiting around the central star of NGC 2346
Authors: Costero R. , Tapia M. , Echevarría J. , Quintero A. , Barrai J.F. , Roth M. 
Published: June 2019

The photometric behaviour of AGK3-0°965, the central star of the bipolar planetary nebula NGC 2346, has been monitored photometrically for several months at the Observatorio Astronómico Nacional at Tonantzintla and San Pedro Mértir, Mexico. A model is proposed in which the eclipses were caused by the passage of an elongated cool dust cloudlet of size ~ 2–5 × 1012 cm and total mass ~ 10−12 M⊙. This model can explain most of the observations. The velocity of the cloud in the direction of the major axis of the projected central binary orbit is vp = 0.14 km s−1. Another warmer (T ≲ 1000 K) circumstellar cloud is responsible for the infrared excess at wavelengths from 3 to 12 μm. Its emission, as seen from the Earth, has not changed significantly at λ > 3 μm during the past twelve years, as shown by new infrared observations also reported. Its most relevant physical properties are still to be determined. The present results provide the first evidence of a dense circumstellar cloudlet of mass similar to that of a minor planet which is probably the result of the fragmentation of a disk or toroid around the central star of NGC 2346. Although the presence of many other similar cloudlets in its vicinity is expected, the probability of similar events occurring in the next few hundred years is very small.The details of the present work will be published in the Revista Mexicana de Astronomía y Astrofísica.
X-ray Bursting Neutron Stars
Authors: Inoue H. 
Published: June 2019

The maximum peak luminosity of the X-ray bursts from a burster is most likely interpreted as the Eddington luminosity of a helium-rich envelope surrounding a neutron star. If this interpretation is true, we can obtain a relation between the mass and the radius of the neutron star in terms of the maximum effective temperature of bursts. On the other hand, the most naive understanding of the origin of the 4.1 keV absorption line often detected in X-ray burst spectra gives us another relation of the neutron star mass with its radius. By solving two simultaneous equations, we can determine the values of the mass and the radius of the neutron star, respectively. However, the result is critical to every neutron star model currently considered.The persistent emissions from X-ray bursters are also discussed.
IAU North Poles and Rotation Parameters for Natural Satellites
Authors: Lieske J. H. 
Published: June 2019

In 1970 the IAU defined any object'snorthpole to be that axis of rotation which lies north of the solar system's invariable plane. A competing definition in widespread use at some institutions followed the “right hand rule” whereby the “north” axis of rotation was generally said to be that that of the rotational angular momentum.A Working Group has periodically updated the recommended values of planet and satellite poles and rotation rates in accordance with the IAU definition of north and the IAU definition of prime meridian.In this paper we review the IAU definitions ofnorthand of the location ofprime meridianand we present the algorithm which has been employed in determining the rotational parameters of the natural satellites.
Nécessité de trois paramètres pour la classification précise des étoiles des premiers types spectraux
Authors: Chalonge D. 
Published: June 2019

RésuméUne classification stellaire utilisant trois paramètres quantitatifs a été constitute : elle permet de classer des étoiles qui n'avaient pas place dans les anciens systèmes.Une classification précise exige trois paramètres aussi bien pour la population I que pour la population II. Lorsque les valeurs des trois paramètres caractérisant une étoile sont connues, sa magnitude absolue semble déterminée sans ambiguité : ainsi toute « dispersion cosmique » disparaîtrait. Cette notion serait la conséquence du manque de precision de la classification à deux paramètres qui a été employée jusqu'ici.
Evidence against Formation of the Stellar Bulge by Mergers Taking Place over a Hubble Time
Authors: Rich R.M. 
Published: June 2019

Data on abundances and ages of stars in the nuclear bulge of the Galaxy are in conflict with a scenario in which the bulge has been slowly accumulated by mergers of Magellanic Cloud-like systems taking place over a Hubble Time.I review the abundance distribution of 88 K Giant stars in Baade's window, and show that the distribution is fit by the simple model of chemical evolution unmodified by gas infall. The metal rich stars in the bulge could not have formed in small galaxies of ≈ 1010 solar masses, which do not retain their metal-enriched gas.Two large surveys of luminous evolved stars in the bulge–the M giant surveys of Blanco, and the carbon star surveys of Azzopardi, Lequeux, and Rebeirot, find no luminous carbon stars or M supergiants which would signify the presence of an intermediate-age population. I present infrared photometry of 33 bulge carbon stars which shows that they are intrinsically faint, confirming the lack of an intermediate age population.The lack of young turnoff stars in the color-magnitude diagrams of bulge fields by Terndrup and Rich further strengthens the case against a substantial bulge population younger than 5 Gyr.
Large-Size Message Construction for ETI: Self-Interpretation in LINCOS
Authors: Ollongren Alexander , Vakoch Douglas A. 
Published: June 2019

Messages for ETI written in a terrestrial language admitting linear notation, should be supplied with extra-linguistic annotations – also linearized in some way – as an aid for interpretation by recipients. In several papers the first author has advocated the use at the second level of an abstract system (a new Lingua Cosmica, still under development), based on constructive logic – with a minimal set of primitives. Expressions at the meta level explain the logic contents of messages.The interaction between any LINCOS and text may suffice for interpretation of both – provided the messages and annotations are of considerable size. Finding a measure for the sizes involved is, however, a non-trivial problem. As a result, one is interested in methods for interpreting a LINCOS without recourse to natural languages. The present paper is concerned with the problem of interpretation of the new system within itself. For that purpose, interpretation of parts of it and (complete) propositional logic in terms of each other is considered (commutativity). This leads to self-interpretation as all semantic terms reside in the closed context of the system.
Ultraviolet classification of Wolf-Rayet stars
Authors: Rochowicz Krzysztof 
Published: June 2019

The ultraviolet spectra of 94 WR stars obtained from Vilspa IUE archive are used here to look for classification criteria in the UV region alone. We have tried to select as many single and SB1 type stars as possible in the Galaxy and the LMC to get the complete, flux-calibrated spectra between 1150 and 3250 Å. Altogether 56 (34 of WN and 22 of WC type) stars in the Galaxy and 38 (31 of WN and 7 of WC type) in the LMC were found, for which at least single SWP and LWR (or LWP) low resolution images are accessible – note that this is about one third of the number of known galactic and LMC WR stars. The set of stars we study is representative according to spectral subtype and brightness (it is almost complete to 12 magnitude for galactic stars). See Niedzielski & Rochowicz (1994) for the list of program stars and associated IUE images as well as for the details of reduction.To look for classification criteria of WR stars in the ultraviolet region we will use the equivalent width (EW) and line width (FWHM) data.
The Cosmic Background Imager
Authors: Pearson T. J. , Mason B. S. , Padin S. , Readhead A. C. S. , Shepherd M. C. , Sievers J. , Udomprasert P. S. , Cartwright J. K. 
Published: June 2019

The Cosmic Background Imager (CBI) is an instrument designed to make images of the cosmic microwave background radiation and to measure its statistical properties on angular scales from about 3 arc minutes to one degree (spherical harmonic scales from l ˜ 4250 down to l ˜ 400). The CBI is a 13-element interferometer mounted on a 6 meter platform operating in ten 1-GHz frequency bands from 26 GHz to 36 GHz. The instantaneous field of view of the instrument is 45 arcmin (FWHM) and its resolution ranges from 3 to 10 arcmin; larger fields can be imaged by mosaicing. At this frequency and resolution, the primary foreground is due to discrete extragalactic sources, which are monitored at the Owens Valley Radio Observatory and subtracted from the CBI visibility measurements.The instrument has been making observations since late 1999 of both primordial CMB fluctuations and the Sunyaev-Zeldovich effect in clusters of galaxies from its site at an altitude of 5080 meters near San Pedro de Atacama, in northern Chile. Observations will continue until August 2001 or later. We present preliminary results from the first few months of observations.
Dust, HII and molecules towards OH and H2O masers
Authors: Forster James R. 
Published: June 2019

Radio synthesis observations made with the BIMA interferometer at 29, 86 and 216 GHz are presented for twelve galactic fields containing multiple interstellar OH and H2O maser sites. A dusty molecular cloud was found at 20 of the 23 maser sites in the fields studied. The clouds have masses in the range 50 to 800 M⊙ and diameters between 0.1 and 0.5 pc.The data show that most masers are located near the centers of massive, dusty molecular cores. The cores appear to be centrally condensed and internally excited. These results suggest that most masers found in star-forming regions are associated with a massive young object at the center of a collapsing molecular cloud. The kinematics of the core gas, and association with ultra-compact HII regions, implies that the duration of the maser phase includes collapse, expansion and early formation of an HII region.
Accurate Parallaxes and Stellar Ages Determinations
Authors: Lebreton Y. , Michel E. , Goupil M.J. , Baglin A. , Fernandes J. 
Published: June 2019

Uncertainties on stellar ages due to the physical description of the stellar material entering the models and to measurements of global parameters and chemical composition are estimated in the case of A/F stars.With combined efforts on atmosphere modeling (to improve global parameters), on asteroseismology (to improve the physical description of the stellar interior) and on distance determination at the level of the sub-milliarcsecond (to improve luminosity), an accuracy on age determination of about 10% is foreseeable.
The New Catalogue of Positions and Proper Motions of 5115 Bright Stars Compiled as the Result of the International “Bright Stars” Program
Authors: Molotaj O.A. , Tel'Nyuk-Adamchuk V.V. , Chernega N.A. , Kanivec' N.D. 
Published: June 2019

At Kyiv University Observatory, in accordance with IAU resolution, the Combined Catalogue of Positions and Proper Motions of 5115 Bright Stars in the FK5 system for Epoch and Equinox J2000.0 (BSC, see reference) has been compiled using 20 source catalogues obtained within the framework of ‘Bright Stars’ International Program. The source catalogs are Bordeaux-66, Bucharest-65, Bucharest-68, Belgrade-79, Cape-68, Kharkiv-70n, Kharkiv-70s, Kyiv-66, Kyiv-73, El Leoncito-70, Moscow-76, Mykolaiv-65, Perth-70, Perth-75, Santiago-65, Santiago-67, Strasbourg-65, Tashkent-64, Tokyo-68, Washington-66. The BSC accumulates around 30,000 source catalogue positions observed within 1960-1980. The standard errors of BSC do not exceed 0.1 arcsec and 0.25 arcsec/cy for positions and proper motions, respectively. The systematic differences between BSC and FK5 in positions for the mean BSC epoch 1970 as a rule do not exceed several hundredths of arcsec. A comparison of the BSC with the PPM catalogue indicates that in the latter the accuracy of positions and proper motions of the ordinary bright stars is slightly worse than that of average values given by the authors of the PPM. It is important to note that the comparison of the BSC with PPM for various star subsets shows deviations of both the HPS bright star system and the rest of the PPM bright stars, on the one hand, from the stars of the FK5 Extension contained in the PPM on the other hand. To examine the BSC proper motion system the stellar astronomy constants and correction to precession have been determined using the BSC proper motions. The parameters obtained agree with the standard ones. But the Oort constants are slightly smaller than those of standard.The BSC catalogue as a whole is acceptable for astrometry usage with respect to both accidental and systematic accuracy.
Inscriptions from Samos
Authors: Gardner Percy 
Published: June 2019

The chief fruit of Mr. Theodore Bent's recent visit to Samos is the discovery of an important agonistic inscription, which gives a list of victors in some games at Samos, probably the Heraea. The limits of date are given on the one hand by the mention of Apameia, founded by Seleucus Nicator, on the other hand by the absence of all Roman names. The forms of the letters with their squareness and strongly marked extremities seem to indicate the second century B.C.The Heraea were celebrated at Samos from early times. Plutarch tells us that after the battle of Aegospotami the Samians renamed the festival after Lysander. But it soon resumed the older name. In one inscription of imperial times it is called in an inscription of the Antonine age the festival is termed The festival was doubtless a great Ionic πανηγυρίς, attended by all the pleasure-loving people of the coast and worthy of the language in which the Homeric hymn speaks of the Delian festival.
A Summer in Phrygia: Some Corrections and Additions
Authors: Anderson J. G. C. 
Published: June 2019

In my second article on Phrygia, Vol. xviii., pp. 101 and 109, mention is made of some Latin inscriptions which were reserved until the stones should be re-examined. I had the opportunity of seeing them again this summer, and I now publish them, together with a few corrections and additions to both papers.Vol. xvii., p. 401, l. 18. Read ‘the small river nearest but one to Saraï Keui on the east’; see the inset map, Pl. IV.P. 418 ff. This inscription is discussed by A. Schulten in a paper entitled Libello dei coloni d'un demanio imperiale in Asia in Mitth. des Instituts, Röm. Abtheil., 1898, pp. 231–247. My restorations, which had to be made very hurriedly and with an inadequate knowledge of the special literature of the subject (e.g. of the important inscription of Skaptoparene, which throws so much light on our document), were merely tentative suggestions; but it seemed better to publish the inscription at once for the benefit of scholars than to hoard it up until an exhaustive commentary could be written on it.