bluuebunny/crossref_metadata_2025_split huggingface dataset:
The Summer Schools of the Vatican Observatory
Authors: McCarthy Martin 
Published: July 2016

Starting on the 10th of June, 1986, the staid and quiet halls and courtyard and corridors, including the giant circular staircase designed by Bernini for the little donkeys that carried Popes to their quarters in the summer palace, echoed to the swift patter of lightfooted students and the buzz of their conversations as 17 young men and 8 young women met at the first Vatican Observatory Summer School in Astronomy and Astrophysics at Castel Gandolfo.These 25 scholars had been chosen from a list of 135 candidates at university and graduate school campuses all over this planet. More than 30 candidates were rejected for “excellence”; they were judged to be too far advanced for admission to the classes on Galaxies and Dark Matter and to those on Spectral Classification and on Instrumentation for Photometry and Image Processing. The classes were aimed at students just beginning or planning immediate entrance into graduate level classes; the School was not planned for “new Ph.D.s,” for “post-docs,” or for those already well into thesis work. Criteria for admission included academic grades, recommendations of university professors, plus personal statements from the candidates on reasons why they felt they wanted to attend the sessions of the school. Applications were studied by faculty and staff members and results were announced in January, giving students some four months to arrange their travel and home commitments so they could be free to respond to the school bells on June 10.
500 - 3200 Å Observations of the Interacting Binary Stars V356 Sgr and β Lyr
Authors: Polidan R. S. 
Published: July 2016

AbstractIn this paper we present new results from the Voyager ultraviolet spectrometers and the IUE spacecraft on V356 Sgr and β Lyr. The V356 Sgr observations cover, in detail, two eclipses and include one IUE high dispersion SWP image. During both eclipses the total strength of the UV emission lines were found to be invariant. Also, an uneclipsed UV continuum was detected at wavelengths shorter than 1600 Å. The IUE high dispersion SWP spectrum revealed that the emission lines are extremely broad, almost symmetrical lines with weak, slightly blue shifted absorption components. No evidence of carbon is seen in the emission or absorption spectrum of V356 Sgr in eclipse. A model for the origin of the circumstellar matter in this binary system is presented. The Voyager ultraviolet observations of β Lyr show a strong far-UV continuum that is detectable down to 912 Å The far-UV continuum flux level was variable on time scales shorter than the orbital period and displayed no obvious orbital modulation or eclipses. The spectral shape of the far-UV continuum closely resembles that of a UX UMa type cataclysmic variable. On 16 August 1985 an rapid brightening of the far-UV continuum was observed which was also reminiscent of cataclysmic variables. Analysis of the β Lyr data suggest that the central object must be small, with a radius on the order of 1 R⊙ or less.
Resolving Information on Algol Systems
Authors: Budding Edwin 
Published: July 2016

AbstractOur awareness of the facts on Algol systems, arising from both statistical evidence and examination of particular examples, is presented. The statistical information derives from the author’s recent catalogue of Algol-type candidate stars. The particular cases of R Ara and W Cru are considered. The presence of undiscerned background factors in these systems exemplify persistent threats to the confidence we place on parameter sets characterising any models we may form of such objects.
New Ways to Rotation Rates
Authors: Wilson R. E. 
Published: July 2016

AbstractProgress in determining rotation rates of Algol primary stars from light curves is assessed. Included are elementary ideas on why the new method works, how to carry out solutions, and how and when to apply the constraint on rotational lobe filling. Some comments are made on desirable improvements for measuring rotation from line broadening. A few remarks are made about the problem of identifying likely fast rotating Algols.
Spectroscopic Observations of the Early-Type Contact Binary AW Lacertae
Authors: Nakamura Y. , Okazaki A. , Katahira J. 
Published: July 2016

Abstract.Spectroscopic observations were performed of the early-type contact binary AW Lac with an image-intensified coude spectrograph of 1.9−m telescope at the Okayama Astro-physical Observatory. A total of twenty-two spectra covering blue region with a dispersion of 16 Amm−1 have been secured on Kodak IIa-O baked plates. In every spectra sharp interstellar Call H,K lines are clearly seen. The spectral type of AW Lac has been estimated as early B, which substantially confirms the one adopted in the photometric analysis by Jiang et al. (1983) and is diffrent from A0 listed in General Catalogue of Variable Stars (Kholopov et al. 1985). Contrary to the suggestion by the photometric solution of Jiang et al., no definite secondary lines could be separated, though some indications of light contamination due to the secondary component are surely observed. This would imply that the light ratio of the components should be somewhat smaller than that derived by photometric analysis. No emission features appeared either. The measurement of radial velocities of the primary component for the orbital elements was made for twenty spectra by a conventional method. It was difficult to measure the radial velocities because the lines are quite broadened and deformed. Hence the measured values for the radial velocities should be regarded as rather preliminary. The derived spectroscopic elements, combined with the photometric data, give the absolute dimensions of the system for each assumed mass ratio q. For q = 1, being the adopted photometric solution by Jiang et al., we obtain too small value for the primary’s mass, comparing with its spectral type. For the mass ratio as small as q = 0.6, we can obtain a reasonable value for the mass of the primary. However, in order to get more definite conclusion the cross-correlation method would be more appropriate for the spectroscopic analysis of this system.
The Binary system V380 Cygni
Authors: Battistini P. , Bonifazi A. , Guarnieri A. , Lolli M. 
Published: July 2016

This binary system, according to Semeniuk and Paczynski (1971), is very interesting because it is probably in a phase of rapid evolution through the Hertzsprung gap in the HR diagram and shows apsidal motion (Battistini et al. 1974) .The system was Observed at the Bologna Astronomical Observatory in UBV because the only known light curve (Kron 1935) is insufficient to give appropriate orbital elements (Kopal 1940, Ramella et al. 1980) and it is impossible to fit photometric elements with spectroscopic results (Batten 1962). The observations started in 1970 and ended in 1973; in 1980 the system was reobserved to complete light curve coverage.
The Old Nova BT Monocerotis
Authors: Seitter W. C. 
Published: July 2016

AbstractSpectroscopic observations through most of the eclipse cycle of BT Mon reveal the presence of both low and high velocity gas streams. Acceleration through a Laval-nozzle-effect at the inner Lagrangian point of the system and powering of the emission lines through kinetic energy losses of Coriolis deflected and subsequently colliding gas streams are considered as possible mechanisms at work in the system.
The Contact Binary AE Phoenicis - An Analysis from Deconvoluted Spectra
Authors: Becker H. J. 
Published: July 2016

AbstractA method is described for an analysis of deconvoluted stellar spectra, and applied to new spectroscopic observations of the close eclipsing system AE Phuenicis, obtained with the 1.52 m telescope of the Southern European Observatory at La Silla, Chile. Results are presented for the rotational velocities of this variable, together with a proposed model of the system.
Spectroscopic Segregation in Binary Systems
Authors: Darius Jon 
Published: July 2016

AbstractBinary systems displaying spectroscopic segregation, whereby line spectra of the two components overlap little or not at all in wavelength, account for a small subset of LUV objects (late-type ultraviolet). Optical and ultraviolet (IUE) spectra for one such system, HD 15351 + UV0225 + 13 (F4-5 V + sdO), are presented and a few related systems described. The role of LUV objects in establishing an absolute luminosity calibration for hot subdwarfs is emphasized, along with their significance for stellar evolution. A search strategy for additional spectroscopically segregated LUV objects is outlined.
Magnetic Braking in Cataclysmic and Low-Mass X-Ray Binaries
Authors: Vilhu O. 
Published: July 2016

AbstractThe chromospheric-coronal emission of lower Main-Sequence single and binary stars can be correlated with an activity parameter of type R = g(B-V)P-1 where P is the rotation or orbital period and g(B-V) a function of the color resembling the convective turnover time. Observations indicate that the active region area coverage filling factor grows as R2, and the whole stellar surface becomes filled with closed loop structures at R ≂ 3. A braking formula is proposed (Equation 4) to include all periods (0.d1 ≲ R ≳ 30d) and spectral types F-M. On the basis of this equation, the mass transfer rates in compact binaries (driven by the gradual loss of orbital angular momentum) are discussed. It is concluded that the magnetic braking has good chances of being that mechanism which drives the mass transfer in cataclysmic variables and galactic bulge X-ray sources.
Diameter Measurements of Asteroids
Authors: Dollfus Audouin 
Published: July 2016

Direct optical measurements of asteroid diameters obtained by telescopic observations are scarce. Although several adequate instrumentations and techniques are available for the purpose, they have not been used. The importance of these determinations should be stressed for the attention of observers.The filar micrometer was used only by one observer during the last century, and no additional measures have been made since. This was in 1894 and 1895 when E. Barnard (1902) used the 90 cm refractor of Lick Observatory, and the 100 cm refractor of Yerkes Observatory. The results are as follows:Ceres: apparent diameter at 1 AU: l˝.060, or 770 km (28 nights)Pallas: apparent diameter at 1 AU: 0˝.675, or 490 km (5 nights) Juno: apparent diameter at 1 AU: 0˝.266, or 195 km (5 nights)Vesta: apparent diameter at 1 AU: 0˝.531, or 390 km (21 nights)
Asteroid Polarimetry: A Progress Report
Authors: Veverka J. 
Published: July 2016

This is a brief report on the present status of asteroid polarimetry. A detailed paper is in preparation jointly with T. Gehrels.The first polarization measurements of asteroids were made by Lyot (1934), who photographically determined the polarization curves of Ceres and Vesta. These curves are reproduced by Dollfus (1961). Unfortunately, because of the low sensitivity of the photographic method, they do not agree very well with recent photoelectric measurements.The first photoelectric polarization measurements of asteroids were made by Provin (1955) (details of this work are given by Dollfus, 1961), and in recent years this work has been extended by Gehrels (unpublished) and by Veverka (1970). To date, fairly complete polarization curves for about a dozen asteroids have been obtained, and at least partial data are available for twice that number.
Photometric Observations and Reductions of Lightcurves of Asteroids
Authors: Taylor Ronald C. 
Published: July 2016

The brightness-time variation (the lightcurve) of an asteroid is observed to obtain the rate of rotation, some indication of the shape, and the orientation of the rotation axis in space. The brightness-phase relations are observed for the study of surface texture.This paper deals specifically with observing routines and reductions, including discussions of lightcurves, rotation periods, absolute magnitudes, phase coefficients, opposition effects, and pole determinations. This paper supplements the review chapter by Gehrels (1970). Only photoelectric techniques are considered because the visual and photographic ones are, nearly without exception, not precise enough.
Descriptive Survey of Families, Trojans, and Jetstreams
Authors: Van Houten C.J. 
Published: July 2016

The word “group” is so general that I would like to suggest that here it is used in its most general way: a group of asteroids is a collection of minor planets that have some feature in common. If we agree on this use of the word “group,” then we can discern the following asteroidal groups:(1) Groups that have a dynamical cause:(a) Trojans(b) Commensurability groups:(i) Hungaria group(ii) Hilda group(iii) Thule(2) Groups that probably have no dynamical cause:(a) Hirayama families(b) Brouwer groups(c) Jetstreams
Collisional Focusing of Particles in Space Causing Jetstreams
Authors: Trulsen Jan 
Published: July 2016

Jetstreams probably played an important role at an intermediate stage of the formation of the solar system (Alfvén and Arrhenius, 1970). A Jetstream is defined here as a collection of grains moving in neighboring elliptical orbits around a central gravitating body and with the dynamics modified by the action of complicated collision processes among the grains themselves.Three main types of collisions will take place in such a stream. Hyper-velocity impacts will lead to fragmentation of the grains involved. At lower impact velocities, the particles will retain their identities after the collision even if they might be deformed to some degree depending on impact velocity and internal structure of the grains. With still lower impact velocity, accretion can take place, the grains sticking together after collision to form larger grains. A common feature of these collision processes are that they will be partially inelastic. A certain fraction of the kinetic energy of the colliding particles will be spent on changing their internal structure. The internal kinetic energy in an isolated Jetstream thus will tend to decrease with time. The mass spectrum of the grains also will vary during the lifetime of a stream, the probability for accretive processes increasing with time.
Possible Magnetic Interaction of Asteroids with the Solar Wind
Authors: Greenstadt Eugene W. 
Published: July 2016

Investigation of extraterrestrial objects is habitually accompanied by the observation of extraterrestrial magnetic fields, which often have significant effects on the solar wind in the vicinity of the objects. Should we be surprised to find this experience repeated at an asteroid?A recent study considered the conditions that would have to be satisfied by the surface magnetic field of a small planetary body at asteroidal distances so that the field would be an obstacle capable of stopping the solar wind or deflecting it sufficiently to generate a detectable magnetic interaction (Greenstadt, 1971).
Ionization Equilibrium for Ions of Na, Al, P, Cl, A, K, Ca, Cr and Mn
Authors: Landini M. , Monsignori Fossi B.C. 
Published: July 2016

Ionization equilibrium calculations, which have a number of astrophysical applications, have been computed by Jordan for the ions of C, N, O, Ne, Mg, Si, S, Fe, and Ni.The aim of this paper is to extend the evaluation to other elements relevant to the investigation of the solar atmosphere. Ions of Na, Al, P, Cl, A, K, Ca, Cr, and Mn have been considered and the ionization balance has been computed for temperature from 104to 107K.The computation is performed including collisional ionization, autoionization, radiative recombination and dielectronic recombination.
The Use of Synchrotron Radiation in the Energy Calibration of Astronomical Apparatus
Authors: Gurzadyan G. A. , Ohanesyan J. B. 
Published: July 2016

The problem of energy calibration of astrophysical apparatus is essential for every or almost every space experiment. The utilization of synchrotron radiation from an electronic accelerator should perhaps be taken as an ideal solution of this problem, if of course, such a possibility is available.Special equipment for the extraction of synchrotron radiation has been devised at the circular electron accelerator with a maximum electron energy of 6 GeV, in the Physics Institute of Erevan (Gurzadyan and Ohanesyan, 1972). The equipment is designed primarily for the energy calibration of astronomical apparatus operating in a vacuum and hard ultraviolet and X rays. However, the equipment can also be applied to a wide range of experiments relating to the physics of solids, crystallography, physics of thin films, X rays, etc.
Missing Solar Ultraviolet Opacity and Diatomic Molecules
Authors: Tarafdar S. P. , Vardya M. S. 
Published: July 2016

AbstractThe solar atmosphericmodel calculations incorporating absorptionby hydrogen and metals and Rayleigh scattering by hydrogen give larger specific intensity in the solar ultraviolet spectrum than that observed. This discrepancy has been interpreted as due to some unknown source(s) of opacity in this spectral region. We have, therefore, compared the absorption coefficient due to bands of nine diatomic molecules with that of metals and hydrogen in the ultraviolet spectral region at temperatures and pressures appropriate to the solar photosphere. The molecular band absorptions due to A-X bands of CO, SiO and OH and to B-X band of CH have been found to be larger than or equal to the total absorption by metals and hydrogen below 4000 Å and may be able to account for the missing opacity except possibly between 2500 Å and 3000 Å. Whether absorption due to some other molecular band or bands is responsible for the opacity in this wavelength interval is not certain.
Spectroscopic Techniques in X-Ray Astronomy
Authors: Speybroeck Leon Van 
Published: July 2016

The catalog of X-ray sources now includes types I and II super-novae remnants, at least one pulsar, other periodic or quasi-periodic sources, starlike objects which emit primarily in X rays, normal galaxies, radio galaxies, Seyfert galaxies, a quasar, and an apparently isotropic extragalactic background. There is ample evidence that X-ray emission is characteristic of many of the most interesting objects in astronomy, and the background may have cosmological implications. This should not be too surprising, since significant X-ray emission occurs whenever high energy electrons interact, and high energy electron production is usually associated with explosive phenomena.The most useful energy range for X-ray observations extends from about 200 eV to perhaps 10 keV. The low energy limit results from the absorption by the interstellar media, which of course varies from object to object; some typical cutoffs are given in Table I. The high energy limit, which is much more arbitrary, results from the usually observed rapidly decreasing emission with increasing energy, and also from the lack of important characteristic emission or absorption features above this energy range. In many cases, however, observations outside of this energy range are required to definitively identify a dominant source mechanism.
CNO Abundances and Nova Outburst Strengths
Authors: MacDonald Jim 
Published: July 2016

ABSTRACTSimple theories of hydrogen shell flashes on accreting white dwarfs are used to find the requisite conditions for classical novae. It is shown that enhancement of CNO abundances, relative to the Sun, is necessary for fast novae yet slow novae, such as DQ Her, can still occur with large CNO abundances. An analysis of observational data indicates that the white dwarfs in nova binaries have masses typically 1.1 Mʘ. For some old novae, the accretion rate, deduced from the accretion disk luminosity, is too high to permit a strong enough hydrogen flash to give the observed nova strength. Some possible resolutions to this paradox are suggested.Recurrent novae are probably not thermonuclear runaways on accreting white dwarfs.
The Formation of Optical CNO Emission Lines in Cataclysmic Variables
Authors: Williams Robert E. , Ferguson Donald H. 
Published: July 2016

ABSTRACTSpectroscopic observations of CNO emission lines are presented for old nova systems, and possible excitation processes for the lines are considered. The Bowen fluorescence mechanism cannot generally be responsible for the strength of N III λ4640 because of the weakness of 0 III λ3429. Other CNO lines are observed which indicate that all of the lines are excited by resonance fluorescence of UV continuum radiation. Several nonfluorescent excited lines of carbon are also present in old novae, probably formed by recombination processes. The available data for the optical CNO lines suggest that non-solar CNO enhancements exist in quiescent novae, indicating that some of the binary systems may be evolved.
The Origin and Evolution of Cataclysmic Binaries
Authors: Eggleton P.P. 
Published: July 2016

ABSTRACTSome cataclysmic binaries may be products of Case C evolution of low mass stars (orbital period ~ 1 yr; masses ~ 1 - 4 Mʘ), involving a common envelope phase. Other mechanisms, probably involving late Case B and even early Case B, but with significant loss of angular momentum, may be necessary to account for some evolved binaries such as AA Dor or V Sge. Further angular momentum loss, probably by magnetic braking coupled with tidal friction, causes secular evolution in cataclysmic binaries. It is suggested that tidal friction may account for the shortage of cataclysmics with periods ≲ 1.3 hr; but this cutoff, as well as the gap in the period distribution between 2 and 3 hrs, is hard to explain and imposes more severe constraints on possible theories than is commonly acknowledged.
Basic Data on Hydrogen-Deficient Stars
Authors: Drilling J.S. 
Published: July 2016

AbstractThe current state of our knowledge on the distribution and motions of various types of hydrogen-deficient stars, and of their positions in the H-R diagram, is reviewed. It is concluded that the extreme helium stars (with the exception of the H-deficient binaries) and cool hydrogen-deficient stars belong to the population of the Galactic nuclear bulge, whereas the intermediate helium stars are young stars of Population I. The helium-rich sdO stars appear to be a local sample which is predominantly Population I.
Spectroscopic Analyses of Hot Extreme Helium Stars
Authors: Heber U. 
Published: July 2016

AbstractSpectroscopic fine analyses of hot extreme helium stars are reviewed. The chemical composition is discussed in detail and conclusions as to the nuclear history of the atmospheric material are drawn. Evidence of inhomogeneities among the hot extreme helium stars is presented and it is concluded that the extreme helium stars can be found in the halo population (BD+10°2179) as well as in the disc population. Their mass loss rates are of the same order of magnitude (10−9 M⊙/yr) as those of normal stars. Four helium rich sdO stars are identified as possible descendants of the B-type extreme helium stars.
The Light Curve of the Pulsating Extreme Helium Star BD +13°3224: Further Evidence of a Decline in the Period Decrease Rate
Authors: Lynas-Gray A.E. , Kilkenny D. 
Published: July 2016

AbstractFurther optical and infrared (J-filter) observations are presented for the extreme helium star BD +13°3224. No infrared excess, which could have been attributed to a cool companion, is found. Very recent times of maximum light confirm the ephemeris cubic term already proposed. Current models for the evolution of BD +13°3224, while approximately accounting for the period decrease rate (Ṗ), do not explain the decreasing Ṗ indicated by the cubic term.
Abundance Analysis of R CrB Variable UW Cen
Authors: Giridhar Sunetra , Rao N. Kameswara 
Published: July 2016

Abstract:Burrell (1976) performed an abundance analysis of the southern R CrB star UW Cen and reported a metal deficiency by a factor of 660 compared to the sun. However, his analysis was made employing very uncertain gf values, which resulted in lower estimates for Texc and Tion etc. We have reanalysed his data using new values and model atmospheres calculated by Schönberner (1975). Our analysis shows that the star has nearly solar abundance.