bluuebunny/crossref_metadata_2025_split huggingface dataset:
Slitless Spectroscopy of Stars with Grating-Prism and Focal Reducer Techniques
Authors: Geyer E. H. 
Published: July 2016

AbstractA slitless field spectrograph for Cassegrain telescopes has been designed. It is based on the focal reducer optical arrangement and grating prisms. Together with the “multiple diaphragm method” not only a gain in limiting magnitude of 3 to 4 magnitudes has been achieved, but also other drawbacks of the classical objective prism camera are avoided.
On the Practical Application of the MK and Related Spectral-Classification Systems to Spectrograms of Various Resolutions
Authors: Ardeberg A. 
Published: July 2016

AbstractFor MK classification of program field stars the “normal” observer is confronted with a number of practical problems, rendering classification on the true MK system very difficult. These problems concern completeness of standard-star grid, spectrogram resolution, comparison of originals-reproductions, spectrogram density levels, spectrogram widening and emulsion. A new atlas of slit spectrograms at 74 Å mm−1 is presented, giving good coverage especially for high-luminosity stars. MK classification from spectral intensity tracings is discussed. Advantages include easy distribution and sharing of standards, relaxation of resolution requirements and wide acceptable density range. Apparent shortcomings of the method seem easy to overcome. An atlas of spectral intensity tracings is presented. Some problems regarding objective-prism classification are discussed for higher as well as lower resolution. Quantitative classification methods are commented. Work in progress is presented on systems for two-dimensional classification of low-resolution objective-prism spectrograms of stars with spectral types earlier than G0.
Discrepant Measurements of the Radial Velocities of SS Cygni: Solution to the Problem
Authors: Robinson E.L. 
Published: July 2016

AbstractWe show that the discrepancies among the various measurements of the radial velocity curve of the K5 V star in the dwarf nova SS Cyg have been caused by (1) poor choices of lines for measuring its velocity and (2) large distortions in its velocity caused by heating from the white dwarf and its accretion disk. The correct K velocity of the center of mass of the K5 V star is 158 ± 3 km s−1.
Periodic Variations in the Spectrum of the Dwarf Nova WX Hyi in Outburst and Minimum
Authors: Vogt N. , Curé M. 
Published: July 2016

AbstractWe present the analysis of spectrograms obtained during quiescence and during an ordinary outburst of the SU UMa type dwarf nova WX Hyi (ESO 3.6m telescope, B&C spectrograph with Image Disector Scanner, 171 Åmm−1, range 4000–7000 Å, time resolution 6min.). The radial velocities of these spectra have been discussed by Schoembs and Vogt (1981) who also derived the orbital elements of WX Hyi. The phases φmax refer to these elements. All velocities discussed here are with respect to the white dwarf, not to the center of mass of the binary system.In quiescent state we did not find significant radial velocity variations. The equivalent widths Wλ of the He I emission lines revealed periodic variations with an amplitude of ≈30%, maximal values of Wλ were observed at φmax = 0.0... 0.2. In contrast, the equivalent widths of the Balmer lines were not variable.During outburst we found periodic radial velocity variations of the emission peak of Hα, Hβ and He I 5875 with an amplitude of ≈100 km s−l, φmax ≈ 0.5. Also the broad Balmer absorption lines revealed periodic radial velocity variations, with a similar amplitude (φmax = 0.3...0.5). The equivalent width of the Hα central emission peak varies with an amplitude of ≈30%, φmax ≈ 0.85. No variations of the equivalent width of the Balmer absorption lines were found.The outburst observations suggest that the preceeding part of the disc is brighter than the following one (in orbital motion). This is probably due to heating of the preceeding part by collisions with circumbinary matter, which seems to have an enhanced density in outburst as compared to the quiescent state. The emission lines are formed in outer layers or in a halo around the disc. The equivalent width variations can be interpreted in terms of interactions between this halo and the optically thick part of the disc.A more detailed discussion of the data is being published elsewhere.
Ultraviolet Observations of Cataclysmic Variables
Authors: Verbunt F. 
Published: July 2016

AbstractThe preliminary results of the analysis of more than 1000 spectra of cataclysmic variables in the archive of the International Ultraviolet Explorer were presented at the meeting. To characterize the slope of the spectra I use F = log(f1460Å/f2880Å). For most spectra F lies between 0.2 and 0.7. No correlation of F with orbital period, inclination, system type or (for dwarf novae) length of the interoutburst interval are found, apart from somewhat lower values of F for DQ Her type systems. Out of 16 dwarf novae for which spectra both at outburst maximum and minimum are available 11 show no large difference in F between maximum and minimum, and in 5 F declines with the flux level. Out of 6 dwarf novae 5 show very red spectra during the rise to maximum, and 1 shows slopes during rise similar to those during decline.In the ultraviolet resonance lines, due to a wind from the disc, no correlation is found between inclination and terminal velocity.
IUE Observations of HL CMa and the Winds of Cataclysmic Variables
Authors: Mauche C.W. , Raymond J.C. 
Published: July 2016

AbstractAs evidenced by the P Cygni profiles of their ultraviolet resonance lines, cataclysmic variables—like early-type stars—are known to have extensive, high velocity winds. Assisted by AAVSO visual data and IUE ultraviolet spectra, we present an observational and theoretical study of the P Cygni profiles of the dwarf nova HL CMa. As these profiles are dependent upon the ionization structure of the wind, we describe a model of a radiatively-driven shocked wind for cataclysmic variables, and present results for the temperature and ionization structure of the outflowing gas.
Explosion of White Dwarfs
Authors: Lopez R. , Isern J. , Labay J. , Canal R. 
Published: July 2016

AbstractWe present models for Type I supernova light curves based on the explosion of partially solid white dwarfs in close binary systems. Studies of such explosions show that they leave bound remnants of different size. Our results reproduce quite well the maximun luminosities, the expansion velocities and the shape of the light curve. As the two basic papameters that govern the light curve, the ejected mass and the mass of 56Ni produced, are variable our models reproduce the slow and fast subclasses of “classical” Type I supernovae.
The Variable Ṁ Scenario for Nova Outbursts
Authors: Kovetz A. , Prialnik D. , Shara M.M. 
Published: July 2016

AbstractAn evolutionary scenario for classical novae is proposed, which is intended to solve the discrepancies that exist between theory and observations: the space densities of classical novae deduced from surveys in the solar neighbourhood are lower by about two orders of magnitude than those predicted theoretically, and the mass transfer rates in nova binaries, as estimated from observed luminosities in quiescence, are higher than those allowed by the thermonuclear runaway model for nova outbursts. These discrepancies disappear if mass transfer (at a high rate) takes place for only a few hundred years before and a few hundred years after an eruption, but declines afterwards and remains off for most of the time between outbursts. We show that such a behavior is to be expected if one takes into account the variation of binary separation, due to mass ejection on the one hand and angular momentum losses on the other hand.One of the aspects of this scenario, on which we report in more detail, is the possibility of enhanced Roche-lobe overflow of the secondary, due to its expansion that results from irradiation by the high nova luminosity. We followed the evolution of a 0.5M⊙ main sequence star illuminated by a changing flux, typical of a classical nova. The numerical results indicate that, in spite of the slight binary separation that may occur after eruption, mass loss from the irradiated and thus bloated secondary should continue for a few hundred years. Other aspects of the variable Ṁ scenario are briefly summarized.
The Frequency of Novae in the Galaxy
Authors: Liller W. 
Published: July 2016

AbstractRecent statistics indicate that each year an average of 3.5 novae or nova-like objects are discovered in the Galaxy. With reasonable assumptions about the completeness of the surveys, we arrive at an overall galactic production rate of 76 ± 38 y−1. When recurrent novae are omitted, this rate drops to 60 + 30 y−1. Hence, it seems that our Galaxy is more prolific than M31 in nova production. The total amount of material released into galactic space by novae each year is about one-tenth that ejected by supernovae.
Accretion in Magnetic Cataclysmic Variables
Authors: Hameury J.M. , King A.R. , Lasota J.P. , Ritter H. 
Published: July 2016

AbstractWe discuss the arguments in favour of the suggestion that polars (AM Her systems) and intermediate polars (IP’s) have magnetic fields of the same order of magnitude, and form one single class of objects. The period distribution of magnetic cataclysmic variables is well explained if they evolve the same way as non magnetic systems, IP’s becoming AM Her systems after crossing the gap. We discuss some consequences of the limited magnetic moment distribution (1033 ≤ μ ≤ 1034 G cm−3) in magnetic CV’s, in particular for the existence of accretion discs in those systems.
Time-Resolved Optical Spectroscopy of AM Her X-Ray Sources
Authors: Mouchet M. , Van Amerongen S.F. , Bonnet-Bidaud J.M. , Osborne J.P. 
Published: July 2016

AbstractWe present high-time resolution spectroscopy of two AM Her sources E1405−451 and E1013−477. For E1405−451, the Balmer emission lines profiles can be divided into a narrow component and a broad one. The amplitudes of the radial velocity curves of these components are respectively 265±30 km/s and 390±50 km/s. The orientation of the column determined from polarimetry is not compatible with the broad component being formed in the lowest parts of the column. Photometric and spectroscopic results on E1013−477 do not confirm the previous reported 103 min. period. Rapid variability (<1.5h) as well as long term modulation (>3.3h) is present in these data.
Optical and UV Observations of the Intermediate Polar 3A0729+103. Modulation with the Orbital Period
Authors: Falomo R. , Bonnet-Bidaud J.M. , Charles P.A. , Maraschi L. , Mouchet M. , Mukai K. , Tanzi E.G. , Treves A. 
Published: July 2016

Abstract3A0729+103 (= BG CMi) is an intermediate polar discovered through its X-ray emission (McHardy et al. 1981, 1984). The orbital period is 3.235 hours and the rotation period is 15.2 minutes, For ephemeris and references on the source we refer to McHardy et al. (1984). We report here on optical (4025 to 5090 A) and ultraviolet (1200 to 3200 A) spectroscopy obtained, respectively, on Dec 1, 1984 and April 21, 1985. Our data show clear modulation of spectral features with the orbital period.
Rapid Mass Accretion on a Fully Convective Star
Authors: Sarna M.J. , Ziólkowski J. 
Published: July 2016

AbstractWe investigated the effects of rapid mass accretion on a fully convective main sequence star of 0.3 M⊙, taking into account the heating of its photosphere by the kinetic energy of the infalling matter. We found that the star develops highly inhomogeneous structure consisting of almost unperturbed initial convective core and a radiative envelope composed of the accreted matter. Both regions are separated by a very stable temperature inversion layer. Due to such structure accreting convective star may significantly increase its radius (contrary to earlier suggestions).
Hydrogen Depletion and the Evolution of Cataclysmic Variables to Low Mass X-Ray Binaries
Authors: Williams R.E. , Phillips M.M. , Heathcote S.R. 
Published: July 2016

AbstractCertain cataclysmic variables may evolve into low mass X-ray binaries if the white dwarfs can steadily accrete sufficient mass to exceed the Chandrasekhar limit. We present spectra of a recurrent nova and a low mass X-ray binary which are very similar to each other, and are also unusual for the strengths of the observed He II emission. We suggest that this similarity is not coincidental, but is evidence for an evolutionary link between the two classes of objects. A hydrogen depletion in the accreting gas is implied from the emission line fluxes, and may be an important parameter in determining whether accreted gas remains bound to the white dwarf, enabling eventual core collapse to occur.
X-Ray and Optical Observations of the X-Ray Source EX0020528+1454.8
Authors: Hudec R. , Wenzel W. , Goetz W. , Valníček B. , Peřestý R. , Richter G.A. , Hacke G. , Huth H. , Mrkos A. , Tremko J. 
Published: July 2016

AbstractWe present preliminary results of the EXOSAT X-ray observations and quasisimultaneous and simultaneous optical photometry of the X-ray source EX0020528+1454.8 = 1E0205+149 found independently as an serendipitous source both with Einstein and EXOSAT satellites. The optical counterpart is a pair of dMe stars, Our results indicate that the object is variable both in X-rays and optical wavelenghts, and probably belongs to dMe flare stars.
IUE Observations of CH Cygni Continuum during 1979–1986
Authors: Mikolajewska J. , Selvelli P.L. , Hack M. 
Published: July 2016

AbstractVariations of the UV continuum have been analyzed. The observed UV continuum may be reproduced by a superposition of a Kurucz model atmosphere (log g=2), Teff~ 8500 - 15000 K) and optically thin hydrogen bound-free and free-free emission (Te~ 1000 K). The temperature of the Kurucz atmosphere is the lowest at the maximum of brightness. The flat minimum in the UV integrated flux was observed in May-October 1985.
Exosat and IUE Observations of the Symbiotic Binary R Aquarii during Maximum and Minimum
Authors: Viotti R. , Piro L. , Friedjung M. , Cassatella A. 
Published: July 2016

AbstractCoordinated IUE and EXOSAT observations of the symbiotic Mira R Aqr, made in June and December 1985, at phases 0.0 and 0.5 of the Mira light curve, are discussed. A weak X-ray flux has been for the first time unambiguously detected without any significant change with the Mira light curve. Also the UV spectrum of the central object has not varied, while the presence of high ionization lines (NV and HeII) in the spectrum of the jet-like feature is confirmed. The data are discussed in the light of a model in which the jet is preexisting material illuminated by the recently increased X and UV radiation from the inner edge of the accretion disk around the degenerate companion of the Mira primary.
The Characteristics of Ancient China’s Astronomy
Authors: Zezong Xi 
Published: July 2016

What are the characteristics of ancient China’s astronomy? Many scholars have discussed the problem. In 1939 Herbert Chatley summed up fifteen points. Joseph Needham(1959) in his great work Science and civilisation in China concentrated it into seven points.
1the elaboration of a polar and equatorial system strikingly different from that of the Hellenistic peoples;2the early conception of an infinite universe, with the stars as bodies floating in empty space;3the development of quantitative positional astronomy and star catalogues two centuries before any other civilisation of which comparable works have come down to us;4the use in these catalogues of equatorial coordinates, and a faithfulness to them extending over two millennia;5the elaboration, in steadily increasing complexity, of astronomical instruments, culminating in the 13th century invention of the equatorial mounting, as an ‘adapted torquetum’ or ‘dissected’ armillary sphere;6the invention of the clock drive for that forerunner of the telescope, the sighting tube, and a number of ingenious mechanical devices ancillary to astronomical instruments;7the maintenance, for longer continuous periods than any other civilisation, of accurate records of celestial phenomena, such as eclipses, comets, Sunspots, etc.
Uses of Ancient Data in Modern Astronomy
Authors: Eddy J A. 
Published: July 2016

AbstractAncient astronomical data are a limited resource that can fill unique needs in modern research. Records from the Orient are of particular value because they were taken more or less continuously, as parts of dynastic and local histories – often for astrological purposes. We review three problems in modern astronomy that lean heavily on ancient records from the Middle East and Orient: the study of solar variability; studies of the variable rotation of the earth; and studies of the occurrence and physics of novae, supernovae and comets.
Solar Physics from Spacelab 2
Authors: Dere K.P. 
Published: July 2016

AbstractFour instruments were flown aboard the Spacelab 2 shuttle mission to perform systematic observations of the solar atmosphere at high resolution and to measure specific global properties of the sun. The Solar Optical Universal Polarimeter recorded series of white light images with which the evolution of the granulation and sunspot phenomena have been studied. The Coronal Helium Abundance Shuttle Experiment provided measurements of a number of EUV coronal lines, and, in particular, the intensities of He IIλ304 and H Iλ1216 from which the coronal helium abundance can be determined. The High Resolution Telescope and Spectrograph obtained stigmatic spectra in the 1200–1700 Å wavelength range, as well as broad band UV spectroheliograms, to provide diagnostic information on the solar chromosphere and transition zone. The Solar Ultraviolet Spectral Irradiance Monitor measured the total solar irrandiance at a resolution of 1.5 and 50 Å in the 1200 to 4000 Å wavelength range to an accuracy of 3Z.
High-Resolution Spectra and Photoabsorption Coefficients for Carbon Monoxide Absorption Bands Between 94.0 run and 100.4 nm
Authors: Yoshino K. , Stark G. , Smith P.L. , Parkinson W.H. , Ito K. 
Published: July 2016

AbstractTheoretical descriptions of the abundance and excitation of CO in interstellar clouds require accurate and complete information on many molecular properties. In particular, data such as line positions, line widths, and photoabsorption coefficients, which will allow the photodissociation rate for CO to be determined, are needed. We have measured some photoabsorption coefficients for CO at a resolving power more than 20 times greater that that used in previous work. Most of our results for bands between 94.0 and 100.4 nm are larger than the values of Letzelteret al.
Charge Exchange in Laboratory and Astrophysical Plasmas
Authors: Pequignot D. 
Published: July 2016

AbstractRecent experiments in tokamak plasmas demonstrate that charge exchanges manifest themselves in a wide variety of situations. It is now realized that charge exchanges involving excited states of hydrogen should be considered: these reactions represent a challenge for atomic physics, detailed plasma modeling, and quantitative plasma diagnostics. Charge exchanges between ions can in some cases modify the state of the gas and produce specific emission.Charge exchanges are important for the ionization balance of many ions in either warm coronal plasmas or photoionized plasmas of Astrophysics. Lines produced by charge exchange have been discovered in the spectrum of nebulae and probably the solar chromosphere. Introduction of charge exchanges modifies earlier views about the structure of some astrophysical objects. The nebulae appear as valuable “laboratories” to check theoretical charge exchange cross sections at very low energy. It is suggested that the detection of charge exchange lines in the solar spectrum would provide new insights into the dynamics of the interface between the chromosphere and the corona. It is pointed out that charge exchanges between heavy particles may have significant effects in the ionization front of some nebulae.
Generation of XUV Spectra by Powerful Picosecond Laser
Authors: Nam C.H. , Tighe W. , Suckewer S. , Feldman U. , Seely J. 
Published: July 2016

AbstractThe development of laser action at wavelengths shorter than those of current X-ray lasers is being investigated along two fronts. In the first case, we are exploring the possibilities for laser action at 15.4 nm in Li-like AIXI and 12.9 nm in Li-like SiXII in a magnetically confined recombining plasma. Previous work on hydrogen-like carbon, CVI, led to lasing action at 18.2 nm. Recently, this has been applied to microscopy and first results from a soft X-ray laser microscope are presented. A new technique to generate shorter wavelength X-ray lasing involves the interaction of a high power laser with a preformed plasma. The Powerful Picosecond Laser (PP-Laser) System with an output power level of 20-30 GW and focussed power density of 1016- 1017W/cm2has recently become operational. The spectra of highly ionized atoms in the XUV region were recorded on a high resolution grazing incidence spectrometer for the PP-Laser beam interacting with different solid targets.
Vuv Spectra Y to Mo
Authors: Chaghtai M.S.Z. 
Published: July 2016

Using R.D. Cowan’s computations (1979) and parametric calculations of Meinders et al (1982), old analyses are thoroughly revised and extended at Aligarh, of Zr III by Khan et al (1981), of Nb IV by Shujauddin et Chaghtai (1985), of Mo V by Tauheed at al (1985). Cabeza et al (1986) confirmed the last one largely.Extensive studies have been reported of the 1–e spectra, Zr IV (Rahimullah et al 1980; Acquista and Reader 1980), Nb V (Shujauddin et al 1982; Kagan et al 1981) and Mo VI (Edlén et al 1985). Some interacting 4p54d2levels of these spectra have been reported from our laboratory, also.Detailed spectral analyses of transitions between excited states have furnished complete energy values for J ≠ 1 levels of these spectra during 1970s and 80s. Shujauddin et al (1982) have worked out Nb VI and Tauheed et al (1984) Mo VII from our lab, while Khan et al (1981) share the work on Zr V with Reader and Acquista (1979).
Wavelengths and Energy Levels for n = 3 − 3 Transitions in F-Like Ions: Cr XVI, Fe XVIII, Ni XX and Cu XXI
Authors: Buchet J.P. , Buchet-Poulizac M.C. 
Published: July 2016

AbstractOn our beam-foil spectra recorded between 100 and 350 Å, we have identified the strongest 3s-3p and 3p-3d transitions of Cr XVI, Fe XVIII, Ni XX and Cu XXI. The Is22s22p53∓level energies have thus been deduced.
Advances in UV Astronomy by the IUE Satellite
Authors: Grewing M. 
Published: July 2016

AbstractOn 26 January 1978 the International Ultraviolet Explorer (IUE) satellite has been launched into a geosynchronous orbit. Operated jointly by NASA, ESA, and the SERC, it has since collected roughly 50.000 UV spectra of objects of widely different nature such as comets and planets orbiting the Sun, nearby cool late-type stars, interstellar matter in our own and nearby galaxies, local and distant hot early-type stars, entire galaxies, and distant quasars. Even the recent supernova SN 1987a in the Large Magellanic Cloud has been and continues to be a target for this satellite just as many other sources in the sky. A few examples have been selected to highlight some of the unique results that have been achieved through observations with the IUE.