bluuebunny/crossref_metadata_2025_split huggingface dataset:
Simultaneous Photometry and Spectroscopy of the Peculiar B[e] Star with Infrared Excess HD 45677
Authors: Klutz M. , Surdej A. , Surdej J. , Swings J.P. 
Published: July 2016

AbstractU, B, V photometric observations performed in February 1977 at the European Southern Observatory (62 cm Bochum telescope) show that for the star B2IV[e] HD 45677 some of the magnitudes and related color indices may vary by as much as 0.03 mag. over one night, and about 0.1 mag. from night to night. The conclusion derived from our photometric run confirm those published by Feinstein et al (1976), namely that “A variation in V is almost systematically accompanied by a change in B-V but of opposite sign”. We further find that a variation in V is well correlated with a similar change of the U-B index: such a correlation existed in the data of Feinstein and coworkers, although it had not been reported.Our spectroscopic material, that was obtained simultaneously with the photometry mentioned above, consists, of 38 spectra that cover the blue region at a dispersion of 20 A mm-1. Such an important sample of spectrograms has not yet been analysed in great detail for intensities, radial velocities, etc. . We will only report here on striking variations that were detected in the profiles of the following lines: Hγ, Hδ, Hε, Ca II(H) and Mg II λ 4481.
Spectral Evolution of Nova Vulpeculae 1976
Authors: Rafanelli P. , Vittone A. 
Published: July 2016

Nova Vulpeculae 1976 was discovered by G.E.D. Alcock (1976) on October 21, 1976 as a star of visual magnitude 6.5 in position (1950): The visual light curve, plotted together with the color index B-V in fig.1, was obtained using the observations published in the I.A.U. Circulars. It shows a slow fall from maximum, about 2.5 magnitudes in 60 days, with characteristic fluctuations, an abrupt drop of about 3.5 magnitudes in 24 days, a slow recovery of one magnitude in 30 days, and a very gradual decline to minimum. The color index B-V remained almost constant near the mean value +1.1 during the slow early decline.
Element Abundance Analyses of Novae
Authors: Williams Robert E. 
Published: July 2016

AbstractThe different methods by which element abundances in novae have been determined are reviewed. Curve of growth studies of novae at maximum light have indicated CNO nuclei to be greatly enhanced with respect to hydrogen in certain objects. These results are questionable because they depend upon an assumed temperature distribution in the photosphere which is probably too steep to be realistic. Emission line analyses of novae, generally obtained in the period of early decline, also indicate possible heavy element enhancement, however these results are tentative because of uncertainties in the parameters of the emitting gas. It is suggested that useful abundance determinations of nova ejecta might be obtained from studies of old, extended nova shells.
Chemical Composition of Nova Cygni 1975
Authors: Boyarchuk A.A. 
Published: July 2016

AbstractThe chemical composition of Nova Cygni 1975 was determined by a curve-of-growth analysis. A strong excess of helium and the CNO -group abundances and a normal Si abundance was found.Spectral observations of N Cyg 1975 were begun at the Crimean Astrophysical Observatory on 29 August 1975, at 18h 50m UT, one day before light maximum (Boyarchuk et al. 1977). Twelve spectrograms with a dispersion of 4,6 and 12 Å/mm were taken during this night. The spectral type of the Nova was B2 Ia+ and no emissions appeared in the spectrum. During the following night, 10 spectrograms were obtained. The spectral type of the Nova was A2 Ia+ qe, and strong emission lines with P Cygni-type profiles could be detected. Since absorption lines were not observed on 30 August, only the spectrograms taken on 29 August can be used for a curve-of-growth analysis.
On the Photometric Variations of the Irregular Variable Red Giant HD 65750 in the Reflection Nebula IC 2220
Authors: Dachs J. , Isserstedt J. , Rahe J. 
Published: July 2016

AbstractThe light-curve between 1964 and 1977 for the variable M2II giant HD 65750 = V341 Car is derived from 77 photographic and 83 photoelectric UBV measurements and analyzed. It is concluded that the light variations of the star are irregular and due to variable extinction in the circumstellar nebula. The appearence of the visible reflection nebula IC 2220 into which HD 65750 is embedded, has been found to vary on a time scale of four years.
Variable Stellar Wind from the WN-Star HD 151932
Authors: Seggewiss W. 
Published: July 2016

AbstractThe effects of the interaction of strong Wolf-Rayet stellar wind with the surrounding interstellar medium in ring-type nebulae are briefly discussed.The outstanding variability of the envelope of the WN 7 star HD 151932 is explained by small density fluctuations. Variable WR wind may be the reason for the filamentary structure observed in ring-type nebulae.
Absolute Energy Distribution in Rho Cassiopbiae
Authors: Joshi S.C. , Rautela B.S. 
Published: July 2016

AbstractThe continuous energy distribution of ρ Cas obtained in the wavelength range 340 - 710 nm has been compared with the energy distribution of δ CMa in the same wavelength range. The circumstellar shell associated with ρ Cas seems to modify the continuum of the star appreciably. Variations in the Balmer emission of ρ Cas taking place within a day are noticed.
1. Radiation Pressure and Poynting-Robertson Drag for Small Spherical Particles
Authors: Soter S. , Burns J. A. , Lamy P. L. 
Published: July 2016

A new heuristic derivation of the radiation pressure and Poynting-Robertson drag forces is presented for particles with general optical properties; previous derivations considered only perfectly absorbing materials. The equation of motion for a particle of mass m and geometrical cross-section A, moving with velocity v through a radiation field of energy flux F, is (to terms of order v/c)where r̂ is the radial unit vector, ṙ is the radial velocity, and c is the speed of light. The radiation pressure efficiency factor Qpr includes both scattering and absorption, it is evaluated using Mie theory for small spherical particles with measured optical properties that are irradiated by the actual solar spectrum. Very small particles (<0.01 μm) are not substantially affected by radiation forces.
6. The Nature of Asteroid Surfaces, from Optical Polarimetry
Authors: Dollfus A. , Geake J. E. , Mandeville J. C. , Zellner B. 
Published: July 2016

Telescopic observations of the polarization of light by asteroids are interpreted on the basis of a systematic polarimetric analysis of terrestrial, meteoritic and lunar samples. Laboratory measurements were made using samples with different surface textures, and scanning electron microscope pictures were used to investigate the influence of microtexture and crystalline structure.It is demonstrated that asteioid surfaces do not accumulate thick regolithic layers of micro-fragments, as do the Moon and Mercury. This is because the majority of debris ejected by impacts are lost, due to the low gravitational escape velocity from these bodies. However, asteroids are not bare rocks, but are coated with a thin layer of adhesive debris. This coating apparently has the composition of the body itself. The fact that there is no indication of significant maturation by space weathering suggests that the dust which coats the surface of asteroids is frequently replaced by further impacts.Asteroids may be classified polarimetrically in several groups: those in group C are made of very dark material and behave like carbonaceous chondrites, or very dark Fe-rich basalts; Those in group S correspond to silicates and stony meteorites. A third group represented by Asteroid 21 Lutetia and 16 Psyche may be metallic.
Introductory Lecture: The Local and General Interstellar Medium
Authors: Breitschwerdt Dieter 
Published: July 2016

AbstractImportant progress in the field of the Interstellar Medium (ISM) in general, and the Local Interstellar Medium (LISM) in particular, has been largely due to the recent launch of orbiting satellite missions and earth-bound observations with unprecedented sensitivity and high spectral or spatial resolution. However, the interpretation of a wealth of new data is still based to a great extent on models that were designed for the previous generation of observations. Thus there remains a clear gap between our theoretical understanding of the basic physics of the ISM and the detailed information available. In such a situation it seems appropriate to focus on some key observations and discuss their implications for modelling.
The Diffuse Extreme Ultraviolet Background
Authors: Vallerga John , Slavin Jonathan 
Published: July 2016

AbstractObservations of the diffuse EUV background towards 138 different directions using the spectrometers aboard the Extreme Ultraviolet Explorer satellite (EUVE) have been combined into a spectrum from 150Å to 730Å and represent an effective exposure of 18 million seconds. There is no significant evidence for any line flux from any source other than the geocorona. These results are inconsistent with the Wisconsin C and B broad-band surveys assuming the source is a logT = 5.8 – 6.1 hot plasma in ionization equilibrium with solar abundances, confirming the previous result of Jelinsky, Vallerga & Edelstein (1995) (hereafter Paper I) using an observation along the ecliptic with the same instrument. To make these results consistent with the previous broad-band surveys, the plasma responsible for the emission must either be depleted in Fe by a factor of ~ 6, be behind an absorbing slab of neutral H with a column of 2×l019cm−2, or not be in collisional ionization equilibrium (CIE). One particular non-CIE model (Breitschwerdt & Schmutzler, 1994) that explains the soft x-ray results is also inconsistent with this EUV data.
Modeling the Local Bubble Using Multiple Supernova Remnants
Authors: Smith R.K. , Cox D.P. 
Published: July 2016

AbstractWe have modeled the Local Bubble (LB) using a one-dimensional hydrocode (ODIN) that can simulate multiple supernova remnants, with non-equilibrium ion evolution and dust. Our model assumes that the local interstellar medium was a cool (104 K) gas approximately 5-10 Myr ago; it was then disturbed by 2 or 3 supernovae exploding within 20-30 pc of each other over a period of 2-4 million years. The LB is the leftover hot gas from these explosions. The model predicts the x-ray emission from such a bubble, as well as ionic abundances for hot gas ions such as O VI. These are compared to the soft x-ray data from the Wisconsin all-sky survey and the ROSAT PSPC.
Neutral Clouds Within the Local X-ray Plasma
Authors: Kerp Jürgen , Pietz Jochen 
Published: July 2016

AbstractWe present new results based on the analysis of ROSAT PSPC observations towards nearby neutral clouds. These clouds are detectable as deep soft X-ray absorption features within the ¼ keV energy band. Towards one of these clouds, optical absorption line measurements determine an upper distance limit of D ≤ 60 pc. The presented data suggest that this filament is only a part of a much more extended local–cloud structure. Here we demonstrate that we most probably detected a local neutral atomic hydrogen “wall” in the direction of a low–velocity arc (Pietz 1994).
Kinematical Structure of the Local Interstellar Medium
Authors: Génova R. , Beckman J. E. , Rodríguez Álamo J. 
Published: July 2016

AbstractObservations of interstellar Na I in the spectra of 93 stars within 315 pc from the Sun show that it lies in a tunnel of gas moving away from Scorpio-Centaurus and is surrounded by gas moving toward the Galactic center.Gas approaches the Sun from Scorpio-Centaurus expanding from (r, l, b)=(160 pc, 313°7, +28°2) with LSR velocity 15.3 km s−1. The radius of this shell is 153 pc.We identify these clouds:D: velocity vector (υd, ld, bd)=(+7.2 km s−1, 305°1, −13°5), above and below the Galactic plane (GP) in the range of Galactic longitudes 357°–55°.C: velocity vector (υc, lc, bc)=(+11.5 km s−1, 349°0, −35°2), above and below the GP in the range 30°≤l≤110°.M: velocity vector (υm, lm, bm)=(+21.9 km s−1, 34°2, +1°5), above and below the GP in the range 100°≤l≤130°.P: velocity vector (υp, lp, bp)=(+13.8 km s−1, 244°9, +5°4), above and below the GP from l~120° to the limit of our data at l~210°.E: velocity vector (υe, le, be)=(+16.8 km s−1, 208°4, +6°2) in the range 160°≤l≤185° and −10°≤b≤–35°.A: velocity vector (υa, la, ba)=(+12.9 km s−1, 73°6, −5°6) towards the Galactic anti-center, below the GP.I: velocity vector (υi, li, bi)=(+37.7 km s−1, 132°8, −64°3) towards the Galactic anti-center, above the GP.
Radio, Millimeter and Infrared Observations of the Local Hot Bubble and Its Environment
Authors: Mebold Ulrich , Kerp Jürgen , Kalberla Peter M.W. 
Published: July 2016

AbstractWe present a definition of the local void of neutral gas from observations in the radio frequency window. We question the concept of the Local Bubble in sense of a more or less spherical volume which is surrounded by a shell of denser gas. The concept of the Local Bubble is challenged by the discovery of numerous neutral, dense clouds inside the local void. The search for a “shell” around the suspected Bubble has resulted only in inconclusive findings so far. The sample of high latitude molecular clouds illustrates the situation particularly well. The statistical properties of their spatial distribution, e.g. the mean distance, seem to fit very nicely to the spatial extent of the Local Bubble. But a more detailed investigation shows that the concept of a bubble – in particular an expanding bubble – is not supported. We suggest that the local void is nothing more than a typical place in an interarm region of our Galaxy.Finally, a discussion of the high latitude boundary of the local void does not give strong evidence for the concept of a bubble, that has once been in rapid expansion and is still showing signs of interaction with its environment. However, indications for interactions of IVCs or HVCs with their surroundings are found. These hint at the presence of a gaseous disk which is much more vertically extended than previously believed, or at a Galactic wind which may be blowing from the Galactic neighbourhood of the Sun.
Pulsars and Bubble Dynamics
Authors: Parui Ramen Kumar 
Published: July 2016

AbstractBased on recent observation of the dominance of the flare generated solar wind streams over the co-rotating streams and a significant lowering in the cosmic ray intensity in the abnormal year of the solar activity period, I have predicted the occurrence of discernible changes in magnetic field strength and the thickness of the shell of the local bubble during high sunspots years of the solar cycle period. In order to observe the variation, both in the magnetic field strength and in the thickness of the compressed shell, a proposal of continuous monitor of these two parameters through the observation of Faraday Rotation Measure has been proposed with an emphasize to the observations in the period of next abnormal year of the solar cycle in near future.
Mapping Cool Gas in the ISM with ROSAT
Authors: Hutchinson I.B. , Warwick R.S. , Willingale R. 
Published: July 2016

AbstractWe have investigated the distribution of cool gas within the local interstellar medium (<150 pc) using data derived from both the ROSAT X-ray and EUV all-sky surveys. The EUV/X-ray spectra for a sample of 89 white dwarf stars and 200 active late-type stars have been analysed to give an estimate of the gas column density along each object’s line of sight. In order to extend the sky coverage we have also included in the analysis 190 late-type stars detected only in the X-ray band. The derived NHI measurements confirm the size of the local low density bubble as typically 50-100 pc and also show that in the general direction of Loop I there is a substantial excess of absorption at a range of distances from 10-150 pc.
Tracing Small-Scale Fluctuations in the Soft X-ray Background
Authors: Warwick R. , Hutchinson I. , Willingale R. , Kuntz K. , Snowden S. 
Published: July 2016

AbstractAn overlapping set of ROSAT PSPC observations made in a region of very low Galactic foreground column density, has been used to investigate variations in the soft X-ray background on angular scales of 15′ – 5°. In the ¼ keV band there is a clear inverse correlation of the count-rate with the line-of-sight hydrogen column density. However, after correcting for this absorption effect, strong residual fluctuations remain in the data, with an amplitude which is significantly larger than that due to the counting statistics or the confusion of unresolved discrete sources. In contrast a similar analysis for the ¾ and 1.5 keV ROSAT bands shows no evidence for an excess signal. The most likely origin of the ¼ keV fluctuations would seem to be in a patchy distribution of ~ 106 K gas in the Galactic halo.
Cirrus as a Probe for the Galactic Bubble Bath
Authors: Miville-Deschênes M.-A. , Boulanger F. , Reach W.T. 
Published: July 2016

AbstractGalactic filaments called cirrus are used here to study the froth structure of the interstellar medium. Using the Leiden/Dwingeloo HI survey we observe that a significant fraction of intermediate latitude cirrus are distant clouds (RGal < 6 kpc) and that some cirrus extend far above (or below) the Galactic plane (1 kpc). Among them, a supershell centered at l = 15°, b = –12° is studied.
26 Al Radioactivity in the Galaxy
Authors: Diehl R. , Oberlack U. , Knödlseder J. , Bennett K. , Bloemen H. , Hermsen W. , Ryan J. , Schönfelder V. , von Ballmoos P. 
Published: July 2016

Abstract26Al radioactivity is believed to originate predominantly from massive stars, ejected into interstellar medium in wind phases and/or supernova events. With its million-year decay time, penetrating γ-rays from 26Al decay measure the massive-star history averaged over a time scale of ≃million years, thus extending times cales accessible otherwise. The COMPTEL 1.809 MeV all-sky data from 5 years of observations show irregularities and features at intermediate latitudes, which may have a more local origin (≃ 1 kpc). We find that the large scale emission can be characterized by a Galactic scale height of ≃ 130 pc, and a Galactocentric scale radius of ≃ 5 kpc, with features from spiral structure. Catalogues from massive-star related objects do not significantly improve the description of COMPTEL data above this. Emission associated with nearby structures such as the Gould Belt, Loop I, or stellar aggregates, is indicated, yet cannot be clearly detected. Combined with our imaging results, this suggests that 26A1 yields from massive star ensembles depend on specifics of those stars and their history. Further 26A1 γ-ray studies are underway to help mapping of the massive star history in the solar vicinity.
The Galactic Fountain
Authors: Kahn F.D. 
Published: July 2016

AbstractThe Galactic fountain is driven by the hot inter-cloud medium (ICM). The ICM itself is heated by successive supernova explosions. This process introduces sufficient irregularities to prevent the fountain flow from being smooth. Instead it leads to the formation of a frothy medium above the disk (Avillez, Berry & Kahn 1997). This paper describes the effect of successive supernova explosions, in a rather idealised case. The real case is still more complicated, but the present approach shows why it is so.
The HI Supergiant Shells in the Large Magellanic Cloud
Authors: Kim S. , Staveley-Smith L. , Sault R.J. , Kesteven M.J. , McConnell D. , Dopita M.A. , Bessell M. 
Published: July 2016

AbstractWe present the result of an HI aperture synthesis mosaic of the Large Magellanic cloud (LMC), made recently with the Australia Telescope Compact Array (ATCA). The resolution of the mosaiced images is l′.0 (15 pc, using a distance to the LMC of 50 kpc). In contrast to its appearance at other wavelengths, the LMC is remarkably symmetrical in HI on the largest scales, with the bulk of the HI residing in a disk of diameter 8.°4 (7.3 kpc). Outer spiral structure is clearly seen, though the features appear to be due to differential rotation, therefore transient in nature. On small to medium scales, the combined action of numerous shells and supershells dominate the structures and motions of the HI gas in the LMC. A good correlation is seen between supershells previously identified in Hα (e.g. Meaburn 1980) and HI structures. We compare the results with a new wide-field Hα image.
Workshop for Continued Discussion of the Local Bubble
Authors: Sanders Wilton T. , Frisch Priscilla C. 
Published: July 2016

AbstractAt the end of the regularly scheduled conference, the organizers made available a large sunny conference room for the remaining participants to continue discussion. The main topics were the structure of the Local Bubble and the properties of the Galactic X-ray halo. Here we try to summarize the main points of those discussions.
Wolf-Rayet Wind Models: Photometric and Polarimetric Variability
Authors: Rodrigues Cláudia V. , Magalhães Antônio Mário 
Published: July 2016

AbstractWe have modelled the observed random variation in broad band intensity and polarization of some isolated Wolf-Rayet stars assuming that their winds have localized, enhanced density regions (blobs). Our model is based on a Monte Carlo code that treats all Stokes parameters of the radiation bundle. This study indicates that the blobs must have sizes comparable to the stellar dimension and be near the base of the envelope. These blobs can be interpreted as a variable structure of large geometric cross section causing the observed polarimetric and photometric variability.
Radio Evidence for Non-isotropic Outflows from Hot Stars
Authors: White Stephen 
Published: July 2016

AbstractRadio diagnostics for outflows from hot stars are reviewed and three well–studied examples (WR 140, η Car and MWC 349) are discussed in some detail. The three systems are very different and their radio properties are diverse, but in each case, the radio data provide strong evidence for the presence of equatorially–enhanced outflows.
HST WFPCII Observations of the Inner HR Car Nebula
Authors: Hulbert Stephen , Nota Antonella , Clampin Mark , Leitherer Claus , Pasquali Anna , Langer Norbert , Schulte-Ladbeck Regina 
Published: July 2016

AbstractWe present Hα observations of the inner region of the HR Carinae nebula. The inner nebula looks clumpy and material appears to be present only to the east of the central star. A jet-like filament stretches away from the central star to the southeast.
Observing Hot Stars in all Four Stokes Parameters
Authors: Eversberg Thomas , Moffat Anthony F.J. , Debruyne Michael , Rice John B. , Piskunov Nikolai , Bastien Pierre , Wehlau William H. , Chesneau Olivier 
Published: July 2016

AbstractWe introduce a new polarimeter unit which, mounted at the Cassegrain focus of any telescope and fiber-connected to a fixed CCD spectrograph, is able to measure all Stokes parameters I, Q, U and V photon-noise limited across spectral lines of bright stellar targets and other point sources in a quasi-simultaneous manner. We briefly outline the technical design of the polarimeter unit and the linear algebraic Mueller calculus for obtaining polarization parameters of any point source. In addition, practical limitations of the optical elements are discussed. We present first results obtained with our spectropolarimeter for three prototype hot-star.
Non-spherical Radiation-Driven Wind Models
Authors: Puls Joachim , Petrenz Peter , Owocki Stanley P. 
Published: July 2016

AbstractThe present state of modelling radiatively driven stellar winds from rapidly rotating stars is reviewed. Various processes affecting the actual, still controversial wind structure are highlighted, in particular non-radial line-forces and gravity darkening, and useful scaling relations are provided. The importance of accounting for consistent NLTE line-forces depending both on the actual density structure and radiation field (as function of latitude and radius) is stressed, and some independent test calculations confirming earlier numerical results are reported.