bluuebunny/crossref_metadata_2025_split huggingface dataset:
Dynamical Effects in the Central Region of the Galaxy
Authors: Sanders Robert H. 
Published: July 2016

For the purpose of this Paper, I will define the central region of the galaxy as being the inner four kiloparsecs. I make this definition for three reasons:1) Outside of four kiloparsecs, the rotation curve for the galaxy is well-defined by the Schmidt disk model; whereas, inside four kiloparsecs, the effects of a central spherical component on the rotation curve become conspicuous. This inner spheroid is a dynamical component of the galaxy which is distinct from the disk and may be distinct from the extended halo component as well.2) There is a conspicuous hole in the total gas density distribution inside 4 kpc.3) High peculiar or non-circular gas velocities are observed within the inner 4 kpc; velocities ranging from the 53 km s-1of the so-called 3 kpc arm, to 165 km s-1in the molecular clouds within 300 pc of the center.I will now discuss these points in some greater detail.
Introduction
Authors: Pecker Jean-Claude 
Published: July 2016

Abstract1. Evolution of the modelling of the inside of the Sun, from “standard models” to the more empirical approach used now, and based on neutrino astronomy, solar sismology, and the interpretation of active phenomena. 2. New concepts introduced in the set of physical equations valid inside the Sun, under the pressure of new observations. 3. Similar trends seeming to affect in a comparable way the modelling of the solar cycle. 4. Other stars, and the improved knowledge of solar evolution may help to understand many observed features of rotation, magnetism, etc...Conclusion: the Sun is “one”, - and it cannot safely be studied piecemeal.
Cataclysmic Variables as Binary Stars: Then and Now
Authors: Kraft Robert P. 
Published: July 2016

AbstractA brief history is given of the clues that led to the establishment, in the period c. 1950 to 1965, of a universal binary model for novae and related cataclysmic variables. The observational facts, established early in this period by A. H. Joy and R. F. Sanford (selected binary orbits), J. L. Greenstein (spectroscopy) and M. Walker (photometry) are reviewed, as are the theoretical ideas that formed the basis for the early models, viz., those of G. Kuiper (restricted 3–body problem), A. Sandage and M. Schwarzschild (stellar evolution), J. Crawford (“dog-eat-dog” hypothesis), F. Hoyle and H. Bondi (accretion), S.-S. Huang (angular momentum losses), and S. Chandrasekhar (gravitational radiation). Some comparisons are made between “what we knew then and what we know now.” With apologies to all, the speaker will recall some anecdotes of an earlier time and comment on developments of the past score of years from a very personal perspective.
New Infrared Results for Classical Novae
Authors: Gehrz Robert D. 
Published: July 2016

AbstractRecent infrared studies of classical novae are described. The nucleation and growth of dust in nova ejecta was confirmed by optical/infrared photometry of several novae during the past five years including QU Vul, V842 Cen, V827 Her, and QV Vul. These novae provided evidence that dust of every astrophysical chemical and mineral composition can condense in nova ejecta. Infrared forbidden fine structure lines were identified in the recent novae V1819 Cyg, QU Vul, OS And, and V827 Her. The implication of IRAS measurements for nova energetics is discussed.
The Peculiar Slow Nova X Serpentis
Authors: Duerbeck H.W. , Seitter W.C. 
Published: July 2016

The very slow nova X Ser (t3 = 555d), situated at a large distance from the galactic plane (z ≈ 4kpc), reached maximum light at 9m in May 1903. It was discovered 5 years later on a Harvard plate (Leavitt 1908). No outburst spectrum is known. A photographic outburst light curve is given by Walker (1923); additional photometric data were published by Sakharov (1954) and Kinman et al. (1965). The light curve, shown in Fig. 1, presents 10-day means, based on all published data, and unpublished data taken from Emily Hughes Boyce’s notebook, Harvard College Observatory Plate Collection.Hughes Boyce (1942) discovered a 275d periodicity during minimum light. From the fragmentary light curve in Fig. 1, including three more recent ‘oscillation’ maxima, a period of 277 days is found. If one assumes that the nova reached Mpg = −6 at maximum, the typical value for a slow nova, the mean absolute magnitude at minimum, Mpg = +2, together with the observed amplitude of about 2m and a relatively long mean period, suggests a very late-type (typically M6e) semi-regular variable.
Chemical Composition of Nova Centauri 1986
Authors: de Freitas Pacheco J.A. , Dell'Aglio R. , Costa D. , Codina-Landaberry S.J. 
Published: July 2016

We have obtained extensive spectroscopic observations of Nova Cen 1986 at different phases of the event.From the observed Hα/Hβ line ratio we derived a colour excess EB-V = 0m.54. Using the empirical relationship between the fading time and the absolute magnitude at maximum light as well as the width of the Nal interstellar lines, we estimated for the nova a distance of 1.2 ± 0.2 kpc. The full-width of non-blended lines at the nebular phase indicates an expansion velocity of 1400 ± 120 km s−1The temporal behaviour of the Hβ emission suggests that the electron density varies with time as Ne ∝ t−3, i.e., the shell evolves more or less homologously. The electron temperature was estimated from the [NII] and [OIII] line ratios. In the O+2 region the electron temperature is in the range 14100 ± 1200 K. The N+ region has a lower temperature, T ≃ 8000 K around day 142 after maximum light. The N+ temperature increases in this region as the shell evolves and attains the same values observed in the O+2 region around days 300-470.
Novae Between Outbursts
Authors: Livio Mario 
Published: July 2016

AbstractThe paper is divided into two parts. In the first part, the common envelope phase that follows a nova outburst is discussed. It is shown that this phase leads to mass loss, preferentially in the orbital plane. It is argued, that the common envelope can explain the rapid appearance of a nebular spectrum in novae and the shaping of the nebula.In the second part, the present status of the cyclic-evolution (“hibernation”) scenario is reviewed. It is argued that novae and dwarf novae are the same systems, transforming from one class to the other. Observational and theoretical evidence is presented, that shows that both the accretion rates and the white dwarf masses in observed nova systems should be higher than the average. Novae should therefore not be regarded as “typical” cataclysmic variables. Some critical observations that can provide observational tests are suggested.
Accretion on CO White Dwarfs. Influence of the External Burning Shells on the Evolution
Authors: Hernanz M. , José J. , Isern J. 
Published: July 2016

AbstractThe influence of accretion in the evolution of CO white dwarfs is calculated, up to the thermonuclear runaway, with a previous analysis of the H-He burning shell. For this later study, a two-zone model is developed, consisting of two thin shells in plane-parallel approximation. The influence in the inner core evolution is discussed.
Herbig-Haro Objects
Authors: Böhm K.H. 
Published: July 2016

The available observational information on the geometrical structure, emission line and continuous spectra, line profiles, radial velocities and linear polarization of Herbig-Haro objects is briefly reviewed. We emphasize the inhomogeneous structure of the “classical” Herbig-Haro objects and the appearance of small “condensations” with radii of ~300-900 a.u. The apparent paradox of the presence of “gaseous nebula type” as well as “reflection type” Herbig-Haro objects is discussed.A purelyempiricalmodel of the regions of line formation is discussed. It shows that regions of low density (Ne~103cm-3) cover the space between the condensations and most of the volume of the condensations themselves. Only between 0.1 and 1% of the volume of the condensations is covered by a high density medium (Ne~ 4 x 104cm-3, N ~105cm-3) which, however, contributes very strongly to the formation of the spectrum.Differenttheoretical modelsfor the line forming regions are discussed. We strongly favor the shock wave theory in which the emission lines are formed in the cooling regions of (running) shock waves. The general agreement between observations and the new calculations by Raymond is emphasized, and the few remaining discrepancies are discussed. The possibilities of explaining other properties of Herbig-Haro objects (including time scales, sizes and filling factors of condensations) are described.
Flare Stars in Stellar Aggregates
Authors: Mirzoyan L.V. 
Published: July 2016

After the report on flare stars presented by Ambartsumian and the author (1971) at the last Bamberg Colloquium, some success has been achieved in the study of these interesting objects.Optical observations of stellar flares with high time-resolution undoubtedly proved the explosive character of this phenomenon and the non-thermal nature of the radiation that appears at least at the beginning of the flare. Parallel optical and radio observations of flares in stellar aggregates complicated the interpretation and showed how far we are from an understanding of the physical nature of this phenomenon. Finally, new optical observations of stellar flares in aggregates of different age confirmed the evolutionary significance of this stage in the life of a star and led to the study of certain regularities in the evolution of flare stars.
The Interaction of A Nova with its Circumstellar Envelope
Authors: Malakpour I. 
Published: July 2016

The existence of dusty envelopes around novae is shown by various authors using different methods:We have used the Balmer decrement of novae. In the case of all novae a sudden variation of this decrement is observed a certain time after the beginning of the outburst, the Hα/Hβ ratio rising from its normal value to a maximum and then decreasing again to its normal value.
OH/IR Stars Near the Galactic Centre
Authors: Baud B. 
Published: July 2016

AbstractObservations at 1612 MHz around the Galactic Centre have revealed the existence of 43 OH/IR stars. Sources within 6° longitude from the Galactic Centre appear to be associated with the central parts of the Galaxy. They have a large velocity dispersion and a mean radial velocity of 0 km s−1, indicating that there is no net rotation around the Centre. Within 2° from the Centre there is a strong relative increase in the number of sources with a velocity separation between the two emission peaks of less than 30 km s−1. This is discussed in terms of a possible interaction between the circumstellar shell and the ambient medium.
The Metal-Rich RR Lyraes: Their Origin and Bearing on the Age and Helium Abundance of the Galactic Disk
Authors: Kraft Robert P. 
Published: July 2016

AbstractWe consider further the question of the origin and evolution of metal-rich RR Lyraes (MR-RR’s) in the solar vicinity, continuing the discussion begun by Taam, et al (1976) who showed that MR-RR’s descend from red giants of Eggen’s old disk population. If an old disk giant (ODG) is similar to a giant in a galactic cluster like NGC 188, then it must lose~0.5 M⊙ if it is to pump the HR-RR domain; thus the probability that an ODG will metamorphose into an RR Lyrae is about 1/200th the probability that its metal-poor (halo) counterpart will do so, else the sky would be full of bright MR-RR’s.
Spectral Observations of the Diffuse FUV Background with DUVE (the Diffuse UV Experiment)
Authors: Korpela Eric J. , Bowyer Stuart 
Published: July 2016

AbstractWe present results from a search for FUV emission from the diffuse ISM conducted with an orbital FUV spectrometer, DUVE, which was launched in July, 1992. The DUVE spectrometer, which covers the band from 950 Å to 1080 Å with 3.2 Å resolution, observed a region of low neutral hydrogen column density near the south galactic pole for a total effective integration time of 1583 seconds, the only emission line detected was a geocoronal hydrogen line at 1025 Å . We were able to place upper limits to several emission features that provide constraints to interstellar plasma parameters. We were also able to place continuum limits in this band. We use these upper limits to place constraints upon the emission measure vs. temperature distribution of this gas using an isothermal Landini and Fossi model.
The Structure of the Local Hot Bubble Toward l = 165°, b = 0° Using IUE and ROSAT Data
Authors: de Boer K.S. , Kerp J. 
Published: July 2016

AbstractThe first X-ray-opaque cloud in the direction of Auriga lies at 180 pc. A tenuous cloud, whose distance is derived from IUE absorption line studies as well as from an analysis of ROSAT data, is embedded at 55 pc. The X-ray emitting gas has a temperature of 105.9−6.0 K. The pressure is 1.6 104 K cm−3.
D/H-Ratio: Observations with ORFEUS II
Authors: Gölz M. , Kappelmann N. , Appenzeller I. , Barnstedt J. , Fromm A. , Grewing M. , Gringel W. , Haas C. , Hopfensitz W. , Krämer G. , Krautter J. , Lindenberger A. , Mandel H. , Werner K. , Widmann H. 
Published: July 2016

AbstractDuring the second flight of the ORFEUS-SPAS satellite (Nov./Dec. 96) high resolution (λ/∆λ = 10,000) Echelle-spectra of BD+28° 4211 in the wavelength regime 912–1400 Å have been taken. Deuterium can be clearly identified in the ORFEUSII Echelle-spectra of this star. For the first time it was possible to take spectra of faint, not redshifted objects in the far ultraviolet with a sufficient spectral resolution to study the deuterium column density in the whole spectral range of the Lyman-series down to the Lyman-limit. We obtained a value of log(ND) = 14.7 (±0.3) towards BD+28° 4211. The hydrogen column density has been determined using ORFEUS Echelle- and IUE-spectra of Ly-α (log(NH) = 19.8 (±0.2)). Thus a value of 8 × 10−6 can be obtained for the D/H-ratio on the line-of-sight towards BD+28° 4211.
High-Resolution Optical Observations of Diffuse Clouds
Authors: Welty Daniel 
Published: July 2016

AbstractWe describe results from high-resolution (Δv = 0.3-1.5 km s−1) observations of absorption lines due to interstellar Na I, Ca II, K I, Ca I, and Ti II. At those resolutions, we can identify and characterize many (but not all) of the individual clouds along a given line of sight; complex spatial and/or velocity structure appears to be the norm. Both the spectra and the statistics of individual cloud properties derived from fits to the observed line profiles suggest that: 1) the five species are not entirely coextensive in the neutral ISM; 2) the typical separation between adjacent components (in Na I and Ca II) is ~1.2 km s−1; 3) the median line widths (FWHM) for components in Na I, K I, and Ca I are ≾ 1.2 km s−1; 4) larger line widths for Ca II, even for “corresponding” components at similar velocities, suggest that Ca II is more widely distributed; 5) line widths for clouds in the Galactic halo and in the local ISM (within 100 pc) are generally somewhat larger than for clouds in the general Galactic disk; and 6) components with very different properties (line width, relative abundances, overall column densities) are often separated by only several km s−1. Observations of multiple systems and lines of sight in restricted regions reveal complex spatial structure and velocity coincidences even within 100 pc. These high-resolution optical spectra can be used to model lower resolution UV spectra of many other neutral and singly ionized species, enabling abundances and physical properties to be derived for individual interstellar clouds.
Diffuse Ionized Gas in the β CMa Tunnel
Authors: Dupin Olivier , Gry Cécile 
Published: July 2016

AbstractWe present HST observations of the interstellar medium toward the star β CMa known to be located in a low density extension of the Local Bubble. Most of the matter in the sight-line is ionized and clumped in two main components. One of them, as well as one of the components detected toward ϵ CMa, is mostly ionized and only slightly depleted. Their ionization ratios are compatible with collisional ionization at T~25 000 K. These clouds could have been ionized by shocks related to the Local Bubble creation and also responsible of some dust grain sputtering.
Energetic Particles in the Local Bubble
Authors: Morfill G.E. , Freyberg M.J. 
Published: July 2016

AbstractThe current status of observations of energetic particles in the “local bubble” is reviewed. This includes primarily “direct” measurements of cosmic rays made in the Solar System, but also the “remote sensing” made possible by observing cosmic ray produced γ-rays in the nearby interstellar clouds. Since the energetic events responsible for the formation of our local bubble may also have produced copious amounts of cosmic rays, fossil records are examined to determine whether there is a corresponding signature. The observations show that: 1) the cosmic ray (proton) intensity is fairly homogeneous throughout the local bubble and its adjacent interstellar clouds, 2) there is some evidence for a “recent” local cosmic ray injection about 40,000 years ago, 3) on longer time scales (a few million years) the cosmic ray intensity was constant within a factor two, 4) there is apparently some “activity” in the Orion cloud, as evidenced by low energy γ-ray signatures, and 5) there are two unexplained observations – the variations in the energy spectra, in particular the significantly flatter spectrum of heavy cosmic rays (Fe) and the matter path length variation, which yields consistently larger path lengths for the lighter elements (H, He). It is suggested that these observations are compatible with two cosmic ray populations – an older one in equilibrium with losses from the galaxy and a younger one which is not yet strongly affected by losses. The latter could be a cosmic ray signature of the formation of the local bubble.
Study of the LISM Using Pulsar Scintillation
Authors: Bhat N.D.R. , Gupta Y. , Rao A.P. 
Published: July 2016

AbstractWe present here the results from an extensive scintillation study of twenty pulsars in the dispersion measure (DM) range 3 – 35 pc cm−3 carried out using the Ooty Radio Telescope, to investigate the distribution of ionized material in the local interstellar medium (LISM). Our analysis reveals several anomalies in the scattering strength, which suggest that the distribution of scattering material in the solar neighborhood is not uniform. Our model suggests the presence of a low density bubble surrounded by a shell of much higher density fluctuations. We are able to put some constraints on geometrical and scattering properties of such a structure, and find it to be morphologically similar to the local bubble known from other studies.
Interstellar Scintillation of Radio Sources as a Probe for Investigations of the Local Interstellar Medium
Authors: Bochkarev N. , Ryabov M. 
Published: July 2016

AbstractA possibility of obtaining information on small scale inhomogeneities of the electron component of the local interstellar medium (LISM) is investigated using interstellar scintillations of extragalactic radio sources. We analyse Culgoora array observational data on variability of 190 extragalactic radio sources, covering most of the sky, at 80 and 160 MHz. The variability at time scales from 1 month to 15 years is interpreted as refractive interstellar scintillations in fast-moving nearby (less than 150 pc) hot gas near shock waves in the LISM. All-sky map of scintillation indices m averaged over 3–5 sources closest to one another shows several m maxima. Two of the 3 most pronounced maxima are probably connected with Loop I; the third one coincides with the soft X-ray (0.1–0.3 keV) background maximum near the South Galactic Pole. Other, less certain, m maxima probably correspond to the Orion star-formation region and to a soft X-ray maximum near the North Galactic Pole. The ”free-of-gas” tunnel in the direction l = 240° corresponds to low values of m. The estimated time scale of interstellar scintillations on the above-mentioned LISM structures is in agreement with that of the observed radio-source variations.
The Local Bubble, Local Fluff, and Heliosphere
Authors: Frisch Priscilla C. 
Published: July 2016

AbstractThe properties of the Local Bubble, Local Fluff complex of nearby interstellar clouds, and the heliosphere are mutually constrained by data and theory. Observations and models of the diffuse radiation field, interstellar ionization, pickup ion and anomalous cosmic-ray populations, and interstellar dust link the physics of these regions. The differences between the one-asymmetric-superbubble and twosuperbubble views of the Local Bubble are discussed.
Fluctuations in the Diffuse Soft X-ray Background; Probably of Galactic Halo Origin
Authors: Sumner T.J. , Sidher S.D. , Quenby J.J. , Hernandez M. , Mian A. , Jesseit R. , Gambhir M. 
Published: July 2016

AbstractSoft X-ray background data from the ROSATPSPC have been fitted by a model including emission from the local bubble, embedded hot gas within the disk, hot gas in the Galactic halo and extra-galactic emission, together with local and disk absorption. In all directions a halo component at 106.2 K (0.2 keV) is required for an acceptable fit. The halo emission measure shows spatial variability and the global trend suggests a disk-like planar rather than more extended spherical distribution. New values for the emission measure within the local bubble are derived.
Infrared Emission from Interstellar Dust in the Local Interstellar Medium
Authors: Reach W.T. , Boulanger F. 
Published: July 2016

AbstractIn this contribution, we discuss some topics in the study of dust in the local interstellar medium. The spectrum of local clouds has recently been measured using ISO and COBE, confirming in general the models of excitation and cooling of dust illuminated by the the interstellar radiation field. We discuss in some detail the spatial correlation of interstellar dust and gas and the idea that infrared emission traces the total column density of the interstellar medium, with the particular application to the formation of H2. We also show that dust is present in the nearby Loop I shell, with properties similar to average, suggesting that the walls of the Local Bubble would also have relatively ‘normal’ dust content.
Optical Studies of a Local Filament Toward the Magellanic Clouds and a Local IVC Region
Authors: Penprase B.E. , Wang Q.D. , Herbstmeier U. 
Published: July 2016

AbstractWe present new spectroscopic results which constrain the distance of a large IR emitting filament near the LMC, as well as some new results for a local region with widely distributed detections of Intermediate Velocity Clouds (IVCs). We present spectroscopic observations of stars toward both regions which constrain the distances and kinematics of the interstellar features. New optical high resolution (λ/δλ ⋍ 106) spectra have been obtained for the star HD 22252, and are used to estimate approximate distances, temperatures, and pressures within the cloud. An unusual local region of the interstellar medium with several IVCs is also reported, with multiple components of absorption from -80 < υLSR < 70 km s−1 seen toward several stars in the region.
High-Velocity Clouds and their Soft X-ray Emission
Authors: Kerp J. , Pietz J. , Kalberla P.M.W. , Burton W.B. , Egger R. , Freyberg M.J. , Hartmann Dap , Mebold U. 
Published: July 2016

AbstractDiffuse excess ¼ keV soft X-ray emission was found to be positionally correlated with the column density distribution of the high velocity cloud (HVC) complex C (Kerp et al. 1996). Here we point out that the detected diffuse X-ray emission is indeed associated with the HVC phenomenon. For this purpose we study the ¼ keV radiation transfer as well as the H I column density distribution of HVCs and intermediate velocity clouds (IVCs) towards HVC complex C in detail. We present evidence that on arcmin scales the ¾ keV soft X-ray emission is positionally anticorrelated with the HVC column density distribution of an individual HVC filament of complex C.