bluuebunny/crossref_metadata_2025 huggingface dataset:
V 1500 Cyg: Slow Variability in Post-nova Stage
Authors: Pavlenko E.
Published: July 2016

Regular photometric observations of V1500 Gyg (Nova Cygni 1975) have been carried out at the Crimean Astrophysical Observatory of the USSR Academy of Sciences from 1975 till now. The 0.5 m telescope equipped with a TV system is used to estimate the star brightness in V.

The decline of the mean brightness is presented in Figure 1. The solid lines (1) and (2) show the changes of the V brightness according to Patterson (1979) and Arkhipova and Zaitseva (1978), respectively. The dotted line is drawn according to our data (Pavlenko 1988). The arrows indicate the amplitudes of the light and colour variations.
Maximum Magnitude Vs. Rate of Decline for Novae of the LMC
Authors: Capaccioli M. , Della Valle M. , D’Onofrio M. , Rosino L.
Published: July 2016

We derive the distance modulus of the Large Magellanic Cloud (LMC) by applying the new calibrated relationship between maximum magnitude and rate of decline (MMRD). The result, , is in close agreement with the most recent determinations based on RR Lyrae and Cepheids. We also discuss the properties of the MMRD of M31 and of the LMC.
Optical Spectrophotometry of Nova PW Vulpeculae
Authors: Mikołajewska J. , Mikołajewski M.
Published: July 2016

PW Vul (Nowa Vul 1984 #1) was a slow classical nova which began its outburst in July 1984 and reached optical maximum in the first week of August 1984. Eight low dispersion spectra (160 A/mm) in the blue spectral range (λλ3400-5100 A) were secured between October 1984 and July 1985, with the CCS spectrograph equipped with 3.5 arcsec aperture image slicer and mounted on 90 cm Schmidt-Cassegrain telescope at Toruń Observatory. Kodak IIa-O plates were used. In addition two moderate dispersion (40 A/mm) spectra in the Hγ-Hβ range were obtained on 28 October and 3 November 1984, using the same instrumentation. Standard stars were observed on each night to remove the influence of spectral sensitivity of the photographic emulssion and atmospheric extinction. The calibration of the absolute flux scale was performed by comparing synthetic B magnitudes calculated from our spectra with published B photometry of PW Vul (Voloshina 1985, Noskova et al. 1985, Kolotilov and Noskova 1986). The accuracy of the flux calibration is ±0.1 mag.
Mass of the Ejected Envelope of LV Vulpeculae
Authors: Raikova D.
Published: July 2016

LV Vulpeculae is a fast nova with a relatively smooth light curve (Raikova, 1981). On Fig. 1 the picture of the radial velocities, displayed during the outburst is shown. It is based on our measurements and the published ones (a more detailed paper will appear in C. R. Acad. Bulg. Sci.). The premaximum absorption line system (A) exhibits a rapidly decreasing velocity. It has been observed for the last time on April 17.52 (Hutchings, 1970) together with the diffuse enhanced system (B) of velocity −1260 km/s. Since the presence of the last system is an indication that the light maximum has passed, we can limit a 2h40m interval in which it had occured (on April 17.385 the brightness is still up). We assume that the light maximum has taken place at the middle – on April 17.45. On April 18 the diffuse enhanced line system, now of −1400 km/s, and the principal one (C) of −780 km/s exist. It is worth-while to emphasize that in LV Vul spectrum the diffuse enhanced system appeared before the principal one.
Physical Properties and Abundances of Novae in the Nebular Phase
Authors: Snijders M.A.J.
Published: July 2016

We discuss the derivation and behaviour of temperatures and densities of nova ejecta during the nebular stage. A systematic comparison is made between fairly complete sets of abundances for 3 C/O and 2 Neon novae. The abundances in the ejecta might influence the formation and composition of circumstellar dust in novae.
PAH’s and Silicate Emission in Nova Cen 1986
Authors: Smith Craig H. , Aitken David K. , Roche Patrick F.
Published: July 2016

We present 8 – 13 μm spectra (R ≃ 40) of Nova Cen 1986 (V842 Cen) on 8 occasions between days 162 and 899 after outburst, and all after the onset of dust formation. All observations were made with the UCL cooled grating array spectrometer on the 3.9m Anglo-Australian Telescope or the 2.3m ANU telescope in Australia. All but the last observation (day 899) show evidence for emission from at least two dust components; a featureless continuum (usually attributed to carbon based dust), a broad emissive component centered on 10 μm (probably "silicates"), and the 11.3 μm feature from the family of unidentified infra-red dust features (UIR’s) seen on days 271 – 687.
Infrared Spectra of Recent Novae
Authors: Andrillat Yvette , Houziaux Léo
Published: July 2016

We present CCD spectra of novae PW Vul, QS And, Herculis 87 and V1819 Cyg obtained in the wavelength range 680 to 1080 nm at the Cassegrain focus of the 193–cm telescope at the Observatoire de Haute–Provence (CNRS, France). The reciprocal dispersion is 23 nm/mm.
Soft X-Ray Emission from Classical Novae in Outburst
Authors: Starrfield Sumner , Truran James W. , Sparks Warren M. , Krautter Joachim , MacDonald James
Published: July 2016

Theoretical modeling of novae in outburst predicts that they should be active emitters of radiation at soft X-ray wavelengths twice during their outburst. The first time occurs very early in the outburst when only a very sensitive all sky survey will be able to detect them. This period lasts only a few hours for the very fastest novae. They again become bright in X-rays late in the outburst when the remnant object becomes very hot and is still luminous. Both simulations and observations show that novae can remain very hot for months to years. It is important to observe them at these late times because a measurement both of the flux and temperature can provide information about the mass of the white dwarf, the turn-off time scale, and the energy budget of the outburst.
The Origin and Evolution of Novae
Authors: Tutukov A.V. , Yungelson L.R.
Published: July 2016

The cataclysmic binaries are products of the nonconservative evolution of close binaries with large initial mass ratios of components. The accretors in cataclysmic binaries can be helium or carbon-oxygen or oxygen-neon-magnesium white dwarfs. Their annual birthrates are ~0.005, ~0.005, and ~0.00005 respectively. In one-zone approximation of a thin accreting shell we estimate the critical masses of hydrogen and helium shells and recurrence time scales of thermonuclear runaways.
Effective Growth Rate of White Dwarf Mass in Nova Outbursts
Authors: Kato Mariko , Hachisu Izumi
Published: July 2016

We have obtained the effective growth rate of white dwarf masses which are suffering mass loss during both hydrogen and helium nova outbursts. If the mass transfer rate from the companion is smaller than 10−7 M⊙/yr, the net growth rate is reduced to less than one tenth of the mass transfer rate from the companion star. It is suggested that the white dwarf mass is hard to grow to the Chandrasekhar mass unless its initial mass is very close to the Chandrasekhar limit.
The White Dwarf Mass and Orbital Period Distributions in Zero-Age Cataclysmic Variables
Authors: Politano M. , Webbink R.F.
Published: July 2016

A zero-age cataclysmic variable (ZACV) we define as a binary system at the onset of interaction as a cataclysmic variable. We present here the results of calculations of the distributions of white dwarf masses and of orbital periods in ZACVs, due to binaries present in a stellar population which has undergone continuous, constant star formation for 1010 years. These results differ from previous work (Politano and Webbink 1988) in that an improved criterion for stability against rapid mass transfer by the secondary to the white dwarf has been used. A brief outline of the method and key assumptions made in this calculation is given in Politano and Webbink (1988).

The white dwarf mass distribution of ZACVs (shown in Figure 1) contains two components: systems with helium white dwarfs and systems with C-0 white dwarfs. Systems with helium white dwarfs comprise slightly greater than 50% of all ZACVs. The helium white dwarfs have masses which range from 0.27 to 0.46 solar mass. The C-0 white dwarfs have masses which range from 0.54 solar mass up to the Chandrasekhar mass. (Note: systems with O-Ne-Mg white dwarfs are not distinguished from systems with C-0 white dwarfs in this calculation. Presumably, these O-Ne-Mg systems comprise the upper end of the white dwarf mass distribution.)
IR Observations of the Symbiotic Nova HM Sagittae
Authors: Taranova O.G. , Yudin B.F.
Published: July 2016

The infrared photometry of the symbiotic nova HM Sge, with a Mira variable as a cool component, shows that since 1983 its mean IR brightness began to decrease from the previous post-outburst level (Figure 1). In 1988 the mean J magnitude was already about 1 mag fainter than it had been until 1983.

An analysis of the photometric observations shows that the decrease in the mean IR light level of HM Sge may be understood in the framework of the commonly accepted model of this binary stellar system (Taranova and Yudin 1983), if we suggest that the Mira variable and the inner parts of its circumstellar envelope (RMira envolope~ 3×l014 cm; τdust ≲ 1 at 1.25 µm until 1983) were gradually obscured by the dust originated between them and the observer.
The nova type outburst of the symbiotic star AS 296
Authors: Munari Ulisse
Published: July 2016

The photometric and spectroscopic evolutions, displayed by AS 296 since the June 1988 outburst ([1]), are presented and discussed. The main features of the model outlined by [2], [3] and [4], are confirmed and further developped. An orbital period of about 3 years is inferred from Hα modulation (see [5]).

The outburst originated from a TNR event in the accreted envelope of a WD. The IUE and optical spectroscopic evolution agrees with the expected scenario for degenerate conditions in the accreted material, while the high quiescence luminosity of the WD would indicate nondegenerate conditions.

The late type giant passed unchanged the outburst. Also the region of Hα formation was not touched by the eruption.

After one year the system has not yet reached the quiescence again. The photometric evolution displayed by AS 296 up to June 15, 1989 is presented in Fig.1.

In Tab.1, the main features exhibited by symbiotic stars that have experienced a TNR event are summarized. The first 8 objects in the table are usually collectively called "symbiotic novae". They distinguish themselves for the very long outburst duration. At present, AS 296 appears to be a borderline case of such class, and a firm understanding needs to wait for the end of current active phase.
Observational Evidence on the Interaction of Orion Population Stars and the Interstellar Medium
Authors: Grasdalen G.
Published: July 2016

The Orion population stars are those stars which have only recently formed. It is generally accepted that these stars arose as condensations in the interstellar medium. It follows that they should show strong interactions with that material. In only one case, the nebula near T Tauri (Schwartz 1974) do we have any direct evidence for the interaction between these stars and the interstellar medium. Presumably this is because the typical interactions take place on much larger or much shorter distance scales. The long range interaction of young stars with their environment is discussed in Section II.

It is also generally agreed that Orion population stars are still enshrouded in circumstellar material. There are important questions that have yet to be answered about that material before we can begin to discuss the details of any interaction between these stars and their surroundings. These difficulties are discussed in Section III.

Finally, I have chosen four topics to discuss in somewhat more detail. My aim has been either to urge caution in accepting current interpretations or to put caution aside and suggest new possibilities.
Quasicyclic Light Changes in Three Low Mass T Tauri Stars
Authors: Mauder H.
Published: July 2016

During a photographic survey of the Chamaeleon T association in 1971/1972, evidence was found for quasiperiodic light changes of three variable stars, see Mauder and Sosna (1975). The period of 6.2 days for SY Cha is well seen, the periods of 7 days for VZ Cha and of 8 days for TW Cha are less pronounced. Intrinsic variations are present in addition to the cyclic variations. The three stars were classified by Hoffmeister (1963) as T Tauri type stars from their light variations. Objective prism spectra obtained by Henize and Mendoza (1973) confirm this classification, they found conspicuous emission lines. For SY Cha and TW Cha they got slit spectra, too, which show the typical veiling. The stars SY Cha, TW Cha and VZ Cha have been observed in the UBV system from 1974 March 12 until 1974 March 22, using the ESO standard photometer. In Figures 1 - 3 the light and colour curves are given for SY Cha, TH Cha and VZ Cha. Each point is a mean of generally 8 to 12 integrations, each integration lasting 5 seconds.
The Frequency of YY Orionis Objects among the T Tauri Stars
Authors: Appenzeller I.
Published: July 2016

A list of 24 T Tauri stars belonging to the YY Orionis subclass is presented. From a statistical analysis it is estimated that at least 75% (and possibly all) UV-excess T Tauri stars are YY Orionis stars. Since about 50% of all known T Tauri stars show a strong UV-excess, the percentage of YY Orionis stars among the T Tauri stars is estimated to be 40 - 50%. This relative high percentage is in good agreement with the present theory of the formation and early evolution of low mass stars.
Simultaneous Spectroscopic and Photometric Observations of the YY Orionis Star S CrA
Authors: Mundt R. , Wolf B.
Published: July 2016

The YY Orionis stars are a subclass of the T Tauri stars which show in their spectra evidence for infailing envelopes. They are interpreted as protostars in the final stages of their hydrodynamical evolution (Walker 1972, Appenzeller and Wolf 1977, Wolf et al. 1977).

To get more information about the behaviour of these highly variable stars simultaneous spectroscopic and photoelectric (UBV) observations have been carried out in July 1977 at the ESO observatory at La Silla. Such observations of YY Orionis stars have never been done before.

The most frequently observed star during our run was the bright YY Orionis star S CrA. The observational material is still under evaluation and therefore only some preliminary results are presented here. A more extended description and discussion of the observations will be published elsewhere (Mundt and Wolf, 1977).
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

U, 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.
Aspects of VW Hyi
Authors: Schoembs R.
Published: July 2016

A coherent sinusoidal oscillation of approximately 88 s and amplitude has been detected at the end of the long eruption of VW Hyi in December 1975. The phenomenon was observed during five nights, when the period varied between 90 and 87 s. Some runs indicate that the amplitude depends on the phase of the orbital revolution. This result favours models in which oscillations are caused by rotation of inhomogeneities in the inner disc.
Element Abundance Analyses of Novae
Authors: Williams Robert E.
Published: July 2016

The 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

The 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.
Nova Cygni 1975: A Model for the Variability of the 3 Hour Period
Authors: Fabian A.C. , Pringle J. E.
Published: July 2016

A periodic modulation in the optical flux from Nova Cygni 1975 has been observed since shortly after outburst (Tempesti 1975) and the period is known to have varied by at least a few percent (Semeniuk et al. 1976). We account for the modulation in terms of a simple geometrical model in which the wind emanating from the nova is shadowed by its binary companion (see Fabian and Pringle 1977 for a fuller account). This produces an azimuthal variation in the radius of the surface of last scattering, RS, which an observer sees as a periodic modulation of the. continuum with period roughly equal to the orbital period. Variation of the observed period is accounted for in terms of variation of the size of RS.
Observational Evidence for Mass Exchange in Close Binary Systems
Authors: Drechsel Horst , Rahe Jürgen , Wolfschmidt Gudrun , Kondo Yoji , McCluskey George E.
Published: July 2016

In 1925 a photographic search for new variable stars was begun at the Remeis-Observatory in Bamberg. Initially the sky patrol covered only the northern hemisphere, but in 1964 it was also extended to the southern sky. At the individual observing stations, the sky is systematically photographed with several wide-angle patrol cameras which are attached to the same mounting, and which have f/6 Tessar lenses of 4-inch aperture. Each camera covers a 13-by-13 degree field. The plates are usually exposed for one hour and a photographic magnitude of 14m is reached.
Young W UMa Binaries and the Interaction with their Environment
Authors: Van’t Veer F.
Published: July 2016

It is arpued that late type W UMa binaries undergo mass ejection, mainly through the second Lagragian point, which causes a steady decrease of their mass ratio m2/m1. This makes it reasonable to believe that the W UMa stage is a state of transition between T Tau and normal main sequence stars.
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

The 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

The 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

The 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.
8. Comet Halley and Nongravitational Forces
Authors: Yeomans D. K.
Published: July 2016

The motion of Comet Halley is investigated over the 1607-1911 interval. The required nongravitational force model was found to be most consistent with a rocket-type thrust from the vaporization of water-ice in the comet’s nucleus. The nongravitational effects are time-independent over the investigated interval.
9. Radio Observations of the OH Radical in Comets Kobayashi-Berger-Milon (1975h) and West (1975n)
Authors: Gerard E. , Biraud F. , Crovisier J. , Kazes I. , Milet B.
Published: July 2016

The radio observations of the 18 cm wavelength OH main lines in comets Kobayashi-Berger-Milon (1975 h) and West (1975 n) confirm the model of ultraviolet pumping by the sun, that we proposed to explain our previous observations of comet Kohoutek (1973 f). The OH scale length in (1975 n) is at least 106 km at a heliocentric distance of 1 AU, in agreement with that for (1973 f).
3. An Alternate Interpretation of the Oort Cloud of Comets?
Authors: Kresak L.
Published: July 2016

Some problems of the current interpretation of the Oort Cloud are discussed. If observational selection is taken into account, no significant difference in physical characteristics of old and new comets is apparent, in spite of the required change in the radiation mechanism after the first passage near the Sun. The abundance of new comets puts special requirements on the relative size of the perihelion distances at which they lose their orbital characteristics and original surface properties, respectively. Stellar perturbations do not seem to be effective enough to displace the perihelia of new comets in a single revolution from the zone of insignificant planetary perturbations into the zone of detectability. Therefore, many physically new comets should appear as dynamically old, which is at variance with observational evidence. It is speculated whether the Oort Cloud really represents a reservoir of comets passing near the Sun for the first time or, alternatively, a region where the capability of building up extensive comas is being restored within periods of the order of 106 to 107 years.
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.
1. Sizes and Albedos of the Larger Asteroids
Authors: Morrison D.
Published: July 2016

The purpose of the present paper is to review all asteroid diameter measurements, current through mid-1976, and to combine them in a consistent way to give the best available estimates for a sample totalling 187 objects. From these diameters it is possible to determine the size-distributions of minor planets down to diameters of 50 km in the inner belt and 100 km in the outer belt. The associated albedos further indicate the distribution of objects of the C, S, and M classes throughout the belt.
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.
7. The Physical basis of the Polarimetri Method for Deriving Asteroid Albedos
Authors: Gehrels T.
Published: July 2016

Physical interpretations of negative polarization and opposition effect confirm the existence of a surface layer on the asteroids of their own dust. Future work should establish whether the impacting grains are cometary or asteroidal/meteoritic.
8. Microwave Brightnesses of 1 Ceres and 4 Vesta
Authors: Conklin E. K. , Ulich B. L. , Dickel J. R. , Ther D. T.
Published: July 2016

The brightnesses of Ceres and Vesta were observed at 3 mm wavelength. For Ceres, pure rock cannot reproduce the observed values, and a dust layer is required, much similar to lunar material. For Vesta, its different thermal characteristics appear to require a more compacted layer of material on its surface.
2. Evidence for 26Al in the Solar System
Authors: Papanastassiou D. A. , Lee T. , Wasserburg G. J.
Published: July 2016

We review the evidence for the presence of short lived 26Al (τ1/2 = 0.72 × 106 years) in the early solar system. Large excesses of 26Mg of up to 5% have been found in Ca-Al rich inclusions of the Allende meteorite. The Mg excesses correlate well with 27Al/24Mg and in two cases they are found in high purity separates of coarse grained Al-rich minerals which tend to exclude Mg. The data demonstrate that 26Al was present in the early solar system. Mechanisms for addition of 26Al to the solar nebula or for production within an active solar system are required within a few million years of condensation of small (centimeter sized) objects. The 26Al abundance in Allende inclusions is high enough to provide for effective melting of kilometer size bodies or larger, if such bodies accreted early enough (a few million years) to incorporate the 26Al.
4. On the Early Thermal History of Chondritic Asteroids Derived by 244-Plutonium Fission Track Thermometry
Authors: Pellas P. , Storzer D.
Published: July 2016

Cooling curves were determined for ordinary chondrites within the time- and temperature intervals from ~4.6 to ~4.1 × 109 years and ~1400 K to 300 K respectively. This was done by analyzing the 244-plutonium fission track record in whitlockite and adjacent mineral track detectors. The resulting cooling rates constrain the sizes of the parent asteroids to ~120 - 200 km in radius. These dimensions together with the fact that chondrites had never been molten, suggest lower 26Al/27Al initial ratios for ordinary chondritic than for Allende refractory materials.
2. Meteoritic Magnetism: Implications for Parent Bodies of Origin
Authors: Brecher A.
Published: July 2016

Recent progress in studying and understanding the magnetic record of meteorites is reviewed. Magnetic data are not compatible with the simple picture of a single planetary parent-body with core-mantle structure and a dynamo-generated magnetic field, as earlier envisaged by Soviet colleagues. The strong preterrestrial magnetization of iron meteorites, previously believed to have been acquired during cooling in parent-body fields of -.6 Oe, has now been shown to be probably a spontaneous moment, directionally controlled by the octahedral Ni-Fe structure. For each class of meteorites, the magnetic record is basically in accord with conclusions based on chemical-mineralogical-petrologic characteristics. For example, the complex remanence of brecciated achondrites bears no record of their primary igneous differentiation, but only of multiple brecciation events. Similarly, the unreilites show the expected magnetic imprint of shock-metamorphism at impact. Although systematic trends were found among ordinary chondrites groups, allowing for a rudimentary magnetic classification, only very few appeared to possess a primordial remanence component, which was used to estimate parent body fields in the range 0.1 = .3 oe. Most ordinary chondrites have been magnetically affected by brecciation at formation (e.g., LL), or by metamorphism within the parent body, or individually - by shock at the breakup of the parent body. Only the carbonaceous chondrites have preserved a clear magnetic record of their formation at low-temperature (T < 500° K), in strong magnetic fields (H ≥ 1 oe). The evidence is compatible with cold condensation and aggregation of component grains either in extended, enhanced solar wind fields, or in cometary magnetic fields.
4. Parent Bodies of Iron Meteorites
Authors: Scott E. R. D.
Published: July 2016

On the basis of their chemical and mineralogical composition, 420 iron meteorites have been classified into 12 different groups. Each group seems to have come from a separate parent body. The largest group, IIIAB, probably formed an asteroidal core in a body approximately 100 km in radius, which was largely destroyed by collision 630 My ago. Another 67 analyzed irons do not belong to these groups, and may represent samples from another 20 or more bodies.
1. The Origin of Comets
Authors: Delsemme A. H.
Published: July 2016

Empirical data are confronted with different hypotheses on the origin of comets. The hypotheses are classified into three categories: 1) Comets were condensed from the solar nebula and ejected later into the Oort’s cloud. 2) Comets were condensed in situ, more or less recently, on their present trajectories; 3) Reversing the arrow of time in the traditional evolution of comets. Only two hypotheses, both from the first category, are found to be in agreement with all empirical data. The first hypothesis explains the origin of the Oort’s cloud by the perturbations of the giant planets (mainly Uranus and Neptune and possibly Pluto) on a ring of proto-comets, during the final accretion stages of the solar system. The second hypothesis uses the fast mass loss of the solar nebula to expell an outer ring of proto-comets into elliptic trajectories. Although no empirical evidence requests that the Oort’s cloud be older than a few million years, its matter is not likely to be from a different reservoir than solar system stuff, and no satisfactory theory explains its formation more recently than 4,5 billion years ago.
7. Carbon Isotope Ratio in Comets and Interstellar Matter
Authors: Vanysek V.
Published: July 2016

The 12C/13C isotope ratio in the interstellar medium and in stellar atmospheres is discussed and compared to the value found in the solar system and especially in comets. The cometary value (≥ 100) tends to be slightly above the terrestrial value (89) and is definitively higher than that for interstellar molecular clouds (about 30 to 50). This result implies that comets are not of interstellar origin.
3. Condensation and Agglomeration of Grains
Authors: Arnold J. R.
Published: July 2016

The thermodynamics of condensation from a cooling neutral gas of solar composition, have now been explored in great detail. Theories based on equilibrium condensation have had some striking successes, but there is still much to learn. There seems good reason to explore the condensation process experimentally, so far as it is possible to simulate the conditions usually assumed, to compare the results with what we see in the meteorites, and with the calculations. Preliminary results of this experimental investigation are being reported here.
10. The Role of Plasma in the Primeval Nebula
Authors: Alfven H. , Arrhenius G. , Mendis D. A.
Published: July 2016

The role of plasma and hydromagnetic processes in the primeval solar nebula is evaluated. In the light of the present knowledge of particles and fields in space it is difficult to avoid the conclusion that they must have played a crucial role in the emplacement of the material as well as its subsequent condensation into “planetesimals.” Strong evidence in support of these processes in the primeval nebula is provided by the dynamical fine structure of the asteroidal belt and the Saturnian rings. The importance of current planetary magnetospheric as well as cometary research in clarifying certain physical processes believed to have occurred in the primeval nebula is stressed.
Introductory Lecture: The Local and General Interstellar Medium
Authors: Breitschwerdt Dieter
Published: July 2016

Important 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

Observations 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

We 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

We 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

Observations 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

We 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

Based 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.
Distribution and Space Density of Soft X-ray Emitting Polars in the Solar Neighbourhood
Authors: Thomas H.-C. , Beuermann K.
Published: July 2016

The ROSAT All Sky Survey (RASS) was the first one performed with an imaging telescope in the soft X-ray regime and has led to the discovery of numerous new objects whose emission is dominated by soft X-rays. Among these are white dwarfs and a subclass of the cataclysmic variables (CVs), the Polars or AM Herculis binaries. From a pre-ROSAT census of only 17, the number of known sources of this class has increased to some 55 (Beuermann and Thomas 1993, Beuermann 1997). Distances or lower limits to the distance are available for some 35 of these, based on the detection or non-detection of the TiO-Features in their optical red spectra. The derived distances range from below 100 pc up to ~ 600 pc, implying that many of these objects are located within the “Local Bubble” of low gas density in interstellar space. As the soft X-ray emission can be reasonably well represented by blackbody emission with a typical temperature of kTbb ≃ 25 eV, spectral fits to the ROSAT PSPC spectra from either the All-Sky-Survey (RASS) or from subsequent pointed ROSAT observations allow to determine the foreground absorption column density in the direction of the polars.
Mapping Cool Gas in the ISM with ROSAT
Authors: Hutchinson I.B. , Warwick R.S. , Willingale R.
Published: July 2016

We 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.
The Volume Filling Factor of the WIM
Authors: Berkhuijsen Elly M.
Published: July 2016

A compilation of data on the volume filling factor fv of the warm ionized medium (WIM) as a function of the local electron density ne indicates that approximately fv ∝ n−1e over 4 decades. This result is expected for a fractal ISM.
Tracing Small-Scale Fluctuations in the Soft X-ray Background
Authors: Warwick R. , Hutchinson I. , Willingale R. , Kuntz K. , Snowden S.
Published: July 2016

An 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

Galactic 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

26Al 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.