Europium and lanthanum in sunspot and in the undisturbed photosphere

Line profiles of Euii 4129.7 Å and Laii 4086.7 Å were observed photoelectrically and photographically in the photosphere and within sunspots and after correction were compared with calculated profiles. The observed large hyperfine structure broadening and isotope shift of 4129.7 Å confirm the Eu origin of this line and suggest a larger Eu abundance than that recently published by Grevesse and Blanquet (1969). The line profiles within the spot may be well represented by means of the spot model of Hénoux (1969), while older spot models are not able to do it. An abundance difference between spot and photosphere has not been observed.     

Production and processing of silicates in laboratory and in space

Since their formation in the outflows of evolved stars, materials suffer in space deep chemical and physical modifications. Most abundant elements (C, N, O, Mg, Si, S and Fe) are present in dust as refractory chemical species. Among them silicates are one of the main constituents. Spectroscopic observations in various astronomical environments have shown that magnesium rich silicates are present both in amorphous and in crystalline form. An accurate interpretation of these observations requires studies on the formation of silicate dust in the atmospheres of giant stars and their evolution in the interstellar medium until their inclusion in protoplanetary disks.Many theoretical works have described the chemical and physical evolution of solids in space and their link to observable optical properties. Laboratory studies of cosmic dust analogues are needed to investigate these processes experimentally.In this work, experiments aimed at simulating the formation of silicates in space are presented. In particular, the laser ablation technique is used to produce amorphous silicates with various Si-Mg-Fe content. The analysis of their thermal evolution is presented.     

Helium and metal diffusion in the Sun and in cluster stars

In this contribution I will review the present knowledge about helium and metal diffusion efficiency in the Sun and in old cluster stars and the influence of the uncertainties still present on these mechanisms concerning the stellar characteristics in different evolutionary phases. I will also discuss the relevance of the current uncertainties on the assumed chemical composition for the main evolutionary features of population II stars.     

Past and recent changes in air and permafrost temperatures in eastern Siberia

Air and ground temperatures measured in Eastern Siberia has been compiled and analyzed. The analysis of mean annual air temperatures measured at 52 meteorological stations within and near the East-Siberian transect during the period from 1956 through 1990 demonstrates a significant and statistically significant (at 0.05 level) positive trend ranging from 0.065 to 0.59 °C/10 yr. A statistically significant (at 0.05 level) positive trend was also observed in mean annual ground temperatures for the same period. The permafrost temperature reflects changes in air temperature on a decadal time scale much better than on an interannual time scale. Generally, positive trends in mean annual ground temperatures are slightly smaller in comparison with trends in mean annual air temperatures, except for several sites where the discordance between the air and ground temperatures can be explained by the winter snow dynamics. The average trend for the entire region was 0.26 °C/10 yr for ground temperatures at 1.6 m depth and 0.29 °C/10 yr for the air temperatures. The most significant trends in mean annual air and ground temperatures were in the southern part of the transect, between 55° and 65° N. Numerical modeling of ground temperatures has been performed for Yakutsk and Tiksi for the last 70 yr. Comparing the results of these calculations with a similar time series obtained for Fairbanks and Barrow in Alaska shows that similar variations of ground temperatures took place at the same time periods in Yakutsk and Fairbanks, and in Tiksi and Barrow. The decadal and longer time scale fluctuations in permafrost temperatures were pronounced in both regions. The magnitudes of these fluctuations were on the order of a few degrees centigrade. The fluctuations of mean annual ground temperatures were coordinated in Fairbanks and Yakutsk, and in Barrow and Tiksi. However, the magnitude and timing of these fluctuations were slightly different for each of the sites.     

Sonic points and shocks in isothermal accretion and winds in Kerr geometry

This paper is devoted to the study of sonic points and shocks in stationary, axially symmetric, isothermal flows around a Kerr black hole. We first show the dependence of the location of the sonic point with the flow's angular momentum for different isothermal sound speeds. With our selected shock jump conditions, we then discuss the properties of the shock, including the location and the strength. The ambiguity regarding the shock locations is removed by stability analysis. We also find some differences between the shock in isothermal flows and that in adiabatic flows. Subject headings: accretion, accretion disks-black hole physics-hydrodynamics-relativity-shock waves.     

Oxygen isotopes in magnetite and fayalite in CV chondrites Kaba and Mokoia

Abstract— We report in situ measurements of O‐isotopic compositions of magnetite and primary and secondary olivine in the highly unequilibrated oxidized CV chondrites Kaba and Mokoia. In both meteorites, the magnetite and the secondary olivine (fayalite, Fa_90–100) have O‐isotopic compositions near the terrestrial fractionation (TF) line; the mean Δ¹⁷O (= δ¹⁷O‐0.52 × δ¹⁸O) value is about ?1%‰. In contrast, the compositions of nearby primary (chondrule), low‐FeO olivines (Fa_1–2) are well below the TF line; Δ¹⁷O values range from ?3 to ?9%‰. Krot et al. (1998) summarized evidence indicating that the secondary phases in these chondrites formed by aqueous alteration in an asteroidal setting. The compositions of magnetite and fayalite in Kaba and Mokoia imply that the O‐isotopic composition of the oxidant was near or somewhat above the TF line. In Mokoia the fayalite and magnetite differ in δ¹⁸O by ～20%‰, whereas these same materials in Kaba have virtually identical compositions. The difference between Mokoia magnetite and fayalite may indicate formation in isotopic equilibrium in a water‐rich environment at low temperatures, ～300 K. In contrast, the similar compositions of these phases in Kaba may indicate formation of the fayalite by replacement of preexisting magnetite in dry environment, with the O coming entirely from the precursor magnetite and silica. The Δ¹⁷O of the oxidant incorporated into the CV parent body (as phyllosilicates or H₂O) appears to have been much (7–8%‰) lower than that in that incorporated into the LL parent body (Choi et al, 1998), which suggests that the O‐isotopic composition of the nebular gas was spatially or temporally variable.     

Ionized helium in prominences and in the chromosphere

Quiescent prominences It is found that Heii 4686 is emitted in the same cold region of 10000 K as hydrogen, metal and neutral helium emission lines. This conclusion is based on the finding that the observed width of 4686 is the same as the calculated width of 4686. The calculated width is derived from the observed widths of hydrogen and metallic lines. The large intensity of Heii 4686 in 10000 K can be explained by the ionization of Heii due to the UV radiation below 228 Å that comes from the corona and the transition region.Loop prominences The very broad width (30 to 50 km s^–1) of 4686 for two post-flare loop prominences shows that the Heii line is emitted in hot regions different from regions of hydrogen and metal emission. From the widths of the Balmer lines and many metallic lines the kinetic temperature for one loop is found to be 16000 K in one part and 7600 K in another part. The electron densities are 10^12.0 cm^–3 and less than 10^11.0 cm^–3 respectively.Chromosphere The intensity of 4686 in the chromosphere can be interpreted in terms of a temperature of 10000 K with the ionization due to UV radiation. But, since observations of the width of 4686 are not available, a definitive conclusion for the chromosphere cannot be reached.     

Trajectories and envelopes in the repulsive two-fixed-centre problem and in the restricted three-body problem

The envelope of iso-energetic trajectories in the (repulsive) two-fixed-centre problem is derived. Our analytical calculations finally lead to a transcendental equation, only containing elliptic integrals and the Weierstraßp function, from which the envelope is constructed. The results may serve as a simple model for the boundary layer between two colliding supersonic stellar wind flows in binary systems, in which at least one of the components has a strong radiation field.Beyond this, the effect of non-inertial forces (centrifugal and Coriolis force) due to the binary's orbital motion has been estimated by a numerical analysis within the scope of the (repulsive) restricted three-body problem.All calculations have been performed for a hot model (Wolf-Rayet/O-star) binary system with a set of parameters which might be appropriate for HD 152270. The envelope may be well approximated by a hyperboloid. The non-inertial forces slightly turn the envelope against the line connecting both stars.     

Gemini observations of disks and jets in young stellar objects and in active galaxies

We present first results from the Near-infrared Integral Field Spectrograph (NIFS) located at Gemini North. For the active galaxies Cygnus A and Perseus A we observe rotationally-supported accretion disks and adduce the existence of massive central black holes and estimate their masses. In Cygnus A we also see remarkable high-excitation ionization cones dominated by photoionization from the central engine. In the T-Tauri stars HV Tau C and DG Tau we see highly-collimated bipolar outflows in the [Fe II] λ 1.644 micron line, surrounded by a slower molecular bipolar outflow seen in the H₂ lines, in accordance with the model advocated by Pyo, T.-S., et al., Astrophys. J. 570, 724 (2002).     

Variations in Abundance Enhancements in Impulsive Solar Energetic-Particle Events and Related CMEs and Flares

We study event-to-event variations in the abundance enhancements of the elements He through Pb for Fe-rich impulsive solar energetic-particle (SEP) events, and their relationship with properties of associated coronal mass ejections (CMEs) and solar flares. Using a least-squares procedure we fit the power-law enhancement of element abundances as a function of their mass-to-charge ratio A/Q to determine both the power and the coronal temperature (which determines Q) in each of 111 impulsive SEP events identified previously. Individual SEP events with the steepest element enhancements, e.g. ～?(A/Q)⁶, tend to be smaller, lower-fluence events with steeper energy spectra that are associated with B- and C-class X-ray flares, with cooler (～?2.5 MK) coronal plasma, and with narrow (°), slower (?1) CMEs. On the other hand, higher-fluence SEP events have flatter energy spectra, less-dramatic heavy-element enhancements, e.g. ～?(A/Q)³, and come from somewhat hotter coronal plasma (～?3.2 MK) associated with C-, M-, and even X-class X-ray flares and with wider CMEs. Enhancements in ³He/⁴He are uncorrelated with those in heavy elements. However, events with ³He/⁴He≥0.1 are even more strongly associated with narrow, slow CMEs, with cooler coronal plasma, and with B- and C-class X-ray flares than are other Fe-rich impulsive SEP events with smaller enhancements of ³He.     

Zirconium and hafnium in meteorites

Abstract– The ratio of the two refractory trace elements zirconium (Zr) and hafnium (Hf) in meteorites has been proposed to be uniform. The most precise value available is 34.3 ± 0.2 (1σ). It was obtained by isotope dilution ICP‐MS applied to 15 chondrites, most of which were carbonaceous chondrites, and six achondrites. We reinvestigated the case and determined Zr/Hf ratios of a broad spectrum of meteoritic samples via laser ablation ICP‐MS. Our sample suite comprised 29 chondrites and five achondrites. The main objective of the study was two‐fold: we intended to verify the accuracy and precision of a relatively fast and inexpensive sample preparation method combined with expeditious laser ablation ICP‐MS techniques. Furthermore, we were looking into the possibility of systematic fine‐scale Zr/Hf variations among bulk meteoritic matter of different classes. The applied fusion technique together with laser ablation ICP‐MS turned out to be well suited to determine relative refractory trace element abundances. Absolute Zr/Hf ratios yield uncertainties of approximately 4% (1σ). As opposed to the most recent findings, we observed variable Zr/Hf ratios in different meteorites ranging from approximately 28 to approximately 38. Our value for Orgueil (CI1) is 34.0 ± 0.3 (1σ). Including literature data, we propose a solar system value of 34.1 ± 0.3. Our data also suggest that H chondrites tend to exhibit higher Zr/Hf ratios (average of 35.6 ± 0.5 [1σ]) while EL6 chondrites rather show low values (average of 30.8 ± 0.6 [1σ]). In addition to examining Zr/Hf ratios, we also explored the content of refractory major elements in different meteorite groups. Here, we found that EL6 chondrites often show very low Ca/Al ratios. The CI1 value for CaO/Al₂O₃ is 0.804. EL6 chondrites, however, display ratios as low as approximately 0.3. While the variation in Zr/Hf can be explained by fractional condensation processes in the early solar nebula, the observed low Ca/Al ratios in EL6 chondrites are probably attributable to deficits in oldhamite (CaS).     

Chaos in Relativity and Cosmology

Chaos appears in various problems of Relativity and Cosmology. Here we discuss (a) the Mixmaster Universe model, and (b) the motions around two fixed black holes. (a) The Mixmaster equations have a general solution (i.e. a solution depending on 6 arbitrary constants) of Painlevé type, but there is a second general solution which is not Painlevé. Thus the system does not pass the Painlevé test, and cannot be integrable. The Mixmaster model is not ergodic and does not have any periodic orbits. This is due to the fact that the sum of the three variables of the system (α + β + γ) has only one maximum for τ = τ_m and decreases continuously for larger and for smaller τ. The various Kasner periods increase exponentially for large τ. Thus the Lyapunov Characteristic Number (LCN) is zero. The "finite time LCN" is positive for finite τ and tends to zero when τ → ∞. Chaos is introduced mainly near the maximum of (α + β + γ). No appreciable chaos is introduced at the successive Kasner periods, or eras. We conclude that in the Belinskii-Khalatnikov time, τ, the Mixmaster model has the basic characteristics of a chaotic scattering problem. (b) In the case of two fixed black holes M₁ and M₂ the orbits of photons are separated into three types: orbits falling into M₁ (type I), or M₂ (type II), or escaping to infinity (type III). Chaos appears because between any two orbits of different types there are orbits of the third type. This is a typical chaotic scattering problem. The various types of orbits are separated by orbits asymptotic to 3 simple unstable orbits. In the case of particles of nonzero rest mass we have intervals where some periodic orbits are stable. Near such orbits we have order. The transition from order to chaos is made through an infinite sequence of period doubling bifurcations. The bifurcation ratio is the same as in classical conservative systems. This revised version was published online in July 2006 with corrections to the Cover Date.     

Neutrinos and Non-proliferation in Europe

The main effort in Europe to evaluate the interest for IAEA of neutrinos detectors close to nuclear power stations is made within the Double Chooz experiments. Specific simulation of diversion scenarios as well as new experimental measurements of neutrinos emitted are underway. On behalf of a collective work by S. Cormon, M. Fallot, H. Faust, T. Lasserre, A. Letourneau, D. Lhuillier, V. Sinev from DAPNIA, Subatech and ILL.     

Molecules and Dust in Supernovae

Observations of molecules and dust in supernova SN 1987a and SN 1995ad are summarised and the inferred masses of CO and SiO are presented. The chemistry is used to argue that macroscopic mixing occurred in which the interpenetrating clumps in the ejecta retained their microscopic integrity. An explanation of the anomalous temperature structure is advanced. Molecular candidates for some of the unidentified spectral features are proposed. This revised version was published online in September 2006 with corrections to the Cover Date.     

Nonthermal particles and photons in starburst regions and superbubbles

Starforming factories in galaxies produce compact clusters and loose associations of young massive stars. Fast radiation-driven winds and supernovae input their huge kinetic power into the interstellar medium in the form of highly supersonic and superalfvenic outflows. Apart from gas heating, collisionless relaxation of fast plasma outflows results in fluctuating magnetic fields and energetic particles. The energetic particles comprise a long-lived component which may contain a sizeable fraction of the kinetic energy released by the winds and supernova ejecta and thus modify the magnetohydrodynamic flows in the systems. We present a concise review of observational data and models of nonthermal emission from starburst galaxies, superbubbles, and compact clusters of massive stars. Efficient mechanisms of particle acceleration and amplification of fluctuating magnetic fields with a wide dynamical range in starburst regions are discussed. Sources of cosmic rays, neutrinos and multi-wavelength nonthermal emission associated with starburst regions including potential galactic “PeVatrons” are reviewed in the global galactic ecology context.     

Spin-up and spin-down in intermediate polars and X-ray pulsars

The accretion torque theory of Wang (1987) is applied to the spin periods of intermediate polars and X-ray pulsars. It is shown that, if the primaries are spinning near their equilibrium values, the range of positive and negative values ofP/P observed in intermediate polars is readily understood in terms of relatively small variations of mass transfer rateM of the kind generated either by long term (10³ yr) cycling ofM suggested by the nova hibernation model, or by the short term (10 yr) variations caused by magnetic cycling in the secondary stars. The variations in spin rates of the disc-fed X-ray pulsars Her X-1 and Cen X-3 can also be accounted for by the latter process.     

Asymmetry and inhomogeneity in proto- and young planetary nebulae

I study some effects of aspherical mass loss during the last stages of the asymptotic giant branch (AGB) on the appearance of proto-planetary nebulae (proto-PNs) and young PNs. The aspherical mass loss can be small-scale inhomogeneities, and/or axially symmetric mass-loss geometry. I first examine the role of the dust opacity in the optical band on the appearance of proto-PNs. I conclude that large optical depths will be found in proto-PNs that are post-AGB stars having high equatorial mass-loss rates, which require a stellar binary companion for their existence. In these cases light from the central star will reach larger distances along and near the polar directions, leading to the appearance of an elongated reflection nebula. These proto-PNs will become bipolar PNs, i.e., PNs with two lobes and an equatorial waist between them, or extreme ellipticals, e.g., a ring but no lobes on the two sides of the equatorial plane. I then derive the conditions for the enhancement of non-radial density inhomogeneity by the propagation of the ionization front at the early PN stages. The ionization will proceed faster in the radial direction along low-density regions. The low-density regions will be heated earlier, and they will expand as a result of their higher pressures, reducing further their densities. The opposite occurs in high-density regions. The condition for this ionization instability to develop is that the ionization time difference between two directions at the same radius is longer than the sound crossing time between these two regions. This condition for the ionization front instability can be expressed as a condition on the mass-loss rate inhomogeneity, i.e., its dependence on direction.     

On core-collapse supernovae in normal and in Seyfert galaxies

This paper estimates the relative frequency of different types of core-collapse supernovae, in terms of the ratio between the number of Type Ib–Ic and of Type II supernovae. We estimate independently for all normal and Seyfert galaxies whose radial velocity is ≤14 000 km s⁻¹, and which had at least one supernova event recorded in the Asiago catalogue from 1986 January to 2000 August. We find that the ratio is  ≈0.23±0.05  in normal galaxies. This value is consistent with constant star formation rate and with a Salpeter initial mass function and an average binary rate ≈50 per cent. On the contrary, Seyfert galaxies exceed the ratio in normal galaxies by a factor ≈4 at a confidence level ≳2 σ . A caveat is that the numbers for Seyferts are still small (six of Type Ib–Ic and six of Type II supernovae discovered as yet). Assumed to be real, this excess of Type Ib/c supernovae may indicate a burst of low-age star formation  ( τ ≲20 Myr)  , a high incidence of binary systems in the inner regions  ( r ≲0.4 R ₂₅)  of Seyfert galaxies, or a top-loaded mass function.