Author name code: gustafsson ADS astronomy entries on 2022-09-14 author:"Gustafsson, Bengt" ------------------------------------------------------------------------ Title: Chemical Tracing and the Origin of Carbon in the Galactic Disk Authors: Gustafsson, Bengt Bibcode: 2022Univ....8..409G Altcode: A basic problem in studies of the evolution of chemical elements in galaxies is the uncertainties in the yields of elements produced by different types of stars. The possibilities of tracing the sites producing chemical elements and corresponding yields in stellar populations by studying ratios of abundances in stars of different ages and metallicities, with an approach with minimal assumptions concerning the yields, is explored by means of simple models of Galactic chemical evolution. Elemental abundances of carbon and oxygen, obtained by recent observations of samples of solar-type stars with estimated ages in the thin disk of the Galaxy, are analysed. Constraints on the yields from winds of intermediate-mass stars and of hot massive stars, including core-collapse supernovae, are derived. It is found that a dominating contribution of carbon from massive stars is most probable, although stars in the mass interval of two to three solar masses may have provided some amounts of carbon in the Sun. The results are consistent with those obtained by using theoretical yields and more elaborate models of Galactic evolution. The uncertainties as regards the mixing of stellar populations due to migration of stars in the Galactic disk may be important for the conclusions. Variations in the star formation rates, lack of chemical homogeneity in the Galactic gas, the inflow of gas from the intergalactic space and possible variations in the Initial mass function may also limit conclusions about the sites and their yields. Very accurate abundance ratios and the determination of stellar ages provide further important constraints on the yields. Title: Iron-Phosphorus Feedbacks Drive Multidecadal Oscillations in Baltic Sea Hypoxia Authors: Jilbert, Tom; Gustafsson, Bo G.; Veldhuijzen, Simon; Reed, Daniel C.; van Helmond, Niels A. G. M.; Hermans, Martijn; Slomp, Caroline P. Bibcode: 2021GeoRL..4895908J Altcode: Hypoxia has occurred intermittently in the Baltic Sea since the establishment of brackish-water conditions at ∼8,000 years B.P., principally as recurrent hypoxic events during the Holocene Thermal Maximum (HTM) and the Medieval Climate Anomaly (MCA). Sedimentary phosphorus release has been implicated as a key driver of these events, but previous paleoenvironmental reconstructions have lacked the sampling resolution to investigate feedbacks in past iron-phosphorus cycling on short timescales. Here we employ Laser Ablation (LA)-ICP-MS scanning of sediment cores to generate ultra-high resolution geochemical records of past hypoxic events. We show that in-phase multidecadal oscillations in hypoxia intensity and iron-phosphorus cycling occurred throughout these events. Using a box model, we demonstrate that such oscillations were likely driven by instabilities in the dynamics of iron-phosphorus cycling under preindustrial phosphorus loads, and modulated by external climate forcing. Oscillatory behavior could complicate the recovery from hypoxia during future trajectories of external loading reductions. Title: Impact of natural re-oxygenation on the sediment dynamics of manganese, iron and phosphorus in a euxinic Baltic Sea basin Authors: Hermans, Martijn; Lenstra, Wytze K.; van Helmond, Niels A. G. M.; Behrends, Thilo; Egger, Matthias; Séguret, Marie J. M.; Gustafsson, Erik; Gustafsson, Bo G.; Slomp, Caroline P. Bibcode: 2019GeCoA.246..174H Altcode: The Baltic Sea is characterized by the largest area of hypoxic (oxygen (O2) < 2 mg L-1) bottom waters in the world's ocean induced by human activities. Natural ventilation of these O2-depleted waters largely depends on episodic Major Baltic Inflows from the adjacent North Sea. In 2014 and 2015, two such inflows led to a strong rise in O2 and decline in phosphate (HPO42-) in waters below 125 m depth in the Eastern Gotland Basin. This provided the opportunity to assess the impact of such re-oxygenation events on the cycles of manganese (Mn), iron (Fe) and phosphorus (P) in the sediment for the first time. We demonstrate that the re-oxygenation induced the activity of sulphur (S)-oxidising bacteria, known as Beggiatoaceae in the surface sediment where a thin oxic and suboxic layer developed. At the two deepest sites, strong enrichments of total Mn and to a lesser extent Fe oxides and P were observed in this surface layer. A combination of sequential sediment extractions and synchrotron-based X-ray spectroscopy revealed evidence for the abundant presence of P-bearing rhodochrosite and Mn(II) phosphates. In contrast to what is typically assumed, the formation of Fe oxides in the surface sediment was limited. We attribute this lack of Fe oxide formation to the high flux of reductants, such as sulphide, from deeper sediments which allows Fe(II) in the form of FeS to be preserved and restricts the penetration of O2 into the sediment. We estimate that enhanced P sequestration in surface sediments accounts for only ∼5% of water column HPO42- removal in the Eastern Gotland Basin linked to the recent inflows. The remaining HPO42- was transported to adjacent areas in the Baltic Sea. Our results highlight that the benthic O2 demand arising from the accumulation of organic-rich sediments over several decades, the legacy of hypoxia, has major implications for the biogeochemical response of euxinic basins to re-oxygenation. In particular, P sequestration in the sediment in association with Fe oxides is limited. This implies that artificial ventilation projects that aim at removing water column HPO42- and thereby improving water quality in the Baltic Sea will likely not have the desired effect. Title: Dust cleansing of star-forming gas. II. Did late accretion flows change the chemical composition of the solar atmosphere? Authors: Gustafsson, Bengt Bibcode: 2018A&A...620A..53G Altcode: 2018arXiv180902361G
Aims: The possibility that the chemical composition of the solar atmosphere has been affected by radiative dust cleansing of late and weak accretion flows by the proto-sun itself is explored.
Methods: Estimates, using semi-analytical methods and numerical simulations of the motion of dust grains in a collapsing non-magnetic and non-rotating gas sphere with a central light source are made in order to model possible dust-cleansing effects.
Results: Our calculations indicate that the amount of cleansed material may well be consistent with the abundance differences observed for the Sun when compared with solar-like stars and with the relations found between these differences and the condensation temperature of the element.
Conclusions: It seems quite possible that the proposed mechanism produced the significant abundance effects observed for the Sun, provided that late and relatively weak accretion did occur. The effects of cleansing may, however, be affected by outflows from the Sun, the existence and dynamics of magnetic fields and of the accretion disk, and the possible presence and location of the early Sun in a rich stellar cluster. Title: High-precision stellar abundances of the elements: methods and applications Authors: Nissen, Poul Erik; Gustafsson, Bengt Bibcode: 2018A&ARv..26....6N Altcode: 2018arXiv181006535N Efficient spectrographs at large telescopes have made it possible to obtain high-resolution spectra of stars with high signal-to-noise ratio and advances in model atmosphere analyses have enabled estimates of high-precision differential abundances of the elements from these spectra, i.e. with errors in the range 0.01-0.03 dex for F, G, and K stars. Methods to determine such high-precision abundances together with precise values of effective temperatures and surface gravities from equivalent widths of spectral lines or by spectrum synthesis techniques are outlined, and effects on abundance determinations from using a 3D non-LTE analysis instead of a classical 1D LTE analysis are considered. The determination of high-precision stellar abundances of the elements has led to the discovery of unexpected phenomena and relations with important bearings on the astrophysics of galaxies, stars, and planets, i.e. (i) Existence of discrete stellar populations within each of the main Galactic components (disk, halo, and bulge) providing new constraints on models for the formation of the Milky Way. (ii) Differences in the relation between abundances and elemental condensation temperature for the Sun and solar twins suggesting dust-cleansing effects in proto-planetary disks and/or engulfment of planets by stars; (iii) Differences in chemical composition between binary star components and between members of open or globular clusters showing that star- and cluster-formation processes are more complicated than previously thought; (iv) Tight relations between some abundance ratios and age for solar-like stars providing new constraints on nucleosynthesis and Galactic chemical evolution models as well as the composition of terrestrial exoplanets. We conclude that if stellar abundances with precisions of 0.01-0.03 dex can be achieved in studies of more distant stars and stars on the giant and supergiant branches, many more interesting future applications, of great relevance to stellar and galaxy evolution, are probable. Hence, in planning abundance surveys, it is important to carefully balance the need for large samples of stars against the spectral resolution and signal-to-noise ratio needed to obtain high-precision abundances. Furthermore, it is an advantage to work differentially on stars with similar atmospheric parameters, because then a simple 1D LTE analysis of stellar spectra may be sufficient. However, when determining high-precision absolute abundances or differential abundance between stars having more widely different parameters, e.g. metal-poor stars compared to the Sun or giants to dwarfs, then 3D non-LTE effects must be taken into account. Title: Dust cleansing of star-forming gas. I. Has radiation from bright stars affected the chemical composition of the Sun and M 67? Authors: Gustafsson, Bengt Bibcode: 2018A&A...616A..91G Altcode: 2018arXiv180500547G
Aims: We explore the possibility that solar chemical composition, as well as the similar composition of the rich open cluster M 67, have been affected by dust cleansing of the presolar or precluster cloud due to the radiative forces from bright early-type stars in its neighbourhood.
Methods: We estimate possible cleansing effects using semi-analytical methods, which are essentially based on momentum conservation.
Results: Our calculations indicate that the amounts of cleansed neutral gas are limited to a relatively thin shell surrounding the H II region around the early-type stars.
Conclusions: It seems possible that the proposed mechanism acting in individual giant molecular clouds may produce significant abundance effects for masses corresponding to single stars or small groups of stars. The effects of cleansing are, however, severely constrained by the thinness of the cleansed shell of gas and by turbulence in the cloud. This is why the mechanism can hardly be important in cleansing masses corresponding to rich clusters, such as the mass of the original M 67. Title: The destruction of an Oort Cloud in a rich stellar cluster Authors: Nordlander, T.; Rickman, H.; Gustafsson, B. Bibcode: 2017A&A...603A.112N Altcode: 2017arXiv170403341N Context. It is possible that the formation of the Oort Cloud dates back to the earliest epochs of solar system history. At that time, the Sun was almost certainly a member of the stellar cluster where it was born. Since the solar birth cluster is likely to have been massive (103-104ℳ⊙), and therefore long-lived, an issue concerns the survival of such a primordial Oort Cloud.
Aims: We have investigated this issue by simulating the orbital evolution of Oort Cloud comets for several hundred Myr, assuming the Sun to start its life as a typical member of such a massive cluster.
Methods: We have devised a synthetic representation of the relevant dynamics, where the cluster potential is represented by a King model, and about 20 close encounters with individual cluster stars are selected and integrated based on the solar orbit and the cluster structure. Thousands of individual simulations are made, each including 3000 comets with orbits with three different initial semi-major axes.
Results: Practically the entire initial Oort Cloud is found to be lost for our choice of semi-major axes (5000-20 000 au), independent of the cluster mass, although the chance of survival is better for the smaller cluster, since in a certain fraction of the simulations the Sun orbits at relatively safe distances from the dense cluster centre.
Conclusions: For the range of birth cluster sizes that we investigate, a primordial Oort Cloud will likely survive only as a small inner core with semi-major axes ≲3000 au. Such a population of comets would be inert to orbital diffusion into an outer halo and subsequent injection into observable orbits. Some mechanism is therefore needed to accomplish this transfer, in case the Oort Cloud is primordial and the birth cluster did not have a low mass. From this point of view, our results lend some support to a delayed formation of the Oort Cloud, that occurred after the Sun had left its birth cluster. Title: A grid of MARCS model atmospheres for late-type stars. II. S stars and their properties Authors: Van Eck, Sophie; Neyskens, Pieter; Jorissen, Alain; Plez, Bertrand; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt; Jørgensen, Uffe Gråe; Nordlund, Åke Bibcode: 2017A&A...601A..10V Altcode: S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing asymptotic giant branch. A grid of MARCS model atmospheres has been computed for S stars, covering the range 2700 ≤ Teff(K) ≤ 4000, 0.50 ≤ C/O ≤ 0.99, 0 ≤ log g ≤ 5, [Fe/H] = 0., -0.5 dex, and [s/Fe] = 0, 1, and 2 dex (where the latter quantity refers to the global overabundance of s-process elements). The MARCS models make use of a new ZrO line list. Synthetic spectra computed from these models are used to derive photometric indices in the Johnson and Geneva systems, as well as TiO and ZrO band strengths. A method is proposed to select the model best matching any given S star, a non-trivial operation since the grid contains more than 3500 models covering a five-dimensional parameter space. The method is based on the comparison between observed and synthetic photometric indices and spectral band strengths, and has been applied on a vast subsample of the Henize sample of S stars. Our results confirm the old claim by Piccirillo (1980, MNRAS, 190, 441) that ZrO bands in warm S stars (Teff>3200 K) are not caused by the C/O ratio being close to unity, as traditionally believed, but rather by some Zr overabundance. The TiO and ZrO band strengths, combined with V-K and J-K photometric indices, are used to select Teff, C/O, [Fe/H] and [s/Fe]. The Geneva U-B1 and B2-V1 indices (or any equivalent) are good at selecting the gravity. The defining spectral features of dwarf S stars are outlined, but none is found among the Henize S stars. More generally, it is found that, at Teff = 3200 K, a change of C/O from 0.5 to 0.99 has a strong impact on V-K (2 mag). Conversely, a range of 2 mag in V-K corresponds to a 200 K shift along the (Teff, V-K) relationship (for a fixed C/O value). Hence, the use of a (Teff, V-K) calibration established for M stars will yield large errors for S stars, so that a specific calibration must be used, as provided in the present paper. Using the atmospheric parameters derived by our method for the sample of Henize S stars, we show that the extrinsic-intrinsic dichotomy among S stars reveals itself very clearly as a bimodal distribution in the effective temperatures. Moreover, the increase of s-process element abundances with increasing C/O ratios and decreasing temperatures is apparent among intrinsic stars, confirming theoretical expectations.

Based on observations carried out at the European Southern Observatory (ESO, La Silla, Chile; program 58.E-0942), on the Swiss 70 cm telescope (La Silla, Chile) and on the Mercator telescope (La Palma, Spain).The MARCS S star model atmospheres will be archived on the MARCS website: http://marcs.astro.uu.seFull Tables 2 and 3 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/601/A10 Title: Sun-like stars unlike the Sun: Clues for chemical anomaliesof cool stars Authors: Adibekyan, V.; Delgado-Mena, E.; Feltzing, S.; González Hernández, J. I.; Hinkel, N. R.; Korn, A. J.; Asplund, M.; Beck, P. G.; Deal, M.; Gustafsson, B.; Honda, S.; Lind, K.; Nissen, P. E.; Spina, L. Bibcode: 2017AN....338..442A Altcode: 2017arXiv170105737A We present a summary of the splinter session "Sun-like stars unlike the Sun" that was held on June 9, 2016, as part of the Cool Stars 19 conference (Uppsala, Sweden), in which the main limitations (in the theory and observations) in the derivation of very precise stellar parameters and chemical abundances of Sun-like stars were discussed. The most important and most debated processes that can produce chemical peculiarities in solar-type stars were outlined and discussed. Finally, in an open discussion between all the participants, we tried to identify new pathways and prospects toward future solutions of the currently open questions. Title: VizieR Online Data Catalog: A grid of MARCS model atmospheres for S stars (Van Eck+, 2017) Authors: van Eck, S.; Neyskens, P.; Jorissen, A.; Plez, B.; Edvardsson, B.; Eriksson, K.; Gustafsson, B.; Jorgensen, U. G.; Nordlund, A. Bibcode: 2017yCat..36010010V Altcode: Johnson and Geneva (G) photometric indices and band indices measured on the observed Henize S stars.

(3 data files). Title: 67P/C-G inner coma dust properties from 2.2 au inbound to 2.0 au outbound to the Sun Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Ivanovski, S.; Green, S. F.; Rietmeijer, F. J. M.; Colangeli, L.; Palumbo, P.; Sordini, R.; Ferrari, M.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Weissman, P.; Gruen, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Ortiz, J. L.; Jeronimo, J. M.; Leese, M. R.; Herranz, M.; Liuzzi, V.; Lopez-Jimenez, A. C. Bibcode: 2016MNRAS.462S.210D Altcode: 2016MNRAS.tmp.1514D GIADA (Grain Impact Analyzer and Dust Accumulator) on-board the Rosetta space probe is designed to measure the momentum, mass and speed of individual dust particles escaping the nucleus of comet 67P/Churyumov-Gerasimenko (hereafter 67P). From 2014 August to 2016 June, Rosetta escorted comet 67P during its journey around the Sun. Here, we focus on GIADA data taken between 2015 January and 2016 February which included 67P's perihelion passage. To better understand cometary activity and more specifically the presence of dust structures in cometary comae, we mapped the spatial distribution of dust density in 67P's coma. In this manner, we could track the evolution of high-density regions of coma dust and their connections with nucleus illumination conditions, namely tracking 67P's seasons. We also studied the link between dust particle speeds and their masses with respect to heliocentric distance, I.e. the level of cometary activity. This allowed us to derive a global and a local correlation of the dust particles' speed distribution with respect to the H2O production rate. Title: VizieR Online Data Catalog: Kepler-10 chemical composition (Liu+, 2016) Authors: Liu, F.; Yong, D.; Asplund, M.; Ramirez, I.; Melendez, J.; Gustafsson, B.; Howes, L. M.; Roederer, I. U.; Lambert, D. L.; Bensby, T. Bibcode: 2016yCat..74562636L Altcode: We obtained high resolution and high SNR spectra with the Canada-France-Hawaii Telescope (CFHT), the Hobby-Eberly Telescope (HET) and the Magellan Clay Telescope.

We observed Kepler-10 with the Echelle SpectroPolarimetric Device for the Observation of Stars at the CFHT during 2013 June. The spectral revolving power is 68000 and the spectral range is 3800-8900Å.

We also observed Kepler-10 with the High Resolution Spectrograph (HRS) on the HET at McDonald Observatory during 2011 May. A total integration time of 6.8h was needed to achieve SNR>350 per pixel. The spectrum has a spectral resolving power of 60000 and covers 4100-7800Å, with a gap of about 100Å around 6000Å.

(4 data files). Title: Gravitational Scattering In The Galactic Disk And The Old High-Altitude Open Clusters Authors: Gustafsson, Bengt Bibcode: 2016diga.confE..37G Altcode: By means of numerical simulations we have investigated the possibility that the observed heating of the Thin Disk and the existence of old high-altitude open clusters are both the result of gravitational scattering by GMCs and other inhomogeneities in the Galactic potential. We find consistency between model results and observations, but the results are very dependent on the structure adopted for the GMCs and their surroundings. Title: Gravitational scattering of stars and clusters and the heating of the Galactic disk Authors: Gustafsson, Bengt; Church, Ross P.; Davies, Melvyn B.; Rickman, Hans Bibcode: 2016A&A...593A..85G Altcode: 2016arXiv160502965G Context. Could the velocity spread, increasing with time, in the Galactic disk be explained as a result of gravitational interactions of stars with giant molecular clouds (GMCs) and spiral arms? Do the old open clusters high above the Galactic plane provide clues to this question?
Aims: We explore the effects on stellar orbits of scattering by inhomogeneities in the Galactic potential due to GMCs, spiral arms and the Galactic bar, and whether high-altitude clusters could have formed in orbits closer to the Galactic plane and later been scattered.
Methods: Simulations of test-particle motions are performed in a realistic Galactic potential. The effects of the internal structure of GMCs are explored. The destruction of clusters in GMC collisions is treated in detail with N-body simulations of the clusters.
Results: The observed velocity dispersions of stars as a function of time are well reproduced. The GMC structure is found to be significant, but adequate models produce considerable scattering effects. The fraction of simulated massive old open clusters, scattered into orbits with |z| > 400 pc, is typically 0.5%, in agreement with the observed number of high-altitude clusters and consistent with the present formation rate of massive open clusters.
Conclusions: The heating of the thin Galactic disk is well explained by gravitational scattering by GMCs and spiral arms, if the local correlation between the GMC mass and the corresponding voids in the gas is not very strong. Our results suggest that the high-altitude metal-rich clusters were formed in orbits close to the Galactic plane and later scattered to higher orbits. It is possible, though not very probable, that the Sun formed in such a cluster before scattering occurred. Title: Evolution of the Dust Size Distribution of Comet 67P/Churyumov-Gerasimenko from 2.2 au to Perihelion Authors: Fulle, M.; Marzari, F.; Della Corte, V.; Fornasier, S.; Sierks, H.; Rotundi, A.; Barbieri, C.; Lamy, P. L.; Rodrigo, R.; Koschny, D.; Rickman, H.; Keller, H. U.; López-Moreno, J. J.; Accolla, M.; Agarwal, J.; A'Hearn, M. F.; Altobelli, N.; Barucci, M. A.; Bertaux, J. -L.; Bertini, I.; Bodewits, D.; Bussoletti, E.; Colangeli, L.; Cosi, M.; Cremonese, G.; Crifo, J. -F.; Da Deppo, V.; Davidsson, B.; Debei, S.; De Cecco, M.; Esposito, F.; Ferrari, M.; Giovane, F.; Gustafson, B.; Green, S. F.; Groussin, O.; Grün, E.; Gutierrez, P.; Güttler, C.; Herranz, M. L.; Hviid, S. F.; Ip, W.; Ivanovski, S. L.; Jerónimo, J. M.; Jorda, L.; Knollenberg, J.; Kramm, R.; Kührt, E.; Küppers, M.; Lara, L.; Lazzarin, M.; Leese, M. R.; López-Jiménez, A. C.; Lucarelli, F.; Mazzotta Epifani, E.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Mottola, S.; Naletto, G.; Oklay, N.; Ortiz, J. L.; Palomba, E.; Palumbo, P.; Perrin, J. -M.; Rietmeijer, F. J. M.; Rodríguez, J.; Sordini, R.; Thomas, N.; Tubiana, C.; Vincent, J. -B.; Weissman, P.; Wenzel, K. -P.; Zakharov, V.; Zarnecki, J. C. Bibcode: 2016ApJ...821...19F Altcode: The Rosetta probe, orbiting Jupiter-family comet 67P/Churyumov-Gerasimenko, has been detecting individual dust particles of mass larger than 10-10 kg by means of the GIADA dust collector and the OSIRIS Wide Angle Camera and Narrow Angle Camera since 2014 August and will continue until 2016 September. Detections of single dust particles allow us to estimate the anisotropic dust flux from 67P, infer the dust loss rate and size distribution at the surface of the sunlit nucleus, and see whether the dust size distribution of 67P evolves in time. The velocity of the Rosetta orbiter, relative to 67P, is much lower than the dust velocity measured by GIADA, thus dust counts when GIADA is nadir-pointing will directly provide the dust flux. In OSIRIS observations, the dust flux is derived from the measurement of the dust space density close to the spacecraft. Under the assumption of radial expansion of the dust, observations in the nadir direction provide the distance of the particles by measuring their trail length, with a parallax baseline determined by the motion of the spacecraft. The dust size distribution at sizes >1 mm observed by OSIRIS is consistent with a differential power index of -4, which was derived from models of 67P’s trail. At sizes <1 mm, the size distribution observed by GIADA shows a strong time evolution, with a differential power index drifting from -2 beyond 2 au to -3.7 at perihelion, in agreement with the evolution derived from coma and tail models based on ground-based data. The refractory-to-water mass ratio of the nucleus is close to six during the entire inbound orbit and at perihelion. Title: Division G Commission 36: Theory of Stellar Atmospheres Authors: Puls, Joachim; Hubeny, Ivan; Asplund, Martin; Allard, France; Allende Prieto, Carlos; Ayres, Thomas R.; Carlsson, Mats; Gustafsson, Bengt; Kudritzki, Rolf-Peter; Ryabchikova, Tatiana A. Bibcode: 2016IAUTA..29..453P Altcode: Different from previous triennial reports, this report covers the activities of IAU Commission 36 `Theory of Stellar Atmospheres' over the past six years†, and will be the last report from the `old' Commission 36. After the General Assembly in Honolulu (August 2015), a new Commission `Stellar and Planetary Atmospheres' (C.G5, under Division G, `Stars and Stellar Physics') has come into life, and will continue our work devoted to the outer envelopes of stars, as well as extend it to the atmospheres of planets (see Sect. 4). Title: The detailed chemical composition of the terrestrial planet host Kepler-10 Authors: Liu, F.; Yong, D.; Asplund, M.; Ramírez, I.; Meléndez, J.; Gustafsson, B.; Howes, L. M.; Roederer, I. U.; Lambert, D. L.; Bensby, T. Bibcode: 2016MNRAS.456.2636L Altcode: 2015arXiv151109287L Chemical abundance studies of the Sun and solar twins have demonstrated that the solar composition of refractory elements is depleted when compared to volatile elements, which could be due to the formation of terrestrial planets. In order to further examine this scenario, we conducted a line-by-line differential chemical abundance analysis of the terrestrial planet host Kepler-10 and 14 of its stellar twins. Stellar parameters and elemental abundances of Kepler-10 and its stellar twins were obtained with very high precision using a strictly differential analysis of high quality Canada-France-Hawaii Telescope, Hobby-Eberly Telescope and Magellan spectra. When compared to the majority of thick disc twins, Kepler-10 shows a depletion in the refractory elements relative to the volatile elements, which could be due to the formation of terrestrial planets in the Kepler-10 system. The average abundance pattern corresponds to ∼13 Earth masses, while the two known planets in Kepler-10 system have a combined ∼20 Earth masses. For two of the eight thick disc twins, however, no depletion patterns are found. Although our results demonstrate that several factors [e.g. planet signature, stellar age, stellar birth location and Galactic chemical evolution (GCE)] could lead to or affect abundance trends with condensation temperature, we find that the trends give further support for the planetary signature hypothesis. Title: Shelf-to-basin iron shuttling enhances vivianite formation in deep Baltic Sea sediments Authors: Reed, Daniel C.; Gustafsson, Bo G.; Slomp, Caroline P. Bibcode: 2016E&PSL.434..241R Altcode: Coastal hypoxia is a growing and persistent problem largely attributable to enhanced terrestrial nutrient (i.e., nitrogen and phosphorus) loading. Recent studies suggest phosphorus removal through burial of iron (II) phosphates, putatively vivianite, plays an important role in nutrient cycling in the Baltic Sea - the world's largest anthropogenic dead zone - yet the dynamics of iron (II) phosphate formation are poorly constrained. To address this, a reactive-transport model was used to reconstruct the diagenetic and depositional history of sediments in the Fårö basin, a deep anoxic and sulphidic region of the Baltic Sea where iron (II) phosphates have been observed. Simulations demonstrate that transport of iron from shelf sediments to deep basins enhances vivianite formation while sulphide concentrations are low, but that pyrite forms preferentially over vivianite when sulphate reduction intensifies due to elevated organic loading. Episodic reoxygenation events, associated with major inflows of oxic waters, encourage the retention of iron oxyhydroxides and iron-bound phosphorus in sediments, increasing vivianite precipitation as a result. Results suggest that artificial reoxygenation of the Baltic Sea bottom waters could sequester up to 3% of the annual external phosphorus loads as iron (II) phosphates, but this is negligible when compared to potential internal phosphorus loads due to dissolution of iron oxyhydroxides when low oxygen conditions prevail. Thus, enhancing vivianite formation through artificial reoxygenation of deep waters is not a viable engineering solution to eutrophication in the Baltic Sea. Finally, simulations suggest that regions with limited sulphate reduction and hypoxic intervals, such as eutrophic estuaries, could act as important phosphorus sinks by sequestering vivianite. This could potentially alleviate eutrophication in shelf and slope environments. Title: Coma dust environment observed by GIADA during the Perihelion of 67P/Churyumov-Gerasimenko. Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Ferrari, M.; Ivanovski, S. L.; Sordini, R.; Mazzotta Epifani, E.; Palumbo, P.; Colangeli, L.; Lopez-Moreno, J. J.; Rodriguez, J.; Zakharov, V.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S.; Gruen, E.; Lamy, P. L.; McDonnell, T.; Mennella, V.; Molina, A.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rodrigo, R.; Weissman, P. R.; Zarnecki, J.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M.; Jeronimo, J. M.; Leese, M.; Lopez-Jimenez, A.; Morales, R. Bibcode: 2015AGUFM.P33E..05R Altcode: GIADA (Grain Impact Analyzer and Dust Accumulator) is an in-situ instrument mounted onboard Rosetta monitoring the dust environment of comet 67P/Churyumov-Gerasimenko. GIADA is composed of 3 sub-systems: 1) the Grain Detection System, based on particle detection through light scattering; 2) the Impact Sensor, giving momentum measurement; 3) the Micro-Balances System, constituted of 5 quartz crystal microbalances, giving cumulative deposited dust. The combination of the measurements performed by these 3 subsystems provides: the number, the mass, the momentum and the speed distribution of dust particles emitted from the comet nucleus. We will present the coma dust environment as observed by GIADA during the perihelion phase of the Rosetta space mission. Despite the large distance from the nucleus, more than 200 km, GIADA was able to detect temporal and spatial variation of dust density distribution. Specific high dust spatial density sectors of the coma have been identified and their evolution during the perihelion phase was studied. Acknowledgements. GIADA was built by a consortium led by the Univ. Napoli "Parthenope" & INAF- Oss. Astr. Capodimonte, IT, in collaboration with the Inst. de Astrofisica de Andalucia, ES, Selex-ES s.p.a. and SENER. GIADA is presently managed & operated by Ist. di Astrofisica e Planetologia Spaziali-INAF, IT. GIADA was funded and managed by the Agenzia Spaziale Italiana, IT, with a support of the Spanish Ministry of Education and Science MEC, ES. GIADA was developped from a PI proposal supported by the University of Kent; sci. & tech. contribution given by CISAS, IT, Lab. d'Astr. Spat., FR, and Institutions from UK, IT, FR, DE and USA. We thank the RSGS/ESAC, RMOC/ESOC & Rosetta Project/ESTEC for their outstanding work. Science support provided by NASA through the US Rosetta Project managed by JPL/California Institute of Technology. GIADA calibrated data will be available through the ESA's PSA web site. Title: GIADA: shining a light on the monitoring of the comet dust production from the nucleus of 67P/Churyumov-Gerasimenko Authors: Della Corte, V.; Rotundi, A.; Fulle, M.; Gruen, E.; Weissman, P.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Accolla, M.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.; Crifo, J. F.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. M.; Rietmeijer, F. J. M.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N. Bibcode: 2015A&A...583A..13D Altcode: Context. During the period between 15 September 2014 and 4 February 2015, the Rosetta spacecraft accomplished the circular orbit phase around the nucleus of comet 67P/Churyumov-Gerasimenko (67P). The Grain Impact Analyzer and Dust Accumulator (GIADA) onboard Rosetta monitored the 67P coma dust environment for the entire period.
Aims: We aim to describe the dust spatial distribution in the coma of comet 67P by means of in situ measurements. We determine dynamical and physical properties of cometary dust particles to support the study of the production process and dust environment modification.
Methods: We analyzed GIADA data with respect to the observation geometry and heliocentric distance to describe the coma dust spatial distribution of 67P, to monitor its activity, and to retrieve information on active areas present on its nucleus. We combined GIADA detection information with calibration activity to distinguish different types of particles that populate the coma of 67P: compact particles and fluffy porous aggregates. By means of particle dynamical parameters measured by GIADA, we studied the dust acceleration region.
Results: GIADA was able to distinguish different types of particles populating the coma of 67P: compact particles and fluffy porous aggregates. Most of the compact particle detections occurred at latitudes and longitudes where the spacecraft was in view of the comet's neck region of the nucleus, the so-called Hapi region. This resulted in an oscillation of the compact particle abundance with respect to the spacecraft position and a global increase as the comet moved from 3.36 to 2.43 AU heliocentric distance. The speed of these particles, having masses from 10-10 to 10-7 kg, ranged from 0.3 to 12.2 m s-1. The variation of particle mass and speed distribution with respect to the distance from the nucleus gave indications of the dust acceleration region. The influence of solar radiation pressure on micron and submicron particles was studied. The integrated dust mass flux collected from the Sun direction, that is, particles reflected by solar radiation pressure, was three times higher than the flux coming directly from the comet nucleus. The awakening 67P comet shows a strong dust flux anisotropy, confirming what was suggested by on-ground dust coma observations performed in 2008. Title: Gaia FGK benchmark stars: Effective temperatures and surface gravities Authors: Heiter, U.; Jofré, P.; Gustafsson, B.; Korn, A. J.; Soubiran, C.; Thévenin, F. Bibcode: 2015A&A...582A..49H Altcode: 2015arXiv150606095H Context. In the era of large Galactic stellar surveys, carefully calibrating and validating the data sets has become an important and integral part of the data analysis. Moreover, new generations of stellar atmosphere models and spectral line formation computations need to be subjected to benchmark tests to assess any progress in predicting stellar properties.
Aims: We focus on cool stars and aim at establishing a sample of 34 Gaia FGK benchmark stars with a range of different metallicities. The goal was to determine the effective temperature and the surface gravity independently of spectroscopy and atmospheric models as far as possible. Most of the selected stars have been subjected to frequent spectroscopic investigations in the past, and almost all of them have previously been used as reference, calibration, or test objects.
Methods: Fundamental determinations of Teff and log g were obtained in a systematic way from a compilation of angular diameter measurements and bolometric fluxes and from a homogeneous mass determination based on stellar evolution models. The derived parameters were compared to recent spectroscopic and photometric determinations and to gravity estimates based on seismic data.
Results: Most of the adopted diameter measurements have formal uncertainties around 1%, which translate into uncertainties in effective temperature of 0.5%. The measurements of bolometric flux seem to be accurate to 5% or better, which contributes about 1% or less to the uncertainties in effective temperature. The comparisons of parameter determinations with the literature in general show good agreements with a few exceptions, most notably for the coolest stars and for metal-poor stars.
Conclusions: The sample consists of 29 FGK-type stars and 5 M giants. Among the FGK stars, 21 have reliable parameters suitable for testing, validation, or calibration purposes. For four stars, future adjustments of the fundamental Teff are required, and for five stars the log g determination needs to be improved. Future extensions of the sample of Gaia FGK benchmark stars are required to fill gaps in parameter space, and we include a list of suggested candidates. Title: New H-band Stellar Spectral Libraries for the SDSS-III/APOGEE Survey Authors: Zamora, O.; García-Hernández, D. A.; Allende Prieto, C.; Carrera, R.; Koesterke, L.; Edvardsson, B.; Castelli, F.; Plez, B.; Bizyaev, D.; Cunha, K.; García Pérez, A. E.; Gustafsson, B.; Holtzman, J. A.; Lawler, J. E.; Majewski, S. R.; Manchado, A.; Mészáros, Sz.; Shane, N.; Shetrone, M.; Smith, V. V.; Zasowski, G. Bibcode: 2015AJ....149..181Z Altcode: 2015arXiv150205237Z The Sloan Digital Sky Survey-III (SDSS-III) Apache Point Observatory Galactic Evolution Experiment (APOGEE) has obtained high-resolution (R ∼ 22,500), high signal-to-noise ratio (\gt 100) spectra in the H-band (∼1.5-1.7 μm) for about 146,000 stars in the Milky Way galaxy. We have computed spectral libraries with effective temperature ({{T}eff}) ranging from 3500 to 8000 K for the automated chemical analysis of the survey data. The libraries, used to derive stellar parameters and abundances from the APOGEE spectra in the SDSS-III data release 12 (DR12), are based on ATLAS9 model atmospheres and the ASSɛT spectral synthesis code. We present a second set of libraries based on MARCS model atmospheres and the spectral synthesis code Turbospectrum. The ATLAS9/ASSɛT ({{T}eff} = 3500-8000 K) and MARCS/Turbospectrum ({{T}eff} = 3500-5500 K) grids cover a wide range of metallicity (-2.5 ≤slant [M/H] ≤slant +0.5 dex), surface gravity (0 ≤ log g ≤slant 5 dex), microturbulence (0.5 ≤slant ξ ≤slant 8 km s-1), carbon (-1 ≤slant [C/M] ≤slant +1 dex), nitrogen (-1 ≤slant [N/M] ≤slant +1 dex), and α-element (-1 ≤slant [α/M] ≤slant +1 dex) variations, having thus seven dimensions. We compare the ATLAS9/ASSɛT and MARCS/Turbospectrum libraries and apply both of them to the analysis of the observed H-band spectra of the Sun and the K2 giant Arcturus, as well as to a selected sample of well-known giant stars observed at very high resolution. The new APOGEE libraries are publicly available and can be employed for chemical studies in the H-band using other high-resolution spectrographs. Title: Dust Measurements in the Coma of Comet 67P/Churyumov-Gerasimenko Inbound to the Sun Between 3.7 and 3.4 AU Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Bussoletti, E.; Crifo, J.; Esposito, F.; Green, S. F.; Gruen, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J.; Rodrigo, R.; Weissman, P.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A. C.; Altobelli, N.; Sierks, H.; Agarwal, J.; Bertini, I.; Fornasier, S.; Gutierrez, P. J.; Lara, L.; Guettler, C.; Marzari, F.; Oaklay, N.; Snodgrass, C.; Tubiana, C.; Vincenzo, J. B. Bibcode: 2015LPI....46.2420F Altcode: 2015LPICo1832.2420F GIADA and OSIRIS dust data, combined with data from MIRO and ROSINA instruments onboard Rosetta, from 3.7 to 3.4 AU inbound provide a dust/gas ratio of 4 ± 2. Title: Density and Charge of Pristine Fluffy Particles from Comet 67P/Churyumov-Gerasimenko Authors: Fulle, M.; Della Corte, V.; Rotundi, A.; Weissman, P.; Juhasz, A.; Szego, K.; Sordini, R.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Accolla, M.; Merouane, S.; Zakharov, V.; Mazzotta Epifani, E.; López-Moreno, J. J.; Rodríguez, J.; Colangeli, L.; Palumbo, P.; Grün, E.; Hilchenbach, M.; Bussoletti, E.; Esposito, F.; Green, S. F.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Rodrigo, R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jerónimo, J. M.; Leese, M. R.; López-Jiménez, A. C.; Altobelli, N. Bibcode: 2015ApJ...802L..12F Altcode: The Grain Impact Analyzer and Dust Accumulator (GIADA) instrument on board ESA’s Rosetta mission is constraining the origin of the dust particles detected within the coma of comet 67 P/Churyumov-Gerasimenko (67P). The collected particles belong to two families: (i) compact particles (ranging in size from 0.03 to 1 mm), witnessing the presence of materials that underwent processing within the solar nebula and (ii) fluffy aggregates (ranging in size from 0.2 to 2.5 mm) of sub-micron grains that may be a record of a primitive component, probably linked to interstellar dust. The dynamics of the fluffy aggregates constrain their equivalent bulk density to \lt 1 kg m-3. These aggregates are charged, fragmented, and decelerated by the spacecraft negative potential and enter GIADA in showers of fragments at speeds \lt 1 m s-1. The density of such optically thick aggregates is consistent with the low bulk density of the nucleus. The mass contribution of the fluffy aggregates to the refractory component of the nucleus is negligible and their coma brightness contribution is less than 15%. Title: Dust measurements in the coma of comet 67P/Churyumov-Gerasimenko inbound to the Sun Authors: Rotundi, Alessandra; Sierks, Holger; Della Corte, Vincenzo; Fulle, Marco; Gutierrez, Pedro J.; Lara, Luisa; Barbieri, Cesare; Lamy, Philippe L.; Rodrigo, Rafael; Koschny, Detlef; Rickman, Hans; Keller, Horst Uwe; López-Moreno, José J.; Accolla, Mario; Agarwal, Jessica; A'Hearn, Michael F.; Altobelli, Nicolas; Angrilli, Francesco; Barucci, M. Antonietta; Bertaux, Jean-Loup; Bertini, Ivano; Bodewits, Dennis; Bussoletti, Ezio; Colangeli, Luigi; Cosi, Massimo; Cremonese, Gabriele; Crifo, Jean-Francois; Da Deppo, Vania; Davidsson, Björn; Debei, Stefano; De Cecco, Mariolino; Esposito, Francesca; Ferrari, Marco; Fornasier, Sonia; Giovane, Frank; Gustafson, Bo; Green, Simon F.; Groussin, Olivier; Grün, Eberhard; Güttler, Carsten; Herranz, Miguel L.; Hviid, Stubbe F.; Ip, Wing; Ivanovski, Stavro; Jerónimo, José M.; Jorda, Laurent; Knollenberg, Joerg; Kramm, Rainer; Kührt, Ekkehard; Küppers, Michael; Lazzarin, Monica; Leese, Mark R.; López-Jiménez, Antonio C.; Lucarelli, Francesca; Lowry, Stephen C.; Marzari, Francesco; Epifani, Elena Mazzotta; McDonnell, J. Anthony M.; Mennella, Vito; Michalik, Harald; Molina, Antonio; Morales, Rafael; Moreno, Fernando; Mottola, Stefano; Naletto, Giampiero; Oklay, Nilda; Ortiz, José L.; Palomba, Ernesto; Palumbo, Pasquale; Perrin, Jean-Marie; Rodríguez, Julio; Sabau, Lola; Snodgrass, Colin; Sordini, Roberto; Thomas, Nicolas; Tubiana, Cecilia; Vincent, Jean-Baptiste; Weissman, Paul; Wenzel, Klaus-Peter; Zakharov, Vladimir; Zarnecki, John C. Bibcode: 2015Sci...347a3905R Altcode: 2015Sci...347.3905R Critical measurements for understanding accretion and the dust/gas ratio in the solar nebula, where planets were forming 4.5 billion years ago, are being obtained by the GIADA (Grain Impact Analyser and Dust Accumulator) experiment on the European Space Agency’s Rosetta spacecraft orbiting comet 67P/Churyumov-Gerasimenko. Between 3.6 and 3.4 astronomical units inbound, GIADA and OSIRIS (Optical, Spectroscopic, and Infrared Remote Imaging System) detected 35 outflowing grains of mass 10-10 to 10-7 kilograms, and 48 grains of mass 10-5 to 10-2 kilograms, respectively. Combined with gas data from the MIRO (Microwave Instrument for the Rosetta Orbiter) and ROSINA (Rosetta Orbiter Spectrometer for Ion and Neutral Analysis) instruments, we find a dust/gas mass ratio of 4 ± 2 averaged over the sunlit nucleus surface. A cloud of larger grains also encircles the nucleus in bound orbits from the previous perihelion. The largest orbiting clumps are meter-sized, confirming the dust/gas ratio of 3 inferred at perihelion from models of dust comae and trails. Title: HIRES: the high resolution spectrograph for the E-ELT Authors: Zerbi, F. M.; Bouchy, F.; Fynbo, J.; Maiolino, R.; Piskunov, N.; Rebolo Lopez, R.; Santos, N.; Strassmeier, K.; Udry, S.; Vanzi, L.; Riva, M.; Basden, A.; Boisse, I.; Bonfils, X.; Buscher, D.; Cabral, A.; Dimarcantonio, P.; Di Varano, I.; Henry, D.; Monteiro, M.; Morris, T.; Murray, G.; Oliva, Ernesto; Parry, I.; Pepe, F.; Quirrenbach, A.; Rasilla, J. L.; Rees, P.; Stempels, E.; Valenziano, L.; Wells, M.; Wildi, F.; Origlia, L.; Allende Prieto, C.; Chiavassa, A.; Cristiani, S.; Figueira, P.; Gustafsson, B.; Hatzes, A.; Haehnelt, M.; Heng, K.; Israelian, G.; Kochukhov, O.; Lovis, C.; Marconi, A.; Martins, C. J. A. P.; Noterdaeme, P.; Petitjean, P.; Puzia, T.; Queloz, D.; Reiners, A.; Zoccali, M. Bibcode: 2014SPIE.9147E..23Z Altcode: The current instrumentation plan for the E-ELT foresees a High Resolution Spectrograph conventionally indicated as HIRES. Shaped on the study of extra-solar planet atmospheres, Pop-III stars and fundamental physical constants, HIRES is intended to embed observing modes at high-resolution (up to R=150000) and large spectral range (from the blue limit to the K band) useful for a large suite of science cases that can exclusively be tackled by the E-ELT. We present in this paper the solution for HIRES envisaged by the "HIRES initiative", the international collaboration established in 2013 to pursue a HIRES on E-ELT. Title: Benchmark stars for cross-calibration of Galactic stellar surveys Authors: Heiter, U.; Jofré, P.; Gustafsson, B.; Thévenin, F.; Korn, A.; Soubiran, C.; Blanco-Cuaresma, S. Bibcode: 2014EAS....67..375H Altcode: Various Galactic stellar spectroscopic surveys are currently underway, and each is expected to achieve high internal accuracy in terms of stellar parameters and abundances. A number of questions related to the formation and evolution of the Galaxy may be addressed based on samples of stars observed within each survey. In addition, complementary samples of stars may be constructed by combining data from different surveys. The Gaia FGK Benchmark Stars provide the necessary link to bring the quantities measured from different spectra with different methods onto the same scale. We selected 28 FGK stars and 5 M giants with available angular diameter θ, bolometric flux Fbol, and distance. We used the fundamental relation Teff ∝ F/θ0.5 to determine a reference effective temperature. We used the fundamental relation g ∝ M/R2, where M is the mass and R the radius, to determine a reference surface gravity. A homogeneous analysis of a high resolution and high signal-to-noise spectral library provides a reference metallicity (Blanco-Cuaresma et al. 2014A&A...566A..98B, Jofré et al. 2014A&A...564A.133J). These stars serve as a reference for testing and homogenizing large stellar surveys such as the Gaia mission and the Gaia-ESO public spectroscopic survey and for improving models of FGK-star atmospheres. A detailed discussion of the fundamental Teff and logg values will be presented in Heiter et al. (to be submitted). Title: Early Grain Detections in the Coma of Comet 67P/Churyumov-Gerasimenko Authors: Rotundi, A.; Della Corte, V.; Fulle, M.; Accolla, M.; Ferrari, M.; Ivanovski, S.; Lucarelli, F.; Sordini, R.; Zakharov, V.; Mazzotta Epifani, E.; Lopez-Moreno, J. J.; Rodriguez, J.; Colangeli, L.; Palumbo, P.; Crifo, J. C.; Bussoletti, E.; Esposito, F.; Green, S.; Grün, E.; Lamy, P. L.; McDonnell, J. A. M.; Mennella, V.; Molina, A.; Morales, R.; Moreno, F.; Ortiz, J. L.; Palomba, E.; Perrin, J. -M.; Rietmeijer, F. J. M.; Rodrigo, R.; Weissman, P. R.; Zarnecki, J. C.; Cosi, M.; Giovane, F.; Gustafson, B.; Herranz, M. L.; Jeronimo, J. M.; Leese, M. R.; Lopez-Jimenez, A.; Altobelli, N. Bibcode: 2014EPSC....9..868R Altcode: The GIADA (Grain Impact Analyser and Dust Accumulator) instrument aboard the Rosetta spacecraft at comet 67P/Churyumov-Gerasimenko (67P/C-G) measures dust grain number, mass, momentum and velocity [1,2]. GIADA is composed of three sub-systems: the Grain Detection System (GDS), detecting dust grains based on light scattering; an Impact Sensor (IS), providing momentum measurements from the impact on a plate connected to five piezoelectric sensors; and the MicroBalances System (MBS), made up of five Quartz Crystal Microbalances (QCMs), to yield cumulative deposited dust mass through the shift in resonance frequency. Title: Abundances and possible diffusion of elements in M 67 stars Authors: Önehag, Anna; Gustafsson, Bengt; Korn, Andreas Bibcode: 2014A&A...562A.102O Altcode: 2013arXiv1310.6297O Context. The rich open cluster M 67 is known to have a chemical composition close to solar and an age of about 3.5-4.8 Gyr. It offers an important opportunity to check and develop our understanding of the physics and the evolution of solar-type stars.
Aims: We present a spectroscopic study at high resolution, R ≈ 50 000, of 14 stars located on the main sequence, at the turn-off point, and on the early subgiant branch in the cluster in order to investigate its detailed chemical composition, for comparison with the Sun and solar twins in the solar neighbourhood, and to explore selective atomic diffusion of chemical elements as predicted by stellar-structure theory.
Methods: We have obtained VLT/FLAMES-UVES spectra and analysed these strictly differentially in order to explore chemical-abundance similarities and differences between the M 67 stars and the Sun and among the M 67 stars themselves.
Results: Individual abundances of 19 different chemical elements are obtained for the stars. They are found to agree very well with solar abundances, with abundance ratios closer to solar than those of most solar twins in the solar neighbourhood. An exception is Li, which shows considerable scatter among the cluster stars. There is a tendency for the cluster-star abundances to be more depleted than the abundances in the field stars in correlation with the condensation temperature of the elements, a tendency also found earlier for the Sun. Moreover, the heavy-element abundances are found to be reduced in the hotter stars and dwarfs by typically ≤0.05 dex, as compared to the abundances of the subgiants.
Conclusions: The results support the hypothesis that the gas of the proto-cluster was depleted by formation and cleansing of dust before the stars formed. They also add support to the proposal that the Sun was formed in a dense stellar environment. Moreover, the observed minor reductions of heavy elements, relative to our standard star M 67-1194 and the subgiants, in the atmospheres of dwarfs and turn-off point stars seem to suggest that diffusion processes are at work in these stars, although the evidence is not compelling. Based on theoretical models, the diffusion-corrected initial metallicity of M 67 is estimated to be [Fe/H] = +0.06.

Appendix A is available in electronic form at http://www.aanda.org Title: Model Stellar Spectral Libraries for Analysis of the SDSS-III Apache Point Observatory Galactic Evolution Experiment (APOGEE) Authors: Allende-Prieto, Carlos; Koesterke, L.; Shetrone, M. D.; Zamora, O.; Ruffoni, M. P.; Smith, V. V.; Cunha, K. M.; Lawler, J. E.; Pickering, J. C.; Nave, G.; Garcia Perez, A.; Bizyaev, D.; Edvardsson, B.; Gustafsson, B.; Plez, B.; Castelli, F.; Majewski, S. R.; Schiavon, R. P.; Meszaros, Sz.; de Vicente, A. Bibcode: 2014AAS...22344005A Altcode: The Apache Point Observatory Galactic Evolution Experiment (APOGEE) is obtaining high resolution ( 22,500), high signal-to-noise (> 100) spectra in the 1510-1690 nm spectral region for 100,000 cool, predominantly post-main sequence stars. To ascertain the stellar atmospheric parameters and measure chemical abundances for the numerous chemical elements with line transitions in this wavelength region, the APOGEE Atmospheric Parameters and Chemical Abundances Pipeline (ASPCAP) relies on an optimization algorithm that identifies the best-fitting model for each of the observed APOGEE spectra. The fitting algorithm speeds up the model evaluation by interpolation in pre-computed grids of synthetic spectra that have been compressed using Principal Component Analysis. Here we describe the main model grids used in ASPCAP for the tenth data release of the Sloan Digital Sky Survey (SDSS DR10), how they were calculated. We also provide a description of ongoing and planned upgrades. Title: A Community Science Case for E-ELT HIRES Authors: Maiolino, R.; Haehnelt, M.; Murphy, M. T.; Queloz, D.; Origlia, L.; Alcala, J.; Alibert, Y.; Amado, P. J.; Allende Prieto, C.; Ammler-von Eiff, M.; Asplund, M.; Barstow, M.; Becker, G.; Bonfils, X.; Bouchy, F.; Bragaglia, A.; Burleigh, M. R.; Chiavassa, A.; Cimatti, D. A.; Cirasuolo, M.; Cristiani, S.; D'Odorico, V.; Dravins, D.; Emsellem, E.; Farihi, J.; Figueira, P.; Fynbo, J.; Gansicke, B. T.; Gillon, M.; Gustafsson, B.; Hill, V.; Israelyan, G.; Korn, A.; Larsen, S.; De Laverny, P.; Liske, J.; Lovis, C.; Marconi, A.; Martins, C.; Molaro, P.; Nisini, B.; Oliva, E.; Petitjean, P.; Pettini, M.; Recio Blanco, A.; Rebolo, R.; Reiners, A.; Rodriguez-Lopez, C.; Ryde, N.; Santos, N. C.; Savaglio, S.; Snellen, I.; Strassmeier, K.; Tanvir, N.; Testi, L.; Tolstoy, E.; Triaud, A.; Vanzi, L.; Viel, M.; Volonteri, M. Bibcode: 2013arXiv1310.3163M Altcode: Building on the experience of the high-resolution community with the suite of VLT high-resolution spectrographs, which has been tremendously successful, we outline here the (science) case for a high-fidelity, high-resolution spectrograph with wide wavelength coverage at the E-ELT. Flagship science drivers include: the study of exo-planetary atmospheres with the prospect of the detection of signatures of life on rocky planets; the chemical composition of planetary debris on the surface of white dwarfs; the spectroscopic study of protoplanetary and proto-stellar disks; the extension of Galactic archaeology to the Local Group and beyond; spectroscopic studies of the evolution of galaxies with samples that, unlike now, are no longer restricted to strongly star forming and/or very massive galaxies; the unraveling of the complex roles of stellar and AGN feedback; the study of the chemical signatures imprinted by population III stars on the IGM during the epoch of reionization; the exciting possibility of paradigm-changing contributions to fundamental physics. The requirements of these science cases can be met by a stable instrument with a spectral resolution of R~100,000 and broad, simultaneous spectral coverage extending from 370nm to 2500nm. Most science cases do not require spatially resolved information, and can be pursued in seeing-limited mode, although some of them would benefit by the E-ELT diffraction limited resolution. Some multiplexing would also be beneficial for some of the science cases. (Abridged) Title: New ATLAS9 and MARCS Model Atmosphere Grids for the Apache Point Observatory Galactic Evolution Experiment (APOGEE) Authors: Mészáros, Sz.; Allende Prieto, C.; Edvardsson, B.; Castelli, F.; García Pérez, A. E.; Gustafsson, B.; Majewski, S. R.; Plez, B.; Schiavon, R.; Shetrone, M.; de Vicente, A. Bibcode: 2012AJ....144..120M Altcode: 2012arXiv1208.1916M We present a new grid of model photospheres for the SDSS-III/APOGEE survey of stellar populations of the Galaxy, calculated using the ATLAS9 and MARCS codes. New opacity distribution functions were generated to calculate ATLAS9 model photospheres. MARCS models were calculated based on opacity sampling techniques. The metallicity ([M/H]) spans from -5 to 1.5 for ATLAS and -2.5 to 0.5 for MARCS models. There are three main differences with respect to previous ATLAS9 model grids: a new corrected H2O line list, a wide range of carbon ([C/M]) and α element [α/M] variations, and solar reference abundances from Asplund et al. The added range of varying carbon and α-element abundances also extends the previously calculated MARCS model grids. Altogether, 1980 chemical compositions were used for the ATLAS9 grid and 175 for the MARCS grid. Over 808,000 ATLAS9 models were computed spanning temperatures from 3500 K to 30,000 K and log g from 0 to 5, where larger temperatures only have high gravities. The MARCS models span from 3500 K to 5500 K, and log g from 0 to 5. All model atmospheres are publicly available online. Title: Obituaries: Roger A Bell: 1935-2012 Authors: Gustafsson, Bengt Bibcode: 2012A&G....53e..38G Altcode: Fellow of the RAS, stellar spectroscopist who pioneered the calculation of synthetic spectra and their diverse applications. Title: M-dwarf metallicities. A high-resolution spectroscopic study in the near infrared Authors: Önehag, A.; Heiter, U.; Gustafsson, B.; Piskunov, N.; Plez, B.; Reiners, A. Bibcode: 2012A&A...542A..33O Altcode: 2011arXiv1112.0141O Context. The relatively wide spread in the derived metallicities ([Fe/H]) of M dwarfs shows that various approaches have not yet converged to consistency. The presence of strong molecular features and incomplete line lists for the corresponding molecules have made determining the metallicity of M dwarfs difficult. Furthermore, the faint M dwarfs require long exposure times for the signal-to-noise ratio needed for a detailed spectroscopic abundance analysis.
Aims: We present a high-resolution (R ~ 50 000) spectroscopic study of a sample of eight single M dwarfs and three wide-binary systems observed in the infrared J band.
Methods: The absence of large molecular contributions allows for a precise continuum placement. We derived metallicities based on the best fit of synthetic spectra to the observed spectra. To verify the accuracy of the applied atmospheric models and test our synthetic spectrum approach, three binary systems with a K-dwarf primary and an M-dwarf companion were observed and analysed along with the single M dwarfs.
Results: We obtain good agreement between the metallicities derived for the primaries and secondaries of our test binaries, thereby confirming the reliability of our method of analysing M dwarfs. Our metallicities agree well with some earlier determinations, and deviate from others.
Conclusions: We conclude that spectroscopic abundance analysis in the J band is a reliable method for establishing the metallicity scale for M dwarfs. We recommend its application to a larger sample covering lower, as well as higher, metallicities. Further prospects for the method include abundance determinations for individual elements.

Based on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID 082.D-0838(A) and 084.D-1042(A).Table 2 is available in electronic form at http://www.aanda.orgElectronic version of the spectra is only available at CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/542/A33 Title: VizieR Online Data Catalog: 3 M dwarfs near-infrared spectra (Onehag+, 2012) Authors: Onehag, A.; Heiter, U.; Gustafsson, B.; Piskunov, N.; Plez, B.; Reiners, A. Bibcode: 2012yCat..35420033O Altcode: 2012yCat..35429033O The observations were carried out in service mode with the infrared spectrometer CRIRES at ESO-VLT.

In total 14 targets were observed during periods 82 (1st of October 2008 to 31st of March 2009) and 84 (1st of October 2009 to 31st of March 2010).

(4 data files). Title: The Gaia-ESO Public Spectroscopic Survey Authors: Gilmore, G.; Randich, S.; Asplund, M.; Binney, J.; Bonifacio, P.; Drew, J.; Feltzing, S.; Ferguson, A.; Jeffries, R.; Micela, G.; Negueruela, I.; Prusti, T.; Rix, H. -W.; Vallenari, A.; Alfaro, E.; Allende-Prieto, C.; Babusiaux, C.; Bensby, T.; Blomme, R.; Bragaglia, A.; Flaccomio, E.; François, P.; Irwin, M.; Koposov, S.; Korn, A.; Lanzafame, A.; Pancino, E.; Paunzen, E.; Recio-Blanco, A.; Sacco, G.; Smiljanic, R.; Van Eck, S.; Walton, N.; Aden, D.; Aerts, C.; Affer, L.; Alcala, J. -M.; Altavilla, G.; Alves, J.; Antoja, T.; Arenou, F.; Argiroffi, C.; Asensio Ramos, A.; Bailer-Jones, C.; Balaguer-Nunez, L.; Bayo, A.; Barbuy, B.; Barisevicius, G.; Barrado y Navascues, D.; Battistini, C.; Bellas Velidis, I.; Bellazzini, M.; Belokurov, V.; Bergemann, M.; Bertelli, G.; Biazzo, K.; Bienayme, O.; Bland-Hawthorn, J.; Boeche, C.; Bonito, S.; Boudreault, S.; Bouvier, J.; Brandao, I.; Brown, A.; de Bruijne, J.; Burleigh, M.; Caballero, J.; Caffau, E.; Calura, F.; Capuzzo-Dolcetta, R.; Caramazza, M.; Carraro, G.; Casagrande, L.; Casewell, S.; Chapman, S.; Chiappini, C.; Chorniy, Y.; Christlieb, N.; Cignoni, M.; Cocozza, G.; Colless, M.; Collet, R.; Collins, M.; Correnti, M.; Covino, E.; Crnojevic, D.; Cropper, M.; Cunha, M.; Damiani, F.; David, M.; Delgado, A.; Duffau, S.; Edvardsson, B.; Eldridge, J.; Enke, H.; Eriksson, K.; Evans, N. W.; Eyer, L.; Famaey, B.; Fellhauer, M.; Ferreras, I.; Figueras, F.; Fiorentino, G.; Flynn, C.; Folha, D.; Franciosini, E.; Frasca, A.; Freeman, K.; Fremat, Y.; Friel, E.; Gaensicke, B.; Gameiro, J.; Garzon, F.; Geier, S.; Geisler, D.; Gerhard, O.; Gibson, B.; Gomboc, A.; Gomez, A.; Gonzalez-Fernandez, C.; Gonzalez Hernandez, J.; Gosset, E.; Grebel, E.; Greimel, R.; Groenewegen, M.; Grundahl, F.; Guarcello, M.; Gustafsson, B.; Hadrava, P.; Hatzidimitriou, D.; Hambly, N.; Hammersley, P.; Hansen, C.; Haywood, M.; Heber, U.; Heiter, U.; Held, E.; Helmi, A.; Hensler, G.; Herrero, A.; Hill, V.; Hodgkin, S.; Huelamo, N.; Huxor, A.; Ibata, R.; Jackson, R.; de Jong, R.; Jonker, P.; Jordan, S.; Jordi, C.; Jorissen, A.; Katz, D.; Kawata, D.; Keller, S.; Kharchenko, N.; Klement, R.; Klutsch, A.; Knude, J.; Koch, A.; Kochukhov, O.; Kontizas, M.; Koubsky, P.; Lallement, R.; de Laverny, P.; van Leeuwen, F.; Lemasle, B.; Lewis, G.; Lind, K.; Lindstrom, H. P. E.; Lobel, A.; Lopez Santiago, J.; Lucas, P.; Ludwig, H.; Lueftinger, T.; Magrini, L.; Maiz Apellaniz, J.; Maldonado, J.; Marconi, G.; Marino, A.; Martayan, C.; Martinez-Valpuesta, I.; Matijevic, G.; McMahon, R.; Messina, S.; Meyer, M.; Miglio, A.; Mikolaitis, S.; Minchev, I.; Minniti, D.; Moitinho, A.; Momany, Y.; Monaco, L.; Montalto, M.; Monteiro, M. J.; Monier, R.; Montes, D.; Mora, A.; Moraux, E.; Morel, T.; Mowlavi, N.; Mucciarelli, A.; Munari, U.; Napiwotzki, R.; Nardetto, N.; Naylor, T.; Naze, Y.; Nelemans, G.; Okamoto, S.; Ortolani, S.; Pace, G.; Palla, F.; Palous, J.; Parker, R.; Penarrubia, J.; Pillitteri, I.; Piotto, G.; Posbic, H.; Prisinzano, L.; Puzeras, E.; Quirrenbach, A.; Ragaini, S.; Read, J.; Read, M.; Reyle, C.; De Ridder, J.; Robichon, N.; Robin, A.; Roeser, S.; Romano, D.; Royer, F.; Ruchti, G.; Ruzicka, A.; Ryan, S.; Ryde, N.; Santos, N.; Sanz Forcada, J.; Sarro Baro, L. M.; Sbordone, L.; Schilbach, E.; Schmeja, S.; Schnurr, O.; Schoenrich, R.; Scholz, R. -D.; Seabroke, G.; Sharma, S.; De Silva, G.; Smith, M.; Solano, E.; Sordo, R.; Soubiran, C.; Sousa, S.; Spagna, A.; Steffen, M.; Steinmetz, M.; Stelzer, B.; Stempels, E.; Tabernero, H.; Tautvaisiene, G.; Thevenin, F.; Torra, J.; Tosi, M.; Tolstoy, E.; Turon, C.; Walker, M.; Wambsganss, J.; Worley, C.; Venn, K.; Vink, J.; Wyse, R.; Zaggia, S.; Zeilinger, W.; Zoccali, M.; Zorec, J.; Zucker, D.; Zwitter, T.; Gaia-ESO Survey Team Bibcode: 2012Msngr.147...25G Altcode: The Gaia-ESO Public Spectroscopic Survey has begun and will obtain high quality spectroscopy of some 100000 Milky Way stars, in the field and in open clusters, down to magnitude 19, systematically covering all the major components of the Milky Way. This survey will provide the first homogeneous overview of the distributions of kinematics and chemical element abundances in the Galaxy. The motivation, organisation and implementation of the Gaia-ESO Survey are described, emphasising the complementarity with the ESA Gaia mission. Spectra from the very first observing run of the survey are presented. Title: Hypoxia in future climates: A model ensemble study for the Baltic Sea Authors: Meier, H. E. M.; Andersson, H. C.; Eilola, K.; Gustafsson, B. G.; Kuznetsov, I.; Müller-Karulis, B.; Neumann, T.; Savchuk, O. P. Bibcode: 2011GeoRL..3824608M Altcode: Using an ensemble of coupled physical-biogeochemical models driven with regionalized data from global climate simulations we are able to quantify the influence of changing climate upon oxygen conditions in one of the numerous coastal seas (the Baltic Sea) that suffers worldwide from eutrophication and from expanding hypoxic zones. Applying various nutrient load scenarios we show that under the impact of warming climate hypoxic and anoxic areas will very likely increase or at best only slightly decrease (in case of optimistic nutrient load reductions) compared to present conditions, regardless of the used global model and climate scenario. The projected decreased oxygen concentrations are caused by (1) enlarged nutrient loads due to increased runoff, (2) reduced oxygen flux from the atmosphere to the ocean due to increased temperature, and (3) intensified internal nutrient cycling. In future climate a similar expansion of hypoxia as projected for the Baltic Sea can be expected also for other coastal oceans worldwide. Title: A grid of S stars MARCS model atmospheres Authors: Van Eck, Sophie; Neyskens, Pieter; Plez, Bertrand; Jorissen, Alain; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt; Gråe Jørgensen, Uffe; Nordlund, Åke Bibcode: 2011JPhCS.328a2009V Altcode: S stars are cool stars of temperatures similar to those of M giants, but their atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing AGB. Despite numerous attempts to link phenomenological spectral classification criteria to physical parameters (Teff, gravity, C/O, [s/Fe], [Fe/H]), the parameter space of S stars is poorly known and this has prevented accurate abundance analysis of S stars until now. Here we present a large grid of S-star model atmospheres. ZrO and TiO band strength indices as well as VJHKL photometry are needed to disentangle the effective temperature, C/O and [s/Fe]. The stellar parameters derived on the basis of low-resolution spectra and photometry are shown to be fairly accurate when compared to high-resolution data of the same stars. The C/O ratio of S stars is found to be between the solar value (0.5) and 0.99, and not 1 as often claimed in the literature. Consistently with stellar evolution expectations, the C/O ratio increases as the effective temperature decreases. Title: Analysis of old very metal rich stars in the solar neighbourhood Authors: Trevisan, M.; Barbuy, B.; Eriksson, K.; Gustafsson, B.; Grenon, M.; Pompéia, L. Bibcode: 2011A&A...535A..42T Altcode: 2011arXiv1109.6304T Context. A sample of mostly old metal-rich dwarf and turn-off stars with high eccentricity and low maximum height above the Galactic plane has been identified. From their kinematics, it was suggested that the inner disk is their most probable birthplace. Their chemical imprints may therefore reveal important information about the formation and evolution of the still poorly understood inner disk.
Aims: To probe the formation history of these stellar populations, a detailed analysis of a sample of very metal-rich stars is carried out. We derive the metallicities, abundances of α elements, ages, and Galactic orbits.
Methods: The analysis of 71 metal-rich stars is based on optical high-resolution échelle spectra obtained with the FEROS spectrograph at the ESO 1.52-m Telescope at La Silla, Chile. The metallicities and abundances of C, O, Mg, Si, Ca, and Ti were derived based on LTE detailed analysis, employing the MARCS model atmospheres.
Results: We confirm the high metallicity of these stars reaching up to [Fe i/H] = 0.58, and the sample of metal-rich dwarfs can be kinematically subclassified in samples of thick disk, thin disk, and intermediate stellar populations. All sample stars show solar α-Fe ratios, and most of them are old and still quite metal rich. The orbits suggest that the thin disk, thick disk and intermediate populations were formed at Galactocentric distances of ~8 kpc, ~6 kpc, and ~7 kpc, respectively. The mean maximum height of the thick disk subsample of Zmax ~ 380 pc, is lower than for typical thick disk stars. A comparison of α-element abundances of the sample stars with bulge stars shows that the oxygen is compatible with a bulge or inner thick disk origin. Our results suggest that models of radial mixing and dynamical effects of the bar and bar/spiral arms might explain the presence of these old metal-rich dwarf stars in the solar neighbourhood.

Observations collected at the European Southern Observatory, La Silla, Chile.Full Tables A.1 to A.4 are only available at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/535/A42 Title: Is the solar spectrum latitude-dependent?. An investigation with SST/TRIPPEL Authors: Kiselman, D.; Pereira, T. M. D.; Gustafsson, B.; Asplund, M.; Meléndez, J.; Langhans, K. Bibcode: 2011A&A...535A..14K Altcode: 2011arXiv1108.4527K Context. In studies of the solar spectrum compared to spectra of solar twin stars, it has been found that the chemical composition of the Sun seems to depart systematically from those of the twins. One possible explanation could be that the effect is caused by the special aspect angle of the Sun when observed from Earth compared with the aspect angles of the twins. This means that a latitude dependence of the solar spectrum, even with the heliocentric angle constant, could lead to the observed effects.
Aims: We explore a possible variation in the strength of certain spectral lines that are used in the comparisons between the composition of the Sun and the twins at loci on the solar disk with different latitudes but at constant heliocentric angle.
Methods: We use the TRIPPEL spectrograph at the Swedish 1-m Solar Telescope on La Palma to record spectra in five spectral regions to compare different locations on the solar disk at a heliocentric angle of 45°. Equivalent widths and other parameters are measured for fifteen different lines representing nine atomic species. Spectra acquired at different times are used in averaging the line parameters for each line and observing position.
Results: The relative variations in equivalent widths at the equator and at solar latitude ~45° are found to be less than 1.5% for all spectral lines studied. Translated into elemental abundances as they would be measured from a terrestrial and a hypothetical pole-on observer, the difference is estimated to be within 0.005 dex in all cases.
Conclusions: It is very unlikely that latitude effects could cause the reported abundance difference between the Sun and the solar twins. The accuracy obtainable in measurements of small differences in spectral line strengths between different solar disk positions is very high, and can be exploited in studies of, e.g. weak magnetic fields or effects of solar activity on atmospheric structure. Title: VizieR Online Data Catalog: Metal rich stars in solar neighbourhood (Trevisan+, 2011) Authors: Trevisan, M.; Barbuy, B.; Eriksson, K.; Gustafsson, B.; Grenon, M.; Pompeia, L. Bibcode: 2011yCat..35350042T Altcode: 2011yCat..35359042T Spectroscopic stellar parameters and abundances of C, O, Mg, Si, Ca, Ti and Ni for 71 stars. U, V, W velocities and orbital parameters derived using the GRINTON integrator (Carraro et al. 2002MNRAS.332..705C, Bedin et al. 2006A&A...460L..27B). Atomic data for Fe I, Fe II, Si I, Ca I, and Ti I lines.

(7 data files). Title: A Grid of MARCS Model Atmospheres for S Stars Authors: van Eck, S.; Neyskens, P.; Plez, B.; Jorissen, A.; Edvardsson, B.; Eriksson, K.; Gustafsson, B.; Jørgensen, U. G.; Nordlund, Å. Bibcode: 2011ASPC..445...71V Altcode: 2010arXiv1011.2092V S-type stars are late-type giants whose atmospheres are enriched in carbon and s-process elements because of either extrinsic pollution by a binary companion or intrinsic nucleosynthesis and dredge-up on the thermally-pulsing AGB. A large grid of S-star model atmospheres has been computed covering the range 2700 ≤ Teff(K) ≤ 4000 with 0.5 ≤ C/O ≤ 0.99. ZrO and TiO band strength indices as well as VJHKL photometry are needed to disentangle Teff, C/O and [s/Fe]. A “best-model finding tool” has been developed using a set of well-chosen indices and checked against photometry as well as low- and high-resolution spectroscopy. It is found that applying M-star model atmospheres (i.e., with a solar C/O ratio) to S stars can lead to errors in Teff up to 400 K. We constrain the parameter space occupied by the S stars of the vast Henize sample in terms of Teff, [C/O] and [s/Fe]. Title: Detached Shells of Dust and Gas around Carbon Stars Authors: Maercker, M.; Olofsson, H.; Eriksson, K.; Gustafsson, B.; Schöier, F. L. Bibcode: 2011ASPC..445..345M Altcode: We present observations of dust-scattered light of the carbon stars U Ant, R Scl, and U Cam taken with the EFOSC2 camera on the ESO 3.6-m telescope and the ACS on the Hubble Space Telescope. The observations show the detached shells around these stars in unprecedented detail, revealing a distinctively clumpy structure in the HST images of R Scl, and a separation of the dust and gas in the ground-based data for U Ant. This allows us to investigate the detached shells and their origin with exceptional precision. Title: Sulphur abundances in halo giants from the [S I] line at 1082 nm and the [S I] triplet around 1045 nm Authors: Jönsson, H.; Ryde, N.; Nissen, P. E.; Collet, R.; Eriksson, K.; Asplund, M.; Gustafsson, B. Bibcode: 2011A&A...530A.144J Altcode: 2011arXiv1104.2148J Context. It is still debated whether or not the Galactic chemical evolution of sulphur in the halo follows the flat trend with [Fe/H] that is ascribed to the result of explosive nucleosynthesis in type II SNe. It has been suggested that the disagreement between different investigations of sulphur abundances in halo stars might be owing to problems with the diagnostics used, that a new production source of sulphur might be needed in the early Universe, like hypernovae, or that the deposition of supernova ejecta into the interstellar medium is time-delayed.
Aims: The aim of this study is to try to clarify this situation by measuring the sulphur abundance in a sample of halo giants using two diagnostics: the S i triplet around 1045 nm and the [S i] line at 1082 nm. The latter of the two is not believed to be sensitive to non-LTE effects. We can thereby minimize the uncertainties in the diagnostic used and estimate the usefulness of the triplet for the sulphur determination in halo K giants. We will also be able to compare our sulphur abundance differences from the two diagnostics with the expected non-LTE effects in the 1045 nm triplet previously calculated by others.
Methods: High-resolution near-infrared spectra of ten K giants were recorded using the spectrometer CRIRES mounted at VLT. Two standard settings were used, one covering the S i triplet and one covering the [S i] line. The sulphur abundances were individually determined with equivalent widths and synthetic spectra for the two diagnostics using tailored 1D model atmospheres and relying on non-LTE corrections from the litterature. Effects of convective inhomogeneities in the stellar atmospheres are investigated.
Results: The sulphur abundances derived from both the [S i] line and the non-LTE corrected 1045 nm triplet favor a flat trend for the evolution of sulphur. In contrast to some previous studies, we saw no "high" values of [S/Fe] in our sample.
Conclusions: We corroborate the flat trend in the [S/Fe] vs. [Fe/H] plot for halo stars found in some previous studies but do not find a scatter or a rise in [S/Fe] as obtained in other works. We find the sulphur abundances deduced from the non-LTE corrected triplet to be somewhat lower than the abundances from the [S i] line, possibly indicating too large non-LTE corrections. Considering 3D modeling, however, they might instead be too small. Moreover, we show that the [S i] line can be used as a sulphur diagnostic down to [Fe/H] ~ -2.3 in giants.

Based on observations collected at the European Southern Observatory, Chile (ESO program 080.D-0675(A)). Title: M67-1194, an unusually Sun-like solar twin in M67 Authors: Önehag, A.; Korn, A.; Gustafsson, B.; Stempels, E.; Vandenberg, D. A. Bibcode: 2011A&A...528A..85O Altcode: 2010arXiv1009.4579O Context. The rich open cluster M67 is known to have a chemical composition close to solar, and an age around 4 Gyr. It thus offers the opportunity to check our understanding of the physics and the evolution of solar-type stars in a cluster environment.
Aims: We present the first spectroscopic study at high resolution, R ≈ 50 000, of the potentially best solar twin, M67-1194, identified among solar-like stars in M67.
Methods: G dwarfs in M67 (d ≈ 900 pc) are relatively faint (V ≈ 15), which makes detailed spectroscopic studies time-consuming. Based on a pre-selection of solar-twin candidates performed at medium resolution by Pasquini et al. (2008, A&A, 489, 677), we explore the chemical-abundance similarities and differences between M67-1194 and the Sun, using VLT/FLAMES-UVES. Working with a solar twin in the framework of a differential analysis, we minimize systematic model errors in the abundance analysis compared to previous studies which utilized more evolved stars to determine the metallicity of M67. The differential approach yields precise and accurate chemical abundances for M67, which enhances the possibility to use this object in studies of the potential peculiarity, or normality, of the Sun.
Results: We find M67-1194 to have stellar parameters indistinguishable from the solar values, with the exception of the overall metallicity which is slightly super-solar ([Fe/H] = 0.023 ± 0.015). An age determination based on evolutionary tracks yields 4.2 ± 1.6 Gyr. Most surprisingly, we find the chemical abundance pattern to closely resemble the solar one, in contrast to most known solar twins in the solar neighbourhood.
Conclusions: We confirm the solar-twin nature of M67-1194, the first solar twin known to belong to a stellar association. This fact allows us to put some constraints on the physical reasons for the seemingly systematic departure of M67-1194 and the Sun from most known solar twins regarding chemical composition. We find that radiative dust cleansing by nearby luminous stars may be the explanation for the peculiar composition of both the Sun and M67-1194, but alternative explanations are also possible. The chemical similarity between the Sun and M67-1194 also suggests that the Sun once formed in a cluster like M67.

Based on data obtained at ESO-VLT, Paranal Observatory, Chile, Program ID 082.D-0726(A).Appendix A is only available in electronic form at http://www.aanda.org Title: Astrophysics: Unexpected warm water Authors: Gustafsson, Bengt Bibcode: 2010Natur.467...35G Altcode: The detection of water vapour in a carbon star has challenged the understanding of ageing stars. The discovery that such water can be warm shows that our knowledge of these objects is still rudimentary. Title: The solar, exoplanet and cosmological lithium problems Authors: Meléndez, J.; Ramírez, I.; Casagrande, L.; Asplund, M.; Gustafsson, B.; Yong, D.; Do Nascimento, J. D.; Castro, M.; Bazot, M. Bibcode: 2010Ap&SS.328..193M Altcode: 2009Ap&SS.tmp..221M; 2009arXiv0910.5845M We review three Li problems. First, the Li problem in the Sun, for which some previous studies have argued that it may be Li-poor compared to other Suns. Second, we discuss the Li problem in planet hosting stars, which are claimed to be Li-poor when compared to field stars. Third, we discuss the cosmological Li problem, i.e. the discrepancy between the Li abundance in metal-poor stars (Spite plateau stars) and the predictions from standard Big Bang Nucleosynthesis. In all three cases we find that the “problems” are naturally explained by non-standard mixing in stars. Title: SIMPLE: a high-resolution near-infrared spectrometer for the E-ELT Authors: Origlia, Livia; Oliva, Ernesto; Maiolino, Roberto; Gustafsson, Bengt; Piskunov, Nikolai; Kochucov, Oleg; Vanzi, Leonardo; Minniti, Dante; Zoccali, Manuela; Hatzes, Artie; Guenther, Eike Bibcode: 2010SPIE.7735E..2BO Altcode: 2010SPIE.7735E..78O SIMPLE is an optimized near IR echelle spectrograph for the E-ELT assisted by adaptive optics. It delivers a complete 0.84-2.5μm spectrum in one exposure with resolution up to R=130,000, nearly diffraction limited pixel scale and limiting magnitudes down to JHK~20. Its most prominent science cases include the study of the intergalactic medium in the early Universe (z>6) and of the atmospheres of exo-planet transiting nearby low mass stars. Title: The chemical composition of solar-type stars in comparison with that of the Sun Authors: Gustafsson, Bengt; Meléndez, Jorge; Asplund, Martin; Yong, David Bibcode: 2010Ap&SS.328..185G Altcode: 2010Ap&SS.tmp...36G The question whether the solar chemical composition is typical for solar-type stars is analysed by comparing the Sun with different stellar samples, including a sample of stars with very similar parameters, solar twins. Although typical in terms of overall metallicity for stars of solar age and galactic orbit, the solar atmosphere is found to have abundances, as compared with solar twins, that indicate that its gas has once been affected by dust formation and dust separation. It is concluded that this may be related to the formation of the solar planetary system and its special properties. Title: Ulysses Dust Detection System V3.1 Authors: Gruen, E.; Krueger, H.; Landgraf, M.; Altobelli, N.; Anweiler, B.; Baguhl, M.; Dermott, S. F.; Dikarev, V.; Divine, N.; Fechtig, H.; Graps, A. L.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horanyi, M.; Kissel, J.; Lindblad, B. -A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Riemann, R.; Schwehm, G.; Siddique, N.; Srama, R.; Staubach, P.; Zook, H. A. Bibcode: 2010PDSS..140.....G Altcode: This data set contains the data from the Ulysses dust detector system (UDDS) from start of mission through the end of mission, 1990-2007. (As the dust detector was turned off after Nov. 30, 2007, this is the last date for which UDDS data is recorded.) Included are the dust impact data, noise data, laboratory calibration data, and location and orientation of the spacecraft and instrument. Title: Three years of Ulysses dust data: 2005 to 2007 Authors: Krüger, H.; Dikarev, V.; Anweiler, B.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 2010P&SS...58..951K Altcode: 2009arXiv0908.1279K The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse ( i=79∘, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in February 1992. Since then it has made almost three revolutions about the Sun. Here we report on the final three years of data taken by the on-board dust detector. During this time, the dust detector recorded 609 dust impacts of particles with masses 10-16g⩽m⩽10-7g, bringing the mission total to 6719 dust data sets. The impact rate varied from a low value of 0.3 per day at high ecliptic latitudes to 1.5 per day in the inner solar system. The impact direction of the majority of impacts between 2005 and 2007 is compatible with particles of interstellar origin; the rest are most likely interplanetary particles. We compare the interstellar dust measurements from 2005/2006 with the data obtained during earlier periods (1993/1994) and (1999/2000) when Ulysses was traversing the same spatial region at southern ecliptic latitudes but the solar cycle was at a different phase. During these three intervals the impact rate of interstellar grains varied by more than a factor of two. Furthermore, in the two earlier periods the grain impact direction was in agreement with the flow direction of the interstellar helium while in 2005/2006 we observed a shift in the approach direction of the grains by approximately 30∘ away from the ecliptic plane. The reason for this shift remains unclear but may be connected with the configuration of the interplanetary magnetic field during solar maximum. We also find that the dust measurements are in agreement with the interplanetary flux model of Staubach et al. (1997) which was developed to fit a 5-year span of Ulysses data. Title: Galileo dust data from the jovian system: 2000 to 2003 Authors: Krüger, H.; Bindschadler, D.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Moissl, R.; Morfill, G. E.; Polanskey, C.; Roy, M.; Schwehm, G.; Srama, R. Bibcode: 2010P&SS...58..965K Altcode: 2009arXiv0908.1051K The Galileo spacecraft was the first man-made satellite of Jupiter, orbiting the planet between December 1995 and September 2003. The spacecraft was equipped with a highly sensitive dust detector that monitored the jovian dust environment between approximately 2 and 370 RJ (jovian radius RJ=71 492 km). The Galileo dust detector was a twin of the one flying on board the Ulysses spacecraft. This is the tenth in a series of papers dedicated to presenting Galileo and Ulysses dust data. Here we present data from the Galileo dust instrument for the period January 2000 to September 2003 until Galileo was destroyed in a planned impact with Jupiter. The previous Galileo dust data set contains data of 2883 particles detected during Galileo's interplanetary cruise and 12 978 particles detected in the jovian system between 1996 and 1999. In this paper we report on the data of additional 5389 particles measured between 2000 and the end of the mission in 2003. The majority of the 21 250 particles for which the full set of measured impact parameters (impact time, impact direction, charge rise times, charge amplitudes, etc.) was transmitted to Earth were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the impact rates frequently exceeded 10 min -1. Surprisingly large impact rates up to 100 min -1 occurred in August/September 2000 when Galileo was far away (≈280RJ) from Jupiter, implying dust ejection rates in excess of 100 kg s -1. This peak in dust emission appears to coincide with strong changes in the release of neutral gas from the Io torus. Strong variability in the Io dust flux was measured on timescales of days to weeks, indicating large variations in the dust release from Io or the Io torus or both on such short timescales. Galileo has detected a large number of bigger micron-sized particles mostly in the region between the Galilean moons. A surprisingly large number of such bigger grains was measured in March 2003 within a four-day interval when Galileo was outside Jupiter's magnetosphere at approximately 350 RJ jovicentric distance. Two passages of Jupiter's gossamer rings in 2002 and 2003 provided the first actual comparison of in-situ dust data from a planetary ring with the results inferred from inverting optical images. Strong electronics degradation of the dust instrument due to the harsh radiation environment of Jupiter led to increased calibration uncertainties of the dust data. Title: Galileo Dust Detection System V4.1 Authors: Krueger, H.; Gruen, E.; Baguhl, M.; Bindschadler, D.; Dermott, S.; Divine, N.; Fechtig, H.; Graps, A.; Gustafson, B.; Hamilton, D.; Hanner, M.; Horanyi, M.; Kissel, J.; Lindblad, B. -A.; Linkert, D.; Linkert, G.; McDonnell, J. A. M.; Mann, I.; Moissl, R.; Morfill, G.; Polanskey, C.; Schwehm, G.; Riemann, R.; Siddique, N.; Srama, R.; Staubach, P.; Zook, H. Bibcode: 2010PDSS..139.....K Altcode: This data set contains the data from the Galileo dust detector system (GDDS) from start of mission through the end of mission. Included are the dust impact data, noise data, laboratory calibration data, and location and orientation of the spacecraft and instrument. Title: High-resolution HST/ACS images of detached shells around carbon stars Authors: Olofsson, H.; Maercker, M.; Eriksson, K.; Gustafsson, B.; Schöier, F. Bibcode: 2010A&A...515A..27O Altcode: 2010arXiv1003.0362O Context. Overall spherically symmetric, geometrically thin gas and dust shells have been found around a handful of asymptotic giant branch (AGB) carbon stars. Their dynamical ages lie in the range of 103 to 104 years. A tentative explanation for their existence is that they have formed as a consequence of mass-loss-rate modulations during a He-shell flash.
Aims: The detached shells carry information on their formation process, as well as on the small-scale structure of the circumstellar medium around AGB stars due to the absence of significant line-of-sight confusion.
Methods: The youngest detached shells, those around the carbon stars R Scl and U Cam, are studied here in great detail in scattered stellar light with the Advanced Survey Camera on the Hubble Space Telescope. Quantitative results are derived assuming optically thin dust scattering.
Results: The detached dust shells around R Scl and U Cam are found to be consistent with an overall spherical symmetry. They have radii of 19.2 arcsec (corresponding to a linear size of 8 × 1016 cm) and 7.7 arcsec (5 × 1016 cm), widths of 1.2 arcsec (5 × 1015 cm) and 0.6 arcsec (4 × 1015 cm), and dust masses of 3 × 10-6 and 3 × 10-7 M_⊙, respectively. The dynamical ages of the R Scl and U Cam shells are estimated to be 1700 and 700 yr, respectively, and the shell widths correspond to time scales of 100 and 50 yr, respectively. Small-scale structure in the form of less than arcsec-sized clumps is clearly seen in the images of the R Scl shell. Average clump dust masses are estimated to be about 2 × 10-9 M_⊙. Comparisons with CO line interferometer data show that the dust and gas shells coincide spatially, within the errors (≤1´´ for U Cam and ≈2´´ for R Scl).
Conclusions: The results are consistent with the interpretation of geometrically thin gas and dust shells formed by a mass-loss eruption during a He-shell flash, and where interaction with a previous wind plays a role as well. The mass loss responsible for the shells must have been remarkably isotropic, and, if wind interaction plays a role, this also applies to the mass loss prior to the eruption. Clumpy structure is present in the R Scl shell, possibly as a consequence of the mass loss itself, but more likely as a consequence of instabilities in the expanding shell.

Based on observations with the NASA/ESA Hubble Space Telescope, obtained at the Space Telescope Science Insitute, which is operated by the AURA, Inc., under NASA contract NAS5-26555. Title: Division III: Planetary Systems Science Authors: Bowell, Edward L. G.; Meech, Karen J.; Williams, Iwan P.; Boss, Alan; Courtin, Régis; Gustafson, Bo Å. S.; Levasseur-Regourd, Anny-Chantal; Mayor, Michel; Spurný, Pavel; Watanabe, Jun-ichi; Consolmagno, Guy J.; Fernández, Julio A.; Huebner, Walter F.; Marov, Mikhail Ya.; Schulz, Rita M.; Valsecchi, Giovanni B.; Witt, Adolf N. Bibcode: 2010IAUTB..27..158B Altcode: The meeting was opened by Ted Bowell, president, at 11 am. The 2006 Division III meetings were reviewed by Guy Consolmagno, secretary; as the minutes of those meetings have already been published, they were assumed to be approved. Title: Commission 36: Theory of Stellar Atmospheres Authors: Asplund, Martin; Puls, Joachim; Landstreet, John; Allende Prieto, Carlos; Ayres, Thomas; Berdyugina, Svetlana; Gustafsson, Bengt; Hubeny, Ivan; Ludwig, Hans Günter; Mashonkina, Lyudmila; Randich, Sofia Bibcode: 2010IAUTB..27..197A Altcode: The members of the Commission 36 Organizing Committee attending the IAU General Assembly in Rio de Janeiro met for a business session on August 7. Both members from the previous (2006-2009) and the new (2009-2012) Organizing Committee partook in the discussions. Past president John Landstreet described the work he had done over the past three years in terms of supporting proposed conferences on the topic. He has also spent significant amount of time establishing an updated mailing list of all >350 members of the commission, which is unfortunately not provided automatically by the IAU. Such a list is critical for a rapid dissemination of information to the commission members and for a correct and smooth running of elections of IAU officials. Everyone present thanked John effusively for all of his hard work over the past three years to stimulate a high level of activity within the discipline. Title: Lithium abundances in Bulge-like SMR stars Authors: Barbuy, Beatriz; Trevisan, M.; Gustafsson, B.; Eriksson, K.; Grenon, M.; Pompéia, L. Bibcode: 2010IAUS..268..325B Altcode: We analyze a sample of 21 super-metal-rich (SMR) stars, using high-resolution échelle spectra obtained with the FEROS Spectrograph at the 1.5m ESO telescope. The metallicities are in the range 0.15 < [Fe/H] < 0.5, 3 of them in common with Pompéia et al. (2002). Geneva photometry, astrometric data from Hipparcos, and radial velocities from CORAVEL are available for these stars. The peculiar kinematics suggests the thin disk close to the bulge as the probable birthplace of these stars (Grenon 1999). From Hipparcos data, it appears that the turnoff of this population indicates an age of 10-11 Gyr (Grenon 1999). Detailed analysis of the sample stars is carried out. Lithium abundances of these stars were derived, and their behaviour with effective temperature is shown. Title: FEROS Abundance Analysis of 21 Bulgelike SMR Stars Authors: Trevisan, Marina; Barbuy, Beatriz; Grenon, M.; Gustafsson, B.; Pompéia, L. Bibcode: 2010IAUS..265..382T Altcode: We analyze a sample of 21 super-metal-rich (SMR) stars, using high-resolution échelle spectra obtained with the Fiber-fed Extended Range Optical Spectrograph at the 1.5m ESO telescope. The metallicities are in the range 0.07 ≤ [Fe/H] ≤ 0.45, 3 of them in common with Pompéia et al. (2009). Geneva photometry, astrometric data from Hipparcos, and radial velocities from CORAVEL are available for these stars. The peculiar kinematics suggests the thin disk close to the bulge as the probable birthplace of these stars (Grenon 1999). From Hipparcos data, it appears that the turnoff of this population indicates an age of 10-11 Gyr (Grenon 1999). Detailed analysis of the sample stars is carried out, and atmospheric parameters are derived from spectroscopic and photometric determinations. Oxygen abundances of these stars are derived, and [O/Fe] overabundances up to +0.35 are found. Title: Are “realistic” model atmospheres realistic enough? Authors: Gustafsson, Bengt Bibcode: 2010IAUS..265..187G Altcode: During the latest decades the number of papers on stellar chemical abundances has increased dramatically. This is basically reflecting the very great achievements in telescope- and spectrometer-construction technology. The analysis of the resulting stellar spectra, however, is still not up to the standard that is offered by the observational methods. Recent significant advances in the analysis methods (i.e., in constructing model atmospheres and model spectra to compare with the observed ones) is reviewed with the emphasis on the application to abundance analysis of late-type stars. It is found that the very considerable progress that have been made beyond mixing-length convection and LTE is a major break-through for physically consistent modeling. Still, however, further steps must be taken, in particular for the cooler stars, before the situation is fully satisifactory. Title: Unprecedented accurate abundances: signatures of other Earths? Authors: Meléndez, Jorge; Asplund, Martin; Gustafsson, Bengt; Yong, David; Ramírez, Iván Bibcode: 2010IAUS..265..412M Altcode: 2009arXiv0910.0875M For more than 140 years the chemical composition of our Sun has been considered typical of solar-type stars. Our highly differential elemental abundance analysis of unprecedented accuracy (~0.01 dex) of the Sun relative to solar twins, shows that the Sun has a peculiar chemical composition with a ≈20% depletion of refractory elements relative to the volatile elements in comparison with solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. A similar study of solar analogs from planet surveys shows that this peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs without detected giant planets show the solar abundance pattern. The peculiarities in the solar chemical composition can be explained as signatures of the formation of terrestrial planets like our own Earth. Title: The detached dust and gas shells around the carbon star U Antliae Authors: Maercker, M.; Olofsson, H.; Eriksson, K.; Gustafsson, B.; Schöier, F. L. Bibcode: 2010A&A...511A..37M Altcode: 2009arXiv0912.2673M Context. Geometrically thin, detached shells of gas have been found around a handful of carbon stars. The current knowledge on these shells is mostly based on CO radio line data. However, imaging in scattered stellar light adds important new information as well as allows studies of the dust shells.
Aims: Previous observations of scattered stellar light in the circumstellar medium around the carbon star U Ant were taken through filters centred on the resonance lines of K and Na. These observations could not separate the scattering by dust and atoms. The aim of this paper is to remedy this situation.
Methods: We have obtained polarization data on stellar light scattered in the circumstellar medium around U Ant through filters which contain no strong lines, making it possible to differentiate between the two scattering agents. Kinematic, as well as spatial, information on the gas shells were obtained through high-resolution echelle spectrograph observations of the KI and NaD lines.
Results: We confirm the existence of two detached shells around U Ant. The inner shell (at a radius of ≈43´´ and a width of ≈2´´) consists mainly of gas, while the outer shell (at a radius of ≈50´´ and a width of ≈7´´) appears to consist exclusively of dust. Both shells appear to have an over-all spherical geometry. The gas shell mass is estimated to be 2 × 10-3~M⊙, while the mass of the dust shell is estimated to be 5 × 10-5~M⊙. The derived expansion velocity, from the KI and NaD lines, of the gas shell, 19.5 km s-1, agrees with that obtained from CO radio line data. The inferred shell age is 2700 years. There is structure, e.g. in the form of arcs, inside the gas shell, but it is not clear whether these are due to additional shells.
Conclusions: Our results support the hypothesis that the observed geometrically thin, detached shells around carbon stars are the results of brief periods of intense mass loss, probably associated with thermal pulses, and subsequent wind-wind interactions. The separation into a gas and a dust shell, with different widths, is most likely the effect of different dynamical evolutions of the two media after their ejection. Title: Phosphorus recycling and burial in Baltic Sea sediments with contrasting redox conditions Authors: Mort, Haydon P.; Slomp, Caroline P.; Gustafsson, Bo G.; Andersen, Thorbjørn J. Bibcode: 2010GeCoA..74.1350M Altcode: In this study, redox-dependent phosphorus (P) recycling and burial at 6 sites in the Baltic Sea is investigated using a combination of porewater and sediment analyses and sediment age dating ( 210Pb and 137Cs). We focus on sites in the Kattegat, Danish Straits and Baltic Proper where present-day bottom water redox conditions range from fully oxygenated and seasonally hypoxic to almost permanently anoxic and sulfidic. Strong surface enrichments of Fe-oxide bound P are observed at oxic and seasonally hypoxic sites but not in the anoxic basins. Reductive dissolution of Fe-oxides and release of the associated P supports higher sediment-water exchange of PO 4 at hypoxic sites (up to ∼800 μmol P m -2 d -1) than in the anoxic basins. This confirms that Fe-bound P in surface sediments in the Baltic acts as a major internal source of P during seasonal hypoxia, as suggested previously from water column studies. Most burial of P takes place as organic P. We find no evidence for significant authigenic Ca-P formation or biogenic Ca-P burial. The lack of major inorganic P burial sinks makes the Baltic Sea very sensitive to the feedback loop between increased hypoxia, enhanced regeneration of P and increased primary productivity. Historical records of bottom water oxygen at two sites (Bornholm, Northern Gotland) show a decline over the past century and are accompanied by a rise in values for typical sediment proxies for anoxia (total sulfur, molybdenum and organic C/P ratios). While sediment reactive P concentrations in anoxic basins are equal to or higher than at oxic sites, burial rates of P at hypoxic and anoxic sites are up to 20 times lower because of lower sedimentation rates. Nevertheless, burial of reactive P in both hypoxic and anoxic areas is significant because of their large surface area and should be accounted for in budgets and models for the Baltic Sea. Title: Chemical abundances of 11 bulge stars from high-resolution, near-IR spectra Authors: Ryde, N.; Gustafsson, B.; Edvardsson, B.; Meléndez, J.; Alves-Brito, A.; Asplund, M.; Barbuy, B.; Hill, V.; Käufl, H. U.; Minniti, D.; Ortolani, S.; Renzini, A.; Zoccali, M. Bibcode: 2010A&A...509A..20R Altcode: 2009arXiv0910.0448R Context. It is debated whether the Milky Way bulge has characteristics more similar to those of a classical bulge than those of a pseudobulge. Detailed abundance studies of bulge stars are important when investigating the origin, history, and classification of the bulge. These studies provide constraints on the star-formation history, initial mass function, and differences between stellar populations. Not many similar studies have been completed because of the large distance and high variable visual extinction along the line-of-sight towards the bulge. Therefore, near-IR investigations can provide superior results.
Aims: To investigate the origin of the bulge and study its chemical abundances determined from near-IR spectra for bulge giants that have already been investigated with optical spectra. The optical spectra also provide the stellar parameters that are very important to the present study. In particular, the important CNO elements are determined more accurately in the near-IR. Oxygen and other α elements are important for investigating the star-formation history. The C and N abundances are important for determining the evolutionary stage of the giants and the origin of C in the bulge.
Methods: High-resolution, near-infrared spectra in the H band were recorded using the CRIRES spectrometer mounted on the Very Large Telescope. The CNO abundances are determined from the numerous molecular lines in the wavelength range observed. Abundances of the α elements Si, S, and Ti are also determined from the near-IR spectra.
Results: The abundance ratios [O/Fe], [Si/Fe], and [S/Fe] are enhanced to metallicities of at least [Fe/H] = -0.3, after which they decline. This suggests that the Milky Way bulge experienced a rapid and early burst of star formation similar to that of a classical bulge. However, a similarity between the bulge trend and the trend of the local thick disk seems to be present. This similarity suggests that the bulge could have had a pseudobulge origin. The C and N abundances suggest that our giants are first-ascent red-giants or clump stars, and that the measured oxygen abundances are those with which the stars were born. Our [C/Fe] trend does not show any increase with [Fe/H], which is expected if W-R stars contributed substantially to the C abundances. No “cosmic scatter” can be traced around our observed abundance trends: the measured scatter is expected, given the observational uncertainties.

Based on observations collected at the European Southern Observatory, Chile (ESO program 079.B-0338(A)). Title: The Peculiar Solar Composition and Its Possible Relation to Planet Formation Authors: Meléndez, J.; Asplund, M.; Gustafsson, B.; Yong, D. Bibcode: 2009ApJ...704L..66M Altcode: 2009arXiv0909.2299M We have conducted a differential elemental abundance analysis of unprecedented accuracy (~0.01 dex) of the Sun relative to 11 solar twins from the Hipparcos catalog and 10 solar analogs from planet searches. We find that the Sun shows a characteristic signature with a ≈20% depletion of refractory elements relative to the volatile elements in comparison with the solar twins. The abundance differences correlate strongly with the condensation temperatures of the elements. This peculiarity also holds in comparisons with solar analogs known to have close-in giant planets while the majority of solar analogs found not to have such giant planets in radial velocity monitoring show the solar abundance pattern. We discuss various explanations for this peculiarity, including the possibility that the differences in abundance patterns are related to the formation of planetary systems like our own, in particular to the existence of terrestrial planets. Title: Assessing the role of the Bothnian Sea phosphorus burial sink Authors: Mort, Haydon P.; Slomp, Caroline P.; Gustafsson, Bo G. Bibcode: 2009GeCAS..73R.908M Altcode: No abstract at ADS Title: Calibration of Strömgren uvby-Hβ photometry for late-type stars - a model atmosphere approach Authors: Önehag, A.; Gustafsson, B.; Eriksson, K.; Edvardsson, B. Bibcode: 2009A&A...498..527O Altcode: 2009A&A...498..527A Context: The use of model atmospheres for deriving stellar fundamental parameters, such as T_eff, log g, and [Fe/H], will increase as we find and explore extreme stellar populations where empirical calibrations are not yet available. Moreover, calibrations for upcoming large satellite missions of new spectrophotometric indices, similar to the uvby-Hβ system, will be needed.
Aims: We aim to test the power of theoretical calibrations based on a new generation of MARCS models by comparisons with observational photomteric data.
Methods: We calculated synthetic uvby-Hβ colour indices from synthetic spectra. A sample of 367 field stars, as well as stars in globular clusters, is used for a direct comparison of the synthetic indices versus empirical data and for scrutinizing the possibilities of theoretical calibrations for temperature, metallicity, and gravity.
Results: We show that the temperature sensitivity of the synthetic (b-y) colour is very close to its empirical counterpart, whereas the temperature scale based upon Hβ shows a slight offset. The theoretical metallicity sensitivity of the m1 index (and for G-type stars its combination with c_1) is somewhat higher than the empirical one, based upon spectroscopic determinations. The gravity sensitivity of the synthetic c1 index shows satisfactory behaviour when compared to obervations of F stars. For stars cooler than the sun, a deviation is significant in the c1-(b-y) diagram. The theoretical calibrations of (b-y), (v-y), and c1 seem to work well for Pop II stars and lead to effective temperatures for globular cluster stars supporting recent claims that atomic diffusion occurs in stars near the turnoff point of NGC 6397.
Conclusions: Synthetic colours of stellar atmospheres can indeed be used, in many cases, to derive reliable fundamental stellar parameters. The deviations seen when compared to observational data could be due to incomplete linelists but are possibly also due to the effects of assuming plane-parallell or spherical geometry and LTE.

Model colours are only available in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/498/527 Title: Bengt Strömgren's Approach to the Galaxy Authors: Gustafsson, Bengt Bibcode: 2009IAUS..254....3G Altcode: The contributions of Bengt Strömgren to the exploration and understanding of the Galactic Disk are sketched. The question what we can learn from his systematic approach is discussed. Title: VizieR Online Data Catalog: Calibration of Stromgren phot. for late-type stars (Onehag+, 2009) Authors: Onehag, A.; Gustafsson, B.; Eriksson, K.; Edvardsson, B. Bibcode: 2009yCat..34980527O Altcode: The file "stellar.dat" contains coordinates (J2000) and identifiers of the comparison stars. Furthermore the stellar parameters: effective temperature (Teff), logarithmic surface gravity (logg), and metallicity with respect to the sun ([Fe/H]) are listed. The reddening corrected Stromgren indices c1 and m1 and the reddening corrected Stromgren (b-y) colours are listed together with the Crawford/Mander H-beta indices.

The file "model.dat" contains data calculated from the MARCS models. The following model parameters are listed: effective temperature (Teff), logarithmic surface gravity (logg), and metallicity with respect to the sun ([Fe/H]). Synthetic Stromgren indices c1 and m1 and synthetic Stromgren (b-y) colours are listed together with the synthetic Crawford/Mander H-beta indices.

(2 data files). Title: Abundances in bulge stars from high-resolution, near-IR spectra. I. The CNO elements observed during the science verification of CRIRES at VLT Authors: Ryde, N.; Edvardsson, B.; Gustafsson, B.; Eriksson, K.; Käufl, H. U.; Siebenmorgen, R.; Smette, A. Bibcode: 2009A&A...496..701R Altcode: 2009arXiv0902.2124R Context: The formation and evolution of the Milky Way bulge is not yet well understood and its classification is ambiguous. Constraints can, however, be obtained by studying the abundances of key elements in bulge stars.
Aims: The aim of this study is to determine the chemical evolution of C, N, O, and a few other elements in stars in the Galactic bulge, and to discuss the sensitivities of the derived abundances from molecular lines.
Methods: High-resolution, near-infrared spectra in the H band were recorded using the CRIRES spectrometer on the Very Large Telescope. Due to the high and variable visual extinction in the line-of-sight towards the bulge, an analysis in the near-IR is preferred. The C, N, and O abundances can all be determined simultaneously from the numerous molecular lines in the wavelength range observed.
Results: The three giant stars in Baade's window presented here are the first bulge stars observed with CRIRES during its science verification observations. We have especially determined the C, N, and O abundances, with uncertainties of less than 0.20 dex, from CO, CN, and OH lines. Since the systematic uncertainties in the derived C, N, and O abundances due to uncertainties in the stellar fundamental parameters, notably T_eff, are significant, a detailed discussion of the sensitivities of the derived abundances is included. We find good agreement between near-IR and optically determined O, Ti, Fe, and Si abundances. Two of our stars show a solar [C+N/Fe], suggesting that these giants have experienced the first dredge-up and that the oxygen abundance should reflect the original abundance of the giants. The two giants fit into the picture, in which there is no significant difference between the oxygen abundance in bulge and thick-disk stars. Our determination of the sulphur abundances is the first for bulge stars. The high [S/Fe] values for all the stars indicate a high star-formation rate in an early phase of the bulge evolution.

Based on observations collected at the European Southern Observatory, Chile (ESO Programme 60.A-9058A).

Table [see full text] is only available in electronic from at http://www.aanda.org Title: Magnetic fields in M dwarf stars from high-resolution infrared spectra Authors: Kochukhov, O.; Heiter, U.; Piskunov, N.; Ryde, N.; Gustafsson, B.; Bagnulo, S.; Plez, B. Bibcode: 2009AIPC.1094..124K Altcode: 2009csss...15..124K Magnetic fields play a central role in the atmospheric properties and variability of active M dwarfs. Information on the strength and structure of magnetic fields in these objects is vital for understanding dynamo mechanisms and magnetically-driven activity of low-mass stars, and for constraining theories of star formation and evolution. We have initiated the first systematic high-resolution survey of magnetically sensitive infrared spectral lines in M dwarf stars using the CRIRES instrument at the ESO VLT. We have completed observations for a sample of 35 active and inactive M dwarfs. Here we report first results of our project, demonstrating a clear detection of magnetic splitting of lines in the spectra of several M dwarfs. We assess diagnostic potential of different Zeeman-sensitive lines in the observed spectral region and apply spectrum synthesis modelling to infer magnetic field properties of selected M dwarfs. Title: Division III: Planetary Systems Sciences Authors: Bowell, Edward L. G.; Meech, Karen J.; Williams, Iwan P.; Boss, Alan P.; Consolmagno, Guy J.; Courtin, Régis; Fernández, Julio A.; Gustafson, Bo Å. S.; Huebner, Walter F.; Levasseur-Regourd, Anny-Chantal; Marov, Mikhail Ya.; Mayor, Michel; Schulz, Rita M.; Spurný, Pavel; Valsecchi, Giovanni B.; Watanabe, Jun-ichi; Williams, Iwan P.; Witt, Adolf N. Bibcode: 2009IAUTA..27..149B Altcode: Division III's activities focus on a broad range of astronomical research on bodies in the solar system (excluding the Sun), on extrasolar planets, and on the search for life in the Universe. Title: Commission 21: Light of the Night Sky Authors: Witt, Adolf N.; Murthy, Jayant; Gustafson, Bo Å. S.; Baggaley, W. Jack; Dwek, Eli; Levasseur-Regourd, Anny-Chantal; Mann, Ingrid; Mattila, Kalevi; Watanabe, Jun-ichi Bibcode: 2009IAUTA..27..171W Altcode: Commission 21 consists of IAU members and consultants with expertise and interest in the study of the light of the night sky and its various diffuse components, at all accessible electromagnetic frequencies. In cosmic distance scales, the subjects of Commission 21 range from airglow and tropospheric scattering in Earth's atmosphere, through zodiacal light in the solar system, including thermal emission from interplanetary dust, integrated starlight in the Milky Way galaxy, diffuse galactic light due to dust scattering in the galactic diffuse interstellar medium, thermal emissions from interstellar dust and free free emission from ionized interstellar gas, to various diffuse extragalactic background sources, including the cosmologically important cosmic microwave background (CMB). Observations of the diffuse night sky brightness at any frequency typically include signals from several of these sources, and it has been the historic mandate of Commission 21 to foster the necessary collaboration of experts from the different astronomical sub-disciplines involved. Title: An attempt to summarize and conclude Authors: Gustafsson, B. Bibcode: 2008PhST..133a4041G Altcode: Some points are made on contributions to the Symposium A Stellar Journey in Uppsala, June 2008. Conclusions are drawn concerning the present status of the stellar-atmosphere research, and a wish list is presented for its further development. Title: A new sample of extremely/ultra metal-poor stars Authors: García Pérez, A. E.; Christlieb, N.; Ryan, S. G.; Beers, T. C.; Aoki, W.; Asplund, M.; Barklem, P. S.; Bessell, M. S.; Eriksson, K.; Frebel, A.; Gustafsson, B.; Korn, A. J.; Nordström, B.; Norris, J. E. Bibcode: 2008PhST..133a4036G Altcode: A sample of 30 very metal-poor stars from the Hamburg-European Southern Observatory (ESO) objective-prism survey have been observed at high spectral resolution at the Very Large Telescope (VLT) using the Ultraviolet and Visual Echelle Spectrograph (UVES). Two of the observed stars are very interesting not only because of their very low iron content, approximately four orders of magnitude lower than the solar value, but also because we detected the neutral lithium resonance line at 670.8 nm. Hydrogen lines suggest that the two observed stars have effective temperatures around 6000 6250 K and according to isochrones, they are either on the main sequence or on the subgiant branch, in which case they would probably be the most metal-poor dwarfs or warm subgiants with lithium detections known. These detections would allow to determine more accurately the slope of the trend of the lithium abundance with [Fe/H] than was possible with samples of unevolved stars restricted to higher metallicities. Title: A grid of MARCS model atmospheres for late-type stars. I. Methods and general properties Authors: Gustafsson, B.; Edvardsson, B.; Eriksson, K.; Jørgensen, U. G.; Nordlund, Å.; Plez, B. Bibcode: 2008A&A...486..951G Altcode: 2008arXiv0805.0554G Context: In analyses of stellar spectra and colours, and for the analysis of integrated light from galaxies, a homogeneous grid of model atmospheres of late-type stars and corresponding flux spectra is needed.
Aims: We construct an extensive grid of spherically-symmetric models (supplemented with plane-parallel ones for the highest surface gravities), built on up-to-date atomic and molecular data, and make it available for public use.
Methods: The most recent version of the MARCS program is used.
Results: We present a grid of about 104 model atmospheres for stars with 2500 K ≤ T_eff ≤ 8000 K, -1 ≤ log g = log (GM/R^2) ≤ 5 (cgs) with various masses and radii, -5 ≤ [Me/H] ≤ +1, with [ α/Fe] = 0.0 and 0.4 and different choices of C and N abundances. This includes “CN-cycled” models with C/N = 4.07 (solar), 1.5 and 0.5, C/O ranging from 0.09 to (normally) 5.0 to also represent stars of spectral types R, S and N, and with 1.0 ≤ ξt ≤ 5 km s-1. We also list thermodynamic quantities (T, P_g, P_e, ρ, partial pressures of molecules, etc.) and provide them on the World Wide Web, as well as calculated fluxes in approximately 108 000 wavelength points. Underlying assumptions in addition to 1D stratification (spherical or plane-parallel) include hydrostatic equilibrium, mixing-length convection and local thermodynamic equilibrium. We discuss a number of general properties of the models, in particular in relation to the effects of changing abundances, of blanketing, and of sphericity. We illustrate positive and negative feedbacks between sphericity and molecular blanketing. We compare the models with those of other available grids and find excellent agreement with plane-parallel models of Castelli & Kurucz (if convection is treated consistently) within the overlapping parameter range. Although there are considerable departures from the spherically-symmetric NextGen models, the agreement with more recent PHOENIX models is gratifying.
Conclusions: The models of the grid show considerable regularities, but some interesting departures from general patterns occur for the coolest models due to the molecular opacities. We have tested a number of approximate “rules of thumb” concerning effects of blanketing and sphericity and often found them to be astonishingly accurate. Some interesting new phenomena have been discovered and explored, such as the intricate coupling between blanketing and sphericity, and the strong effects of carbon enhancement on metal-poor models. We give further details of line absorption data for molecules, as well as details of models and comparisons with observations in subsequent papers. Title: Is the Sun unique as a star—and if so, why? Authors: Gustafsson, B. Bibcode: 2008PhST..130a4036G Altcode: The question whether the Sun is peculiar as compared with other stars in its neigbourhood is revisited. It is concluded that although the Sun is rather normal from many points of view, it departs in several respects from most stars of similar age and galactic orbit. Thus, it is more massive, and the amplitude of the micro-variability of the Sun at visual wavelengths seems unusually small. It also departs from most stars in being a single star, and it may have an unusual planetary system. There are some tentative indications that its chemical composition departs from those of most solar-type stars of similar age. This is discussed and the departures are found not to be significant. I discuss here to what extent these peculiarities may be understood in terms of it being a planet host. Title: INTRODUCTION: Nobel Symposium 135: Physics of Planetary Systems (18 22 June 2007, Lidingö, Stockholm, Sweden) Authors: Piskunov, Nikolai; Rickman, Hans; Gustafsson, Bengt Bibcode: 2008PhST..130a1001P Altcode: Since the discovery of the first planet, orbiting a sun-like star outside of our solar system, astronomy has changed dramatically. This event inspired a wide spectrum of activities not just in observational astronomy but in all fields related to planets from star formation to astrobiology. The discovery itself was the result of long and systematic work on perfecting measuring techniques and collecting data. Once the required level of precision was reached news about extrasolar planets started to appear frequently not just in scientific journals but also in the general media.

Although fast progress is quite obvious in many areas related to planetary sciences for this Nobel symposium, dedicated to the Physics of Planetary Systems, we selected five topics where a number of particularly important breakthroughs happened in the last decade. These are:

detection of exoplanets planet birthplaces: observations and modelling planet formation evolution of planetary systems planet characterization.

We dedicated a full session, consisting of a few review talks and a joint discussion, to each of these topics. The format was a success, but what made this meeting so remarkable was the quality of the talks. We are very thankful to the world leading scientists for coming to Lidingö and making this symposium a truly memorable event. This book contains most of their contributions for you to enjoy.

We are very thankful to the Nobel Foundation for generous sponsorship which made this symposium possible. Title: Phosphorus burial in Baltic Sea sediments with contrasting redox conditions Authors: Mort, Haydon P.; Slomp, Caroline P.; Gustafsson, Bo G. Bibcode: 2008GeCAS..72R.654M Altcode: No abstract at ADS Title: Science cases, wavelength ranges, and strategies for ELTs: some remarks and conclusions Authors: Gustafsson, Bengt Bibcode: 2008SPIE.6986E..0MG Altcode: 2008SPIE.6986E..22G Discussions at the Symposium ELTs: Which wavelengths? in Lund in December 2007 are summarized and in particular comments are made on the relation between the optimization of the presently planned ELTs, and their corresponding background science cases. The division of labour between the ELTs and the JWST is commented on. The need for an ELT (and/or a future Space Telescope) for the optical wavelength region is stressed. Possible strategies for pursuing the ELT projects are commented on. Title: On the Use of Blanketed Atmospheres as Boundary Conditions for Stellar Evolutionary Models Authors: VandenBerg, Don A.; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt Bibcode: 2008ApJ...675..746V Altcode: 2007arXiv0708.1188V Stellar models have been computed for stars having [ Fe/H ] = 0.0 (assuming both the Grevesse & Sauval and Asplund et al. heavy-element mixtures) and -2.0 to determine the effects on the predicted Teff scale of using boundary conditions derived from the latest MARCS model atmospheres. The latter were fitted in a fully consistent way to the interior models at the photosphere and at τ = 100: the resultant evolutionary sequences on the H-R diagram were found to be nearly independent of the chosen fitting point. Tracks were also computed in which the pressure at T = Teff was obtained by integrating the hydrostatic equation together with either the classical gray T(τ , Teff) relation or that derived by Krishna Swamy from an empirical solar atmosphere. Due to the effects of differences in the solar-calibrated values of the mixing-length parameter, αMLT, very similar tracks were obtained for the different treatments of the atmosphere, except at solar abundances, where the models based on the Krishna Swamy T(τ , Teff) relationship predicted ~150 K hotter giant branches than the others, in good agreement with the inferred temperatures of giants in the open cluster M67 from recent (V - K) -Teff relations. Tracks that used new ``scaled solar, differentially corrected'' MARCS atmospheres were found to agree well with those that employed the Krishna Swamy T(τ , Teff) relationship, independently of the assumed metal abundance. (Gray atmospheres are quite different from MARCS models.) Fits of isochrones for [ Fe/H ] = - 2.0 to the CMD of the globular cluster M68, as well as the possibility that αMLT varies with stellar parameters, are also discussed. Title: Hercules-stream stars and the metal-rich thick disk Authors: Bensby, T.; Oey, M. S.; Feltzing, S.; Gustafsson, B. Bibcode: 2008mru..conf...62B Altcode: 2006astro.ph.10754B Using the MIKE spectrograph, mounted on the 6.5 m Magellan/Clay telescope at the Las Campanas observatory in Chile, we have obtained high-resolution spectra for 60 F and G dwarf stars, all likely members of a density enhancement in the local velocity distribution, referred to as the Hercules stream. Comparing with an existing sample of 102 thin and thick disk stars we have used space velocities, detailed elemental abundances, and stellar ages to trace the origin of the Hercules stream. We find that the Hercules stream stars show a wide spread in stellar ages, metallicities, and element abundances. However, the spreads are not random but separate the Hercules stream into the abundance and age trends as outlined by either the thin disk or the thick disk. We hence claim that the major part of the Hercules stream actually are thin and thick disk stars. These diverse properties of the Hercules stream point toward a dynamical origin, probably caused by the Galactic bar. However, we can at the moment not entirely rule out that the Hercules stream could be the remnants of a relatively recent merger event. Title: M 67: a constraint on Z_⊙ and/or on diffusive processes in stellar interiors. Authors: VandenBerg, D. A.; Gustafsson, B.; Edvardsson, B.; Eriksson, K.; Ferguson, J. W. Bibcode: 2008MmSAI..79..759V Altcode: The mass of the lowest mass star that has a convective core throughout the main-sequence phase is predicted to be a fairly sensitive function of Z (especially the CNO abundances). The ∼ 4 Gyr open cluster M 67 thus provides a constraint on Z_⊙ (and the solar metals mix) because (i) it has the same metallicity as the Sun according to high-resolution spectroscopy, and (ii) its turnoff stars have masses just above this lower mass limit. While isochrones computed for Z = 0.0165, assuming the Grevesse & Sauval (1998) heavy-element mixture, are able to reproduce the M 67 color-magnitude diagram satisfactorily, those for the solar abundances derived by M. Asplund et al. (implying Z_⊙ = 0.0125) do not predict a gap near the turnoff where one is observed. These results suggest either that there is a problem with the solar metal abundances derived by Asplund et al. or that the neglect of diffusive processes in the present models is responsible for this difficulty. If the latter is the correct explanation, then M 67 provides an important constraint on the rates of diffusive processes in the deep interiors of stars. Title: Commission 21: Light of the Night Sky Authors: Gustafson, Bo A. S.; Witt, Adolf N.; Lamy, Philippe; Dwek, Eli; Lamy, Philippe; Henry, Richard C.; Mann, Ingrid Bibcode: 2007IAUTB..26..138G Altcode: Applications have been received from Dr. Peter Wheatley (proposed by UK), Prof. Harald Schuh (proposed by Austria), and Dr. Busaba Kramer (proposed by Thailand). All applications were endorsed, with the caveat that Dr. Kramer's application needs to be endorsed by at least one of the other commissions since she has not a publication record in our field. Title: Atomic Diffusion and Mixing in Old Stars. I. Very Large Telescope FLAMES-UVES Observations of Stars in NGC 6397 Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Mashonkina, L.; Barklem, P. S.; Collet, R.; Gustafsson, B.; Piskunov, N. Bibcode: 2007ApJ...671..402K Altcode: 2007arXiv0709.0639K We present a homogeneous photometric and spectroscopic analysis of 18 stars along the evolutionary sequence of the metal-poor globular cluster NGC 6397 ([Fe/H]~-2), from the main-sequence turnoff point to red giants below the bump. The spectroscopic stellar parameters, in particular stellar parameter differences between groups of stars, are in good agreement with broadband and Strömgren photometry calibrated on the infrared flux method. The spectroscopic abundance analysis reveals, for the first time, systematic trends of iron abundance with evolutionary stage. Iron is found to be 30% less abundant in the turnoff point stars than in the red giants. An abundance difference in lithium is seen between the turnoff point and warm subgiant stars. The impact of potential systematic errors on these abundance trends (stellar parameters, the hydrostatic and LTE approximations) is quantitatively evaluated and found not to alter our conclusions significantly. Trends for various elements (Li, Mg, Ca, Ti, and Fe) are compared with stellar structure models including the effects of atomic diffusion and radiative acceleration. Such models are found to describe the observed element-specific trends well, if extra (turbulent) mixing just below the convection zone is introduced. It is concluded that atomic diffusion and turbulent mixing are largely responsible for the subprimordial stellar lithium abundances of warm halo stars. Other consequences of atomic diffusion in old metal-poor stars are also discussed.

Based on observations carried out at the European Southern Observatory (ESO), Paranal, Chile, under program ID 075.D-0125(A). Title: Towards a Satisfactory Understanding of AGB-Star Atmospheres? Authors: Gustafsson, B. Bibcode: 2007ASPC..378...60G Altcode: The understanding and the modelling of the atmospheres of AGB stars are discussed and found to be unsatisfactory for most purposes. A number of developments and possible actions to improve this situation are considered. Title: Carbon Stars in the Bulge -- or Beyond It? Authors: Wahlin, R.; Eriksson, K.; Gustafsson, B. >; Ryde, N.; Westerlund, B.; Lambert, D. L. Bibcode: 2007ASPC..378..410W Altcode: The carbon stars in the direction of the Bulge were recently proposed to belong to the Sagittarius system which, with its lower metallicity, would more easily produce carbon stars. The compositions of the carbon stars might be used to distinguish between true members of the Bulge and members of the Sagittarius stream seen through the Bulge. We present oxygen abundances for a sample of carbon stars in the Sagittarius dwarf galaxy including its tidal stream, and towards the galactic Bulge. The abundances were determined from infrared spectra obtained with the ISAAC spectrometer on VLT (R=1500). We find that the oxygen abundances of the Bulge carbon stars are compatible with membership of the Sagittarius stream, but we also discuss possible scenarios that might explain their abundances if they were true Bulge members. Title: A Constraint on Zsolar from Fits of Isochrones to the Color-Magnitude Diagram of M67 Authors: VandenBerg, Don A.; Gustafsson, Bengt; Edvardsson, Bengt; Eriksson, Kjell; Ferguson, Jason Bibcode: 2007ApJ...666L.105V Altcode: 2007arXiv0708.1172V The mass at which a transition is made between stars that have radiative or convective cores throughout the core H burning phase is a fairly sensitive function of Z (particularly, the CNO abundances). As a consequence, the ~4 Gyr, open cluster M67 provides a constraint on Zsolar (and the solar heavy-element mixture) because (1) high-resolution spectroscopy indicates that this system has virtually the same metal abundances as the Sun, and (2) its turnoff stars have masses just above the lower limit for sustained core convection on the main sequence. In this study, evolutionary tracks and isochrones using the latest MARCS model atmospheres as boundary conditions have been computed for 0.6-1.4 Msolar on the assumption of a metals mix (implying Zsolar~0.0125) based on the solar abundances derived by M. Asplund and collaborators using 3D model atmospheres. These calculations do not predict a turnoff gap where one is observed in M67. No such difficulty is found if the analysis uses isochrones for Zsolar=0.0165, assuming the Grevesse and Sauval mix of heavy elements. Our findings, like the inferences from helioseismology, indicate a problem with the abundances of Asplund and collaborators. However, it is possible that low-Z models with diffusive processes taken into account will be less problematic. Title: A First Study of Giant Stars in the Galactic Bulge based on Crires spectra Authors: Ryde, N.; Edvardsson, B.; Gustafsson, B.; Käufl, H. -U. Bibcode: 2007IAUS..241..260R Altcode: 2007astro.ph..1916R We present our on-going work on the determination of elemental abundances of giants in the Galactic Bulge by means of infrared spectroscopy. We show a preliminarily reduced spectrum and a synthetic spectrum fit of the Bulge giant Arp 4203 recorded with the near-infrared, high-resolution Crires spectrograph mounted on the VLT during its science verification run in August 2006. Abundances derived from this spectrum are discussed. Title: On Stellar Models with Blanketed Atmospheres as Boundary Conditions Authors: Vandenberg, Don A.; Edvardsson, Bengt; Eriksson, Kjell; Gustafsson, Bengt; Ferguson, Jason W. Bibcode: 2007IAUS..241...23V Altcode: No abstract at ADS Title: Libraries of synthetic stellar spectra - or are we building palaces upon sand? Authors: Gustafsson, Bengt; Heiter, Ulrike; Edvardsson, Bengt Bibcode: 2007IAUS..241...47G Altcode: No abstract at ADS Title: Chemical Abundances in Metal-Rich Bulge-like Stars Authors: Pompéia, L.; Barbuy, B.; Grenon, M.; Gustafsson, B. Bibcode: 2007IAUS..241...78P Altcode: No abstract at ADS Title: Exploring the Near-Infrared at High Spatial and Spectral Resolution: First Results from CRIRES Science Verification Authors: Siebenmorgen, Ralf; Smette, Alain; Käufl, Hans Ulrich; Seifahrt, Andreas; Uttenthaler, Stefan; Bik, Arjan; Casali, Mark; Hubrig, Swetlana; Jung, Yves; Kerber, Florian; Melnick, Jorge; Moorwood, Alan; Pirard, Jean-François; Sana, Hugues; Valenti, Elena; Tacconi-Garman, Lowell; Hilker, Michael; Primas, Francesca; Amado, Pedro J.; Carmona, Andrés; van Dishoeck, Ewine F.; Foellmi, Cédric; Goto, Miwa; Gredel, Roland; Günther, Eike; Gustafsson, Bengt; Kurtz, Don; Lidman, Christopher; Linz, Hendrik; Martins, Fabrice; Menten, Karl; Moutou, Claire; Nissen, Poul E.; Nürnberger, Dieter; Reiners, Ansgar Bibcode: 2007Msngr.128...17S Altcode: The VLT cryogenic high-resolution infrared echelle spectrograph CRIRES offers high spatial, spectral and temporal resolution spectroscopy from 1 to 5 μm. Highlights from among the 29 pilot studies of the CRIRES science verification (SV) runs are summarised. Title: The Origin of the Hercules Stream Authors: Oey, M. S.; Bensby, T.; Feltzing, S.; Gustafsson, B. Bibcode: 2007AAS...210.8503O Altcode: 2007BAAS...39..194O We find that the Hercules Stream appears to have a dynamical origin within our own Galaxy. Our measurements of [Mg/Fe] and [Ba/Fe] in 60 Hercules Stream stars show a range of one-tenth solar to super-solar metallicity; across this range, the data are consistent with the abundance patterns of these elements in the Galactic thick and thin disks. Thus, our results favor a dynamical origin, perhaps induced by the Galactic bar, rather than an extragalactic merger origin, for the Hercules Stream. Title: Working Group on Definition of Planet Authors: Williams, Iwan P.; Bowell, Edward L. G.; Tedesco, Edward; Consolmagno, Guy J.; Valsecchi, Giovanni B.; Gustafson, Bo Å.; Mann, Ingrid; Meech, Karen J.; A'Hearn, Michael F.; Boss, Alan P.; Cruikshank, Dale P.; Levasseur-Regourd, Anny-Chantal; Marov, Mikhail; Morrison, David; Tinney, Chris; Marsden, Brian; Stern, Alan; Ticha, Jana; Askness, Kaare Bibcode: 2007IAUTA..26..189W Altcode: The Working Group was formed at the request of the Board of DivisionIII and approved by the IAU Executive committee in March 2004. This was in recognition of the fact that discoveries in the Trans Neptunian region were repeatedly raising the question of "what is a planet". The task of the WG was to investigate the options available and give indications of the level of support and opposition for each if more than one option was emerging. Title: Commission 21: Light of the Night Sky Authors: Gustafson, Bo Å. S.; Witt, Adolf N.; Dwek, E.; Lamy, P.; Henry, R.; Mann, I. Bibcode: 2007IAUTA..26..161G Altcode: Commission 21, one of IAU's smallest commissions, consists of some hundred members and consultants working to understand and describe the light of the night sky with emphasis on the diffuse components. Many more work on these topics without being members of the commission. Light is here defined in its broader sense of electromagnetic radiation of any frequency. The diffuse components of the light of the night sky encompass a variety of physical phenomena over the full range of cosmic distance scales and include scattered light, thermal emission, line emission, and any other emission phenomena producing a diffuse light source. These attract interest not only as scientific topics of study in their own right but also as an unwanted foreground or background against which all other sky phenomena are observed. Commission 21 has for mandate to promote research and availability of results on issues related to the diffuse light of the night sky. This document is a report on activities in this field and is not confined to the activities of its members, no distinction is made between work carried out by commission members and non commission members. The report is organized starting with a summary of the state of broad surveys that provide most of the observations. The report on developments in the various disciplines start with the sources closest to the observer known as airglow and progresses by way of the interplanetary and interstellar mediums to the increasingly distant integrated starlight, diffuse galactic light and diffuse emission in other galaxies ending with the extragalactic background radiation. Title: Disentangling the Hercules Stream Authors: Bensby, T.; Oey, M. S.; Feltzing, S.; Gustafsson, B. Bibcode: 2007ApJ...655L..89B Altcode: 2006astro.ph.12658B Using high-resolution spectra of nearby F and G dwarf stars, we have investigated the detailed abundance and age structure of the Hercules stream. We find that the stars in the stream have a wide range of stellar ages, metallicities, and element abundances. By comparing to existing samples of stars in the solar neighborhood with kinematics typical of the Galactic thin and thick disks, we find that the properties of the Hercules stream distinctly separate into the abundance and age trends of the two disks. Hence, we find it unlikely that the Hercules stream is a unique Galactic stellar population but rather is a mixture of thin and thick disk stars. This points toward a dynamical origin for the Hercules stream, probably caused by the Galactic bar.

Based on observations collected with the MIKE spectrograph on the 6.5 m Magellan Clay telescope at the Las Campanas observatory in Chile. Title: Gaia and Metal-Poor Stars Authors: Gustafsson, B. Bibcode: 2006ASPC..353..387G Altcode: The expected impact of the Gaia mission on our understanding of metal-poor stars and the formation of the Galactic halo is discussed. It is concluded that substantial ground-based efforts will be needed in order to realise the full potential of the Gaia project with its grand volume of high-precision astrometric and photometric stellar data. Title: New Abundances for Old Stars - Atomic Diffusion at Work in NGC 6397 Authors: Korn, A.; Grundahl, F.; Richard, O.; Barklem, P.; Mashonkina, L.; Collet, R.; Piskunov, N.; Gustafsson, B. Bibcode: 2006Msngr.125....6K Altcode: 2006astro.ph.10077K; 2006Msngr.125...10K A homogeneous spectroscopic analysis of unevolved and evolved stars in the metal-poor globular cluster NGC 6397 with FLAMES-UVES reveals systematic trends of stellar surface abundances that are likely caused by atomic diffusion. This finding helps to understand, among other issues, why the lithium abundances of old halo stars are significantly lower than the abundance found to be produced shortly after the Big Bang. Title: Galileo dust data from the jovian system: 1997 1999 Authors: Krüger, H.; Bindschadler, D.; Dermott, S. F.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Moissl, R.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 2006P&SS...54..879K Altcode: The dust detector system on board the Galileo spacecraft recorded dust impacts in circumjovian space during the craft's orbital mission about Jupiter. This is the eighth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January 1997-December 1999 when the spacecraft completed 21 revolutions about Jupiter. In this time interval data were obtained as high resolution realtime science data or recorded data during 449 days (representing 41% of the entire period), or via memory readouts during the remaining times. Because the data transmission rate of the spacecraft was very low, the complete data set (i.e. all parameters measured by the instrument during impact of a dust particle) of only 3% (7625) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data of 2883 particles detected during Galileo's interplanetary cruise and 5353 particles detected in the jovian system in 1996, complete data of 15 861 particles detected by the Galileo dust instrument from 1989 to 1999 are now available. The majority of the detected particles were tiny grains (about 10 nm in radius), most of them originating from Jupiter's innermost Galilean moon Io. They were detected throughout the jovian system and the highest impact rates exceeded 100min-1 (C21 orbit; 01 July 1999). With the new data set the times of onset, cessation and a 180∘ shift in the impact direction of the grains measured during 19 Galileo orbits about Jupiter are well reproduced by simulated 9 nm particles charged up to a potential of +3V, confirming earlier results obtained for only two Galileo orbits (Horányi, M., Grün, E., Heck, A., 1997. Modeling the Galileo dust measurements at Jupiter. Geophys. Res. Lett. 24, 2175-2178). Galileo has detected a large number of bigger particles mostly in the region between the Galilean moons. The average radius of 370 of these grains measured in the 1996-1999 period is about 2μm (assuming spherical grains with density 1gcm-3) and the size distribution rises steeply towards smaller grains. The biggest detected particles have a radius of about 10μm. Title: A probable stellar solution to the cosmological lithium discrepancy Authors: Korn, A. J.; Grundahl, F.; Richard, O.; Barklem, P. S.; Mashonkina, L.; Collet, R.; Piskunov, N.; Gustafsson, B. Bibcode: 2006Natur.442..657K Altcode: 2006astro.ph..8201K The measurement of the cosmic microwave background has strongly constrained the cosmological parameters of the Universe. When the measured density of baryons (ordinary matter) is combined with standard Big Bang nucleosynthesis calculations, the amounts of hydrogen, helium and lithium produced shortly after the Big Bang can be predicted with unprecedented precision. The predicted primordial lithium abundance is a factor of two to three higher than the value measured in the atmospheres of old stars. With estimated errors of 10 to 25%, this cosmological lithium discrepancy seriously challenges our understanding of stellar physics, Big Bang nucleosynthesis or both. Certain modifications to nucleosynthesis have been proposed, but found experimentally not to be viable. Diffusion theory, however, predicts atmospheric abundances of stars to vary with time, which offers a possible explanation of the discrepancy. Here we report spectroscopic observations of stars in the metal-poor globular cluster NGC6397 that reveal trends of atmospheric abundance with evolutionary stage for various elements. These element-specific trends are reproduced by stellar-evolution models with diffusion and turbulent mixing. We thus conclude that diffusion is predominantly responsible for the low apparent stellar lithium abundance in the atmospheres of old stars by transporting the lithium deep into the star. Title: Five years of Ulysses dust data: 2000 2004 Authors: Krüger, H.; Altobelli, N.; Anweiler, B.; Dermott, S. F.; Dikarev, V.; Graps, A. L.; Grün, E.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Landgraf, M.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 2006P&SS...54..932K Altcode: The Ulysses spacecraft has been orbiting the Sun on a highly inclined ellipse ( i=79∘, perihelion distance 1.3 AU, aphelion distance 5.4 AU) since it encountered Jupiter in 1992. Between January 2000 and December 2004, the spacecraft completed almost an entire revolution about the Sun, passing through perihelion in May 2001 and aphelion in July 2004. In this five-year period the dust detector on board recorded 4415 dust impacts. We publish and analyse the complete data set of both raw and reduced data for particles with masses 10-16g⩽m⩽10-7g. Together with 1695 dust impacts recorded between launch of Ulysses and the end of 1999 published earlier (Grün, E., Baguhl, M., Divine, N., Fechtig, H., Hamilton, D.P, Hanner, M.S., Kissel, J., Lindblad, B.A., Linkert, D., Linkert, G., Mann, I., McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Riemann, R., Schwehm, G.H., Siddique, N., Staubach, P., Zook, H.A., 1995a. Two years of Ulysses dust data. Planetary Space Sci. 43, 971-999, Paper III; Krüger, H., Grün, E., Landgraf, M., Baguhl, M., Dermott, S.F., Fechtig, H., Gustafson, B.A., Hamilton, D.P., Hanner, M.S., Horányi, M., Kissel, J., Lindblad, B., Linkert, D., Linkert, G., Mann, I., McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Schwehm, G.H., Srama, R., Zook, H.A., 1995. Three years of Ulysses dust data: 1993 to 1995. Planetary and Space Sci. 47, 363-383, Paper V; Krüger, H., Grün, E., Landgraf, M., Dermott, S.F., Fechtig, H., Gustafson, B.A., Hamilton, D.P., Hanner, M.S., Horányi, M., Kissel, J., Lindblad, B., Linkert, D., Linkert, G., Mann, I., McDonnell, J.A.M., Morfill, G.E., Polanskey, C., Schwehm, G.H., Srama, R., Zook, H.A., 2001b. Four years of Ulysses dust data: 1996 to 1999. Planetary Space Sci. 49, 1303-1324, Paper VII), a data set of 6110 dust impacts detected with the Ulysses sensor between October 1990 and December 2004 is now available. The impact rate measured between 2000 and 2002 was relatively constant with about 0.3 impacts per day showing a maximum at 1.5 per day around ecliptic plane crossing in early-2001. The impact direction of the majority of impacts between 2000 and 2002 is compatible with particles of interstellar origin, the rest are most likely interplanetary particles. In 2003 and 2004 dust stream particles originating from the jovian system dominated the overall impact rate. Twenty-two individual dust streams were measured between November 2002 and December 2004. The observed impact rates are compared with models for interplanetary and interstellar dust. The dust measurements from the entire mission since Ulysses launch give good agreement with the interplanetary flux model of Staubach, P., Grün, E., Jehn, R., 1997. The meteoroid environment near Earth, Adv. Space Res. 19, 301-308. Title: Oxygen abundances in metal-poor subgiants as determined from [O I], O I and OH lines Authors: García Pérez, A. E.; Asplund, M.; Primas, F.; Nissen, P. E.; Gustafsson, B. Bibcode: 2006A&A...451..621G Altcode: 2005astro.ph.12290G The debate on the oxygen abundances of metal-poor stars has its origin in contradictory results obtained using different abundance indicators. To achieve a better understanding of the problem we have acquired high quality spectra with the Ultraviolet and Visual Echelle Spectrograph at VLT, with a signal-to-noise of the order of 100 in the near ultraviolet and 500 in the optical and near infrared wavelength range. Three different oxygen abundance indicators, OH ultraviolet lines around 310.0 nm, the [O i] line at 630.03 nm and the O i lines at 777.1-5 nm were observed in the spectra of 13 metal-poor subgiants with -3.0≤[Fe/H]≤-1.5. Oxygen abundances were obtained from the analysis of these indicators which was carried out assuming local thermodynamic equilibrium and plane-parallel model atmospheres. Abundances derived from O i were corrected for departures from local thermodynamic equilibrium. Stellar parameters were computed using T_eff-vs.-color calibrations based on the infrared flux method and Balmer line profiles, Hipparcos parallaxes and Fe II lines. [O/Fe] values derived from the forbidden line at 630.03 nm are consistent with an oxygen/iron ratio that varies linearly with [Fe/H] as [O/Fe]=-0.09(±0.08)[Fe/H]+0.36(±0.15). Values based on the O i triplet are on average 0.19±0.22 dex(s.d.) higher than the values based on the forbidden line while the agreement between OH ultraviolet lines and the forbidden line is much better with a mean difference of the order of -0.09±0.25 dex(s.d.). In general, our results follow the same trend as previously published results with the exception of the ones based on OH ultraviolet lines. In that case our results lie below the values which gave rise to the oxygen abundance debate for metal-poor stars. Title: The Hamburg/ESO R-process enhanced star survey (HERES). III. HE 0338-3945 and the formation of the r + s stars Authors: Jonsell, K.; Barklem, P. S.; Gustafsson, B.; Christlieb, N.; Hill, V.; Beers, T. C.; Holmberg, J. Bibcode: 2006A&A...451..651J Altcode: 2006astro.ph..1476J We have derived abundances of 33 elements and upper limits for 6 additional elements for the metal-poor ([Fe/H] = -2.42) turn-off star HE 0338-3945 from high-quality VLT-UVES spectra. The star is heavily enriched, by about a factor of 100 relative to iron and the Sun, in the heavy s-elements (Ba, La, ...). It is also heavily enriched in Eu, which is generally considered an r-element, and in other similar elements. It is less enriched, by about a factor of 10, in the lighter s-elements (Sr, Y and Zr). C is also strongly enhanced and, to a somewhat lesser degree, N and O. These abundance estimates are subject to severe uncertainties due to NLTE and thermal inhomogeneities which are not taken into detailed consideration. However, an interesting result, which is most probably robust in spite of these uncertainties, emerges: the abundances derived for this star are very similar to those of other stars with an overall enhancement of all elements beyond the iron peak. We have defined criteria for this class of stars, r+s stars, and discuss nine different scenarios to explain their origin. None of these explanations is found to be entirely convincing. The most plausible hypotheses involve a binary system in which the primary component goes through its giant branch and asymptotic giant branch phases and produces CNO and s-elements which are dumped onto the observed star. Whether the r-element Eu is produced by supernovae before the star was formed (perhaps triggering the formation of a low-mass binary), by a companion as it explodes as a supernova (possibly triggered by mass transfer), or whether it is possibly produced in a high-neutron-density version of the s-process is still unclear. Several suggestions are made on how to clarify this situation. Title: Getting a handle on the origin of the Galactic Bulge Authors: Lambert, David L.; Ryde, Nils; Hinkle, Kenneth; Smith, Verne V.; Gustafsson, Bengt; Edvardsson, Bengt; Asplund, Martin; Johansson, Sveneric; Wahlin, Rurik Bibcode: 2006noao.prop..268L Altcode: The origin, chemical properties, and evolution history of the Galactic Bulge remain poorly understood. Abundance ratios of bulge stars, especially in the [(alpha)/Fe] vs [Fe/H] diagram, serve to constrain the evolutionary models. Measuring, for instance, a high (alpha) over-abundance indicates rapid and early star-formation. Thus, we propose an infrared based study of the (alpha) elements, including oxygen, of ten stars in two low-extinction windows towards the bulge. We will also re-investigate the oxygen abundance trends found from optical spectra of K giants in Baade's window by McWilliam & Rich (2004), which indicate a surprising cession of oxygen production in the bulge for metallicities larger than -0.5. The infrared, with lower extinction and molecular rather than atomic abundance indicators, is a preferred wavelength region to study abundances in bulge stars. Title: The Chemical Composition of Red Giants, AGB Stars and Planetary Nebulae Authors: Gustafsson, Bengt; Wahlin, Rurik Bibcode: 2006IAUS..234..251G Altcode: 2006astro.ph..7218G The determinations of element abundances in red-giant stars and in particular in AGB stars are reviewed and the resulting abundances are compared with those obtained for planetary nebulae in the Galaxy and in nearby galaxies. The problems, possibilities and implications of such comparisons when estimating yields from low-mass and intermediate-mass stars are illustrated and commented on. Title: Carbon stars in local group dwarf galaxies: C and O abundances Authors: Wahlin, R.; Eriksson, K.; Gustafsson, B.; Hinkle, K. H.; Lambert, D. L.; Ryde, N.; Westerlund, B. Bibcode: 2006MmSAI..77..955W Altcode: 2006astro.ph..5244W We present abundances of carbon and oxygen as well as abundance ratios 12C/13C for a sample of carbon stars in the LMC, SMC, Carina, Sculptor and Fornax dwarf galaxies. The overall metallicities in these dwarf galaxies are lower than in the galactic disc. The observations cover most of the AGB and we discuss the abundance patterns in different regions along the AGB. The abundances are determined from infrared spectra obtained with the ISAAC spectrometer on VLT (R=1500) and the Phoenix Spectrometer on Gemini South (R=50000). The synthetic spectra used in the analysis were computed with MARCS model atmospheres. We find that the oxygen abundance is decreasing with decreasing overall metallicity of the system while the C/O ratio at a given evolutionary phase is increasing with decreasing oxygen abundance.

Based on observations collected at the European Southern Observatory, Paranal, Chile (ESO Programme 70.D-0414 & 072.D-0501) Title: Pinning Down Gravitational Settling Authors: Korn, A. J.; Piskunov, N.; Grundahl, F.; Barklem, P.; Gustafsson, B. Bibcode: 2006cams.book..294K Altcode: 2006astro.ph..8338K We analyse high-resolution archival UVES data of turnoff and subgiant stars in the nearby globular cluster NGC6397 ([Fe/H]≈-2). Balmer-profile analyses are performed to derive reddening-free effective temperatures. Due to the limited S/N and uncertainties related to blaze removal, we find the data quality insufficient to exclude the existence of gravitational settling. If the newly derived effective temperatures are taken as a basis for an abundance analysis, the photospheric iron (Fe ii) abundance in the turnoff stars is 0.11 dex lower than in the (well-mixed) subgiants. Title: An investigation of Titan's aerosols using microwave analog measurements and radiative transfer modeling Authors: Thomas-Osip, J. E.; Gustafson, B. Å. S.; Kolokolova, L.; Xu, Y. -L. Bibcode: 2005Icar..179..511T Altcode: A combination of laboratory experiments, theoretical modeling, and spacecraft observations is employed to characterize the aerosols in the atmosphere of Titan. The scattering properties of model aerosols were measured using the Microwave Analog Light Scattering Facility at the University of Florida and complemented with theoretical modeling of single scattering characteristics and radiative transfer in Titan's atmosphere. This study compares these modeling results with photopolarimetric observations made over a range of phase angles by the Pioneer 11 and Voyagers 1 and 2 spacecraft. Important results of this work include a survey of the scattering properties of different particle morphologies and compositions necessary to accurately interpret these observations without introducing non-physical assumptions about the particles or requiring additional free parameters to the radiative transfer models. Previous studies use calculation methods which, due to computing memory and processing time requirements, a priori exclude much of the parameter space that the microwave analog laboratory is ideal for exploring. The goal of the present work, to directly constrain aerosol physical characteristics, is addressed by studying in a consistent manner how a variety of particle morphologies and refractive indices affect the polarization and intensity reflected by Titan's atmosphere. Based on comparisons of model results to spacecraft observations, many model morphologies are excluded from further consideration. The most plausible physical particle models suggest that a combination of Rayleigh-like single particles and aggregates that are larger than those previously suggested and investigated [West, R.A., Smith, P.H., 1991. Evidence for aggregate particles in the atmospheres of Titan and Jupiter. Icarus 90, 330-333; Rannou, P., Cabane, M., Botet, R., Chassefière, E., 1997. A new interpretation of scattered light measurements at Titan's limb. J. Geophys. Res. 102, 10997-11013] provide the best fit to the existing data. Additional laboratory experiments and more refined modeling awaits the results of the new rich observational dataset from the Cassini/Huygens encounter with Titan. Title: Scattering by "Bird's-Nest"-type Material and Large Dust Aggregates: Microwave Analogue Measurements Authors: Gustafson, B. Å. S.; Espy, A. J. Bibcode: 2005LPICo1280...65G Altcode: No abstract at ADS Title: Chemical abundances in 43 metal-poor stars Authors: Jonsell, K.; Edvardsson, B.; Gustafsson, B.; Magain, P.; Nissen, P. E.; Asplund, M. Bibcode: 2005A&A...440..321J Altcode: 2005astro.ph..5118J We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni, and Ba for 43 metal-poor field stars in the solar neighbourhood, most of them subgiants or turn-off-point stars with iron abundances [Fe/H] ranging from -0.4 to -3.0. About half of this sample has not been spectroscopically analysed in detail before. Effective temperatures were estimated from uvby photometry, and surface gravities primarily from Hipparcos parallaxes. The analysis is differential relative to the Sun, and was carried out with plane-parallel MARCS models. Various sources of error are discussed and found to contribute a total error of about 0.1-0.2 dex for most elements, while relative abundances, such as [Ca/Fe], are most probably more accurate. For the oxygen abundances, determined in an NLTE analysis of the 7774 Å triplet lines, the errors may be somewhat larger. We made a detailed comparison with similar studies and traced the reasons for the, in most cases, relatively small differences. Among the results we find that [O/Fe] possibly increases beyond [Fe/H] = -1.0, though considerably less so than in results obtained by others from abundances based on OH lines. We did not trace any tendency toward strong overionization of iron, and find the excesses, relative to Fe and the Sun, of the α elements Mg, Si, and Ca to be smaller than those of O. We discuss some indications that also the abundances of different α elements relative to Fe vary and the possibility that some of the scatter around the trends in abundances relative to iron may be real. This may support the idea that the formation of Halo stars occurred in smaller systems with different star formation rates. We verify the finding by Gratton et al. (2003b, A&A, 406, 131) that stars that do not participate in the rotation of the galactic disk show a lower mean and larger spread in [ α/Fe] than stars participating in the general rotation. The latter stars also seem to show some correlation between [ α/Fe] and rotation speed. We trace some stars with peculiar abundances, among these two Ba stars, HD 17072 and HD 196944, the second already known to be rich in s elements. Finally we advocate that a spectroscopic study of a larger sample of halo stars with well-defined selection criteria is very important, in order to add to the very considerable efforts that various groups have already made. Title: Light Scattering as a Diagnostic for Asteroid Structure Authors: Espy, A. J.; Gustafson, B. A. S. Bibcode: 2005DPS....37.1508E Altcode: 2005BAAS...37..640E With the identification of the Veritas family as the source of the 9.35 degree dust band of the Zodiacal cloud (Nesvory, et. al 2003), instead of the formerly assigned Eos, we are presented with a new means to study the Veritas family and its precursor asteroid. When an asteroid breaks up, the larger pieces remain together on the same orbit and may reassemble into what is known as a rubble pile. The smaller (sub-millimeter to micron sized) particles, however, experience a stronger perturbation from the solar radiation pressure and these particles migrate to the zodiacal cloud, rather than remaining with the rubble pile. The light scattering of this corresponding band of the zodiacal cloud can be studied for information on the dust particles comprising it, specifically their size and structure, and thus also their precursor asteroid. Using the unique capability of the Microwave Scattering Facility (Gustafson 1996), models of these dust particles are created and the scattering by these particles is measured, specifically the intensities and polarizations. The models are based on the currently known data for the Veritas family, i.e. taxonomic class, tensile strength(calculated from light curves), break-up epochs (obtained from theoretical orbital integrations), and albedo dispersion. Our current hypothesis is that the Veritas precursor was NOT differentiated, but rather it was an aggregate of interstellar grains like the Bird's Nest model of dust proposed by Greenberg and Gustafson(1981). The Bird's Nest model represents the dust as pieces of aggregated nebular dust from which water ice has sublimated. We expect to find structure in the zodiacal dust on the scale of the size of the interstellar grains, 0.1-0.7 microns. If, however, the precursor WAS differentiated then the bulk material in the dust should appear homogeneous (for full differentiation) or show struucture on a different size scale (for partial differentiation). We present here our method and first results. Title: Stochastic chemical enrichment in metal-poor systems. II. Abundance ratios and scatter Authors: Karlsson, T.; Gustafsson, B. Bibcode: 2005A&A...436..879K Altcode: 2005astro.ph..4617K A stochastic model of the chemical enrichment of metal-poor systems by core collapse supernovae is used to study the scatter in stellar abundance ratios. Large-scale mixing of the enriched material by turbulent motions and cloud collisions in the interstellar medium, and infall of pristine matter are taken into account. The resulting scatter in abundance ratios, e.g. as functions of the overall metallicity, is demonstrated to be crucially dependent on the as yet uncertain supernovae yields. The observed abundance ratios and their scatters therefore have diagnostic power as regards the yields. The relatively small star-to-star scatter observed in many chemical abundance ratios, e.g. by Cayrel et al. (2004) for stars down to [Fe/H]= -4, is tentatively explained by the averaging of a large number of contributing supernovae and by the cosmic selection effects favoring contributions from supernovae in a certain mass range for the most metal-poor stars. The scatter in observed abundances of α-elements is understood in terms of observational errors only, while additional spread in yields or sites of nucleosynthesis may affect the odd-even elements Na and Al. For the iron-group elements we find some systematic deviations from observations in abundance ratios, such as systematically too high predicted Cr/Fe and Cr/Mg ratios, as well as differences between the different sets of yields, both in terms of predicted abundance ratios and scatter. The semi-empirical yields recently suggested by Francois et al. (2004) are found to lead to scatter in abundance ratios significantly greater than observed, when applied in the inhomogeneous models. "Spurs", very narrow sequences in abundance-ratio diagrams, may disclose a single-supernova origin of the elements of the stars on the sequence. Verification of the existence of such features, called single supernova sequences (SSSs), is challenging. This will require samples of several hundred stars with abundance ratios observed to accuracies of 0.05 dex or better. Title: VizieR Online Data Catalog: Chemical abundances in 43 metal-poor stars (Jonsell+, 2005) Authors: Jonsell, K.; Edvardsson, B.; Gustafsson, B.; Magain, P.; Nissen, P. E.; Asplund, M. Bibcode: 2005yCat..34400321J Altcode: Data from an analysis of 43 metal-poor field stars with iron abundances [Fe/H] ranging from -0.4 to -3.0dex are presented here. Photometric data, stellar velocities, masses, fundamental parameters, spectral classifications and notations of possible binarity are given. Tables with line data for O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni and Ba, equivalent widths and resulting abundances are also given.

(4 data files). Title: Cool stars in the Gaia photometric system Authors: Heiter, U.; Piskunov, N.; Gustafsson, B.; Jordi, C.; Carrasco, J. M. Bibcode: 2005ESASP.560..635H Altcode: 2005csss...13..635H No abstract at ADS Title: Carbon stars in local group dwarf galaxies: C & O abundances Authors: Wahlin, R.; Eriksson, K.; Gustafsson, B.; Hinkle, K. H.; Lambert, D. L.; Ryde, N.; Westerlund, B. Bibcode: 2005ESASP.560.1017W Altcode: 2005csss...13.1017W No abstract at ADS Title: Concluding remarks Authors: Gustafsson, Bengt Bibcode: 2005IAUS..228..603G Altcode: Attempts are made to summarize some main points and results discussed at the IAU Symposium No. 228 in Paris, May 2005. It is concluded that, although the situation in areas pioneered by F. and M. Spite is nowdays rather complex, some important progress has recently been made, and more is expected to occur within the next few years if the level of ambition in the astronomical community is kept at the high level set by the pioneers. Title: Oxygen abundances in metal-poor subgiants Authors: García Pérez, A. E.; Asplund, M.; Primas, F.; Nissen, P. E.; Gustafsson, B. Bibcode: 2005IAUS..228..257G Altcode: 2005IAUS..228..257P There seems to be no consensus on the [O/Fe] values found in metal-poor stars nor their trend with metallicity: different indicators give different results. We present here [O/Fe] derived from three different oxygen abundance indicators ([OI], OI and OH UV lines) for a sample of thirteen subgiant stars with metallicities in the range -3≤[Fe/H]≤-1.5. Oxygen and iron abundances were determined from the analysis of high S/N spectra acquired with the UVES spectrograph at VLT. We found good agreement between [O/Fe] estimates based on OH and the estimates based on [Oi] (mean difference∼-0.09±0.25(s.d.)), although the scatter is not insignificant. Unfortunately, good agreement is not reached for the third indicator (mean difference∼0.19±0.22(s.d.)). Our [OI] and OH-based estimates do not show a well defined linear trend with metallicity. Another interesting result is that the abundances based on molecular lines ([O/Fe]∼0.45) are in general lower than previous published results for turn-off stars even though a lower solar oxygen abundance (A(O)=8.74) was assumed. Title: Stochastic chemical enrichment in the early Galaxy Authors: Karlsson, Torgny; Gustafsson, Bengt Bibcode: 2005IAUS..228..231K Altcode: A stochastic model of the chemical enrichment of metal-poor systems by core-collapse supernovae is used to study the scatter in relative elemental abundances in extremely metal-poor stars. The resulting scatter in abundance ratios is demonstrated to be crucially dependent on the as yet uncertain supernovae yields. The relatively small star-to-star scatter observed in many of these abundance ratios, e.g. by Cayrel et al. (2004), is tentatively explained by the averaging of a large number of contributing supernovae and by the cosmic selection effects favoring contributions from supernovae in a certain mass range for the most metal-poor stars. "Spurs", very narrow sequences in abundance-ratio diagrams, may disclose a single-supernova origin of the elements of the stars on the sequence and would thus be an indication of an unmixed interstellar medium (ISM). Verification of the existence of such features, called single supernova sequences (SSSs), is challenging. This will require samples of several hundred stars with abundance ratios observed to accuracies of 0.05 dex or better. Title: Phoenix Spectra of Carbon Stars in the LMC Authors: Wahlin, Rurik; Eriksson, Kjell; Gustafsson, Bengt; Hinkle, Kenneth; Lambert, David; Ryde, Nils; Westerlund, Bengt Bibcode: 2005hris.conf..439W Altcode: We present high-resolution, IR-spectra of Carbon stars in the LMC obtained with the Phoenix spectrometer on the Gemini South 8-meter telescope. This is part of an ongoing project where CNO abundances and 12C/13C ratios of Carbon Stars are determined in Local-Group dwarf galaxies of different metallicities. The spectra obtained so far cover two 20 cm 1 wide spectral regions in the H and K bands. The bands contain lines from CN, C2, and CO, with 12C and 13C isotopes, and several atomic lines. The spectra are analyzed with synthetic spectra of model atmospheres from the MARCS spherical-model-atmosphere code. Title: The Abundance of Elements in Cool Stars, as Determined from High-Resolution 1 5 μm Spectroscopy Authors: Ryde, Nils; Gustafsson, Bengt; Eriksson, Kjell; Wahlin, Rurik Bibcode: 2005hris.conf..365R Altcode: 2004astro.ph..7340R We review the field of abundance determinations of elements in cool stars, with special interest paid to determinations based on analyses of high-resolution, 1 5 μm spectra. We discuss the current status, problems, and challenges of exploring high-resolution, near-infrared spectra. In particular, advantages and drawbacks are pointed out. A few examples of current, chemical-abundance determinations are highlighted and, finally, we discuss the development and future prospects of the field. Title: Chemical abundances in 43 metal-poor stars Authors: Gustafsson, Bengt; Asplund, Martin; Edvardsson, Bengt; Jonsell, Karin; Magain, Pierre; Nissen, Poul Erik Bibcode: 2005IAUS..228..259G Altcode: We have derived abundances of O, Na, Mg, Al, Si, Ca, Sc, Ti, V, Cr, Fe, Ni and Ba for 43 metal-poor field stars, mostly stars at the turn-off point and on the subgiant branch, in the interval {-}3.0{[Fe/H]{. The analysis is differential relative to the Sun. Oxygen abundances, with consideration of NLTE effects, were derived from the OI 777.4 nm triplet lines. We find [O/Fe] to gradually increase with decreasing [Fe/H], though considerably slower than has earlier been obtained from OH lines in the UV. A scatter in [O,Mg,Ca,Ti/Fe] at a given [Fe/H] is found and we argue that this scatter is partly real. The deviations from the mean trends of abundance ratios vs [Fe/H] are found to correlate in non-trivial ways for different abundances. Similar trends are found from results of accurate studies by other groups. This seems to give further evidence for the hypothesis that the stars once formed in different subsystems, with different star-formation rates.The paper is in press in A&A, may be obtained as astro-ph/0505118. Title: Subgiants as probes of galactic chemical evolution Authors: Thorén, P.; Edvardsson, B.; Gustafsson, B. Bibcode: 2004A&A...425..187T Altcode: 2004astro.ph..7260T Chemical abundances for 23 candidate subgiant stars have been derived with the aim at exploring their usefulness for studies of galactic chemical evolution. High-resolution spectra from ESO CAT-CES and NOT-SOFIN covered 16 different spectral regions in the visible part of the spectrum. Some 200 different atomic and molecular spectral lines have been used for abundance analysis of ∼30 elemental species. The wings of strong, pressure-broadened metal lines were used for determination of stellar surface gravities, which have been compared with gravities derived from HIPPARCOS parallaxes and isochronic masses. Stellar space velocities have been derived from HIPPARCOS and Simbad data, and ages and masses were derived with recent isochrones. Only 12 of the stars turned out to be subgiants, i.e. on the ``horizontal'' part of the evolutionary track between the dwarf- and the giant stages. The abundances derived for the subgiants correspond closely to those of dwarf stars. With the possible exceptions of lithium and carbon we find that subgiant stars show no ``chemical'' traces of post-main-sequence evolution and that they are therefore very useful targets for studies of galactic chemical evolution.

Based on observations made at ESO, La Silla.

Based on observations made at NOT, La Palma.

Tables 1 and 2 are only available in electronic form at http://www.edpsciences.org Title: On the Oxygen Abundance of HE 0107-5240 Authors: Bessell, M. S.; Christlieb, N.; Gustafsson, B. Bibcode: 2004ApJ...612L..61B Altcode: 2004astro.ph..1450B We have determined the oxygen abundance of HE 0107-5240 from UV-OH lines detected in VLT/UVES spectra. Using a plane-parallel LTE model atmosphere, we derive [O/Fe]=+2.3, and a similar analysis of CD -38°245 yields [O/Fe]=+0.9. We estimate systematic errors due to three-dimensional effects to be on the order of 0.3-0.4 dex. That is, our derived O abundances are likely overestimates: effects from thermal inhomogeneities due to convection may require that the abundances should be reduced by 0.3-0.4 dex or even more. Radial velocity data for HE 0107-5240 based on high-resolution spectra show that over a time span of 373 days, the radial velocity was constant at 44.5 km s-1, with a 1 σ scatter of the measurements of 0.5 km s-1. However, it cannot yet be ruled out that HE 0107-5240 is a very long period and/or low amplitude binary. These results provide new constraints on scenarios for the origin of the abundance pattern of HE 0107-5240. In particular, it seems unlikely that the large overabundances of CNO have been produced in a medium-mass asymptotic giant branch star that later evolved into a white dwarf. The oxygen abundance of HE 0107-5240 is significantly smaller than the prediction of Umeda & Nomoto from calculated yields of an ~25 Msolar Population III star exploding as a supernova of low explosion energy (Eexp=3×1050 ergs) with mixing and fallback. The scenario of Limongi et al., involving two Population III supernovae, predicts an oxygen abundance of [O/Fe]=+4.1 for HE 0107-5240, in strong contradiction to the observed value. In conclusion, none of the above-mentioned scenarios, in their present realizations, can satisfactorily explain the abundance pattern of HE 0107-5240.

Based on observations collected at the European Southern Observatory, Paranal, Chile (proposal 70.D-0009). Title: The R Coronae Borealis stars: carbon abundances from forbidden carbon lines Authors: Pandey, Gajendra; Lambert, David L.; Rao, N. Kameswara; Gustafsson, Bengt; Ryde, Nils; Yong, David Bibcode: 2004MNRAS.353..143P Altcode: 2004MNRAS.tmp..228P; 2004astro.ph..5600P Spectra of several R Coronae Borealis (RCB) stars at maximum light have been examined for the [CI] 9850- and 8727-Åabsorption lines. The 9850-Åline is variously blended with an FeII and CN lines, but positive identifications of the [CI] line are made for RCrB and SUTau. The 8727-Åline is detected in the spectrum of the five stars observed in this wavelength region. Carbon abundances are derived from the [CI] lines using the model atmospheres and atmospheric parameters used by Asplund et al.

Although the observed strength of a CI line is constant from cool to hot RCB stars, the strength is lower than predicted by an amount equivalent to a factor of 4 reduction of the gf-value of a line. Asplund et al. dubbed this `the carbon problem' and discussed possible solutions.

The [CI] 9850-Åline seen clearly in RCrB and SUTau confirms the magnitude of the carbon problem revealed by the CI lines. The [CI] 8727-Åline measured in five stars shows an enhanced carbon problem. The gf-value required to fit the observed [CI] 8727-Åline is a factor of 15 less than the well-determined theoretical gf-value. We suggest that the carbon problem for all lines may be alleviated to some extent by a chromospheric-like temperature rise in these stars. The rise far exceeds that predicted by our non-local thermodynamic equilibrium calculations, and requires a substantial deposition of mechanical energy. Title: VizieR Online Data Catalog: Chemical abundances of 23 subgiants & giants (Thoren+, 2004) Authors: Thoren, P.; Edvardsson, B.; Gustafsson, B. Bibcode: 2004yCat..34250187T Altcode: Chemical abundances, stellar parameters, and atomic and molecular line data are given for a study of 23 subgiant and giant stars in the solar vicinity. With the exception of Li and possibly C we show that subgiant stars show no "chemical" traces of post-main-sequence evolution and that they are therefore and because of their simple age dating very useful targets for studies of galactic chemical evolution.

(3 data files). Title: HE 0107-5240, a Chemically Ancient Star. I. A Detailed Abundance Analysis Authors: Christlieb, N.; Gustafsson, B.; Korn, A. J.; Barklem, P. S.; Beers, T. C.; Bessell, M. S.; Karlsson, T.; Mizuno-Wiedner, M. Bibcode: 2004ApJ...603..708C Altcode: 2003astro.ph.11173C We report on a detailed abundance analysis of HE 0107-5240, a halo giant with [Fe/H]NLTE=-5.3. This star was discovered in the course of follow-up medium-resolution spectroscopy of extremely metal-poor candidates selected from the digitized Hamburg/ESO objective-prism survey. On the basis of high-resolution VLT/UVES spectra, we derive abundances for eight elements (C, N, Na, Mg, Ca, Ti, Fe, and Ni) and upper limits for another 12 elements. A plane-parallel LTE model atmosphere has been specifically tailored for the chemical composition of HE 0107-5240. Scenarios of the origin of the abundance pattern observed in the star are discussed. We argue that HE 0107-5240 is most likely not a post-asymptotic giant branch star and that the extremely low abundances of the iron-peak and other elements are not due to selective dust depletion. The abundance pattern of HE 0107-5240 can be explained by preenrichment from a zero-metallicity Type II supernova (SN II) of 20-25 Msolar, plus either self-enrichment with C and N or production of these elements in the asymptotic giant branch phase of a formerly more massive companion, which is now a white dwarf. However, significant radial velocity variations have not been detected within the 52 days covered by our moderate- and high-resolution spectra. Alternatively, the abundance pattern can be explained by enrichment of the gas cloud from which HE 0107-5240 formed by a 25 Msolar first-generation star exploding as a subluminous SN II, as proposed by Umeda & Nomoto. We discuss consequences of the existence of HE 0107-5240 for low-mass star formation in extremely metal-poor environments and for currently ongoing and future searches for the most metal-poor stars in the Galaxy.

Based on observations collected at the European Southern Observatory, Paranal, Chile (proposal 268.D-5745). Title: Physical properties of cometary dust from light scattering and thermal emission Authors: Kolokolova, L.; Hanner, M. S.; Levasseur-Regourd, A. -Ch.; Gustafson, B. Å. S. Bibcode: 2004come.book..577K Altcode: This chapter explores how physical properties of cometary dust (size distribution, composition, and grain structure) can be obtained from characteristics of the electromagnetic radiation that the dust scatters and emits. We summarize results of angular and spectral observations of brightness and polarization in continuum as well as thermal emission studies. We review methods to calculate light scattering starting with solutions to Maxwell's equations as well as approximations and specific techniques used for the interpretation of cometary data. Laboratory experiments on light scattering and their results are also reviewed. We discuss constraints on physical properties of cometary dust based on the results of theoretical and experimental simulations. At the present, optical and thermal infrared observations equally support two models of cometary dust: (1) irregular polydisperse particles with a predominance of submicrometer particles, or (2) porous aggregates of submicrometer particles. In both models the dust should contain silicates and some absorbing material. Comparison with the results obtained by other than lightscattering methods can provide further constraints. Title: Atmospheres of AGB Stars Authors: Gustafsson, Bengt; Höfner, Susanne Bibcode: 2004agbs.book..149G Altcode: No abstract at ADS Title: Laboratory Simulations Authors: Huebner, W. F.; Walker, J.; Gustafson, B. Bibcode: 2004cosp...35.2021H Altcode: 2004cosp.meet.2021H Geophysical properties of near-Earth objects (NEOs) can best be studied using radio tomography and seismology. Reflection and transmission radio tomography is best suited for measuring the complex electric permittivity of poorly conducting materials to reveal the internal structure of NEOs. Such NEOs are primarily comet nuclei and carbonaceous asteroids. Seismic experiments are most suitable for studying elastic properties of consolidated materials to reveal material strengths of stony and iron-nickel asteroids. Thus, the two methods are complementary for investigating comets and asteroids of all types. Analysis of reflection and transmission radio tomography of heterogeneous irregular shaped bodies is very difficult. Scattering by internal and outer boundaries, differences in the refractive indices of heterogeneous materials, and attenuation by electric conductivity complicate the analyses. For this reason laboratory simulations with scaled objects and scaled wavelengths is extremely useful to check the reliability of inversion techniques of radio signals to arrive at the interior structure of an NEO. Another approach to obtaining quantitative information on the composition and structure of an NEO is through induced seismology. There are two approaches to producing seismic waves: small explosive charges and impactors. Experimental work has been performed in the laboratory to examine the impulse delivered by explosives. Wave travel times can be used to back out basic material properties and first order structure of an NEO. For example, if distinct arrival pulses for P and S waves are recorded and the explosive initiation/impact time and location are known, then it is possible to determine the elastic properties of bulk and shear modulus. Reflections in the seismograms allow a determination of material boundaries in an NEO. Original arrival time is important since Q numbers for stony NEO material are presumed to be high, as they were on the Moon, and thus it is expected that there will be extensive ringing and noise. Other types of NEO materials will have differing seismic characteristics. Title: Nucleosynthesis and future stellar abundance determinations Authors: Gustafsson, B. Bibcode: 2004EAS....11...21G Altcode: The most remarkable future possibilities of stellar spectroscopy and abundance analysis are discussed, and their consequences for the further understanding of stellar nucleosynthesis are commented on. It is argued that it will soon be possible to put the exploration of the origin of the chemical elements and the study of the chemical evolution of galaxies on a solid empirical ground, through systematic observations of yields from AGB stars and planetary nebulae, Wolf-Rayet stars and supernovae, and of well-determined abundance trends in different stellar populations. Title: Model Atmospheres and Stellar Abundance Analysis Authors: Gustafsson, Bengt Bibcode: 2004oee..symp..102G Altcode: 2004oee..symp..104G Model atmospheres have now been used in the analysis of stellar abundances for more than 50 years. During this period, remarkable progress has been made in the understanding of the physics of stellar atmospheres and in their modeling. The advances made in the observation of stellar spectra are even more remarkable. The question addressed here is whether comparable progress also can be found in the accuracy of the resulting abundances. It seems that this is not the case to the extent one might have expected, and the reasons for this are discussed. A number of recent developments in model atmosphere construction and in basic atomic and molecular data may, however, suggest that we are now approaching a situation with significantly diminished systematic errors in stellar abundances. Title: Resonant Structure in the Kuiper Disk: An Asymmetric Plutino Disk Authors: Holmes, Elizabeth K.; Dermott, Stanley F.; Gustafson, Bo Å. S.; Grogan, Keith Bibcode: 2003ApJ...597.1211H Altcode: In order to develop a dynamical model of the Kuiper disk, we run numerical integrations of particles originating from source bodies trapped in the 3:2 external mean motion resonance with Neptune to determine what percentage of particles remain in the resonance for a variety of particle and source body sizes. The dynamical evolution of the particles is followed from source to sink with Poynting-Robertson light drag, solar wind drag, radiation pressure, the Lorentz force, neutral interstellar gas drag, and the effects of planetary gravitational perturbations included. We find that the number of particles in the 3:2 resonance increases with decreasing β (i.e., increasing particle size) for the cases in which the initial source bodies are small (<=10 km in diameter) and that the percentage of particles in resonance is not significantly changed by either the addition of the Lorentz force, as long as the potential of the particles is small (~5 V), or the effect of neutral interstellar gas drag. The brightness of the entire Kuiper disk is calculated using a model composed of 500 μm diameter particles and fits well with upper limits to the Kuiper disk brightness and previous estimates. A disk with a size-frequency distribution weighted toward large particles, which are more likely to remain in resonance, may have a stronger, more easily identifiable resonant signature than a disk composed of small particles. Title: Development and testing of quartz crystal microbalances for missions to measure particle fluxes from minor solar system bodies Authors: Stephens, J.; Gustafson, B.; Waldemarsson, K. Bibcode: 2003EAEJA.....4478S Altcode: An instrument is being developed to measure the mass flux and size distribution of particles striking a spacecraft operating in the vicinity of airless minor solar system bodies including asteroids, small moons, and comets. We are developing and testing quartz crystal microbalances (QCMs) with robust particle capture coatings coupled with advanced oscillator electronics. The instrument is an extension the QCMs that are part of the Grain Impact Analyzer and Dust Accumulator (GIADA) instrument that will be carried aboard the European Space Agency (ESA) Rosetta Spacecraft. Particle capture coatings are required that will survive the interplanetary environment for long periods. The coatings should provide effective particle capture and coupling to a QCM to allow mass measurements during rendezvous encounters. We are using thin aerogel layers for particle capture since aerogel consists of a very low density (99% void volume) web of rigidly connected, sub-micron silica fibers. Sophisticated oscillator circuits are required to oscillate a QCM with a thick particle capture coating. Previously we reported on measurements of the electro-mechanical properties of thick (100 micrometer) layers of aerogel bonded to QCMs. In this work we report the results of firing small (100-500 micrometer) grains at aerogel-coated QCMs using a light gas gun at the University of Florida. The efficiency of particle capture by the aerogel layer as a function of particle size, velocity, and material composition was measured. The results will help guide the design of a second generation of aerosol capture coatings for QCMs. Title: ISO-SWS calibration and the accurate modelling of cool-star atmospheres. III. A0 to G2 stars Authors: Decin, L.; Vandenbussche, B.; Waelkens, K.; Eriksson, C.; Gustafsson, B.; Plez, B.; Sauval, A. J. Bibcode: 2003A&A...400..695D Altcode: 2002astro.ph..7636D Vega, Sirius, beta Leo, alpha Car and alpha Cen A belong to a sample of twenty stellar sources used for the calibration of the detectors of the Short-Wavelength Spectrometer on board the Infrared Space Observatory (ISO-SWS). While general problems with the calibration and with the theoretical modelling of these stars are reported in {Decin} et al. (\cite{Decin2000b}), each of these stars is discussed individually in this paper. As demonstrated in {Decin} et al. (\cite{Decin2000b}), it is not possible to deduce the effective temperature, the gravity and the chemical composition from the ISO-SWS spectra of these stars. But since ISO-SWS is absolutely calibrated, the angular diameter (thetad ) of these stellar sources can be deduced from their ISO-SWS spectra, which consequently yields the stellar radius (R), the gravity-inferred mass (Mg) and the luminosity (L) for these stars. For Vega, we obtained thetad = 3.35 +/- 0.20 mas, R = 2.79 +/- 0.17 Rsun, Mg = 2.54 +/- 1.21 Msun and L = 61 +/- 9 Lsun; for Sirius thetad = 6.17 +/- 0.38 mas, R = 1.75 +/- 0.11 Rsun, Mg = 2.22 +/- 1.06 Msun and L = 29 +/- 6 Lsun; for beta Leo thetad = 1.47 +/- 0.09 mas, R = 1.75 +/- 0.11 Rsun, Mg = 1.78 +/- 0.46 Msun and L = 15 +/- 2 Lsun; for alpha Car thetad = 7.22 +/- 0.42 mas, R = 74.39 +/- 5.76 Rsun, Mg = 12.80+24.95-6.35 Msun and L = 14573 +/- 2268 Lsun and for alpha Cen A thetad = 8.80 +/- 0.51 mas, R = 1.27 +/- 0.08 Rsun, Mg = 1.35 +/- 0.22 Msun and L = 1.7 +/- 0.2 Lsun. These deduced parameters are confronted with other published values and the goodness-of-fit between observed ISO-SWS data and the corresponding synthetic spectrum is discussed.

Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.}\fnmsep\thanks{Appendices A and B are only available in electronic form at http://www.edpsciences.org} Title: ISO-SWS calibration and the accurate modelling of cool-star atmospheres. IV. G9 to M2 stars Authors: Decin, L.; Vandenbussche, B.; Waelkens, C.; Decin, G.; Eriksson, K.; Gustafsson, B.; Plez, B.; Sauval, A. J. Bibcode: 2003A&A...400..709D Altcode: 2002astro.ph..7653D A detailed spectroscopic study of 11 giants with spectral type from G9 to M2 is presented. The 2.38-4.08 mu m wavelength-range of band 1 of ISO-SWS (Short-Wavelength Spectrometers on board of the Infrared Space Observatory) in which many different molecules - with their own dependence on each of the stellar parameters - are absorbing, enables us to estimate the effective temperature, the gravity, the microturbulence, the metallicity, the CNO-abundances, the 12C/13C-ratio and the angular diameter from the ISO-SWS data. Using the Hipparcos' parallax, the radius, luminosity and gravity-inferred mass are derived. The stellar parameters obtained are in good agreement with other published values, though also some discrepancies with values deduced by other authors are noted. For a few stars (delta Dra, xi Dra, alpha Tuc, H Sco and alpha Cet) some parameters - e.g. the CNO-abundances - are derived for the first time. By examining the correspondence between different ISO-SWS observations of the same object and between the ISO-SWS data and the corresponding synthetic spectrum, it is shown that the relative accuracy of ISO-SWS in band 1 (2.38-4.08 mu m) is better than 2% for these high-flux sources. The high level of correspondence between observations and theoretical predictions, together with a confrontation of the estimated Teff (ISO) value with Teff values derived from colours - which demonstrates the consistency between V-K, BCK, Teff and thetad derived from optical or IR data - proves that both the used MARCS models to derive the stellar quantities and the flux calibration of the ISO-SWS detectors have reached a high level of reliability.

Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.

Appendices A-D are only available in electronic form at http://www.edpsciences.org Title: ISO-SWS calibration and the accurate modelling of cool-star atmospheres. II. General results Authors: Decin, L.; Vandenbussche, B.; Waelkens, C.; Eriksson, K.; Gustafsson, B.; Plez, B.; Sauval, A. J.; Hinkle, K. Bibcode: 2003A&A...400..679D Altcode: 2002astro.ph..7621D The fine calibration of the ISO-SWS detectors (Infrared Space Observatory - Short Wavelength Spectrometer) has proven to be a delicate problem. We therefore present a detailed spectroscopic study in the 2.38-12 mu m wavelength range of a sample of 16 A0-M2 stars used for the calibration of ISO-SWS. By investigating the discrepancies between the ISO-SWS data of these sources, the theoretical predictions of their spectra, the high-resolution FTS-KP (Kitt Peak) spectrum of alpha Boo and the solar FTS-ATMOS (Atmospheric Trace Molecule Spectroscopy) spectrum, both calibration problems and problems in computing the theoretical models and the synthetic spectra are revealed. The underlying reasons for these problems are sought for and the impact on the further calibration of ISO-SWS and on the theoretical modelling is discussed extensively.

Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries France, Germany, The Netherlands and the UK) and with the participation of ISAS and NASA.

Appendix is only available in electronic form at http://www.edpsciences.org Title: Imaging polarimetry of stellar light scattered in detached shells around the carbon stars R Scl and U Ant Authors: González Delgado, D.; Olofsson, H.; Schwarz, H. E.; Eriksson, K.; Gustafsson, B.; Gledhill, T. Bibcode: 2003A&A...399.1021G Altcode: Imaging polarimetry has been used to study the extended, detached circumstellar shells around the bright carbon stars R Scl and U Ant. The observations were done in two narrow band filters centred on the resonance lines of neutral K and Na, but much broader than the expected line widths. The polarimetric data reveal brightness distributions, in both cases, which are in perfect agreement with previous observations of scattered light obtained through direct imaging techniques. The total intensity images towards R Scl outline, in both filters, circular disk-like distributions out to a radius of ~21arcsec , where the intensity drops sharply. The polarised intensity images reveal, however, that the scattering occurs in a geometrically thin shell. The degree of polarisation reaches values of ~35% in both filters. The imaging polarimetry observations of U Ant reveal a somewhat more complex structure, where the existence of several shells can be discerned. The polarised scattered light comes from a component, at a radius of ~50arcsec from the star, which lies outside the region where the bulk of the light is scattered. The latter comes from a dominating shell at ~43arcsec , which coincides spatially with the detached gas shell inferred from CO radio line data, and there may be another two shells inside this. The polarisation degree reaches ~50% in the outer component. We model, with a code based on the Monte Carlo method, the scattered emission under the assumption of dust scattering, using the observed polarised brightness distributions as constraints. In the case of R Scl we found that the polarised, as well as the total, light distributions can be explained by scattering in a 2arcsec wide shell of radius 20arcsec containing a dust mass of ~2*E-6 Msun. This dust shell is also responsible for the thermal dust emission measured by IRAS. There is room, up to 30% of the total scattered flux, for other scattering agents. Comparison with CO radio line data shows that this dust shell probably lies outside the detached CO gas shell. In the case of U Ant the modelling explains the outer component in terms of a 5arcsec wide shell at a radius of about 52arcsec with a dust mass of ~4*E-6 Msun. This is also the dust shell responsible for the emission measured by IRAS. However, the bulk of the scattered light cannot in this case be due to scattering by dust. In accordance with a discussion in a previous paper we attribute the remaining, unpolarised, scattering to the KI and Na D resonance lines. In both cases we found evidence that a dust shell has separated from the rest of the circumstellar medium. This may be due to gas-grain drift, or to hydrodynamical effects, which may also explain the complex multiple-shell structure seen towards U Ant. The model results are very dependent on the grain size distribution, and the observational data can only be reconciled with a very steep decline in grain size.

Based on observations using the 3.6 m telescope of the European Southern Observatory, La Silla, Chile. Title: Carbon Stars in the Local Group -- Detailed Abundance Analysis of Carbon Stars in the LMC Authors: Lambert, David L.; Eriksson, Kjell; Gustafsson, Bengt; Hinkle, Kenneth H.; Ryde, Nils; Wahlin, Rurik; Westerlund, Bengt Bibcode: 2003noao.prop..265L Altcode: Using the Phoenix on Gemini we propose to observe a sample of carbon stars in the LMC in four different wavelength regions at high spectral resolution and with high S/N. The spectra will provide CO, CN, and C_2 and atomic lines from which elemental and isotopic C, N, and O abundances and metal abundances will be derived by an approach similar to that previously used for Galactic field carbon stars (Lambert et al. 1986). We will then be able to calibrate lower resolution spectra of carbon stars in other Local Group galaxies. The observational study of carbon stars is a key to understanding late evolutionary stages and nucleosynthesis of low mass stars. Title: Integrated Study of the Physical Characteristics of Primitive Solar System Bodies Authors: Kolokolova, L.; Gustafson, B. A. S.; Lara, L. M.; Licandro, J.; Tozzi, G. P. Bibcode: 2003RMxAC..16...94K Altcode: Primitive bodies (comets, Centaurs, trans-Neptunian objects, etc.) are the best-preserved remnants of the Solar Nebula. Their composition and structure harbor clues to the origin of solar and exosolar planets and the evolution of protoplanetary disks. The capabilities of the Gran Telescopio Canarias (GTC) and its instrumentation provide us a unique opportunity to accomplish an integrated study of the physical properties of these remote small bodies. Title: A Grid of Model Atmospheres for Cool Stars Authors: Gustafsson, B.; Edvardsson, B.; Eriksson, K.; Mizuno-Wiedner, M.; Jørgensen, U. G.; Plez, B. Bibcode: 2003ASPC..288..331G Altcode: 2003sam..conf..331G An extensive grid of spherically symmetric model atmospheres of stars with

1. 2500 K ≤ Teff ≤ 8000 K, 2. -1.0 ≤ log g (= log GM/R2) ≤ 5.0 (cgs units), 3. different combinations of M and R, 4. -5 ≤ [A/H] ≤ 1, and 5. a number of CNO abundance combinations

is being constructed with an updated version of the MARCS program.

Special efforts are made to reach accuracy and completeness in opacity data. Opacity sampling is used with 10,000 and (for a minority of models) 90,000 wavelength points. Synthetic spectra are also provided.

We shall show how these classical models may be used to illustrate important physical properties of cool star atmospheres. Title: The Current Status in the Modelling of Stellar Atmospheres Authors: Gustafsson, B. Bibcode: 2003IAUS..210....3G Altcode: No abstract at ADS Title: A New MARCS Grid Authors: Gustafsson, B.; Edvardsson, B.; Eriksson, K.; Jørgensen, U. G.; Mizuno-Wiedner, M.; Plez, B. Bibcode: 2003IAUS..210P..A4G Altcode: No abstract at ADS Title: The virtue of looking in another direction Authors: Gustafsson, Bengt Bibcode: 2003UppOR..59....1G Altcode: No abstract at ADS Title: Atmospheres of AGB Stars Authors: Gustafsson, Bengt; Höfner, Susanne Bibcode: 2003agbs.conf..149G Altcode: No abstract at ADS Title: A MARCS Grid of S-Type Star Atmospheres Authors: Plez, B.; van Eck, S.; Jorissen, A.; Edvardsson, B.; Eriksson, K.; Gustafsson, B. Bibcode: 2003IAUS..210P..A2P Altcode: No abstract at ADS Title: Dynamical evolution of dust particles in the Kuiper disk Authors: Holmes, Elizabeth K.; Dermott, Stanley F.; Gustafson, Bo A. S. Bibcode: 2002ESASP.500...43H Altcode: 2002acm..conf...43H A Kuiper belt disk will have a resonant structure, arising because a subset of Kuiper belt objects, the Plutinos, are in the 3:2 mean motion resonance with Neptune. We run numerical integrations of particles originating from Plutinos to determine what percentage of particles remain in the resonance for a variety of particle and source body sizes. The dynamical evolution of the particles is followed from source to sink with Poynting-Robertson light drag, solar wind drag, radiation pressure, the Lorentz force, neutral interstellar gas drag, and the effects of planetary gravitational perturbations included. The percentage of particles in the 3:2 resonance increases with decreasing β for the cases where the source bodies are small (≤10 km), and is not significantly changed by either the addition of neutral interstellar gas drag or the Lorentz force, as long as the potential of the particles is small (U≍5 V). Title: A stellar relic from the early Milky Way Authors: Christlieb, N.; Bessell, M. S.; Beers, T. C.; Gustafsson, B.; Korn, A.; Barklem, P. S.; Karlsson, T.; Mizuno-Wiedner, M.; Rossi, S. Bibcode: 2002Natur.419..904C Altcode: 2002astro.ph.11274C The chemical composition of the most metal-deficient stars largely reflects the composition of the gas from which they formed. These old stars provide crucial clues to the star formation history and the synthesis of chemical elements in the early Universe. They are the local relics of epochs otherwise observable only at very high redshifts; if totally metal-free (`population III') stars could be found, this would allow the direct study of the pristine gas from the Big Bang. Earlier searches for such stars found none with an iron abundance less than 1/10,000 that of the Sun, leading to the suggestion that low-mass stars could form from clouds above a critical iron abundance. Here we report the discovery of a low-mass star with an iron abundance as low as 1/200,000 of the solar value. This discovery suggests that population III stars could still exist-that is, that the first generation of stars also contained long-lived low-mass objects. The previous failure to find them may be an observational selection effect. Title: Electromagnetic and Light Scattering by Nonspherical Particle Authors: Gustafson, Bo Åke Sture; Kolokolova, Ludmilla; Videen, Gorden Bibcode: 2002elsn.conf.....G Altcode: No abstract at ADS Title: Dust in Interplanetary Space Authors: Gustafson, B. Å. S. Bibcode: 2002AAS...200.6602G Altcode: 2002BAAS...34Q.754G I will critically review the main results on dust in interplanetary space and its diversity based on deep space probing. The dust impact rate on the Ulysses and Galileo dust detectors can be discerned as depending on the changing viewing geometry of the detector as the spacecraft spins and moves along its orbit. This reveals the existence of dynamically separate populations, evidence for these will be presented and interpretations in terms of the progenitors will be discussed. The decreasing flux with increasing size or mass in combination with typical detector areas of the order of one square meter means that the smallest grains in the micron and submicron range are sampled while statistically very little or no information is obtained on larger grains. The next step will be the study of larger grains and their retrieval for analysis in the laboratory. I will address plans for a large cosmic dust collector in Earth orbit to bring back grains of tens of microns to Earth for laboratory studies. Title: Erratum: Chemical abundance patterns - fingerprints of nucleosynthesis in the first stars Authors: Karlsson, T.; Gustafsson, B. Bibcode: 2002A&A...386..884K Altcode: Figures 17 and 18 on page 478 were misprinted. The metallicity of the stars, measured by [Fe/H], was wrongly indicated and one star was missing. The corrected figures are shown below. No conclusions are altered. Title: Planetary aerosol monitor/interplanetary dust analyser Authors: Gustafson, B. Å. S.; Giovane, F.; Waldemarsson, T.; Kolokolova, L.; Xu, Yu. -I.; McKisson, J. Bibcode: 2002dsso.conf..195G Altcode: 2002IAUCo.181..195G No abstract at ADS Title: Light scattering by flakes Authors: Waldemarsson, K. W. T.; Gustafson, B. Å. S. Bibcode: 2002dsso.conf..320W Altcode: 2002IAUCo.181..320W No abstract at ADS Title: Evolution of cometary grains from studies of comet images Authors: Kolokolova, L.; Gustafson, B. Å. S.; Jockers, K.; Lichtenberg, G. Bibcode: 2002dsso.conf..269K Altcode: 2002IAUCo.181..269K No abstract at ADS Title: Chemical abundance patterns - fingerprints of nucleosynthesis in the first stars Authors: Karlsson, T.; Gustafsson, B. Bibcode: 2001A&A...379..461K Altcode: 2001astro.ph..9010K The interstellar medium of low-metallicity systems undergoing star formation will show chemical abundance inhomogeneities due to supernova events enriching the medium on a local scale. If the star formation time-scale is shorter than the time-scale of mixing of the interstellar matter, the inhomogeneities are reflected in the surface abundances of low-mass stars and thereby detailed information on the nucleosynthesis in the first generations of supernovae is preserved. Characteristic patterns and substructures are therefore expected to be found, apart from the large scatter behaviour, in the distributions of stars when displayed in diagrams relating different element abundance ratios. These patterns emerge from specific variations with progenitor stellar mass of the supernova yields and it is demonstrated that the patterns are insensitive to the initial mass function (IMF) even though the relative density of stars within the patterns may vary. An analytical theory of the formation of patterns is presented and it is shown that from a statistical point of view the abundance ratios can trace the different nucleosynthesis sites even when mixing of the interstellar medium occurs. Using these results, it should be possible to empirically determine supernova yields from the information on relative abundance ratios of a large, homogeneous sample of extremely metal-poor Galactic halo stars. Title: One year of Galileo dust data from the Jovian system: 1996 Authors: Krüger, H.; Grün, E.; Graps, A.; Bindschadler, D.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 2001P&SS...49.1285K Altcode: 2001astro.ph..7052K The dust detector system onboard Galileo has recoding dust impacts in circumjovian space since the spacecraft was injected into a bound orbit about Jupiter in December 1995. This is the sixth in a series of papers dedicated to presenting Galileo and Ulysses dust data. We present data from the Galileo dust instrument for the period January to December 1996 when the spacecraft completed four orbits about Jupiter (G1, G2, C3 and E4). Data were obtained as high-resolution realtime science data or recorded data during a time period of 100 days, or via memory read-outs during the remaining times. Because the data transmission rate of the spacecraft is very low, the complete data set (i.e. all parameters measured by the instrument during impact of a dust particle) for only 2% (5353) of all particles detected could be transmitted to Earth; the other particles were only counted. Together with the data for 2883 particles detected during Galileo's interplanetary cruise and published earlier, complete data of 8236 particles detected by the Galileo dust instrument from 1989 to 1996 are now available. The majority of particles detected are tiny grains (about 10 nm in radius) originating from Jupiter's innermost Galilean moon Io. These grains have been detected throughout the Jovian system and the highest impact rates exceeded 100 min-1. A small number of grains has been detected in the close vicinity of the Galilean moons Europa, Ganymede and Callisto which belong to impact-generated dust clouds formed by (mostly submicrometer sized) ejecta from the surfaces of the moons (Krüger et al., 1999e. Nature 399, 558). Impacts of submicrometer to micrometer sized grains have been detected throughout the Jovian system and especially in the region between the Galilean moons. Title: Systematic Study of the Light Scattering by Aggregates Using Microwave Analog Experiments and Multifactor Analysis Authors: Kolokolova, L.; Gustafson, B. A. S. Bibcode: 2001DPS....33.6202K Altcode: 2001BAAS...33.1154K The unique microwave-analog-to-light-scattering facility at the University of Florida was used to survey light scattering characteristics of aggregated particles. Microwave analog experiments are the fastest and most flexible means to simulate light scattering by complex cosmic dust particles. This remains true although powerful computer codes to calculate light scattering by irregular and inhomogeneous particles have been developed in recent years. Aggregates of a variety of physical characteristics (number and size of constituent particles, packing factor) were built and the scattering was measured at a variety of orientations (to simulate random orientation) and across a range of wavelengths (to study spectral properties). To satisfy the requirements of the statistical multi-factor analysis, known as 2k factorial design, each of three characteristics of an aggregate (number and size of particles, aggregate packing factor) could take two fixed values. In each new experiment only one characteristic differed from those in the previous experiment. Thus, eight (23) aggregates of all possible combinations of two values of three parameters were studied. The values of the characteristics were: 1000 and 5000 for the number of particles in the aggregates; the particle size corresponded to 0.25 and 0.5 micron; the packing factor (the ratio of the total volume of the particles to the volume of the aggregate) was 10 and 50%. The angular and spectral dependencies of intensity and polarization were obtained for these aggregates. The subjects of the statistical analysis were color, polarization and polarimetric color around the scattering angle 90 degree. The statistical analysis showed that the intensity and polarization are mostly affected by the size of the constituent particles. The size also determines the shape of the angular and spectral dependencies and, consequently, the color and polarimetric color. The packing factor and number of the particles have less influence on the light-scattering characteristics within the range studied. NASA supported this work through grants NAG5-8944 and NAG5-6378. Title: The ``Planetary Aerosol Monitor/ Interplanetary Dust Analyzer" Instrument for Comet or Planet Missions. Authors: Gustafson, B. Å. S.; Giovane, F.; Kolokolova, L.; Waldemarsson, K. W. T.; Xu, Y. -l.; McKisson, J. Bibcode: 2001DPS....33.5714G Altcode: 2001BAAS...33.1146G The Laboratory for Astrophysics at the University of Florida has developed a dust analyzer capable of measuring key particle physical parameters without causing damage to the dust grains. A laser illuminates particles passing through an optical system that measures intensity and polarization of the scattered light at specific scattering angles. The choice of scattering angles, a sophisticated light collecting assembly and analysis algorithms allow classification of the dust particles according to size, shape (equidimensional, elongated, smooth or angular), composition (dielectric, absorbing, or metallic) and internal structure (compact or porous). The instrument's capabilities are illustrated using theoretical simulations, microwave analogue measurements and tests data obtained using a laboratory version of the PAM/IDA. We gratefully acknowledge NASA support through the Planetary Instrument Definition & Development Program, Grant NAG5-4547. Title: Application of Microwave Analog Measurements to the Modeling of Titan's Aerosols Authors: Thomas-Osip, J. E.; Gustafson, B. Å. S.; Kolokolova, L.; Xu, Y. -l. Bibcode: 2001DPS....33.3804T Altcode: 2001BAAS...33.1109T A combination of laboratory experiments, theoretical modeling, and spacecraft in situ observations is employed to characterize the aerosols in the atmosphere of Titan. The scattering properties of model aerosols were measured using the Microwave Analog Light Scattering Facility at the University of Florida and complemented with theoretical modeling of radiative transfer in Titan's atmosphere. This study compares these modeling results with photopolarimetric observations made over a range of phase angles by the Pioneer 11 and Voyagers 1 and 2 spacecraft. Important results of this work include a survey of the scattering properties of different particle morphologies and compositions necessary to accurately interpret these observations without introducing non-physical assumptions about the particles or requiring additional free parameters to the radiative transfer models. Previous studies use calculation methods which, due to computing memory and processing time requirements, a priori exclude many particle shapes and sizes that the microwave analog laboratory is ideal for exploring. The goal of the present work, to directly constrain aerosol physical characteristics, is addressed by studying in a consistent manner how a variety of aerosol characteristics affect the polarization and intensity reflected by Titan's atmosphere. Model results for many particle morphologies do not match the in situ spacecraft observations. The most plausible physical particle models suggest that a combination of Rayleigh-like single particles and aggregates that are larger than those previously suggested and investigated (Rannou et al. 1997, JGR, 102, 10997; West & Smith 1991, Icarus, 90, 330) provide the best fit to the existing data. Additional laboratory experiments and more refined modeling awaits the results of a new rich observational dataset following the Cassini/Huygens encounter with Titan in 2004. This work was partially funded by the NASA GSRP. Title: Four years of Ulysses dust data: 1996-1999 Authors: Krüger, H.; Grün, E.; Landgraf, M.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 2001P&SS...49.1303K Altcode: 2001astro.ph..6322K The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse ( i=79°, perihelion distance 1.3 AU, aphelion distance 5.4 AU). Between January 1996 and December 1999 the spacecraft was beyond 3 AU from the Sun and crossed the ecliptic plane at aphelion in May 1998. In this 4-yr period 218 dust impacts were recorded with the dust detector on board. We publish and analyse the complete data set of both raw and reduced data for particles with masses 10 -16- 10 -8 g. Together with 1477 dust impacts recorded between launch of Ulysses and the end of 1995 published earlier (Grün et al., Planet. Space Sci. 43 (1995a) 971; Krüger et al., Planet. Space Sci. 47 (1999b) 363), a data set of 1695 dust impacts detected with the Ulysses sensor between October 1990 and December 1999 is now available. The impact rate measured between 1996 and 1999 was relatively constant with about 0.2 impacts per day. The impact direction of the majority of the impacts is compatible with particles of interstellar origin, the rest are most likely interplanetary particles. The observed impact rate is compared with a model for the flux of interstellar dust particles. The flux of particles several micrometres in size is compared with the measurements of the dust instruments on board Pioneer 10 and Pioneer 11 beyond 3 AU (Humes, J. Geophys. Res. 85 (1980) 5841). Between 3 and 5 AU, Pioneer results predict that Ulysses should have seen 5 times more ( ∼10 μm sized) particles than actually detected. Title: Imaging of detached shells around the carbon stars R Scl and U Ant through scattered stellar light Authors: González Delgado, D.; Olofsson, H.; Schwarz, H. E.; Eriksson, K.; Gustafsson, B. Bibcode: 2001A&A...372..885G Altcode: 2001astro.ph..4140G; 2001astro.ph..4140D We present the first optical images of scattered light from large, detached gas/dust shells around two carbon stars, R Scl and U Ant, obtained in narrow band filters centred on the resonance lines of neutral K and Na, and in a Ström}gren b filter (only U Ant). They confirm results obtained in CO radio line observations, but also reveal new and interesting structures. Towards R Scl the scattering appears optically thick in both the K and Na filters, and both images outline almost perfectly circular disks with essentially uniform intensity out to a sharp outer radius of ~21arcsec . These disks are larger - by about a factor of two - than the radius of the detached shell which has been marginally resolved in CO radio line data. In U Ant the scattering in the K filter appears to be, at least partially, optically thin, and the image is consistent with scattering in a geometrically thin (~3arcsec ) shell (radius ~43arcsec ) with an overall spherical symmetry. The size of this shell agrees very well with that of the detached shell seen in CO radio line emission. The scattering in the Na filter appears more optically thick, and the image suggests the presence of at least one, possibly two, shells inside the 43arcsec shell. There is no evidence for such a multiple-shell structure in the CO data, but this can be due to considerably lower masses for these inner shells. Weak scattering appears also in a shell which is located outside the 43arcsec shell. The present data do not allow us to conclusively identify the scattering agent, but we argue that most of the emission in the K and Na filter images is to due to resonance line scattering, and that there is also a weaker contribution from dust scattering in the U Ant data. Awaiting new observational data, our interpretation must be regarded as tentative. Based on observations using the 3.6 m telescope of the European Southern Observatory, La Silla, Chile. Title: Color and polarization as indicators of comet dust properties and evolution in the near-nucleus coma Authors: Kolokolova, Ludmilla; Jockers, Klaus; Gustafson, Bo Å. S.; Lichtenberg, Günther Bibcode: 2001JGR...10610113K Altcode: We present CCD colorimetric and polarimetric observations of comets Hale-Bopp, Hyakutake, and Tabur and an analysis of their change in color and polarization with the distance from the nucleus that may indicate dust evolution in the coma. We concentrate on trends along the solar-antisolar direction in the innermost coma, where all three observed comets demonstrate a correlation between color and polarization. Comparisons to laboratory studies of scattering by complex dust structures reveal that the observed correlation is most likely a result of evaporation/destruction of a dark (organic) material. We study the evolution and properties of the dust in the central coma of these comets using a tentative model of cometary dust as an ensemble of core-mantle particles with sublimating mantles. Calculations for a variety of optical properties, core-mantle mass ratios, and dust size distributions showed that this model could describe the observed change in color and polarization in cometary comae when realistic ranges of input parameters are used. The best fit particles have silicate cores of radius 0.05-0.2μm with a porous organic-carbon mantle of mantle/core mass ratio 0.5-1. Within the frames of the model the peculiarity of the color and polarization for comet Hale-Bopp (both increase with the distance from the nucleus unlike the decrease observed in comets Hyakutake and Tabur) can be understood in terms of a compact organic mantle on the Hale-Bopp dust grains, whereas the Hyakutake and Tabur dust have more porous mantles. We show how polarimetric color restricts the range of satisfactory refractive indices of both the core and the mantle materials. Title: New Searches for R-Process Enhanced Stars Authors: Christlieb, N.; Beers, T. C.; Hill, V.; Primas, F.; Rhee, J.; Ryan, S. G.; Bessell, M.; Norris, J. E.; Sneden, C.; Edvardsson, B.; Gustafsson, B.; Karlsson, T.; Mizuno-Wiedner, M. Bibcode: 2001ASPC..245..298C Altcode: 2001aats.conf..298C No abstract at ADS Title: Interactions with Electromagnetic Radiation: Theory and Laboratory Simulations Authors: Gustafson, Bo A. S.; Greenberg, J. Mayo; Kolokolova, Ludmilla; Xu, Yu-lin; Stognienko, Ralf Bibcode: 2001indu.book..509G Altcode: No abstract at ADS Title: Interplanetary Dust Authors: Grün, E.; Gustafson, B. A. S.; Dermott, S.; Fechtig, H. Bibcode: 2001indu.book.....G Altcode: 2001ipd..book.....G This is a handbook on the physics of interplanetary dust, a topic of interest not only to astronomers and space scientists but also to engineers. The following topics are covered in the book: historical perspectives; cometary dust; near-Earth environment; meteoroids and meteors; properties of interplanetary dust, information from collected samples; in situ measurements of cosmic dust; numerical modeling of the Zodiacal Cloud structure; synthesis of observations; instrumentation; physical processes; optical properties of interplanetary dust; orbital evolution of interplanetary dust; circumplanetary dust, observations and simple physics; interstellar dust and circumstellar dust disks. Title: Images in Scattered Light of Two Carbon Stars (CD-ROM Directory: contribs/gonzalez) Authors: González Delgado, D.; Olofsson, H.; Schwarz, H.; Eriksson, K.; Gustafsson, B. Bibcode: 2001ASPC..223.1219G Altcode: 2001csss...11.1219G No abstract at ADS Title: How Good Are New Ages for Old Stars? Authors: Gustafsson, Bengt; Mizuno-Wiedner, Michelle Bibcode: 2001ASPC..245..271G Altcode: 2001aats.conf..271G No abstract at ADS Title: Are there Dust-Flakes in Cometary Atmospheres? Authors: Waldemarsson, K. W. T.; Kolokolova, L.; Gustafson, B. A. S. Bibcode: 2000AAS...197.5001W Altcode: 2000BAAS...32.1486W Recent comet observations show that the inner comae (within 5000 km from the nucleus) has unusual light scattering features. Particularly, the color, polarization, and polarimetric color are much different than in the surrounding cometary atmosphere and cannot be explained by the light scattering from simple spherical particles. More complex particle geometries have been proposed. Stephens and Gustafson (1991, Icarus 94, 209) showed through a laboratory study that thin flakes can form on surfaces of sublimating dust/ice mixtures. Microwave analog to light scattering measurements has shown that such flakes can produce unusual combinations of color, polarization and polarimetric color and may be inner coma particle candidates. This paper presents the results of our theoretical modeling of the light scattering by flake-like dust particles. The modeling is based on our approximate light scattering solution for a thin plate with arbitrary refractive index. When the scattering model is compared to microwave test measurements an overall good agreement is found. We investigate the dependence of the polarization, color, and polarimetric color on the refractive index and geometrical dimensions of the flakes. We show how the light scattering by flakes can explain observational features of inner comae. Title: ISO-SWS calibration and the accurate modelling of cool-star atmospheres. I. Method Authors: Decin, L.; Waelkens, C.; Eriksson, K.; Gustafsson, B.; Plez, B.; Sauval, A. J.; Van Assche, W.; Vandenbussche, B. Bibcode: 2000A&A...364..137D Altcode: 2000astro.ph..8316D A detailed spectroscopic study of the ISO-SWS data of the red giant alpha Tau is presented, which enables not only the accurate determination of the stellar parameters of alpha Tau, but also serves as a critical review of the ISO-SWS calibration. This study is situated in a broader context of an iterative process in which both accurate observations of stellar templates and cool star atmosphere models are involved to improve the ISO-SWS calibration process as well as the theoretical modelling of stellar atmospheres. Therefore a sample of cool stars, covering the whole A0 - M8 spectral classification, has been observed in order to disentangle calibration problems and problems in generating the theoretical models and corresponding synthetic spectrum. By using stellar parameters found in the literature large discrepancies were seen between the ISO-SWS data and the generated synthetic spectrum of alpha Tau. A study of the influence of various stellar parameters on the theoretical models and synthetic spectra, in conjunction with the Kolmogorov-Smirnov test to evaluate objectively the goodness-of-fit, enables us to pin down the stellar parameters with a high accuracy: Teff = 3850 +/- 70 K, log g = 1.50 +/- 0.15, M = 2.3 +/- 0.8 Msun, z = -0.15 +/- 0.20 dex, xit = 1.7 +/- 0.3 km s-1, 12C/13C = 10 +/- 1, varepsilon (C) = 8.35 +/- 0.20 dex, varepsilon (N) = 8.35 +/- 0.25 dex, varepsilon (O) = 8.83 +/- 0.15 dex and thetad = 20.77 +/- 0.83 mas. These atmospheric parameters were then compared with the results provided by other authors using other methods and/or spectra. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. Title: Mira's Wind Explored in Scattering Infrared CO Lines Authors: Ryde, N.; Gustafsson, B.; Eriksson, K.; Hinkle, K. H. Bibcode: 2000ApJ...545..945R Altcode: 2000astro.ph..8235R We have observed the intermediate regions of the circumstellar envelope of Mira (ο Ceti) in photospheric light scattered by three vibration-rotation transitions of the fundamental band of CO, from low-excited rotational levels of the ground vibrational state, at an angular distance of β~2''-7" away from the star. The data were obtained with the Phoenix spectrometer mounted on the 4 m Mayall telescope at Kitt Peak. The spatial resolution is approximately 0.5" and seeing limited. Our observations provide absolute fluxes, leading to an independent new estimate of the mass-loss rate of approximately 3×10-7 Msolar yr-1, as derived from a simple analytic wind model. We find that the scattered intensity from the wind of Mira for 2''<~β<~7'' decreases as β-3, which suggests a time constant mass-loss rate, when averaged over 100 yr, over the past 1200 yr. Title: The Effect of the Lorentz Force on the Resonant Structure of Dust Particles in the Kuiper Belt Authors: Holmes, E. K.; Dermott, S. F.; Gustafson, B. A. S. Bibcode: 2000AAS...197.5005H Altcode: 2000BAAS...32.1487H There is a possible connection between structure in circumstellar disks and the presence of planets, our own zodiacal cloud being a proven example. Asymmetries in such a disk could be diagnostic of planets which would be otherwise undetectable. At least three different types of asymmetries can serve to indicate bodies orbiting a star in a disk: (1) a warp in the plane of symmetry of the disk, (2) an offset in the center of symmetry of the disk with respect to the central star, and (3) density anomalies in the plane of the disk due to resonant trapping of dust particles. In the asteroid belt, collisions between asteroids supply dust particles to the zodiacal cloud. By comparison, it has been postulated that collisions between Kuiper Belt Objects (KBOs) could initiate a collisional cascade which would produce a Kuiper dust disk. A Kuiper Disk would most likely have a resonant structure, with two concentrations in brightness along the ecliptic longitude. This large scale structure arises because many of the KBOs, the Plutinos, are in the 2:3 mean motion resonance with Neptune. By running numerical integrations of particles in Pluto-like orbits, the resonant structure of the Kuiper belt can be studied by determining the percentage of particles trapped in the resonance as a function of their initial velocity and beta, where β = Frad}/F{grav. The dynamical evolution of the particles is followed from source to sink with Poynting Robertson light drag, solar wind drag, radiation pressure, the Lorentz force, neutral interstellar gas drag, and the effects of planetary gravitational perturbations included. The integrations are run with and without the Lorentz force to determine what effect the Lorentz force has on particles in the Kuiper Belt as a function of particle size. This research was funded in part by a NASA GSRP grant. Title: The Rare 1932 Dust Trail Encounter of November 17, 2000, As Observed from Aircraft Authors: Jenniskens, P.; Gustafson, B. A. S. Bibcode: 2000JIMO...28..209J Altcode: Both encounters with the 1932 and 1866 dust trails of Comet 55T/Temple-Tuttle on November 17 and 18, 2000, respectively, were observed with intensified cameras from a twin-engine Cessna-130 aircraft over southern Florida. Here, preliminary results are presented for the 1932 dust trail encounter, which was most difficult to observe from the ground. Results are consistent with models that predict strong Leonid returns in November 2001 and 2002. Title: ISO Impact on Stellar Models and Viceversa Authors: Decin, L.; Waelkens, C.; Eriksson, K.; Gustafsson, B.; Plez, B.; Sauval, A. J.; van Assche, W.; Vandenbussche, B. Bibcode: 2000ESASP.456..289D Altcode: 2000astro.ph..8362D; 2000ibp..conf..289D We present a detailed spectroscopic study of a sample of bright, mostly cool, stars observed with the Short-Wavelength Spectrometer (SWS) on board ISO, which enables the accurate determination of the stellar parameters of the cool giants, but also serves as a critical review of the ISO-SWS calibration. Title: Gasdynamics of Detached Shells Around Carbon Stars With Variable Mass Loss Authors: Myasnikov, A. V.; Belov, N. A.; Gustafsson, B.; Eriksson, K. Bibcode: 2000Ap&SS.274..231M Altcode: Gasdynamic features of detached shells around carbon stars with variable mass loss rate are investigated in detail numerically. It is shown that a shell is unstable and also, 2D perturbations are less developed that 3D ones. The structure of perturbed flows corresponding to different evolution scenarios is compared. The results obtained seem to be promising for interpretation of observations, in particular, the recently obtained detailed data of TT Cyg. Title: Applicability of effective medium theories to photometric and polarimetric observations of cosmic dust - A laboratory study using the microwave analog technique Authors: Kolokolova, L.; Gustafson, B. A. S.; Bourgeois, M. Bibcode: 2000DPS....32.5603K Altcode: 2000BAAS...32.1107K The interpretation of optical (photometric, polarimetric, colorimetric, etc.) observations of dust, whether cometary, interplanetary, circum-stellar, or planetary aerosols, is hampered by the complicated structure of the grains that, most likely, include multi-compositional, aggregated particles. It is a common practice to use effective medium theories (EMT) to estimate average, "effective" optical constants of such inhomogeneous materials. A variety of EMTs were developed for different structures of the medium (aggregated, fractal, separated inclusions) and for a variety of sizes and shapes of the inhomogeneities. However, the validity of EMT for astronomical applications has only been demonstrated for extinction cross-sections that were checked using the DDA method. This paper compares angular distribution and wavelength dependence of intensity and polarization of scattered light obtained from EMT calculations with the results of microwave analog measurements at the microwave facilities of the University of Florida. We simulated the light-scattering by organic grains with silicate inclusions of size parameter x=0.075 (0.04 micron), 0.58 (0.3 micron), and 1.2 (0.6 micron). The conclusion is that all EMTs (including Maxwell-Garnett, Bruggeman, Looyenga, Stroud and Pan) yield similar results and work better for the intensity of the scattered light than for its polarization. The dependency of the intensity on the scattering angle is in good agreement with the EMTs. However, calculations overestimate the magnitude of the intensity when the size of the inclusions and/or their volume fraction in the mixture increases. We find that the EMTs cannot reproduce the angular dependence of polarization and yield errors in polarization of around 45-65% for all sizes and volume fractions of the inclusions. The spectral gradient of polarization (polarimetric color) calculated using EMTs also differ from the experiments by the same order. By contrast, the calculated spectral gradient of intensity (color) is in good agreement with the experiments. This work was supported by NASA grants NAG5-8944 and NAG5-6378. Title: Growth and Form of Planetary Seedlings: Results from a Microgravity Aggregation Experiment Authors: Blum, J.; Wurm, G.; Kempf, S.; Poppe, T.; Klahr, H.; Kozasa, T.; Rott, M.; Henning, T.; Dorschner, J.; Schräpler, R.; Keller, H. U.; Markiewicz, W. J.; Mann, I.; Gustafson, B. A.; Giovane, F.; Neuhaus, D.; Fechtig, H.; Grün, E.; Feuerbacher, B.; Kochan, H.; Ratke, L.; El Goresy, A.; Morfill, G.; Weidenschilling, S. J.; Schwehm, G.; Metzler, K.; Ip, W. -H. Bibcode: 2000PhRvL..85.2426B Altcode: The outcome of the first stage of planetary formation, which is characterized by ballistic agglomeration of preplanetary dust grains due to Brownian motion in the free molecular flow regime of the solar nebula, is still somewhat speculative. We performed a microgravity experiment flown onboard the space shuttle in which we simulated, for the first time, the onset of free preplanetary dust accumulation and revealed the structures and growth rates of the first dust agglomerates in the young solar system. We find that a thermally aggregating swarm of dust particles evolves very rapidly and forms unexpected open-structured agglomerates. Title: The r-Process-enriched Low-Metallicity Giant HD 115444 Authors: Westin, Jenny; Sneden, Christopher; Gustafsson, Bengt; Cowan, John J. Bibcode: 2000ApJ...530..783W Altcode: 1999astro.ph.10376W New high-resolution, very high signal-to-noise spectra of ultra-metal-poor (UMP) giant stars HD 115444 and HD 122563 have been gathered with the High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7 m telescope. With these spectra, line identification and model atmosphere analyses have been conducted, emphasizing the neutron-capture elements. Twenty elements with Z>30 have been identified in the spectrum of HD 115444. This star is known to have overabundances of the neutron-capture elements, but it has lacked a detailed analysis necessary to compare with nucleosynthesis predictions. The new study features a line-by-line differential abundance comparison of HD 115444 with the bright, well-studied halo giant HD 122563. For HD 115444, the overall metallicity is [Fe/H]~=-3.0. The abundances of the light and iron-peak elements generally show the same pattern as other UMP stars (e.g., overdeficiencies of manganese and chromium, overabundances of cobalt), but the differential analysis indicates several nucleosynthesis signatures that are unique to each star. Synthetic spectrum analyses reveal substantial overabundances of the heavier neutron-capture elements (Z>=56 elements barium and beyond) in HD 115444. Thus with [Eu/Fe]~=+0.9, for example, HD 115444 is a moderate version of the extremely neutron-capture-rich UMP giant CS 22892-052 ([Fe/H]~=-3.1, [Eu/Fe]~=+1.7). The abundance pattern of the heavier neutron-capture elements is consistent with scaled solar system r-process-only abundances (with little contribution from the s-process). In HD 115444, [Ba/Eu]=-0.73, while in CS 22892-052 this ratio is -0.79. Thus HD 115444 becomes the second UMP r-process-rich halo giant unambiguously identified from a very detailed abundance analysis. Abundances of the lighter neutron-capture elements strontium, yttrium, and zirconium are, however, nearly identical in HD 115444 and HD 122563. Along with the heavier neutron-capture elements, the 4019 Å line of Th II has been detected in HD 115444, yielding log ɛ(Th) = -2.23+/-0.07. Comparing the observed thorium abundance in HD 115444, along with CS 22892-052, with other theoretical estimates of the time-zero abundance suggests an age for both of these UMP stars of 15.6+/-4 Gyr, consistent with previous radioactive age estimates for CS 22892-052 and other Galactic and cosmological age determinations. Title: CO Imaging of Late-Type Circumstellar Shells Authors: Gustafsson, Bengt; Eriksson, Kjell; Lambert, David L.; Olofsson, Hans; Ryde, Nils; Schoier, Fredrik L. Bibcode: 2000noao.prop..293G Altcode: Microwave emission lines and optical resonance lines have been used to image circumstellar shells on the sky. Now it is possible to image resonance scattering from infrared vibration-rotational carbon monoxide lines (see Ryde et al. A& A 347, L35, 1999). Infrared CO is formed closer to the star than microwave CO and provides complementary information. Infrared CO mapping is especially powerful because many CO lines of differing excitation are present, allowing the extraction of excitation temperature and abundance from the measured column densities. Previous on-star observations have led to the detection of multiple velocity components in the CO lines, formed in different parts of the circumstellar shell. We have found in an earlier observing run with this method that the shell of CO gas around Mira (4 arcsec-10 arcsec from the star) is spherically symmetric and homogeneous. But we also trace from the data a region close to the star devoid of gas or at least of CO (Ryde et al. ApJ, soon to be submitted). Each CO line can be used to image the circumstellar outflow at different stellar radii. Information on the velocity structure and the development of clumps in the flow will be extracted. The present proposal focuses on the study of shells around carbon stars for which we have complementary mm and optical data. We will furthermore for the first time map detached shells with this method. Title: Interferometric Molecular Line observations of RW LMi Authors: Lindqvist, Michael; Lucas, Robert; Olofsson, Hans; Larsen, Fredrick; Omont, Alain; Eriksson, Kjell; Gustafsson, Bengt Bibcode: 2000IAUS..177..557L Altcode: No abstract at ADS Title: Microwave Analog to Light-Scattering Measurements Authors: Gustafson, Bo Å. S. Bibcode: 2000lsnp.book..367G Altcode: No abstract at ADS Title: Tracing the first supernovae in halo dwarf stars Authors: Karlsson, T.; Gustafsson, B. Bibcode: 2000LIACo..35..237K Altcode: 2000ghgc.conf..237K No abstract at ADS Title: Commission 21: Light of the Night Sky: (Lumiere du Ciel Nocturne) Authors: Bowyer, S.; Lamy, P.; Dwek, E.; Gustafson, B.; Hanner, M.; Levasseur-Regourd, A. Ch.; Mikhail, J.; Mann, I.; Mukai, T.; Matsumoto, T. Bibcode: 2000IAUTA..24..152B Altcode: No abstract at ADS Title: Carbon Stars and Nucleosynthesis in Galaxies Authors: Gustafsson, Bengt; Ryde, Nils Bibcode: 2000IAUS..177..481G Altcode: No abstract at ADS Title: VizieR Online Data Catalog: Atmospheric parameters in metal-poor stars. II (Gratton+, 1999) Authors: Gratton, R. G.; Carretta, E.; Eriksson, K.; Gustafsson, B. Bibcode: 2000yCat..33500955G Altcode: We present non-LTE corrections to abundances of Fe, O, Na, and Mg derived from LTE analyses of F-K stars over a broad range of gravities and metal abundances; they were obtained using statistical equilibrium calculations and new model atoms. Line opacity was considered by means of an empirical procedure where it was attributed to a veil of weak Fe I lines; in the case of solar-type dwarfs, results were compared with those obtained using (LTE) mean intensities computed from OSMARCS models. We think that the empirical procedure produces better results for metal-poor stars, while mean intensities should perhaps be preferred for the Sun (where departures from LTE are anyway not very large). Collisions with both electrons and H I atoms were considered. Since cross sections for this second mechanism are very poorly known, we calibrated them empirically by matching observations of RR Lyrae variables at minimum light (discussed in Clementini et al., 1995, Cat. ). These stars were selected because non-LTE effects are expected to be larger in these stars than in those usually considered in the study of the chemical evolution of the Galaxy (cool main sequence and red giant branch stars). We found that different non-LTE mechanisms are important for the different species and transitions considered; on the whole, our calculations yielded moderate corrections to LTE abundances for high excitation O lines in warm dwarfs and giants, Na and Mg lines in giants and supergiants, and Fe I lines in F-supergiants (where corrections becomes very large for IR O lines). Non-LTE corrections were found to be negligible in the other cases studied.

(3 data files). Title: A high-resolution study of episodic mass loss from the carbon star TT Cygni Authors: Olofsson, H.; Bergman, P.; Lucas, R.; Eriksson, K.; Gustafsson, B.; Bieging, J. H. Bibcode: 2000A&A...353..583O Altcode: CO radio line observations with the IRAM Plateau de Bure interferometer show that the carbon star TT Cyg is surrounded by a large (radius ~ 35arcsec or 2.7x1017 cm), geometrically thin (average width ~ 2farcs 5 or 1.9x1016 cm) shell of gas, which has a remarkable overall spherical symmetry (e.g., its radius varies by less than +/-3%). It expands with a velocity of ~ 12.6 km s-1. The emitting gas is very evenly distributed in the shell when averaged over a solid angle of about 0.2 steradians. We estimate a molecular hydrogen density of ~ 250 cm-3, a gas kinetic temperature of ~ 100 K, and a mass of ~ 0.007 M_sun for the shell if the medium is homogeneous. There is no evidence for matter immediately inside or outside the shell, nor is there any evidence for structure in the radial direction of the shell brightness distribution (it is essentialy perfectly fitted with Gaussians). The shell centre is displaced ~ 1farcs 7 (position angle ~ -20degr ) with respect to the star. We favour an interpretation of this displacement in terms of TT Cyg being a member of a binary system. We put forward several arguments for a shell medium that consists almost entirely of a large number of small (la 1arcsec ) clumps (in which case the density required to fit the observational data is much higher, ~ 104 cm-3, and the kinetic temperature is considerably lower, la 20 K). TT Cyg is presently losing mass at a modest rate, ~ 3x10-8 M_sunpyr, and with a low expansion velocity, ~ 3.8 km s-1. This is inferred from CO line emission from a region centred on the present position of the star. The systemic velocity is estimated, from both the centre and the shell emission, to be -27.3+/-0.1 km s-1 in the LSR system. All quantitative results are obtained assuming the Hipparcos distance of 510 pc. These data strongly support that TT Cyg has recently ( ~ 7x103 yr ago) gone through a period of drastically varying mass loss properties. We discuss briefly two scenarios: a short period (a few hundred years) of very intense mass loss (a rate in excess of 10-5 M_sunpyr), and a related scenario with a more modest mass ejection and where most of the shell gas is swept-up from a previous, slower stellar wind. It is presently not possible to favour any of these two scenarios, but we suggest that in either case it is a coordinated mass ejection that caused the shell formation. The He-shell flash phenomenon in AGB-stars can provide this coordination, and it also fits the time scales involved. Title: The R Coronae Borealis stars - atmospheres and abundances Authors: Asplund, M.; Gustafsson, B.; Lambert, D. L.; Rao, N. K. Bibcode: 2000A&A...353..287A Altcode: An abundance analysis of the H-deficient and He- and C-rich R Coronae Borealis (R CrB) stars has been undertaken to examine the ancestry of the stars. The investigation is based on high-resolution spectra and line-blanketed H-deficient model atmospheres. The models successfully reproduce the flux distributions and all spectral features, both molecular bands and high-excitation transitions, with one important exception, the C i lines. Since photoionization of C i dominates the continuous opacity, the line strengths of C i are essentially independent of the adopted carbon abundance and stellar parameters. All predicted C i lines are, however, much too strong compared with observations, with a discrepancy in abundance corresponding to 0.6 dex with little star-to-star scatter. Various solutions of this ``carbon problem'' have been investigated. A possible solution is that classical model atmospheres are far from adequate descriptions of supergiants such as the R CrB stars. We can also not exclude completely, however, the possibility that the gf-values for the C i lines are in error. This is supported by the fact that the C ii, [C i] and C_2 lines are reproduced by the models with no apparent complications. In spite of the carbon problem, various tests suggest that abundance ratios are little affected by the uncertainties. Judging by chemical composition, the R CrB stars can be divided into a homogeneous majority group and a diverse minority, which is characterized by extreme abundance ratios, in particular as regards Si/Fe and S/Fe. All stars show evidence of H- and He-burning in different episodes as well as mild s-process enhancements. Four of the majority members are Li-rich, while overabundances of Na, Al, Si and S are attributes of all stars. An anti-correlation found between the H and Fe abundances of H-deficient stars remains unexplained. These enigmatic stars are believed to be born-again giants, formed either through a final He-shell flash in a post-AGB star or through a merger of two white dwarfs. Owing to a lack of theoretical predictions of the resulting chemical compositions, identification of the majority and minority groups with the two scenarios is unfortunately only preliminary. Furthermore, Sakurai's object and V854 Cen exhibit aspects of both majority and minority groups, which may suggest that the division into two groups is too simplistic. Title: Scattered Light from Envelopes around N-type Stars Authors: Gustafsson, Bengt; Eriksson, Kjell; Kiselman, Dan; Olander, Nils; Olofsson, Hans; Schwarz, Hugo E. Bibcode: 2000IAUS..177..409G Altcode: No abstract at ADS Title: Dust Dynamics of Transplanetary Disks Authors: Gustafson, Bo Å. S. Bibcode: 2000IAUJD...4E..11G Altcode: Forces acting on a given dust particle in Trans-Neptunian space differ in relative importance from the forces that the same grain would experience in the inner parts of the solar system. The Lorentz force due to solar wind interaction can no longer be neglected at Neptune's distance and is shown to cause dust orbits to precess along the solar equator. Alternating epochs of nodal recession and advance result from the change in magnetic field direction with the solar cycles. Secular perturbations are expected to cause dust structures reminiscent of the now well-known solar system dust bands in the asteroid belt. While the asteroid dust bands are induced by gravitational perturbations resulting primarily from the Jovian planets, the Lorentz-force induced dust bands that may extend parallel to the solar equator in Trans-Neptunian space are independent of the existence of any planets. It is therefore possible that the counterparts of the dust bands in extra solar dust disks may be mistaken for evidence for one or more planets. Ironically, the drag from interstellar gas would pump-up orbital eccentricities and would likely prevent a planet-induced ring from forming in our solar system at these large heliocentric distances. Title: Oxygen -- abundances and model atmospheres Authors: Gustafsson, Bengt Bibcode: 2000IAUJD...8E...7G Altcode: The uncertainties in current determinations of oxygen abundances of Pop II stars, resulting from systematic errors in models used to represent the stellar atmospheres, are analysed and discussed. Recommendations are given for abundance criteria to be selected and for model atmosperes to be used and developed further. Title: Deflection of the local interstellar dust flow by solar radiation pressure. Authors: Landgraf, M.; Augustsson, K.; Grün, E.; Gustafson, B. Å. S. Bibcode: 1999Sci...286.2319L Altcode: Interstellar dust grains intercepted by the dust detectors on the Ulysses and Galileo spacecrafts at heliocentric distances from 2 to 4 AU show a deficit of grains with masses from 1×10-17 to 3×10-16kg relative to grains intercepted outside 4 AU. To divert grains out of the 2- to 4-AU region, the solar radiation pressure must be 1.4 to 1.8 times the force of solar gravity. These figures are consistent with the optical properties of spherical or elongated grains that consist of astronomical silicates or organic refractory material. Pure graphite grains with diameters of 0.2 to 0.4 μm experience a solar radiation pressure force as much as twice the force of solar gravity. Title: Spectroscopic Observations of Convective Patterns in the Atmospheres of Metal-poor Stars Authors: Allende Prieto, Carlos; García López, Ramón J.; Lambert, David L.; Gustafsson, Bengt Bibcode: 1999ApJ...526..991A Altcode: 1999astro.ph..7046A; 1999astro.ph..7046P Convective line asymmetries in the optical spectrum of two metal-poor stars, Gmb 1830 and HD 140283, are compared to those observed for solar metallicity stars. The line bisectors of the most metal-poor star, the subgiant HD 140283, show a significantly larger velocity span that the expectations for a solar-metallicity star of the same spectral type and luminosity class. The enhanced line asymmetries are interpreted as the signature of the lower metal content, and therefore opacity, in the convective photospheric patterns. These findings point out the importance of the three-dimensional convective velocity fields in the interpretation of the observed line asymmetries in metal-poor stars and, in particular, urge caution when deriving isotopic ratios from observed line shapes and shifts using one-dimensional model atmospheres. The mean line bisector of the photospheric atomic lines is compared with those measured for the strong Mg I b1 and b2 features. The upper parts of the bisectors are similar, and-assuming they overlap-the bottom ends of the stronger lines, which are formed higher in the atmosphere, go much farther to the red. This is in agreement with the expected decreasing of the convective blueshifts in upper atmospheric layers, and is compatible with the high-velocity redshifts observed in the chromosphere, transition region, and corona in late-type stars. Title: A Consistency Test of Spectroscopic Gravities for Late-Type Stars Authors: Allende Prieto, Carlos; García López, Ramón J.; Lambert, David L.; Gustafsson, Bengt Bibcode: 1999ApJ...527..879A Altcode: 1999astro.ph..7155P; 1999astro.ph..7155A Chemical analyses of late-type stars are usually carried out following the classical recipe: LTE line formation and homogeneous, plane-parallel, flux-constant, and LTE model atmospheres. We review different results in the literature that have suggested significant inconsistencies in the spectroscopic analyses, pointing out the difficulties in deriving independent estimates of the stellar fundamental parameters and hence, detecting systematic errors. The trigonometric parallaxes measured by the Hipparcos mission provide accurate appraisals of the stellar surface gravity for nearby stars, which are used here to check the gravities obtained from the photospheric iron ionization balance. We find an approximate agreement for stars in the metallicity range -1.0<=[Fe/H]<=0, but the comparison shows that the differences between the spectroscopic and trigonometric gravities decrease toward lower metallicities for more metal-deficient dwarfs (-2.5<=[Fe/H]<=-1.0), which casts a shadow upon the abundance analyses for extreme metal-poor stars that make use of the ionization equilibrium to constrain the gravity. The comparison with the strong-line gravities derived by Edvardsson and Fuhrmann confirms that this method provide systematically larger gravities than the ionization balance. The strong-line gravities get closer to the physical ones for the stars analyzed by Fuhrmann, but they are even further away than the iron ionization gravities for the stars of lower gravities in Edvardsson's sample. The confrontation of the deviations of the iron ionization gravities in metal-poor stars, reported here with departures from the excitation balance found in the literature, show that they are likely to be induced by the same physical mechanism. Title: VizieR Online Data Catalog: The R CrB stars (Asplund+, 2000) Authors: Asplund, M.; Gustafsson, B.; Lambert, D. L.; Rao, N. K. Bibcode: 1999yCat..33530287A Altcode: Adopted line data, measured equivalent widths and derived elemental abundances for the individual lines observed in R Coronae Borealis and Extreme Helium stars. (2 data files). Title: Reply Authors: Knowles, S.; Meier, R. R.; Gustafson, B. Å. S.; Giovane, F. J. Bibcode: 1999JGR...10422609K Altcode: Abstract Available from AGU Title: The cosmic dust aggregation experiment CODAG Authors: Blum, Jürgen; Wurm, Gerhard; Poppe, Torsten; Kempf, Sascha; Fiethe, Björn; Giel, Michaela; Offterdinger, Peter; Neuhaus, Dietmar; Rott, Martin; Giovane, Frank; Gustafson, Bo Bibcode: 1999MeScT..10..836B Altcode: For the simulation of the first stage of preplanetary dust aggregation, we developed the cosmic dust aggregation experiment (CODAG). With CODAG, we intend to study the aggregational behaviour of a cloud of micron-sized dust particles due to Brownian motion of the grains. For a realistic simulation of the processes in the young solar system, the dust grains have to be dispersed in a rarefied gas so that mutual collisions are ballistic. Fast sedimentation of the grains in the Earth's gravitational field leads to unrealistic collision velocities and to a rapid loss of particles to the container walls. Therefore, CODAG was designed to work in a microgravity environment. In this paper, we present an overview of the experimental design of CODAG which was recently flown in a Get Away Special container during the STS-95 mission. Title: Abundances of light elements in metal-poor stars. II. Non-LTE abundance corrections Authors: Gratton, R. G.; Carretta, E.; Eriksson, K.; Gustafsson, B. Bibcode: 1999A&A...350..955G Altcode: We present non-LTE corrections to abundances of Fe, O, Na, and Mg derived from LTE analyses of F-K stars over a broad range of gravities and metal abundances; they were obtained using statistical equilibrium calculations and new model atoms. Line opacity was considered by means of an empirical procedure where it was attributed to a veil of weak Fe I lines; in the case of solar-type dwarfs, results were compared with those obtained using (LTE) mean intensities computed from OSMARCS models. We think that the empirical procedure produces better results for metal-poor stars, while mean intensities should perhaps be preferred for the Sun (where departures from LTE are anyway not very large). Collisions with both electrons and H I atoms were considered. Since cross sections for this second mechanism are very poorly known, we calibrated them empirically by matching observations of RR Lyrae variables at minimum light (discussed in Clementini et al. 1995). These stars were selected because non-LTE effects are expected to be larger in these stars than in those usually considered in the study of the chemical evolution of the Galaxy (cool main sequence and red giant branch stars). We found that different non-LTE mechanisms are important for the different species and transitions considered; on the whole, our calculations yielded moderate corrections to LTE abundances for high excitation O lines in warm dwarfs and giants, Na and Mg lines in giants and supergiants, and Fe I lines in F-supergiants (where corrections becomes very large for IR O lines). Non-LTE corrections were found to be negligible in the other cases studied. The Tables~1 to 12 are available only in electronic form at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/Abstract.html Title: ERRATUM: Comparison between Multisphere Light-scattering Calculations: Rigorous Solution and Discrete Dipole Approximation Authors: Xu, Yu-lin; Gustafson, Bo Å. S. Bibcode: 1999ApJ...522.1206X Altcode: In the paper ``Comparison between Multisphere Light-scattering Calculations: Rigorous Solution and Discrete Dipole Approximation'' by Yu-lin Xu and Bo Å. S. Gustafson (ApJ, 513, 894 [1999]), there is a minor error in the figures concerning the Müller matrix elements. This error involves Figures 8, 9, 10, 14, 22, 23, and 24, but not Figures 7 and 18. The corrected figures are shown below.

The authors thank Bruce T. Draine for bringing this error to their attention. Title: Experiments for in-situ monitoring of dust environments in the Solar System Authors: Colangeli, L.; Bussoletti, E.; Lopez Moreno, J. J.; Epifani, E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.; Maag, C.; Weissman, P. R. Bibcode: 1999DPS....31.2906C Altcode: "Dust" is present in the Solar System, from planetary surfaces to comets. The in-situ monitoring of its physical and dynamical properties is one of the main scientific tasks to be achieved in order to characterise grains and to correctly understand their role in the evolution of Solar System bodies. A new generation of methods for in-situ exploration of dusty environments in the Solar System has been studied and adopted in different instruments under development or study for future planetary space missions. Mass flux measurements by quartz crystal microbalances, optical detection of single grains and momentum monitoring by piezoelectric transducers are techniques which provide high sensitivity for grains at relatively low (below some hundreds m/s) velocities. The GIADA (Grain Impact Analyser and Dust Accumulator) experiment is part of the payload of the ESA Rosetta orbiter, targeted to a rendez-vous of 46P/Wirtanen comet. Thanks to GIADA, one of the prime scientific objectives of the mission will be fulfilled, i.e. the monitoring of the cometary coma dust environment. The dust flux from different directions vs. time and the momentum and velocity vs. mass of particles will be measured, while comet will approach the Sun. The MAGO (Martian Atmospheric Grain Observer) instrument, under study in the framework of the next Mars exploration opportunities (e.g.: Mars Surveyor Program 2003) adopts similar technical solutions and is aimed at measuring, directly for the first time, the dust mass flux in the Martian atmosphere and the dynamical properties of airborne particles vs. time. Finally, similar measurement techniques can be integrated with other detection/collection systems (e.g. aerogel collectors) to monitor the dust in the near Earth environment, e.g. from the space station. Title: Preliminary results on the circumstellar envelopes of alpha ORI and R Leo from CO 4.6 micron line emission Authors: Ryde, N.; Gustafsson, B.; Hinkle, K. H.; Eriksson, K.; Lambert, D. L.; Olofsson, H. Bibcode: 1999A&A...347L..35R Altcode: CO 4.6 mu m vibration-rotational lines are detected in fluorescent emission from the inner regions of the Betelgeuse (alpha Orionis) and R Leonis stellar winds. The spatially and spectrally resolved 1-0 R(1), R(2), and R(3) line profiles are found to be highly useful probes of circumstellar shells. The current data sample only a few regions of the circumstellar shells of the program stars. However, now it should be possible to obtain envelope maps and absolute flux estimates, allowing new independent estimates of mass loss rates. This will open up new possibilities in the study of the structure and dynamics of stellar winds around red giants. The temperature 4arcsec away from alpha Ori is found to be 38(+6}_{-5} {K) . For R Leo the temperature 4arcsec North is derived to be 24(+3}_{-2} {K) and 4arcsec South 35(+7}_{-4} {K) . Title: The Chemical Evolution of Carbon in the Galactic Disk Authors: Karlsson, T.; Edvardsson, B.; Gustafsson, B.; Olsson, E.; Ryde, N. Bibcode: 1999Ap&SS.265..261K Altcode: No abstract at ADS Title: A search for small comets with the Naval Space Command radar Authors: Knowles, S.; Meier, R. R.; Gustafson, B. Å. S.; Giovane, F. J. Bibcode: 1999JGR...10412637K Altcode: We have searched for the hypothetical small comets proposed by Frank et al. [1986a, b] and Frank and Sigwarth [1993] using the world's most powerful radar in terms of gain-aperture product. The Naval Space Surveillance System can detect most space objects in low Earth orbit with radar cross sections (RCSs) of 0.1 m2 or larger; at higher altitudes of the order of 10,000-20,000 km the radar can detect objects with RCSs of 1 m2. We carried out detailed first-principle calculations of the RCS of spherical comct using the properties proposed by Frank and Sigwarth [1993]. We find that 8-12 m diameter comets have an average cross section of 0.4 m2 at the radar frequency (217 MHz), with peaks reaching 1 m2. Therefore the Naval radar system has sufficient sensitivity to detect many small comets, especially as they approach low Earth orbit. We estimate that at least 800-5000 small comets should have been detected by the radar during the 37 day search period during fall 1997. None of the more than 12,000 unidentified detections can be explained by small comets. The lack of detection of small comets by the radar can be explained only if small comets have RCSs <0.1% of their assumed physical size (which is unrealistic, given that human technology can match this value only by tailoring a design for a specific radar) or if their impact rate with Earth is some 4 orders of magnitude less than proposed by Frank et al. [1986a] and Frank and Sigwarth [1993]. Title: On the determination of carbon isotopic ratios in cool carbon stars. II. Accuracy of the iso-intensity method for crowded spectra Authors: de Laverny, P.; Gustafsson, B. Bibcode: 1999A&A...346..520D Altcode: de Laverny & Gustafsson (1998, Paper I) questioned the iso-intensity method used by Ohnaka & Tsuji (1996) to derive carbon isotopic ratios in cool carbon stars. As a reply, Ohnaka & Tsuji (1998) pointed out that the method criticized in Paper I differs from the original one and conclude that our results are unreliable. No comparison of the two methods was, however, made. The iso-intensity method used in Paper I and OT96 do slighty differ in their definition. In investigating the consequences of this difference we have found that they are rather insignificant. We therefore confirm that the iso-intensity method is not reliable when applied to crowded spectra of cool stars. That reinforces the conclusions presented in Paper I. Title: Three years of Ulysses dust data: 1993-1995 Authors: Krüger, H.; Grün, E.; Landgraf, M.; Baguhl, M.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 1999P&SS...47..363K Altcode: 1998astro.ph..9133K The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse (i = 79°). After its Jupiter flyby in 1992 at a heliocentric distance of 5.4 AU, the spacecraftreapproached the inner solar system, flew over the Suns south polar region in September 1994,crossed the ecliptic plane at a distance of 1.3 AU in March 1995, and flew over the Suns northpolar region in July 1995. We report on dust impact data obtained with the dust detector onboardUlysses between January 1993 and December 1995. We publish and analyse the complete dataset of 509 recorded impacts of dust particles with masses between 10-16 g-10-7 g. Together with 968 dust impacts from launch until the end of 1992 published earlier ([Gruuml;n et al., 1995c]), information about 1477 particles detected with theUlysses sensor between October 1990 and December 1995 is now available. The impact ratemeasured between 1993 and 1995 stayed relatively constant at about 0.4 impacts per day andvaried by less than a factor of ten. Most of the impacts recorded outside about 3.5 AU arecompatible with particles of interstellar origin. Two populations of interplanetary particles havebeen recognized: big micrometer-sized particles close to the ecliptic plane and smallsub-micrometer-sized particles at high ecliptic latitudes. The observed impact rate is comparedwith a model for the flux of interstellar dust particles which gives relatively good agreement withthe observed impact rate. No change in the instruments noise characteristics or degradation of thechanneltron could be revealed during the three-year period. Title: Three years of Ulysses dust data: 1993-1995 Authors: rüger, H.; Grün, E.; Landgraf, M.; Baguhl, M.; Dermott, S.; Fechtig, H.; Gustafson, B. a.; Hamilton, D. P.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. a.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. a. m.; Morfill, G. e.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. a. Bibcode: 1999P&SS...47..363R Altcode: The Ulysses spacecraft is orbiting the Sun on a highly inclined ellipse (i = 79°). After its Jupiter flyby in 1992 at a heliocentric distance of 5.4 AU, the spacecraftreapproached the inner solar system, flew over the Suns south polar region in September 1994,crossed the ecliptic plane at a distance of 1.3 AU in March 1995, and flew over the Suns northpolar region in July 1995. We report on dust impact data obtained with the dust detector onboardUlysses between January 1993 and December 1995. We publish and analyse the complete dataset of 509 recorded impacts of dust particles with masses between 10-16 g-10-7 g. Together with 968 dust impacts from launch until the end of 1992 published earlier (Grün et al., 1995c), information about 1477 particles detected with theUlysses sensor between October 1990 and December 1995 is now available. The impact ratemeasured between 1993 and 1995 stayed relatively constant at about 0.4 impacts per day andvaried by less than a factor of ten. Most of the impacts recorded outside about 3.5 AU arecompatible with particles of interstellar origin. Two populations of interplanetary particles havebeen recognized: big micrometer-sized particles close to the ecliptic plane and smallsub-micrometer-sized particles at high ecliptic latitudes. The observed impact rate is comparedwith a model for the flux of interstellar dust particles which gives relatively good agreement withthe observed impact rate. No change in the instruments noise characteristics or degradation of thechanneltron could be revealed during the three-year period. Title: Comparison between Multisphere Light-scattering Calculations: Rigorous Solution and Discrete-Dipole Approximation Authors: Xu, Yu-lin; Gustafson, Bo Å. S. Bibcode: 1999ApJ...513..894X Altcode: We present the comparison of light-scattering calculations between a rigorous solution and the discrete-dipole approximation (DDA) for two-sphere aggregates. We also compare theoretical predictions with laboratory scattering measurements to examine the validity of the numerical solutions. It is found that there are cases in which the DDA solution, while satisfying the validity criterion for interdipole spacing to be small compared with the wavelength of incident radiation, deviates significantly from the rigorous solution and the experimental results. We show that the DDA works reasonably well for small-volume structures and that its validity is challenged, at least as it is currently implemented, when used on larger structures. We also show that, besides its advantages in reliability, the rigorous solution approach is far superior to the approximation method in computing efficiency as well. Title: The origin of carbon, investigated by spectral analysis of solar-type stars in the Galactic Disk Authors: Gustafsson, B.; Karlsson, T.; Olsson, E.; Edvardsson, B.; Ryde, N. Bibcode: 1999A&A...342..426G Altcode: 1998astro.ph.11303G Abundance analysis of carbon has been performed in a sample of 80 late F and early G type dwarf stars in the metallicity range {-1.06<=[Fe/H]<=0.26} using the forbidden [C i] line at 8727 Angstroms. This line is presumably less sensitive to temperature, atmospheric structure and departures from LTE than alternative carbon criteria. We find that {[C/Fe]} decreases slowly with increasing {[Fe/H]} with an overall slope of -0.17+/-0.03. Our results are consistent with carbon enrichment by superwinds of metal-rich massive stars but inconsistent with a main origin of carbon in low-mass stars. This follows in particular from a comparison between the relation of {[C/O]} with metallicity for the Galactic stars and the corresponding relation observed for dwarf irregular galaxies. The significance of intermediate-mass stars for the production of carbon in the Galaxy is still somewhat unclear. Based on observations carried out at the European Southern Observatory, La Silla, Chile. Title: The LMC Centre Unfing Authors: Ardeberg, A.; Linde, P.; Gustafsson, B. Bibcode: 1999IAUS..190..357A Altcode: 1998IAUS..190E.124A A deep study of individual stars has been made in the dense central part of the LMC Bar. Stromgren uvby photometry has been used with the HST PC and WFC and advanced image processing to obtain high spatial resolution data of high photometric accuracy for a field inaccessible with conventional tools. We have investigated star formation history and chemical abundance and evolution. Our study covers a magnitude interval from V=16 to V=26. Ages of stellar populations and star formation history are derived from a y versus b-y colour-magnitude diagram from V=16 to V=24 including approximately 4000 stars. Older populations range in age from 2 to 9 Gyears. Few if any stars are older than 10 Gyears or between 300 Myears and 2 Gyears. A striking feature is a young stellar component with ages below 300 Myears containing around 30% of the total amount of stars in the LMC centre. The abundance of heavy elements has been determined for a large number of stars close to the turn off point in the HR diagram. For the great majority of stars, the metallicity falls close to [Me/H] = -0.6 with a smaller amount of stars having [Me/H] values well below -1.0. Employing a new method, we have derived the faint end of the luminosity function down to V=26. The resulting luminosity function for the LMC Bar centre, from V=16 to V=26, is similar to that of the solar neighbourhood albeit somewhat steeper. Title: Dating Intermediate-and Low-Mass Stars Authors: Gustafsson, B. Bibcode: 1999ASPC..192...91G Altcode: 1999sdsg.conf...91G No abstract at ADS Title: The Centre of the LMC Bar - Analysis of HST Data Authors: Linde, P.; Ardeberg, A.; Gustafsson, B. Bibcode: 1999IAUS..190..359L Altcode: 1998IAUS..190E.125L Studies of star formation and stellar populations in the LMC Bar centre provide important data on galactic evolution. The stellar density and the distance make photometry the only tool realistic. However, image crowding implies an absolute need for front line instrumentation and sophisticated image processing techniques. The high image resolution of the HST is unique. For studies of a single field in the centre of the LMC Bar, we have used 14 hours of HST WFPC2 exposures and uvby photometry. Extraction of precision astrophysical data from raw HST images requires careful data processing. In the space environment, interference from cosmic radiation is a severe limiting factor for longer exposures. To allow a large field, the design of the WFPC2 notably under-samples the images. This is especially serious for crowded field photometry requiring high precision. We present results from some techniques minimising effects of cosmic radiation interference and image under-sampling. It is demonstrated that efficient cosmic ray elimination can provide close to intrinsic photometric accuracy. Further, image dithering and subsequent recombination enhance the quality of photometric analysis in the LMC core, affected by high image crowding and under-sampling as in WFPC2 frames. Title: The GIADA Experiment for Rosetta Mission to Comet 46P/Wirtanen: Design and Performances Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani, E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini, E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.; Gustafson, B.; Maag, C.; Weissmann, P. R. Bibcode: 1999AdSpR..24.1149B Altcode: Rosetta is one of the most ambitious missions planned by ESA for the beginning of the next millennium. It will explore from very close a comet nucleus along its trajectory up to perihelion. In the instrument complex forming the scientific payload, the GIADA (Grain Impact Analyser and Dust Accumulator) experiment is devoted to study the cometary dust flux evolution and grain dynamic properties. To achieve the required performances and the expected scientific return, GIADA has been designed as a multi-sensor instrument. It is able to detect grain passage by laser light scattering measurement, particle momentum through piezoelectric transducers and mass flux by means of quartz crystal microbalances. In this paper we describe the technical solutions and performances which have been reached on the development models of GIADA Title: Old Structure - Young Stars The Stellar Content of the Centre of the LMC Bar Authors: Linde, P.; Ardeberg, A.; Gustafsson, B. Bibcode: 1999IAUS..192..108L Altcode: No abstract at ADS Title: The nature of the circumstellar CO_2 emission from M giants Authors: Ryde, N.; Eriksson, K.; Gustafsson, B. Bibcode: 1999A&A...341..579R Altcode: 1998astro.ph.11330R The 13-16mu m region observed by the Infrared Space Observatory (ISO) of several ABG stars are discussed. We present and analyse spectra of seven M giants which show carbon dioxide features. To explain the features of the bands, we suggest they originate from two different circumstellar layers, one being a warm and high density layer close to the star, possibly making the 15mbox {\mum} band optically thick, and the other being a large, cold and optically thin layer extending far out in the wind. This could explain the difference in temperatures of the different bands found in the analysis of the spectra and the number of molecules needed for the emission. It is demonstrated that in spite of the bands probably not being formed in vibrational LTE, the temperatures can be estimated from the widths of the bands. Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with the participation of ISAS and NASA. The SWS is a joint project of SRON and MPE. Title: The GIADA experiment for ROSETTA mission to comet 46P/wirtanen: Design and performances Authors: Bussoletti, E.; Colangeli, L.; Lopez Moreno, J. J.; Epifani, E.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Girela, F.; Herranz, M.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Benini, E.; Casini, L.; Cherubini, G.; Coradini, A.; Giovane, F.; Grün, E.; Gustafson, B.; Maag, C.; Weissmann, P. R. Bibcode: 1999AdSpR..24.1139B Altcode: No abstract at ADS Title: Scattering by complex systems I: Methods Authors: Gustafson, B. Å. S. Bibcode: 1999ASIC..523..535G Altcode: 1999fess.conf..535G No abstract at ADS Title: Scattering by complex systems II: Results from microwave measurements Authors: Gustafson, B. Å. S.; Kolokolova, L.; Thomas-Osip, J. E.; Waldemarsson, K. W. T.; Loesel, J.; Xu, Y. -L. Bibcode: 1999ASIC..523..549G Altcode: 1999fess.conf..549G No abstract at ADS Title: Chemical Abundances of Local ``Unevolved'' Stars Authors: Gustafsson, Bengt Bibcode: 1999cezh.conf....1G Altcode: A number of results from work in recent years on chemical abundances in main-sequence late-type stars are discussed. This illuminates what may be discovered when the analyses are carried out with high S/N and high-resolution spectra, and with accurate and uniform methods for the analysis and the selection of fundamental stellar parameters. A major conclusion is that further new important discoveries as regards star formation, stellar and galactic evolution and nucleosynthesis will most probably result when the VLT UVES spectrometer, and the next generation of model atmospheres, are applied in such analyses. Title: Experiments for in-situ monitoring of dust environments in the Solar System. Authors: Colangeli, L.; Bussoletti, E.; López-Moreno, J. J.; Epifani, E.; Esposito, F.; Mennella, V.; Palomba, E.; Palumbo, P.; Rotundi, A.; Vergara, S.; Jeronimo, J. M.; Lopez-Jimenez, A. C.; Molina, A.; Morales, R.; Moreno, F.; Olivares, I.; Rodrigo, R.; Rodriguez-Gomez, J. F.; Ruiz-Falco, A.; Sanchez, J.; McDonnell, J. A. M.; Leese, M.; Lamy, P.; Perruchot, S.; Crifo, J. F.; Fulle, M.; Perrin, J. M.; Angrilli, F.; Coradini, A.; Giovane, F.; Gruen, E.; Gustafson, B.; Maag, C.; Weissman, P. R. Bibcode: 1999BAAS...31R1119C Altcode: No abstract at ADS Title: Late stages of stellar evolution Authors: Gustafsson, Bengt Bibcode: 1999anot.conf..254G Altcode: No abstract at ADS Title: A systematic study of light scattering by aggregate particles using the microwave analog technique: Angular and wavelength dependence of intensity and polarization Authors: Gustafson, Bo Å. S.; Kolokolova, Ludmilla Bibcode: 1999JGR...10431711G Altcode: Microwave analog experiments [e.g., Gustafson, 1996a, 1999] allow us to simulate light-scattering properties of particles of almost any combination of composition, size, and shape. We have taken advantage of this ability and the broadband nature of the University of Florida microwave facility in a systematic study of light scattering by aggregates. We present angular dependencies of intensity and polarization in the scattering angle range 0°-165°, and in the wavelength interval 2.7-4 mm, which simulates 0.430-0.660 μm in the visual. The data are for a variety of sizes, shapes, and compositions of the constituent particles, as well as the number of particles in an aggregate and their packing. Wavelength dependencies are shown to be powerful diagnostics for the interpretation of comet dust observations and we urge observers to report color and polarimetric color. As an example, we estimate the size of constituent particles in cometary grains (0.1-1μm). We also show that the grains evolve with the distance from the nucleus and that the reason apparently is the loss of some dark matter. Techniques and results reported here are general enough to apply to a broad range of natural and artificial aggregates. Title: The Chemical Evolution of Carbon in the Galactic Disk Authors: Karlsson, T.; Edvardsson, B.; Gustafsson, B.; Olsson, E.; Ryde, N. Bibcode: 1999gecd.conf..261K Altcode: No abstract at ADS Title: Convection in Metal-Poor Stars as Traced from Spectral Line Asymmetries Authors: Allende Prieto, C.; Asplund, M.; García López, R. J.; Gustafsson, B.; Lambert, D. L. Bibcode: 1999ASPC..173..205A Altcode: 1999sstt.conf..205A No abstract at ADS Title: Another r-Process-Enriched Halo Star: HD 115444 Authors: Westin, J.; Sneden, C.; Gustafsson, B.; Edvardsson, B.; Cowan, J. J. Bibcode: 1998AAS...193.4501W Altcode: 1998BAAS...30.1317W A new high resolution very high signal to noise spectrum has been obtained for the metal-poor giant star HD 115444, first examined in detail by Griffin et al. (1982, MNRAS, 198, 637). Our new spectrum was gathered with the High-Resolution Echelle Spectrometer of the McDonald Observatory 2.7m Telescope. We have performed a model atmosphere analysis and line identification, emphasizing the neutron-capture elements; 20 elements with Z>30 have been identified in the HD 115444 spectrum. The overall metallicity was found to be [Fe/H] = --3.0. The abundances of the light and iron-peak elements show the same pattern as other very metal-poor stars (e.g. overdeficiencies of Mn and Cr, overabundances of Co). The initial synthetic spectrum analyses reveal substantial overabundances of all neutron-capture elements with Z>=56 (Ba and beyond). Moreover, the abundance pattern is clearly consistent with production dominated by r-process nucleosynthesis (with little contribution from the s-process), just like that also found in the metal-poor giant star CS 22892-052 (Sneden et al., 1996, ApJ, 467, 819). To illustrate this, in HD 115444 we find [Ba/Eu] = --0.73, while in CS 22892-052, this ratio is --0.79. Thus HD 115444 becomes the second clear example of a very metal-poor yet r-process-rich halo giant. With (for example) [Eu/Fe] =~ +0.9, HD 115444 is a moderate version of CS 22892-052 (which has [Eu/Fe] =~ +1.7). Title: Three years of Galileo dust data: II. 1993-1995 Authors: Krüger, H.; Grün, E.; Hamilton, D. P.; Baguhl, M.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Riemann, R.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 1998P&SS...47...85K Altcode: 1999P&SS...47...85K; 1998astro.ph..9318K Between January 1993-December 1995, the Galileo spacecraft traversed interplanetaryspace between Earth and Jupiter and arrived at Jupiter on 7 December 1995. The dust instrumentonboard the spacecraft was operating during most of the time and data from the instrument wereobtained via memory readouts which occurred at rates between twice per day and once per week.All events were classified by an onboard program into 24 categories. Noise events were usuallyrestricted to the lowest categories (class 0). During Galileos passage through Jupiters radiationbelts on 7 December 1995, several of the higher categories (classes 1 and 2) also show evidencefor contamination by noise. The highest categories (class 3) were noise-free all the time. Arelatively constant impact rate of interplanetary and interstellar (big) particles of 0.4 impacts perday was detected over the whole three-year time span. In the outer solar system (outside about2.6 AU) they are mostly of interstellar origin, whereas in the inner solar system they are mostlyinterplanetary particles. Within about 1.7 AU from Jupiter intense streams of small dust particleswere detected with impact rates of up to 20,000 per day whose impact directions are compatiblewith a Jovian origin. Two different populations of dust particles were detected in Jovianmagnetosphere: small stream particles during Galileos approach to the planet and big particlesconcentrated closer to Jupiter between the Galilean satellites. There is strong evidence that thedust stream particles are orders of magnitude smaller in mass and faster than the instrumentscalibration, whereas the calibration is valid for the big particles. Because the data transmissionrate was very low, the complete data set for only a small fraction (2525) of all detected particlescould be transmitted to Earth; the other particles were only counted. Together with the 358particles published earlier, information about 2883 particles detected by the dust instrumentduring Galileos six years journey to Jupiter is now available. Title: A double-arm Møller Polarimeter for Jefferson Lab's Hall B Authors: Grún, E.; Krúger, H.; Dermott, S.; Fechtig, H.; Graps, A. L.; Zook, H. A.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Heck, A.; Horányi, M.; Kissel, J.; Lindbad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; Mcdonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 1998APS..DNP..B711G Altcode: We have constructed and commissioned a double-arm Møller polarimeter for the Hall B beamline at the Thomas Jefferson National Accelerator Facility. The polarimeter measures the longitudinal polarization of the 0.8-4.0 GeV electron beam as it enters the experimental hall. The primary components of the apparatus are a target chamber, a pair of quadrupole magnets, and a pair of lead/scintillating-fiber detectors. The target chamber contains two 20 μm-thick permendur foils tilted at ± 20^o with respect to the beam axis. A target polarization of approximately 8% is produced along the beam direction by a 90 G (nominal) magnetic field generated by a pair of Helmholtz coils. The scattered Møller-electron pairs are directed toward the detectors by the quadrupoles. The quadrupoles are are individually tuned--depending on the beam energy--to center the peak of the Møller asymmetry (θ_c.m.=90^o) onto the fixed detectors. The real-to-accidental coincident-detection rate is better than 200:1. The beam polarization can be measured to a 3% relative statistical precision in less than 30 minutes with a relative systematic uncertainty of less than 5%. Title: Galileo observes electromagnetically coupled dust in the Jovian magnetosphere Authors: Grün, E.; Krüger, H.; Graps, A. L.; Hamilton, D. P.; Heck, A.; Linkert, G.; Zook, H. A.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hanner, M. S.; Horányi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 1998JGR...10320011G Altcode: Measurements of dust coupled to the Jovian magnetosphere have been obtained with the dust detector on board the Galileo spacecraft. We report on data obtained during the first four orbits about Jupiter that had flybys of the Galilean satellites: Ganymede (orbits 1 and 2), Callisto (orbit 3), and Europa (orbit 4). The most prominent features observed are highly time variable dust streams recorded throughout the Jovian system. The impact rate varied by up to 2 orders of magnitude with a 5 and 10 hour periodicity, which shows a correlation with Galileo's position relative to the Jovian magnetic field. Around 20 RJ (Jupiter radius, RJ=71, 492 km) in bound a dip in the impact rate has been found consistently. At the same times, reversals by 180° in impact direction occurred. This behavior can be qualitatively explained by strong coupling of nanometer-sized dust to the Jovian magnetic field. At times of satellite flybys, enhanced rates of dust impacts have been observed, which suggests that all Galilean satellites are sources of ejecta particles. Inside about 20 RJ impacts of micrometer-sized particles have been recorded that could be particles on bound orbits about Jupiter. Title: Microwave analog study of light-scattering properties of aggregate particles for intepretation of cometary dust observations Authors: Kolokolova, L.; Gustafson, B. S.; Thomas-Osip, J.; Loesel, J. Bibcode: 1998DPS....30.4007K Altcode: 1998BAAS...30Q1090K Microwave analog experiments allow us to study particles of almost any combination of composition, size and shape. We have taken advantage of this ability and the broadband nature of the University of Florida microwave facility to obtain the intensity, polarization, color, and polarimetric color for a range of particle types. Here we present results for aggregates as the most probable type of cometary grains. These may be particles of size close to the wavelength of visible light aggregated to form structures very large compared to the wavelength. These circumstances make a theoretical study of the light scattered by cometary dust exceedingly difficult and, at least in part, beyond the capability of common numerical techniques. We selected aggregates made of polystyrene, nylon and a mixture of expanded plastic and iron oxide. These materials are, with their refractive indices near 1.6-0.03i, 1.74-0.005i, and 1.7 - 0.2i, microwave analogues to silicates and organic materials expected in cometary dust. The angular dependencies of intensity and polarization were obtained in the scattering angle range [0,165(o]) , and in the wavelength intervals [2.7-3] and [3.5-4] mm, to simulate cometary continuum filters at 0.442 and 0.642 microns . The study of light scattering properties of a range of aggregate types and the comparison of laboratory data with data of photometric and polarimetric observations of comets allow us not only to estimate the size and structure of cometary grains but also to study their evolution with distance from the nucleus. Title: Boron in Very Metal Poor Stars Authors: Garcia Lopez, Ramon J.; Lambert, David L.; Edvardsson, Bengt; Gustafsson, Bengt; Kiselman, Dan; Rebolo, Rafael Bibcode: 1998ApJ...500..241G Altcode: 1998astro.ph..1167G; 1998astro.ph..1167L We have observed the B I 2497 A line to derive the boron abundances of two very metal-poor stars selected to help in tracing the origin and evolution of this element in the early Galaxy: BD +23 3130 and HD 84937. The observations were conducted using the Goddard High Resolution Spectrograph on board the Hubble Space Telescope. A very detailed abundance analysis via spectral synthesis has been carried out for these two stars, as well as for two other metal-poor objects with published spectra, using both Kurucz and OSMARCS model photospheres, and taking into account consistently the NLTE effects on the line formation. We have also re-assessed all published boron abundances of old disk and halo unevolved stars. Our analysis shows that the combination of high effective temperature (Teff > 6000 K, for which boron is mainly ionized) and low metallicity ([Fe/H]<-1) makes it difficult to obtain accurate estimates of boron abundances from the B I 2497 A line. This is the case of HD 84937 and three other published objects (including two stars with [Fe/H] ~ -3), for which only upper limits can be established. BD +23 3130, with [Fe/H] ~ -2.9 and logN(B)_NLTE=0.05+/-0.30, appears then as the most metal-poor star for which a firm measurement of the boron abundance presently exists. The evolution of the boron abundance with metallicity that emerges from the seven remaining stars with Teff < 6000 K and [Fe/H]<-1, for which beryllium abundances were derived using the same stellar parameters, shows a linear increase with a slope ~ 1. Furthermore, the B/Be ratio found is constant at a value ~ 20 for stars in the range -3<[Fe/H]<-1. These results point to spallation reactions of ambient protons and alpha particles with energetic particles enriched in CNO as the origin of boron and beryllium in halo stars. Title: Steps toward interstellar silicate mineralogy. III. The role of aluminium in circumstellar amorphous silicates Authors: Mutschke, H.; Begemann, B.; Dorschner, J.; Guertler, J.; Gustafson, B.; Henning, Th.; Stognienko, R. Bibcode: 1998A&A...333..188M Altcode: It is a well-known fact that the spectra of oxygen-rich circumstellar dust envelopes around evolved stars show great diversity, especially in the 10 mu m silicate band profiles, but also in the longer infrared wavelength range covered by ISO. This supports earlier conclusions that the concept of a universal cosmic silicate is inadequate and that it is reasonable to consider a wider variety of possible silicate analogues as the basis for an improved modelling of the observed spectra. In the course of an investigation of the role of aluminium in cosmic dust, aluminosilicate glasses (ASGs) have been suggested as interesting laboratory analogues for this purpose. In these glasses, silicon ions within the SiO_4 tetrahedra are partly substituted by fourfold coordinated aluminium. In a new laboratory approach to the silicate dust problem, 13 ASG samples were prepared. Apart from magnesium and iron, the cosmically most abundant metals, sodium and calcium, were incorporated as cations. In this paper, these new silicate dust analogues are analytically and spectroscopically characterized. The spectroscopic results were obtained in the range from the UV to the far-infrared, in the millimetre wave range, and by Raman spectroscopy. Optical constants have been derived for the wavenumbers 1500-20 cm(-1) (6.7-500 mu m) from infrared reflectance measurements and for the frequencies 110-75 GHz (2.7-4 mm) from angle-resolved millimetre-wave scattering at spherical samples from two of the ASGs. For the electronic and vibrational absorption features, the dependence on the aluminium/silicon substitution ratio and on the glass structure is discussed. Relations between the calculated (Rayleigh case) band positions, widths and strengths of the IR absorption bands and the chemical compositions are derived. The application of the new data to the reproduction of observed stardust spectra of the IRAS-LRS catalogue shows promising results. Title: Is the Sun a Sun-Like Star? Authors: Gustafsson, B. Bibcode: 1998SSRv...85..419G Altcode: Various observable properties of the Sun are compared with those of solar-type stars. It is concluded that the Sun, to a remarkable degree, is “solar-type”. As regards its particular mass and age, and probably its non-binarity, “anthropic” explanations may seem in place. The possible tendency for the Sun, as compared with similar stars, to be somewhat rich in iron relative to other elements needs further exploration. This is also true concerning its presently small micro-variability amplitude. Title: VizieR Online Data Catalog: G and K dwarfs abundances (Feltzing+ 1998) Authors: Feltzing, S.; Gustafsson, B. Bibcode: 1998yCat..41290237F Altcode: The table presents the abundances of all 47 dwarf stars analysed in the paper. We give abundances relative to the Sun in the standard notation of [X/H]=log(X/H)star-log(X/H)⊙. The 5 K dwarf stars and 3 stars in common with Barbuy & Grenon (1990) appear at the end of the table. The label of each column indicates the ion the quoted abundances are derived from. For each star we give the abundance, [X/H], the line-to-line scatter (if more than one line is used) and the number of lines used. The stars are ordered in the same way as in Table 1 in the paper, ie. the K dwarf stars and the stars in common with Barbuy & Grenon (1990) are found at the end. (2 data files). Title: Abundance similarities between the RCrB star V854Cen and the born-again Sakurai's object Authors: Asplund, Martin; Gustafsson, Bengt; Kameswara Rao, N.; Lambert, David L. Bibcode: 1998A&A...332..651A Altcode: 1998astro.ph..1068A The elemental abundances of the mildly hydrogen-deficient R Coronae Borealis (RCrB) star V854Cen have been estimated. The RCrB stars have been divided into majority and minority classes judging by their abundance patterns. Class assignment has previously been unambiguous but V854Cen has traits of both the minority and majority class. Neither V854Cen nor the three obvious minority members show any clear abundance signatures of having been affected by e.g. dust-gas separation as often observed in post-AGB stars. By chemical composition, V854Cen closely resembles Sakurai's object, which has probably recently experienced a final He-shell flash. Therefore V854Cen and Sakurai's object may share the same evolutionary background, which would add support for the final-flash scenario as a viable origin of the RCrB stars. Most of the few differences in abundance ratios between the stars could if so be attributed to milder H-ingestion in connection with the final He-shell flash of V854Cen. The identification of either the majority or the minority group, if any, as final flash objects, remain uncertain, however, due to the unclear membership status of V854Cen. Title: South-North and radial traverses through the interplanetary dust cloud Authors: Gruen, E.; Staubach, P.; Baguhl, M.; Hamilton, D. P.; Zook, H. A.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hanner, M. S.; Horanyi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 1998exdu.work..270G Altcode: Identical in situ dust detectors are flown on board the Galileo and Ulysses spacecraft. They record impacts of micrometeoroids in the ecliptic plane at heliocentric distances from 0.7 to 5.4 AU and in a plane almost perpendicular to the ecliptic from -79 deg to +79 deg ecliptic latitude. The combination of both Ulysses and Galileo measurements yield information about the radial and latitudinal distributions of micron and sub-micron sized dust in the solar system. Two types of dust particles were found to dominate the dust flux in interplanetary space: (1) Interplanetary micrometeoroids covering a wide mass range from 10-16 to 10-6 gr are mostly recorded inside 3 AU, and at latitudes below 30 deg; and (2) Interstellar grains with masses between 10-14 and 10-12 gr have been positively identified outside 3 AU near the ecliptic plane and outside 1.8 AU at high ecliptic latitudes (> 50 deg). Interstellar grains move on hyperbolic trajectories through the planetary system and constitute the dominant dust flux (1.5 x 10-4/ sq m sec) in the outer solar system and at high ecliptic latitudes. In order to compare and analyze the Galileo and Ulysses data sets, a new model is developed based on Divine's (1993) "Five populations of interplanetary meteoroids" model. By using this model, which takes into account the measured velocities and the effect of radiation pressure on small particles, we define four populations of meteoroids on elliptical orbits plus one population on hyperbolic orbits that all can fit the micrometeoroid flux observed by Galileo and Ulysses. Title: Abundances in metal-rich stars. Detailed abundance analysis of 47 G and K dwarf stars with [Me/H] > 0.10 dex Authors: Feltzing, S.; Gustafsson, B. Bibcode: 1998A&AS..129..237F Altcode: 1997astro.ph.10315F We have derived elemental abundances of O, Na, Mg, Al, Si, Ca, Ti, Cr, Mn, Fe, Co, Ni as well as for a number of s-elements for 47 G and K dwarf, with [Me/H]>0.1 dex. The selection of stars was based on their kinematics as well as on their uvby-beta photometry. One sample of stars on rather eccentric orbits traces the chemical evolution interior to the solar orbit and another, on circular orbits, the evolution around the solar orbit. A few Extreme Population I stars were included in the latter sample. The stars have -0.1 dex < [Fe/H] < 0.42 dex. The spectroscopic [Fe/H] correlate well with the [Me/H] derived from uvby-beta photometry. We find that the elemental abundances of Mg, Al, Si, Ca, Ti, Cr and Ni all follow [Fe/H]. Our data put further constraints on models of galactic chemical evolution, in particular of Cr, Mn and Co which have not previously been studied for dwarf stars with [Me/H] >0.1 dex. The increase in [Na/Fe] and [Al/Fe] as a function of [Fe/H] found previously by \cite[Edvardsson et al. (1993a)]{Edv93} has been confirmed for [Na/Fe]. This upturning relation, and the scatter around it, are shown not to be due to a mixture of populations with different mean distances to the galactic centre. We do not confirm the same trend for aluminium, which is somewhat surprising since both these elements are thought to be produced in the same environments in the pre-supernova stars. Nor have we been able to trace any tendency for relative abundances of O, Si, and Ti relative to Fe to vary with the stellar velocities, i.e. the stars present mean distance to the galactic centre. These results imply that there is no significant difference in the chemical evolution of the different stellar populations for stars with [Me/H]>0.1 dex. We find that [O/Fe] continue to decline with increasing [Fe/H] and that oxygen and europium correlate well. However [Si/Fe] and [Ca/Fe] seem to stay constant. A real (``cosmic'') scatter in [Ti/Fe] at given [Fe/H] is suggested as well as a decreasing abundance of the s-elements relative to iron for the most metal-rich dwarf stars. We discuss our results in the context of recent models of galactic chemical evolution. In our sample we have included a few very metal rich stars, sometimes called SMR (super metal rich) stars. We find these stars to be among the most iron-rich in our sample but far from as metal-rich as indicated by their photometric metallicities. SMR stars on highly eccentric orbits, alleged to trace the evolution of the chemical evolution in the galactic Bulge, have previously been found overabundant in O, Mg and Si. We have included three such stars from the study by \cite[Barbuy & Grenon (1990)]{Bar90}. We find them to be less metal rich and the other elemental abundances remain puzzling. Detailed spectroscopic abundance analyses of K dwarf stars are rare. Our study includes 5 K dwarf stars and has revealed what appears to be a striking example of overionization. The overionization is especially prominent for Ca, Cr and Fe. The origin of this apparent overionization is not clear and we discuss different explanations in some detail. Based on observations at the McDonald Observatory. Title: On the determination of carbon isotopic ratios in cool carbon stars Authors: de Laverny, P.; Gustafsson, B. Bibcode: 1998A&A...332..661D Altcode: We discuss the determination of carbon isotopic ratios (12C) / (12C) iso in N-type Galactic carbon stars. Ohnaka & Tsuji (1996) reported (12C) / (12C) iso ratios smaller by a factor 2 or 3 than the determinations of Lambert et al. (1986). Using synthetic spectra of carbon stars, we analyse systematic errors in their iso-intensity method. It is found to be rather sensitive to model parameters and blends. Furthermore, there are large discrepancies between the effective temperatures adopted by these two studies (mean discrepancy close to 260 K for the 20 stars in common). That, together with uncertainties due to model atmospheres, to carbon enrichments and effects of the blends, could explain most of the discrepancies between these two studies. The LGEH86 analysis is, on the other hand, rather insensitive to model parameters. We therefore conclude that large (12C) / (12C) iso ratios in cool Galactic carbon stars should be favoured. Title: A thin molecular shell around the carbon star TT CYG Authors: Olofsson, H.; Bergman, P.; Lucas, R.; Eriksson, K.; Gustafsson, B.; Bieging, J. H. Bibcode: 1998A&A...330L...1O Altcode: Interferometric CO({\jtra10} and {\tra21}) observations reveal a remarkably thin shell of molecular gas around the carbon star TT Cyg, width/radius la 1farcs 3/34arcsec ~ 0.04. It expands at ~13{km s(-1) , and contains ~ 0.02M_sun of gas provided the CO abundance with respect to H_2 is 10(-3) and the distance is 1kpc. Only about a quarter of the shell has been mapped, but we infer an overall spherical shell with only small, but clear, deviations at the per cent level. The radial structure of the shell is barely resolved at the arc second level, but there exists weak emission extending a few arc seconds inwards from the peak. A drastic change in mass loss properties, possibly combined with the effects of interacting winds, provides the most likely explanation to the origin of the shell. % Title: Tentative Detection of Circumstellar CO2 from the AGB Star R Crateris Authors: Ryde, N.; Eriksson, K.; Gustafsson, B.; Lindqvist, M.; Olofsson, H. Bibcode: 1998Ap&SS.255..301R Altcode: 1997Ap&SS.255..301R We report on and discuss the detection of an emission feature at 14.98 µm from the oxygen-rich, semi-regularly pulsating Asymptotic Giant Branch star R Crateris, a feature which we suggest to be due to the <Stack> 0 1 </Stack> Q-branch of circumstellar CO2. We also suggest a reasonable excitation mechanism, which could explain the height, the width and the asymmetry of the feature. Title: DFA-the dust flux analyzer for the Rosetta orbiter Authors: Lamy, P.; Perruchot, S.; Reynaud, J. -L.; Leese, M. R.; McDonnell, J. A. M.; Green, S. F.; Busoletti, E.; Colangeli, L.; Fulle, M.; Rotundi, A.; Giovane, F.; Gustafson, B.; Perrin, J. -M. Bibcode: 1998AdSpR..21.1557L Altcode: We describe the scientific objectives, the design concept and the implementation of the Dust Flux Analyser (DFA) for the ESA Rosetta mission. DFA is designed to detect individual dust particles in order to study their physical and dynamical properties as a function of time and of orbital position, to monitor the spatial distribution of the dust production and correlate it with the nucleus emission sites and to analyse gas-dust interactions and the evolution of the coma. The instrument is composed of three detectors with a common electronic box. The Velocity Measurement System (VMS) will measure the velocity of the incoming dust particles and the dust detector (MOM), its momentum. A separate deposition system (DEP) composed of three quartz microbalances will monitor the cometary dust flux in three directions. DFA will be able to detect dust particles in the size range 5-1000 μm and velocity range 0.1-150 m.s^-1. Required resources are a mass of 4.9 kg, a power of 3.6 W to 16.7 W and a telemetry of 50 to 512 kBits per hour depending upon the operating modes. Title: Modelling of molecular bands of oxygen-rich AGB stars Authors: Ryde, N.; Eriksson, K.; Gustafsson, B.; Olofsson, H.; Plez, B. Bibcode: 1998IAUS..191P.118R Altcode: ISO observations of infrared molecular bands of oxygen-rich AGB stars are compared with synthetic spectra generated using model atmospheres from the new large grid of model atmospheres that we are currently calculating with the newest MARCS code in spherical geometry. Seven molecular bands of eight M-giants, observed by ISO in medium resolution mode (SWS06), are analysed in this way. Title: Cosmic Dust Exploration Using Broadband Microwave Analogues Authors: Gustafson, B. E. S.; Kolokolova, L.; Loesel, J.; Thomas-Osip, J.; Waldemarsson, T.; Xu, Y. -L. Bibcode: 1998lss..work..143G Altcode: No abstract at ADS Title: Modelling of ISO-SWS spectra of red giants Authors: Decin, L.; Cohen, M.; Eriksson, K.; Gustafsson, B.; Huygen, E.; Morris, P.; Plez, B.; Sauval, J.; Vandenbussche, B.; Waelkens, C. Bibcode: 1998IAUS..191P.120D Altcode: The modelling and interpretation of the ISO-SWS (Infrared Space Observatory - Short Wavelength Spectrometer) data require accurately calibrated spectrometers. In the SWS spectral region (2.38-45.2 microns) the primary standard calibration candles are bright, mostly cool, stars. The better these calibration sources are known in the infrared, the more accurate the spectrometers can be calibrated. Since ISO offers the first opportunity to observe in the infrared with a resolving power of ~1500, our knowledge on stellar sources -and more specifically on stellar atmospheres- is not so refined. A full exploitation of the ISO data will therefore result from an iterative process in which both accurate observations and new modelling are involved. A comparison between the observed SWS spectra and the predicted ones based on the Opacity Sampling spherical models of B. Plez (Plez et al., 1992; 1993) is performed. This reveals not only calibration problems, but also shortcomings in generating the synthetic spectra. Our results will not only contribute to a better calibration of the ISO-SWS data, but also to a better understanding and modelling of the atmosphere of cool giants. Title: Mid and far-infrared spectra of the third brightest carbon star IRAS 15194-5115 Authors: Ryde, N.; Eriksson, K.; Gustafsson, B.; Jorgensen, U. G.; Nyman, L. -Aa.; Olofsson, H.; Plez, B.; Wolstencroft, R. Bibcode: 1998IAUS..191P.312R Altcode: ISO observations from 2 to 197 microns of the recently discovered, third brightest (at 12 microns) carbon star IRAS 15194-5115, are analysed. Eighty spectra, covering the entire range from 2.3 microns to 45 microns, were observed in the ISO medium-high resolution mode (SWS06). Also, observations were made with the ISO long wavelength spectrometer (LWS) from 42 to 197 microns. The evolutionary stage and chemistry are discussed and a comparison to the similar carbon star IRC+10216 is made. Title: Experimental Verification of Multisphere Light-Scattering Calculations: I) Rigorous Solution and II) the DDA Authors: Xu, Yu-Lin; Gustafson, Bo E. S. Bibcode: 1998lss..work..270X Altcode: No abstract at ADS Title: Is the Sun a Sun-like Star? Authors: Gustafsson, B. Bibcode: 1998sce..conf..419G Altcode: No abstract at ADS Title: Episodic mass loss of the carbon star TT CYG Authors: Olofsson, H.; Bergman, P.; Lucas, R.; Eriksson, K.; Gustafsson, B.; Bieging, J. H. Bibcode: 1998IAUS..191P.415O Altcode: There exists now seven carbon stars for which there is good evidence that the mass loss has been highly episodic. Detached gas shells were first imaged in circumstellar CO emission, R Scl, U Ant, S Sct, and TT Cyg (see Olofsson et al. 1996), or in other molecular line emissions, U Cam. Detached dust shells have been observed towards U Hya, Y CVn, and U Ant (probably two shells). So far there is only one M-star for which a similar detached shell has been found, R Hya. It has been suggested that these shells are due to episodic high mass loss rate events connected with the thermal pulses of the central star. In this poster we present high resolution (~2 arcsecond) CO(J = 1-0) observations of the carbon star TT Cyg performed with the IRAM interferometer on Plateau de Bure, France (a minor part of the data have been presented in Olofsson et al. 1998). To cover the entire shell we have observed eight primary fields. We have used four configurations to be sensitive to extended as well as sharply peaked emission. The data reveal an overall close to spherically symmetric, very narrow (width/radius approximately less than 0.04, except to the north) shell. Yet, there are clear deviations from perfect spherical symmetry, e.g., the star does not lie exactly at the centre of the shell, which appears to break up in the north. The brightness distribution is very patchy. If the shell is due to a phase of substantially increased mass loss, the time scale for this phase is at most a few hundred years and the mass loss rate must have approached 10^{-4} Modot yr^{-1} ~5000 years ago (adopting the HIPPARCOS distance of ~500 pc). The present mass loss of the star is very low. Title: Images in scattered light of detached circumstellar shells Authors: Delgado, D. G.; Olofsson, H.; Schwarz, H.; Eriksson, K.; Gustafsson, B. Bibcode: 1998IAUS..191P.404D Altcode: The temporal variations of the mass loss rate of an AGB-star as it evolves is to a large extent unknown. This applies to all time scales from the pulsation period to the full time scale for the AGB-phase. For the shortest time scales we are limited by the spatial resolution of the observations, while for the longest time scales we lack suitable observational probes. On the intermediate time scales (10^2-10^4 yr) there is now growing evidence for substantial variations in the mass loss rate, perhaps due to the effects of thermal pulses. Some of the best examples are provided by CO radio line observations of detached gas shells, and at least in one case the shell is extremely narrow compared to its radius (width/radius approximately less than 0.04, see P4-15). The interpretation of the CO data are hampered by the fact that the emission depends on the excitation as well as the photodissociation of the CO-molecules, and hence the relation between the density distribution (and consequently the mass loss history) and the brightness distribution is uncertain. Here we present images obtained in 50 AA narrow filters (centered on the KI and Na D lines) with the ESO 3.6m telescope of three carbon stars with detached CO shells: R Scl, U Ant, and S Sct. In the two former we detect light scattered in extended envelopes. The brightness is relatively constant out to a relatively sharp outer radius, R Scl (~19 arcsecond) and U Ant (~41 arcsecond). For U Ant this radius coincides exactly with the observed peak radius of the CO shell. For R Scl this radius coincides with the outer radius of the CO distribution (as estimated from a model fit to the CO data; the CO shell is only marginally resolved and hence its radius is not well determined). [In the case of S Sct, with the largest CO shell radius (~70 arcsecond), no scattered light is detected.] This strongly supports the conclusion that the density distribution has a sharp outer edge. The shell distribution of the CO emission can only be reasonably explained by a sharp inner edge of the density distribution. Hence, these stars have gone through a period of significant change in the mass loss rate. Whether the shells are formed by a brief period of very enhanced mass loss, or are due to a faster wind sweeping up material from a slower wind remains to be determined. Title: Evidence for Comet Dust Evolution based on Microwave Analogue Experiments and Polarimetric Observations Authors: Kolokolova, L.; Gustafson, B. E. S.; Loesel, J.; Thomas-Osip, J. Bibcode: 1998lss..work..170K Altcode: No abstract at ADS Title: The centre of the LMC bar Authors: Ardeberg, A.; Linde, P.; Snel, R.; Gustafsson, B.; Nissen, P. E. Bibcode: 1998IAUS..184..135A Altcode: With the HST PC and uvby photometry, we investigate evolutionary signatures in a field in the centre of the LMC Bar. Field stars close to the turn off point in the HR diagram are used for a study of ages and evolution of the stellar populations dominating the Bar as well as for determination of the abundance of heavy elements. Including fainter stars, we derive the corresponding luminosity function. Here, we discuss some results obtained from a preliminary version of our data. The quality of our data is high. Two strong stellar populations are obvious. A young component contains approximately 30% of the total number of stars. At least a considerable fraction of this component originated less than 500 Myears ago. The older population ranges in age between around 2 and 9 G years. The abundance of heavy elements is around [Me/H] = -0.6. The tentative luminosity function, down to y = 24, resembles in shape that predicted from earlier galactic and LMC data. Parallel to arrival of further HST data, our analysis continues. Title: Molecules in Stellar Atmospheres Authors: Gustafsson, B. Bibcode: 1998Ap&SS.255..241G Altcode: 1997Ap&SS.255..241G The effects of molecules on model stellar atmospheres are briefly reviewed. Molecular diagnostics of stellar fundamental parameters and of atmospheric structure are discussed, and the presently emerging "ISO picture" of the outer regions of stars is commented upon. Title: The rise and fall of the NaMgAl stars. Authors: Tomkin, J.; Edvardsson, B.; Lambert, D. L.; Gustafsson, B. Bibcode: 1997A&A...327..587T Altcode: 1997astro.ph..7208T We have made new abundance determinations for a sample of NaMgAl stars. These stars, which are a subgroup of the nearby metal-rich field F and G disk dwarfs, were first identified by Edvardsson et al. (1993A&A...275..101E) on the basis of their apparent enrichment in Na, Mg and Al relative to other elements. The discovery of a planetary companion to the nearby solar type star 51 Peg (Mayor & Queloz, 1995Natur.378..355M) combined with Edvardsson et al.'s earlier identification of 51 Peg as a NaMgAl star highlighted the group's potential importance. Our new analysis, which uses new spectra of higher resolution and better wavelength coverage than the analysis of Edvardsson et al., shows that the Na, Mg and Al abundances of the NaMgAl stars are indistinguishable from those of non-NaMgAl stars with otherwise similar properties. The group thus appears to be spurious. Our study, which includes 51 Peg, also provides the most complete set of abundances for this star available to date. The new Fe abundance, [Fe/H]=+0.20+/-0.07, of 51 Peg confirms earlier measurements of its metal richness. Abundances for 19 other elements, including C, N and O, reveal a fairly uniform enrichment similar to that of Fe and show no evidence of abnormality compared to other metal rich stars of similar spectral type. Title: South-North and Radial Traverses through the Interplanetary Dust Cloud Authors: Grün, E.; Staubach, P.; Baguhl, M.; Hamilton, D. P.; Zook, H. A.; Dermott, S.; Gustafson, B. A.; Fechtig, H.; Kissel, J.; Linkert, D.; Linkert, G.; Srama, R.; Hanner, M. S.; Polanskey, C.; Horanyi, M.; Lindblad, B. A.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Schwehm, G. Bibcode: 1997Icar..129..270G Altcode: Identicalin situdust detectors are flown on board the Galileo and Ulysses spacecraft. They record impacts of micrometeoroids in the ecliptic plane at heliocentric distances from 0.7 to 5.4 AU and in a plane almost perpendicular to the ecliptic from -79° to +79° ecliptic latitude. The combination of both Ulysses and Galileo measurements yields information about the radial and latitudinal distributions of micron- and sub-micron-sized dust in the Solar System. Two types of dust particles were found to dominate the dust flux in interplanetary space. Interplanetary micrometeoroids covering a wide mass range from 10-16to 10-6g are recorded mostly inside 3 AU and at latitudes below 30°. Interstellar grains with masses between 10-14and 10-12g have been positively identified outside 3 AU near the ecliptic plane and outside 1.8 AU at high ecliptic latitudes (>50°). Interstellar grains move on hyperbolic trajectories through the planetary system and constitute the dominant dust flux (1.5 × 10-4m-2sec-1) in the outer Solar System and at high ecliptic latitudes.

To compare and analyze the Galileo and Ulysses data sets, a new model is developed based onJ. Geophys. Res.98,17029-17048, Divine's (1993, “five populations of interplanetary meteoroids” model. Both models describe the interplanetary meteoroid environment in terms of dust populations on distinct orbits. Taking into account the measured velocities and the effect of radiation pressure on small particles (described by the ratio of radiation pressure force to gravity, β), we define four populations of meteoroids on elliptical orbits and one population on hyperbolic orbit that can fit the micrometeoroid flux observed by Galileo and Ulysses. Micrometeoroids with masses greater than 10-10g and negligible radiation pressure (β = 0) orbit the Sun on low to moderately eccentric orbits and with low inclinations (≤30°). Populations of smaller particles with mean masses of 10-11g (β = 0.3), 10-13g (β = 0.8), and 5 × 10-15g (β = 0.3), respectively, have components with high eccentricities and have increasingly wider inclination distributions with decreasing mass. Similarities among the orbit distributions of the small particle populations on bound orbits suggest that all are genetically related and are part of an overall micrometeoroid complex that prevails in the inner Solar System. The high-eccentricity component of the small particle populations may actually be β-meteoroids which are not well characterized by our measurements. Our modeling suggests further that the interstellar dust flux is not reduced at Ulysses' perihelion distance (1.3 AU) and that it contributes about 30% of the total dust flux observed there. Title: VizieR Online Data Catalog: Abundances of 9 solar-type stars (Tomkin+ 1997) Authors: Tomkin, J.; Edvardsson, B.; Lambert, D. L.; Gustafsson, B. Bibcode: 1997yCat..33270587T Altcode: Line identifications, measured equivalent widths and derived chemical abundances in 9 solar-type dwarf stars, which are identified by their Bright Star (HR, (Cat. <V/50>)) numbers. (1 data file). Title: Hubble Space Telescope Spectroscopy of the Carbon Star TX Piscium Authors: Carpenter, Kenneth G.; Robinson, Richard D.; Johnson, Hollis R.; Eriksson, Kjell; Gustafsson, Bengt; Pijpers, Frank P.; Querci, Francois; Querci, Monique Bibcode: 1997ApJ...486..457C Altcode: Ultraviolet spectra obtained with the Hubble Space Telescope of the carbon star TX Piscium (HR 9004) are presented, along with analysis providing information on its outer atmosphere, including flow and turbulent velocities, line formation mechanisms, and variations with time. Both thermal (collisionally excited) and fluorescent emission from the chromosphere of the star appear to be formed near the stellar rest velocity, i.e., in a region below that in which the stellar wind is accelerated. Absorption self-reversals in the Mg II emission confirm the presence of an outflowing stellar wind at a mean velocity of about 9-10 km s-1. Circumstellar absorption features (Mn I and Fe I) overlying the Mg II emission indicate a cool shell expanding at about 5-6 km s-1 relative to the photosphere. The widths (FWHM) of various emission lines indicate that the chromospheric turbulence is at least 16 km s-1, but that it may increase with altitude to as much as 34 km s-1. Three hours of integration on the C II] lines are examined for any signs of variability that might indicate the presence of shocks, but no statistically significant variations are seen. A previous identification (in spectra of UU Aur) of an emission line at 2807 Å, seen only in spectra of carbon stars, as belonging to Fe I multiplet UV45 pumped by the C II] line at 2325 Å is confirmed by the discovery of an absorption feature corresponding exactly to the wavelength of the pumped transition (Fe I UV13) near 2325 Å. Lines from Fe II UV165, previously seen in solar off-limb spectra and in Goddard High-Resolution Spectrograph spectra of α Tau, are clearly present. The normally much stronger Fe II UV32, 62, and 63 multiplets are seen but are weaker relative to both the UV165 lines and the intercombination lines of C II] and Si II] than in α Tau. The weakness of these Fe II lines is indicated both by their absolute flux levels and by their narrow, single-peaked profiles, which are in sharp contrast to the broad, double-peaked profiles seen in oxygen-rich cool giant and supergiant stars. The weakness of the Fe II lines and the presence of the Fe I 2807 Å line suggest that the ionization fraction of iron (Fe II/Fe I) is significantly lower in the outer atmospheres of carbon stars. Fluxes in emission lines of Fe II and Mg II are >=2-3 times lower than in a 1984 IUE spectrum of TX Psc, confirming that the latter was obtained at an epoch of unusual UV brightness for the star. The Mg II profiles are heavily mutilated by overlying absorption, even more so than in 1984. The TX Psc profiles are very similar to those seen in the carbon star TW Hor but are dramatically different than those in another carbon star, UU Aur, whose lines show violet wing emission out to much shorter wavelengths than in the other two stars.

Based on observations with the NASA/ESA Hubble Space Telescope, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555 and on observations at the Haute-Provence Observatory. Title: Dust measurements in the Jovian magnetosphere Authors: Grun, E.; Kruger, H.; Dermott, S.; Fechtig, H.; Graps, A. L.; Zook, H. A.; Gustafson, B. A.; Hamilton, D. P.; Hanner, M. S.; Heck, A.; Horanyi, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 1997GeoRL..24.2171G Altcode: Dust measurements have been obtained with the dust detector onboard the Galileo spacecraft inside a distance of about 60RJ from Jupiter (Jupiter radius, RJ = 71,492 km) during two periods of about 8 days around Galileo's closest approaches to Ganymede on 27 June and on 6 Sept 1996. The impact rate of submicrometer-sized particles fluctuated by a factor of several hundred with a period of about 10 hours, implying that their trajectories are strongly affected by the interaction with the Jovian magnetic field. Concentrations of small dust impacts were detected at the times of Ganymede closest approaches that could be secondary ejecta particles generated upon impact of other particles onto Ganymede's surface. Micrometer-sized dust particles, which could be on bound orbits about Jupiter, are concentrated in the inner Jovian system inside about 20RJ from Jupiter. Title: (Erratum) Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars. Authors: Asplund, M.; Gustafsson, B.; Kiselman, D.; Eriksson, K. Bibcode: 1997A&A...323..286A Altcode: Erratum to Astron. Astrophys. 318, 521-534 (1997) Title: Light Scattering by Complex Dust Structures Authors: Gustafson, B. . S.; Thomas-Osip, J. E.; Waldemarsson, K. W. T.; Xu, Y. -L. Bibcode: 1997DPS....29.2909G Altcode: 1997BAAS...29.1030G We present both experimental data and theoretical solutions to evaluate the scattering of light and other electromagnetic radiation by complex dust morphologies. This includes porous particles made of spherical subparticles to represent aggregated structures that may be relevant models of comet dust and dust in the atmospheres of Titan and Saturn. Solid cubes represent some asteroid dust and dust in some planetary atmospheres. The experimental data were obtained in the microwave analogue to light scattering facility at the Laboratory for Astrophysics, University of Florida. Title: Molecules in Circumstellar Envelopes of Carbon Stars Authors: Larsen, F.; Olofsson, H.; Eriksson, K.; Gustafsson, B. Bibcode: 1997Ap&SS.251..235L Altcode: We have searched for line emission from various transitions of a number of molecules, including CO, HCN, CN, CS and SiO, as well as some of their isotopic variants, towards a sample of 68 bright carbon stars. Part of the data has already been published in Olofsson et al. (1993a,b). The aim of the project is to obtain a better understanding of the carbon star phenomenon and the processes involved. In particular, we would like to obtain reliable mass loss rates and molecular abundances for these objects. This requires careful and detailed modelling, which is currently underway. Our hope is that the study of these bright carbon stars will serve as a guide to the study of higher mass loss rate objects. Some preliminary observational results are presented here. Title: On the history of star formation in the bar of the Large Magellanic Cloud. Authors: Ardeberg, A.; Gustafsson, B.; Linde, P.; Nissen, P. -E. Bibcode: 1997A&A...322L..13A Altcode: With the HST PC and uvby photometry, we investigate evolutionary signatures in a field in the centre of the LMC Bar. Field stars close to the turn off point in the HR diagram are used for a study of ages and evolution of the stellar populations dominating the Bar as well as for determination of the abundance of heavy elements. Including fainter stars, we derive the corresponding luminosity function. Here, we discuss some results obtained from a preliminary version of our data. The quality of our data is high. Two strong stellar populations are obvious. A young component contains approximately 30% of the total number of stars. At least a considerable fraction of this component originated less than 500Myears ago. The older population ranges in age between around 2 and 9Gyears. The abundance of heavy elements is around [Me/H]=-0.6. The tentative luminosity function, down to y=24, resembles in shape that predicted from earlier galactic and LMC data. Parallel to arrival of further HST data, our analysis continues. Title: A stellar endgame - the born-again Sakurai's object. Authors: Asplund, M.; Gustafsson, B.; Lambert, D. L.; Kameswara Rao, N. Bibcode: 1997A&A...321L..17A Altcode: 1997astro.ph..4005A The surface chemical composition of this remarkable star shows that it is hydrogen-deficient, carbon-rich and enriched in the light s-process elements. Spectra taken in May and October 1996 indicate a decrease in the surface hydrogen abundance by 0.7dex in five months along with an increase in the abundances of Li, Sr, Y and Zr. The abundance changes are in agreement with the hypothesis of the star being a rapidly evolving "born-again" AGB star experiencing a final He-shell flash, similar to FGSge. The ^12^C/^13^C ratio in October is very low, also suggesting hydrogen ingestion. By chemical composition, Sakurai's object resembles the R Coronae Borealis (RCrB) stars. Title: KI emission from envelopes around N-type stars. Spectroscopic observations and interpretations. Authors: Gustafsson, B.; Eriksson, K.; Kiselman, D.; Olander, N.; Olofsson, H. Bibcode: 1997A&A...318..535G Altcode: Circumstellar envelopes around three bright N-type stars, R Scl, X TrA, and V Aql have been detected in emission in resonance lines from KI. This radiation, which is most probably scattered photospheric radiation, was first found spectroscopically, but has later been imaged with coronographic and polarimetric techniques. In the present paper, which is the first in a series, the spectroscopic KI observations are discussed. From the observations of the KI 769.9nm emission we find systemic and expansion velocities in fair agreement with those obtained from the CO millimetre lines. We find a decline of the emission with distance from the star, in rough agreement with the assumption of a constant expansion velocity, mass-loss rate and KI abundance. Our mass loss rate estimates from the KI line observations agree rather well with those obtained from CO (ranging from 1/4 to 1/1 of the CO mass loss), which suggests that a considerable fraction of the potassium stays neutral through the envelope. This puts strong upper limits on the photoionizing chromospheric UV emission from the stars. Some indirect indications that the envelopes have inhomogeneous structures, clumps, are discussed. Title: Line-blanketed model atmospheres for R Coronae Borealis stars and hydrogen-deficient carbon stars. Authors: Asplund, M.; Gustafsson, B.; Kiselman, D.; Eriksson, K. Bibcode: 1997A&A...318..521A Altcode: We have constructed line-blanketed model atmospheres for the hydrogen-deficient and carbon-rich R Coronae Borealis (RCrB) stars, as well as for the similar hydrogen-deficient carbon (HdC) stars and the cool extreme helium (EHe) stars. Improved continuum opacities have been used together with realistic line absorption data for atomic and molecular transitions. The observed dereddened fluxes of R CrB are compared with the calculated model fluxes and found to agree best with a model effective temperature of 6900K, while the infrared flux method gives between 6600 and 6900K, depending on the nature of the flux excess in the J and H bands compared to the model fluxes. The excess may correspond to a recently formed dust cloud close to the star, with a typical temperature around 2000K and a dust mass of ~10^-11^Msun_. The agreement for the ultraviolet flux distribution is also very satisfactory as seen from IUE spectra of RCrB. Theoretical broad band photometry is presented and effective temperatures of RCrB and HdC stars estimated. The constructed models show a significantly steeper temperature gradient compared to previously existing models as a result of the line opacity. Due to the cool surface and high abundance of carbon, molecular bands of e.g. C_2_ and CO are visible in the spectra even at as high effective temperatures as 7000K. Furthermore, the high temperatures encountered at depth explain the observed Hei and CII lines for T_eff_ down to ~7000K. In the inner layers (τ_Ross_ > 3) the models show density inversions related to the ionization zone of helium. For certain low gravity models the luminosity exceeds the local Eddington limit and hence gas pressure inversions occur as well, which could be related to the decline events of RCrB stars. Title: The ISO-SWS flux standard stars: synthetic spectra and observations. Authors: der Bliek, N. S.; Morris, P. W.; Vandenbussche, B.; Waters, L. B. F. M.; Zaal, P.; Bell, R. A.; Gustafsson, B.; Eriksson, K.; de Graauw, T. Bibcode: 1997IAUS..189...89D Altcode: 1998IAUS..189...89D The authors present flux-calibrated, synthetic spectra for the calibration stars of the Short Wavelength Spectrometer of the Infrared Space Observatory ISO-SWS. Title: H band spectra of cool dwarfs and giants Authors: van der Bliek, N. S.; Gustafsson, B.; Eriksson, K. Bibcode: 1997IAUS..189P..32V Altcode: 1998IAUS..189P..32V No abstract at ADS Title: Accuracy of synthetic far IR fluxes of stars Authors: van der Bliek, N. S.; Gustafsson, B.; Eriksson, K. Bibcode: 1997IAUS..189P..28V Altcode: 1998IAUS..189P..28V No abstract at ADS Title: South-north and radial traverses through the zodiacal cloud. Authors: Baghul, M.; Grün, E.; Staubach, P.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hamilton, D.; Hanner, M. S.; Horany, M.; Kissel, J.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 1997AdSpR..20.1546B Altcode: No abstract at ADS Title: Comparison Bertween ISO-SWS Observations and Synthetic Spectra of K Giants and M Giants α Boo and β Peg (Invited Paper) Authors: Decin, L.; Cohen, M.; Eriksson, K.; Gustafsson, B.; Huygen, E.; Morris, P.; Plez, B.; Sauval, J.; Vandenbussche, B.; Waelkens, C. Bibcode: 1997ESASP.419..185D Altcode: 1997fiso.work..185D The accurate flux calibration of SWS requires the observation of spectra of stellar templates (Schaeidt et al., 1996). On the other hand, our knowledge of stellar spectra in the broad spectral domain that ISO has opened for the first time is still incomplete, and must be improved with these same ISO data. Clearly, the final flux calibration of SWS data will result from an iterative process, that should benefit to both our understanding of the instrument and of the atmo- spheres of cool stars. We report on the progress of a project which confronts SWS observations of cool stars with state-of-the-art synthetic spectra. The ISO observations enable us to discriminate between various sources of molecular data and put tight constraints on the atmospheric parameters of the stellar templates. Preliminary results suggest that a 2% relative flux accuracy may be attainable in bands 1 and 2 of the SWS range. Title: Large-scale Star Formation in the Centre of the LMC Bar Authors: Ardeberg, A.; Gustafsson, B.; Linde, P.; Nissen, P. -E.; Snel, R. Bibcode: 1997IAUJD...2E..49A Altcode: With the HST PC and uvby photometry, we investigate evolutionary signatures in a field in the centre of the LMC Bar. Field stars close to the turn off point in the HR diagram are used for a study of ages and evolution of the stellar populations dominating the Bar as well as for determination of the abundance of heavy elements. Including fainter stars, we derive the corresponding luminosity function. Here, we discuss some results obtained from a preliminary version of our data. The quality of our data is high. Two strong stellar populations are obvious. A young component contains approximately 30 % of the total number of stars. At least a considerable fraction of this component originated less than 500 Myears ago. The older population ranges in age between around 2 and 9 Gyears. The abundance of heavy elements is around [Me/H] = -0.6. The tentative luminosity function, down to y = 24, resembles in shape that predicted from earlier galactic and LMC data. Parallel to arrival of further HST data, our analysis continues. Title: What do we do when models don't fit? On model atmospheres and real stellar spectra. Authors: Gustafsson, B. Bibcode: 1997IAUS..189..261G Altcode: 1998IAUS..189..261G Developments in the modelling of stellar atmospheres and results from the confrontation between calculated and observed fluxes and spectra are discussed. It is argued that, although impressive advances in the study of O-type, WR and cool star spectra have recently occurred, significant improvements should be possible with already existing methods in the analysis of, e.g., solar-type stars. Title: Area to mass ratio and packing factor from meteor data Authors: Gustafson, B. Å. S.; Adolfsson, L. G. Bibcode: 1997ASIC..487..349G Altcode: 1997cduc.conf..349G No abstract at ADS Title: The Concept of a Facility for Cosmic Dust Research on the Iss Authors: Blum, J.; Henning, Thomas; Cabane, Michel; Fonda, Mark; Giovane, Frank; Gustafson, Bo A. S.; Keller, Horst U.; Markiewicz, Wojciech J.; Nuth, Joseph A.; Rogers, Fred Bibcode: 1996ESASP.385..303B Altcode: 1996ssu..conf..303B No abstract at ADS Title: An Estimation of the Interstellar Contribution to the Zodiacal Thermal Emission Authors: Grogan, K.; Dermott, S. F.; Gustafson, B. A. S. Bibcode: 1996ApJ...472..812G Altcode: Impact data from the Ulysses dust detector at 5 AU from the Sun have been interpreted as a flux of submicron interstellar dust particles arriving from ecliptic longitude 252 deg and ecliptic latitude 2.dg5. By following the motions of these particles under the influence of solar gravity, radiation pressure, and electromagnetic forces, we derive a model of the thermal emission from the resultant particle cloud. Since the distributions of the particles are time variable depending on the solar cycle, calculations are performed for the years 1984 and 1990, corresponding, respectively, to the times of the IRAS and COBE observations. We also illustrate how the distributions vary with particle size (or, at a more basic level beta , the ratio of the radiation pressure to gravitational force) by presenting results for three different particle sizes. Patches of emission from our test cloud reach peak levels of 0.1 MJy sr-1 in the 12 mu m wave band. This represents 10% of the average brightness asymmetry around the sky between the trailing/leading telescope pointing directions seen in the IRAS and COBE data sets. Some of these patches occur at high ecliptic latitudes where the contribution from the Galaxy is negligible and emission from the smooth zodiacal background is low compared to that at low ecliptic latitudes. A strong seasonal variation in the predicted interstellar emission trailing/leading asymmetry is the most obvious signature of the interstellar source, and, in addition, the time variability of the emission will produce different features in the IRAS and COBE data sets and in any subsequent infrared mission. For these reasons, a search of the data for the predicted signatures is certainly justifiable. Title: Dust Measurements During Galileo's Approach to Jupiter and lo Encounter Authors: Grun, E.; Hamilton, D. P.; Riemann, R.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hanner, M. S.; Heck, A.; Horanyi, M.; Kissel, J.; Kruger, H.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R.; Zook, H. A. Bibcode: 1996Sci...274..399G Altcode: About a hundred dust impacts per day were detected during the first week in December 1995 by Galileo during its approach to Jupiter. These impacts were caused by submicrometer-sized particles that were just above the detection limit. After the closest approach to Io on 7 December, impacts of these small particles ceased. This effect is expected for dust grains emitted from Io that exit the field of view of the instrument after the flyby. The impact rate of bigger micrometer-sized dust grains continued to increase toward Jupiter. These dust particles are in orbit about Jupiter or are interplanetary grains that are gravitationally concentrated near Jupiter. Title: Carbon Stars and Nucleosynthesis in Galaxies Authors: Gustafsson, Bengt; Ryde, Nils Bibcode: 1996astro.ph.10261G Altcode: The role of carbon stars in the build-up of chemical elements in galaxies is discussed on the basis of stellar evolution calculations and estimated stellar yields, abundance analyses of AGB stars, galactic-evolution models and abundance trends among solar-type disk stars. We conclude that the AGB stars in general, and carbon stars in particular, probably are main contributors of $s$-elements, that their contributions of flourine and carbon are quite significant, and that possibly their contributions of lithium, $^{13}$C and $^{22}$Ne are of some importance. Also contributions of N, Na and Al are discussed. The major uncertainties that characterize almost any statement concerning these issues are underlined. Title: Investigation of Aggregates as a Model for Titan's Aerosols Using Microwave Analog Experiments and Radiative Transfer Theory Authors: Thomas-Osip, J. E.; Gustafson, B. Å. S. Bibcode: 1996DPS....28.2010T Altcode: 1996BAAS...28.1131T It has been suggested that the aerosols in the atmosphere of Titan have an aggregate morphology (Bar-Nun et al., 1988: West and Smith, 1991). Previous studies were based on formulations of the Discrete Dipole Approximation to calculate the single scattering properties of such aggregates. These studies were limited in the size of the individual spheres and total size of the aggregate. We present microwave to light analog scattering measurements and radiative transfer calculations for aggregates of 250-500 individual spheres near the Raleigh size limit in a plane parallel atmosphere. The advantages of using microwave analog experiments include the possibility of investigating a broad range of particle sizes and morphologies. Title: Polarization of Light by Cometary and Asteroid Dust Models Authors: Gustafson, B. Å S.; Thomas-Osip, J. E.; Waldemarsson, T. K.; Xu, Y. -L. Bibcode: 1996DPS....28.1601G Altcode: 1996BAAS...28Q1120G We have investigated the angular distribution of scattered light by asteroid dust models using the microwave analog to light scattering facility at the Laboratory for Astrophysics at the University of Florida. The main features in the (linear degree of) polarization in the zodiacal light can be reproduced using comet dust models of the "Bird's-Nest" type. We show that the polarization also can be reasonably well reproduced using two asteroid dust models. One model is a compact aggregate of silicate and refractory materials representing interstellar grain material. This model is similar to the "Bird's-Nest" model in composition but the morphology is compacted as opposed to 90% void. A second model represents sharp corners of asteroid fragments and breccia using cubes of refractive index near 1.603 -0.003i. This work is supported by NASA through the Planetary Atmospheres Program Title: Carbon stars with episodic mass loss: observations and models of molecular emission from detached circumstellar shells. Authors: Olofsson, H.; Bergman, P.; Eriksson, K.; Gustafsson, B. Bibcode: 1996A&A...311..587O Altcode: We have obtained detailed CO radio line maps of the circumstellar medium around the bright carbon stars R Scl, U Ant, S Sct, and TT Cyg. They provide direct evidence for the existence of large [radii between 10-70", or (1-5)x10^17^cm], geometrically thin (we estimate that the shell widths are <~10"), over-all spherically symmetric shells of CO line-emitting gas around these stars. The shells expand with velocities in the range 13-20km/s, i.e., their ages lie in the range (1-10)x10^3^years. Less extensive CO observations of the carbon star V644 Sco suggest that also it is surrounded by a detached shell. The expansion velocities of the present mass loss winds, as evidenced by weak CO emission from regions close to the stars, are considerably lower, of the order 5km/s. We conclude that the mass loss characteristics of these, otherwise apparently normal, carbon stars have changed significantly over the last 10^4^years. For such a shell structure, the most reasonable cause is a short period of very intense mass loss (i.e., a mass loss eruption), although an interacting-wind scenario cannot be excluded. The CO brightness distributions are very patchy, suggesting an inhomogeneous circumstellar medium. Using a model where the shell consists of a large number of small, homogeneous clumps, we estimate that the H_2_-masses of the four, spatially resolved shells are all around 0.01Msun_ (for an adopted CO abundance with respect to H_2_ of =~10^-3^), and that in the mass loss eruption -scenario the H_2_-mass loss rates of the stars were =~10^-5^x(10"/{DELTA}R)Msun_/yr during the formation of the shells ({DELTA}R being the unresolved shell width in arc seconds). The present mass loss rates are very low, <~10^-7^Msun_/yr. These results suggest that the four stars have all gone through a type of event that led to a dramatic change in the mass loss characteristics. The adopted model is an initial, relatively crude, attempt to provide a more realistic base for the interpretation of line emission from a circumstellar medium in which, in general, the physical conditions are very likely quite inhomogeneous. It is the accidental overlap along the line-of-sight and in velocity space of the many small clumps that in the model produces a clumpy appearance of the brightness distribution, at the larger scale set by the observational resolution, that resembles the observed ones. In the mass loss eruption -scenario the estimated life time of a CO line-emitting shell of the type discussed in this paper is =~10^4^years, and it is determined by the photodissociation of the CO molecules. Only shells younger than =~10^3^years are expected to be observable in molecular radio lines other than those of CO. There is a period after formation when such shells should be characterized by very anomalous line intensity ratios. For instance, in our model the line intensity ratio between the photodissociation product CN and the parent molecule HCN increases drastically on a time scale of hundreds of years as the shell recedes from the star. We suggest that the shell around R Scl is in this phase, since this is the only object, among the five observed, in which we have clearly detected also lines of HCN and CN, albeit with anomalous line intensity ratios. Title: Constraints from Galileo observations on the origin of jovian dust streams Authors: Grün, E.; Baguhl, M.; Hamilton, D. P.; Riemann, R.; Zook, H. A.; Dermott, S.; Fechtig, H.; Gustafson, B. A.; Hanner, M. S.; Horányi, M.; Khurana, K. K.; Kissel, J.; Kivelson, M.; Lindblad, B. A.; Linkert, D.; Linkert, G.; Mann, I.; McDonnell, J. A. M.; Morfill, G. E.; Polanskey, C.; Schwehm, G.; Srama, R. Bibcode: 1996Natur.381..395G Altcode: THE Ulysses spacecraft detected streams of sub-micrometre-sized dust particles as it approached Jupiter in 19921,2. Although interplanetary space was known to contain dust, the presence of discrete streams was completely unexpected. The directions from which the dust grains struck the spacecraft strongly suggested that the source lay somewhere within the Jupiter system. Three origins were proposed, the comet Shoemaker-Levy 9 (ref. 3), Jupiter's gossamer ring4, and the volcanoes on Io5, but there was no definitive evidence for or against any of the options. Here we report the detection by the Galileo spacecraft of even more intense dust streams-including three intense dust storms of month-long duration, with impact rates up to 10 times higher than those observed by Ulysses. Our analysis of the data confirms that the dust streams originate near Jupiter; we are able to rule out a cometary origin, but cannot yet determine conclusively whether the dust comes from Io or the ring. Title: Stellar far-IR fluxes: how accurate are model predictions? Authors: van der Bliek, N. S.; Gustafsson, B.; Eriksson, K. Bibcode: 1996A&A...309..849V Altcode: We present the results of an analysis of the accuracy of predicted far infrared (FIR) fluxes of stars. Sources of errors are a) the input parameters for the model atmospheres; b) assumptions in the modelling, resulting in errors in the structure of the model atmospheres; c) the adopted IR continuous opacity, dominated by the H^-^_ff_ opacity; d) the possible presence of circumstellar (CS) dust. Stellar effective temperatures are typically determined with an accuracy of about 100K. This leads to an uncertainty in the predicted far infrared (FIR) flux of 1 to 4%, depending on the spectral type. Errors in the other two fundamental parameters of a star, the surface gravity and the metallicity, have a minor effect on the prediction of stellar FIR fluxes, less than 1%. The various assumptions made in the modelling result in errors in the temperature structure T(τ) of model atmospheres. By using the depth and shape of spectral lines, T(τ) in the outer layers of the atmosphere, where the lines are formed, can be pinned down to about 100K, resulting in uncertainties of about 1 to 2% in the FIR. Errors in the H^-^_ff_ opacity are small and as a result uncertainties in the FIR fluxes due to the continuous opacity are less than 0.1%. CS dust can have a large impact on the IR fluxes. We find that the uncertainties due to the possible presence of CS dust can be more than an order of magnitude larger than the uncertainties resulting from modelling the stellar atmosphere. Unfortunately with the present day accuracies of IR data no further constraints can be set to limit these uncertainties. Title: Microwave analog to light scattering measurements: a modern implementation of a proven method to achieve precise control. Authors: Gustafson, B. Å. S. Bibcode: 1996JQSRT..55..663G Altcode: The experimental determination of scattered electromagnetic radiation from a known target illuminated by a known source remains an essential tool to test new scattering theories and to investigate the scattering by particles for which a theory has not yet been devised. This article describes a modern broad-band microwave scattering facility capable of determining the elements of the scattering matrix from 0 to 168° scattering angle under automated control. The laboratory measurements can cover the size range from near the Rayleigh limit to geometric optics. Both phase and intensity are routinely measured at 85-501 discrete wavelengths from 2.7 to 4 mm, which allows the derivation of all elements in the scattering matrix. The unwanted background radiation can be removed through vector subtraction and the result verified using the technique of "time-gating" based on inverse Fourier transformation and time domain analysis. Measurements are shown to be repeatable and accurate. This is primarily due to the use of a "clean" mechanical and electronic design in combination with high mechanical and thermal stability. Title: Radiation Pressure Correction to Meteor Orbits Authors: Gustafson, Bo ». S.; Adolfsson, Lars G. Bibcode: 1996EM&P...72..327G Altcode: We present a method to calculate the radiation pressure force to gravity ratio on meteoroids from their atmospheric flight. Radiation pressure corrections to meteor orbits are negligible for fireballs; of the order of or less than the measurement errors (≈ 1%) for photographic meteors; of the order of and in some cases substantially larger than the measurement errors (≈ 10%) for radar meteors. Title: Are the declines of R Coronae Borealis stars caused by super- Eddington luminosities? Authors: Asplund, M.; Gustafsson, B. Bibcode: 1996ASPC...96...39A Altcode: 1996hds..conf...39A No abstract at ADS Title: The Martian Atmosphere as a Meteoroid Detector Authors: Adolfsson, Lars G.; Gustafson, Bo Å. S.; Murray, Carl D. Bibcode: 1996Icar..119..144A Altcode: We investigate the plausibility of detecting meteors from the surface of Mars. We estimate the flux of high-speed photographic meteoroids at the orbit of Mars to be ∼50% that at Earth. Because the atmospheric densities of the Earth and Mars are comparable at a height of 120 km, close to where meteor ablation occurs on Earth, we also expect martian meteors to ablate at heights similar to those on Earth. By numerical integration we have modeled the intensity of an “asteroidal” particle and a “cometary” particle as they enter the atmosphere, using particle masses in the range 10-8to 102g. We conclude that high-speed (≳30 km sec-1) meteoroids will have the same magnitude in both atmospheres; lower speed meteoroids will be dimmer in Mars' atmosphere. We suggest that future missions to Mars should include meteor observation programs which would permit direct measurements of the meteoroid complex in another region of the solar system as well as providing important information on the structure and time variability of the martian atmosphere. Title: A Complete and Efficient Multisphere Scattering Theory for Modeling the Optical Properties of Interplanetary Dust Authors: Xu, Y. -L.; Gustafson, B. A. S. Bibcode: 1996ASPC..104..419X Altcode: 1996IAUCo.150..419X; 1996pcdi.conf..419X No abstract at ADS Title: Physics, chemistry, and dynamics of interplanetary dust Authors: Gustafson, Bo A. S.; Hanner, Martha S. Bibcode: 1996ASPC..104.....G Altcode: 1996pcdi.conf.....G; 1996IAUCo.150.....G No abstract at ADS Title: Search for the Signature of Interstellar Dust in the COBE Data Authors: Grogan, K.; Dermott, S. F.; Gustafson, B. A. S.; Jayaraman, S.; Xu, Y. L.; Hamilton, D. Bibcode: 1996ASPC..104..325G Altcode: 1996pcdi.conf..325G; 1996IAUCo.150..325G No abstract at ADS Title: An Optical Instrument to Characterize Individual Dust Particles Authors: Giovane, F.; Gustafson, B. A. S.; Lamy, Ph. L. Bibcode: 1996ASPC..104..247G Altcode: 1996pcdi.conf..247G; 1996IAUCo.150..247G No abstract at ADS Title: The Metal-Rich Disk Population Authors: Feltzing, S.; Gustafsson, B. Bibcode: 1996IAUS..171..372F Altcode: No abstract at ADS Title: Sources of Interplanetary Dust Authors: Dermott, S. F.; Grogan, K.; Gustafson, B. A. S.; Jayaraman, S.; Kortenkamp, S. J.; Xu, Y. L. Bibcode: 1996ASPC..104..143D Altcode: 1996IAUCo.150..143D; 1996pcdi.conf..143D No abstract at ADS Title: Interferometric molecular line observations of the circumstellar envelope(s) around U Camelopardalis. Authors: Lindqvist, M.; Lucas, R.; Olofsson, H.; Omont, A.; Eriksson, K.; Gustafsson, B. Bibcode: 1996A&A...305L..57L Altcode: We have observed the circumstellar envelope of the carbon star U Cam in the HCN(J=1->0) and CN(N=1->0) lines using the IRAM Plateau de Bure interferometer. There is evidence of a two-envelope structure: an outer extended envelope, possibly a shell, with a radius of ~7x10^16^cm, that expands with a velocity of ~25km/s, surrounding an inner envelope with a radius of ~6x10^15^cm and an expansion velocity of only ~13km/s. Mass loss rate estimates based on these data alone are uncertain, but they suggest that the mass loss rate during the formation of the outer envelope was higher than during the present mass loss epoch. Thus, we have evidence for a significant variation in the mass loss characteristics of U Cam within the last 10^3^years. Title: Model atmospheres of cool hydrogen-deficient carbon stars Authors: Gustafsson, B.; Asplund, M. Bibcode: 1996ASPC...96...27G Altcode: 1996hds..conf...27G No abstract at ADS Title: Dust Flux Analyser experiment for the Rosetta mission Authors: Leese, M. R.; McDonnell, J. A. M.; Green, S. F.; Busoletti, E.; Clark, B. C.; Colangeli, L.; Crifo, J. F.; Eberhardt, P.; Giovane, F.; Grün, E.; Gustafson, B.; Hughes, D. W.; Jackson, D.; Lamy, P.; Langevin, Y.; Mann, I.; McKenna-Lawlor, S.; Tanner, W. G.; Weissman, P. R.; Zarnecki, J. C. Bibcode: 1996AdSpR..17l.137L Altcode: 1996AdSpR..17..137L We present the description of a design for a proposed Dust Flux Analyser for the Rosetta cometary mission. A concept first developed for the NASA/ESA Tempel II Rendezvous and Halley Intercept Mission /1/, the instrument is able to measure dust particle parameters and fluxes over a velocity range typical of emission from cometary surfaces. It would be mounted on the Rosetta Orbiter and would measure the variation in flux rate throughout all mission phases at the comet. The instrument would measure particle flux, velocity, momentum and density, shape and scattering properties. Title: Interstellar Grain Flow Through the Solar Wind Cavity around 1992 Authors: Gustafson, B. A. S.; Lederer, S. M. Bibcode: 1996ASPC..104...35G Altcode: 1996IAUCo.150...35G; 1996pcdi.conf...35G No abstract at ADS Title: Optical Properties of Dust from Laboratory Scattering Measurements Authors: Gustafson, B. A. S. Bibcode: 1996ASPC..104..401G Altcode: 1996pcdi.conf..401G; 1996IAUCo.150..401G No abstract at ADS Title: Dynamic and Probabilistic Relation Between Meteoroids and Their Parent Bodies Authors: Adolfsson, L. G.; Gustafson, B. A. S. Bibcode: 1996ASPC..104..133A Altcode: 1996pcdi.conf..133A; 1996IAUCo.150..133A No abstract at ADS Title: Concepts for Dust Velocity Measurements on a Cometary Orbiter Authors: Perruchot, S.; Lamy, Ph. L.; Giovane, F.; Gustafson, B. A. S. Bibcode: 1996ASPC..104..255P Altcode: 1996IAUCo.150..255P; 1996pcdi.conf..255P No abstract at ADS Title: Area to mass ratio and packing factor from meteor data. Authors: Gustafson, B. Å. S.; Adolfsson, L. G. Bibcode: 1996cduc.conf..349G Altcode: The authors show that the bulk density of meteoroids during atmospheric flight can be accurately estimated with the uncertainty in the deceleration of the meteoroid and the efficiency factor for drag as the major sources of error. They reinterpret the difference in photometric mass, which they believe is close to the true mass, and the dynamical mass in terms of porous meteoroid material. The bulk density of 0.26 g cm-3 prior to atmospheric entry could be reliably estimated for one meteoroid. The corresponding packing factor is 0.12, i.e., 88% of the meteoroid's volume is likely to be cavities. Title: Atmospheres from Within Authors: Morgan, Thomas; Abshire, James; Clancy, Todd; Fry, Ghee; Gustafson, Bo; Hecht, Michael; Kostiuk, Theodor; Rall, Jonathan; Reuter, Dennis; Sheldon, Robert Bibcode: 1996psi..work...51M Altcode: In this review of atmospheric investigations from planetary surfaces, a wide variety of measurement and instrument techniques relevant to atmospheric studies from future planetary lander missions are discussed. The diversity of planetary surface environments within the solar system precludes complete or highly specific coverage, but lander investigations for Mars and cometary missions are presented as specific cases that represent the broad range of atmospheric-surface boundaries and that also correspond to high priority goals for future national and international lander missions. Title: The origin and dynamics of the interplanetary dust cloud. Authors: Dermott, S. F.; Jayaraman, S.; Xu, Y. L.; Grogan, K.; Gustafson, B. A. S. Bibcode: 1996AIPC..348...25D Altcode: Obtaining a model of the zodiacal cloud to predict the flux in a given waveband, in a given direction, at a given time of the year, to one per cent of the peak brightness, or better, will require a detailed understanding of the dynamics of the particles that originate from each of the various sources. Each component of the cloud (asteroidal, cometary and interstellar) gives rise to characteristic features and by resolving the cloud into its various components and determining the amplitudes of the signals associated with each, one is able to determine the fractional composition of the cloud. One can expect to have a good understanding of the dynamics of the asteroidal particles that give rise to the solar system dust bands and get trapped in the Earth's circumsolar resonant ring. Interpretations of the dust band observations and of the cloud's trailing/leading asymmetry indicate that about one third of the particles in the cloud are asteroidal, implying that about two thirds of the particles originate from comets. Some progress has been made with understanding the dynamics of cometary particles, but this remains a challenging problem. In this paper, to illustrate the quality of the DIRBE data and to show how the observed structure of the cloud is amenable to a dynamical interpretation, the authors analyse the asymmetry of the cloud observed in the DIRBE 12 μm waveband. Title: Chemical Evolution and History of Star Formation in the Large Magellanic Cloud Authors: Gustafsson, Bengt Bibcode: 1995hst..prop.6102G Altcode: Large scale processes controlling star formation and nucleosynthesis are fundamental but poorly understood. This is especially true for external galaxies. A detailed study of individual main sequence stars in the LMC Bar is proposed. The LMC is close enough to allow this, has considerable spread in stellar ages and a structure permitting identification of stellar populations and their structural features. The Bar presumably plays a dominant role in the chemical and dynamical evolution of the galaxy. Our knowledge is, at best, based on educated guesses. Still, the major population of the Bar is quite old, and many member stars are relatively evolved. The Bar seems to contain stars similar to those of Intermediate to Extreme Pop II in the Galaxy. We want to study the history of star formation, chemical evolution and initial mass function of the population dominating the Bar. We will use field stars close to the turn off point in the HR diagram. From earlier studies, we know that 250-500 such stars are available for uvby photometry in the PC field. We aim at an accuracy of 0.1 -0.2 dex in Me/H and 25% or better in relative ages. This requires an accuracy of about 0.02 mag in the uvby indices, which can be reached, taking into account errors in calibration, flat fielding, guiding and problems due to crowding. For a study of the luminosity function fainter stars will be included as well. Calibration fields are available in Omega Cen and M 67. Title: Search for the Signature of Interstellar Dust in the COBE Data Authors: Grogan, K.; Dermott, S. F.; Gustafson, B. A. S.; Jayaraman, S.; Hamilton, D. Bibcode: 1995DPS....27.4006G Altcode: 1995BAAS...27.1164G No abstract at ADS Title: Recent Advances on Light Scattering Models of Interplanetary Dust Authors: Xu, Y. -L.; Dermott, S. F.; Gustafson, B. Å. S. Bibcode: 1995DPS....27.4007X Altcode: 1995BAAS...27.1164X No abstract at ADS Title: Outer Layers of a Carbon Star: The View from the Hubble Space Telescope Authors: Johnson, Hollis R.; Ensman, Lisa M.; Alexander, David R.; Avrett, Eugene H.; Brown, Alexander; Carpenter, Kenneth G.; Eriksson, Kjell; Gustafsson, Bengt; Jorgensen, Uffe G.; Judge, Philip D.; Linsky, Jeffrey L.; Luttermoser, Donald G.; Querci, Francois; Querci, Monique; Robinson, Richard D.; Wing, Robert F. Bibcode: 1995ApJ...443..281J Altcode: To advance our understanding of the relationship between stellar chromospheres and mass loss, which is a common property of carbon stars and other asymptotic giant branch stars, we have obtained ultraviolet spectra of the nearby N-type carbon star UU Aur using the Hubble Space Telescope (HST). In this paper we describe the HST observations, identify spectral features in both absorption and emission, and attempt to infer the velocity field in the chromosphere, upper troposphere, and circumstellar envelope from spectral line shifts. A mechanism for producing fluoresced emission to explain a previously unobserved emission line is proposed. Some related ground-based observations are also described. Title: Interferometric Observations of HCN and CN towards Carbon Stars Authors: Lindqvist, M.; Lucas, R.; Olofsson, H.; Omont, A.; Eriksson, K.; Gustafsson, B. Bibcode: 1995Ap&SS.224..501L Altcode: Using the IRAM interferometer we have observed four carbon stars (U Cam, CIT6, Y CVn, IRC+40540) in the HCN(J=1 → 0) and CN(N=1 → 0) lines. Here we present some results for CIT6 and U Cam. Title: High-Precision Astrometry and the Modelling of Stellar Spectra Authors: Gustafsson, B. Bibcode: 1995IAUS..166..143G Altcode: No abstract at ADS Title: Opacity incompleteness and atmospheres of cool stars Authors: Gustafsson, B. Bibcode: 1995HiA....10..579G Altcode: No abstract at ADS Title: Opacity Incompleteness and Atmospheres of Cool Stars Authors: Gustafsson, B. Bibcode: 1995ASPC...78..347G Altcode: 1995aapn.conf..347G No abstract at ADS Title: Do We Need the VLT to Study Nearby Stellar Populations? Authors: Gustafsson, B. Bibcode: 1995svlt.conf...65G Altcode: No abstract at ADS Title: Line asymmetries in the metal-poor star HD 140283 Authors: Allende Prieto, C.; García López, R. J.; Lambert, D. L.; Gustafsson, B. Bibcode: 1995IAUS..176P.107A Altcode: No abstract at ADS Title: Star Formation and System Calibration Authors: Linde, P.; Ardeberg, A.; Gustafsson, B.; Nissen, P. E. Bibcode: 1995chst.conf..334L Altcode: No abstract at ADS Title: Models of late-type stellar photospheres Authors: Gustafsson, Bengt; Jorgensen, Uffe Grae Bibcode: 1994A&ARv...6...19G Altcode: In this review we discuss recent work and progress in the modelling of photospheres of stars of spectral types F and later. Special emphasis is laid on advances as regards the consideration of atomic and molecular blanketing, non-LTE and convection and other dynamic processes. In a special chapter we discuss the possibilities of semi-empirical modelling of late-type photospheres. In the conclusions we find that much important work remains in this field, but that a considerable part of this work may in fact be carried out in a near future. Title: Boron in the extreme Population II star HD 140283 and the production of light elements in the Early Galaxy Authors: Edvardsson, B.; Gustafsson, B.; Johansson, S. G.; Kiselman, D.; Lambert, D. L.; Nissen, P. E.; Gilmore, G. Bibcode: 1994A&A...290..176E Altcode: 1994astro.ph..3002E Using observations of the 2496.7A Bi line with the HST GHRS at a nominal resolving power of 90,000, we have found the abundance of boron of HD140283 to be logɛ_B_(=12+log(N_B_/N_H_))=0.34+/-0.20. This result is found when a significant non-LTE effect in the formation of the Bi line is taken into account. The resulting N_B_/N_Be_ ratio is about 17 (in the range 9-34), which is in very good agreement with what is expected from spallation by cosmic rays. We conclude that this origin of Be and B in the Early Galaxy is the most probable of recently suggested formation mechanisms. Title: Effect of meteoroid rotation on atmospheric entry heating and meteor beginning height Authors: Adolfsson, L. G.; Gustafson, B. A. S. Bibcode: 1994P&SS...42..593A Altcode: The begining of height of a meteor yaries by ∼ 10 km depending on the rotation state of a spherical meteoroid as long as the body sustains a temperature gradient. Such gradients build up in friable stony metoroids larger than ∼ 0.1 cm and in iron meteoroids that are ∼ 1 cm or larger. The height where 100 μm or smaller zodiacal dust particles ablate is nearly independent of rotation. Stony particles in the 100 μm size range ablate near 120 km while both larger and smaller interoids penetrate deeper. All calculations were made with a nominal speed of 30 km s -1 and a zenithal distance equal to zr = 0°. Larger meteoroids cool their surface by conduction to the interior while smaller meteoroids decelerate significantly due to their large surface area to mass ratio so that the surface recieves a lower energy flux. Some micro-meteoroids smaller than ∼ 10 μm may escape ablation altogether at the nominal velocity. The effect of rotation on particle temperature during atmospheric flight is significant on meteoroids larger than 0.1 cm but may be negligible on micro-meteorites that are typically 10-50 μm in diameter. Title: A circumsolar ring of asteroidal dust in resonant lock with the Earth Authors: Dermott, Stanley F.; Jayaraman, Sumita; Xu, Y. L.; Gustafson, B. Å. S.; Liou, J. C. Bibcode: 1994Natur.369..719D Altcode: Numerical simulations of the orbital evolution of asteroidal dust particles show that the Earth is embedded in a circumsolar ring of asteroidal dust, and has a cloud of dust permanently in its wake. This could account for the asymmetry of the zodiacal cloud observed by the Infrared Astronomical Satellite (IRAS). The resonant trapping and subsequent release of dust particles by the ring may provide a mechanism by which carbonaceous material is transported from the asteroid belt to the Earth. Title: Interstellar dust in the heliosphere Authors: Gruen, E.; Gustafson, B.; Mann, I.; Baguhl, M.; Morfill, G. E.; Staubach, P.; Taylor, A.; Zook, H. A. Bibcode: 1994A&A...286..915G Altcode: A flow of μm-sized interstellar grains has been identified with the Ulysses dust detector in the outer solar system at about 5 AU from the Sun. The observed flux is 1.5x10^-4^m^-2^/s of particles of mean mass 3x10^-13^g, which corresponds to a mass flux of 5x10^-17^g/m^2^/s. The particles on hyperbolic trajectories have radiants which are compatible with the flow of interstellar gas, although some velocity dispersion occurs. The grains are on average a factor 30 more massive than the classical interstellar grains which cause stellar extinction. However, these smaller grains have not been detected by Ulysses. It is demonstrated that radiation pressure and interaction of the charged grains with the interplanetary magnetic field prevent these small grains from penetrating down to the distance of Ulysses. The spatial density of interstellar grains is compatible with zodiacal light observations. Some consequences arising from the existence of big grains in the interstellar medium are discussed. Title: A New Analog to Light Scattering Laboratory at the University of Florida Authors: Gustafson, B. Å. S. Bibcode: 1994DPS....26.0609G Altcode: 1994BAAS...26R1089G No abstract at ADS Title: Chemical composition and atmospheric parameters of metal-poor halo stars Authors: Nissen, P. E.; Gustafsson, B.; Edvardsson, B.; Gilmore, G. Bibcode: 1994A&A...285..440N Altcode: The abundance of oxygen in 9 metal-poor stars is derived from high resolution observations of OH lines in the spectral region 3138-3155 A. The same spectra were previously used to determine the beryllium abundance (Gilmore et al. 1992). In addition, Mg, Ca, Ti, Cr, and Fe abundances are derived from accurate equivalent widths of weak atomic absorption lines in the 5100-6100 A spectral region. Atmospheric parameters, T_eff_ and g, are determined from the Stroemgren photometric indices b-y and c_1_. New accurate oscillator strengths for the FeI and FeII lines allow an important check of these parameters as well as the assumption of LTE; the FeI excitation balance is consistent with the photometric temperatures, whereas the FeII/FeI ionization balance suggests an over-ionization of iron amounting to about 0.15 dex with respect to LTE. The derived abundance ratios between the α-elements and Fe are nearly constant in the metallicity range -3.2 <~[Fe/H]<~-1.8. Any possible scatter of Mg/Fe, Ca/Fe and Ti/Fe in the galactic halo is less than 0.06 dex and an upper limit for the scatter of O/Fe is 0.15 dex. This suggests that the IMF was similar in different regions of the inner halo and that the mixing of nucleosynthesis products was very efficient in galactic regions of typically globular cluster masses. Title: The Production of Beryllium in the Early Galaxy Authors: Feltzing, Sofia; Gustafsson, Bengt Bibcode: 1994ApJ...423...68F Altcode: The formation of beryllium in the early Galaxy is discussed. It is shown that if spallation occurs predominantly in regions rich in heavy elements, i.e., close to supernovae, the linear relation recently obtained by Gilmore et al. (1992) between beryllium and oxygen abundances for Population II stars may be reproduced. Estimates of relevant timescales for mixing show that the decisive factor, the ratio of the timescale of cosmic-ray diffusion out of the locally enriched regions to the decay time of cosmic rays in the Galaxy as a whole, admits this scenario. Although energetically possible, it requires, however, very high local cosmic-ray fluxes (greater than or equal to 105/sq cm/s), which predicts gamma-ray fluxes above those observed from supernova remnants and the Galaxy. We therefore consider other models, such as those given by Duncan et al. (1992) or Prantzos et al. (1993), more probable. Title: Modern Sources of Dust in the Solar System Authors: Dermott, Stanley F.; Durda, D. D.; Gustafson, B. A. S.; Jayaraman, S.; Liou, J. -C.; Xu, Y. -L. Bibcode: 1994aidp.work...17D Altcode: 1994LPITR9402...17D The observed size-frequency distributions of the main-belt and family asteroids and the results of an analysis of the IRAS data on the zodiacal background and the solar system dustbands were used to estimate the extent of the contribution of asteroidal dust to the zodiacal cloud. It is concluded that the total asteroidal contribution to the zodiacal signal is probably 40% of the total flux. Thus, some 60% of the flux probably derives from a source other than main-belt asteroids. Title: Zodiacal Dust Bands Authors: Dermoti, S. F.; Durda, D. D.; Gustafson, B. A. S.; Jayaraman, S.; Liou, J. C.; Xu, Y. L. Bibcode: 1994IAUS..160..127D Altcode: No abstract at ADS Title: Physics of Zodiacal Dust Authors: Gustafson, B. A. S. Bibcode: 1994AREPS..22..553G Altcode: No abstract at ADS Title: The processes of nucleosynthesis and chemical evolution as observed in stars: three examples Authors: Gustafsson, B. Bibcode: 1993JPhGS..19....1G Altcode: No abstract at ADS Title: The processes of nucleosynthesis and chemical evolution as observed in stars: three examples Authors: Gustafsson, B. Bibcode: 1993JPhG...19S...1G Altcode: No abstract at ADS Title: The chemical evolution of the galactic disk II. Observational data. Authors: Edvardsson, B.; Andersen, J.; Gustafsson, B.; Lambert, D. L.; Nissen, P. E.; Tomkin, J. Bibcode: 1993A&AS..102..603E Altcode: We recently discussed the chemical evolution of the galactic disk based on the detailed analysis of 189 F and early G disk dwarfs (Edvardsson et al. 1993). Here we describe the related solar observations, compare equivalent widths of programme stars observed both from ESO and McDonald observatories and tabulate equivalent widths. Title: The Chemical Evolution of the Galactic Disk - Part One - Analysis and Results Authors: Edvardsson, B.; Andersen, J.; Gustafsson, B.; Lambert, D. L.; Nissen, P. E.; Tomkin, J. Bibcode: 1993A&A...275..101E Altcode: 2009A&A...500..391E No abstract at ADS Title: Scattering by aggregates with and without an absorbing mantle: microwave analog experiments Authors: Zerull, R. H.; Gustafson, B. A. S.; Schulz, K.; Thiele-Corbach, E. Bibcode: 1993ApOpt..32.4088Z Altcode: We present angular scattering functions for loosely packed aggregates of 250 and 500 identical spheres near the Rayleigh size limit before and after the application of successive layers of an absorbing mantle. All measurements were obtained by using the microwave analog technique. Gross features of the scattering by aggregates without a mantle can be interpreted in terms of coherent scattering from the unit spheres acting independently of each other. The largest deviations from this approximation occur after the first minimum in forward scattering and extend to a scattering angle of 60 or 80 deg for our models. This intermediate range is also where the largest differences occur in the scattering from one aggregate to another. The angular extent of the range is largest for aggregates with the smallest dimensions. The scattering function is usually flat in the backscattering hemisphere and has little or no backscattering increase. The coherent scattering approximation breaks down when the aggregates are coated, and an equivalent spheres approximation becomes a better representation. The maximum degree of polarization near a scattering angle of 90 deg first decreases and then increases again as the mantle grows thicker. Title: A Study of Circumstellar Envelopes around Bright Carbon Stars. I. Structure, Kinematics, and Mass-Loss Rate Authors: Olofsson, H.; Eriksson, K.; Gustafsson, B.; Carlstrom, U. Bibcode: 1993ApJS...87..267O Altcode: Results are presented of a survey of circumstellar CO emission on a sample of bright carbon stars, which is relatively complete out to about 900 pc from the sun. A total of 68 detections were made. All objects within 600 pc of the sun were detected. It is suggested that the large majority of all carbon stars have circumstellar envelopes. The CO-emitting parts of these envelopes have angular sizes less than about 15 arcsec. The median gas expansion velocity is 12.5 km/s, and the expansion velocities for the majority of the objects fall in the range 9-15 km/s. The median mass-loss rate is 1.5 x 10 exp -7 solar mass/yr, and the mass loss rate for the majority of stars lies within the narrow range (0.8-2.5) x 10 exp -7 solar mass/yr. Circumstellar and photospheric HCN, CN, and CS abundances are estimated and compared for a sample for bright carbon stars. The chemistry in the envelope around R Scl is determined. Title: A Study of Circumstellar Envelopes around Bright Carbon Stars. II. Molecular Abundances Authors: Olofsson, H.; Eriksson, K.; Gustafsson, B.; Carlstroem, U. Bibcode: 1993ApJS...87..305O Altcode: We have estimated and compared circumstellar and photospheric HCN, CN, and CS abundances for a sample of bright carbon stars. The circumstellar HCN and CS abundances roughly correlate with the photospheric ones, but the former appear to be systematically overestimated by a factor of 5-10. Although we cannot exclude the presence of a circumstellar chemistry that efficiently produces HCN and CS in the inner parts of these relatively hot circumstellar envelopes, we attribute this difference between photospheric and circumstellar abundances to errors in the circumstellar envelope model used. In particular, for the low mass-loss rate objects a systematic underestimate of the mass-loss rate may be suspected. In addition to this general trend, stars that are in some sense peculiar also show circumstellar abundances that deviate significantly from the expected. There is evidence for the presence of maser features in the HCN (J = 1-0) emission toward some of the stars. The estimated circumstellar CN abundances suggest that this species is a photodissociation product of HCN. A search for circumstellar HNC, SiS, and HC3N shows that molecular emission from species other than CO, HCN, CN, and CS is very weak in these low mass-loss rate objects. An attempt has been made to determine the chemistry in the (probably detached) envelope around R Scl. The data suggest a carbon-rich chemistry. Finally, it is shown that the circumstellar 12CO/13CO and H12CN/H13CN intensity ratios roughly correlate with the photospheric 12C/13C isotope ratios for a small number of low mass-loss rate objects, although the former ratios are systematically lower than the latter by a factor of about 2. Title: A Multi-Wavelength Study of the Potentially Meteorite-producing Comet P/Wilson-Harrington (4015 1979VA) Authors: Campins, H.; Osip, D.; Gustafson, B. S. Å.; Rieke, G.; Rieke, M.; Larson, S.; Schleicher, D. Bibcode: 1993DPS....25.1007C Altcode: 1993BAAS...25R1057C No abstract at ADS Title: VizieR Online Data Catalog: Chemical evolution of the galactic disk II. (Edvardsson+ 1993) Authors: Edvardsson, B.; Andersen, J.; Gustafsson, B.; Lambert, D. L.; Nissen, P. E.; Tomkin, J. Bibcode: 1993yCat..41020603E Altcode: (1993A&A...275..101E, see catalog <J/A+A/275/101>) from observations at ESO and McDonald observatories are compared. (4 data files). Title: VizieR Online Data Catalog: Chemical evolution of the galactic disk I. (Edvardsson+ 1993) Authors: Edvardsson, B.; Andersen, J.; Gustafsson, B.; Lambert, D. L.; Nissen, P. E.; Tomkin, J. Bibcode: 1993yCat..32750101E Altcode: From high resolution, high S/N spectroscopic observations of carefully selected northern and southern stars, abundances of O, Na, Mg, Al, Si, Ca, Ti, Fe, Ni, Y, Zr, Ba and Nd, as well as photometric ages, are derived for 189 nearby field F and G stars.

(2 data files). Title: The observed chemical evolution of the Galactic disk. Authors: Edvardsson, B.; Gustafsson, B.; Andersen, J.; Nissen, P. E.; Lambert, D. L.; Tomkin, J. Bibcode: 1993AGAb....8..105E Altcode: 1993AGAb....8..105. No abstract at ADS Title: A Multi-Wavelength Study of the Potentially Meteorite-producing Comet P/Wilson-Harrington (4015 1979VA) Authors: Campins, H.; Osip, D.; Gustafson, B. Å. S.; Rieke, G.; Rieke, M.; Larson, S.; Schleicher, D. Bibcode: 1993LPICo.810...54C Altcode: No abstract at ADS Title: Is superficial knowledge about stellar surfaces sufficient? Authors: Gustafsson, Bengt Bibcode: 1993ASPC...40..122G Altcode: 1993IAUCo.137..122G; 1993ist..proc..122G The significance of a detailed knowledge of the atmosphere of a star for a proper understanding of its interior is illustrated and discussed. It is concluded that significant progress in the understanding of stellar atmospheres is needed in order to match methods, discoveries and needs in the study of stellar internal structure and evolution. (orig.) Title: Models of the Zodiacal Cloud and the Solar System Dust Bands for a Spectrum of Wavebands Authors: Xu, Y. -L.; Dermott, S. F.; Gustafson, B. Å. S.; Liou, J. C. Bibcode: 1993LPICo.810..317X Altcode: No abstract at ADS Title: Origin of the IRAS dustbands (Invited) Authors: Dermott, S. F.; Durda, D. D.; Gomes, R. S.; Gustafson, B. A. S.; Jayaraman, S.; Liou, J. C.; Nicholson, P. D.; Xu, Y. L. Bibcode: 1993mtpb.conf..357D Altcode: No abstract at ADS Title: Dependence of Meteor Beginning Heights on Meteoroid Rotation Authors: Adolfsson, L. G.; Gustafson, B. Å. S. Bibcode: 1993LPICo.810....1A Altcode: No abstract at ADS Title: Optical and Physical Properties of Comet Dust Models; Numerical and Laboratory Results Authors: Gustafson, B. Å. S.; Palm, T.; Andersson, M. W.; Adolfsson, L. G.; Xu, Y. L.; Zerull, R. H. Bibcode: 1993LPICo.810..125G Altcode: No abstract at ADS Title: Meteoroid Material and Beginning Heights Within Meteor Streams Authors: Adolfsson, L. G.; Gustafson, B. Å. S. Bibcode: 1993LPICo.810....2A Altcode: No abstract at ADS Title: The processes of nucleosynthesis and chemical evolution as observed in stars: three examples Authors: Gustafsson, B. Bibcode: 1993nuco.conf....3G Altcode: No abstract at ADS Title: Tools for the interpretation of stellar data Chemical composition as a parameter in individual stars Authors: Gustafsson, B. Bibcode: 1993fces.conf....3G Altcode: No abstract at ADS Title: The production of light elements in the early galaxy Authors: Feltzing, S.; Gustafsson, B. Bibcode: 1993paas.conf..550F Altcode: No abstract at ADS Title: Standard stars for the Infrared Space Observatory, ISO. Authors: van der Bliek, N. S.; Bouchet, P.; Habing, H. J.; Jourdain de Muizon, M.; Blackwell, D. E.; Gustafsson, B.; Hammersley, P. L.; Kessler, M. F.; Lim, T. L.; Manfroid, J.; Metcalfe, L.; Salama, A. Bibcode: 1992Msngr..70...28V Altcode: No abstract at ADS Title: Modeling of Asteroidal Dust Production Rates Authors: Durda, Daniel D.; Dermott, Stanley F.; Gustafson, Bo A. S. Bibcode: 1992acm..proc..161D Altcode: The production rate of dust associated with the prominent Hirayama asteroid families and the background asteroidal population are modeled with the intent of using the families as a calibrator of mainbelt dust production. However, the dust production rates of asteroid families may be highly stochastic; there is probably more than an order of magnitude variation in the total area of dust associated with a family. Over 4.5 x 109 years of collisional evolution, the volume (mass) of a family is ground down by an order of magnitude, suggesting a similar loss from the entire mainbelt population. Our collisional models show that the number of meteoroids deliverable to Earth also varies stochastically, but only by a factor of 2 to 3. Title: The Origin and Evolution of the Zodiacal Dust Cloud Authors: Dermott, Stanley F.; Durda, Daniel D.; Gustafson, Bo A. S.; Jayaraman, S.; Xu, Y. L.; Gomes, R. S.; Nicholson, P. D. Bibcode: 1992acm..proc..153D Altcode: We have now analyzed a substantial fraction of the IRAS observations of the zodiacal cloud, particularly in the 25 micron waveband. We have developed a gravitational perturbation theory that incorporates the effects of Poynting-Robertson light drag (Gomes and Dermott, 1992). We have also developed a numerical model, the SIMUL mode, that reproduces the exact viewing geometry of the IRAS telescope and calculates the distribution of thermal flux produced by any particular distribution of dust particle orbits (Dermott and Nicholson, 1989). With these tools, and using a distribution of orbits based on those of asteroidal particles with 3.4 micron radii whose orbits decay due to Poynting-Robertson light drag and are perturbed by the planets, we have been able to: (1) account for the inclination and node of the background zodiacal cloud observed by IRAS in the 25 micron waveband; (2) relate the distribution of orbits in the Hirayama asteroid families to the observed shapes of the IRAS solar system dustbands; and (3) show that there is observational evidence in the IRAS data for the transport of asteroidal particles from the main belt to the Earth by Poynting-Robertson light drag. Title: Did Earth-Approaching Asteroids 3551, 3908, or 4055 Produce Meteorites? Authors: Gustafson, Bo A. S.; Williams, I. P. Bibcode: 1992acm..proc..219G Altcode: Orbital integrations show that Amor asteroid 3908 could have ejected one out of four plausible groups of meteorite producing fireballs during a collision in the asteroid belt. It was suggested by others that such a collision may also have split asteroids 3551 and 3908. A member of this group of fireballs is listed as one of the better possibilities for recovery. Title: Collisional and Dynamic Evolution of Dust from the Asteroid Belt Authors: Gustafson, Bo A. S.; Gruen, Eberhard; Dermott, Stanley F.; Durda, Daniel D. Bibcode: 1992acm..proc..223G Altcode: The size and spatial distribution of collisional debris from main belt asteroids is modeled over a 10 million year period. The model dust and meteoroid particles spiral toward the Sun under the action of Poynting-Robertson drag and grind down as they collide with a static background of field particles. Title: Why High Spectral Resolution - Even at Low Signal-To Ratio Authors: Gustafsson, B. Bibcode: 1992ESOC...40...17G Altcode: 1992hrsw.conf...17G No abstract at ADS Title: A Rugged Method to Determine the Solar Radiation Pressure Force to Gravitation Ratio (β) from Meteor Data Authors: Adolfsson, L. G.; Gustafson, B. S. Å. Bibcode: 1992DPS....24.1108A Altcode: 1992BAAS...24..952A No abstract at ADS Title: Optical and Physical Properties of Comet Dust Aggregates of the Vold-Sutherland and Related Types Authors: Gustafson, B. S. Å.; Palm, T.; Andersson, M.; Shu, Y. -L.; Zerull, R. H. Bibcode: 1992DPS....24.3802G Altcode: 1992BAAS...24.1017G No abstract at ADS Title: Is beryllium in metal-poor stars of galactic or cosmological origin? Authors: Gilmore, Gerard; Gustafsson, Bengt; Edvardsson, Bengt; Nissen, Poul E. Bibcode: 1992Natur.357..379G Altcode: Standard Big Bang nucleosynthesis predicts a very small primordial abundance of beryllium. Observations of nine very metal-poor stars indicate a beryllium abundance roughly proportional to the oxygen abundance, a trend that can be explained in terms of galactic chemical evolution. Combining this rate of beryllium production with recent observations of boron and lithium in similar stars yields an upper limit to the primordial beryllium abundance several orders of magnitude greater than the cosmological prediction, a result that can be explained by cosmicray activity in the early Galaxy. Title: Book-Review - the Birth and Early Evolution of Our Universe - Proceedings of Nobel SYMPOSIUM:79 - Graftavallen - Sweden - 1990 Authors: Nilsson, J. S.; Gustafsson, B.; Skagerstam, B. S. Bibcode: 1992Sci...255.1451N Altcode: No abstract at ADS Title: The Chemical and Dynamical Evolution of the Galactic Disk Authors: Gustafsson, B.; Edvardsson, B.; Nissen, P.; Lambert, D. L.; Tomkin, J.; Andersen, J. Bibcode: 1992IAUS..149...75G Altcode: No abstract at ADS Title: Can classical model atmospheres be of any use for the study of hypergiants Authors: Gustafsson, B.; Plez, B. Bibcode: 1992iesh.conf...86G Altcode: No abstract at ADS Title: Stellar Abundances - Recent Progress and Expectations Authors: Gustafsson, B. Bibcode: 1992eatc.conf...78G Altcode: No abstract at ADS Title: The circumstellar envelope of the carbon star S Scuti. Authors: Olofsson, H.; Carlstrom, U.; Eriksson, K.; Gustafsson, B. Bibcode: 1992A&A...253L..17O Altcode: CO(J = 1-0) observations of the bright carbon star S Sct show that the star is surrounded by a large (about 5.3 x 10 exp 17 cm) shell of gas expanding at a velocity of 16.5 km/s. It was produced during a brief period (about 1200 years) of high mass loss (about 4 x 10 exp-5 solar mass/yr) about 10 exp 4 years ago. The current mass losss rate and gas expansion velocity are only about 3 x 10 exp -8 solar mass/yr and about 5 km/s, respectively. This indicates that the star has gone through a very eruptive phase, possibly induced by a thermal pulse. The simple kinematics of the shell makes it possible to infer an overall spherical symmetry of the otherwise definitely clumpy CO brightness distribution. Thus, the mass loss must have been globally spherically symmetric, and the material was probably ejected in the form of lumps. Title: Dynamics of the Zodiacal Cloud (lecture) Authors: Dermott, S. F.; Gomes, R. S.; Durda, D. D.; Gustafson, B. Å. S.; Jayaraman, S.; Xu, Y. L.; Nicholson, P. D. Bibcode: 1992IAUS..152..333D Altcode: No abstract at ADS Title: Laboratory reflectance measurements of analogues to ``dirty'' ice surfaces on atmosphereless solar system bodies Authors: Stephens, John R.; Gustafson, Bo A. S. Bibcode: 1991Icar...94..209S Altcode: This article presents laboratory measurements of bidirectional reflectances from particle/ice mixtures representing "dirty" ice surfaces on atmosphereless Solar System bodies. The reflectance was monitored as ice sublimed under vacuum from the mixtures leaving behind porous refractory particle layers up to a millimeter thick. Similar layers or "dust-mantles" may evolve on cometary surfaces and on icy asteroids. The measurements cover a 40° to 90° phase angle at a fixed incidence angle of 20° from the surface normal. The spectral coverage is from the U band (350 nm) in the ultraviolet to the R band (720 nm) in the near infrared. Before significant ice sublimation, a 10% (by mass) colloidal silica in water ice sample was the brightest with reflectances in the 0.20-0.30 range. A similar mixture with the addition of 1% carbon had only 0.03 to 0.06 reflectance. A mixture of 1% carbon in water ice (without silica) had an intermediate reflectance of 0.05 to 0.20. Only carbon in ice showed marked angular dependence with a broad increase toward the specular angle. The initial reflectance spectra were slightly blue with reflectivity gradients (RG) < -1.4%/100 nm except for one carbon/silica/ice sample that was red in color with RG = 2.2%/100 nm. The formation of porous refractory layers or mantles through sublimation is coupled with significant changes in reflectance and color. The silica/ice sample more than doubled in reflectance to 0.53-0.78 and became bluer with RG > - 5%/100 nm. Reflectance from the carbon/ice changed to 0.05 with no phase angle dependence and became slightly red (RG < 1%/100 nm). The optical properties of the carbon/silica/ice samples are more complex and depend on the thermal history of the sample. These samples became more blue (RG < -0.67) as a mantle formed with increased reflectivities in the range of 0.07 to 0.18. The processed carbon/ice sample is optically most similar to dark icy Solar System bodies including C type asteroids (RG < 3%/100 nm, albedo ( Pv) < 0.05) and the asteroid Chiron (RG < 1%/100 nm, Pv ≈ 0.1). The sample is more neutral in color than D type asteroids (RG > 6%/100 nm, Pv < 0.05) and Comet Halley (RG = 6%/100 nm, Pv = 0.06). The carbon/silica/ices samples, with comparatively high reflectance and blue reflectivity gradients, are unlike asteroids or comets despite containing a mixture of silicate and carbonaceous material, a composition expected of these bodies. Differences in reflectance and reflectivity gradient between our samples and solar system bodies may reflect differing physical processes during mantle formation as well as differences in chemistry of silicate and carbonaceous materials. Further laboratory and theoretical work are needed to fully understand the optical consequences of mantle formation on atmosphereless icy Solar System bodies. Title: Light Scattering by Comet Dust Models Authors: Gustafson, B. S. Å.; Zerull, R. H.; Schulz, K.; Corbach, E. Bibcode: 1991BAAS...23.1160G Altcode: No abstract at ADS Title: Modelling the Zodiacal Dust Cloud Authors: Xu, -L. Y.; Dermott, S. F.; Gustafson, B. S. Å.; Jayaraman, S.; Durda, D. D. Bibcode: 1991BAAS...23.1149X Altcode: No abstract at ADS Title: Geminid Meteoroids and the Probability for Cometary Activity on Phaethon Authors: Adolfsson, L.; Gustafson, B. S. Å. Bibcode: 1991BAAS...23.1141A Altcode: No abstract at ADS Title: Origin and evolution of the zodiacal dust cloud Authors: Dermott, S. F.; Durda, D.; Gustafson, B.; Jayaraman, S.; Xu, Y. -L.; Nicholson, P. D.; Gomes, R. S. Bibcode: 1991pggp.rept..405D Altcode: The astrophysical importance of the zodiacal cloud became more apparent. The most useful source of information on the structure of the zodiacal cloud is the Infrared Astronomical Satellite (IRAS) observations. A substantial fraction of the extensive IRAS data set was analyzed. Also, a numerical model was developed (SIMUL) that allows to calculate the distribution of night-sky brightness that would be produced by any particular distribution of dust particle orbits. This model includes the effects of orbital perturbations by both the planets and solar radiation, it reproduces the exact viewing geometry of the IRAS telescope, and allows for the eccentricity of the Earth's orbit. SIMUL now is used to model not just the solar system dust bands discovered by IRAS but the whole zodiacal cloud. Title: The Origin and Evolution of the Zodiacal Dust Cloud Authors: Dermott, S. F.; Durda, D.; Gomes, R. S.; Gustafson, B.; Jayaraman, S.; Xu, Y. -L.; Nicholson, P. D. Bibcode: 1991LPICo.765...49D Altcode: No abstract at ADS Title: Modelling of Long Term Evolution and Equilibrium State of a Dust Component from the Asteroid Belt Authors: Gustafson, B. Å. S.; Grün, E. Bibcode: 1991LPICo.765Q..82G Altcode: No abstract at ADS Title: Spectroscopy of southern active stars. II. HD 32918, HD 82558, BD -22 3467, AB Doradus (HD 36705) and RST 137B. Authors: Vilhu, O.; Gustafsson, B.; Walter, F. M. Bibcode: 1991A&A...241..167V Altcode: We have observed the southern active cool stars HD 32918 (K1 IIIp), HD 82558 (K2 V), BD-22°3467 (G8 III), AB Doradus (HD 36705, K1 IV) and Rst 137 B (M 3-5), each of which lies close to the chromospheric- coronal saturation limit. The fractional Hα-luminosities LHα/Lbol of the stars were close to 10-4. No significant radial velocity variations were detected in any of the stars.

With the variations of the Fe I 6546-line profiles, as a function of the 9.55 d rotation period, the existence of a cool spot-region of HD 32918 was traced. The spectra were analysed by a surface imaging technique by Piskunov et al. (1990). The resulting image showed a large group of cool spots at the equatorial belt at one side of the star, and a smaller and less cool one extending to higher latitudes at the opposite longitude. Old photometry suggests that the equatorial spots might have been permanent during 7 yr at the same (active) longitude. The Hα-emission of HD 32918 was variable and asymmetric, comprising possibly of chromospheric and wind (or expanding chromosphere) components. The He I 5876 (D 3) absorption was remarkably strong in HD 32918, pointing to the existence of an extended and low density chromosphere.

BD-22°3467, the cool companion to the hot central star of the planetary nebula Abell 35, experiences a photometric wave with a 0.77 d period (Jasniewicz & Acker, 1988). Our observations, performed around the same time with this photometry, resolved a blue-shifted Hα-emission at the minimum light. This behaviour was opposite to that found in HD 32918. The υ sin i value (90 km s-1) of BD-22°3467 is compatible with the interpretation that the 0.77 d photometric cycle is the star's rotation period.

The Hα-emission of HD 82558 was stronger than in the previous observations by Fekel et al. (1986) and variable, but with no obvious rotational modulation. The Hα-emission strengths of the young pre-main-sequence pair AB Dor - Rst 137 B are compatible with those of the Pleiades stars (WHα vs. R - I, Stauffer & Hartmann 1986), giving additional support to the small age of the system. Rst 137 B has the He I 5876 triplet in strong emission (EW = 750±80 mA), and its photospheric lines are broad (υ sin i around 50 km s-1). These facts suggest that Rst 137 B is an extremely active M star. In AB Dor we detected two Hα-transients (the first in emission and the second one in absorption).

In the fastest rotators of our sample, AB Dor (0.51 d) and HD 82558 (1.66 d), we detected no He I D3 absorption nor emission. The physics of the Hα and He D3 transitions seem to be related. In low density and active chromospheres (with large optical thickness and filling factor) the lines appear in absorption (photo-ionization dominated plasma), while in very high density chromospheres (Rst 137 B) they are in emission (collisionally dominated plasma). Intermediate cases show no absorption nor emission (filled-in level, AB Dor as a typical example).

The lithium-abundances, as determined by us, suggest that AB Dor (logɛ(Li) = 3.1) and HD82558 (logɛ(Li) = 2.6) are premain-sequence stars, while HD 32918 (logɛ(Li) = 1.6-2.0) is most probably an evolved object. Title: The birth and early evolution of our universe. Proceedings. Nobel Symposium 79, Gräftåvallen (Sweden), 11 - 16 Jun 1990. Authors: Nilsson, J. S.; Gustafsson, B.; Skagerstam, B. -S. Bibcode: 1991PhST...36.....N Altcode: Contents: 1. Cosmic background radiation - primordial nucleosynthesis - inflation. 2. Large scale structure. 3. Cosmic strings and textures - dark matter - standard model physics. 4. Dark matter - standard model physics. 5. Quantum cosmology. Title: Size Distribution Dependance of Infrared Emission from Models of Asteroidal and Cometary Dust Authors: Gustafson, B. Å. S. Bibcode: 1991LPICo.765...81G Altcode: No abstract at ADS Title: Light Scattering by Open-Structured, Filamentary, Comet Dust Models Authors: Gustafson, B. Å. S.; Zerull, R. H.; Schulz, K.; Corbach, E. Bibcode: 1991LPICo.765...83G Altcode: No abstract at ADS Title: The future of stellar spectroscopy and its dependence on YOU. Authors: Gustafsson, B. Bibcode: 1991PhST...34...14G Altcode: The use of atomic data in contemporary stellar spectroscopy is illustrated by a number of examples of recent applications. The needs for extended and improved data are stressed. Title: The Shape of Meteor Streams in Orbital Parameter Space from Independent Meteor Surveys Authors: Gustafson, B. Å. S. Bibcode: 1991LPICo.765...80G Altcode: No abstract at ADS Title: Spectroscopy of Southern Active Stars Authors: Vilhu, O.; Gustafsson, B.; Walter, F. M. Bibcode: 1991LNP...380..492V Altcode: 1991IAUCo.130..492V; 1991sacs.coll..492V H and HeI D3 lines were observed in five active cool stars over their relatively short rotation periods. Three of the stars (AB Dor, Rst137B, HD82558) are in the pre main sequence phase (as deduced from their lithium abundances), while two are post main sequence FK Comae type stars (HD32918 and BD-223467) (Vilhu et al., 1991). We present the results of these observations and point out the physical similarity of the Ha and He D3 transitions (Fig.1). Title: A Search for Streams Associated with Earth-Approaching Asteroids 3551, 3908, and 4055 Authors: Gustafson, B. Å. S.; Williams, I. P. Bibcode: 1991LPICo.765R..82G Altcode: No abstract at ADS Title: The birth and early evolution of our universe Authors: Nillson, J. S.; Gustafsson, B.; Skagerstam, B. -S. Bibcode: 1991beeo.conf.....N Altcode: No abstract at ADS Title: A uvby-like photometric system for the WF/PC of the HST. Authors: Kiselman, D.; Oja, T.; Gustafsson, B. Bibcode: 1990A&A...238..265K Altcode: The possibility of combining four filters of the Hubble Space Telescope Wide Field/Planetary Camera into a uvby-like photometric system is discussed. On the basis of earth-based observations with appropriate filters, such a system consisting of WF/PC filters F 368M, F 413M, F 492M, and F 547M was calibrated for the determination of fundamental parameters of F dwarf stars. A good agreement was found between this empirical calibration and a theoretical one by Bell (1988). Good estimates of effective temperatures and metallicities can be obtained with this system, while gravity determinations require a UV filter at shorter wavelengths. Title: Book-Review - Astrophysics Authors: Gustafsson, B.; Nissen, P. E. Bibcode: 1990Sci...250..702G Altcode: No abstract at ADS Title: Formation of stable dust mantles on short-period comet nuclei Authors: Rickman, H.; Fernandez, J. A.; Gustafson, B. A. S. Bibcode: 1990A&A...237..524R Altcode: The study addresses a numerical analysis of the formation and evolution of dust mantles on the surfaces of cometary nuclei in order to determine the dependency on the perihelion distance, spin, and size of the nucleus. Two different regimes - free sublimation and gas diffusion, are considered. The nucleus is divided into latitude strips evolving independently of each other, and the computation starts with the whole nucleus in the free-sublimation regime. With the formation of a mantle, the code switches to the gas-diffusion regime. The formation of stable mantles is found to be frequent, most often when the spin axis is in the orbital plane and the perihelion distance is greater than 2 AU. It is noted that an implication of the presented results is that the nuclei of short-period comets may become completely mantled during their dynamical evolution into earth-approaching orbits. Title: Distribution and Thermal Properties of Dust Particles in the Zodiacal Cloud Authors: Gustafson, B.; Dermott, S. F.; Gomes, R. S. Bibcode: 1990BAAS...22Q1123G Altcode: No abstract at ADS Title: IRAS Observations of Cool Dust-Is There Dust in the Outer Solar System Beyond the Orbit of Pluto? Authors: Simpson, C.; Dermott, S. F.; Gomes, R. S.; Gottesman, S. T.; Gustafson, B.; Jayaraman, S. Bibcode: 1990BAAS...22.1118S Altcode: No abstract at ADS Title: IRAS Observations of the "Ten-Degree" Solar System Dust Bands Authors: Jayaraman, S.; Dermott, S. F.; Gomes, R. S.; Gustafson, B.; Simpson, C.; Xu, -L. Y.; Nicholson, P. D. Bibcode: 1990BAAS...22.1123J Altcode: No abstract at ADS Title: IRAS Observations of the Large-Scale Background Zodiacal Cloud Authors: Xu, -L. Y.; Dermott, S. F.; Gomes, R. S.; Gustafson, B.; Jayaraman, S.; Simpson, C.; Nicholson, P. D. Bibcode: 1990BAAS...22.1118X Altcode: No abstract at ADS Title: IRAS Observations of the "Near-Ecliptic" Solar System Dust Bands Authors: Dermott, S. F.; Gomes, R. S.; Gustafson, B.; Jayaraman, S.; Simpson, C.; Xu, -L. Y.; Nicholson, P. D. Bibcode: 1990BAAS...22.1124D Altcode: No abstract at ADS Title: A comparison of photospheric and circumstellar HCN / CO -ratios for bright carbon stars. Authors: Olofsson, H.; Eriksson, K.; Gustafsson, B. Bibcode: 1990A&A...230..405O Altcode: Measures of circumstellar HCN/CO abundance ratios for carbon stars are compared with corresponding ratios estimated from photospheric abundance analysis. A satisfactory agreement is found for most stars. However, V Hya and two 60 μm-excess sources have significantly lower circumstellar ratios than expected, and for the 13C-rich stars the ratios are somewhat higher. Title: Bright carbon stars with detached circumstellar envelopes - A naturalconsequence of helium shell flashes ? Authors: Olofsson, H.; Carlstrom, U.; Eriksson, K.; Gustafsson, B.; Willson, L. A. Bibcode: 1990A&A...230L..13O Altcode: CO radio map data are presented for the bright carbon stars R Scl, U Ant, S Sct, and TT Cyg. The stars are found to have large circumstellar envelopes which, at least in the last three cases, are geometrically thin and clearly detached from the stars, indicating that the mass loss has occurred episodically. The possibility that these episodes are triggered by helium shell flashes is discussed and found consistent with existing data. Title: Are the Geminids High Density Porous Flakes from a Surface Crust on Phaethon? Authors: Gustafson, B. Å. S. Bibcode: 1990acm..proc..523G Altcode: 1989acm..proc...54G No abstract at ADS Title: Model Calculations of Mantle Formation on Comet Nuclei Authors: Rickman, H.; Gustafson, B. Å. S.; Fernández, J. A. Bibcode: 1990acm..proc..423R Altcode: 1989acm..proc..106R No abstract at ADS Title: Modeling of shells around carbon stars. Authors: Carlström, U.; Eriksson, K.; Gustafsson, B.; Olofsson, H.; Stenholm, L.; Willson, L. A. Bibcode: 1990apsu.conf...13C Altcode: No abstract at ADS Title: The chemical evolution of the galactic disk. Authors: Edvardsson, B.; Gustafsson, B.; Andersen, J.; Nissen, P. E.; Lambert, D. L.; Tomkin, J. Bibcode: 1990apsu.conf...21E Altcode: No abstract at ADS Title: Abundances in solar type disk stars. Authors: Edvardsson, B.; Gustafsson, B.; Andersen, J.; Nissen, P. E.; Lambert, D. L.; Tomkin, J. Bibcode: 1990nba..meet...93E Altcode: 1990taco.conf...93E Abundances of O, Na, Mg, Al, Si, Ca, Ti, Fe, Ni, Y, Zr, Ba and Nd have been derived for up to 189 solar type stars with known ages and space velocities. Title: A Study of Bright Carbon Stars Authors: Olofsson, H.; Carlstrom, U.; Eriksson, K.; Gustafsson, B.; Willson, L. A. Bibcode: 1990fmpn.coll..341O Altcode: No abstract at ADS