bluuebunny/crossref_metadata_2025 huggingface dataset:
Orbital stability of Earth-type planets in stellar binary systems
Authors: Eberle Jason , Cuntz Manfred , Musielak Zdzislaw E.
Published: October 2010

An important factor in estimating the likelihood of life elsewhere in the Universe is determining the stability of a planet's orbit. A significant fraction of stars like the Sun occur in binary systems which often has a considerable effect on the stability of any planets in such a system. In an effort to determine the stability of planets in binary star systems, we conducted a numerical simulation survey of several mass ratios and initial conditions. We then estimated the stability of the planetary orbit using a method that utilizes the hodograph to determine the effective eccentricity of the planetary orbit. We found that this method can serve as an orbital stability criterion for the planet.
Multiplicity study of exoplanet host stars
Authors: Mugrauer Markus , Neuhäuser Ralph , Ginski Christian , Eisenbeiss Thomas
Published: October 2010

We present recent results of our ongoing multiplicity study of exoplanet host stars.
Defining the envelope for the search for life in the Universe
Authors: Rothschild Lynn J.
Published: October 2010

The search for life in the universe relies on defining the limits for life and finding suitable conditions for its origin and evolution elsewhere. From the biological perspective, a conservative approach uses life on earth to set constraints on the environments in which life can live. Conditions for the origin of life, even on earth, cannot yet be defined with certainty. Thus, we will describe what is known about conditions for the origin of life and limits to life on earth as a template for life elsewhere, with a particular emphasis on such physical and chemical parameters as temperature, pH, salinity, desiccation and radiation. But, other life forms could exist, thus extending the theoretical possibility for life elsewhere. Yet, this potential is not limitless, and so constraints for life in the universe will be suggested.
Earthshine observations and the detection of vegetation on extrasolar planets
Authors: Briot Danielle
Published: October 2010

To prepare future observations of terrestrial planets and the detection of life, we search for life on the planet Earth seen as a point source. Observations of Earthshine is a convenient way to see Earth as a remote planet. The vegetation reflectance spectrum presents a sharp edge in the near infrared: the Vegetation Red Edge. Observational programs in progress are described, particularly our observations at the Concordia station in Antarctica.
Mineralogical study of proto-planetary disks in FU Orionis stars
Authors: Sainz Emanuel J. , Gomez Mercedes
Published: October 2010

We report on mid-infrared (8–13 μm) spectroscopic observations of eight FU Orionis type objects and discuss a qualitative initial mineralogical analysis.
Interior structure models of terrestrial exoplanets and application to CoRoT-7 b
Authors: Wagner Frank W. , Sohl Frank , Rauer Heike , Hussmann Hauke , Grott Matthias
Published: October 2010

In this study, we model the internal structure of CoRoT-7b, considered as a typical extrasolar terrestrial planet, using mass and energy balance constraints. Our results suggest that the deep interior is predominantly composed of dry silicate rock, similar to the Earth's Moon. A central iron core, if present, would be relatively small and less massive (<15 wt.% of the planet's total mass) as compared to the Earth's (core mass fraction 32.6 wt.%). Furthermore, a partly molten near-surface magma ocean could be maintained, provided surface temperatures were high enough and the rock component mainly composed of Earth-like mineral phase assemblages.
Mars Science Laboratory (MSL) and the future missions to Mars
Authors: Cabane Michel ,   the SAM Team
Published: October 2010

After their formation, and for almost 0.5 Gyr, Mars and Earth evolved in the same manner. On Earth, life occured very early, around 3.6 Gy ago. Then, the hypothesis that life might have occured also on Mars, and be extinct, is not unrealistic. If this is true, then complex molecules could be present, representing an early state of life-building blocks. Missions to Mars (Viking 1-2, Phoenix) have carried instruments capable to search for molecular indicators, although up to now, no positive detection has been obtained. Future missions to Mars (MSL-NASA, Exomars-ESA) will use enhanced experiments to try to end this quest.
Characteristics of the Kepler target stars
Authors: Batalha Natalie M. , Borucki William J. , Koch David G. , Brown Timothy M. , Caldwell Douglas A. , Latham David W.
Published: October 2010

The Kepler Mission successfully launched March 6, 2009, beginning its 3.5-year mission to determine the frequency of Earth-size planets in the habitable zones of late-type stars. The brightnesses of over 100,000 stars are currently being monitored for transit events with an expected differential photometric precision of 20 ppm at V=12 for a 6.5-hour transit. The same targets will be observed continuously over the mission duration in order to broaden the detection space to orbital periods comparable to that of Earth. This paper provides an overview of the selection and prioritization criteria used to choose the stars that Kepler is observing from the > 4.5 million objects in the 100 square degree field of view. The characteristics of the Kepler targets are described as well as the implications for detectability of planets in the habitable zone smaller than 2R⊕.
SIM Lite astrometric observatory for detection of Earth-like planets
Authors: Pan Xiaopei , Shao Michael , Goullioud Renaud
Published: October 2010

The SIM Lite Astrometric Observatory is an optical astrometry mission for detection of Earth-like planets and investigation of dark matter, galaxy assembly, black holes etc. SIM Lite is a minimum system that performs the full NRC recommenced SIM science programs. This paper summarize the latest status and progresse of the SIM Lite space mission.
Gavriil Adrianovich Tikhov (1875-1960) a pioneer in astrobiology
Authors: Tejfel Victor
Published: October 2010

Astrobiology emerged as a scientific discipline in Kazakhstan more than half-a-century ago and flourished for many years under the leadership of Gavriil A. Tikhov, the oldest Pulkovian astrophysicist, member of the Academy of Sciences of the KazSSR (ASKSSR), and corresponding member of the Academy of Sciences of the USSR.
George W. Wetherill (1925-2006): physicist, geochemist, planetary scientist, astrobiologist
Authors: Boss Alan P.
Published: October 2010

Trained as a physicist, George W. Wetherill (1925-2006) made seminal contributions to the fields of geochemical dating, meteoritical and asteroidal science, and the theory of the formation of terrestrial planets, evolving along the way into one of the first astrobiologists.
Accretion dynamics and star-disk interaction in NCG 2264
Authors: Alencar Silvia H. P. , Bouvier Jérôme , Catala Claude , Fernandez Matilde , Gameiro Jorge Filipe , Fonseca Nathalia , Guimarães Marcelo Medeiros , Hetem Jane Gregorio , McGinnis Pauline Telles , Moraux Estelle , Teixeira Paula
Published: October 2010

The Corot satellite observed the young stellar cluster NGC 2264 during 23 days in March 2008. This was the first time a group of young accreting stars, classical T Tauri stars (CTTS), were followed ininterruptedly with high photometric accuracy for such a long run. Before the Corot observations, AA Tau (Bouvier et al. 2003, A&A, 409, 169 and Bouvier et al. 2007, A&A, 463, 1017) was one of the few CTTS systems that had been analysed synoptically over several consecutive rotational periods. Its analysis suggested a highly dynamical star-disk interaction mediated by the stellar magnetic field, as predicted by magneto-hydrodynamical simulations of young accreting systems.
Proto-planetary disks with CARMA: sub-arsecond observations at millimeter wavelengths
Authors: Andrea Isella , Carpenter John M. , Perez Laura , Sargent Anneila I.
Published: October 2010

Using the Combined Array for Research in Millimeter-wave Astronomy (CARMA) we observed several proto-planetary disks in the dust continuum emission at 1.3 and 2.8 mm (Isella et al. 2009a, 2009b). The observations have angular resolution between 0.15 and 0.7 arcsecond, corresponding to spatial scales spanning from about the orbit of Saturn up to about the orbital radius of Pluto. The observed disks are characterized by a variety of radial profiles for the dust density. We observe inner disk clearing as well as smooth density profiles, suggesting that disks may form, or evolve, in different ways. Despite that, we find that the characteristic disk radius is correlated with the stellar age increasing from 20 AU to 100 AU over about 5 Myr. Interpreting our results in terms of the temporal evolution of a viscous α-disk, we estimate that (i) at the beginning of the disk evolution about 60% of the circumstellar material was located inside radii of 25-40 AU, (ii) that disks formed with masses from 0.05 to 0.4 solar masses and (iii) that the viscous timescale at the disk initial radius is about 0.1-0.3 Myr. Viscous disk models tightly link the surface density Σ(R) with the radial profile of the disk viscosity ν(R)∝ Rγ. We find values of γ ranging from -0.8 to 0.8, suggesting that the viscosity dependence on the orbital radius can be very different in the observed disks. We demonstrate that the similarity solution for the surface density for γ < 0 can explain the properties of some “transitional” disks without requiring discontinuities in the disk surface density. In the case of LkCa 15, a smooth distribution of material from few stellar radii to about 240 AU can produce both the observed SED and the spatially resolved continuum emission at millimeter wavelengths. For two sources, RY Tau and DG Tau, we observed the dust emission with a resolution as high as 0.15 arcsecond, which corresponds to a spatial scale of 20 AU at the distance of the two stars. The achieved angular resolution is a factor 2 higher than any existing observation of circumstellar disks at the same wavelengths and enable us to investigate the disk structure with unprecedent details. In particular, we present a first attempt to derive the radial profile of the slope of the dust opacity β. We find mean values of β of 0.5 and 0.7 for DG Tau and RY Tau respectively and we exclude that β may vary by more than ±0.4 between 20-70 AU. This implies that the circumstellar dust has a maximum grain size between 10 μm and few centimeters.
Resolving structure in the HD100546 disk - signatures of planet building?
Authors: Maddison S. T. , Wright C. M. , Lommen D. , Burton M. , Wilner D. , Bourke T.
Published: October 2010

Several lines of evidence suggest that planet formation may be well underway within the circumstellar disk of the enigmatic Herbig Be star HD100546, including a cleared inner cavity, spiral structure, and similar dust mineralogy as seen in our own solar system. To learn more about the processes occurring in this disk we have conducted a multi-frequency observing program with the Australia Telescope Compact Array (ATCA).
[Ne II] and X-ray emission from ρ Ophiuchi young stellar objects
Authors: Flaccomio E. , Stelzer B. , Sciortino S. , Pillitteri I. , Micela G.
Published: October 2010

Circumstellar disks are mostly made of gas. Constraining the spatial and thermal structure of the gas, and its time evolution, is crucial to understand the star- and planet-formation processes. Models predict that the gas is affected by UV and X-ray radiation from the central young stellar object (YSO), but many uncertainties remain, e.g. whether the EUV emission actually reaches the disk or is absorbed by disk winds. The infrared [Ne II] and [Ne III] fine structure lines at 12.81μm and 15.55μm have been theoretically predicted to trace the circumstellar disk gas subject to X-ray heating and ionization.
A movie of accretion/ejection of material in a high-mass YSO in Orion BN/KL at radii comparable to the Solar System
Authors: Goddi C. , Greenhill L. , Humphreys E. , Matthews L. , Chandler C.
Published: October 2010

Around high-mass Young Stellar Objects (YSOs), outflows are expected to be launched and collimated by accretion disks inside radii of 100 AU. Strong observational constraints on disk-mediated accretion in this context have been scarce, largely owing to difficulties in probing the circumstellar gas at scales 10-100 AU around high-mass YSOs, which are on average distant (>1 Kpc), form in clusters, and ignite quickly whilst still enshrouded in dusty envelopes. Radio Source I in Orion BN/KL is the nearest example of a high-mass YSO, and only one of three YSOs known to power SiO masers. Using VLA and VLBA observations of different SiO maser transitions, the KaLYPSO project (http://www.cfa.harvard.edu/kalypso/) aims to overcome past observational limitations by mapping the structure, 3-D velocity field, and dynamical evolution of the circumstellar gas within 1000 AU from Source I. Based on 19 epochs of VLBA observations of v=1,2 SiO masers over ~2 years, we produced a movie of bulk gas flow tracing the compact disk and the base of the protostellar wind at radii < 100 AU from Source I. In addition, we have used the VLA to map 7mm SiO v=0 emission and track proper motions over 10 years. We identify a narrowly collimated outflow with a mean motion of 18 km/s at radii 100-1000 AU, along a NE-SW axis perpendicular to that of the disk traced by the v=1,2 masers. The VLBA and VLA data exclude alternate models that place outflow from Source I along a NW-SE axis. The analysis of the complete (VLBA and VLA) dataset provides the most detailed evidence to date that high-mass star formation occurs via disk-mediated accretion.
Magnetospheric accretion & outflows in stars & brown dwarfs: theories and observational constraints
Authors: Mohanty S.
Published: October 2010

The manner in which young classical T Tauri stars (cTTs) and brown dwarfs accrete gas from their surrounding disks and simultaneously drive jets and outflows is central to star and planet formation and angular momentum evolution, but remains an ill-understood and hotly debated subject. One of the central concerns is the stellar field geometry: while analytic theories assume an idealized stellar dipole, T Tauri fields are observed to be complex multipolar beasts. I present an analytic generalization of the X-wind theory to include such fields. Independent of the precise field geometry, the generalized model makes a unique prediction about the relationship between various cTTs observables. I show that this prediction is supported by observations of accretion rate, hot spot size, stellar rotation and field strength from stellar to brown dwarf masses, including recent detailed spectropolarimetric measurements. I also discuss the unique insights offered by recent magnetic field measurements on accreting brown dwarfs: while they agree with the accretion theory above, they also pose a puzzle for magnetic field generation theory. Resolving this conundrum promises to illuminate our general picture of accretion and angular momentum transport in fully convective objects.
Brown Dwarf Model Atmospheres Based on Multi-Dimensional Radiation Hydrodynamics
Authors: Allard France , Freytag Bernd
Published: October 2010

The atmospheres of Brown Dwarfs (BDs) are the site of molecular opacities and cloud formation, and control their cooling rate, radius and brightness evolution. Brown dwarfs evolve from stellar-like properties (magnetic activity, spots, flares, mass loss) to planet-like properties (electron degeneracy of the interior, cloud formation, dynamical molecular transport) while retaining, due to their fully convective interior, larger rotational velocities (≤ 30 km/s i.e. P < 4 hrs versus 11 hrs for Jupiter). Model atmospheres treating all this complexity are therefore essential to understand the evolution properties, and to interpret the observations of these objects. While the pure gas-phase based NextGen model atmospheres (Allard et al. 1997, Hauschildt et al. 1999) have allowed the understanding of the several populations of Very Low Mass Stars (VLMs), the AMES-Dusty models (Allard et al. 2001) based on equilibrium chemistry have reproduced some near-IR photometric properties of M and L-type brown dwarfs, and played a key role in the determination of the mass of brown dwarfs and Planetary Mass Objects (PMOs) in the eld and in young stellar clusters. In this paper, we present a new model atmosphere grid for VLMs, BDs, PMOs named BT-Settl, which includes a cloud model and dynamical molecular transport based on mixing information from 2D Radiation Hydrodynamic (RHD) simulations (Freytag et al. 2009). We also present the status of our 3D RHD simulations including rotation (Coriolis forces) of a cube on the surface of a brown dwarf. The BT-Settl model atmosphere grid will be available shortly via the Phoenix web simulator (http://phoenix.ens-lyon.fr/simulator/).
Physical Properties of Binary Brown Dwarfs
Authors: Brandner W. , Stumpf M. , Köhler R. , Joergens V. , Hormuth F. , Geißler K. , Goldman B. , Henning T. , Bouy H. , Martin E.
Published: October 2010

Astrometric observations of binary brown dwarfs yield dynamical masses of the components independently of theoretical models. We give an update on our long-term high-resolution spectroscopic and photometric monitoring programme of spatially resolved binary brown dwarfs using ground-based adaptive optics and the Hubble Space Telescope. We present current orbital fits, including refined dynamical mass estimate of the Kelu-1 AB system. The results seem to support the previously reported trend that evolutionary and atmospheric models might underestimate the mass of very-low-mass stars and brown dwarfs.
Testing Models with Brown Dwarf Binaries
Authors: Dupuy Trent J. , Liu Michael C.
Published: October 2010

We have been using Keck laser guide star adaptive optics to monitor the orbits of ultracool binaries, providing dynamical masses at lower luminosities and temperatures than previously available and enabling strong tests of theoretical models. (1) We find that model color–magnitude diagrams cannot reliably be used to infer masses as they do not accurately reproduce the colors of ultracool dwarfs of known mass. (2) Effective temperatures inferred from evolutionary model radii can be inconsistent with temperatures derived from fitting observed spectra with atmospheric models by at most 100–300 K. (3) For the single pair of field brown dwarfs with a precise mass (3%)andage determination (≈25%), the measured luminosities are ~2–3× higher than predicted by model cooling rates (masses inferred fromLboland age are 20–30% larger than measured). Finally, as the sample of binaries with measured orbits grows, novel tests of brown dwarf formation theories are made possible (e.g., testing theoretical eccentricity distributions).
Mid-Infrared Variability in Binary Brown Dwarfs
Authors: Sterzik Michael F. , Chauvin Gael , Geißler Kerstin , Pantin Eric
Published: October 2010

We have spatially resolved several nearby binary brown dwarfs and obtained mid-infrared photometry with VISIR at the VLT. In particular, we have monitored ε Indi B and HD 130948 in several narrow-band MIR filters. The 10.5μm band is a probe to constrain non-equilibrium chemistry in the atmosphere of cool brown dwarfs.
CORNISH: A 5 GHz VLA survey of the Galactic plane
Authors: Purcell Cormac R. , Hoare Melvin G. ,   the CORNISH team
Published: October 2010

The CORNISH (Co-Ordinated Radio ‘N’ Infrared Survey for High-mass star formation) project is the radio continuum part of a series of multi-wavelength surveys of the Galactic Plane that focus on the northern GLIMPSE-I region (10° < l <65°, |b| < 1°) observed by the SPITZER satellite in the mid-infrared (Churchwell et al. 2009). CORNISH has delivered a complementary 5 GHz arcsecond resolution, radio-continuum survey to address key questions in high-mass star formation as well as many other areas of astrophysics.
High spatial resolution Galactic 3D extinction mapping with IPHAS
Authors: Sale S. E. , Drew J. E. ,   the IPHAS Collaboration
Published: October 2010

An algorithm, MEAD, is presented, which can map extinction in three dimensions, with fine distance and angular resolutions. MEAD is then employed when studying the structure of the outer Galaxy. We show that the Galaxy's radial density profile takes the form of a broken exponential, with density dropping off more steeply beyond a Galacto-centric radius of ~13 kpc.
I-GALFA: The Inner-Galaxy ALFA Low-Latitude H I Survey
Authors: Koo Bon-Chul , Gibson Steven J. , Kang Ji-hyun , Douglas Kevin A. , Park Geumsook , Peek Joshua E. G. , Korpela Eric J. , Heiles Carl E. , Bania Thomas M.
Published: October 2010

The I-GALFA survey is mapping HI 21 cm emission in the inner parts of our Milky Way Galaxy using the Arecibo L-band Feed Array (ALFA). Examples of various H i features such as supershells and chimneys are shown.
Abundance structure and chemical evolution of the Galactic disc
Authors: Bensby Thomas , Feltzing Sofia
Published: October 2010

We have obtained high-resolution, high signal-to-noise spectra for 899 F and G dwarf stars in the Solar neighbourhood. The stars were selected on the basis of their kinematic properties to trace the thin and thick discs, the Hercules stream, and the metal-rich stellar halo. A significant number of stars with kinematic properties ‘in between’ the thin and thick discs were also observed to investigate in greater detail the dichotomy of the Galactic disc. All stars have been homogeneously analysed, using the exact same methods, atomic data, model atmospheres, etc., and also truly differentially to the Sun. Hence, the sample is likely to be free from internal errors, allowing us to, in a multi-dimensional space consisting of detailed elemental abundances, stellar ages, and the full three-dimensional space velocities, reveal very small differences between the stellar populations.
Abundance gradients: tracing the chemical properties of the disk
Authors: Costa Roberto D.D. , Maciel Walter J.
Published: October 2010

Abundance gradients are key parameters to constrain the chemical evolution of the galactic disk. In this review recent determinations for the radial gradient are described, including its slope as derived from different objects such as planetary nebulae, HII regions, cepheids, or B stars, and for different elements. Inner and outer limits for the radial gradient, as well as its time evolution, both related to the chemical evolution of the Galaxy, are also described. The possible existence of azimuthal and vertical gradients is also discussed.
Physics and Structure of the Galactic disc(s)
Authors: Schönrich Ralph A.
Published: October 2010

The combination of classical models of chemical evolution with radial mixing and dynamics of the Galactic disc has opened alternative methods of understanding the detailed structure of the solar neighbourhood. I will show how radial mixing alters the views on chemical evolution as demonstrated by Schönrich & Binney (2009). I will explain how the model gives rise to a very natural division of the Galactic disc into a thick and a thin component, which can be examined in the light of detailed observational studies combining information on kinematics, chemistry and stellar ages.
Star formation simulations: caveats
Authors: Goodwin Simon P.
Published: October 2010

Star formation is such a huge problem, covering such a large range of physical scales and involving so many physical processes, that the results of simulations should always be taken with care.
A New Comprehensive Catalogue of Infrared Dark Clouds
Authors: Fuller G. A. , Peretto N.
Published: October 2010

To better characterise infrared dark clouds (IRDCs), and the star formation within them, a comprehensive catalogue of IRDCs has been constructed from the Spitzer GLIMPSE and MIPSGAL archival data. Mosaicing the individual survey blocks together, we have used a new extraction method to identify dark clouds up to 30′ in size, and produce a column density image of each cloud. In total the catalogue contains over 11,000 clouds, defined as connected regions with 8 micron optical depth > 0.35 (corresponding to column densities < 1022cm−2). The extraction algorithm also identifies sub-structures (fragments) within each cloud. These Spitzer dark clouds (SDCs) range in mass from 10M⊙to 104M⊙. About 80% of the SDCs were previously unidentified. Only ~ 30% of the SDCs are associated with 24μm point-like sources, leaving the majority of these clouds with no apparent sign of star formation activity. This new catalogue provides an important new resource for future studies of the initial conditions of star formation in the Galaxy.
The JCMT Legacy Survey: Mapping the Milky Way in the Submillimetre
Authors: Chrysostomou Antonio ,   the members of the JLS teams
Published: October 2010

The JCMT Legacy Survey (JLS) is an ambitious programme of independent surveys to study our Galaxy and universe in the submillimetre (λ = 450 − 850 μm) from the summit of Mauna Kea, Hawaii. With its scientific breadth and unique spectral window, it is clear that the JLS will have a significant impact on star formation studies in the near future and beyond. Its complementarity with other surveys (e.g. Spitzer, Herschel) will make the JLS a very valuable resource for multi-wavelength studies for low and high-mass star formation across the Milky Way. The JLS is currently in its second year of operation.
The Galactic star formation rate as seen by the Spitzer Space Telescope
Authors: Robitaille Thomas P. , Whitney Barbara A.
Published: October 2010

We present preliminary results of a study to determine the star formation rate of the Galaxy using a census of young stellar objects (YSOs) in the Spitzer/GLIMPSE and MIPSGAL surveys, which cover nearly 300 square degrees of the Galactic mid-plane. We find a value of 1.7 M⊙/yr, consistent with independent estimates.
The Red MSX Source Survey - Massive Star Formation in the Milky Way
Authors: Lumsden Stuart , Hoare Melvin , Davis Ben ,   the RMS team
Published: October 2010

We present the results of a Galaxy-wide survey for young massive stars still in the process of formation. Our data are consistent with a model in which the stars form through accretion disks with the overall Galactic star formation rate being 3 M⊙ per year.
Star Formation Histories from Pan-Chromatic Infrared Continuum Surveys
Authors: Molinari Sergio
Published: October 2010

One of the currently most disputed issues in Star Formation is the timeline of the whole process. Is it a “slow” process of cloud assembly which, mediated by magnetic fields, evolve toward turbulence-supported clumps which are eventually super-critical to collapse, e.g. McKee & Tan (2003)? Or do clumps originate in already super-critical state in the post-shock regions of large-scale Galactic converging flows, e.g. Hartmann et al. (2001) with a rapid collapse in a crossing time or so (Elmegreen 2000)?

A pan-chromatic 1μm-1mm continuum view of cluster forming regions in their early stages offers access to the most massive members longward of 5-10μm, as well as the low-mass members which instead dominate the emission in the near-IR, offering an interesting potential in stimulating advances in theoretical modelling of clustered star formation, its history and rate.
The population of Planetary Nebulae in the Milky Way
Authors: Corradi Romano L. M.
Published: October 2010

Extensive surveys of the Milky Way have provided a global view of the population of planetary nebulae in the Milky Way. Their chemical, dynamical, and morphological properties, the link with their red giant progenitors and white dwarf descendants, and the implications on our understanding of the chemical evolution of the Galaxy, are discussed.
The Galactic Pulsar Population
Authors: Lorimer Duncan R.
Published: October 2010

Simulations of the Galactic pulsar population are reviewed. These include snapshot and time-dependent models of normal pulsars as well as binary and milli-second pulsars.
The H.E.S.S. Galactic Plane Survey
Authors: de Oña-Wilhelmi Emma
Published: October 2010

The H.E.S.S. Galactic Plane Survey (GPS) has revealed a large number of Galactic Sources, including Pulsar Wind Nebulae (PWN), Supernova Remnants (SNRs), giant molecular clouds, star formation regions and compact binary systems, as well as a number of unidentified objects, or dark sources, for which no obvious counterparts at other wavelengths have yet been found. We will review the latest results from the GPS observations and discuss the most interesting cases.
Red clump giant stars as tracers of Galactic structure
Authors: López-Corredoira M. , Cabrera-Lavers A. , Hammersley P. L. , Garzón F. , Mahoney T. J. , González-Fernández C.
Published: October 2010

By isolating the red clump giant population in the color-magnitude diagrams and inverting their star counts, we can obtain directly the density distribution of the old stellar population along the line of sight. We have applied this method to several near infrared surveys and obtained information on the disc, bulge and long bar. The disc is well fitted by an exponential distribution in both the galactocentric distance and height, flared and warped in the outer parts, and with a deficit of stars in the inner in-plane regions. The long bar occupies these in-plane regions within R < 3.9 kpc, with approximate dimensions of 7.8 kpc × 1.2 kpc × 0.2 kpc and a position angle of 40-45 deg. The bulge is a triaxial structure, possibly boxy, thicker and shorter than the long bar and with position angle of 10-30 deg.
New Galactic Wolf-Rayet Stars Discovered via 2MASS + Spitzer
Authors: Mauerhan Jon C. , Van Dyk Schuyler D. , Morris Pat W.
Published: October 2010

We have undertaken a campaign to expand the census of WRs throughout the Galaxy using the 2MASS and Spitzer/GLIMPSE surveys. Free-free emission generated within the ion-dense winds of WRs generates a significant infrared excess which forms the basis of an excellent criterion for photometrically selecting WRs from the stellar field.
The Pan-STARRS 3π Survey and the Brown Dwarf Factory
Authors: Magnier E. A. , Liu M. , Goldman B. , Monet D. G. , Chambers K. C. , Kaiser N.
Published: October 2010

The Pan-STARRS 1 Telescope (PS1) is currently (2009 Aug) undergoing final commissioning efforts and starting to perform initial science observations for the PS1 survey mission. PS1 will greatly expand the known population of Brown Dwarfs, with discovery via photometry, proper-motion, and parallax.
Prediction Uncertainty in the Bornhuetter-Ferguson Claims Reserving Method: Revisited
Authors: Alai D. H. , Merz M. , Wüthrich M. V.
Published: October 2010

We revisit the stochastic model of Alai et al. (2009) for the Bornhuetter-Ferguson claims reserving method, Bornhuetter & Ferguson (1972). We derive an estimator of its conditional mean square error of prediction (MSEP) using an approach that is based on generalized linear models and maximum likelihood estimators for the model parameters. This approach leads to simple formulas, which can easily be implemented in a spreadsheet.
Ex situ and in situ methods of inspecting and optimizing adaptive bimorph mirrors
Authors: Sutter J. P. , Alcock S. , Sawhney K.
Published: October 2010

At the Diamond Light Source, adaptive bimorph mirrors are extensively used to focus synchrotron light. Piezo crystals embedded in each bimorph mirror expand or contract in response to applied voltages, enabling the curvature of the reflecting surface to adapt to the required form. However, high-grade metrology tools are needed to determine the optimal voltages. The Diamond Optics & Metrology group have implemented in situ (on the beamlines) and ex situ (in a metrology lab) methods of characterizing optical surfaces. For ex situ tests, a slope-measuring profiler (the Diamond-NOM (Nanometre Optical Metrology)) is employed. In situ, X-ray pencil beam scans, performed using an X-ray sensitive camera and software designed in-house, are used to correct optical slope errors. Ex situ and in situ data are shown to be in good agreement. Examples of in situ improvements in the focusing quality and deliberate defocusing are shown. The methods developed are also applicable to many other forms of adaptive optics.
Effects of source size and wavefront propagation on the energy resolution of a bent-crystal polychromator
Authors: Sutter J. P. , Amboage M. , Hayama S. , Díaz-Moreno S.
Published: October 2010

Polychromators, or elliptically bent diffracting crystals that focus a broad-bandwidth X-ray beam onto a sample, have become a common device at synchrotron beamlines specializing in X-ray absorption spectroscopy (XAS) because they allow a full absorption spectrum to be collected in one shot. Such a device is being planned for the XAS beamline I20 of the Diamond Light Source. A bent silicon crystal diffracting 7 keV X-rays with the (1 1 1) reflection is taken as a model for the simulations of this report. Instrumental resolution is determined by the demagnification of the source, the spread of the diffracted beam during propagation and the pixel size of the position-sensitive detector placed behind the sample. The first is calculated by geometrical optics. The second is calculated by a full wave-optical treatment, which includes Takagi–Taupin integration to find the diffracted amplitude at the crystal's surface and Huygens–Fresnel propagation of the diffracted wave to the sample or detector. This sets the polychromator's intrinsic energy resolution. The pixel size of the detector is then added to find the total instrumental resolution at various sample–detector distances.
European synchrotron radiation facility upgrade beamline UPBL6 – inelastic scattering
Authors: Martel K. , Astruc A. , Barrett R. , Henriquet C. , Huotari S. , Monaco G. , del Rio M. Sanchez , Verbeni R. , Zhang L.
Published: October 2010

As part of phase 1 of the European synchrotron radiation facility (ESRF) upgrade programme, a new beamline (UPBL6) for the study of electronic excitations using inelastic scattering and emission spectroscopy will be designed and constructed. The new beamline will provide an intense stable X-ray beam at two different spectrometers to be used on a time-shared basis. One of the spectrometers will be dedicated to resonant inelastic X-ray scattering (RIXS); the other to X-ray Raman spectroscopy (XRS). This beamline is currently (June 2010) in the design phase and may be fully operational by early 2013.
The controller for Shanghai Synchrotron Radiation Facility in-vacuum undulators
Authors: Gu M. , Yuan Q.B. , Chen Z.H. , Wang R.P. , Chen R.
Published: October 2010

The in-vacuum undulator (IVU) controller has been developed and applied in Shanghai Synchrotron Radiation Facility (SSRF), China. The controller based on programmable logic controller (PLC) mainly controls two stepper motors for regulating the gap and taper of magnet array, implement automatic control of the correction coil power supplies, etc. In addition, the controller is also provided with a local and remote working mode. This paper mainly introduces related hardware and software design for the IVU controller.
Residual stress measurement on the I12 JEEP beamline at Diamond Light Source
Authors: Korsunsky A. M. , Song X. , Hofmann F. , Abbey B. , Xie M. , Connolley T. , Reinhard C. , Atwood R. , Connor L. , Drakopoulos M.
Published: October 2010

One of the multiple capabilities of the new Joint Engineering, Environmental and Processing (JEEP) beamline I12 at Diamond Light Source is the set-up for polychromatic high-energy X-ray diffraction for the study of polycrystalline deformation and residual stresses. The results and interpretation of the first experiments carried out on JEEP are reported. Energy dispersive diffraction patterns from titanium alloy Ti-6Al-4V were collected using the new 23-cell ‘horseshoe’ detector and interpreted using Pawley refinement to determine the residual elastic strains at the macro- and meso-scale. It provides a clear demonstration of the tensile-compressive hardening asymmetry of the hexagonal close-packed grains oriented with the basal plane perpendicular to the loading direction.
A global positioning system–based climatology for the total electron content in the ionosphere
Authors: Scharroo Remko , Smith Walter H. F.
Published: October 2010

The total electron content (TEC) in the ionosphere is an important factor in the propagation of radio waves. Since 1998 the coverage global positioning system (GPS) observations has been sufficient to monitor the TEC globally. We have used the global ionosphere maps provided by the Jet Propulsion Laboratory to devise a new ionosphere climatology (NIC09). The climatology fits the GPS maps to 4.5 TECU, more than twice as well as the IRI2007 climatology. The use of the global mean TEC as the input parameter reduces scaling errors and long‐term mean errors in the model. For climatic studies of sea level measured by satellite radar altimeters, it is necessary to go back before 1998. During the earlier years of radar altimetry, we use TOPEX dual‐frequency altimeter data to reconstruct the global mean TEC or use the solar radio flux (F10.7) as a proxy. The comparison of dual‐frequency altimeter data with the GPS maps demonstrated that about 8% of the TEC extends above 1350 km and about 14% above 800 km. The root mean square error of the NIC09 climatology was found to be approximately 18% of the TEC, compared to 14% for the GPS TEC maps, and 35% for IRI2007.
Long‐term slip history discriminates among occurrence models for seismic hazard assessment
Authors: Fitzenz D. D. , Ferry M. A. , Jalobeanu A.
Published: October 2010

Today, the probabilistic seismic hazard assessment (PSHA) community relies on stochastic models to compute occurrence probabilities for large earthquakes. Considerable efforts have been devoted to extracting information from long catalogs of large earthquakes based on instrumental, historical, archeological and paleoseismological data. However, the models remain only and insufficiently constrained by these rare single‐slip event data. Therefore, the selection of the models and their respective weights necessarily involves ruling by a panel of experts. Since cumulative slip data with high temporal and spatial resolution are now available, we propose a new approach to incorporate these pieces of evidence of mid‐ to long‐term fault behavior into PSHA: the Cumulative Offset‐Based Bayesian Recurrence Analysis (COBBRA). For the Dead Sea Fault, our method provides weights to the competing recurrence and rupture models, allows time‐independent models to be ruled out, and provides a means to compute the cumulative probability of occurrence for the next full‐segment event reflecting all available data.
Elasticity of AlFeO3 and FeAlO3 perovskite and post‐perovskite from first‐principles calculations
Authors: Caracas R.
Published: October 2010

We use state‐of‐the‐art ab initio calculations based on the generalized gradient approximation of the density functional theory in the planar augmented wavefunction formalism to determine the elastic constants tensor of perovskite and post‐perovskite with formulas AlFeO3 and FeAlO3 in which Fe or Al respectively occupy only octahedral sites, for the stable magnetic configurations. The phase transition between perovskite and post‐perovskite is associated with a site exchange, during which Fe from the inter‐octahedral site in perovskite moves into the octahedral site in post‐perovskite. Following this transition path the elastic moduli show positive jumps, considerably larger than for MgSiO3. The phase transition is marked by a positive jump of 0.04 km/s (0.33%) in the velocity of the compressional waves and by a negative jump of −0.15 km/s (−1.87%) in shear wave velocity. We find that the effects of the Mg + Si <=> Al + Fe substitution on the seismic properties of MgSiO3 perovskite and post‐perovskite depend on the crystallography of the substitution, namely the position the exchanged cations take in the structure.
Electron density and temperature measurements in the cold plasma environment of Titan: Implications for atmospheric escape
Authors: Edberg N. J. T. , Wahlund J.‐E. , Ågren K. , Morooka M. W. , Modolo R. , Bertucci C. , Dougherty M. K.
Published: October 2010

We present electron temperature and density measurements of Titan's cold ionospheric plasma from the Langmuir probe instrument on Cassini from 52 flybys. An expression of the density as a function of temperature is presented for altitudes below two Titan radii. The density falls off exponentially with increased temperature as log(ne) = −2.0log(Te) + 0.6 on average around Titan. We show that this relation varies with location around Titan as well as with the solar illumination direction. Significant heating of the electrons appears to take place on the night/wake side of Titan as the density‐temperature relation is less steep there. Furthermore, we show that the magnetospheric ram pressure is not balanced by the thermal and magnetic pressure in the topside ionosphere and discuss its implications for plasma escape. The cold ionospheric plasma of Titan extends to higher altitudes in the wake region, indicating the loss of atmosphere down the induced magnetospheric tail.
Enhanced signature of solar variability in Eurasian winter climate
Authors: Woollings T. , Lockwood M. , Masato G. , Bell C. , Gray L.
Published: October 2010

We demonstrate that open solar flux (Fs, derivable from geomagnetic data) exhibits stronger correlations with atmospheric circulation variations than conventionally‐used measures of solar activity. The circulation anomalies are particularly enhanced over the North Atlantic/Eurasian sector, where there are large changes in the occurrence of blocking and the winter mean surface temperature differs by several degrees between high‐ and low‐solar terciles. The relationship is stronger and simpler for Fs, being more linear between high‐ and low‐solar winters. While the circulation anomalies strongly resemble the North Atlantic Oscillation they also extend deeper into Eurasia, especially in high‐solar conditions. This distinct signature may be useful for the detection and attribution of observed changes and also the identification of dynamical mechanisms.
A relation between lava discharge rate, thermal insulation, and flow area set using lidar data
Authors: Harris Andrew , Favalli Massimiliano , Steffke Andrea , Fornaciai Alessandro , Boschi Enzo
Published: October 2010

A simple linear relation can be used to link time averaged discharge rate (TADR) and lava flow area (A). The relation applies to given insulation conditions, as described by the characteristic flow surface temperature (Te), and will vary from case‐to‐case depending on rheological and topographic influences on flow spreading. Most flows have insulation conditions that change through time, modifying the relationship between TADR and area as insulation conditions evolve. Using lidar data we can define TADR, the flow area that the discharge feeds and Te, allowing generation of a case‐specific relation to convert satellite‐data‐derived flow areas to TADR. For Etna's 2006 lava flow field we obtain a relation whereby TADR = 5.6 × 10−6 A for well insulated conditions (Te = 100°C) and TADR = 1.5 × 10−4 A for poorly insulated conditions (Te = 600°C).
Estimating the climate impact of linear contrails using the UK Met Office climate model
Authors: Rap Alexandru , Forster Piers M. , Haywood James M. , Jones Andy , Boucher Olivier
Published: October 2010

The HadGEM2 global climate model is employed to investigate some of the linear contrail effects on climate. Our study parameterizes linear contrails as a thin layer of aerosol. We find that at 100 times the air traffic of year 2000, linear contrails would change the equilibrium global‐mean temperature by +0.13 K, corresponding to a climate sensitivity of 0.3 K/(Wm−2) and a climate efficacy of 31% (significantly smaller than the only previously published estimate of 59%). Our model suggests that contrails cause a slight warming of the surface and, as noted by most global warming modelling studies, land areas are affected more than the oceans. Also, unlike the contrail coverage and radiative forcing, the contrail temperature change response is not geographically correlated with air traffic patterns. In terms of the contrail impact on precipitation, the main feature is the northern shift of the Inter‐Tropical Convergence Zone. Finally, our model strongly indicates that the contrail impact on both the diurnal temperature range and regional climate is significantly smaller than some earlier studies suggested.
In situ observations of the effect of a solar wind compression on Saturn's magnetotail
Authors: Jackman C. M. , Arridge C. S. , Slavin J. A. , Milan S. E. , Lamy L. , Dougherty M. K. , Coates A. J.
Published: October 2010

In this paper we explore the dynamic response of Saturn's magnetotail to an episode of solar wind compression that took place while Cassini was sampling Saturn's nightside equatorial magnetosphere in 2006. Following an initial increase in solar wind dynamic pressure the magnetosphere was compressed, but over several subsequent days the flaring of the tail increased as open flux built up in the tail lobes. Several days later the current sheet was displaced southward from its previously hinged position, and magnetic signatures consistent with the passage of a plasmoid were observed. Concurrently, Saturn's kilometric radio emissions were enhanced and the spectrum displayed a continuous extension to lower frequency, corresponding to radio sources detected at higher altitudes. We suggest that all of the above features are a common consequence of the impact of a solar wind compression on Saturn's magnetosphere.
What can be learned from the absence of auroral X‐ray emission from Saturn?
Authors: Hui Yawei , Cravens Thomas E. , Ozak Nataly , Schultz David R.
Published: October 2010

To understand the origin and magnitude of the present upper limit observations of Saturn's auroral X‐ray emission, we use simple models based on the mechanism that leads to analogous emission at Jupiter, charge transfer between ion precipitation and atmospheric gas. Several putative sources and characteristics of the precipitation are considered, namely, (1) highly charged solar wind ions with additional acceleration and (2) ambient, thermal ion population originating, for example, from Saturn's satellites, and then accelerated to high energies. Estimates obtained for each of these sources show the need for acceleration, either to focus the highly charged solar wind ions into the atmosphere or to enable stripping of the initially low‐charge state ambient ions to higher charges. The former yields a constraint on the existing accelerating potentials present at Saturn but can only account for about a tenth of the observed upper limit to the auroral luminosity, while the latter requires extremely low limits on the area (i.e., less than 100 km2) over which field‐aligned potentials are active and needed to produce the acceleration to generate the observational upper limit on the X‐ray luminosity. We therefore narrow the range of possible ion sources, the accelerating potentials required that are consistent with the present understanding of the magnetosphere, and model upper limit of X‐ray emission from ion precipitation.