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The power of micro-arcsecond (μas) astrometry is about to be unleashed. ESA's Gaia mission, now headed towards the end of the first year of routine science operations, will soon fulfil its promise for revolutionary science in countless aspects of Galactic astronomy and astrophysics. The potential of Gaia position measurements for important contributions to the astrophysics of planetary systems is huge. We focus here on the expectations for detection and improved characterization of ‘young’ planetary systems in the neighborhood of the Sun using a combination of Gaia μas astrometry and direct imaging techniques.
This paper considers four alternative sets of actions that a pilot may use to recover an aeroplane from the stall. These actions: those published by the UK CAA and the US FAA, as well as a power delayed sequence and a pitch delayed sequence, were evaluated on 14 single engine piston aeroplane types. In a limited number of types (five in cruise configuration, two in landing configuration) the pitch delayed recovery gave a safe response and least height loss, but in a greater number of types (six and eight in cruise and landing configurations respectively) it resulted in further post-stall uncommanded motion. The other sets of actions all gave a consistent recovery from the stall, but the least height loss in recovery was also consistently the CAA sequence of simultaneous full power and nose-down pitching input, which normally resulted in approximately two thirds the height loss of the FAA’s pitch first then power method, which in turn resulted in about 90% of the height loss of the trialled power delayed recovery. Additionally the CAA recovery gave the least variation in height loss during stall recovery. It was also found that all of the aeroplane types evaluated except for one microlight aeroplane of unusual design, displayed a pitch-up with increased power in the normal (pre-stall) flight regime. Reducing this to separate components it was therefore shown that pitch control is of primary importance and should be used to provide immediate stall recovery. The thrust control can additionally be used as early as possible to minimise height loss, but if the thrust control is used before the pitch control in the stall or post-stall flight regime, there is some risk of subsequent loss of control. Finally, from the discussion on stall recovery methods, questions for Regulatory Authorities are put forward that should address the current practices.
The aerodynamic flow conditions on wings and tail surfaces due to the rotational motion of a spinning aeroplane have been investigated in a full-scale spin flight research programme at the Brunel Flight Safety Laboratory. The wing upper surface vortex has been visualised using smoke and tufts on the wing of a Slingsby Firefly. The flow structures on top of both wings, and on top of the horizontal tail surfaces, have also been studied on a Saab Safir. The development of these rotational flow effects has been related to the spin motion and the effect on the spin dynamics has been studied and discussed. Evidence suggests that the turbulent wake from the wing upper surface vortex impinges the tail of the aircraft during the spin entry. It is hypothesised that the turbulent flow structure on the outside upper wing surface is due to additional accelerations induced by the rotational motion of the aeroplane. Furthermore, the lightening in stick force during spin entry and the apparent increase in push force required for spin recovery corresponds to the observed change in flow condition on the horizontal tail. The difference in pressure on the upper and lower horizontal tail surfaces have been measured using differential pressure sensors, and the result corresponds both with the observed flow conditions and earlier research results from NASA.
Next year the second generation instrument SPHERE will begin science operations at the Very Large Telecope (ESO). This instrument will be dedicated to the search for exoplanets through the direct imaging techniques, with the new generation extreme adaptive optics. In this poster, we present the performances of one of the focal instruments, the Infra-Red Dual-beam Imaging and Spectroscopy (IRDIS). All the results have been obtained with tests in laboratory, simulating the observing conditions in Paranal. We tested several configurations using the sub-system Integral Field Spectrograph (IFS) in parallel and simulating long coronographic exposures on a star, calibrating instrumental ghosts, checking the performance of the adaptive optics system and reducing data with the consortium pipeline. The contrast one can reach with IRDIS is of the order of 10−6 at 0.5 arcsec separation from the central star.
We review spectroscopic evidence of multiple stellar populations in globular clusters. First, we lay down the basic data: the C-N, Na-O, Mg-Al anti-correlations among red giants and main sequence stars, and discuss how they appear to be general properties of globular clusters, in spite of cluster-to-cluster differences. We will then describe what is currently known about He from spectroscopy. We will then present the implications and current observations for the interpretation of the horizontal branches, showing that the multiple population phenomenon is strongly related to the distribution of stars along them. We will briefly mention the spectroscopic evidence related to some less understood cases, like the clusters with multiple subgiant branches. Finally, we summarize the relation between multiple populations and general properties for globular clusters, and their implications for the formation scenario.
Motion and airflow during a two-turn erect spin of an aerobatic light aeroplane have been analysed. An alternative method, based upon camera tracking, has been used to capture the spin motion. A CAD model of the Slingsby Firefly was created using laser scanning. Formation flights with a helicopter have been flown and high-quality video and still imagery obtained. Camera tracking has produced data and unique illustrations of the spinning Slingsby. To further investigate the aerodynamic flow of a spinning aeroplane, full-scale, flow visualisation flights have been flown using wool tufts on wing, fuselage and empennage. Tufts indicate that a large vortex forms on the outside wing. The spanwise motion of this vortex has been studied and related to the spin motion. Furthermore, tufts on the horizontal tail indicate the presence of a leading edge vortex with the flow mainly in a spanwise outwards direction. The effects observed are clearly three dimensional and time dependent. Finally, it is discussed how this new knowledge does not correspond with the spin theories of the past.
The frequency of planets in binaries is an important issue in the field of extrasolar planet studies, because of its relevance in the estimate of the global planet population of our Galaxy and the clues it can give to our understanding of planet formation and evolution.
Here we present an update of the results discussed in Bonavita & Desidera (2007) (hereafter BD07), where we reported the outcomes of our literature search for binaries and multiple systems among the sample with uniform detectability (UD) defined by Fischer & Valenti (2005) (hereafter FV05).
We present an analysis of how bisectors of spectral lines
for a few stars
observed during the high-accuracy radial-velocity planet survey ongoing
at the Telescopio Nazionale Galileo (TNG) using the
Galileo High Resolution
Spectrograph (Spettrografo Alta Risoluzione Galileo, SARG),
and discuss their relation with differential radial velocities. The iodine cell
lines employed in the radial velocity measurements were used to improve the wavelength
calibration and then removed before bisector analysis. The line bisectors were then
computed from average absorption profiles obtained by cross-correlation of the stellar
spectra with a mask made from suitable lines of a solar catalog. Bisector velocity
spans were determined and the run of bisector velocity span against radial velocity
was studied to search for correlations between line asymmetries and radial velocity
variations. We present an analysis of spectra of HD 216122B that show a slight contamination
likely to be due to a stellar companion, and an analysis of spectra of HD 76036A, a case where the
line bisectors are useful for improving the RV measurements. These systems are part of
a survey sample being observed with adaptive optics (AdOpt at the TNG since 2006) in an
attempt to visually resolve stellar companions.
We present the radial velocity planet search in moderately wide binaries
with similar components (twins) ongoing at Telescopio Nazionale Galileo (TNG) using the
Galileo High Resolution
Spectrograph (Spettrografo Alta Risoluzione Galileo, SARG).
We discuss the sample selection, the observing and
procedures, the main results of the radial velocity monitoring and the
implications in terms of planet frequency in binary systems. We also briefly
discuss the second major science goal of the SARG survey, the search for
abundance anomalies caused by the ingestion of planetary material by the
central star. Finally, we present some preliminary conclusions regarding the
frequency of planets in binary systems.
The available results of deep imaging searches for planetary companions around nearby stars provide us useful constraints on the frequencies of giant planets in very wide orbits.
Here we present some preliminary results of the Monte Carlo simulation which compare the published detection limits with the generated planetary masses and orbital parameters.
This allow us to consider the impications of the null detection, which comes from the direct imaging techniques, on the distributions of mass and semimajor axis derived from the results of the other search techniques and also to check the agreement of the observations with the available planetary formation models.
We derive abundances of Fe, Na, O, α and s-elements from GIRAFFE@VLT spectra for more than 200 red giant stars in the Milky Way satellite ω Centauri. Our preliminary results are that: (i) we confirm that ω Centauri exhibits large star-to-star metallicity variation (~1.4 dex); (ii) the metallicity distribution reveals the presence of at least five stellar populations with different [Fe/H]; (iii) a distinct Na-O anticorrelation is clearly observed for the metal-poor and metal-intermediate stellar populations while apparently the anticorrelation disappears for the most metal rich populations. Interestingly the Na level grows with iron.
The single stable isotope of beryllium is a pure product of cosmic-ray spallation in the ISM. Assuming that the cosmic-rays are globally transported across the Galaxy, the beryllium production should be a widespread process and its abundance should be roughly homogeneous in the early-Galaxy at a given time. Thus, it could be useful as a tracer of time. In an investigation of the use of Be as a cosmochronometer and of its evolution in the Galaxy, we found evidence that in a log(Be/H) vs. [α/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined. We also found evidence that the star formation rate was lower in the outer regions of the thick disk, pointing towards an inside-out formation.
Beryllium stellar abundances were suggested to be a good tracer of time in the early Galaxy. In an investigation of its use as a cosmochronometer, using a large sample of local halo and thick-disk dwarfs, evidence was found that in a log(Be/H) vs. [α/Fe] diagram the halo stars separate into two components. One is consistent with predictions of evolutionary models while the other is chemically indistinguishable from the thick-disk stars. This is interpreted as a difference in the star formation history of the two components and suggests that the local halo is not a single uniform population where a clear age-metallicity relation can be defined.
We study the stability of the cold-plasma dispersion relation for circularly polarized waves in a plasma composed of an ion background and an ion beam. The presence of the beam introduces a resonant branch into the dispersion relation for right-hand-polarized waves propagating in the direction of the external magnetic field, which, for V>Vφ, has negative energy (here V is the beam velocityVφ is the wave phase velocity). Therefore this branch may give rise to explosive instabilities when the waves experience parametric decays. It is shown graphically that resonant right-hand-polarized and non-resonant left-hand-polarized waves, propagating parallel to the external magnetic field, can be unstable. It is also shown that the instability region can extend to large frequencies and wavenumnbers, and that the instability regions have a band structure. The parametric dependence of instability thresholds and marginal modes is also studied.
The Bologna Open Cluster Chemical Evolution (BOCCE) project is intended to study the disk of our Galaxy using open clusters as tracers of its properties. We are building a large sample of clusters, deriving homogeneously their distance, age, reddening, and detailed chemical composition. Among our sample we have several objects more metal-rich than the Sun and we present here first results of the analysis for NGC 6819, IC 4651, NGC 6134, NGC 6791, and NGC 6253, the last two being the most metal-rich open clusters known.
We use Beryllium to investigate star formation in the early Galaxy. Be has been demonstrated to be a good indicator of time in these early epochs. By analyzing the so-far largest sample of halo and thick disk metal poor stars, we find a clear scatter in Be for a given value of [Fe/H] and [O/H]. The scatter is very pronounced for Halo stars, while it is marginal for thick disk stars. Our halo stars separate in the [α/Fe] - Be diagram, showing two main branches: one indistinguishable from the thick disk stars, and one with lower [α/Fe] ratio. The stars belonging to this branch are characterized by highly eccentric orbits and small perigalactic radius (Rmin). Their kinematics are consistent with an accreted component.
We present an analysis of the HD planetary system based on a photometric transit dataset and radial velocities obtained on 3 December 2007. We also present limits on the presence of close stellar companions based on high resolution images.
The extreme contrast in mass and luminosity between the extra-solar planets and their host stars make detailed studies of these planets very challenging. In particular, direct observations of extra-solar planets is still beyond the capabilities of the currently available instrumentation, save for perhaps a few extreme cases of very young and massive planets at large distances from the central star. While progress in instrumentation might allow significant progress in detection capabilities either with the 8 and 10-m ground-based telescopes (Planet Finder instruments on the VLT and Gemini) or with the next generation space telescope (JWST), imaging of extra-solar planets over a wide range of parameters, and possibly down to terrestrial planets, will require extremely large ground-based telescopes like OWL or dedicated space instrumentation (TPF or Darwin for instance). We outline here the scientific objectives of EPICS, the OWL Earth-like Planet Imager and Spectrograph, summarize the corresponding high level requirements, present the foreseen observing modes and give a first estimate of its performance.
Direct detection and spectral characterization of extrasolar planets is one of the most exciting but also one of the most challenging area in modern astronomy. For its second generation instrumentation on the VLT, ESO has supported two phase A studies for a so-called “Planet Finder” dedicated instrument. Based on the results of these two studies, a unique instrument is now considered for first light in early 2010, including a powerful extreme adaptive optics system, various coronagraphs, an infrared differential imaging camera, an infrared integral field spectrograph and a visible differential polarimeter. We will briefly summarize the science objectives and requirements, describe the proposed conceptual design and discuss the main limitations and corresponding instrumental issues of such a system. We will also derive the expected performance of the proposed Planet Finder and present the project organization.
This paper presents the scientific case for a next generation adaptive optics instrument at the VLT, temporarily named “Planet Finder”, that is aimed at detecting and characterizing extrasolar planets through the direct analysis of their emitted photons in the visible and at near-IR wavelengths. We discuss the observational niche of such an instrument to have first light in 2010, in complement to other planet search methods. To improve the efficiency (and consistency) of the search for planets with the PF, the observations will need to be organized in the form of an extensive survey of hundreds of nearby stars, predicted outputs of which are also described here. This summarizes the study phase of the instrument, conducted by two competitive teams and the recent merging of both studies, regarding the scientific impact of Planet Finder.