An orbital period of 0.94days for the hot-Jupiter planet WASP-18b

The `hot Jupiters' that abound in lists of known extrasolar planets are thought to have formed far from their host stars, but migrate inwards through interactions with the proto-planetary disk from which they were born, or by an alternative mechanism such as planet-planet scattering. The hot Jupiters closest to their parent stars, at orbital distances of only ~0.02 astronomical units, have strong tidal interactions, and systems such as OGLE-TR-56 have been suggested as tests of tidal dissipation theory. Here we report the discovery of planet WASP-18b with an orbital period of 0.94days and a mass of ten Jupiter masses (10MJup), resulting in a tidal interaction an order of magnitude stronger than that of planet OGLE-TR-56b. Under the assumption that the tidal-dissipation parameter Q of the host star is of the order of 106, as measured for Solar System bodies and binary stars and as often applied to extrasolar planets, WASP-18b will be spiralling inwards on a timescale less than a thousandth that of the lifetime of its host star. Therefore either WASP-18 is in a rare, exceptionally short-lived state, or the tidal dissipation in this system (and possibly other hot-Jupiter systems) must be much weaker than in the Solar System.

Development and validation of a dried blood spot-LC-APCI-MS assay for estimation of canrenone in paediatric samples

A selective and sensitive liquid chromatography (LC)-atmospheric pressure chemical ionisation (APCI)-mass spectroscopic (MS) assay of canrenone has been developed and validated employing Dried Blood Spots (DBS) as the sample collection medium. DBS samples were prepared by applying 30 mu l of spiked whole blood onto Guthrie cards. A 6 mm disc was punched from the each DBS and extracted with 2 ml of methanolic solution of 17 alpha-methyltestosterone (Internal Standard). The methanolic extract was evaporated to dryness and reconstituted in acetonitrile:water (1:9, v/v). The reconstituted solution was further subjected to solid phase extraction using HLB cartridges. Chromatographic separation was achieved using Waters Sunfire C18 reversed-phase column using isocratic elution, followed by a high organic wash to clear late eluting/highly retained components. The mobile phase consisted of methanol:water (60:40, v/v) pumped at a flow rate of 0.3 ml/min. LC-APCI-MS detection was performed in the selected-ion monitoring (SIM) mode using target ions at m/z 341.1 and 303.3 for canrenone and internal standard respectively. The selectivity of the method was established by analysing DBS samples from 6 different sources (individuals). The calibration curve for canrenone was found to be linear over 25-1000 ng/ml (r >0.994). Accuracy (% RE) and precision (% CV) values for within and between day were

WASP-24 b: A New Transiting Close-in Hot Jupiter Orbiting a Late F-star

We report the discovery of a new transiting close-in giant planet, WASP-24 b, in a 2.341 day orbit, 0.037 AU from its F8-9 type host star. By matching the star's spectrum with theoretical models, we infer an effective temperature T eff = 6075 ± 100 K and a surface gravity of log g = 4.15 ± 0.10. A comparison of these parameters with theoretical isochrones and evolutionary mass tracks places only weak constraints on the age of the host star, which we estimate to be 3.8+1.3 –1.2 Gyr. The planetary nature of the companion was confirmed by radial velocity measurements and additional photometric observations. These data were fit simultaneously in order to determine the most probable parameter set for the system, from which we infer a planetary mass of 1.071+0.036 –0.038 M Jup and radius 1.3+0.039 –0.037 R Jup.

Hot Electrons Transverse Refluxing in Ultraintense Laser-Solid Interactions

We have analyzed the coupling of ultraintense lasers (at similar to 2 X 1019 W/cm(2)) with solid foils of limited transverse extent (similar to 10 s of mu m) by monitoring the electrons and ions emitted from the target. We observe that reducing the target surface area allows electrons at the target surface to be reflected from the target edges during or shortly after the laser pulse. This transverse refluxing can maintain a hotter, denser and more homogeneous electron sheath around the target for a longer time. Consequently, when transverse refluxing takes places within the acceleration time of associated ions, we observe increased maximum proton energies (up to threefold), increased laser-to-ion conversion efficiency (up to a factor 30), and reduced divergence which bodes well for a number of applications.

Acoustic solitary waves in dusty and/or multi-ion plasmas with cold, adiabatic, and hot constituents

Large nonlinear acoustic waves are discussed in a four-component plasma, made up of two superhot isothermal species, and two species with lower thermal velocities, being, respectively, adiabatic and cold. First a model is considered in which the isothermal species are electrons and ions, while the cooler species are positive and/or negative dust. Using a Sagdeev pseudopotential formalism, large dust-acoustic structures have been studied in a systematic way, to delimit the compositional parameter space in which they can be found, without restrictions on the charges and masses of the dust species and their charge signs. Solitary waves can only occur for nonlinear structure velocities smaller than the adiabatic dust thermal velocity, leading to a novel dust-acoustic-like mode based on the interplay between the two dust species. If the cold and adiabatic dust are oppositely charged, only solitary waves exist, having the polarity of the cold dust, their parameter range being limited by infinite compression of the cold dust. However, when the charges of the cold and adiabatic species have the same sign, solitary structures are limited for increasing Mach numbers successively by infinite cold dust compression, by encountering the adiabatic dust sonic point, and by the occurrence of double layers. The latter have, for smaller Mach numbers, the same polarity as the charged dust, but switch at the high Mach number end to the opposite polarity. Typical Sagdeev pseudopotentials and solitary wave profiles have been presented. Finally, the analysis has nowhere used the assumption that the dust would be much more massive than the ions and hence, one or both dust species can easily be replaced by positive and/or negative ions and the conclusions will apply to that plasma model equally well. This would cover a number of different scenarios, such as, for example, very hot electrons and ions, together with a mix of adiabatic ions and dust (of either polarity) or a very hot electron-positron mix, together with a two-ion mix or together with adiabatic ions and cold dust (both of either charge sign), to name but some of the possible plasma compositions.

WASP-21b: a hot-Saturn exoplanet transiting a thick disc star

We report the discovery of WASP-21b, a new transiting exoplanet discovered by the Wide Angle Search for Planets (WASP) Consortium and established and characterized with the FIES, SOPHIE, CORALIE and HARPS fiber-fed echelle spectrographs. A 4.3-d period, 1.1% transit depth and 3.4-h duration are derived for WASP-21b using SuperWASP-North and high precision photometric observations at the Liverpool Telescope. Simultaneous fitting to the photometric and radial velocity data with a Markov Chain Monte Carlo procedure leads to a planet in the mass regime of Saturn. With a radius of 1.07 RJup and mass of 0.30 MJup, WASP-21b has a density close to 0.24 ?Jup corresponding to the distribution peak at low density of transiting gaseous giant planets. With a host star metallicity [Fe/H] of -0.46, WASP-21b strengthens the correlation between planetary density and host star metallicity for the five known Saturn-like transiting planets. Furthermore there are clear indications that WASP-21b is the first transiting planet belonging to the thick disc.

Spin-orbit angle measurements for six southern transiting planets. New insights into the dynamical origins of hot Jupiters

Context. Several competing scenarios for planetary-system formation and evolution seek to explain how hot Jupiters came to be so close to their parent stars. Most planetary parameters evolve with time, making it hard to distinguish between models. The obliquity of an orbit with respect to the stellar rotation axis is thought to be more stable than other parameters such as eccentricity. Most planets, to date, appear aligned with the stellar rotation axis; the few misaligned planets so far detected are massive (> 2 MJ). Aims: Our goal is to measure the degree of alignment between planetary orbits and stellar spin axes, to search for potential correlations with eccentricity or other planetary parameters and to measure long term radial velocity variability indicating the presence of other bodies in the system. Methods: For transiting planets, the Rossiter-McLaughlin effect allows the measurement of the sky-projected angle ß between the stellar rotation axis and a planet's orbital axis. Using the HARPS spectrograph, we observed the Rossiter-McLaughlin effect for six transiting hot Jupiters found by the WASP consortium. We combine these with long term radial velocity measurements obtained with CORALIE. We used a combined analysis of photometry and radial velocities, fitting model parameters with the Markov Chain Monte Carlo method. After obtaining ß we attempt to statistically determine the distribution of the real spin-orbit angle ?. Results: We found that three of our targets have ß above 90°: WASP-2b: ß = 153°+11-15, WASP-15b: ß = 139.6°+5.2-4.3 and WASP-17b: ß = 148.5°+5.1-4.2; the other three (WASP-4b, WASP-5b and WASP-18b) have angles compatible with 0°. We find no dependence between the misaligned angle and planet mass nor with any other planetary parameter. All six orbits are close to circular, with only one firm detection of eccentricity e = 0.00848+0.00085-0.00095 in WASP-18b. No long-term radial acceleration was detected for any of the targets. Combining all previous 20 measurements of ß and our six and transforming them into a distribution of ? we find that between about 45 and 85% of hot Jupiters have ? > 30°. Conclusions: Most hot Jupiters are misaligned, with a large variety of spin-orbit angles. We find observations and predictions using the Kozai mechanism match well. If these observational facts are confirmed in the future, we may then conclude that most hot Jupiters are formed from a dynamical and tidal origin without the necessity to use type I or II migration. At present, standard disc migration cannot explain the observations without invoking at least another additional process.