Has a star enough energy to excite the thousand of modes observed with CoRoT?

The recent analyses of the light curves provided by CoRoT have revealed pulsation spectra of unprecedented richness and precision, in particular, thousands of pulsating modes, and a clear distribution of amplitudes with frequency. In the community, some scientists have started doubting about the validity of the classical tools to analyze these very accurate light curves. This work provides the asteroseismic community with answers to this question showing that (1) it is physically possible for a star to excite at a time and with the observed amplitudes such a large number of modes; and (2) that the kinetic energy accumulated in all those modes does not destroy the equilibrium of the star. Consequently, mathematical tools presently applied in the analyses of light curves can a priori be trusted. This conclusion is even more important now, when a large amount of space data coming from Kepler are currently being analyzed. The power spectrum of different stellar cases, and the non-adiabatic code GraCo have been used to estimate the upper limit of the energy per second required to excite all the observed modes, and their total kinetic energy. A necessary previous step for this study is to infer the relative radial pulsational amplitude from the observed photometric amplitude, scaling our linear pulsational solutions to absolute values. The derived upper limits for the required pulsational energy were compared with 1) the luminosity of the star; and 2) the gravitational energy. We obtained that both upper energy limits are orders of magnitude smaller.Comment: 18 pages, 2 figures, accepted by ApJ Letters Dec 15, 200

Modelling turbulent fluxes due to thermal convection in rectilinear shearing flow

We revisit a phenomenological description of turbulent thermal convection along the lines proposed originally by Gough (1965) in which eddies grow solely by extracting energy from the unstably stratified mean state and are subsequently destroyed by internal shear instability. This work is part of an ongoing investigation for finding a procedure to calculate the turbulent fluxes of heat and momentum in the presence of a shearing background flow in stars.Comment: 2 pages, 1 figure, accepted for publication in IAU Symposium 271 "Astrophysical Dynamics: From Galaxies to Stars", Nice, 201

Rare decays and CP violation at B-factories

Recent results on rare B decays from the two B-factories, Belle and BABAR, are presented. The Wilson Coefficients in B → K(∗)l+l− and polarization puzzle in charmless B → V V decays are addressed

Planar Pixel Sensors for the ATLAS tracker upgrade at HL-LHC

The ATLAS Planar Pixel Sensor R&D Project is a collaboration of 17 institutes and more than 80 scientists. Their goal is to explore the operation of planar pixel sensors for the tracker upgrade at the High Luminosity-Large Hadron Collider (HL-LHC). This work will give a summary of the achievements on radiation studies with n-in-n and n-in-p pixel sensors, bump-bonded to ATLAS FE-I3 and FE-I4 readout chips. The summary includes results from tests with radioactive sources and tracking efficiencies extracted from test beam measurements. Analysis results of ${2\cdot10^{16}} \text{n}_{\text{eq}}\text{cm}^{-2}$ and ${1\cdot10^{16}} \text{n}_{\text{eq}}\text{cm}^{-2}$ ($1 \text{MeV}$ neutron equivalent) irradiated n-in-n and n-in-p modules confirm the operation of planar pixel sensors for future applications

Asteroseismology of the Kepler field DBV White Dwarf - It's a hot one!

We present an asteroseismic analysis of the helium atmosphere white dwarf (a DBV) recently found in the field of view of the Kepler satellite. We analyze the 5-mode pulsation spectrum that was produced based on one month of high cadence Kepler data. The pulsational characteristics of the star and the asteroseismic analysis strongly suggest that the star is hotter (29200 K) than the 24900 K suggested by model fits to the low S/N survey spectrum of the object. This result has profound and exciting implications for tests of the Standard Model of particle physics. Hot DBVs are expected to lose over half of their energy through the emission of plasmon neutrinos. Continuous monitoring of the star with the Kepler satellite over the course of 3 to 5 years is not only very likely to yield more modes to help constrain the asteroseismic fits, but also allow us to obtain a rate of change of any stable mode and therefore measure the emission of plasmon neutrinos.Comment: 5 pages, 3 figures, accepted for publication in ApJ

Excitation of stellar p-modes by turbulent convection: 1. Theoretical formulation

Stochatic excitation of stellar oscillations by turbulent convection is investigated and an expression for the power injected into the oscillations by the turbulent convection of the outer layers is derived which takes into account excitation through turbulent Reynolds stresses and turbulent entropy fluctuations. This formulation generalizes results from previous works and is built so as to enable investigations of various possible spatial and temporal spectra of stellar turbulent convection. For the Reynolds stress contribution and assuming the Kolmogorov spectrum we obtain a similar formulation than those derived by previous authors. The entropy contribution to excitation is found to originate from the advection of the Eulerian entropy fluctuations by the turbulent velocity field. Numerical computations in the solar case in a companion paper indicate that the entropy source term is dominant over Reynold stress contribution to mode excitation, except at high frequencies.Comment: 14 pages, accepted for publication in A&

Taxonomy and ecology of the Western Australian Soldier Crab, Mictyris Occidentalis (Crustacea: Decapoda: Brachyura: Mictyridae)

The taxonomy and autoecology of the Western Australian soldier crab, Mictyris occidentalis Unno, 2008 is presented including a new species description, a comprehensive ichnology, sampling methods, an extensive habitat description and a decadal population dynamics study. Such a wide ranging, holistic study has not been carried out for any mictyrid specious previously. In detail, a taxonomy component compares M. occidentalis with congeners, clearly establishing it as a separate species from M. longicarpus to which it was previously referred, and the issues affecting taxonomic classification in the Mictyris genus in general are discussed. A species identification key is provided for the genus. A full suite of ichnological products created by M. occidentalis including cavities, shafts, exit holes, pellets, rosettes, tunnels and pustular structures, is described and related to the behaviour and life stages of the crab from juvenile to adult. The principle of understanding the behaviour of a species before designing sampling strategies is illustrated, using the example of the rapid burrowing escape mechanism employed by M. occidentalis. The habitats of M. occidentalis are described across its entire geographic range encompassing thousands of kilometres of coastline. Factors characterising the soldier crab habitat are investigated from the regional, to large, to local, to micro-geomorphic habitat scale including the abiotic factors of wave energy, tidal level, submergence frequency, the sediment characteristics of grain size, composition, moisture content, salinity and also groundwater salinity. Also, the biotic factors of the densities of sea couch roots and mangrove pneumatophores are considered. A model of the soldier crab habitat is provided for prediction of the presence/absence of soldier crab populations in any particular coastal zone. The results of a 30 year study of the population dynamics of M. occidentalis in King Bay, Dampier Archipelago are presented in which the juvenile recruitment patterns, intra and interannual abundance and size classes of the population and gender composition and size classes of swarms and subsurface population components are determined. Periods of ovigery of M. occidentalis females are compared with those of other mictyrid species. The lifecyle of M. occidentalis is determined to consist of a cryptic infaunal phase for most of the crab’s life followed by an emergent adult stage. Swarms comprise predominantly adult males with most females and all juveniles remaining in the subsurface during a swarm event. The extended period of swarming adults on a tidal flat is explained by the extended period of juvenile recruitment resulting in a continuous series of cohorts reaching maturity and commencing the emergent phase. Environmental management recommendations to conserve populations of M. occidentalis are provided based on a synthesis of the findings of this ecological study