Internal rapid rotation and its implications for stellar structure and pulsations

Massive and intermediate mass stars play a crucial role in astrophysics. Indeed, massive stars are the main producers of heavy elements, explode in supernovae at the end of their short lifetimes, and may be the progenitors of gamma ray bursts. Intermediate mass stars, although not destined to explode in supernovae, display similar phenomena, are much more numerous, and have some of the richest pulsation spectra. A key to understanding these stars is understanding the effects of rapid rotation on their structure and evolution. These effects include centrifugal deformation and gravity darkening which can be observed immediately, and long terms effects such as rotational mixing due to shear turbulence, which prolong stellar lifetime, modify chemical yields, and impact the stellar remnant at the end of their lifetime. In order to understand these effects, a number of models have been and are being developed over the past few years. These models lead to increasingly sophisticated predictions which need to be tested through observations. A particularly promising source of constraints is seismic observations as these may potentially lead to detailed information on their internal structure. However, before extracting such information, a number of theoretical and observational hurdles need to be overcome, not least of which is mode identification. The present proceedings describe recent progress in modelling these stars and show how an improved understanding of their pulsations, namely frequency patterns, mode visibilities, line profile variations, and mode excitation, may help with deciphering seismic observations.Comment: Proceedings for the CoRoT 3/KASC 7 meeting in Toulous

Influence of observation of true stuttering and self-disclosure on college professors' perception of students who stutter

textResearch has demonstrated that college professors rate hypothetical students who stutter more negatively than college students who do not stutter. To date, no studies have explored perceptions when observing actual students who stutter. Furthermore, self-disclosure has been proven to influence listener perception. The primary purpose of the present study is to investigate the role self-disclosure has on the perception of college professors.Communication Sciences and Disorder

Vibration of a flexible pipe conveying viscous pulsating fluid flow

The non-linear equations of motion of a flexible pipe conveying unsteadily flowing fluid are derived from the continuity and momentum equations of unsteady flow. These partial di!erential equations are fully coupled through equilibrium of contact forces, the normal compatibility of velocity at the fluid} pipe interfaces, and the conservation of mass and momentum of the transient fluid. Poisson coupling between the pipe wall and fluid is also incorporated in the model. A combination of the finite difference method and the method of characteristics is employed to extract displacements, hydrodynamic pressure and flow velocities from the equations. A numerical example of a pipeline conveying fluid with a pulsating flow is given and discussed

Analysis of the vibration of pipes conveying fluid

The dynamic equilibrium matrix equation for a discretized pipe element containing flowing fluid is derived from the Lagrange principle, the Ritz method and consideration of the coupling between the pipe and fluid. The Eulerian approach and the concept of fictitious loads for kinematic correction are adopted for the analysis of geometrically non-linear vibration. The model is then deployed to investigate the vibratory behaviour of the pipe conveying fluid. The results for a long, simply supported, fluid-conveying pipe subjected to initial axial tensions are compared with experimentally obtained results and those from a linear vibration model

Asteroseismic inversions in the Kepler era: application to the Kepler Legacy sample

In the past few years, the CoRoT and Kepler missions have carried out what is now called the space photometry revolution. This revolution is still ongoing thanks to K2 and will be continued by the Tess and Plato2.0 missions. However, the photometry revolution must also be followed by progress in stellar modelling, in order to lead to more precise and accurate determinations of fundamental stellar parameters such as masses, radii and ages. In this context, the long-lasting problems related to mixing processes in stellar interior is the main obstacle to further improvements of stellar modelling. In this contribution, we will apply structural asteroseismic inversion techniques to targets from the Kepler Legacy sample and analyse how these can help us constrain the fundamental parameters and mixing processes in these stars. Our approach is based on previous studies using the SOLA inversion technique to determine integrated quantities such as the mean density, the acoustic radius, and core conditions indicators, and has already been successfully applied to the 16Cyg binary system. We will show how this technique can be applied to the Kepler Legacy sample and how new indicators can help us to further constrain the chemical composition profiles of stars as well as provide stringent constraints on stellar ages.Comment: To appear in the proceedings of the Kasc 9 Tasc 2 worksho

Hot Electron Bolometer Development for a Submillimeter Heterodyne Array Camera

We are developing Nb diffusion-cooled Hot Electron Bolometers (HEBs) for a large-format array submillimeter camera. We have fabricated Nb HEBs using a new angle deposition process. We have characterized these devices using heterodyne mixing at 20 GHz. We also report on optimizations in the fabrication process that improve device performance.Comment: 2005 International Symposium on Space Terahertz Technolog

Non-adiabatic pulsations in ESTER models

One of the greatest challenges in interpreting the pulsations of rapidly rotating stars is mode identification, i.e. correctly matching theoretical modes to observed pulsation frequencies. Indeed, the latest observations as well as current theoretical results show the complexity of pulsation spectra in such stars, and the lack of easily recognisable patterns. In the present contribution, the latest results on non-adiabatic effects in such pulsations are described, and we show how these come into play when identifying modes. These calculations fully take into account the effects of rapid rotation, including centrifugal distortion, and are based on models from the ESTER project, currently the only rapidly rotating models in which the energy conservation equation is satisfied, a prerequisite for calculating non-adiabatic effects. Non-adiabatic effects determine which modes are excited and play a key role in the near-surface pulsation-induced temperature variations which intervene in multi-colour amplitude ratios and phase differences, as well as line profile variations.Comment: Proceedings for the Joint TASC2 & KASC9 Workshop, Terceira, Azores, 201

Mode identification in rapidly rotating stars from BRITE data

Apart from recent progress in Gamma Dor stars, identifying modes in rapidly rotating stars is a formidable challenge due to the lack of simple, easily identifiable frequency patterns. As a result, it is necessary to look to observational methods for identifying modes. Two popular techniques are spectroscopic mode identification based on line profile variations (LPVs) and photometric mode identification based on amplitude ratios and phase differences between multiple photometric bands. In this respect, the BRITE constellation is particularly interesting as it provides space-based multi-colour photometry. The present contribution describes the latest developments in obtaining theoretical predictions for amplitude ratios and phase differences for pulsation modes in rapidly rotating stars. These developments are based on full 2D non-adiabatic pulsation calculations, using models from the ESTER code, the only code to treat in a self-consistent way the thermal equilibrium of rapidly rotating stars. These predictions are then specifically applied to the BRITE photometric bands to explore the prospects of identifying modes based on BRITE observations.Comment: 8 pages, 3 figures, proceedings of the 3rd BRITE Science Worksho

Vibration analysis of a circular disc backed by a cylindrical cavity

This paper describes the free vibration analysis of a thin disc vibrating and interacting with an acoustic medium contained in a cylindrical duct. The effects of structural-acoustic coupling are studied by means of an analytical-numerical method that is based upon classical theory and the Galerkin method. The coupling effects are discussed, and results obtained from the analysis are compared with corresponding values obtained both experimentally and from a finite element analysis. There is good agreement between the three sets of results