Mode visibilities in rapidly rotating stars

in Astronomy and Astrophysics (2013), 550

Context: Mode identification is a crucial step to comparing observed frequencies with theoretical ones, but has proven to be difficult in rapidly rotating stars. Aims: To further constrain mode ... [more ▼]

Context: Mode identification is a crucial step to comparing observed frequencies with theoretical ones, but has proven to be difficult in rapidly rotating stars. Aims: To further constrain mode identification, we aim to accurately calculate mode visibilities and amplitude ratios in rapid rotators. Methods: We derive the relevant equations for calculating mode visibilities in different photometric bands while fully taking into account the geometric distortion from both the centrifugal deformation and the pulsation modes, the variations in effective gravity, and an approximate treatment of the temperature variations. These equations are then applied to 2D oscillation modes, calculated using the TOP code, in fully distorted 2D models based on the SCF method. The specific intensities come from a grid of Kurucz atmospheres, thereby taking into account limb and gravity darkening. Results: We obtain mode visibilities and amplitude ratios for 2 M_{\odot} models rotating at 0 to 80 % of the critical rotation rate. These calculations confirm previous results, such as the increased visibility of chaotic modes, the simpler frequency spectra of pole-on stars, or the dependence of amplitude ratios on inclination and azimuthal order. In addition, the geometric shape of the star reduces the contrast between pole-on and equator-on visibilities of island modes. We also show that modes with similar (ell, |m|) values frequently have similar amplitude ratios, even in the most rapidly rotating models. [less ▲]

A Model Based Study of Carbon Fluxes at Ten European Forest Sites

in Valentini, Riccardo (Ed.) Fluxes of Carbon, Water and Energy of European Forests (2003)

Model calculations of the Sivers function satisfying the Burkardt sum rule

in Physical Review D - Particles, Fields, Gravitation and Cosmology (2009), 79(7),

It is shown that, at variance with previous analyses, the MIT bag model can explain the available data of the Sivers function and satisfies the Burkardt sum rule to a few percent accuracy. The agreement ... [more ▼]

It is shown that, at variance with previous analyses, the MIT bag model can explain the available data of the Sivers function and satisfies the Burkardt sum rule to a few percent accuracy. The agreement is similar to the one recently found in the constituent quark model. Therefore, these two model calculations of the Sivers function are in agreement with the present experimental and theoretical wisdom. © 2009 The American Physical Society. [less ▲]

Model complexity and performance: How far can we simplify?

in Progress in Oceanography (2006), 70(1), 27-57

Handling model complexity and reliability is a key area of research today. While complex models containing sufficient detail have become possible due to increased computing power, they often lead to too ... [more ▼]

Handling model complexity and reliability is a key area of research today. While complex models containing sufficient detail have become possible due to increased computing power, they often lead to too much uncertainty. On the other hand, very simple models often crudely oversimplify the real ecosystem and can not be used for management purposes. Starting from a complex and validated 1D pelagic ecosystem model of the Ligurian Sea (NW Mediterranean Sea), we derived simplified aggregated models in which either the unbalanced algal growth, the functional group diversity or the explicit description of the microbial loop was sacrificed. To overcome the problem of data availability with adequate spatial and temporal resolution, the outputs of the complex model are used as the baseline of perfect knowledge to calibrate the simplified models. Objective criteria of model performance were used to compare the simplified models' results to the complex model output and to the available data at the DYFAMED station in the central Ligurian Sea. We show that even the simplest (NPZD) model is able to represent the global ecosystem features described by the complex model (e.g. primary and secondary productions, particulate organic matter export flux, etc.). However, a certain degree of sophistication in the formulation of some biogeochemical processes is required to produce realistic behaviors (e.g. the phytoplankton competition, the potential carbon or nitrogen limitation of the zooplankton ingestion, the model trophic closure, etc.). In general, a 9 state-variable model that has the functional group diversity removed, but which retains the bacterial loop and the unbalanced algal growth, performs best. (C) 2006 Elsevier Ltd. All rights reserved. [less ▲]

Model emulsion systems

Conference (1995, April)

Model Extension Facilitates Parameter Estimation for Kinetic Reaction Networks

Poster (2007, September)

Model Extension Facilitates Parameter Estimation for Kinetic Reaction Networks

Poster (2007, September)

A model for optimal sea-river shipping management

in Proceedings of the Third Research Roundtable Conference on Shortsea Shipping (1996, June)

A model for ternary projective relations between regions

in Lecture Notes in Computer Science (2004)

A model for the generalized parton distribution of the pion

in AIP Conference Proceedings (2005), 756