Non-adiabatic Asteroseismology of Near-Main Sequence Variable Stars

Abstract

Abstract. We present in this talk a new linear non-adiabatic pulsation code: MAD 1 . We detail all the possible applications of it in the frame of asteroseismology. By using it, photospheric observables such as multi-color photometric amplitude ratios, phase differences and line profile variations can be determined accurately and confronted with observations. Moreover, MAD enables the precisely analysis of the excitation mechanisms of pulsating stars. Non-adiabatic asteroseismologyIn the superficial layers of a star, the thermal relaxation time is shorter than the pulsation periods, so that the oscillations are highly non-adiabatic. The use of a non-adiabatic code is thus intrinsically necessary for an accurate confrontation with observables directly linked to the photosphere. The main specificity of MAD is the special care given to the treatment of the pulsation in the entire nongrey atmosphere. Hence, it is able to determine accurately the amplitudes and phases of variation of the different physical quantities in the very outer layers of stars. In particular, the normalized amplitude and phase of effective temperature variation can be determined. Its effect on line profile variations De Ridder et al. 2002) and on multi-color photometric amplitude ratios and phase differences (Dupret et al. 2003a) can be determined, which improves significantly the accuracy of mode identification methods. Moreover, since the non-adiabatic theoretical predictions are very sensitive to the characteristics of the equilibrium models, these models can be constrained by searching for the best fit between theory and observations; we term this method non-adiabatic asteroseismology.

Kepler Eclipsing Binaries with $δ$ Scuti/$γ$ Doradus Pulsating Components 1: KIC 9851944

“…As a first step to understand the theoretical pulsational spectrum of δ Scuti stars, we show the evolution of pulsational frequencies of l = 0, 1, 2 modes of a 1.8M ⊙ star from Zero Age Main Sequence (ZAMS) to post-MS phases in Figures 14 and 15. A similar diagram can be found in Dupret (2002). These modes suffer from less cancellation effect in broadband photometry like Kepler and thus are most likely to be observed.…”

Investigating surface correction relations for RGB stars

“…The modal surface effect stems from the fact that oscillation frequencies of stars are computed under the assumption of adiabaticity, which does not hold true in the near-surface layers (e.g. Dupret 2004;Christensen-Dalsgaard 2008;Townsend & Teitler 2013;Grosjean et al 2014). Moreover, the contribution from turbulent pressure, i.e.…”

Leaky-wave-induced disks around Be stars: a pulsational analysis on their formation

“…We adopted the AGS05 metal mixture (Asplund et al 2005), the corresponding OP opacity tables (Badnell et al 2005), X = 0.070 and Z = 0.014 and a convective core overshooting of 0.1. Non-adiabatic computations have been performed with MAD (Dupret 2002), in which the traditional approximation for rotation has been implemented (Bouabid et al 2013) to perform modes for 1 l 4. The efficiency of wave leakage (given by the integral over the surface of the wave kinetic energy) should increase with the rotation as the critical frequency increases.…”