A photometric mode identification method, including an improved non-adiabatic treatment of the atmosphere

Abstract

Abstract. We present an improved version of the method of photometric mode identification of Heynderickx et al. (1994). Our new version is based on the inclusion of precise non-adiabatic eigenfunctions determined in the outer stellar atmosphere according to the formalism recently proposed by Dupret et al. (2002a). Our improved photometric mode identification technique is therefore no longer dependent on ad hoc parameters for the non-adiabatic effects. It contains the complete physical conditions of the outer atmosphere of the star, provided that rotation does not play a key role. We apply our method to the two slowly pulsating B stars HD 74560 and HD 138764 and to the β Cephei star EN (16) Lac. Besides identifying the degree of the pulsating stars, our method is also a tool for improving the knowledge of stellar interiors and atmospheres, by imposing constraints on parameters such as the metallicity and the mixing-length parameter α (a procedure we label non-adiabatic asteroseismology).

Non-adiabatic Asteroseismology of Near-Main Sequence Variable Stars

“…The last degree of freedom is then lifted by the non-adiabatic analysis. As shown, for example, in Dupret et al (2003a), the theoretical non-adiabatic predictions (growth rates, photometric amplitude ratios and phase differences) are essentially sensitive to the metallicity of the models for /3 Cep stars. On one hand, imposing that all the observed modes are excited, we find Z > 0.016.…”

“…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.…”

Variability in the CoRoT photometry of three hot O-type stars

“…In these calculations, we assumed a metallicity of Z = 0.015 and the metal mixture of Grevesse & Noels (1993). We also used the MAD non-adiabatic pulsation code (Dupret et al 2003) to determine the frequencies of excited modes. The computations were made on the basis of preliminary stellar and wind parameters derived from the atmosphere code CMFGEN (Hillier & Miller 1998) by Martins et al (in prep.).…”

CoRoT's view of newly discovered B-star pulsators: results for 358 candidate B pulsators from the initial run's exoplanet field data

“…19). Stellar models were computed with cles (Scuflaire et al 2008b), adiabatic frequencies with losc (Scuflaire et al 2008a), and the stability of modes of degree = 0, 1, 2 was investigated with the code mad (Dupret et al 2003). In the case of δ Sct and γ Doradus stars, the nonadiabatic computations included the interaction between convection and pulsation as described by Grigahcène et al (2005).…”