Notes on disentangling of spectra II. Intrinsic line-profile variability due to Cepheid pulsations

Abstract

The determination of pulsation velocities from observed spectra of Cepheids is needed for the Baade-Wesselink calibration of these primary distance markers. The applicability of the Fourier-disentangling technique for the determination of pulsation velocities of Cepheids and other pulsating stars is studied. The KOREL-code was modified to enable fitting of free parameters of a prescribed line-profile broadening function corresponding to the radial pulsations of the stellar atmosphere. It was applied to spectra of delta Cep in the H-alpha region observed with the Ondrejov 2-m telescope. The telluric lines were removed using template-constrained disentangling, phase-locked variations of line-strengths were measured and the curves of pulsational velocities obtained for several spectral lines. It is shown that the amplitude and phase of the velocities and line-strength variations depend on the depth of line formation and the excitation potential. The disentangling of pulsations in the Cepheid spectra may be used for distance determination.

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• Understanding the dynamical structure of pulsating stars. HARPS spectroscopy of the delta Scuti stars rho Pup and DX Cet
• Understanding the dynamical structure of pulsating stars: The center-of-mass velocity and the Baade-Wesselink projection factor of the beta-Cephei star alpha-Lupi
• Spectral disentangling with Spectangular
• Spectangular: Disentangling variable spectra
• VO-KOREL: A Fourier disentangling service of Virtual Observatory