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

摘要

Context. The determination of pulsation velocitiesfrom observedspectra of Cepheids is needed for the Baade-Wesselink calibration ofthese primary distance markers. Aims. The applicability of the Fourier-disentanglingtechniquefor the determination of pulsation velocities of Cepheids and otherpulsating stars is studied. Methods. The KOREL-code was modified to enablefitting of freeparameters of a prescribed line-profile broadening functioncorresponding to the radial pulsations of the stellar atmosphere. Itwas applied to spectra of Cepin the H-alpha region observed with the Ondrejov 2-m telescope. Results. The telluric lines were removed usingtemplate-constrained disentangling, phase-locked variations ofline-strengths were measured and the curves of pulsational velocitiesobtained for several spectral lines. It is shown that the amplitude andphase of the velocities and line-strength variations depend on thedepth of line formation and the excitation potential. Conclusions. The disentangling of pulsations in theCepheid spectra may be used for distance determination. Key words: line: profiles - techniques:spectroscopic - stars: variables: Cepheids - stars: atmospheres