Photometric and spectroscopic study of silicon Ap-star HD193722
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The period of light variationP=1 . d 13316 has been found for the silicon B9 IVp star HD 193722. Spectroscopic study of this star was based on 35 spectrograms with dispersion 4 Å mm−1 well distributed in phase. The measurements of radial velocities of spectral line components for SiII, HeI, EuII, FeII and SrII allowed us to localize several regions on the surface of the star with enhanced abundance of these elements. The phase of maximum light inU, B andV was found to be the same as the phase of maximum Eu abundance. The coincidence of the regions with larger abundance of Si and He in HD 193 722 disagree with the hypothesis of diffusion in the presence of a magnetic field developed by Michaud (1971), to explain the peculiar chemical composition of Ap-stars.
HD 193722 is a silicon B9 IVp star for which the magnetic field has not been measured. In the list by Palmeret al. (1962) its rotational velocityV sini is given as 250 kms−1. As will be seen below, this value is too high. Megessier (1971) determined from hydrogen line profiles and continuous spectrumTeff=13 000° and lgg=3.5.
The results of photometric and spectroscopic study of HD193722 are given below.
KeywordsHydrogen Silicon Magnetic Field Spectral Line Radial Velocity
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