Long-Term Radial Velocity Monitoring of the HeI 6678 Line of zeta Tau

Volume 44 number 1 (2016)

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Ernst Pollmann

Germany, 51375 Leverkusen, Emil-Nolde-Str.12, ernestospec@hotmail.de

Abstract

With our investigation period of approximately 15 years we have been able to calculate a new long-term period of the HeI 6678 radial velocity (RV) of the binary system zeta Tau. Such a long investigation period was possible because we were able to combine RV data from Ruzdjak et al. (2009) with our own data of the ARAS group (http://www.astrosurf.com/aras/). To detect long-term cyclic RV variations of the HeI 6678 absorption line in the spectrum of zeta Tau leads to the necessity to take into account the overlaid medium-term orbital RV period of 133 days and short-term RV variations, done in this paper.