Study of the effect of metallicity on the amplitudes of Cepheids.pdf

Astron. Nachr. / AN 999, No. 88, 789 – 792 (2006) / DOI please set DOI! Study of the effect of metallicity on the amplitudes of Cepheids P. Klagyivik1,⋆ and L. Szabados2,⋆⋆ 1 Department of Astronomy of E¨otv¨os Lor´and University, 11 12 Budapest, P´azm´any P. s´et´any 1/A, Hungary 2 Konkoly Observatory of the Hungarian Academy of Sciences, 1525 Budapest XII, PO Box 67, Hungary Received 3 March 2007, accepted 15 May 2007 7 Published online later 0 0 Key words Cepheids – photometry – spectroscopy 2 Results concerning the dependence of photometric and radial velocity amplitudes on metallicity are presented based on y a about 200 Galactic classical Cepheids pulsating in the fundamental mode. The Galactic distribution of the [Fe/H] value of Cepheids is also studied. We show that the photometric amplitude ratio A /A is independent of metallicity. The observed I V M dependence of this ratio on the pulsation period does not correspond to the theoretical predictions. c 5 2006 WILEY-VCH Verlag GmbH Co. KGaA, Weinheim 1 ] h 1 Introduction dance. Nevertheless, when studying the metallicity depen- p dence of the Cepheid distance scale, the external galaxies - o Cepheids are regularly pulsating variables and their radial are always