Radii of LMC and SMC Cepheids

We collected long sets of precise radial velocity observations of radial velocities for 8 SMC and 14 LMC Cepheids. Based on these series of radial velocity measurements and on multicolor photoelectric observations, we calculated radii of the program extragalactic Cepheids using a modification of Balona's method. Our main goal was to determine the long-period branch of the period-radius diagram and reveal a dependence on metallicity. We derived the following period-radius relation: log R = 1.06(+/- 0.03)+0.74(+/- 0.02) log P. We did not find any significant difference between the period-radius relation of extragalactic Cepheids and that of fundamental-mode galactic Cepheids. ((c) 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)