Discovery of the spectroscopic binary nature of the classical Cepheids   FN Aql and V1344 Aql
  We present the analysis of photometric and spectroscopic data of two classical Cepheids, FN Aquilae and V1344 Aquilae. Based on the joint treatment of the new and earlier radial velocity data, both Galactic Cepheids have been found to be a member in a spectroscopic binary system.   To match the phases of the earlier radial velocity data correctly with the new ones, we also determined the temporal behaviour of the pulsation period of these Cepheids based on all available photometric data. The O-C graph covering about half century shows slight changes in the pulsation period due to stellar evolution for both Cepheids. 
L. Szabados, B. Cseh, J. Kov\'acs, B. Cs\'ak, \'A. D\'ozsa, Gy. M.   Szab\'o, A. E. Simon, T. Borkovits, L. L. Kiss, I. Jank...
astro-ph.SR