Usenko, I. A.Miroshnichenko, A. S.Klochkova, V. G.Tavolzhanskaya, N. S.2015-11-092015-11-092015Odessa Astronomical Publicationshttps://dspace.onu.edu.ua/handle/123456789/7546Odessa Astronomical publications / Одесская астроном. обсерватория . – Одесса : Астропринт, 2015.We present the results of the radial velocity (RV ) measurements of metallic lines as well as H (H ) obtained in 55 high-resolution spectra of the Cepheid UMi (Polaris Aa) in 1994–2010. While the RV amplitudes of these lines are roughly equal, their mean RV begin to differ essentially with growth of the Polaris Aa pulsational activity. This difference is accompanied by the H core asymmetries on the red side mainly (so-called knifelike profiles) and reaches the value of 8–12 km/s in 2003 with subsequent decrease to 1.5–2 km/s. We interpret so unusual behaviour of the H line core as dynamical changes in the envelope around Polaris Aa.enStars: CepheidsStars: radial velocitiesStars: Ha absorption lineStars: envelopesStars: individual - UMi (Polaris A)Article