Peculiarities and variations in the optical spectrum of the post-AGB star V448Lac=IRAS22223+4327

Repeated observations with high spectral resolution acquired in 1998-2008 are used to study the temporal behavior of the spectral line profiles and velocity field in the atmosphere and circumstellar envelope of the post-AGB star V448Lac. Asymmetry of the profiles of the strongest absorption lines with low-level excitation potentials less 1eV and time variations of these profiles have been detected, most prominently the profiles of the resonance lines of BaII, YII, LaII, SiII. The peculiarity of these profiles can be explained using a superposition of stellar absorption line and shell emission lines. Emission in the (0;1) 5635A Swan band of the C2 molecule has been detected in the spectrum of V448Lac for the first time. The core of the Halpha line displays radial velocity variations with an amplitude ~8 km/s. Radial velocity variations displayed by weakest metallic lines with lower amplitudes, 1-2 km/s, may be due to atmospheric pulsations. Differential line shifts, 0 -- 8 km/s, have been detected on various dates. The position of the molecular spectrum is stationary in time, indicating a constant expansion velocity of the circumstellar shell, Vexp=15.2 km/s, as derived from the C2 and NaI lines.Comment: 19 pages, 8 figures, 1 tabl

Evolutionary stage of the spectral variable BD+48 1220=IRAS 05040+4820

Based on high-resolution observations (R=60000 and 75000), we have studied the optical spectral variability of the star BD+48 1220 (IRAS05040+4820). We have measured the equivalent widths of numerous absorption lines of neutral atoms and ions at wavelengths from 4500 to 6760 AA, as well as the corresponding radial velocities. We use model atmospheres to determine Teff=7900K, log g=0.0, microturbulence velocity xi_t=6.0, and the abundances for 16 elements. The star's metallicity differs little from the solar value: [Fe/H]=-0.10 dex. The main peculiarity of the chemical composition of the star is a large He-excess, derived from the HeI 5876 A absorption, [He/H]=+1.04, and the equally large O-excess, [O/Fe]=+0.72 dex. The C-excess is small, [C/Fe]=+0.09 dex, and the ratio [C/O]$\le$ 1. We obtained a revised relation for the light-metal abundances: [Na/Fe]=+0.87 with [Mg/Fe]=-0.31. The barium abundance is low, [Ba/Fe]=-0.84. The radial velocity of the star measured from photospheric absorption lines over three years of observations varies in the interval V_sun = -(7 - 15) km/s. Time variable differential line shifts have been revealed. The entire set of available data (the luminosity Mv~-5m, velocity V_lsr~-20 km/s, metallicity [Fe/H]=-0.10, and peculiarities of the optical spectrum and chemical composition) confirms the status of BD+48 1220 as a post-AGB star with He- and O-excesses belonging to the Galactic disk.Comment: 42 pages, 7 figures, 6 tables, accepted by Astronomy Report

NEW ASPECT OF SMALL-AMPLITUDE CEPHEID SU CAS

New 17 high-resolutional spectra of small-amplitude Cepheid SU Cas have been obtained to determine its atmosphere parameters (Teff=6353 K; log g=2.38; Vt=3.25 km s -1 and to measure its radial velocities. The last ones were added to the total RV list (378 values) and using the frequency analysis we can specify the pulsational and orbital periods of this Cepheid. With the well-known main pulsational period of 1.9493 days, classified as fundamental tone, we can detect the presence of two equidistant periods at a distance of +-0.003 c/d from it, and the secondary (possible first overtone) one of 2.0405 day. Their ratio P1/P0 = 0.96 supposed about an existence of non-radial pulsations in the Cepheid's atmosphere. Changes of the mean colour-index, effective temperature and γ-velocity confirmed the presence of one or more companions with possible periods of 463.7 - 483.8, 1738.8 and 7490.3 days

PULSATIONAL AND ORBITAL PERIODS OF SMALL-AMPLITUDE CEPHEID SU CAS

New seven high-resolutional spectra of small-amplitude Cepheid SU Cas have been obtained to determine its atmosphere parameters (Teff=6384 K; log g=2.4; Vt=3.3 km s-1) and to measure its radial velocities. The last ones were added to the total list (360 values) and using the frequency analysis we can specify the pulsational and orbital periods of this Cepheid. With the well-known main pulsational period of 1.949329 days, classified as fundamental tone, we can detect the presence of two equidistant periods at a distance of ±0.003 c/d from it, and the secondary (possible first overtone) one of 2.040461 day. Their ratio P1/P0 = 0.96 supposed about an an existence of non-radial pulsations in the Cepheid's atmosphere. Changes of the mean colour-index, effective temperature and γ-velocity confirmed the presence of one or more companions with possible periods of 463.7 - 483.8, 1738.8 and 7490.3 days

Hα LINE AS AN INDICATOR OF ENVELOPE PRESENCE AROUND THE CEPHEID POLARIS Aa (α UM i)

We present the results of the radial velocity (RV ) measurements of metallic lines as well as Hα (Hβ ) obtained in 55 high-resolution spectra of the Cepheid α 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 Hα 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 Hα line core as dynamical changes in the envelope around Polaris Aa