18 research outputs found
New Spectroscopic Observations of the Post-AGB Star V354Lac=IRAS22272+5435
The strongest absorption features with the lower-level excitation potentials
eV are found to be split in the high-resolution optical
spectra of the post-AGB star V354 Lac taken in 2007--2008. Main parameters,
T=5650 K, =0.2, =5.0 km/s, and the abundances of 22
chemical elements in the star's atmosphere are found. The overabundance of the
-process chemical elements (Ba, La, Ce, Nd) in the star's atmosphere is
partly due to the splitting of strong lines of the ions of these metals. The
peculiarities of the spectrum in the wavelength interval containing the LiI
6707 \AA{} line can be naturally explained only by taking the
overabundances of the CeII and SmII heavy-metal ions into account. The best
agreement with the synthetic spectrum is achieved assuming (LiI)=2.0,
(CeII)=3.2, and (SmII)=2.7. The velocity field both in the
atmosphere and in the circumstellar envelope of V354 Lac remained stationary
throughout the last 15 years of our observations.Comment: 16 pages, 6 figures, 2 table
Optical spectrum of the post-AGB star HD56126 in the region 4010-8790 AA
We studied in detail the optical spectrum of the post-AGB star HD56126
(IRAS07134+1005). We use high resolution spectra (R=25000 and 60000) obtained
with the echelle spectrographs of the 6-m telescope. About one and a half
thousand absorptions of neutral atoms and ions, absorption bands of C_2, CN,
and CH molecules, and interstellar bands (DIBs) are identified in the 4010 to
8790 AA wavelength region, and the depths and radial velocities of these
spectral features are measured. Differences are revealed between the variations
of the radial velocities measured from spectral features of different
excitation. In addition to the well-known variability of the Halpha profile, we
found variations in the profiles of a number of FeII, YII, and BaII lines. We
also produce an atlas of the spectrum of HD56126 and its comparison staralpha
Per. The full version of the atlas is available in electronic form from
Web-address: http://www.sao.ru/hq/ssl/Atlas/Atlas.htmlComment: 42 pages, 6 figure
Detection of the spectral binary (SB2) nature of BD-6^o1178
BD-6^o1178 identified with the infrared source IRAS05238-0626 is shown for
the first time to be a spectroscopic binary (SB2) by analyzing the
high-resolution spectra taken with the NES echelle spectrograph of the 6-m
telescope. The components of the binary have close spectral types and
luminosity classes: F5IV-III and F3V. The heliocentric radial velocities are
measured for both components at four observing moments in 2004-2005. Both stars
have close rotation velocities, which are equal to 24 and 19km/s. We do not
confirm the classification of BD-6^o1178 as a supergiant in the transition
stage of becoming a planetary nebula. BD-6^o1178 probably is a young pre-MS
stars. It is possibly a member of the 1c subgroup of the OriOB1 association.Comment: 13 pages, 1 table, 4 figure
Spectroscopy of high proper motion stars in the ground--based UV
Based on high quality spectral data (spectral resolution R>60000) within the
wavelength range of 3550-5000 AA we determined main parameters (effective
temperature, surface gravity, microturbulent velocity, and chemical element
abundances including heavy metals from Sr to Dy) for 14 metal-deficient G-K
stars with large proper motions. The stars we studied have a wide range of
metallicity: [Fe/H]=-0.3 \div -2.9. Abundances of Mg, Al, Sr and Ba were
calculated with non-LTE line-formation effects accounted for. Abundances both
of the radioactive element Th and r-process element Eu were determined using
synthetic spectrum calculations. We selected stars that belong to different
galactic populations according to the kinematical criterion and parameters
determined by us. We found that the studied stars with large proper motions
refer to different components of the Galaxy: thin, thick disks and halo. The
chemical composition of the star BD+80 245 located far from the galactic plane
agrees with its belonging to the accreted halo. For the giant HD115444 we
obtained [Fe/H]=-2.91, underabundance of Mn, overabundance of heavy metals from
Ba to Dy, and, especially high excess of the r-process element Europium:
[Eu/Fe]=+1.26. Contrary to its chemical composition typical for halo stars,
HD115444 belongs to the disc population according to its kinematic parameters.Comment: 16 pages, 4 figures, 5 tables, "UV Universe-2010 (2nd NUVA Symposium)
conference
The evolutionary status of the semiregular variable QYSge
Repeated spectroscopic observations made with the 6m telescope of yielded new
data on the radial-velocity variability of the anomalous yellow supergiant
QYSge. The strongest and most peculiar feature in its spectrum is the complex
profile of NaI D lines, which contains a narrow and a very wide emission
components. The wide emission component can be seen to extend from -170 to +120
km/s, and at its central part it is cut by an absorption feature, which, in
turn, is split into two subcomponents by a narrow (16km/s at r=2.5) emission
peak. An analysis of all the Vr values leads us to adopt for the star a
systemic velocity of Vr=-21.1 km/s, which corresponds to the position of the
narrow emission component of NaI. The locations of emission-line features of
NaI D lines are invariable, which point to their formation in regions that are
external to the supergiant's photosphere. Differential line shifts of about
10km/s are revealed. The absorption lines in the spectrum of QYSge have a
substantial width of FWHM~45 km/s. The method of model atmospheres is used to
determine the following parameters: Teff=6250K, lg g=2.0, and microturbulence
Vt=4.5km/s. The metallicity of the star is found to be somewhat higher than the
solar one with an average overabundance of iron-peak elements of [Met/H]=+0.20.
The star is found to be slightly overabundant in carbon and nitrogen,
[C/Fe]=+0.25, [N/Fe]=+0.27. The alpha-process elements Mg, Si, and Ca are
slightly overabundant [alpha/H]=+0.12. The strong sodium excess, [Na/Fe]=+0.75,
is likely to be due to the dredge-up of the matter processed in the NeNa cycle.
Heavy elements of the s-process are underabundant relative to the Sun. On the
whole, the observed properties of QYSge do not give grounds for including this
star into the group of RCrB or RVTau-type type objects.Comment: 29 pages, 8 figures, 4 tables; accepted by Astrophys. Bulleti