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31.
Based on CCD spectra taken with an echelle spectrometer attached to the 6-m telescope, we have determined for the first time the fundamental parameters and detailed chemical composition of HD 331319, an optical counterpart of the infrared source IRAS 19475+3119, by the model-atmosphere method. Helium lines were detected in the spectrum of this luminous (Mυm object with the effective temperature T eff=7200 K. This detection can be interpreted as a significant helium overabundance in the observed atmospheric layers and may be considered as a manifestation of helium synthesis during the preceding evolution. Nitrogen and oxygen were found to be overabundant, [N/Fe]⊙=+1.30 dex and [O/Fe]⊙=+0.64 dex, with the carbon overabundance being modest. The metallicity of the stellar atmosphere, [Fe/H]⊙=+0.25, differs only slightly from its solar value. The s-process metals are not overabundant but most likely underabundant relative to iron: [X/Fe]⊙=?0.68 for Y and Zr. Barium is also underabundant relative to iron: [Ba/Fe]⊙=?0.47. The heavier elements La, Ce, Nd, and Eu are slightly enhanced relative to iron: the mean [X/Fe]⊙=?0.16 for them. In general, the elemental abundances confirm that IRAS 19475+3119 is a post-AGB object. The metallicity in combination with the radial velocity Vr=?3.4 km s?1 and Galactic latitude $\left| b \right| = 2_.^ \circ 7$ of the object suggest that it belongs to the Galactic disk population. The envelope expansion velocity, V exp≈21 km s?1, was determined from the positions of the absorption bands that originate in the circumstellar envelope. A comparison of our results for the comparison star HD 161796=IRAS 17436+5003, a typical post-AGB object, with previously published data revealed an evolutionary increase in the effective temperature of HD 161796 at a mean rate of ≥50° per year. 相似文献
32.
The phenomenon of spectral mimicry refers to the fact that hypergiants and post-AGB supergiants—stars of different masses in fundamentally different stages of their evolution—have similar optical spectra, and also share certain other characteristics (unstable extended atmospheres, expanding dust–gas envelopes, high IR excesses). As a consequence, it is not always possible to distinguish post-AGB stars from hypergiants based on individual spectral observations in the optical. Examples of spectral mimicry are analyzed using uniform, high-quality spectral material obtained on the 6-m telescope of the Special Astrophysical Observatory in the course of long-term monitoring of high-luminosity stars. It is shown that unambiguously resolving the mimicry problem for individual stars requires the determination of a whole set of parameters: luminosity, wind parameters, spectral energy distribution, spectral features, velocity field in the atmosphere and circumstellar medium, behavior of the parameters with time, and the chemical composition of the atmosphere. 相似文献
33.
Klochkova V. G. Miroshnichenko A. S. Panchuk V. E. Tavolzhanskaya N. S. Yushkin M. V. 《Astronomy Reports》2022,66(5):429-440
Astronomy Reports - The optical spectra of the B-supergiant LS III +52°24 (IRAS 22023+5249) obtained at the 6-m BTA telescope with a resolution $${\text{R}} \geqslant 60{\kern 1pt} {\kern 1pt}... 相似文献
34.
Based on our high-spectral-resolution observations performed with the NES echelle spectrograph of the 6-m telescope, we have studied the peculiarities of the spectrum and the velocity field in the atmosphere and envelope of the cool supergiant V1027 Cyg, the optical counterpart of the infrared source IRAS 20004+2955. A splitting of the cores of strong absorptions of metals and their ions (Si II, Ni I, Ti I, Ti II, Sc II, Cr I, Fe I, Fe II, BaII) has been detected in the stellar spectrum for the first time. The broad profile of these lines contains a stable weak emission in the core whose position may be considered as the systematic velocity V sys = 5.5 km s?1. Small radial velocity variations with an amplitude of 5–6 km s?1 due to pulsations have been revealed by symmetric low- and moderate-intensity absorptions. A long-wavelength shift of the Hα profile due to line core distortion is observed in the stellar spectrum. Numerous weak CN molecular lines and the KI 7696 Å line with a P Cyg profile have been identified in the red spectral region. The coincidence of the radial velocities measured from symmetric metal absorptions and CN lines suggests that the CN spectrum is formed in the stellar atmosphere. We have identified numerous diffuse interstellar bands (DIBs) whose positions in the spectrum, V r (DIBs) = ?12.0 km s?1, correspond to the velocity of the interstellar medium in the Local Arm of the Galaxy. 相似文献
35.
The radial velocities of the star BM Ori are determined from spectra obtained by the HST and IUE satellites, as well as from spectra obtained with the BTA telescope. An analysis of this data shows that the radial velocities of the main star and its satellite experience an irregular positive shift by 20-30 km/s. This fact can only be interpreted in terms of the presence of yet another star in the binary system. The new observations have made it possible to significantly improve the accuracy of the spectroscopic elements of the orbit of the close binary system and to estimate the orbital characteristics of the third body. The preliminary values of the elements are: Ep=JD2444744, P=1302d, =11km/s, e=0.92, K=20km/s, and =1.6rad. 相似文献
36.
Two CCD spectra of the star V1016 Ori were obtained with the echelle spectrograph of the 6-m (BTA) telescope. An analysis of these spectra allowed us to estimate the star's atmospheric parameters (T eff=29700 K, logg=4.4) and projected rotational velocity (Vsini=60 km s?1) and to determine its chemical composition. Chemical anomalies were found. The Fe abundance is nearly solar; He, C, O, Mg, Al, Si are underabundant; and Ne, S, Zn are overabundant. The “spectroscopic” radius of the primary is in satisfactory agreement with its radius determined from the light and radial-velocity curves if the small star is assumed to lie in front of the giant star during an eclipse. The paradox of the primary's anomalous radius is thus resolved. A table of line equivalent widths and a portion of the star's spectrum are given in Appendices 1 and 2. 相似文献
37.
The main parameters of spectroscopic experiments in the UV range of the electromagnetic spectrum are estimated. Different spectral devices are compared in terms of their potential quality. Some technical details of current UV experiments and prospects of spectrographs of the WSO-UV project are discussed. 相似文献
38.
V. G. Klochkova V. E. Panchuk E. L. Chentsov M. V. Yushkin 《Astrophysical Bulletin》2007,62(3):217-234
Repeated spectroscopic observations made with the 6-m telescope of SAO RAS yielded new data on the radial-velocity variability of the anomalous yellow supergiant QY Sge. 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 (16 km/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 10 km/s are revealed. Emission in the Hα line is weaker than in NaI D lines, it fills the photospheric absorption almost completely. The absorption lines in the spectrum of QY Sge have a substantial width of FWHM ≈ 45 km/s. The method of model atmospheres is used to determine the following parameters: the effective temperature T eff =6250±150 K, surface gravity l g g=2.0±0.2, and microturbulence velocity ξ t =4.5±0.5 km/s. The chemical composition of the atmosphere differs only slightly from the solar composition: the metallicity of the star is found to be somewhat higher than the solar metallicity 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 α-process elements Mg, Si, and Ca are slightly overabundant, on the average by [α/H]⊙=+0.12, and sulfur overabundance is higher, [S/α]=+0.29. The strong overabundance of sodium, [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 QY Sge do not give grounds for including this star into the group of RCrB or RVTau-type objects. 相似文献
39.
V. G. Klochkova E. L. Chentsov N. S. Tavolganskaya M. V. Shapovalov 《Astrophysical Bulletin》2007,62(2):162-192
The optical spectrum of the post-AGB star HD56126 identified with the infrared source IRAS07134+1005 is studied in detail using high spectral resolution observations (R = 25000 and 60000) performed with the echelle spectrographs of the 6-m telescope. A total of about one and a half thousand absorptions of neutral atoms and ions, absorption bands of C2, CN, and CH molecules, and interstellar bands (DIBs) are identified in the 4012 to 8790 Å Å wavelength interval, 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 Hα 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 star α Per. The full version of the Atlas is available in electronic form from: http://www.sao.ru/hq/ssl/Atlas/Atlas.html. 相似文献
40.
Optical spectra taken in 1997–2008 are used to analyze the spectral peculiarities and velocity field in the atmosphere of the peculiar supergiant 3 Pup. The profiles of strong Fe II lines and of the lines of other iron-group ions have a specific shape: the wings are raised by emissions, whereas the core is sharpened by a depression. The latter feature becomes more pronounced with the increasing line strength, and the increasing wavelength. Line profiles are variable: the magnitude and sign of the absorption asymmetry, and the blue-to-red emission intensity ratios vary from one spectrum to another. The temporal Vr variations are minimal for the forbidden emissions and sharp shell cores of the absorption features of FeII(42), and other strong lines of iron-group ions. The average velocity for the above lines can be adopted as the systemic velocity: Vsys = 28.5 ± 0.5 km/s. The weakest photospheric absorptions and photospheric MgII, Si II absorptions exhibit well-defined day-to-day velocity variations of up to 7 km/s. Quantitative spectral classification yields the spectral type of A2.7±0.3 Ib. The equivalent widths and profiles of Hδ and Hγ, and the equivalent width of the OI 7774 Å triplet yield an absolute magnitude estimate of Mv=?5.5m ± 0.3m, implying the heliocentric distance of 0.7 kpc. 相似文献