Vladimir E. Panchuk

OPTICAL SPECTRUM OF THE IR SOURCE IRC + 10420 IN 1992-1996

To understand the evolutionary stage of the peculiar supergiant IRC+10420, we have been taking spectra for several years at the 6m telescope. The optical spectrum of IRC+10420 of the years from 1992 through 1996 points to the increase in the temperature: spectral class A5 instead of the former F8, as was pointed out by Humpreys et al., (1973). Now it resembles the spectra of late-type B[e] stars. The spectrum contains absorptions (mainly of ions) formed in the photosphere, apparently stationary with respect to the star center of mass, and emissions too, which can be formed in the fossil expanding envelope as well as partly in its compressing region. Using our spectra and spectral data obtained by Oudmaijer (1995) we estimated the atmospheric parameters Teff=8500 K, logg=1.0, Vt=12km/s and concluded that metallicity of IRC+10420 is solar: the average value [(V,Cr,Fe)/H]=-0.03. Combination of results allows us to consider IRC+10420 as a massive supergiant evolving to the WR-stage.

HD 331319: A Post-AGB F Supergiant with He I Lines

AbstractBased 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 (Mυ<−8m object with the effective temperature Teff=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

HD 179821 (V1427 Aql, IRAS 19114+0002) – A Massive Post-Red Supergiant Star?

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Detection of spectral variability of the optical component of the IR source IRAS 20508+2011

of the object suggest that it belongs to the Galactic disk population. The envelope expansion velocity, Vexp≈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.

Spectroscopy and Spectral Energy Distribution of the Peculiar Supergiant IRAS 04296+3429

The World Space Observatory Ultraviolet (WSO/UV) is a multi-national project grown out of the needs of the astronomical community to have future access to the ultraviolet range of the spectrum. The development of the WSO/UV S/C and the telescope is headed by the Russian Federal Space Agency (Roscosmos). The mission is scheduled to be launched in 2010 into the L2 orbit. The WSO/UV consists of a single Ultraviolet Telescope, incorporating a primary mirror of 1.7 m diameter feeding UV spectrometer and UV imagers. The UV spectrometer comprises three different single spectrographs, two high resolution echelle spectrographs - the High Resolution Double Echelle Spectrograph (HIRDES) - and a low dispersion long slit instrument. Within the HIRDES the spectral band (102 - 310 nm) is separated into two echelle spectrographs covering the UV range between 174- and 310 nm (UVES) and VacuumUV range between 102 and 176 nm (VUVES) with a very high spectral resolution of > 50000. Each spectrograph encompass a stand alone optical bench structure with a fully redundant high speed MCP detector system, the optomechanics and a network of mechanisms with different functionalities. The fundamental technical concept is based on the heritage of the two previous ORFEUS SPAS missions. The phase B1 development activities are described in this paper under consideration of performance aspects, design drivers, the related trade offs (e.g. mechanical concepts, material selection etc.) and the critical functional and environmental test verification approach. Furthermore the actual state of the other scientific instruments of the WSO/UV (e.g. UV imagers) project is described.

PFES2: new primary focus Echelle spectrograph for Russian 6-m telescope

We have derived elemental abundances of a remarkable star, HD 179821, with unusual composition (e.g. [Na/Fe]=1.0

Spectral and polarimetric facilities for ground support of the WSO-UV Space mission

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Optical design of WUVS instrument: WSO-UV spectrographs

0.2 dex) and extra-ordinary spectral characteristics. Its metallicity at [Fe/H]=0.4 dex places it among the most metal-rich stars yet analyzed. The abundance analysis of this luminous star is based on high resolution and high quality (S/N