Документ взят из кэша поисковой машины. Адрес
оригинального документа
: http://jet.sao.ru/hq/ssl/papers/CRDF.html
Дата изменения: Unknown Дата индексирования: Mon Oct 1 23:51:10 2012 Кодировка: |
The main purpose of the investigation of the first three objects are a clarification of the models of their winds and an attempt to get the additional spectroscopic differences between the true hypergiants and theirs simulations by the low-mass stars. The clarification of the nature and the evolutinary state is the task of the investigation of the two last objects.
Based on a review of published information on stellar spectro- polarimeters, a program to develop equipment for stellar spectro- polarimetry at the 6-m telescope is proposed (Klochkova V.G., Panchuk V.E., and Romanenko V.P. Stellar spectropolarimeters. Preprint SAO N156, 2001).
A seminar on spectroscopic and spectropolarimetric devices at the 6m telescope was presented on November, 15, 2001. Primary astrophysical results from the FSU team, based on the observational data obtained with the devices mentioned above, concerning post-AGB stars, A- and F-supergiants, and hypergiants were reported.
The FSU team visited the Catholic University of Valparaiso (Valparaiso, IN) aiming at a joint scientific discussion on proto-planetary nebulae with Prof. B. Hrivnak, a well-known researcher in this field. The FSU team's results on high resolution spectroscopy of such objects were presented there. These results are significant to understanding the processes of stellar nucleosynthesis and evolution of intermediate-mass stars after the main sequence phase.
During the visit, the FSU team was acquainted with spectral devices at the Ritter Observatory and software for 2-dimensional spectra processing. We have discussed advantages of the packages used for spectroscopic data reduction at the Ritter Observatory and at the Special Astrophysical Observatory.
We have also discussed a possibility to use new observational facilities at the 6m telescope to select new targets for follow up high resolution spectroscopy.
Spectroscopic (resolving power R=60000) and spectropolarimetric (R=15000) observations of the northern lobe of the Egg nebula (AFGL2688) were performed at the 6-meter telescope. Recent results published by Klochkova et al.(2000, Astronomy Letters) confirmed the post-AGB evolutionary state for the central star of this object.
The combination of spectroscopy and spectropolarimetry permits us to separate optical spectral components formed in the stellar atmosphere from those formed in the nebula. We showed that the approximation of single scattering of optical radiation is valid within the nebula. The optical spectrum of the nebula contains emission components of the resonance sodium doublet NaI D1&2, emission in H alpha, and emission bands of the C2 molecule. We showed that the nebula is optically thick in the lines of the sodium doublet. A system of absorptions found in the resonance sodium line confirms a continuation of the matter outflow from the star. We resolved the rotational structure of the emission bands of the Swan system of the C2 molecule. Our analysis of both the rotational spectrum and vibrational-rotational transitions of the C2 molecule confirms a hypothesis about the resonance fluorescence as their exciting mechanism, which was proposed earlier by Klochkova et al. (2000).
A macroturbulence velocity in the atmosphere of the central star was estimated. Radial velocities were measured using spectral details formed both in the photosphere of the supergiant and inside the lobe. An analysis of the optical data was carried out in combination with published results based on the radio- and IR-regions. We critically considered models suggested for the nebula AFGL2688. It should be noted that high resolution spectropolarimetry for such a faint object (V>14.5mag) was obtained for the firts time.
The paper "Nebula AFGL2688: spectroscopy and spectropolarimetry with high spectral resolution", by by V.G.Klochkova, V.E.Panchuk and M.V.Yushkin, will be submitted to Astronomy Reports soon.