Based on high-spectral-resolution observations (R=60000) performed with the
6-m BTA telescope in combination with the echelle spectrograph NES, we have
studied the optical spectra of three A-type supergiants: a peculiar supergiant
3 Pup, a post-AGB star BD+48 1220, and a massive $\alpha$ Cyg, which belong to
essentially different stages of evolution. A spectral atlas for these stars is
prepared in the wavelength interval of 3920 to 6720 \AA.Comment: 56 pages, 2 tables, 10 figure
from different observations) and the strong intensity of the red emission (it exceeds the continuum level by up to a factor of seven) are typical for hypergiants rather than the classical supergiants. IRAS 01005 is an example of spectral mimicry of a low mass post-AGB star masquerading as a massive hypergiant.
Based on the high resolution spectral monitoring conducted at the 6-m BTA telescope, we study the optical spectrum of the high-latitude variable V534 Lyr. Heliocentric radial velocities V r corresponding to the positions of all metal absorption components, as well as the Na I D and Hα lines were measured during all the observational dates. The analysis of the velocity field examining the lines of various nature revealed a low-amplitude variability of V r based on the lines with a high excitation potential, which are formed in deep layers of the stellar atmosphere, and allowed to estimate the systemic velocity of V sys ≈ −125 km s −1 (V lsr ≈ −105 km s −1 ). The distance estimate of d ≈ 6 kpc for the star leads us to its absolute magnitude of M V ≈ −5. m 3, what corresponds to the MK spectral classification. The previously undetected for this star spectral phenomenon was revealed: at certain times a splitting of the profiles of low-excited absorptions is observed, reaching ∆V r = 20-50 km s −1 . A combination of the parameters: reduced metallicity [Met/H] ⊙ = −0.28, increased nitrogen abundance [N/Fe] = +1.10, large spatial velocity, high luminosity, a strong variability of the emission-absorption profiles of H I lines, splitting of metal absorptions at different times of observations and the variability of the velocity field in the atmosphere allow us to classify V534 Lyr as a pulsating star near the HB and belonging to the thick disk of our Galaxy.
Over the past decades, the achievements in astronomical instrumentation have given rise to a number of novel advanced studies related to the analysis of large arrays of observational data. One of the most famous of these studies is a study of transient events in the near and far space and a search for exoplanets. The main requirements for such kinds of projects are a simultaneous coverage of the largest possible field of view with the highest possible detection limits and temporal resolution. In this study, we present a similar project aimed at creating an extensive, continuously updated survey of transient events and exoplanets. To date, the core of the project incorporates several 0.07–2.5 m optical telescopes and the 6-m BTA telescope of the Special Astrophysical Observatory of RAS (Russia), a number of other Russian observatories and the Bonhyunsan observatory of the Korea Astronomy and Space Science Institute (South Korea). Our attention is mainly focused on the description of two groups of small, wide-angle optical telescopes for primary detection. All the telescopes are originally designed for the goals of the project and may be of interest to the scientific community. A description is also given for a new, high-precision optical spectrograph for the Doppler studies of transient and exoplanet events detected within the project. We present here the philosophy, expectations and first results obtained during the first year of running the project.
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