191 research outputs found
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.Comment: 14 pages, Latex, 4 ps figures, uses supertab.sty. Accepted for
publication in the MNRA
Polaris B, an optical companion of Polaris (alpha UMi) system: atmospheric parameters, chemical composition, distance and mass
We present an analysis of high-resolution spectroscopic observations of
Polaris B, the optical companion of the Polaris Ab system. The star has a
radial velocity V_r of -16.6km/s to -18.9km/s, and a projected rotational
velocity vsini=110 km/s. The derived atmospheric parameters are: Teff=6900K;
logg=4.3; V_t=2.5km/s. Polaris B has elemental abundances generally similar to
those of the Cepheid Polaris A (Usenko et al. 2005a), although carbon, sodium
and magnesium are close to the solar values. At a spectral type of F3V Polaris
B has a luminosity of 3.868L_sun, an absolute magnitude of +3.30mag, and a
distance of 109.5pc. The mass of the star is estimated to be 1.39M_sun, close
to a mass of 1.38+/-0.61M_sun for the recently-resolved orbital periods
companion Polaris Ab observed by Evans et al. (2007).Comment: 6 pages, 3 figures, 1 tabl
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