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Astrometry ; Space Sciences ; Archaeoastronomy and Astronomy in Culture
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carbon stars ; surveys ; late - type stars
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Abstract:
The second Gaia data release (Gaia DR2) data are used to analyze and estimate a some important parameters for 127 carbon (C) type stars (56 are late N - type Asymptotic Giant Branch (AGB) C stars, 71 are early -type CH giants) detected on the First Byurakan Spectral Sky Survey (FBS) low - resolution (lr) spectral plates. Gaia DR2 G broad band magnitudes are in the range 9.4 mag < G < 18.2 mag. for FBS C stars. Radial velocities (RV) is available for 75 C stars out of 127. For 9 objects RV is greater than 200 km/s. Absolute magnitudes in V band are estimated for 18 FBS C stars, having luminosity data, from which 17 are CH giants. They are in the range between -3.5 ≤ MV < +0.5 mag. For FBS 1918+869 absolute magnitude MV = -3.4(±0.2) mag, which is typical for N type AGB C stars. Having distance estimations, the Hertzsprung - Russell diagram (HRD, or color - absolute magnitude diagram) was constructed for C stars. All FBS detected C stars are giants and AGB stars in the Galactic Halo. They are not far than 14 kpc from the Sun and 8 kpc from the Galactic plane.