Astronomy and Astrophysics – Astrophysics
Scientific paper
Feb 1994
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1994a%26a...282...93s&link_type=abstract
Astronomy and Astrophysics (ISSN 0004-6361), vol. 282, no. 1, p. 93-105
Astronomy and Astrophysics
Astrophysics
28
Atmospheric Models, Binary Stars, Early Stars, Light Curve, Radial Velocity, Spectroscopic Analysis, Stellar Atmospheres, Stellar Models, Mathematical Models, Photosphere, Stellar Mass, Stellar Orbits, Stellar Spectra, Stellar Spectrophotometry, Stellar Temperature
Scientific paper
A spectroscopic analysis of the blue spectrum of DH Cephei is presented together with a study of the radial velocity and light curves. We applied the disentangling method, a novel technique for the reconstruction of the individual spectra of the components of well detached binaries. This method makes it possible to determine the photospheric parameters of the binary components with the same accuracy as for single stars. From an elaborate spectral analysis by means of non-local thermodynamic equilibrium model atmospheres we obtained the following parameters for the primary/secondary: Teff = 44000/43000 +/- 1000K, log geff = 3.95/4.03 +/- 0.15, epsilonHe = 0.09/0.08 +/- 0.02, vr sin i = 192/181 +/- 20 km/s, and the light ratio l = 0.85 +/- 0.02. The spectroscopic orbit parameters have been determined with improved accuracy. The orbit was found to be circular (e less than or equal to 0.04). We determined radial velocity amplitudes of K1 = 213 +/- 6 km/s and K2 = -249 +/- 6 km/s, which corresponds to a mass ratio of q = 0.85 +/- 0.03. The period is P = 2.110912 days. The best fit to the B and V photometry of Lines et al. (1986) yields the following absolute dimensions: inclination i = 47 deg +/- 1 deg, M1 = 29.4 +/- 0.4 solar mass, M2 = 25.0 +/- 0.3 solar mass, Rp, 1 = 8.31 +/- 0.06 solar radius, and Rp, 2 = 7.76 +/- 0.06 solar radius. By comparison with theoretical evolutionary tracks we conclude that DH Cephei is very close to the zero age main sequence. The effective temperatures of the components are higher than predicted by the evolutionary theory of single stars.
Simon K. P.
Sturm Eckhard
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