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The present work is devoted to the study of faint Be stars observed by CoRoTin the fourth long run (LRA02). The astrophysical parameters were determinedfrom the spectra observed with the VLT/FLAMES instruments at ESO. Spectra werefitted with models of stellar atmospheres using our GIRFIT package. Spectra inthe lambda-lambda 6400-7200$ AA domain enabled the confirmation or a firstidentification of Be star candidates. The apparent parameters (Teff,log g,Vsini) for a set of 19 B and Be stars were corrected for the effects induced by therapid rotation. These allowed us to determine: 1) masses that are in agreementwith those measured for detached binary systems; 2) distances that agree withthe GAIA parallaxes; and 3) centrifugal/gravity equatorial force ratios of~0.6-0.7, which indicate that our Be stars are subcritical rotators. A study ofthe Balmer Halpha, Hgamma and Hdelta emission lines produced: extents of thecircumstellar disk (CD) emitting regions that agree with the interferometricinferences in other Be stars; R-dependent exponents n(R) of the CD radialdensity distributions; CD base densities. The Hgamma and Hdelta emission linesare formed in CD layers close to the central star. These lines produced adifferent value of the exponent n(R) than assumed for Halpha. Further detailedstudies of Hgamma and Hdelta emission lines could reveal the physicalproperties of regions where the viscous transport of angular momentum to theremaining CD regions is likely to originate from. The subcritical rotation ofBe stars suggests that their huge discrete mass-ejections and concomitantnon-radial pulsations might have a common origin in stellar envelope regionsthat become unstable to convection due to rotation. The errors induced on theestimated Teff by the possible presence of stripped sub-dwarf O/B companionsare not likely to exceed their present uncertainties.

astronomy and astrophysics

Study of a Sample of Faint Be Stars in the Exofield of CoRoT. Part III.  Global Spectroscopic Characterization and Astrophysical Parameters of the  Central Stars