Stellar physical properties of star clusters are poorly known and the cluster parameters are often very uncertain. Our goals are to perform a spectrophotometric study of the B star population in open clusters to derive accurate stellar parameters, search for the presence of circumstellar envelopes, and discuss the characteristics of these stars. The BCD spectrophotometric system is a powerful method to obtain stellar fundamental parameters from direct measurements of the Balmer discontinuity. To this end, we wrote the interactive code MIDE3700. The BCD parameters can also be used to infer the main properties of open clusters: distance modulus, color excess, and age. Furthermore, we inspected the Balmer discontinuity to provide evidence for the presence of circumstellar disks and identify Be star candidates. We used an additional set of high-resolution spectra in the H{alpha} region to confirm the Be nature of these stars. We provide Teff, logg, Mv, Mbol, and spectral types for a sample of 68 stars in the field of the open clusters NGC6087, NGC6250, NGC6383, and NGC6530, as well as the cluster distances, ages, and reddening. Then, based on a sample of 230 B stars in the direction of the 11 open clusters studied along this series of three papers, we report 6 new Be stars, 4 blue straggler candidates, and 15 B-type stars (called Bdd) with a double Balmer discontinuity, which indicates the presence of circumstellar envelopes. We discuss the distribution of the fraction of B, Be, and Bdd star cluster members per spectral subtype. The majority of the Be stars are dwarfs and present a maximum at the spectral type B2-B4 in young and intermediate-age open clusters (<40Myr). Another maximum of Be stars is observed at the spectral type B6-B8 in open clusters older than 40Myr, where the population of Bdd stars also becomes relevant. The Bdd stars seem to be in a passive emission phase. Our results support previous statements that the Be phenomenon is present along the whole main sequence band and occurs in very different evolutionary states.We find clear evidence of an increase of stars with circumstellar envelopes with cluster age. The Be phenomenon reaches its maximum in clusters of intermediate age (10-40Myr) and the number of B stars with circumstellar envelopes (Be plus Bdd stars) is also high for the older clusters (40-100Myr).
The BT-COND Model grid of theoretical spectra. Brown dwarfs/extrasolar planets atmosphere models without irradiation and no dust opacity (no dust settling) but updated abundances. Wavelengths have been converted to air wavelengths.
The BT-DUSTY Model grid of theoretical spectra. Brown dwarfs/extrasolar planets atmosphere models without irradiation but including dust opacity (fully efficient dust settling) and updated abundances. Wavelengths have been converted to air wavelengths.
The NextGen Model grid of theoretical spectra; Gas phase only, valid for Teff > 2700 K. Updated opacities. Wavelengths have been converted to air wavelengths.
The NextGen Model grid of theoretical spectra; Gas phase only, valid for Teff > 2700 K. Updated opacities. Wavelengths have been converted to air wavelengths.
We have used recent Kurucz models and many standard stars to revise previous calibrations of the Geneva photometric parameters in terms of Teff, logg, and [M/H]. In addition, new parameters pT and pG were defined, which are the Geneva equivalents of Stromgren's a and r parameters and allow to estimate Teff and logg for stars with intermediate temperature (spectral type A0-A3). A fortran code (calib.f) has been written, which applies our calibration to stars measured in the Geneva system. A conspicuous change in slope appears in the grid d vs B2-V1. It seems to be linked with the onset of convection in the superficial layers of the star's envelope.
The BT-Settl Model grid of theoretical spectra; With a cloud model, valid across the entire parameter range. Wavelengths have been converted to air wavelengths.
The BT-Settl Model grid of theoretical spectra; With a cloud model, valid across the entire parameter range. Using AGSS2009 abundances. Wavelengths have been converted to air wavelengths.
The BT-Settl Model grid of theoretical spectra. With a cloud model, valid across the entire parameter range and using the Caffau et al. (2011) solar abundances. Wavelengths have been converted to air wavelengths.
