¹ Laboratorio de Astrofísica Espacial y Física Fundamental, INTA, Apdo. Correos 50727, E-28080 Madrid, Spain
² Universidad SEK, Cardenal Zúñiga s/n, E-40003 Segovia, Spain
³ Space Sciences Laboratory, University of California, Berkeley, CA 94720-7304
⁴ Harvard-Smithsonian Center for Astrophysics, MS-3, 60 Garden Street, Cambridge, MA 02138

Spectra of B stars in the wavelength range of 911-1100 Å have been obtained with the EURD spectrograph onboard the Spanish satellite MINISAT-01 with 5 Å spectral resolution. IUE spectra of the same stars have been used to normalize Kurucz models to the distance, reddening and spectral type of the corresponding star. The comparison of 8 main-sequence stars studied in detail ( Vir,  Tau,  Tau,  Tau,  Leo,  Lib,  Oph, and  Sgr) shows agreement with Kurucz models, but observed fluxes are 10-40% higher than the models in most cases. The difference in flux between observations and models is higher in the wavelength range between Lyman and Lyman . We suggest that Kurucz models underestimate the FUV flux of main-sequence B stars between these two Lyman lines. Computation of flux distributions of line-blanketed model atmospheres including non-LTE effects suggests that this flux underestimate could be due to departures from LTE, although other causes cannot be ruled out. We found the common assumption of solar metallicity for young disk stars should be made with care, since small deviations can have a significant impact on FUV model fluxes. Two peculiar stars ( Leo and  Aqr), and two emission line stars ( Cap and  Aqr) were also studied. Of these, only  Aqr has a flux in agreement with the models. The rest have strong variability in the IUE range and/or uncertain reddening, which makes the comparison with models difficult.

Accepted by The Astrophysical Journal
Preprints from morales@laeff.esa.es
or on the web at http://xxx.lanl.gov/abs/astro-ph/0012220/