We report on detailed studies of the absorption line spectrum and spectroscopic orbit of the binary BN2.5Ib star HD 235679. We also give ao preliminary report on our study of the Hα emission line profiles from this perplexing system. Hipparcos and Tycho2 astrometric data allow us to place limits on the distance to the system. The lack of a measurable reflection effect in the Hipparcos photometry allows us to rule out the possibility that the massive invisible star is cool and fills its Roche lobe. Thus, by process of elimination, the invisible star must be hot or a black hole. The properties of the Hα profiles suggest that the invisible star is somewhat hotter, and has a stronger wind than HD235679.
The progress in the investigation of Be stars during the past decade was enabled mainly thanks to high-resolution echelle spectrographs. Such instruments made possible to carry out multi-line studies of line profile variations and to search for correlations between photospheric and circumstellar phenomena. The Heros team was one of the most active in this field during the last decade. Here we summarize the most important achievements reached by the group.
The corona status of our knowledge of the HR 2142 system is reviewed. The massflow in the system and its long-term behavior are currently being studied using IUE HIRES data obtained between 1979-95 and archival Copernicus observations acquired in the late 1970s. Some recent results are summarized here. The strength and velocity behavior of the infall components to the Si II, IV lines seen during the primary shell phase from φ ~0.70-0.98 resemble that observed in conventional Algol systems. The inferred mass infall rate of ~10^-7 M⊕ yr^-1, however, is too small to account for the massive Hα-emitting disk about the primary. The cause for the mass outflow observed during the secondary shell phase is still unknown. The nature of the secondary star, which remains undetected, is discussed. The small amount of residual flux in the UV that might be attributed to the secondary weakens the assumption that it must be an O subdwarf as in the φ Per system, but further studies are warranted.
We give an introduction to interferometrical concepts and their applicability to Be stars. The first part of the paper concen trates on a short historic overview and basic principles of two-beam interferometric observations. In the second part, the VLTI/MIDI instrument is introduced and its first results on Be stars, obtained on α Ara and δ Cen, are outlined.
The short-time scale spectroscopic variability of some Be stars has been mvestigated with an optical fiber spectrograph and a CCD camera. We have found on time-scale of hours and days: -1) weak changes in the Hα emission line profile of yCas; -2) changes in the structure and the intensity of the Hα emission line core and sometimes in the wings of the Hel λ 6678 of φPer; -3) no table variations in the Hel photospheric line profile λ 6678 and in the core of the Hα absorption line of o And, which do not seem correlated with the photometric period 1.57 days given by Harmanec (1984).