The Inhomogeneous Wind of the LBV Candidate CygOB2-No.12

We present the results of high-resolution spectroscopy of the extremely luminous star CygOB2-No.12. We identified about 200 spectral features in the range 4552-7939 AA, including the interstellar NaI, KI lines and numerous very strong DIBs, along with the HeI, CII, and SiII lines. An MK spectral type we derived for the object is B4.5Ia+. Our analysis of the radial velocity data shows the presence of a gradient in the stellar atmosphere, caused by both atmospheric expansion and matter infall onto the star. The Halpha emission displays broad Thompson wings, a slightly blue-shifted PCyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.Comment: 3 pages, 2 figures, IAU Symposium No.272 "Active OB stars: structure, evolution, mass loss and critical limits", 201

On Protostellar Disks in Herbig Ae/Be Stars

The spectral shape of IR emission from Herbig Ae/Be stars has been invoked as evidence for accretion disks around high-mass protostars. Instead, we present here models based on spherical envelopes with $r^{-1.5}$ dust density profile that successfully explain the observed spectral shapes. The spectral energy distributions (SEDs) of eight primary candidates for protostellar disks are fitted in detail for all wavelengths available, from visual to far IR. The only envelope property adjusted in individual sources is the overall visual optical depth, and it ranges from 0.3 to 3. In each case, our models properly reproduce the data for both IR excess, visual extinction and reddening. The success of our models shows that accretion disks cannot make a significant contribution to the radiation observed in these pre-main sequence stars.Comment: 10 pages, 2 Postscript figures (included), uses aaspp4.sty. To appear in Astrophysical Journal Letter

The B[e] phenomenon in the Milky Way and Magellanic Clouds

Discovered over 30 years ago, the B[e] phenomenon has not yet revealed all its puzzles. New objects that exhibit it are being discovered in the Milky Way, and properties of known objects are being constrained. We review recent findings about objects of this class and their subgroups as well as discuss new results from studies of the objects with yet unknown nature. In the Magellanic Clouds, the population of such objects has been restricted to supergiants. We present new candidates with apparently lower luminosities found in the LMC.Comment: 5 pages, 2 figures, IAU Symposium 272, Active OB stars: structure, evolution, mass loss and critical limit

VY Mon - the twin of Z CMa?

In 1985-1990 we obtained photometric, polarimetric and spectroscopic observations of the peculiar emission-line star VY Mon. These observational data were compared with those of Z CMa. To our opinion the similarity of the observational features of these stars is due to their similar nature

Binaries Among Be Stars

Binarity as an explanation of some observed properties of Be stars, such as the fast rotation and the presence of circumstellar disks, was suggested nearly 40 years ago. Although not well accepted initially because of the lack of supporting data, this hypothesis gained solid grounds with the advent of high resolution spectroscopy. Many bright Be stars have been recognized as primary components of binary systems over the last two decades. I will review the current binary statistics among Be stars, discuss methods of detecting binaries, and briefly present recent results on newly found binary systems

The remarkable outburst of the highly evolved post-period-minimum dwarf nova SSS J122221.7-311525

We report extensive 3-yr multiwavelength observations of the WZ Sge-type dwarf nova SSS J122221.7-311525 during its unusual double superoutburst, the following decline and in quiescence. The second segment of the superoutburst had a long duration of 33 d and a very gentle decline with a rate of 0.02 mag d-1, and it displayed an extended post-outburst decline lasting at least 500 d. Simultaneously with the start of the rapid fading from the superoutburst plateau, the system showed the appearance of a strong near-infrared excess resulting in very red colours, which reached extreme values (B - I ? 1.4) about 20 d later. The colours then became bluer again, but it took at least 250 d to acquire a stable level. Superhumps were clearly visible in the light curve from our very first time-resolved observations until at least 420 d after the rapid fading from the superoutburst. The spectroscopic and photometric data revealed an orbital period of 109.80 min and a fractional superhump period excess ?0.8 per cent, indicating a very low mass ratio q ? 0.045. With such a small mass ratio the donor mass should be below the hydrogen-burning minimum mass limit. The observed infrared flux in quiescence is indeed much lower than is expected from a cataclysmic variable with a near-main-sequence donor star. This strongly suggests a brown-dwarf-like nature for the donor and that SSS J122221.7-311525 has already evolved away from the period minimum towards longer periods, with the donor now extremely dim

Optical and near-infrared photometry of the Vega-excess star SAO 26804=HD 233517

UBVRUHK photometry of the Vega-excess star SAO 26804=HD 233517 and several stars of its environments obtained at the I-meter telescope of the Tien-Shan Observatory in Kazakhstan is presented. It is shown that the star has a later spectral type than has been considered oreviously. Its effective temperature is estimated by the visual surface brightness method as 4170 K. The star has no excess radiation in the range of 0.3-2.5 um. A comparison of its IR-excesses with those of other K-type stars with IR-excesses is made. HD 233517 is probably more evolved than SAO 179815=HD 98800 having a very similar intrinsic spectral energy distribution (SED) and the largest IR-excess among K-type stars from the SAO catalogue

Far-infrared excesses in classical Be stars

A sample of Be stars with large far-infrared excesses detected by IRAS is selected and their high-resolution IRAS images are examined. The far-infrared emission from most of them is marginally extended and is associated with the optical sources. Modeling of the stars' spectral energy distributions allows us to rule out the infrared cirrus nature of the excesses. We suggest that the excesses are more likely due to circumstellar dust, possibly formed early in the evolution of the star

High State of Ha Emission Activity of the Herbig Be Star HD 200775

We present the results of high-resolution spectroscopic observations of the pre–main-sequence Herbig Be star HD 200775 obtained between 1994 September and 1998 February. Strong variations of the Ha line associated with an extended period of strong emission during the summer and fall of 1997 have been observed. The line equivalent width took on the highest value reported in the last 20 yr. A review of the observational literature dating back to 1977 indicates periodic behavior of the Ha equivalent width with a period of 3.68 yr. These variations might be due to interaction between the stellar wind and the protostellar envelope, as suggested previously by Beskrovnaya et al., or to an effect of a possible close companion, such as those detected in some classical Be stars. The next high emission state is predicted to occur in the first half of 2001. We emphasize the importance of coordinated photometric and high-resolution spectroscopic observations for further understanding of the star’s behavior