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

Revealing the nature of the B[e] star MWC 342

We carried out an analysis of existing multicolor photometry and optical spectroscopy of MWC 342, a B[e] star with an uncertain evolutionary state. The star shows a gradual brightening in the optical and near-IR regions, while its Balmer lines demonstrate a relative stability of their shapes over the last 50 years. Recent high-resolution spectroscopic observations did not reveal the presence of photospheric lines. The hypotheses about the nature of MWC 342 suggested in the literature are briefly discussed. It is shown that the object’s properties, such as the Balmer line profiles and shapes of the IR excess, are similar to those of several other B[e] stars including MWC 84 = CI Cam, which underwent a strong outburst in April 1998. We suggest that MWC 342 is likely to be an evolved object, perhaps a binary system with a compact secondary, which may also undergo an outburst in the nearest future

Time-dependent spectral-feature variations of stars displaying the B[e] phenomenon III. HD 50138

Context. B[e] stars are anomalous objects around which extended circumstellar matter is present. The observed properties of the central star are significantly affected by the surrounding material. Therefore, the use of standard synthetic spectra is disputable in this case and our capability to study these objects is limited. One of the possibilities is to analyse variations of the spectral features. Long-term spectroscopic observations are required for this, but are not found in the literature. For our study we choose the B[e] star HD 50138 of the FS CMa type because of the indication that this star is a post-main-sequence star, although still not highly evolved. Therefore, it can be a good object for testing evolutionary models. Currently, HD 50138 is the most extensively observed FS CMa star which makes it an ideal object for modelling. Our observations fill the gap in the available data.Aims. To describe the variability of HD 50138 we have monitored this star spectroscopically over the last twenty years. To search for the periodicity on short-term scales, series of night-to-night observations were also obtained. We were able to obtain 130 spectra from four different telescopes – 1.06 m at Ritter Observatory (échelle, R ~ 26 000, 32 spectra, 1994-2003), the Perek 2 m telescope at Ondrejov Observatory (slit, R ~ 12 500, 56 spectra, 2004-2013), the 2.12 m telescope at Observatorio Astronomico Nacional San Pedro Martir (échelle, R ~ 18 000, 16 spectra, 2005-2013), and the 0.81 m telescope at Three College Observatory (échelle, R ~ 12 000, 26 spectra, 2013-2014).Methods. We describe and analyse variations of the chosen lines. The measurements of the equivalent widths and radial velocities of the Ha, Hß, and [O?i] ?? 6300, 6364 Å lines are presented. The set of obtained spectra allows us to describe the changes on timescales from days to years.Results. The long-term quasi-periodic trend was found in the variations of the Ha equivalent width and confirmed by time dependent studies of the relative flux and equivalent width of the [O?i] 6300 Å line and radial velocity of the Ha violet peak. The two long periods of 3000 ± 500and 5000 ± 1000 days were detected there. We were able to catch moving humps in the Ha line, which reveal the rotating media around the star. An analysis of the correlation of equivalent widths, radial velocities, relative fluxes, and V/R ratios for various lines is presented in detail.Conclusions. We describe the spectral variability of HD 50138 over the last twenty years. Based on these data, we determine new restrictions for future modelling. We confirm the quasi-periodic behaviour of the object’s spectral variability, which probably reflects mass transfer in a binary system. This behaviour also supports a recently introduced explanation of the nature of FS CMa stars as post-merger systems

Polaris: History of Pulsation Activity since Discovery

The pulsation activity of small-amplitude Cepheid Alpha UMi (Polaris) during the period of its radial velocity observations has been analyzed. In the 20th century, Polaris was known to demonstrate a decrease in radial velocity amplitude to the minimum, in the 1980s. Thereafter, the amplitude has increased. The observations of September-December 2015 (21 spectra) obtained by 81cm telescope TCO with spectrograph have showed that radial velocity amplitude comes to 4.16 km/s and is approximately twice higher than the estimates made in 2007, with pulsation period adding 8.6 min