We present the results of high-resolution spectroscopy of the extremely luminous star Cyg OB2 No. 12. We identified about 200 spectral features in the range 4552–7939 Å, including the interstellar Na I, K I lines and numerous very strong DIBs, along with the He I, C II, and Si II lines. An MK spectral type we derived for the object is B4.5±0.5 Ia+. 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 Hα emission displays broad Thompson wings, a slightly blue-shifted P Cyg type absorption component and a time-variable core absorption. We conclude that the wind is variable in time.

Pinwheel Nebulae are colliding wind binaries (CWB) composed of a Wolf-Rayet star and an early-type star. We first compare our simulations to analytic solutions for CWB. Then we perform large scale 2D simulations of the particular system WR 104. We determine the properties of the gas in the winds and confirm the flow in the spiral has a ballistic motion.

Classical Be (CBe) stars are fast-rotating emission-line stars associated with infrared excess often attributed to plasma free-free emission. A few with exceptionally large near-infrared excess, namely with (J–H) and (H–Ks) both greater than 0.6 mag, however, must be accounted for by thermal emission from circumstellar dust. From 2007 to 2009, spectra of more than 100 CBe stars have been collected. We present some of these spectra and discuss how temporal correlation (or lack of) among spectral features would provide possible diagnosis of the origin of the CBe phenomena.

HD 62623 is one of the very few A-type supergiants showing the B[e] phenomenon. We studied the geometry of its circumstellar envelope in the mid-infrared using the VLTI/MIDI instrument. Using the radiative transfer code MC3D, we managed to model it as a dusty disk with an inner radius of 3.85 AU, an inclination angle of 60°, and a mass of 2 × 10−7M⊙. It is the first time that the dusty disk inner rim of a supergiant star exhibiting the B[e] phenomenon is significantly constrained. The inner gaseous envelope likely contributes up to 20% to the total N band flux and acts like a reprocessing disk. Finally, the hypothesis of a stellar wind deceleration by the companion gravitational effect remains the most probable case since the bi-stability mechanism is not efficient for this star.

Dusty Wolf-Rayet stars are few but remarkable in terms of dust production rates (up to Ṁ = 10−6 M⊙/yr). Infrared excesses associated to mass-loss are found in the sub-types WC8 and WC9. Few WC9d stars are hosting a “pinwheel” nebula, indirect evidence of a companion star around the primary. While few other WC9d stars have a dust shell which has been barely resolved so far, the available angular resolution offered by single telescopes is insufficient to confirm if they also host “pinwheel” nebulae or not. In this article, we present the possible detection of such nebula around the star WR 118. We discuss about the potential of interferometry to image more “pinwheel” nebulae around other WC9d stars.

B[e] stars are among the most peculiar objects in the sky. This spectral type, characterised by allowed and forbidden emission lines, and a large infrared excess, does not represent an homogenous class of objects, but instead, a mix of stellar bodies seen in all evolutionary status. Among them, one can find Herbig stars, planetary nebulae central stars, interacting binaries, supermassive stars, and even “unclassified” B[e] stars: systems sharing properties of several of the above. Interferometry, by resolving the innermost regions of these stellar systems, enables us to reveal the true nature of these peculiar stars among the peculiar B[e] stars.

FS CMa objects are a group of hot stars that exhibit the B[e] phenomenon. The group was defined a few years ago on the basis of the formerly known unclassified B[e] stars and newly discovered objects. One of their main features is the presence of hot circumstellar dust whose properties were unknown. We present IR spectra of nearly 20 FS CMa objects obtained with the Spitzer Space Telescope. Dusty features, such as broad silicate bands in emission and narrow bands that are usually explained by PAHs, are detected. The IR fluxes are compared to those detected by IRAS and MSX. Main results of the data analysis are briefly discussed.

We present preliminary results of a 4-month campaign carried out in the framework of the Mons project, where time-resolved Hα observations are used to study the wind and circumstellar properties of a number of OB stars.

We consider the effect of density distribution evolution on the global one-armed oscillation modes in disks around Be stars. Previous studies of global oscillations in Be disks assumed a power-law density distribution of the disk. However, observational results show that some Be stars exhibit evidence of formation and dissipation of the equatorial disk. This causes the disk density distribution can be far from a power-law form. Performing calculations for several times in the disk formation and dissipation stages, we find one-armed modes confined to the inner part of the disk in both stages. In the disk formation stage, the oscillation frequency stays approximately constant after the disk is fully developed. In the dissipation stage of the Be disk, the local precession frequency is, in general, higher than in the disk formation stage. Thus, we expect that V/R periods become shorter as the innermost part of the disk starts to accrete.

We test whether Be star disks rotate in a Keplerian or an Angular Momentum Conserving fashion. This is done by employing sub-milli arcsecond spectroastrometry around Hα. We spatially resolve the disks, and are the first to do so at such a high spectral resolution. We fit the emission line profiles with parametric models. The Keplerian models reproduce the spectro-astrometry, whereas the AMC models do not, thereby supporting the viscous disk model for Be stars.

We present spectropolarimetric observations of the B[e] supergiant star GG Car at two epochs. Polarization line effects along Hα are analysed using the Q–U diagram. In particular, the polarization position angle (PA) obtained using the line effect allows to constrain the symmetry axis of the disk/envelope. The depolarization line effect around Hα is evident in the Q–U diagram for both epochs, confirming that light from the system is intrinsically polarized. A rotation of the PA along Hα is also observed, indicating a counter-clockwise rotating disk. The intrinsic PA calculated using the line effect (~85°) is consistent between our two epochs, suggesting a clearly defined symmetry axis of the disk.

New spectra of MWC314 are presented; they indicate that the V/R emission line flux ratios show signs of varying in an opposite way to the absorption line radial velocities. The latter appear to be due to apparently non-periodic pulsations, perhaps in strange modes.

We present interferometric observations of the Be star ζ Tau obtained using the MIRC beam combiner at the CHARA Array during four epochs in 2007–2009. Fitting a geometric model to the data reveals a nearly edge-on disk with a FWHM of ~1.8 milli-arcsec in the H-band. The non-zero closure phases indicate an asymmetry in the brightness distribution. Interestingly, when combining our results with previously published interferometric observations of ζ Tau, we find a correlation between the position angle of the disk and the spectroscopic V/R ratio, suggesting that the tilt of the disk might be precessing. This work is part of a multi-year monitoring campaign to investigate the development and outward motion of asymmetric structures in the disks of Be stars.

A new monochromatic imaging and spectral synthesis package for Be stars, based on the bedisk code, is introduced. Example images and spectra are given for for H i and Fe ii. Predicted Fe ii equivalents widths are also compared to recent observations by Arias et al. (2006) and show good agreement, although only for very dense disks.

We discuss the origin of the hard X-rays in γ Cas and its analogs. Of great importance are their temporal correlations with optical/UV signatures, suggesting an origin near the Be star.

Optical and IR spectra, optical to sub-mm photometry, visual imaging polarimetry, and IR high-resolution spectro-interferometry are being used to monitor the new outburst of 28 CMa, which started in 2008 and so far closely resembles previous ones. First modeling based on viscous decretion and focused on constraining the disk viscosity parameter, α, is presented.

The region of the hot end of the main-sequence is hosting pulsating stars of different types and flavours. Pulsations are not only observed for Slowly pulsating B stars (mid to late B-type stars; high order g-modes) and β Cephei stars (early B-type stars; low order p/g-modes) but are also causing variability in Be stars and OB-supergiants. In this review we give an overview of the asteroseismic observations that are currently available for these types of stars. The first asteroseismic results were solely based on ground-based observations. Recently, the arrival of space-based data gathered by space missions like most, corot and kepler has led to important discoveries for massive stars, highlighting their excellent asteroseismic potential. We show that, despite the unprecedented precision of the space-based data, there is still a clear need for ground-based follow-up observations.

Photometry of Wolf-Rayet (WR) stars obtained with the first Canadian space telescope MOST (Microvariability and Oscillations of STars) has revealed multimode oscillations mainly in continuum light that suggest stellar pulsations could be a significant contributing factor to the mass-loss rates. Since the first clear detection of a pulsation period of P = 9.8h in WR123, two other stars have also shown periods of a few days, which must be related to stellar pulsations.

The corot and kepler space missions are collecting very high-precision long-duration photometric data of many Be stars, allowing us to better understand the origin of their short-term variability and the link between these variations and the Be phenomenon. In this paper, we present a brief summary of the results obtained in the analysis of several Be stars observed with corot in terms of pulsations. In addition, we show that variations of the Be star HD 175869 can be explained as two active regions separated by 150 degrees or as unstable pulsating modes in a star with an extensive mixing in radiative layers corresponding to a core overshooting of 0.35Hp. A preliminary study of the photometric and spectroscopic variability seen in the B1.5IVe star HD 51193 is performed. Currently the kepler satellite is observing the only confirmed Be star in its field of view, namely KIC 6954726. From low-resolution spectra we derived a spectral type of B2.5Ve for this star and we studied the long-term variation of the emission in the Hα line. The 3.5-year kepler light curve will allow us to detect even more close frequencies than with corot and to perform a detailed analysis of the amplitude variations in a Be star.

A review of the ability of asteroseismology to probe the internal physics of OB stars is presented. The main constraints that can be obtained from the frequency spectrum in p- and g-modes pulsators are discussed. Next, we consider energetic aspects of the pulsations in OB stars and show how such study also allows to constrain their internal physics. The cases of p-mixed modes (β Cep stars), g-modes (SPB stars), strange modes and stochastically excited modes are considered.