Related papers: The yellow hypergiant - B[e] supergiant connection

We have studied a sample of 28 periodically variable B-type supergiants selected from the HIPPARCOS mission and 12 comparison stars covering the whole B-type spectral range. Our goal is to test if their variability is compatible with…

Blue supergiant stars of B and A spectral types are amongst the visually brightest non-transient astronomical objects. Their intrinsic brightness makes it possible to obtain high quality optical spectra of these objects in distant galaxies,…

The extreme luminosities of hot, massive stars drive strong stellar winds through UV line-scattering. For OB stars with an orbiting circumstellar disk, we explore the effect of such line-scattering in ablating disk material, initially…

Close to a black hole, the density of the sub-Keplerian accreting matter becomes higher compared to a spherical flow due to the presence of a centrifugal barrier independent of whether or not a standing shock actually forms. This hot dense…

The heavily obscured open cluster Berkeley~51 shows characteristics typical of young massive clusters, even though the few previous studies have suggested older ages. We combine optical ($UBV$) and 2MASS photometry of the cluster field with…

Newly formed planets (or brown dwarfs) may possess disks or rings that occupy an appreciable fraction of the planet's Hill sphere and extend beyond the Laplace radius, where the tidal torque from the host star dominates over the torque from…

The processes taking place in the outermost reaches of spiral disks (the 'proto-disk') are intimately connected to the build-up of mass and angular momentum in galaxies. The thinness of spiral disks suggests that the activity is mostly…

The co-planarity of solar-system planets led Kant to suggest that they formed from an accretion disk, and the discovery of hundreds of such disks around young stars as well as hundreds of co-planar planetary systems by the Kepler satellite…

In the summer and fall of 2000 the yellow hypergiant Rho Cassiopeiae dimmed by more than a visual magnitude, while its effective temperature decreased from \~7000 K to below 4000 K over ~200 d. We observed the highest mass-loss rate of ~5 %…

We discuss an interesting feature of the distribution of luminous blue variables on the H-R diagram, and we propose a connection with the bistability jump in the winds of early-type supergiants. There appears to be a deficiency of quiescent…

Mergers between helium white dwarfs and main-sequence stars are likely common, producing red giant-like remnants making up roughly a few percent of all low-mass ($\lesssim2M_\odot$) red giants. Through detailed modeling, we show that these…

The dust disk around Beta Pictoris must be produced by collision or by evaporation of orbiting Kuiper belt-like objects. Here we extend the already proposed Orbiting-Evaporating-Bodies (OEB) scenario in which the disk is a gigantic…

Context. The fate of a massive star during the latest stages of its evolution is highly dependent on its mass-loss rate/geometry and therefore knowing the geometry of the circumstellar material close to the star and its surroundings is…

Chandra X-ray and HST far-ultraviolet (FUV) observations of three early-F supergiants have shed new light on a previous puzzle involving a prominent member of the class: Alpha Persei (HD20902: F5Ib). The warm supergiant is a moderately…

Thanks to significant improvements in high-resolution spectrographs and the launch of dedicated space missions MOST, CoRoT and Kepler, the number of subgiants and red-giant stars with detected oscillations has increased significantly over…

Around 2% of all A stars have photospheres depleted in refractory elements. This is hypothesized to arise from a preferential accretion of gas rather than dust, but the specific processes and the origin of the material -- circum- or…

It is surprising to find dust around B type stars, as in the case of B[e] stars. These stars exhibit a dense, dusty environment witnessed by their infrared-excess and many emission lines from permitted and forbidden transitions. Given the…

We present deep, high angular resolution near-infrared images of the obscured Galactic Giant H II region NGC3576. Our images reach objects to ~3M_sun. We collected high signal-to-noise K-band spectra of eight of the brightest objects, some…

Ring nebulae are often found around massive stars such as Wolf-Rayet stars, OB and Of stars and Luminous Blue Variables (LBVs). In this paper we report on two ring nebulae around blue supergiants in the Large Magellanic Cloud. The star…

The quadruple young stellar system HD 98800 consists of two spectroscopic binary pairs with a circumbinary disk around the B component. Recent work by Boden and collaborators using infrared interferometry and radial velocity data resulted…