Related papers: B[e] Supergiants' circumstellar environment: disks…
The central regions of galaxies show the presence of massive black holes and/or dense stellar systems. The question about their modes of formation is still under debate. A likely explanation of the formation of the central dense stellar…
High-resolution UCLES/AAT spectra are presented for nine B-type supergiants in the SMC, chosen on the basis that they may show varying amounts of nuclear-synthetically processed material mixed to their surface. These spectra have been…
Planet migration in protoplanetary discs plays an important role in the longer term evolution of planetary systems, yet we currently have no direct observational test to determine if a planet is migrating in its gaseous disc. We explore the…
A key challenge for protoplanetary disks and planet formation models is to be able to make a reliable connection between observed structures in the disks emission, like bright and dark rings or asymmetries, and the supposed existence of…
Spectroscopic analyses of 7 SMC B-type supergiants and 1 giant have been undertaken using high resolution optical data obtained on the VLT with UVES. FASTWIND, a non-LTE, spherical,line-blanketed model atmosphere code was used to derive…
Most of massive stars form in binary or higher-order systems in clumpy, sub-structured clusters. In the very first phases of their life, these stars are expected to interact with the surrounding environment, before being released to the…
A statistical study of the environment around Polar Ring Galaxies is presented. Two kinds of search are performed: 1) a study of the concentration and diameters of all the objects surrounding the Polar Rings, within a search field 5 times…
The current picture painted by the observations of circumstellar dust at white dwarfs, and the consequent atmospheric pollution, is of a surviving planetary system. This chapter recounts in detail both the discovery and empirical…
The medium around massive stars is strongly shaped by the stellar winds. Those winds depend on various stellar parameters (effective temperature, luminosity, chemical composition, rotation, ...), which are varying as a function of the time.…
Star forming galaxies exhibit a variety of physical conditions, from quiescent normal spirals to the most powerful dusty starbursts. In order to study these complex systems, we need a suitable tool to analyze the information coming from…
Spitzer IRS spectroscopy supports the interpretation that BP Piscium, a gas and dust enshrouded star residing at high Galactic latitude, is a first-ascent giant rather than a classical T Tauri star. Our analysis suggests that BP Piscium's…
The characteristics of the various types of B[e] stars are discussed and compared with those of classical Be stars. Both groups of stars are characterized by the presence of emission lines in their spectra, in particular of hydrogen.…
In the local (redshift z~0) Universe, collisional ring galaxies make up only ~0.01% of galaxies and are formed by head-on galactic collisions that trigger radially propagating density waves. These striking systems provide key snapshots for…
Massive stars in their late stages of evolution as Red Supergiants experience mass loss. The resulting winds show various degrees of dynamical and chemical complexity and produce molecules and dust grains. This review summarises our…
The formation environment of stars in massive stellar clusters is similar to the environment of stars forming in galaxies at a redshift of 1 - 3, at the peak star formation rate density of the Universe. As massive clusters are still forming…
Self-gravitating protostellar discs are unstable to fragmentation if the gas can cool on a time scale that is short compared to the orbital period. We use a combination of hydrodynamic simulations and N-body orbit integrations to study the…
The recent discoveries of circumbinary planets by $\it Kepler$ raise questions for contemporary planet formation models. Understanding how these planets form requires characterizing their formation environment, the circumbinary…
The recent detections of extrasolar giant planets has revealed a surprising diversity of planetary system architectures, with many very unlike our Solar System. Understanding the origin of this diversity requires multi-wavelength studies of…
It has been suggested that circumstellar disks evolve from dense, actively accreting structures to low-mass, replenished remnants. During this transition, grains may assemble into planetesimals, or the disk may be cleared by newborn…
Theories of planet formation predict the birth of giant planets in the inner, dense, and gas-rich regions of the circumstellar disks around young stars. These are the regions from which strong CO emission is expected. Observations have so…