Related papers: Using the Coolest Ae Stars to Constrain Circumstel…
In this paper we study the evolution of viscous and radiative circumstellar disks under the influence of a companion star. We focus on the eccentric {\gamma} Cephei and {\alpha} Centauri system as examples and compare the disk quantities…
We discuss the basic hydrodynamics that determines the density structure of the disks around hot stars. Observational evidence supports the idea that these disks are Keplerian (rotationally supported) gaseous disks. A popular scenario in…
Hot, massive stars (spectral types O and B) have extreme luminosities ($10^4 -10^6 L_\odot$) that drive strong stellar winds through UV line-scattering. Some massive stars also have disks, formed by either decretion from the star (as in the…
Context. Evolution of massive stars is affected by a significant loss of mass either via (nearly) spherically symmetric stellar winds or by aspherical mass-loss mechanisms, namely the outflowing equatorial disks. However, the scenario that…
The temperature structure of Be star circumstellar disks at the sub-solar metallicity appropriate to the Small Magellanic Cloud (SMC) is investigated. It is found that for central stars of the same spectral type, Be star disks in the SMC…
This paper summarizes several results concerning the comparison between accretion-related properties of cool (T Tauri; T < 7000 K, M < 1 Msun and hot (Herbig Ae/Be; 7000 < T(K) < 13000; 1 < M(Msun) < 6) pre-main sequence (PMS) stars. This…
We study the emission and absorption of CO ro-vibrational lines in the spectra of intermediate mass pre-main-sequence stars with the aim to determine both the spatial distribution of the CO gas and its physical properties. We also aim to…
We have analysed high-resolution spectra of 28 A and 22 F stars in the Kepler field, observed with the FIES spectrograph at the Nordic Optical Telescope. We provide spectral types, atmospheric parameters and chemical abundances for 50…
This paper presents a detailed statistical determination of the equatorial rotation rates of classical Be stars. The rapid rotation of Be stars is likely to be linked to the ejection of gas that forms dense circumstellar disks. The physical…
We study the molecular content and chemistry of a circumstellar disk surrounding the Herbig Ae star AB Aur at (sub-)millimeter wavelengths. Our aim is to reconstruct the chemical history and composition of the AB Aur disk and to compare it…
We performed the slitless spectroscopic survey to identify Classical (CBe) stars in open clusters older than 100 Myr. Observing a sample of 71 open clusters, we identified 13 CBe stars in 11 open clusters, one of, which (TYC 2679-432-1) is…
*Context The evolution of young massive protoplanetary disks toward planetary systems is expected to include the formation of gaps and the depletion of dust and gas. *Aims A special group of flaring disks around Herbig Ae/Be stars do not…
Be stars possess gaseous circumstellar decretion disks, which are well described using standard $\alpha$-disk theory. The Be star 28 CMa recently underwent a long outburst followed by a long period of quiescence, during which the disk…
The observed emission lines of Be stars originate from a circumstellar Keplerian disk that are generally well explained by the Viscous Decretion Disk model. In an earlier work we performed the modeling of the full light curve of the bright…
We investigate variations in the linear polarization as well as in the V-band and B-band colour-magnitudes for classical Be star disks. We present two models: disks with enhanced disk density and disks that are tilted or warped from the…
Context: The geometry of the circumstellar envelopes (CSE) surrounding Be stars is still uncertain, although it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. Achernar (Alpha Eri) is the…
(abbreviated) We report detection with the Spitzer Space Telescope of cool dust surrounding solar type stars. The observations were performed as part of the Legacy Science Program, ``Formation and Evolution of Planetary Systems'' (FEPS).…
We investigate the structure of accretion disks around massive protostar applying steady state models of thin disks. The thin disk equations are solved with proper opacities for dust and gas taking into account the huge temperature…
We present a series of 2-d ($r,\phi$) hydrodynamic simulations of marginally self gravitating disks around protostars using an SPH code. We implement simple dynamical heating and we cool each location as a black body, using a photosphere…
A search for previously undetected optically thin disks around stars in the nearby, young, TW Hydrae Association was conducted around sixteen stars with sensitive 12 and 18 micron photometry. The survey could detect Zodiacal-like dust, with…