相关论文: More nitrogen rich B-type stars in the SMC cluster…

High-resolution UVES/VLT spectra of B12, an extreme pole-on Be star in the SMC cluster NGC330, have been analysed using non-LTE model atmospheres to obtain its chemical composition relative to the SMC standard star AV304. We find a general…

We have previously analysed the spectra of 135 early B-type stars in the LMC and found several groups of stars that have chemical compositions that conflict with the theory of rotational mixing. Here we extend this study to Galactic and SMC…

The AF-supergiants in the Galaxy and the SMC allow us to examine predictions from evolution models through their CNO abundances. In these proceedings, we recalculate the NLTE nitrogen abundances in 22 Galactic and 9 SMC A-supergiants using…

Analyses of large spectroscopic surveys of early-type stars in the LMC have found an excess of nitrogen enriched B-type targets with a vsini<40 km/s compared with the predictions of single star evolutionary models incorporating rotational…

Observations of hot stars belonging to the young cluster SMC-NGC330 and its surrounding region were obtained with the VLT-GIRAFFE facilities in MEDUSA mode. We investigated the B and Be star properties and proportions in this environment of…

Rotational mixing in massive main sequence stars is predicted to monotonically increase their surface nitrogen abundance with time. We use this effect to design a method for constraining the age and the inclination angle of massive main…

Evolutionary models for massive stars, accounting for rotational mixing effects, do not predict any core-processed material at the surface of B dwarfs with low rotational velocities. Contrary to theoretical expectations, we present a…

Photospheric nitrogen abundances for a sample of 26 Be stars and 16 normal B stars were found using high-resolution spectra from the Magnetism in Massive Stars (MiMeS) spectroscopic survey. Nitrogen abundances were obtained using non-LTE…

Aims. We compare the predictions of evolutionary models for early-type stars with atmospheric parameters, projected rotational velocities and nitrogen abundances estimated for a sample of Be-type stars. Our targets are located in 4 fields…

New abundances of N, O, Na, Mg, Si, Ca, Sc, Ti, Cr, Fe, Sr, Zr, and Ba are presented for 10 A-type supergiants in the SMC, plus upper limits for C. In interpreting the CNO results for constraints on stellar evolution theories, careful…

The number ratios Be/(B+Be) of Be to B-type stars in young, well studied clusters of the Galaxy, the LMC and SMC are examined. In order to disentangle age and metallicity effects we choose clusters in the same age interval and for which…

Star clusters are privileged laboratories for studying the evolution of massive stars (OB stars). One particularly interesting question concerns the phases, during which the classical Be stars occur, which unlike HAe/Be stars, are not…

The origin of initial rotation rates of stars, and how a star's surface rotational velocity changes during the evolution, either by internal angular momentum transport or due to interactions with a binary companion, remain open questions in…

In this paper we review the observational data for OB stars in the SMC concentrating on those aspects of their spectra which provide information on processes which may strongly influence their evolution, namely mass-loss, rotational mixing…

Rotation has become an important element in evolutionary models of massive stars, specifically via the prediction of rotational mixing. Here, we study a sample of stars, including rapid rotators, to constrain such models and use nitrogen…

High resolution optical spectra of 57 Galactic B-type supergiant stars have been analyzed to determine their rotational and macroturbulent velocities. In addition, their atmospheric parameters (effective temperature, surface gravity and…

Using new accurate fundamental parameters of 30 Galactic A and F supergiants, namely their effective temperatures Teff and surface gravities log g, we implemented a non-LTE analysis of the nitrogen abundance in their atmospheres. It is…

We search for effects of metallicity on B and Be stars in the Small and Large Magellanic Clouds (SMC and LMC) and in the Milky Way (MW). We extend our previous analysis of B and Be stars populations in the LMC to the SMC. The rotational…

We present the results of a detailed NLTE abundance study of nine beta Cephei stars, all of them being prime targets for theoretical modelling: gamma Peg, delta Cet, nu Eri, beta CMa, xi1 CMa, V836 Cen, V2052 Oph, beta Cep and DD (12) Lac.…

Previous analyses of the spectra of OB-type stars in the Magellanic Clouds have identified targets with low projected rotational velocities and relatively high nitrogen abundances. The VFTS obtained spectroscopy for B-type 434 stars. We…