Context. The radius of a star is a very important constraint to evolutionary models, particularly when combined with asteroseismology. Diameters can now be measured interferometrically with great precision (better than 1%), but the center-to-limb darkening (CLD) remains a potential source of bias. Measuring this bias is possible by completely resolving the star using long-baseline interferometr...

We present a simple theoretical framework for massive galaxies at high redshift, where the main assembly and star formation occurred, and report on the first cosmological simulations that reveal clumpy disks consistent with our analysis. The evolution is governed by the interplay between smooth and clumpy cold streams, disk instability, and bulge formation. Intense, relatively smooth streams ma...

We report the discovery of two hibonite grains (CaAl12O19) whose isotopic compositions show that they formed in the winds of red giant and asymptotic giant branch (AGB) stars. While hibonite is the second major phase (after corundum, Al2O3) expected to condense from stellar ejecta with , it has not previously been found. C/O ! 1 One circumstellar hibonite grain is highly enriched in O and sligh...

On the basis of recent observational evidence and new theoretical results, we construct a speculative scenario for the evolution of Wolf-Rayet central stars of planetary nebula. Although single star evolutionary calculations have recently succeeded in reproducing the composition of these objects, it is clear from the latest infra-red observations that a new perspective has to be adopted: the si...

The Milky Way has a giant stellar structure in the solar neighborhood, which has a size of ∼ 1 kpc, a mass of ∼ 106M⊙, and a ring-like distribution of young stars. Fundamental physical properties of this local enigmatic structure, known as the Gould belt (GB), have not been reproduced by previously proposed models. We first show that the local enigmatic structure can be formed about 30 Myr ago ...

Giant planets on short-period orbits are predicted to be inflated and eventually engulfed by their host stars. However, the detailed timescales stages of these processes not well known. Here we present discovery three hot Jupiters (P $<$ 10 d) orbiting evolved, intermediate-mass stars ($M_\star$ $\approx$ 1.5 M$_\odot$, 2 R$_\odot$ $R_\star < $ 5 R$_\odot$). By combining \tess photometry with g...

We present one possible mechanism for the giant flares of the Soft GammaRay Repeaters (SGRs) within the framework of magnetar, i.e., superstrongly magnetized neutron star model, motivated by the positive period increase associated with the August 27 event from SGR 1900+14. We assume that the global reconfiguration of the internal magnetic field suddenly occurs. Then, the shape of the star is de...

Among the 160 known exoplanets, mainly detected in large radial-velocity surveys, only 8 have a characterization of their actual mass and radius thanks to the two complementary methods of detection: radial velocities and photometric transit. We started in March 2004 an exoplanet-search programme biased toward high-metallicity stars which are more frequently host extra-solar planets. This survey...