KERVELLA , Pierre

Context: The nearby pair of solar-type stars Alpha Centauri is a favorable target for an imaging search for extrasolar planets. Indications exist that the gravitational mass of Alpha Cen B could be higher than its modeled mass, the difference being consistent with a substellar companion of a few tens of Jupiter masses. However, Alpha Centauri...

Proxima and α Centauri AB have almost identical distances and proper motions with respect to the Sun. Although the probability of such similar parameters is, in principle, very low, the question as to whether they actually form a single gravitationally bound triple system has been open since the discovery of Proxima one century ago. Owing to...

- Context: The triple stellar system delta Vel system presents a significant infrared excess, whose origin is still being debated. A large infrared bow shock has been discovered using Spitzer/MIPS observations. Although it appears as a significant contributor to the measured IR excess, the possibility exists that a circumstellar IR excess is...

The rapid proper motion of the α Cen pair (≈ 3.7 arcsec yr −1) and its location close to the galactic plane on a rich stellar background combine constructively to make them excellent candidates for close stellar conjunctions with more distant stars. Adding new differential astrometry to archival data, we have refined the orbital parameters,...

The photospheric radius is one of the fundamental parameters governing the radiative equilibrium of a star. We report new observations of the nearest solar-type stars α Centauri A (G2V) and B (K1V) with the VLTI/PIONIER optical interferometer. The combination of four configurations of the VLTI enable us to measure simultaneously the limb...

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 nearest Be star, and we recently detected a CSE using near-IR interferometry. Aims: Our initial goal was to...

Be stars show evidence of mass loss and circumstellar envelopes (CSE), from UV resonance lines, near-IR excesses and the presence of episodic hydrogen emission lines. The geometry of these envelopes is still uncertain, though it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. We probe the close...

Context. The census of stellar and substellar companions of nearby stars is largely incomplete, in particular toward the low-mass brown dwarf and long-period exoplanets. It is, however, fundamentally important in the understanding of the stellar and planetary formation and evolution mechanisms. Nearby stars are particularly favorable targets...

Be stars show evidence of mass loss and circumstellar envelopes (CSE), from UV resonance lines, near-IR excesses and the presence of episodic hydrogen emission lines. The geometry of these envelopes is still uncertain, though it is often assumed that they are formed by a disk around the stellar equator and a hot polar wind. We probe the close...