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...

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 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...

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...

We report the angular diameter measurement obtained with the VINCI/VLTI instrument on the nearby star Procyon A (alpha CMi A, F5IV-V), at a relative precision of ± 0.9%. We obtain a uniform disk angular diameter in the K band of thetaUD = 5.376±0.047 mas and a limb darkened value of thetaLD = 5.448±0.053 mas. Together with the HIPPARCOS...

Using VLTI/VINCI angular diameter measurements, we constrain the evolutionary status of three asteroseismic targets: the stars $\delta$ Eri, $\xi$ Hya, $\eta$ Boo. Our predictions of the mean large frequency spacing of these stars are in agreement with published observational estimations. Looking without success for a companion of $\delta$ Eri...

Context: The Be stars are massive dwarf or subgiant stars that present temporary emission lines in their spectrum, and particularly in the Halpha line. The mechanism triggering these Be episodes is currently unknown, but binarity could play an important role. Aims: Previous observations with the VLT/VISIR instrument (Kervella & Domiciano de...

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 Be stars are massive dwarf or subgiant stars that present temporary emission lines in their spectrum, and particularly in the Halpha line. The mechanism triggering these Be episodes is currently unknown, but binarity could play an important role. Aims: Previous observations with the VLT/VISIR instrument (Kervella & Domiciano de...

Context: Be stars are massive dwarf or subgiant stars that present temporary emission lines in their spectrum, and particularly in the Halpha line. The mechanism triggering these Be episodes is currently unknown, but binarity could play an important role. Aims: Previous observations with the VLT/VISIR instrument (Kervella & Domiciano de Souza...

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...

The availability of a number of new interferometric measurements of Main Sequence and subgiant stars makes it possible to calibrate the surface brightness relations of these stars using exclusively direct angular diameter measurements. These empirical laws make it possible to predict the limb darkened angular diameters thetaLD of dwarfs and...

Context: Alpha Centauri is our closest stellar neighbor, at a distance of only 1.3 pc, and its two main components have spectral types comparable to the Sun. This is therefore a favorable target for an imaging search for extrasolar planets. Moreover, indications exist that the gravitational mass of Alpha Cen B is higher than its modeled mass,...

Context: Alpha Centauri is our closest stellar neighbor, at a distance of only 1.3 pc, and its two main components have spectral types comparable to the Sun. This is therefore a favorable target for an imaging search for extrasolar planets. Moreover, indications exist that the gravitational mass of Alpha Cen B is higher than its modeled mass,...

Context: B[e] stars are expected to possess dusty circumstellar environments, which are responsible for a strong infrared (IR) excess. Aims: Using single-dish diffraction-limited imaging in the thermal infrared domain, we aim at measuring the angular extension of the dusty environment of the galactic B[e] MWC 300. Methods: We obtained...

Context. delta Vel contains the brightest eclipsing binary in the southern sky (delta Vel A), and a nearby third star located ~0.6" away (delta Vel B). The proximity of delta Vel B (usable as a reference) makes it a particularly well-suited target to detect the astrometric displacement of the center of light of the eclipsing pair. Aims. We...

We report in this paper the direct interferometric measurement of the angular diameter of five nearby Vega-like stars: alpha PsA, beta Leo, beta Pic, ε Eri and tau Cet. The near-infrared (K and H bands) observations were conducted at the VLTI during the commissioning period with the VINCI instrument and three different baselines ranging from 66...

Asteroseismology aims at constraining the stellar evolution theory, and allows to determine the age of stars together with other fundamental parameters. We present recent results obtained by interferometry, and prospects for the future.

International audience

Context: As is the case of several other Be stars, Achernar is surrounded by an envelope, recently detected by near-IR interferometry. Aims: We search for the signature of circumstellar emission at distances of a few stellar radii from Achernar, in the thermal IR domain. Methods: We obtained interferometric observations on three VLTI baselines...