A. Mérand
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View article: Interferometric Detection and Orbit Modeling of the Subcomponent in the Hot-dust System <i>κ</i> Tuc A: A Low-mass Star on an Eccentric Orbit in a Hierarchical-quintuple System
Interferometric Detection and Orbit Modeling of the Subcomponent in the Hot-dust System <i>κ</i> Tuc A: A Low-mass Star on an Eccentric Orbit in a Hierarchical-quintuple System Open
The system κ Tuc A is part of a hierarchical-quintuple system and is a prime target for studies of hot-exozodiacal dust, because a time-variable near-infrared excess has been detected. We observed the system with the Multi Aperture mid-Inf…
View article: Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B
Exomoon search with VLTI/GRAVITY around the substellar companion HD 206893 B Open
Direct astrometric detection of exomoons remains unexplored. This study presents the first application of high-precision astrometry to search for exomoons around substellar companions. We investigate whether the orbital motion of the compa…
View article: The mid-infrared spectrum of <i>β</i> Pictoris b
The mid-infrared spectrum of <i>β</i> Pictoris b Open
Few spectra of directly imaged exoplanets have been obtained in the mid-infrared (>3 μm). This region is particularly rich in molecular spectral signatures, whose measurements can help recover atmospheric parameters and provide a better un…
View article: Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-resolution Spectroscopy and VLTI/GRAVITY Astrometry <sup>*</sup>
Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-resolution Spectroscopy and VLTI/GRAVITY Astrometry <sup>*</sup> Open
Understanding the orbits of giant planets is critical for testing planet formation models, particularly at wide separations (>10 au) where traditional core accretion becomes inefficient. However, constraining orbits at these separations ha…
View article: The ExoGRAVITY survey: A K-band spectral library of giant exoplanet and brown dwarf companions
The ExoGRAVITY survey: A K-band spectral library of giant exoplanet and brown dwarf companions Open
Direct observations of exoplanet and brown dwarf companions with near-infrared interferometry, first enabled by the dual-field mode of VLTI/GRAVITY, provide unique measurements of the objects' orbital motions and atmospheric compositions. …
View article: V659 Cen: System Members Updated
V659 Cen: System Members Updated Open
V659 Cen is a classical Cepheid which is part of a multiple system. Previous observations have shown that a hot companion dominates an ultraviolet spectrum and a cooler main-sequence star dominates an XMM-Newton spectrum. The Hubble Space …
View article: Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-Resolution Spectroscopy and VLTI/GRAVITY Astrometry
Constraints on the Orbit of the Young Substellar Companion GQ Lup B from High-Resolution Spectroscopy and VLTI/GRAVITY Astrometry Open
Understanding the orbits of giant planets is critical for testing planet formation models, particularly at wide separations greater than 10 au where traditional core accretion becomes inefficient. However, constraining orbits at these sepa…
View article: Astrometric exomoon detection by means of optical interferometry
Astrometric exomoon detection by means of optical interferometry Open
Context: With no conclusive detection to date, the search for exomoons, satellites of planets orbiting other stars, remains a formidable challenge. Detecting these objects, compiling a population-level sample and constraining their occurre…
View article: V659 Cen: System Parameters Updated
V659 Cen: System Parameters Updated Open
V659 Cen is a classical Cepheid which is part of a multiple system. Previous observations have shown that a hot companion dominates an ultraviolet spectrum and a cooler main sequence star dominates an XMM-Newton spectrum. The Hubble Space …
View article: Spatially resolved broad line region in a quasar at z=4: Dynamical black hole mass and prominent outflow
Spatially resolved broad line region in a quasar at z=4: Dynamical black hole mass and prominent outflow Open
We present the first near-infrared interferometric data of a QSO at z=4. The K-band observations were performed with GRAVITY+ on the VLTI using all 4 UTs, detecting a differential phase signal that traces the spatially resolved kinematics …
View article: "Industrial-Scale" Black Hole Selection without a Satellite
"Industrial-Scale" Black Hole Selection without a Satellite Open
The forthcoming GRAVITY+ instrument promises to usher in an era of "industrial-scale" mass measurements of isolated black holes (BHs), with the potential to assemble a sample of many tens of BHs via interferometric microlensing over severa…
View article: An interferometric study of B star multiplicity
An interferometric study of B star multiplicity Open
Context. Massive stars can have extreme effects on their environments from local to galactic scales. Their multiplicity can affect this influence by altering how they evolve over time by causing dynamical interactions, common-envelope evol…
View article: Direct imaging discovery of a young giant planet orbiting on Solar System scales
Direct imaging discovery of a young giant planet orbiting on Solar System scales Open
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View article: Direct imaging discovery of a young giant planet orbiting on Solar System scales
Direct imaging discovery of a young giant planet orbiting on Solar System scales Open
HD 135344 AB is a young visual binary system that is best known for the protoplanetary disk around the secondary star. The circumstellar environment of the A0-type primary star, on the other hand, is already depleted. HD 135344 A is theref…
View article: Orbit and atmosphere of HIP 99770 b through the eyes of VLTI/GRAVITY
Orbit and atmosphere of HIP 99770 b through the eyes of VLTI/GRAVITY Open
Context . Inferring the likely formation channel of giant exoplanets and brown dwarf companions from orbital and atmospheric observables remains a formidable challenge. Further and more precise directly measured dynamical masses of these c…
View article: Mass of Cepheid V350 Sgr Incorporating Interferometry and the Companion Mass
Mass of Cepheid V350 Sgr Incorporating Interferometry and the Companion Mass Open
The system V350 Sgr has a classical Cepheid for the primary. Interferometry is presented for the system, and the full orbit is determined. The mass of the companion has been determined from an International Ultraviolet Explorer spectrum an…
View article: Mass of Cepheid V350 Sgr Incorporating Interferometry and the Companion Mass
Mass of Cepheid V350 Sgr Incorporating Interferometry and the Companion Mass Open
The system V350 Sgr has a classical Cepheid for the primary. Interferometry is presented for the system and the full orbit is determined. The mass of the companion has been determined from an {\it IUE} spectrum and comparison with the mass…
View article: Versatile light curve templates of Cepheids
Versatile light curve templates of Cepheids Open
Context. To use the period–luminosity relations of Cepheids to derive distances of extragalactic Cepheids, it is crucial to have reliable estimations of the luminosity of such stars. However, the light curves (LCs) of extragalactic Cepheid…
View article: Surface brightness–colour relations of Cepheids calibrated by optical interferometry
Surface brightness–colour relations of Cepheids calibrated by optical interferometry Open
Context . Surface brightness–colour relations (SBCRs) are widely used to determine the angular diameters of stars. They are in particular used in the Baade-Wesselink (BW) method of distance determination of Cepheids. However, the impact of…
View article: Insights from mid-infrared interferometric observations of the symbiotic nova RS Ophiuchi
Insights from mid-infrared interferometric observations of the symbiotic nova RS Ophiuchi Open
View article: On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb
On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb Open
The companion GL229B was recently resolved by Xuan et al. as a tight binary of two brown dwarfs (Ba and Bb) through VLTI-GRAVITY interferometry and Very Large Telescope-CRIRES+ radial velocity (RV) measurements. Here, we present Bayesian m…
View article: The highly magnetic Wolf-Rayet binary HD 45166 resolved with VLTI/GRAVITY
The highly magnetic Wolf-Rayet binary HD 45166 resolved with VLTI/GRAVITY Open
HD 45166 was recently reported to be a long-period binary comprising a B7 V star and a highly magnetic (⟨ B ⟩=43.0 ± 0.5 kG) hot Wolf-Rayet-like component, dubbed a quasi Wolf-Rayet (qWR) star in the literature. While originally proposed t…
View article: VLTI/GRAVITY upper limit on near-infrared emission from the nearby 33 <i>M</i><sub>⊙</sub> black hole Gaia BH3
VLTI/GRAVITY upper limit on near-infrared emission from the nearby 33 <i>M</i><sub>⊙</sub> black hole Gaia BH3 Open
Context. The recent astrometric discovery of the nearby (590 pc) massive (33 M ⊙ ) dormant black hole candidate Gaia BH3 offers the possibility to angularly resolve the black hole from its companion star by using optical interferometry. Ai…
View article: On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb
On the Orbit of the Binary Brown Dwarf Companion GL229 Ba and Bb Open
The companion GL229B was recently resolved by Xuan et al. (2024) as a tight binary of two brown dwarfs (Ba and Bb) through VLTI-GRAVITY interferometry and VLT-CRIRES+ RV measurements. Here, we present Bayesian models of the interferometric…
View article: Observations of Microlensed Images with Dual-field Interferometry: On-sky Demonstration and Prospects
Observations of Microlensed Images with Dual-field Interferometry: On-sky Demonstration and Prospects Open
Interferometric observations of gravitational microlensing events offer an opportunity for precise, efficient, and direct mass and distance measurements of lensing objects, especially those of isolated neutron stars and black holes. Howeve…
View article: Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE
Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE Open
Context. The circumstellar envelopes (CSE) of Cepheids are still only poorly characterized despite their potential impact on the distance determination via both the period-luminosity relation and the parallax-of-pulsation method. Aims. Thi…
View article: VLTI/GRAVITY enables the determination of the first dynamical masses of a classical Be + stripped and bloated pre-subdwarf binary
VLTI/GRAVITY enables the determination of the first dynamical masses of a classical Be + stripped and bloated pre-subdwarf binary Open
Context. HR 6819 is the first post-mass transfer binary system composed of a classical Be star and a bloated pre-subdwarf stripped star directly confirmed by interferometry. While the Be star is already spun up to near-critical rotation an…
View article: VLTI/GRAVITY enables the determination of the first dynamical masses of a classical Be + stripped and bloated pre-subdwarf binary
VLTI/GRAVITY enables the determination of the first dynamical masses of a classical Be + stripped and bloated pre-subdwarf binary Open
HR~6819 is the first post-mass transfer binary system composed of a classical Be star and a bloated pre-subdwarf stripped star directly confirmed by interferometry. While the Be star is already spun up to near-critical rotation and possess…
View article: Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE
Circumstellar emission of Cepheids across the instability strip: Mid-infrared observations with VLTI/MATISSE Open
The circumstellar envelopes (CSE) of Cepheids are still not well characterized despite their potential impact on distance determination via both the period-luminosity relation and the parallax-of-pulsation method. This paper aims to invest…
View article: Multiplicity of Galactic Cepheids from long-baseline interferometry
Multiplicity of Galactic Cepheids from long-baseline interferometry Open
Aims. We aim to accurately measure the dynamical mass and distance of Cepheids by combining radial velocity measurements with interferometric observations. Cepheid mass measurements are particularly necessary for solving the Cepheid mass d…