arXiv subjects

J. -B. Lebouquin

Publications and source records attributed to J. -B. Lebouquin.

4 recordsLinked to original sources

arXiv2026

Unlocking the dynamics of Young Stellar Objects: Time-Domain Interferometry with six 4-m class telescopes

The dynamics of the inner regions of young stellar objects (YSOs) is driven by a variety of physical phenomena, from magnetospheres and accretion to the dust sublimation rim and inner disk flows. These inner environments evolve on timescales of hours to days, exactly when bursts, dips, and rapid structural changes carry the most valuable information about star and planet formations, but remain hardly reachable with current facilities. A better reactive infrastructure with six or more telescopes, combined with alerts from large time-domain surveys (e.g., at the era of LSST/Rubin type facilities), and equipped with instruments spanning from the V-band to the thermal infrared (N), would provide the instantaneous uv-coverage and spectral diagnostics needed to unambiguously interpret and image these events as they happen. Such a world's first time-domain interferometric observatory would enable qualitatively new science: directly linking optical and infrared variability to spatially resolved changes in magnetospheric accretion, inner-disk geometry, and dust and gas dynamics in the innermost astronomical unit. Crucially, connecting these processes to outer-scale unresolved information from JWST, ALMA, and the ELT would yield a complete tomography of the planet-forming region.

astro-ph.IM↗

arXiv2011

A PIONIER and incisive look at the interacting binary SS Lep

Symbiotic stars are eccellent laboratories to study a broad range of poorly understood physical processes, such as mass loss of red giants, accretion onto compact objects, and evolution of nova-like outbursts. As their evolution is strongly influenced by the mass transfer episodes, understanding the history of these systems requires foremost to determine which process is at play: Roche lobe overflow, stellar wind accretion, or some more complex mixture of both. We report here an interferometric study of the symbiotic system SS Leporis, performed with the unique PIONIER instrument. By determining the binary orbit and revisiting the parameters of the two stars, we show that the giant does not fill its Roche lobe, and that the mass transfer most likely occurs via the accretion of an important part of the giant's wind.

astro-ph.SR↗

arXiv2011

Optimized fringe sensors for the VLTI next generation instruments

Context. With the arrival of the next generation of ground-based imaging interferometers combining from 4 to possibly 6 telescopes simultaneously, there is also a strong need for a new generation of fringe trackers able to cophase such arrays. These instruments have to be very sensitive and to provide robust operations in quickly varying observational conditions. Aims. We aim at defining the optimal characteristics of fringe sensor concepts operating with 4 or 6 telescopes. The current detector limitations impose us to consider solutions based on co-axial pairwise combination schemes. Methods. We independently study several aspects of the fringe sensing process: 1) how to measure the phase and the group delay, and 2) how to combine the telescopes in order to ensure a precise and robust fringe tracking in real conditions. Thanks to analytical developments and numerical simulations, we define the optimal fringe-sensor concepts and compute the expected performance of the 4-telescope one with our dedicated end-to-end simulation tool sim2GFT. Results. We first show that measuring the phase and the group delay by obtaining the data in several steps (i.e. by temporally modulating the optical path difference) is extremely sensitive to atmospheric turbulence and therefore conclude that it is better to obtain the fringe position with a set of data obtained simultaneously. Subsequently, we show that among all co-axial pairwise schemes, moderately redundant concepts increase the sensitivity as well as the robustness in various atmospheric or observing conditions. Merging all these results, end-to-end simulations show that our 4-telescope fringe sensor concept is able to track fringes at least 90% of the time up to limiting magnitudes of 7.5 and 9.5 for the 1.8- and 8.2-meter VLTI telescopes respectively.

astro-ph.IM↗

arXiv2010

PIONIER: a visitor instrument for the VLTI

PIONIER is a 4-telescope visitor instrument for the VLTI, planned to see its first fringes in 2010. It combines four ATs or four UTs using a pairwise ABCD integrated optics combiner that can also be used in scanning mode. It provides low spectral resolution in H and K band. PIONIER is designed for imaging with a specific emphasis on fast fringe recording to allow closure-phases and visibilities to be precisely measured. In this work we provide the detailed description of the instrument and present its updated status.

astro-ph.IM↗