Description du sujet de thèse

The PhD project focuses on the development and application of high-contrast interferometry for the characterization of exoplanets. High-contrast imaging systems such as GPI and SPHERE have enabled the discovery and study of massive giant planets, but their capabilities are limited to large orbital separations greater than 10 astronomical units. The VLTI instrument GRAVITY has paved the way for the direct observation of giant planets closer to their host star, allowing for the first simultaneous measurements of mass and luminosity. However, it remains restricted to the K band between 1.9 and 2.3 microns.

This project aims to design, at LIRA in collaboration with ESO, a high-contrast interferometric testbed in the J band, covering wavelengths between 1.1 and 1.3 microns. ESO, the European Southern Observatory (www.eso.org), is an intergovernmental organisation that designs, builds, and operates some of the most advanced astronomical observatories in the world, mainly located in Chile. It brings together multiple European member states and provides the international scientific community with cutting-edge facilities such as the Very Large Telescope (VLT) and the future Extremely Large Telescope (ELT).

The goal of the project is to enable the observation and detailed characterization of young giant planets such as Beta Pictoris c, to detect planets in reflected light in order to measure their albedo, and to improve the astrometric precision of the VLTI to search for possible exomoons. The instrumental development will include the capability to inject and recombine beams in integrated optics at short wavelengths, the precise control of polarization effects, and the implementation of J-band laser metrology to compensate for optical path errors.

The PhD work will involve both an astrophysical and an instrumental component. On the astrophysical side, the candidate will analyse existing datasets, particularly from the ExoGRAVITY and MATISSE programs, to study planetary atmospheres and orbits, publish the results, and present them at international conferences. This will also involve using and improving data reduction tools, especially in the context of the very small separation mode developed for GRAVITY+. On the instrumental side, the candidate will take part in assembling and aligning the optical testbed, in designing integrated optics chips in collaboration with Teem Photonics, and in implementing solutions to reduce contrast limitations caused by polarization effects and optical path variations.

In the long term, the success of this project will pave the way for multi-wavelength observations combining the J, K, and L bands to study young giants near the ice line, providing a better understanding of the giant planet population. The PhD candidate will benefit from a rich scientific environment at LIRA, known for its expertise in interferometric instrumentation and exoplanet studies, as well as from close international collaboration with ESO and opportunities for travel within Europe and to Chile.

Contexte de travail

LIRA, the direct successor of LESIA, has both a long-standing tradition in interferometry and instrumentation—reflected in its direct involvement in the GRAVITY+ project, as well as in the PLATO and ARIEL missions, the RPW instrument on Solar Orbiter, and MICADO for the ELT—and significant and growing expertise in exoplanets. It serves both as a centre of expertise in high-contrast observations, notably through the THD testbed, and as a central hub for GRAVITY+ and the ExoGRAVITY collaboration. The subject naturally finds its place at the interface between the “High Angular Resolution in Astronomy (HRAA)” group and the “Exoplanet Systems” group. The project will be conducted in close collaboration with ESO, and travel to Garching (near Munich, Germany) is to be expected.