Description du sujet de thèse

SOPHIE is the high-precision spectrograph installed at the 1.93m telescope at OHP since 2006. After major instrumental improvements, it daily delivers 1m/s accuracy on stellar RVs. The camera will be changed in 2026 for one with a larger and more efficient detector. This will lead to extend the wavelength coverage of the spectrograph to the far-red. However, getting the highest precision on this close near-infrared part of the spectra will present several challenges: contamination by telluric lines, closeness of the orders on the detectors, determining a new wavelength calibration procedures for the extension of the spectra.

On the scientific part, the extension of several orders of diffraction towards the near-infrared (650-800nm ) permits us to have more radial-velocity content(e.g. Artigau et al. 2018), hence a better accuracy especially for K and M dwarfs. It will improve the coverage of observations carried out jointly by SPIRou, mounted at the CFHT observing in the near-infrared and SOPHIE. The search and characterization of planet around M stars will be improved by the combination of the two instruments.

The K stars, less studied by the community until now, are very interesting because the effect of the stellar activity is seen to be lower than for G stars, their habitable zone is farther from the star than for M stars, and the probability of transit is higher than for G stars. Planets in the habitable zone of nearby K dwarfs are also of particular interest for the future major space missions like HWO (NASA) and LIFE (ESA) which will aim at searching for biomarkers on those planets, albeit they still need to be discovered. A new program focussed on these stars is set since one year.

The PhD candidate will have several objectives : develop a new wavelength calibration procedure, adapt line-by-line and template matching method to identify and remove instrumental systematics, telluric contamination correction,… The PhD will be also fully involved in different programs search for SOPHIE and associated to the SPIRou programs describe above.

Contexte de travail

This PhD subject is included in a collaborative project obtained through the French national agency (ANR) with IPAG at Grenoble and IRAP at Toulouse. The PhD project will be two years at OHP and the last year in larger institution (probably LAM or IPAG).

The PhD advisor, Isabelle BOISSE is part of the LAM and the GSP team and currently located at OHP. She is responsible or co-investigator of several SOPHIE programs and in strong collaboration with an European group of ~20 researchers (3 institutes in France, one in Geneva, Switzerland, one in Porto, Portugal, and one in Birmingham, UK). She is also strongly involved in the SPIRou programs and she is the French representative for the construction of the ANDES spectrograph for the ELT. The exoplanet group at LAM is also involved in several other projects: SPHERE, CHEOPS, TESS, Roman, PLATO, ARIEL and HARMONI.

Contraintes et risques

Travel for collaborations and promotion of scientific work.
Observations with SOPHIE, in particular, at least between 20 and 30 nights per year approximately.