NewAthena is the second L-class mission of the European Space Agency's Cosmic Vision program, with a scheduled launch for 2037. This mission will focus on observing the so-called hot and energetic universe using X-rays (Nandra et al. 2013). Scientific studies conducted with NewAthena observations will enhance our understanding of how large matter halos (galaxy groups and clusters) have formed, particularly the dynamics of inter-cluster plasma, and how active galactic nuclei influence this process. Another significant aspect will be gaining a better understanding of the formation of supermassive black holes at the centers of galaxies and the physics of accretion and ejection associated with their activity. NewAthena will also provide precise X-ray spectra of solar system planets, observe massive stars and their stellar winds, and accurately characterize Type Ia Supernovae.

The X-IFU instrument will be one of the two instruments aboard Athena (Peille et al. 2024). It will be a cryogenic X-ray imaging spectrometer, achieving unprecedented spectral resolution for this type of observation, with a target resolution of 4 eV at 7 keV. This will be accomplished through an array of over 1,000 Transition Edge Sensors (TES) microcalorimeters cooled to 55 mK, covering approximately 12 arcmin² of the sky. These goals can only be met by performing a precise and comprehensive calibration of the instrument, which will be the responsibility of IRAP and the central focus of the thesis work.

The thesis will revolve around three main axes:

1 - Detection chain validation and ground calibration preparation: These activities will involve a cryogenic test bench designed at IRAP used with X-ray sources. The bench is optimized to integrate flight electronics prototypes and demonstrate the complete detection chain of the instrument. An essential goal of the calibration is to calibrate the energy response of the microcalorimeters with a precision better than 0.4 eV up to 7 keV, allowing the study of gas dynamics in galaxy clusters, particularly kinematics and turbulence. Conventional calibration sources, such as fluorescent sources, present challenges due to the difficulty of modeling the emitted spectral line complexes, leading to uncertainties that exceed calibration requirements. To obtain precise energy references, an Electron Beam Ion Trap (EBIT) will be used. This device generates a plasma of highly ionized atoms with known X-ray emission lines, accurate to a few meV, providing an ideal calibration source. These instrumental activities, central to this thesis work, will allow a thorough and precise calibration of the instrument, managed by IRAP.  

2 - In-Flight Calibration Preparation: Efforts will be made to prepare for in-flight calibration based on astrophysical sources. The ultimate performance of the instrument will only be realized by comparing the ground calibration (notably from the aforementioned EBIT measurements) with that obtained in space. The absence of complex X-ray sources on board necessitates the use of sky sources, whose characteristics are known to varying degrees. Therefore, it will be necessary to identify suitable standard candles in advance, simulate them, and validate the calibration methods based on the theoretical response of the instrument. This will rely on a simulated calibration database incorporating uncertainties regarding both the observed source and the instrument itself. The aim is to determine the achievable precision and the time required to optimally prepare the in-flight calibration plan.

3 - Contribution to Data Analysis: A contribution will be made to the analysis and interpretation of observations focused on the astrophysical aspects related to the X-IFU objectives and the preparation of observations with the instrument. Based on data from the Resolve instrument aboard the Japanese XRISM satellite, a precursor to the X-IFU, this work will concentrate on studying galaxy clusters (Ettori et al. 2013, Pointecouteau et al. 2013). These extended sources require the full capabilities of integral field spectrometers like Resolve and X-IFU to reconstruct the physical properties of hot intra-cluster plasma (e.g., density, temperature, chemical abundances, turbulent velocities, etc.). These analyses will require adapting existing tools or developing new ones tailored to the hyperspectral nature of X-IFU data. The objective will be to provide new constraints that will enhance our understanding of the dynamic assembly of the largest matter halos in the universe.

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For more Information about the topics and the co-financial partner (found by the lab !); 

contact Directeur de thèse - etienne.pointecouteau@irap.omp.eu

Then, prepare a resume, a recent transcript and a reference letter from your M2 supervisor/ engineering school director and you will be ready to apply online  before March 14th, 2025 Midnight Paris time !