| Přispěvatelé: |
Institut de recherche en astrophysique et planétologie (IRAP), Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Observatoire Midi-Pyrénées (OMP), Institut de Recherche pour le Développement (IRD)-Université Toulouse III - Paul Sabatier (UT3), Université de Toulouse (UT)-Université de Toulouse (UT)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Institut de Recherche pour le Développement (IRD)-Institut national des sciences de l'Univers (INSU - CNRS)-Centre National d'Études Spatiales [Toulouse] (CNES)-Centre National de la Recherche Scientifique (CNRS)-Météo-France -Centre National de la Recherche Scientifique (CNRS), Université Paul Sabatier - Toulouse III, Jean Luc Atteia |
| Popis: |
Gamma-Ray Bursts (GRBs) are extra-galactic transient phenomena that continue to puzzle scientists, 50 years after their discovery. Associated to violent events like the death of massive stars, they consist of two phases: the prompt emission, a burst of gamma-ray photons lasting typically few seconds and the afterglow, detectable in X-ray, visible and radio wavelengths up to few days after the prompt GRB. Being some of the most luminous phenomena in the Universe, GRBs are extremely interesting: they are among the farthest cosmic sources observed, representing a unique mean to probe stellar populations and the intra and inter-galactic medium at the highest redshifts. However, because of their short duration, their unpredictable times and sky localization, the study of GRBs remains challenging, even for modern astronomy. The Sino-French mission SVOM, to be launched end of 2023, encompasses two wide-field (ECLAIRs and GRM) and two narrow-field (MXT and VT) instruments for detecting, characterizing and localizing the GRB prompt and afterglow emissions. SVOM also benefits from three dedicated ground telescopes (GWAC, C-GFT and COLIBRI) and an antennae network, allowing to alert the scientific community within few minutes after the prompt emission detection for an optimal follow-up. My work focused on ECLAIRs, the wide-field hard X-ray telescope of SVOM. Using its coded mask and on-board computer, ECLAIRs will detect in near real-time the GRB prompt emission and get a crude localization from it. Thanks to its low energy threshold at 4 keV, the telescope will be perfectly suited for the detection of interesting GRB populations such as X-ray Flashes or high-redshift GRBs. My thesis has been focused on the evaluation of ECLAIRs performances in space: I have combined instrumental effects with models of the background sky emission and GRB/X-ray sources to accurately simulate the instrument data stream. These simulations have been used for example to evaluate the sensitivity of ECLAIRs to various types of transients, to calculate the GRB detection rate expected during the mission, and as a support to evaluate the science impact of various configuration parameters of the instrument. They have also been used as a framework for developing alternative trigger algorithm solutions to the on-board software, motivated by the unique ability of ECLAIRs to transfer all the events recorded on-board to the ground. Relying on simulated background orbits and GRBs, I have used a neural-network architecture suited for the anomaly detection on time series. This method may become part of an offline trigger able to detect transients missed by the on-board algorithm. Another application presented in the manuscript is the evaluation of ECLAIRs sensitivity to short high-energy (HE) transients coming from our local Universe (z |
