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Sismologie des étoiles Be avec le satellite CoRoT

Abstract : Be stars represent about 20 % of the B-type stars in our Galaxy. These stars are surrounded by a circumstellar envelope fed by discrete and recurrent material ejections that come from the star. These stars are also pulsating and rapidly rotating stars. That is why Be stars have specifics pulsational features, that can be studied by the CoRoT satellite, successfully launched on the 27th December 2006. For the first time, CoRoT allows us to systematically study the link between pulsations of Be stars and material outflows that give rise to the circumstellar disk.The purpose of my PhD thesis work is to analyse the CoRoT data of Be stars observed in the first observations runs. Firstly, the data processing required improvements of the frequency searching methods in order to analyse a huge volume of data with high accuracy. Therefore, I developed a data processing tool, called TiSAFT (Time Series Analysis with Fisher's Test of significance), that extracts the frequencies embedded in the CoRoT photometric data. TiSAFT uses a statistical criterium to determine the significance of the results. Secondly, I analysed the photometric data of the Be star HD49330 observed with the CoRoT during 137 days and with ground-based spectroscopy during a total period of 20 nights. HD49330 showed a luminosity burst during the observations that we associated to a material ejection. The amplitudes of the signal associated with the main frequencies HD49330 change all along the light burst and are clearly correlated with the burst. Moreover, concerning the caracteristics of the pulsation modes. HD49330 is an "hybrid" star : we found p modes typical of β Cephei stars and g modes typical stars.
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Submitted on : Tuesday, December 18, 2018 - 10:12:09 AM
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Anne-Laure Huat. Sismologie des étoiles Be avec le satellite CoRoT. Astrophysique stellaire et solaire [astro-ph.SR]. Observatoire de Paris, 2009. Français. ⟨tel-01958554⟩



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