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Identification multi-longueurs d'onde des sources X faibles des amas globulaires

Abstract : I present a study of the faint X ray sources of three Galactic globular clusters (NGC 2808, NGC 4372 and M 22) in order to understand their dynamical evolution. XMM-Newton and Chandra observations are presented and analysed. They are strengthened by optical, ultraviolet, infrared and radio observations in order to identify the X-ray sources associated with these globular clusters. X-ray observations lead to the detection of 16 sources in NGC 2808 and 18 sources in M 22. These sources are mainly close binaries. This significant population of close binaries is likely to play an important role in slowing down the core collapse of these clusters. One quiescent neutron star low-mass X-ray binary was detected in NGC 2808, and there is no evidence for such an object in M 22 and NGC 4372. These results are in agreement with the relationship already observed showing that the number of these objects is correlated with the stellar encounter rate in the core of globular clusters. A possible lack of X-ray sources detected in NGC 2808 indicates that the encounter rate is not the only parameter to play a role in the formation of the X-ray sources, and the cluster metallicity could also play a role. Using X/UV ratios, and optical spectroscopic observations, we suggest different approaches to tackle the problem of the deficit of cataclysmic variable outbursts already observed in globular clusters, and try to determine whether it is because of moderate magnetic fields and low mass transfer, or increased white dwarf masses. The observations presented in this thesis allow us to derive a mass limit of several hundreds of solar masses, if an intermediate mass black hole is present in NGC 2808.
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Contributor : Williams Exbrayat <>
Submitted on : Tuesday, April 14, 2009 - 4:37:26 PM
Last modification on : Thursday, October 15, 2020 - 4:07:33 AM
Long-term archiving on: : Friday, October 12, 2012 - 4:35:36 PM


  • HAL Id : tel-00375366, version 1



Mathieu Servillat. Identification multi-longueurs d'onde des sources X faibles des amas globulaires. Planète et Univers [physics]. Université Paul Sabatier - Toulouse III, 2008. Français. ⟨tel-00375366⟩



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