Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction of groups compares to that of clusters. In the following sections, the author describes the mechanics of X-ray astronomy, the group environment, and the characteristics of active galactic nuclei. The author briefly describes the possible mechanisms for AGN fueling.

We obtained four pointings of over 100 ks each of the well-studied Wolf-Rayet star WR 6 with the XMM-Newton satellite. With a first paper emphasizing the results of spectral analysis, this follow-up highlights the X-ray variability clearly detected in all four pointings. However, phased light curves fail to confirm obvious cyclic behavior on the well-established 3.766 d period widely found at longer wavelengths. The data are of such quality that we were able to conduct a search for "event clustering" in the arrival times of X-ray photons. However, we fail to detect any such clustering. One possibility is that X-rays are generated in a stationary shock structure. In this context we favor a co-rotating interaction region (CIR) and present a phenomenological model for X-rays from a CIR structure. We show that a CIR has the potential to account simultaneously for the X-ray variability and constraints provided by the spectral analysis. Ultimately, the viability of the CIR model will require both intermittent long-term X-ray monitoring of WR 6 and better physical models of CIR X-ray production at large radii in stellar winds.

Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction of groups compares to that of clusters. In the following sections, the author describes the mechanics of X-ray astronomy, the group environment, and the characteristics of active galactic nuclei. The author briefly describes the possible mechanisms for AGN fueling.

Using the Chandra X-ray Observatory, Martini et al. (2006) found that the AGN fraction of galaxy clusters was five times higher than previous optical studies suggested. Using visual observations only, Dressler et al. (1985) estimated the AGN fraction of field galaxies to be 5%, while that of clusters was thought to be 1%. To understand the role that the environment plays in AGN fueling, the author studied a variety of environments, ranging from the field to groups to clusters. Will the AGN fraction of groups also be higher than that of the field? The author demonstrates how the AGN fraction of groups compares to that of clusters. In the following sections, the author describes the mechanics of X-ray astronomy, the group environment, and the characteristics of active galactic nuclei. The author briefly describes the possible mechanisms for AGN fueling.

Ultraluminous X-ray sources (ULXs) are extragalactic, non-nuclear, point-like X-ray sources whose luminosity supersedes that of the Eddington limit of an accreting stellar mass black hole (L&gt; 10 ^ 39 erg / s). Most of them are powered by black holes and neutron stars undergoing genuine super-Eddington accretion, with a small handful of candidates being consistent with sub-Eddington accretion on an intermediate mass black hole. In this thesis, we explore the populations of ULXs in the sky surveys of ESA's X-ray satellite, XMM-Newton, and the MPE's newly launched X-ray telescope, eROSITA. We do so by correlating them with the HECATE list of galaxiesto build two X-ray non-nuclear catalogs, and comparing the yields with very expensive surveys and previous works. To build a catalog, we useother reference lists of contaminant objects, such as the Gaia data releases, the SIMBAD database or the SDSS survey to look for contaminating objects of diverse nature, such as foreground stars or background quasars, in order to make sure that our resulting ULX samples are as clean as possiblewith catalog data only. Our results include the attestation that the XMM-Newton ninth data release provides an improvement in quantity and quality with respect to older data releases used in previous works, and that the eROSITA survey is currently in a very preliminary stage. The two new catalogs contain 12,952 and 3,720 non-nuclear X-ray sources, out of which 914 and 132 are ULX candidates with an expected ~ 25% fraction of undetected contaminants. This constitutes a very significant contribution to the already known 300 ULX candidates. Since the sky coverage and depth of the XMM-Newton and eROSITA surveys are vastly different, only 19 of the ULX candidates are shared between the catalogs. ULX candidates are preferentially found in star-forming galaxies, but a subset of very bright objects (L&gt; 5x10 ^ 40 erg / s) try to be more common in elliptical galaxies, in contradiction to what has been established in the literature. / <p>This thesis was written under the joint supervision of Erin O'Sullivan at Uppsala University and Axel Schwope at the Leibniz Institute for Astrophysics in Potsdam. The presentation was held online due to the COVID-19 circumstances.</p> / Master Thesis

We obtained X-ray XMM-Newton observations of the open cluster Berkeley 87 and the massive star-forming region (SFR) ON 2. In addition, archival infrared Spitzer Space Telescope observations were used to study the morphology of ON 2, to uncover young stellar objects, and to investigate their relationship with the X-ray sources. It is likely that the SFR ON 2 and Berkeley 87 are at the same distance, 1.23 kpc, and hence are associated. The XMM-Newton observations detected X-rays from massive stars in Berkeley 87 as well as diffuse emission from the SFR ON 2. The two patches of diffuse X-ray emission are encompassed in the shell-like H II region GAL 75.84+0.40 in the northern part of ON 2 and in the ON 2S region in the southern part of ON 2. The diffuse emission from GAL 75.84+0.40 suffers an absorption column equivalent to AV ≈ 28 mag. Its spectrum can be fitted either with a thermal plasma model at T ≳ 30 MK or by an absorbed power-law model with γ ≈ −2.6. The X-ray luminosity of GAL 75.84+0.40 is LX ≈ 6 × 1031 erg s−1. The diffuse emission from ON 2S is adjacent to the ultra-compact H II (UCH II) region Cygnus 2N, but does not coincide with it or with any other known UCH II region. It has a luminosity of LX ≈ 4 × 1031 erg s−1. The spectrum can be fitted with an absorbed power-law model with γ ≈ −1.4. We adopt the view of Turner & Forbes that the SFR ON 2 is physically associated with the massive star cluster Berkeley 87 hosting the WO-type star WR 142. We discuss different explanations for the apparently diffuse X-ray emission in these SFRs. These include synchrotron radiation, invoked by the co-existence of strongly shocked stellar winds and turbulent magnetic fields in the star-forming complex, cluster wind emission, or an unresolved population of discrete sources.

Les observations XMM-Newton et Chandra en X de trois amas globulaires galactiques (NGC 2808, NGC 4372 et M 22) sont présentées et analysées. Elles sont complétées par des observations dans le visible, l'ultraviolet, l'infrarouge et le domaine radio afin d'identifier les sources X liées à ces amas globulaires. Les observations X ont permis de détecter 16 sources liées à NGC 2808 et 18 sources liées à M 22 qui sont principalement des binaires serrées. Cette population élevée de binaires aurait un rôle important à jouer dans le ralentissement de l'effondrement du cœur de ces amas globulaires. Une binaire X de faible masse en quiescence contenant une étoile à neutrons a été détectée dans NGC 2808 et aucune source de ce type n'est détectée dans M 22 et NGC 4372. Ces résultats sont en accord avec la corrélation déjà observée entre le nombre de ces objets et le taux de rencontre d'étoiles dans le cœur des amas globulaires. Un déficit possible de sources X dans NGC 2808 semble indiquer que le taux de rencontre n'est pas le seul paramètre intervenant dans la production des sources X et la métallicité de l'amas pourrait aussi avoir une influence. À partir des rapports X/UV et d'observations spectroscopiques, nous proposons différentes approches afin de résoudre le problème du déficit d'éruptions de variables cataclysmiques déjà observé dans les amas globulaires. Ces approches consistent à déterminer si les variables cataclysmiques des amas globulaires sont en majorité magnétiques ou si elles ont un taux d'accrétion faible. Enfin, les observations permettent d'apporter une limite supérieure d'environ 400 masses solaires si un trou noir de masse intermédiaire se trouvait dans NGC 2808.

In this thesis, we present the spectral and timing variabilities of anomalous X-ray pulsar 1E 2259+586 observed with European Photon Imaging PN Camera (EPIC PN) on board X-ray Multi Mirror Mission (XMM), Proportional Counter Array (PCA) on board Rossi X-ray Timing Explorer (RXTE) and Advanced CCD Imaging Spectrometer (ACIS) on board Chandra X-ray Observatory. We presented the results of spectral analysis of 2000 January 11 ACIS observation. Pulse phase spectroscopy was performed on two XMM observations before and after the outburst. Pulse profiles of two XMM observations before the outburst and three XMM observations after the outburst were studied. Results are consistent with the those presented by Patel et al. (2001) and Woods et al. (2004). We searched for the spectral variations versus spin rate during the outburst. Long-term spectral, frequency and spin-down rate variations are presented between 1996 and 2006 including 98 RXTE and 4 XMM observations. However, except outburst region (Woods et al. 2004) no significant spectral and spin rate variabilities were seen. Around the outburst region we confirmed the spectral hardening with increasing spin rate and flux.

Le satellite XMM-Newton est la seconde grande mission du plan Horizon 2000 de l'Agence Spatiale Européenne, et a pour but d'ouvrir plus largement la fenêtre des rayons-X afin d'explorer la population de sources de hautes énergies tant de la Galaxie que du ciel profond.<br /><br />Dans la première partie, je dresse un portrait de l'astronomie contemporaine dans les hautes énergies, puis je résume le contexte, notamment celui de l'observation des grandes structures et des Amas de Galaxies, ayant mené au développement d'un observatoire spatial tel qu'XMM-Newton. Une description de ses télescopes, aussi détaillée que nécessaire compte-tenu des études présentées par la suite, est faite dans la seconde partie.<br /><br />Je décris dans la troisième partie comment se sont déroulées les campagnes d'étalonnage au sol des instruments EPIC sur le banc de test synchrotron d'Orsay, ainsi que ma contribution à l'analyse des données subséquentes.<br /><br />Dans une quatrième partie, je confronte des résultats d'étalonnage à des données de vol, fais le bilan des méthodes d'analyse de ces données et présente une application de ces méthodes à l'observation d'Amas de Galaxies.<br /><br />Je conclus enfin quant aux perspectives en matière d'observations de sources étendues avec XMM-Newton ainsi qu'en matière d'instrumentation pour les hautes énergies en général et de techniques de traitement de données massives dont les Observatoires Virtuels pourront être demandeurs.

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