Accretion Disk Weather of Black Hole X-Ray Binaries - The Case of Cygnus X-1

Die Röntgenemission, die bei der Akkretion von Materie auf ein Schwarzes Loch entsteht, bietet die Möglichkeit, den Einfluss dieser Objekte auf ihre Umgebung zu untersuchen. Der Schwerpunkt dieser Arbeit liegt auf stellaren Schwarzen Löchern in Röntgendoppelsternsystemen (BHXRBs). Eine systematische Untersuchung ihrer Röntgenvariabilität und die sich daraus ergebenden Einschränkungen für aktuelle Akkretionsmodelle werden vorgestellt. Die Einleitung beschreibt die historische Entdeckung von BHXREBs, stellt die Objektklassen vor, und gibt einen Überblick über die bekannten Quellen und die Cyg X-1 Beobachtungskampagne. Kap. 2 fasst die Eigenschaften der verschiedenen BHXRB Emissionszustände sowie der assoziierten physikalischen Modelle zusammen. In Kap. 3 werden die verwendeten Zeitreihenanalysemethoden - hauptsächlich Fourier Statistiken höherer Ordnung - beschrieben und durch Beispiele illustriert. Die anschliessenden Kapitel sind der Analyse des Cyg X-1 Monitorings (1996-2001) gewidmet: Kap. 4 beschäftigt sich mit der zeitlichen Entwicklung der Zeitverzögerungen zwischen verschiedenen Energiebändern, deren Untersuchung u.a. zur Definition der 'fehlgeschlagenen' Zustandsänderungen geführt hat. Kapitel 5 konzentriert sich auf die Modellierung der Variabilitätsspektren mit Lorentzfunktionen, wobei zum ersten Mal gezeigt werden konnnte, dass dies für alle Cyg X-1 'Hard State' Beobachtungen konsistent möglich ist. Das abschliessende Kapitel diskutiert die Ergebnisse u.a. vor dem Hintergrund neuerer Röntgendoppelsternstudien. Sowohl die Untersuchung der Zeitverzögerungen wie auch die Modellierung der Variabilitätsspektren weisen auf eine vertikale Vergrösserung der Akkretionsregion während Zustandsänederungen hin. Dies unterstützt kürzlich entwickelte Jet-Disk Modelle, in denen ein Anteil des Materials in der Akkretionsregion nicht vom Schwarzen Loch 'verschluckt' wird, sondern dessen Umgebung in Form eines 'Outflows' wieder verlässt.The X-ray emission produced by accretion of matter onto a black hole gives us the unique opportunity to study the influence of these fascinating objects on their surroundings. This thesis focuses on stellar mass black holes in X-ray binary systems (BHXRBs) and presents a systematic study of their variability and its implication for current accretion models. To this end regular multiwavelength observations of Cyg X-1 were performed, especially with the Rossi X-Ray Timing Explorer. The introductory chapter describes the historical discovery of BHXRBs, introduces the different object classes, and gives an overview of known sources and of the observing campaign for Cyg X-1. The following chapter summarizes the observational properties of the different emission states of BHXRBs and the corresponding physical models. In chapter 3 the applied time series analysis methods - mainly recently developed higher order Fourier statistics - are described, illustrated by examples (up to ~100 Hz). Chapters 4 and 5 present the results of analyzing the Cyg X-1 monitoring from 1996 to 2001. The main objective of chapter 4 is to study the temporal evolution of the time lags between different energy bands, leading, e.g., to the definition of 'failed' state transitions. Chapter 5 concentrates on modeling the power spectra with discrete Lorentzians, showing for the first time that this is possible for all Cyg X-1 hard state observations in a consistent way. The final chapter discusses the results in the light of recent X-ray binary studies. A physical accretion scenario is proposed: both approaches - studying the lags as well as modeling the power spectra - indicate a vertical expansion of the accretion region during state transitions. Thus recent jet-disk models are strongly supported where a fraction of the material in the accretion region is not 'swallowed' by the black hole but leaves its neighborhood again in form of an outflow

State transitions and jet formation in black hole binaries

The daily monitoring observations of black hole transients with RXTE provided important clues on the conditions of the state transitions, both in terms of spectra and timing. The recent addition of monitoring in the optical-infrared and the radio band significantly extended our knowledge of the relation between the jets and the spectral states. However, there are still very important unanswered questions, most importantly, whether the formation of the jet triggers any change in the spectral and temporal properties of the source. The answer to this question is also intrinsically related to the origin of the hard X-ray emission. In this work, the relation between the jet and the state transitions is discussed, using the data from GX 339-4, 4U 1543-47, H 1743-322, and GRO J1655-40, concentrating on the evolution of spectral and temporal parameters before, during and after the formation of the jet

Broadband Suzaku observations of IGR J16207-5129

An analysis of IGR J16207-5129 is presented based on observations taken with Suzaku. The data set represents ~80 ks of effective exposure time in a broad energy range between 0.5 and 60 keV, including unprecedented spectral sensitivity above 15 keV. The average source spectrum is well described by an absorbed power law in which we measured a large intrinsic absorption of nH = 16.2(-1.1/+0.9)x10^22 /cm2. This confirms that IGR J16207-5129 belongs to the class of absorbed HMXBs. We were able to constrain the cutoff energy at 19(-4/+8) keV which argues in favor of a neutron star as the primary. Our observation includes an epoch in which the source count rate is compatible with no flux suggesting a possible eclipse. We discuss the nature of this source in light of these and of other recent results.Comment: 12 pages, 6 figures, accepted for publication in Ap

Temporal Variations of Strength and Location of the South Atlantic Anomaly as Measured by RXTE

The evolution of the particle background at an altitude of ~540 km during the time interval between 1996 and 2007 is studied using the particle monitor of the High Energy X-ray Timing Experiment on board NASA's Rossi X-ray Timing Explorer. A special emphasis of this study is the location and strength of the South Atlantic Anomaly (SAA). The size and strength of the SAA are anti-correlated with the the 10.7 cm radio flux of the Sun, which leads the SAA strength by ~1 year reflecting variations in solar heating of the upper atmosphere. The location of the SAA is also found to drift westwards with an average drift rate of about 0.3 deg/yr following the drift of the geomagnetic field configuration. Superimposed to this drift rate are irregularities, where the SAA suddenly moves eastwards and where furthermore the speed of the drift changes. The most prominent of these irregularities is found in the second quarter of 2003 and another event took place in 1999. We suggest that these events are previously unrecognized manifestations of the geomagnetic jerks of the Earth's magnetic field.Comment: 21 pages, 11 figures, accepted for publication in Earth and Planetary Science Letter

A Clumpy Stellar Wind and Luminosity-Dependent Cyclotron Line Revealed by The First Suzaku Observation of the High-Mass X-ray Binary 4U 1538-522

We present results from the first Suzaku observation of the high-mass X-ray binary 4U 1538-522. The broad-band spectral coverage of Suzaku allows for a detailed spectral analysis, characterizing the cyclotron resonance scattering feature at $23.0 \pm 0.4$ keV and the iron K$\alpha$ line at $6.426 \pm 0.008$ keV, as well as placing limits on the strengths of the iron K$\beta$ line and the iron K edge. We track the evolution of the spectral parameters both in time and in luminosity, notably finding a significant positive correlation between cyclotron line energy and luminosity. A dip and spike in the lightcurve is shown to be associated with an order-of-magnitude increase in column density along the line of sight, as well as significant variation in the underlying continuum, implying the accretion of a overdense region of a clumpy stellar wind. We also present a phase-resolved analysis, with most spectral parameters of interest showing significant variation with phase. Notably, both the cyclotron line energy and the iron K$\alpha$ line intensity vary significantly with phase, with the iron line intensity significantly out-of-phase with the pulse profile. We discuss the implications of these findings in the context of recent work in the areas of accretion column physics and cyclotron resonance scattering feature formation.Comment: 15 pages, 8 figures. Accepted to ApJ on 2 July 201

Spectroscopy of the stellar wind in the Cygnus X-1 system

The X-ray luminosity of black holes is produced through the accretion of material from their companion stars. Depending on the mass of the donor star, accretion of the material falling onto the black hole through the inner Lagrange point of the system or accretion by the strong stellar wind can occur. Cygnus X-1 is a high mass X-ray binary system, where the black hole is powered by accretion of the stellar wind of its supergiant companion star HDE226868. As the companion is close to filling its Roche lobe, the wind is not symmetric, but strongly focused towards the black hole. Chandra-HETGS observations allow for an investigation of this focused stellar wind, which is essential to understand the physics of the accretion flow. We compare observations at the distinct orbital phases of 0.0, 0.2, 0.5 and 0.75. These correspond to different lines of sights towards the source, allowing us to probe the structure and the dynamics of the wind.Comment: conference proceeding from Integral/Bart Workshop Karlsbad, CZ, 14.4-18.4 201