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Comprehensive Analyses of Massive Binaries and Implications on Stellar Evolution

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Comprehensive Analyses of Massive Binaries and Implications on Stellar Evolution Institut für Physik und Astronomie Astrophysik I Comprehensive analyses of massive binaries and implications on stellar evolution Kumulative Dissertation zur Erlangung des akademischen Grades “doctor rerum naturalium” (Dr. rer. nat.) in der Wissenschaftsdisziplin Astrophysik eingereicht an der Mathematisch-Naturwissenschaftlichen Fakultät der Universität Potsdam von Tomer Shenar Potsdam, den 02. September 2016 Published online at the Institutional Repository of the University of Potsdam: URN urn:nbn:de:kobv:517-opus4-104857 http://nbn-resolving.de/urn:nbn:de:kobv:517-opus4-104857 Abstract (English / Deutsch) Via their powerful radiation, stellar winds, and supernova explosions, massive stars (Mini & 8 M ) bear a tremendous impact on galactic evolution. It became clear in recent decades that the majority of massive stars reside in binary systems. This thesis sets as a goal to quantify the impact of binarity (i.e., the presence of a companion star) on massive stars. For this purpose, massive binary systems in the Local Group, including OB-type binaries, high mass X-ray binaries (HMXBs), and Wolf-Rayet (WR) binaries, were investigated by means of spectral, orbital, and evolutionary analyses. The spectral analyses were performed with the non-local thermodynamic equillibrium (non-LTE) Pots- dam Wolf-Rayet (PoWR) model atmosphere code. Thanks to critical updates in the calculation of the hydrostatic layers, the code became a state-of-the-art tool applicable for all types of hot massive stars (Chapter 2). The eclipsing OB-type triple system δ Ori served as an intriguing test-case for the new version of the PoWR code, and provided key insights regarding the formation of X-rays in massive stars (Chapter 3). We further analyzed two prototypical HMXBs, Vela X-1 and IGR J17544-2619, and obtained fundamental conclusions regarding the dichotomy of two basic classes of HMXBs (Chapter 4). We performed an exhaustive analysis of the binary R 145 in the Large Magellanic Cloud (LMC), which was claimed to host the most massive stars known. We were able to disentangle the spectrum of the system, and performed an orbital, polarimetric, and spectral analysis, as well as an analysis of the wind-wind collision region. The true masses of the binary components turned out to be significantly lower than suggested, impacting our understanding of the initial mass function and stellar evolution at low metallicity (Chapter 5). Finally, all known WR binaries in the Small Magellanic Cloud (SMC) were analyzed. Although it was theoretical predicted that virtually all WR stars in the SMC should be formed via mass-transfer in binaries, we find that binarity was not important for the formation of the known WR stars in the SMC, implying a strong discrepancy between theory and observations (Chapter 6). Durch ihre intensive Strahlung, Sternwinde und Supernovaexplosionen tragen massereiche Sterne (Minitial & 8 M ) erheblich zur Entwicklung von Galaxien bei. In den letzten Jahren wurde es immer klarer, dass sich die Mehrheit der massereichen Sterne in Doppelsternsystemen befindet. Die vorliegende Doktorarbeit hat das Ziel, den Einfluss dieser Tatsache auf die Entwicklung massereicher Sterne quantitativ zu untersuchen. Um dies zu erreichen, haben wir eine Analyse der Umläufe, Spektren und Entwicklung verschiedener Doppelsternsysteme in der lokalen Gruppe durchgeführt, die OB-Sterne, massereicher Röntgendoppelsterne (HMXBs) und Wolf-Rayet-(WR)-Doppelsterne einschließt. Die Spektralanalyse wurde mithilfe des Potsdam-Wolf-Rayet-(PoWR)-Modellatmosphären-Programms für Strahlungstransport in Abwesenheit von lokalem thermodynamischen Gleichgewicht (non-LTE) durchge- führt. Das PoWR-Programm wurde im Laufe der Arbeit aktualisiert, sodass die Berechnung der hydro- statischen Schichten des Sternes nun wesentlich genauer erfolgt, was die Verwendung dieses Programms für alle Typen heißer massereicher Sterne erlaubte (Kapitel 2). Das bedeckungsveränderliche Dreifach- sternsystem δ Ori diente als Test für diese neue Version von PoWR, und lieferte wesentliche Informationen bezüglich der Entstehung von Röntgenstrahlung in massereichen Sternen (Kapitel 3). Die Analyse zweier prototypischer massereicher Röntgendoppelsterne, Vela X-1 und IGR J17544-2619, machte den Ursprung der Dichotomie der zwei Hauptklassen der Röntgendoppelsterne deutlich (Kapitel 4). Eine umfassende Analyse des Doppelsterns R 145 in der Großen Magellanschen Wolke (LMC), der angeblich aus den massereichsten uns bekannten Sternen besteht, wurde durchgeführt. Mithilfe einer Dekomposition des Spektrums, einer Orbital- und Spektralanalyse, sowie einer Analyse der Kollision von Sternwinden in diesem System konnten wir zeigen, dass die Massen der Komponenten wesentlich kleiner sind als bisher angenommen. Dies ist ein wichtiger Beitrag zu unserem Verständnis der Anfangsmassenfunktion und der Entwicklung massereicher Sterne in Umgebungen geringer Metalizität (Kapitel 5). Schließlich wurde die Gesamtpopulation der WR-Doppelsterne in der Kleinen Magellanschen Wolke (SMC) analysiert. Im Widerspruch zur theoretischen Vorhersage, alle WR-Doppelsterne in der SMC seien dank Massentransfer in Doppelsternsystemen entstanden, finden wir, dass Massentransfer unerheblich für die Entstehung der uns bekannten WR-Sterne in der SMC war (Kapitel 6). 3 Contents 1. Introduction 9 1.1. Stellar winds......................................... 10 1.2. Wolf-Rayet stars....................................... 11 1.3. Binary interaction and evolution............................... 12 1.4. Roche Lobe overflow..................................... 13 1.5. Overview of the manuscripts................................. 15 1.5.1. Manuscript I...................................... 15 1.5.2. Manuscript II...................................... 15 1.5.3. Manuscript V...................................... 15 1.5.4. Manuscript IV..................................... 16 1.5.5. Manuscript III..................................... 16 2. On the consistent treatment of the quasi-hydrostatic layers in hot star atmospheres (Manuscript I) 17 2.1. Introduction.......................................... 17 2.2. The PoWR code........................................ 19 2.2.1. The Basics...................................... 19 2.2.2. The quasi-hydrostatic domain............................ 20 2.2.3. The quasi-hydrostatic treatment in different stellar atmosphere codes........ 23 2.2.4. The effective gravity................................. 25 2.3. Results and discussion.................................... 27 2.3.1. Test model details.................................. 27 2.3.2. Comparison with fixed ggrav ............................. 29 2.3.3. Comparison with fixed geff .............................. 30 2.3.4. Blanketing and Doppler velocity influence...................... 32 2.4. Comparison with TLUSTY.................................. 33 2.5. Summary and conclusions.................................. 36 2.6. acknowledgements...................................... 37 3. A coordinated X-ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Orionis Aa: A Multiwavelength, Non-LTE spectroscopic analysis (Manuscript II) 39 3.1. Introduction.......................................... 39 3.2. Observational data...................................... 42 3.3. Non-LTE photosphere and wind modeling.......................... 43 3.3.1. The PoWR code................................... 43 3.3.2. The analysis method................................. 44 3.3.3. Initial assumptions.................................. 45 3.4. Results............................................. 46 3.4.1. Which distance is the correct one?.......................... 47 3.4.2. Constraining the parameters of Aa2 and Ab..................... 49 3.4.3. Bulk and turbulent motions.............................. 52 3.4.4. Uncertainties..................................... 55 3.5. Inhomogeneities in the primary’s wind............................ 56 3.5.1. Microclumping.................................... 56 3.5.2. Macroclumping.................................... 58 5 Contents 3.6. Where do the X-rays in δ Ori A come from?......................... 59 3.6.1. Auger ionization................................... 60 3.6.2. f/i analysis...................................... 60 3.6.3. X-ray line modeling................................. 63 3.7. Summary and Conclusions.................................. 66 3.8. Acknowledgements...................................... 67 4. Measuring the stellar wind parameters in IGR J17544-2619 and Vela X-1 constrains the accretion physics in Supergiant Fast X-ray Transient and classical Supergiant X-ray Bi- naries (Manuscript III) 69 4.1. Introduction.......................................... 69 4.2. The observations....................................... 71 4.3. The PoWR code....................................... 73 4.4. The fitting procedure..................................... 74 4.4.1. IGR J17544-2619................................... 75 4.4.2. Vela X-1....................................... 81 4.5. Discussion.......................................... 85 4.5.1. Wind-fed accretion.................................. 85 4.5.2. Evolutionary tracks.................................. 91 4.5.3. Asymmetries in spectral lines of Vela X-1..................... 91 4.6. Summary and conclusions.................................. 93 5. The Tarantula Massive Binary Monitoring: II. First SB2 orbital and spectroscopic analy- sis for the Wolf-Rayet binary R 145 (Manuscript IV) 95 5.1. Introduction.........................................
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