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  • 1
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2020-10-07
    Description: The main topic of this work is the introduction of time dependence into PHOENIX. This has been achieved for both the radiation field and the matter in the SN Ia model atmosphere. First, time dependence in the radiative transfer equation has been implemented. Two discretization schemes have been used for the implementation of the time derivative. Test calculations have been performed to confirm the correctness of the implementations. The radiation time scale computed with the time dependent radiative transfer is comparable to a simple analytic approach. Perturbations of the inner boundary condition of the atmosphere move through the whole atmosphere. For instance, an atmosphere with a sinusoidally varying inner light bulb leads to an atmosphere where the luminosity varies sinusoidally everywhere. For the next extension of time dependence for the matter, a simple hydrodynamical solver has been implemented. It computes the changes in the energy of an SN Ia atmosphere by considering the homologous expansion, energy transport and the deposition of energy by g -ray emission due to the radioactive decay of 56Ni and 56Co. Test calculations verified that each part of the solver works correctly. The energy deposition heats the atmosphere and increases the observed luminosity, whereas the adiabatic e expansion cools the atmosphere. The energy transport always pushes the temperature structure of the atmosphere towards the radiative equilibrium state ...
    Description: thesis
    Keywords: 523 ; THI 000 ; THU 162 ; Helligkeit von Sternen {Astronomie} ; Supernovae {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 107 S.
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  • 2
    Publication Date: 2021-03-29
    Description: Spectro-astrometry is a technique to obtain information about the structure of an astronomical source on sub-diffraction limited spatial scales down to milli- or micro-arcseconds. The method exploits the shift of the photocentre of a structured source over emission/absorption lines in its spectral energy distribution. Sub-diffraction limited resolution can be achieved because the method only uses wavelength-differential information of longslit spectra. Although spectro-astrometry has already been devised by Bailey (1998) and some studies have been performed to date on different astronomic targets, so far, no systematic analysis of the potential of this technique has been undertaken. The aim of this work was to analyse the potential of the method, develop the tools to exploit this potential and write the software which is needed to perform the analysis procedure. To verify the practical feasibility, observations were done with the VLT/CRIRES facility to demonstrate the capabilities of the method with respect to detecting structures on giant star surfaces. All steps of data reduction were analysed with respect to their influence on the spectro-astrometric quantities and a new method for bad pixel detection was devised and implemented ...
    Description: thesis
    Keywords: 523 ; THT 600 ; THK 000 ; THT 400 ; Riesensterne {Astronomie} ; Spektren und Spektroskopie von Sternen {Astronomie} ; Kalte Sterne {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 109 S.
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  • 3
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: This thesis deals with the high-energy emission from young stellar objects, which are on the one hand still actively accreting from their disk, and on the other hand are no longer deeply obscured by their natal cloud. Stars of spectral type B and A are called Herbig Ae/Be (HAeBe) stars in this stage, all stars of later spectral type are termed classical T Tauri stars (CTTS); strictly speaking both types are defined by spectroscopic signatures, which are equivalent to the evolutionary stage described above. In this thesis CTTS and HAeBes are studied through high-resolution X-ray and UV spectroscopy and through detailed physical simulations. Spectroscopic X-ray data is reduced and presented for two targets: The CTTS V4046 Sgr was observed with Chandra for 100 ks, using a high-resolution grating spectrometer. The lightcurve contains one flare and the He-like triplets of Si XIII, Ne IX and O VII indicate high densities in the X-ray emitting regions. The second target is the HAeBe HD 163296, which was observed with XMM-Newton for 130 ks. The lightcurve shows only moderate variability, the elemental abundance follows a pattern, that is usual for active stars. The He-like triplet of O VII exhibits line ratios similar to coronal sources, indicating that neither a high density nor a strong UV-field is present in the region of the X-ray emission ...
    Description: thesis
    Keywords: 523 ; THP 000 ; Thermodynamische Vorgänge in Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 84 S.
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  • 4
    Publication Date: 2021-03-29
    Description: Many stars evolve not alone but along one or more companions. While the evolution of single isolated stars is well predicted by theoretical calculations, close binary systems with their interactions are on the one hand far more difficult to handle, but on the other hand well constrained in their masses and sizes. One mechanism thought to produce such close binaries is the Common Envelope Evolution (CEE). Especially young post CEE binaries show great temperature differences between both components of about a factor 10 at a separation of just a few solar radii. This work focuses on close binary systems with a hot primary component (e.g. a subdwarf O-type star (sdO)) and a much cooler secondary component (e.g. a main-sequence star), which is heavily influenced by external radiation originating from the first. The technique to include external radiation into the stellar atmosphere code PHOENIX, i.e., the deviation of the outer boundary condition and the change in the temperature correction method, is described in detail. To concentrate on the irradiation effect, other difficulties such as asymmetric effects due to tear-drop shaped stars, ongoing mass accretion or shadows of a circumbinary disc, are avoided by selecting pre-cataclysmic variables (pre CVs) out of the class of close binaries as laboratory. The total eclipsing binary system UU~Sagittae is used as an example for massive irradiation and observed spectral features in the optical are fitted ...
    Description: thesis
    Keywords: 523 ; THK 000 ; THT 900 ; Spektren und Spektroskopie von Sternen {Astronomie} ; Doppelsterne {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 100 S.
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  • 5
    Publication Date: 2021-03-29
    Description: The term "stellar activity" summarizes a number of phenomena on the stellar surface and in the stellar atmosphere. The origin of many of these phenomena are changes in the structure of the stellar magnetic field. While it is possible to directly observe different forms of activity on the Sun in great detail, this remains impossible for other stars. However, by analyzing the spectra of these stars, information about their activity can be obtained. This thesis addresses two aspects of activity: First, the X-ray emission from the positions of A-type stars and a possible mechanism to produce these X-rays and second, the chromospheric activity in the spectral range from late A- to late K-type stars. Since the dynamo, which is responsible for the activity of solar-like stars, emerges in the range of late A- to early F-type stars, this spectral range is of special interest for the understanding of the activity phenomena. To study the X-ray activity of A-type stars, their optical positions as given in the Bright Star Catalogue were compared with the positions of the X-ray sources listed in the ROSAT catalogs. The matching criteria for the ROSAT All-Sky Survey data were 90 arcseconds, 36 arcseconds for the pointing observations with the PSPC and 18 arcseconds for HRI data. Those stars which could be associated with X-ray sources were tested for indications of hidden late-type companions. Variations in the radial velocity, the proper motion, and the light curve were interpreted as signs for binarity...
    Description: thesis
    Keywords: 523 ; THP 000 ; THN 400 ; Thermodynamische Vorgänge in Sternen {Astronomie} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
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  • 6
    Publication Date: 2021-03-29
    Description: In this work, nonanalytical line profiles for both cool and hot, dense atmospheres are added to the opacity calculations of the multipurpose stellar atmosphere code PHOENIX. Their influence on model atmospheres and synthetic spectra is studied. Model atmospheres are necessary in order to calculate synthetic spectra and to derive reliable stellar parameters. For cool, dense atmospheres, i.e., of objects of spectral type similar to and lower than latetype M, vanderWaals broadening is the most important pressure broadening mechanism. The spectra of these objects below ~1 micro-meter are dominated by alkali resonance lines. The profiles of the alkali resonance lines, especially of Na ID and KI, determine mostly the pseudo continuum in this wavelength range. Up to this work, classical analytical impact approximated alkali near line wing profiles perturbed by H2, He, and HI, which are the dominant perturbing particles, have been applied. In this work, various nonanalytical alkali line profiles, including far line wing and near line wing profiles, for Na I D, Li I, KI, and Rb I are included in order to describe the strong alkali absorption features which are characteristic for latetype dwarfs. For the alkali resonance line profiles, different theoretical approaches were used describing the far and near line wings. Non analytical alkali profiles for the far and near line wings perturbed by H2 and He are provided in the unified semiclassical theory...
    Description: thesis
    Keywords: 523 ; 550 ; THN 400 ; THK 000 ; Sternatmosphären {Astronomie} ; Spektren und Spektroskopie von Sternen {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 156 S.
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  • 7
    Publication Date: 2021-03-29
    Description: Die H.E.S.S. Kollaboration betreibt ein stereoskopisches System aus vier großen abbildenden Cherenkov-Teleskopen für den Nachweis sehr hochenergetischer Gamma-Strahlung (VHE; 〉 100 GeV). In dieser Arbeit wird über den Nachweis zweier neuer Quellen sehr hochenergetischer Gamma-Strahlung mit den H.E.S.S.-Teleskopen berichtet. Die extragalaktische Quelle 1ES0347-121 gehört zur Klasse der BL Lac Objekte und ist der aktive Kern einer entfernten Galaxie. Detektiert mit einer Signifikanz von mehr als 10 Standard-Abweichungen, ist es die bisher am weitesten entfernte Quelle sehr hochenergetischer Gamma-Strahlung (Rotverschiebung z = 0.1880). Ihr Energiespektrum läßt sich gut durch ein Potenzgesetz mit Photonindex Gamma = 3.08 +/- 0.23_stat +/- 0.1_sys beschreiben. Der integrale Fluss I(E 〉250GeV) entspricht ~2% des Flusses des Krebsnebels. Mit Hilfe des hochenergetische Gamma-Strahlungsspektrum von 1ES 0347-121 werden Einschränkungen auf die Dichte des extragalaktischen diffusen Photonfeldes bestimmt (s. unten). Bei der zweiten Quelle handelt es sich um die ausgehnte Quelle HESS J1023-577, die mit dem jungen, massiven Sternenhaufen Westerlund 2 und dessen Umgebung assoziert wird. Junge und massereichen Sterne strahlen starke Sternenwinde ab, die durch Schockbeschleunigung hochenergetische Teilchen produzieren können. Zum erstenmal konnte eine Quelle sehr hochenergetischer Gamma-Strahlung mit einer solchen Umgebung sicher identifiziert werden. Das Energiespekrum reicht von ~400GeV bis ~20TeV und läßt sich gut durch eine Potenzgesetz mit Photonindex Gamma=2.53 +/- 0.16_stat +/- 0.1_syst beschreiben.
    Description: thesis
    Keywords: 523 ; TIE 400 ; TBK 000 ; TCE 240 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Hochenergieastronomie ; Röntgen- und Gammateleskope {Astronomische Instrumente}
    Language: English
    Type: monograph , publishedVersion
    Format: 123 S.
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  • 8
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: Unter stellarer Aktivität werden eine Reihe von Phänomenen in den unterschiedlichen Atmosphärenschichten zusammengefasst, die eng mit dem Magnetfeld des einzelnen Sterns verbunden sind. Da eine direkte Auflösung der Sternoberfläche, wie uns dies bei der Sonne möglich ist, für aktive Sterne noch in ferner Zukunft liegt, können diese Phänomene im Normalfall nicht direkt beobachtet werden. Es können aber aus der Spektralanalyse indirekt Informationen über die Aktivität eines Sterns gewonnen werden. Die vorliegende Arbeit beschäftigt sich mit koronaler und chromosphärischer Aktivität von mittleren und späten M Sternen und deren Nachweis und Analyse in UVES Echelle-Spektren von 3030 bis 3880 und 4580 bis 6680 A. Dabei widmet sich der erste Teil der Arbeit dem Nachweis der verbotenen koronalen Fe XIII Linie bei 3388 A. Das mehrere Millionen Kelvin heiße koronale Gas wird normalerweise - und am leichtesten - im Röntgenbereich beobachtet...
    Description: thesis
    Keywords: 523 ; THK 000 ; THN 400 ; Spektren und Spektroskopie von Sternen {Astronomie} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 101 S.
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  • 9
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The high ionization state of the intergalactic medium (IGM) is maintained by the metagalactic UV background radiation. This ionizing radiation field is supposed to be the integrated radiation of quasars and young star-forming galaxies, which is reprocessed and attenuated by the intergalactic gas. Since the UV background is inaccessible to direct observations, it is impossible to test theoretical predictions of its spectral energy distribution in great detail. However, constraints can be derived from studies of metal absorption systems, the HI Lyman alpha opacity, or the HeII Lyman alpha forest, respectively. Observations of the HeII/HI column density ratio eta particularly probe the variations of the UV background. Since unobscured quasars permitting observation of HeII absorption are rare, there are only two lines of sight, towards the quasars HE2347-4342 and HS1700+6416, where the HeII Lyman alpha forest can be resolved. This work presents a study of the UV background at redshifts z 〈 3 investigating the HeII absorption towards the quasars HS1700+6416 (z = 2.72), which provides the second line of sight where the HeII Lyman alpha forest is resolved. The numerous metal line systems detected in the spectra of this QSO are studied in order to avoid biases due to unrecognized metal line absorption in the HeII forest. In this connection, several shapes of the ionizing radiation are tested for each system. The majority of the considered systems, in particular those at z 〉 2, is best reproduced with an ionizing radiation similar to the UV background of Haardt & Madau (2001), where the HeII break, formally located at 4 Ryd, is shifted to lower energies (~ 3 Ryd), probably due to the opacity of the higher HeII Lyman series lines ...
    Description: thesis
    Keywords: 523 ; TIE 400 ; TBI 000 ; Spektren und Leuchtkraft von Sternsystemen {Astronomie} ; Ultraviolett-Astronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 131 S.
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  • 10
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 523 ; TIE 900 ; TBG 000 ; TC 200 ; Sonstige Sternensysteme {Astronomie} ; Infrarot-Astronomie ; Astronomische Beobachtungen vom Weltraum aus
    Language: English
    Type: monograph , publishedVersion
    Format: 181 S.
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  • 11
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The Levantine Basin - a seismic investigation of the crustal structure and the evolution of the Messinian evaporites ABSTRACT This work presents an analysis of the crustal structure of the Levantine Basin, based on refraction seismic and gravity data, and an analysis of the evolution of the Messinian evaporites, based on reflection seismic data. Forward and inverse modelling of refraction seismic traveltimes along two profiles yielded 2-D velocity-depth-profiles. Gravity modelling along these profiles provided further information on the crustal structure. A great number of reflection seismic profiles was used for the analysis of the Messinian evaporites, which allowed an exhaustive investigation of the geometry of the evaporite layers, depositional phases of the evaporites and of their structural evolution. The Levantine Basin is located in the Southeastern Mediterranean Sea. The basin and its margin are key areas for the understanding of the geodynamic evolution of the Eastern Mediterranean. The opening of the Levantine Basin is closely related to the opening of the Neo-Tethys. Many geodynamic reconstructions of this area have been developed, but the key question, the origin of the crust, remained open. The Levantine Basin is also a world class site for studying the initial stages of salt tectonics driven by differential sediment load. The Messinian evaporites are comparatively young (deposited during the Messinian Salinity Crisis 5.9 - 5.3 Ma ago), the sediment load varies along the basin margin, they are hardly tectonically overprinted, and the geometry of the basin and the overburden is well-defined...
    Description: thesis
    Keywords: 550 ; TSF 000 ; VAE 820 ; VEF 000 ; Südeuropa und Mittelmeergebiet {Geophysik} ; Sedimentationsbecken als Erdkrustentypen {Geologie} ; Südeuropa und Mittelmeergebiet {Geologie}
    Language: English
    Type: monograph , publishedVersion
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  • 12
    Publication Date: 2021-03-29
    Description: Central Asia is characterized by a number of spectacular tectonic units such as the Tibetan Plateau, the Tien Shan intra-continental mountain belt and the Altyn Tagh strike-slip fault. Deformation of the lithosphere of these units is not well understood. In this dissertation, an attempt is made to answer the following tectonic questions: To what extent do the tectonic units formed in the upper crust in the course of the convergence between India and Eurasia weaken the underlying lithosphere? How is the Tibetan Plateau gravita-tionally compensated along its northern boundary? Do the Altyn Tagh and/or West Kunlun faults persist as vertical strike-slips throughout the crust and mantle lithosphere, thus representing a fundamental plate boundary? Which dynamic processes in the crust and mantle of the Tien Shan are responsible for intra-continental mountain building? What characterizes the local stress field in the Tien Shan and what causes the deformation of these mountains? To answer these questions, the elastic plate theory is used to interpret gravity and topography data, and in turn to derive specific characteristics of the lithospheric structure in Central Asia. Theoretical deflection of the elastic plate or plates were calculated using the 3D and 2D finite-difference methods. Variable-rigidity elastic plates are subjected to vertical and horizontal loads, shear forces, and terminal bending moments. Surface topo-graphic data from the Topo30 dataset is used as vertical surface loading to calculate the flexure of the elastic lithosphere...
    Description: thesis
    Keywords: 551.8 ; 622.15 ; 551 ; 550 ; VAE 400 ; VEK 000 ; TQA 000 ; TSK 000 ; VAE 400 ; VEK 000 ; TQA 000 ; TSK 000 ; Tektogenese {Geologie} ; Zentralasien {Geologie} ; Gravimetrische Verfahren {Geophysik} ; Zentralasien {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 136 Bl.
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  • 13
    Publication Date: 2021-03-29
    Description: Mit der Annahme schwacher Anisotropie vereinfachen sich die Lösungen der Modellierung und Inversion anisotroper Medien. Üblicherweise werden Perturbation-Methoden zur Beschreibung der Wellen-Ausbreitung in schwach anisotropen Medien verwendet, ein anisotropes Medium wird ersetzt durch ein isotropes Hintergrundmodell. Hier lässt sich die Wellenausbreitung leicht behandeln und die anisotropen Effekte werden mit Hilfe der Perturbations-Methode berechnet. Um die jeder Perturbations-Methode anhaftenden Fehler zu minimieren, sollte das gewählte isotrope Hintergrundmedium dem korrektem anisotropen Medium so ähnlich wie möglich sein. Zur Bestimmung des optimalen isotropen Mediums wurden Formeln für sektoriell best angepasste isotrope Medien entwickelt. Deren Anwendung wurde anhand von Modellen mit transversal isotropen und orthorombischen Symmetrien gezeigt...
    Description: thesis
    Keywords: 551.22 ; 550 ; Seismische Wellen {Geophysik} ; Übertragungsmedien {Seismologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 134 S.
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  • 14
    Publication Date: 2021-03-29
    Description: The Aggregated Carbon Cycle, Atmospheric Chemistry, and Climate model (ACC2) (Tanaka and Kriegler et al., 2007a) describes physical-biogeochemical processes in the Earth system at a global-annual-mean level. Compared to its predecessors NICCS (Hooss, 2001) and ICM (Bruckner et al., 2003), ACC2 adopts more detailed parameterizations of atmospheric chemistry involving a set of agents (CO2, CH4, N2O, O3, SF6, 29 species of halocarbons, sulfate aerosols (direct effect), carbonaceous aerosols (direct effect), all aerosols (indirect effect), stratospheric H2O, OH, and pollutants NOx, CO, and VOC). In contrast to the Impulse Response Function (IRF) approaches in the predecessor models, ACC2 uses DOECLIM (Kriegler, 2005), a land-ocean Energy Balance Model (EBM), to calculate temperature change. The carbon cycle is described by box models based on the IRF approach. A temperature feedback is newly implemented to ocean and land CO2 uptake. The most novel aspect of ACC2 is its inverse estimation, the first attempt to estimate uncertain parameters simultaneously for the carbon cycle, atmospheric chemistry, and climate system by taking their interactions into account. Theoretical underpinning of the ACC2 inversion is the probabilistic inverse estimation theory (Tarantola, 2005), which characterizes the ACC2 inversion as an integration of the existing Earth system knowledge. This includes parameter estimates, observational databases, reconstructions, and physical-biogeochemical laws...
    Description: thesis
    Keywords: 551.5 ; TUA 500 ; TOY 000 ; TVA 200 ; VJD 000 ; Meteorologische Modelle ; Energiebilanzen in der Geodynamik {Geophysik} ; Zusammensetzung der Atmosphäre {Meteorologie} ; Geochemie der Atmosphäre
    Language: English
    Type: monograph , publishedVersion
    Format: 300 S.
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  • 15
    Publication Date: 2021-03-29
    Description: Aim of the study was to test the capability of multiple trace gas analyses for the assessment of regional carbon budgets. Therefore, air samples were taken by airborne and ground level activities during several field campaigns within Europe. Basic elements for the data acquisition were the development of an adapted sampling system and of an enhanced investigation strategy. By the study important processes like insufficient mixing and advection were identified which could seriously effect the measurements and thus the calculated budgets. The concluding results prompt for improvements regarding appropriate flux estimation techniques and application of the enhanced investigation strategy within a frame of combined measurement activities.
    Description: thesis
    Keywords: 551.5 ; 550 ; TUA 700 ; VJI 000 ; VJD 100 ; TVA 210 ; Verfahren zur Untersuchung der freien Atmosphäre {Meteorologie} ; Geochemische Kreislaufmodelle ; Geochemie der Ungestörten Atmosphäre ; Chemische Zusammensetzung der Atmosphäre {Meteorologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 344 S.
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  • 16
    Publication Date: 2021-03-29
    Description: The southeastern Mediterranean Sea and the northern section of Egypt constitutes one of the most complex tectonic areas in the Mediterranean. This study is an attempt to achieve a better understanding of tectonics, and geodynamical processes along a complex tectonization region. These include crustal structure, thickness of sediments, transition between oceanic and continental crust and regional integrated model of the gravity field observed. A wide range of field work from the geophysical data has been acquired and used in this study with respect to the gravity and magnetic data as well as the results of deep seismic soundings. A comparison between the marine gravity data and the gravity data derived from satellite altimetry was made to ensure that the marine gravity data compiled from different marine surveys were compatible...
    Description: thesis
    Keywords: 622.15 ; 551.1 ; 550 ; TSZ 100 ; VAE 880 ; TSZ 100 ; VAE 880 ; Atlantischer Ozean {Geophysik} ; Passive und aktive Kontinentalränder {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 184 Bl.
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  • 17
    Publication Date: 2021-03-29
    Description: Context Extragalactic absorbers with column densities exceeding NH I 〉 2 × 1020 hydrogen atoms cm-2 are generally termed damped Ly alpha (DLA) systems. The absorbers are basically comprised of predominantly neutral gas, which is an essential prerequisite for the formation of stars. The spectroscopy of absorbers offers the best possibility to study the chemical composition of the supposed equivalents of the interstellar medium of local galaxies at an earlier stage of cosmic evolution. Absorbers in the sub-DLA range with NH I 〉 1019 cm-2 may consist of predominantly neutral gas, if the cosmic UV background is reduced...
    Description: thesis
    Keywords: 523 ; TII 040 ; Physikalische Eigenschaften {Astronomie: Interstellare Materie}
    Language: English
    Type: monograph , publishedVersion
    Format: 68 S.
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  • 18
    Publication Date: 2021-03-29
    Description: With the last generation of X-ray satellites, such as XMM-Newton and Chandra, our knowledge about the X-ray properties of Active Galactic Nuclei (AGN) has greatly improved. Detailed spectroscopy and long-term observations of hundreds of kilo-seconds have provided new insights into the mechanisms of X-ray production, its modification by intervening matter, and X-ray variability. In this thesis I present radiative transfer modeling of AGN in the Far-UV and X-ray range. The modeling considers several aspects of the observed X-ray properties: the Compton reflection/reprocessed component, X-ray variability and flares, and the effects of the warm absorber. For the X-ray reprocessing, I investigate in detail the magnetic flare model assuming solar-like magnetic reconnections above the accretion disk
    Description: thesis
    Keywords: 523 ; TEG 440 ; TBK 000 ; Schwarze Löcher {Astronomie: Kosmogonie} ; Hochenergieastronomie
    Language: English
    Type: monograph , publishedVersion
    Format: 151 S.
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  • 19
    Publication Date: 2021-03-29
    Description: PHOENIX has been used to calculate model atmospheres of classical novae in the X-ray spectral range. The models account for an expanding, one-dimensional spherically symmetric medium in full non-local thermodynamic equilibrium. Nova atmospheres have been modeled with PHOENIX since the early 90's to fit the early nova spectra in the ultraviolet and infrared spectral ranges. In this work the PHOENIX-code has been enhanced to also model X-ray spectra. This was accomplished by accounting for atomic data and physical processes. The synthetic spectra were compared to observations from the LETGS onboard the CHANDRA X-ray satellite. The template is the observation of nova V4743 Sagittarii in March 2003. The spectrum is very spectacular because of the nova brightness and CHANDRA's spectral resolution. Further observations from July2003, September 2003, and February 2004 were taken. Models with solar and non-solar abundances have been calculated and the synthetic spectra have been fitted to the four observations. The fits were used to discuss discrepancies between models and observations. The effective temperature of the atmosphere, the hydrogen column density, and the abundances ofhelium, carbon, nitrogen, oxygen, and iron in the shell were determined by the fits. It was examined how the parameters evolve with time. With the models the atmosphere structure and NLTE effects were determined. The models were compared to the previous nova model atmospheres from PHOENIX ...
    Description: thesis
    Keywords: 523 ; THU 155 ; THN 400 ; Eruptionsveränderliche {Astronomie: Sterne} ; Sternatmosphären {Astronomie}
    Language: English
    Type: monograph , publishedVersion
    Format: 196 S.
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  • 20
    Publication Date: 2021-03-29
    Description: The Sun shows a variety of transient surface features which are summarized as solar activity. Activity phenomena, apparently similar to the solar case, are also observed on stars other than the Sun. Stellar activity is closely related to magneto-hydrodynamic processes in a stars̉ convection zone. A dynamo is believed to operate in the outer convection zone of solar-like stars, generating magnetic fields by complex motions of the convecting plasma under the influence of rotation. Differential (i.e. non-rigid) rotation of the stellar surface is an important indicator of the overall dynamics of a stars̉ outer convection zone. Sunspots are a conspicuous token of solar activity; dark spots can also be observed on the surface of stars other than the Sun. To which degree starspots are analogues of sunspots is presently only poorly known; the processes governing their lifetime and structure are largely unexplored. Doppler imaging overcomes the diffraction-limitations of direct and interferometric imaging techniques by making use of information that is modulated into a star’s spectrum due to its rotation. Doppler imaging is currently the only method to produce well-resolved images of solar-like stars. After a selective review of the observational and theoretical foundation,
    Description: thesis
    Keywords: 523 ; THN 400 ; THE 400 ; Sternatmosphären {Astronomie} ; Rotation, Eigenbewegung {Astronomie: Sterne}
    Language: English
    Type: monograph , publishedVersion
    Format: 187 S.
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  • 21
    Publication Date: 2021-03-29
    Description: Reflection seismic is one of the most commonly used geophysical method for the oil and gas exploration. In this thesis I show the application of the Common Reflection Surface (CRS) stack technique to improve the quality of reflection seismic images. Conventional seismic imaging method based on the CMP stacking does not use the full potential of the dataset due to reflection point dispersal in the presence of dipping reflectors or laterally inhomogeneous media. Application of the CRS stack technique is advantageous in complex areas, since it involves information about the shape of seismic reflectors, i.e., dip and curvature, into processing. Moreover, a multiparameter formula allows to sum up more traces during the stack. All together, this leads to better imaging results, especially to an improvement of the signal-to-noise (S/N) ratio. Reflection events in the CRS stack sections appear clearer and more continuous compared to conventional CMP stack sections...
    Description: thesis
    Keywords: 622.15 ; TQC 220 ; VRE 110 ; Reflexionsseismik {Geophysik} ; Geophysikalische Verfahren
    Language: English
    Type: monograph , publishedVersion
    Format: 129 S.
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  • 22
    Publication Date: 2021-03-29
    Description: Interpretation of high and very high resolution reflection seismic data from the western Black Sea shelf yielded a seismic stratigraphic model of the Late Quaternary deposits on the southwestern Black Sea shelf. This model was combined with borehole information to carry out a regional subsidence analysis, so that the influence of tectonics and sediment compaction could be ruled out in the estimation of sea-level changes in the Black Sea. Mio-Pliocene sediments form the baseline of the interpretation. On top of it four Quaternary seismic stratigraphic units were identified on the western Black Sea shelf; they are named in chronological order Unit 4 to Unit 1 (U4 U1). Pliocene deposits are built up by gently basinward dipping layers of relatively high and approximately uniform thickness. Buried graben structures attest to the influence of extensional tectonics until the Upper Pliocene. Later, strong erosion left a rugged surface on the inner and middle shelf that was later overlain by a thin layer of Quaternary to Holocene sediments. The Pliocene is followed by the oldest observed Quaternary seismic sequence (Unit 4, U4); it comprises layers of Lower Quaternary age that dip towards the basin at a steeper angle than those of the Pliocene. Within U4 the oldest of three Quaternary shelfedge delta systems in the study area was found, that supposedly marks an Early Quaternary sea-level lowstand...
    Description: thesis
    Keywords: 551 ; 551 ; 550 ; VDI 200 ; VEZ 120 ; TSZ 100 ; Quartär ; Randmeere {Geologie} ; Atlantischer Ozean {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 170 S.
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  • 23
    Publication Date: 2021-03-29
    Description: For seismic imaging of complex 3-D structures by e.g. prestack Kirchhoff depth migration large amounts of traveltime tables are required. This work provides a wavefront-oriented ray tracing technique for multi-valued traveltimes in smooth 3-D heterogeneous anisotropic media. In this method, wavefronts are propagated stepwise through the model and output quantities are interpolate (e.g., traveltimes, slowness) from rays to gridpoints. In contrast to isotropic media, where the input is a velocity model, the model for an anisotropic medium is defined by 21 elastic parameters at each gridpoint. To provide an efficient, accurate and fast algorithm for the interpolation of the elastic parameters to arbitrary points, the Cardinal Spline interpolation has been used, which produces an interpolated function that is continuous through the second derivative. The insertion of a new ray is performed by tracing it directly from the source. To calculate traveltimes at gridpoints a distance-weighted averaging method is used. To demonstrate the accuracy of the method the traveltimes computed for a homogeneous anisotropic model with elliptical symmetry are compared to exact traveltimes available for this medium. Since it exists no analytical solution for an inhomogeneous anisotropic model, I compare the results with an alternative method for traveltime computation, the FD perturbation method...
    Description: thesis
    Keywords: 622.1592 ; 550 ; TQC 200 ; Prospektionsseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 24
    Publication Date: 2021-03-29
    Description: Merapi volcano in Central Java, Indonesia, is considered one of the most dangerous volcanoes worldwide. Due to the high viscosity of its magma, the lava emerging at the top the volcano cannot flow silently down the flanks of the volcano but builds a lava dome. An indicator for the stability of the lava dome are rockfalls and block and ash flows, which are caused by local instabilities at the dome. When the lava dome reaches a critical size, it collapses. This results in dangerous block and ash flows, which can reach several kilometers into the proximity of the volcano. In the past rockfall and block and ash flow activity has been observed visually or by seismic networks. However, visual observations are often impossible due to bad visibility conditions and until now seismic measurements allow only few insights into the dynamic processes that are involved in instability events, i.e. events of material breaks off the lava dome. In order to enhance monitoring of lava dome activity, a first prototype Doppler radar system has been installed at the western of the Merapi in October 2001. This system consists of a frequency modulated continuous wave (FMCW) 24GHz Doppler radar. The Doppler spectra recorded by the system give a relative measure of the amount of material moving through the beam as well as information about its velocities. Because the radar system is insensitive for clouds, the system provides first continuous "quasi-visual" observations of dome instabilities...
    Description: thesis
    Keywords: 551.21 ; TQD 800 ; TSJ 300 ; VAD 700 ; VAD 100 ; TSJ 300 ; VAD 700 ; VAD 100 ; Indonesien {Geophysik} ; Regionaler Vulkanismus {Geologie} ; Methodik in der Vulkanologie {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 156 S.
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  • 25
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    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: In this thesis, the 1997 Vogtland/NW-Bohemia swarm has been selected for the analysis of inhomogeneities in the stress field because two predominant nearly perpendicular flat zones of seismicity are visible in the hypocentre distribution implying inhomogeneities in the stress field. This is unusual compared to other swarms originating from this area. An existing dataset of waveform data, P- and S-phase picks, and master event locations has been analysed regarding similarity of waveforms, location refinement, and estimation of relative moment tensors. The latter are used together with a regional dataset of 50 single focal mechanisms and 125 focal mechanisms from the 2000 hydraulic fracturing experiment at the KTB for an estimate of the regional homogeneous and the locally inhomogeneous stress field. An automated processing procedure consisting of coherence analysis,precise relocation, relative moment tensor inversion, and stress trajectory determination has been set up. The coherence analysis has been successfully applied using a new method that uses three component seismograms. 457 events are separated into 13 multiplets of similar waveforms of at least size 8. Another result are precise relative arrival time measurements which are fed into the precise relocation program "hypoDD". Two nearly perpendicular structures are found in the hypocentre distribution. 352 moment tensors are estimated using a relative moment tensor inversion. Three different algorithms to distinguish between fault plane and auxiliary plane are successfully applied to them...
    Description: thesis
    Keywords: 551.22 ; 550 ; VAE 130 ; TOH 400 ; Geomechanik ; Übertragungsmedien {Seismologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 184 S.
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  • 26
    Publication Date: 2021-03-29
    Description: Mittelozeanische Rücken finden sich in allen größeren Ozeanbecken der Erde. Sie besitzen die weltweit höchste Produktionsrate an Extrusiv- und Intrusivgesteinen. Bildung ozeanischer Kruste und Vulkanismus an divergenten Plattengrenzen sind fundamentale Prozesse, deren Grundverständnis wichtig ist. Magmatische Dykes bauen einen Großteil ozeanischer Kruste auf. Ihr Vorkommen ist besonders augenfällig im sogenannten Sheeted-Dyke-Komplex der oberen Kruste. In dieser Arbeit wird die Wechselwirkung zwischen Magmakammern und Dykes aufgrund von Spannungsfeldern untersucht. Die Ergebnisse werden zur Analyse ozeanischer Krustenbildung im allgemeinen und des Sheeted-Dyke-Komplexes im besonderen benutzt. Da nur wenig Daten über die Geologie mittelozeanischer Rücken und den Verlauf magmatischer Prozesse verfügbar sind und analytische Modelle zumeist an der Berücksichtigung inhomogener Medien und heterogener Spannungsfelder scheitern, stellen numerische Modelle ein wichtiges Werkzeug zur weiteren Erforschung dieser Abläufe dar. Um den Aufstieg von Dykes als Fortbewegung fluidgefüllter Risse zu berechnen, wurde eine Randelementmethode verwendet. Modelle für den Magmaaufstieg im Mantel müssen sowohl die hohen Transportgeschwindigkeiten als auch die Trennung von Schmelze und Mantelgestein zur Verhinderung chemischer Ausgleichsreaktionen und die Fokussierung des Magmas von der breiten Schmelzzone in der Tiefe zur schmalen Austrittszone an der Rückenachse leisten...
    Description: thesis
    Keywords: 551.1 ; 550.28 ; 550 ; VAE 130 ; VAE 890 ; TSZ 000 ; Geomechanik ; Ozeanische Kruste {Tektonik} ; Meeresräume {Geophysik}
    Language: English
    Type: monograph , publishedVersion
    Format: 178 S.
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  • 27
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 622.15 ; 553.28 ; 550 ; TSI 000 ; VRE 160 ; VSI 000 ; TSI 000 ; VRE 160 ; VSI 000 ; Vorderasien {Geophysik} ; Regionale Exploration und Prospektion {Kohlenwasserstofflagerstätten} ; Vorderasien {Fossile Energieträger}
    Language: English
    Type: monograph , publishedVersion
    Format: 93 Bl.
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  • 28
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: thesis
    Keywords: 551.22 ; 550 ; TQC 100 ; Physikalische und mathematische Grundlagen {Geophysik: Seismik}
    Language: English
    Type: monograph , publishedVersion
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  • 29
    Publication Date: 2021-03-29
    Description: During several marine geophysical data acquisition cruises in the western Baltic Sea, for the Baltseis and NeoBaltic projects, a dense grid of 2D high-resolution multichannel seismics and to some extend gravity and magnetic data were acquired in the German and Danish territorial waters of the region. The western Baltic Sea comprises the northern part of the Northeast German Basin on the southern flank of the Ringkøbing-Fyn High. Furthermore, parts of the suture zone between the Avalonia and Baltica plates (the Caledonian Deformation Front) and the Sorgenfrei Tornquist Zone were investigated during these research cruises. Adjacent to the study area two structures are located, which are important for the structural evolution in the region. To the west the N-S trending Glückstadt Graben and in the eastern part the E-W running Grimmen High...
    Description: thesis
    Keywords: 550 ; VBM 000 ; VAE 820 ; TSB 000 ; VEB 110 ; TQC 200 ; Geologische Interpretation geophysikalischer Beobachtungen ; Sedimentationsbecken als Erdkrustentypen {Geologie} ; Mitteleuropa {Geophysik} ; Norddeutsche Senke {Geologie} ; Prospektionsseismik {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 30
    Publication Date: 2021-03-29
    Description: In this study different full waveform techniques was developed for the investigation of seismic ocean bottom single station data. These techniques were applied to data obtained in a pilot ocean bottom experiment in the Tyrrhenian Sea/Italy (TySea experiment) from December 2000 to May 2001. A network of broadband seven ocean bottom seismometers and seven ocean bottom hydrophones was installed above the subducting Ionian plate which descends from Southeast to Northwest. Local and teleseismic earthquakes were recorded by the stations. The newly developed techniques produce very promising results in reconstructing the sea floor structure beneath the stations and in attenuating waveform effects generated by water layer multiples. Additionally the techniques offer a possibility to determine the orientation of free fall ocean bottom seismometers. The main results are: 1. The waveform recorded at the seafloor differs from waveforms recorded at land stations. This is primarily due to multiple reflections in the water layer. These multiple reflections show different patterns on seismometer and hydrophone recordings depending on the seafloor structure. This opens the possibility to constrain the P-wave velocity structure beneath the station by means of a full waveform inversion...
    Description: thesis
    Keywords: 550 ; TSZ 100 ; VAE 890 ; TQC 700 ; Atlantischer Ozean {Geophysik} ; Ozeanische Kruste {Tektonik} ; Seismische Verfahren zur Feststellung von Atomexplosionen {Geophysik}
    Language: English
    Type: monograph , publishedVersion
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  • 31
    Publication Date: 2021-03-29
    Description: This work presents multichannel seismic and hydroacoustic data of four survey areas along the Red Sea Rift and the Dead Sea Transform Fault. Sedimentary Basins that developed due to the rifting of the Red Sea and the strike-slip displacement of the Dead Sea Transform Fault were investigated and models for their evolution were derived. The Red Sea Rift and the Dead Sea Transform Fault are the main tectonic features in the Middle East. The rifting process of the Red Sea that initiated in the late Oligocene and early Miocene separated the African Plate from the Arabian Plate. In the Middle Miocene, the extension was compensated in the northern part of the Red Sea with the initiation of the left lateral Dead Sea Transform Fault. Along the Red Sea, different stages of evolution can be observed. Whereas the southern part comprises already seafloor spreading, the northern part is assumed to be in the late stage of continental rifting. Because of huge evaporitic sediment layers within the entire Red Sea, direct basement observations are sparse. Surficial features like ocean deeps along the axis of the Red Sea are interpreted as first seafloor spreading cells in the transition process between seafloor spreading and continental rifting. Along the Dead Sea Transform Fault, 105 km of left lateral displacement are observed within the last 20 Ma. The displacement is most likely not continuous since its onset. The Dead Sea Transform Fault may have experienced a break in its history before 5 Ma...
    Description: thesis
    Keywords: 622.15 ; 551.8 ; 550 ; TSI 000 ; VAE 840 ; TSI 000 ; VAE 840 ; Vorderasien {Geophysik} ; Rifts {Geologie}
    Language: English
    Type: monograph , publishedVersion
    Format: 127 S.
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  • 32
    facet.materialart.
    Unknown
    Univ. Hamburg
    Publication Date: 2021-03-29
    Description: The purpose of the first part of this dissertation was to develop a migration algorithm for converted waves, and a tomographic method for estimating an interval shear wave velocity model. The developed algorithm is based on the Kirchhoff formalism. The elastic Kirchhoff integral and its implementation were discussed and summarised in Chapter 2. The derived migration integral was generalised for all types of multicomponent data. For practical reasons, multicomponent data are decomposed into their corresponding components (z,x, and y components), and the migration is performed separately for each component. Normally it is assumed that the decomposed wave components are free from other wave types. The migration result of each component shows particular characteristics of the subsurface. For example, PS data give the shear wave characteristics of the subsurface...
    Description: thesis
    Keywords: Reflexionsseismik {Geophysik} ; 622.15 ; 550 ; TQC 220
    Language: English
    Type: monograph , publishedVersion
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  • 33
    Publication Date: 2021-03-29
    Description: This work presents the first three-dimensional gravity and magnetic investigation along the convergent Peruvian margin. Three-dimensional magnetic modelling is still a relatively untried and challenging technique. The gravity and magnetic models image nearly the whole margin which has been only partly resolved with geophysical methods up to now. The gravity and magnetic models are constructed for three areas between 7.25ʿS and 16.75ʿS and are based on the available wide-angle seismic velocity models (Hampel et al., 2002a; Broser et al., 2002). The continental margin is characterised by positive free-air anomalies of varying amplitudes, indicating that the margin has been shaped by the subduction of different features on the Nazca Plate...
    Description: thesis
    Keywords: 551.1 ; 622.15 ; 550 ; TSX 800 ; TQA 000 ; TQB 000 ; VAE 880 ; VEX 800 ; Peru und Ecuador {Geophysik} ; Gravimetrische Verfahren {Geophysik} ; Erdmagnetische Verfahren {Geophysik} ; Passive und aktive Kontinentalränder {Geologie} ; Peru und Ecuador {Geologie}
    Language: English
    Type: monograph , publishedVersion
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