@phdthesis{Kneiske2004,
  author    = {Kneiske, Tanja},
  title     = {Wechselwirkung von Gammastrahlung mit dem metagalaktischen Strahlungsfeld},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-11479},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2004},
  abstract  = {Im Rahmen dieser Arbeit wurden Effekte der Paarbildung durch Wechselwirkung von hochenergetischer Gammastrahlung mit dem metagalaktischen FIR-UV Strahlungsfeld (MRF) untersucht. Einerseits hat die Paarbildung Folgen f"ur die beobachteten Spektren aktiver Galaxienkerne, andererseits hat sie auch einen gro"sen Einflu"s auf den extragalaktischen Gammastrahlungshintergrund. Es wurde ein verbesserte Version f"ur das Modell des FIR-UV Strahlungsfelds vorgestellt, mit dessen Hilfe aus beobachteten Daten intrinsische Blazarspektren ermittelt wurden. Im weiteren wurde ein auf EGRET-Blazaren basierendes Modell f"ur den Gammastrahlungshintergrund berechnet, in dem besonderer Wert auf die korrekte Beschreibung der Absorption prim"arer und der daraus resultierenden sekund"aren Gammastrahlung gelegt wurde. Schlie"slich wurde gezeigt, da"s der Beitrag von BL Lac Objekten zum Gammahintergrund nicht nur der fehlende Flu"s, sondern auch die spektrale Form der aus EGRET Beobachtungen gewonnenen Daten erkl"art werden kann, ohne den gegenw"artigen TeV-Daten zu widersprechen.},
  subject      = {Metagalaxis},
  language  = {de}
}
@phdthesis{Dorner2008,
  author    = {Dorner, Daniela},
  title     = {Observations of PG 1553+113 with the MAGIC telescope},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28196},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {Blazars are among the most luminous sources in the universe. Their extreme short-time variability indicates emission processes powered by a supermassive black hole. With the current generation of Imaging Air Cherenkov Telescopes, these sources are explored at very high energies. Lowering the threshold below 100 GeV and improving the sensitivity of the telescopes, more and more blazars are discovered in this energy regime. For the MAGIC telescope, a low energy analysis has been developed allowing to reach energies of 50 GeV for the first time. The method is presented in this thesis at the example of PG 1553+113 measuring a spectrum between 50 GeV and 900 GeV. In the energy regime observed by MAGIC, strong attenuation of the gamma-rays is expected from pair production due to interactions of gamma-rays with low-energy photons from the extragalactic background light. For PG 1553+113, this provides the possibility to constrain the redshift of the source, which is still unknown. Well studied from radio to x-ray energies, PG 1553+113 was discovered in 2005 in the very high energy regime. In total, it was observed with the MAGIC telescope for 80~hours between April 2005 and April 2007. From more than three years of data taking, the MAGIC telescope provides huge amounts of data and a large number of files from various sources. To handle this data volume and to provide monitoring of the data quality, an automatic procedure is essential. Therefore, a concept for automatic data processing and management has been developed. Thanks to its flexibility, the concept is easily applicable to future projects. The implementation of an automatic analysis is running stable since three years in the data center in W{\"u}rzburg and provides consistent results of all MAGIC data, i.e. equal processing ensures comparability. In addition, this database controlled system allows for easy tests of new analysis methods and re-processing of all data with a new software version at the push of a button. At any stage, not only the availability of the data and its processing status is known, but also a large set of quality parameters and results can be queried from the database, facilitating quality checks, data selection and continuous monitoring of the telescope performance. By using the automatic analysis, the whole data sample can be analyzed in a reasonable amount of time, and the analyzers can concentrate on interpreting the results instead. For PG 1553+113, the tools and results of the automatic analysis were used. Compared to the previously published results, the software includes improvements as absolute pointing correction, absolute light calibration and improved quality and background-suppression cuts. In addition, newly developed analysis methods taking into account timing information were used. Based on the automatically produced results, the presented analysis was enhanced using a special low energy analysis. Part of the data were affected by absorption due to the Saharan Air Layer, i.e. sanddust in the atmosphere. Therefore, a new method has been developed, correcting for the effect of this meteorological phenomenon. Applying the method, the affected data could be corrected for apparent flux variations and effects of absorption on the spectrum, allowing to use the result for further studies. This is especially interesting, as these data were taken during a multi-wavelength campaign. For the whole data sample of 54 hours after quality checks, a signal from the position of PG 1553+113 was found with a significance of 15 standard deviations. Fitting a power law to the combined spectrum between 75 GeV and 900 GeV, yields a spectral slope of 4.1 +/- 0.2. Due to the low energy analysis, the spectrum could be extended to below 50 GeV. Fitting down to 48 GeV, the flux remains the same, but the slope changes to 3.7 +/- 0.1. The determined daily light curve shows that the integral flux above 150 GeV is consistent with a constant flux. Also for the spectral shape no significant variability was found in three years of observations. In July 2006, a multi-wavelength campaign was performed. Simultaneous data from the x-ray satellite Suzaku, the optical telescope KVA and the two Cherenkov experiments MAGIC and H.E.S.S. are available. Suzaku measured for the first time a spectrum up to 30 keV. The source was found to be at an intermediate flux level compared to previous x-ray measurements, and no short time variability was found in the continuous data sample of 41.1 ksec. Also in the gamma regime, no variability was found during the campaign. Assuming a maximum slope of 1.5 for the intrinsic spectrum, an upper limit of z < 0.74 was determined by deabsorbing the measured spectrum for the attenuation of photons by the extragalactic background light. For further studies, a redshift of z = 0.3 was assumed. Collecting various data from radio, infrared, optical, ultraviolet, x-ray and gama-ray energies, a spectral energy distribution was determined, including the simultaneous data of the multi-wavelength campaign. Fitting the simultaneous data with different synchrotron-self-compton models shows that the observed spectral shape can be explained with synchrotron-self-compton processes. The best result was obtained with a model assuming a log-parabolic electron distribution.},
  subject      = {Aktiver galaktischer Kern},
  language  = {en}
}
@phdthesis{Meyer2008,
  author    = {Meyer, Markus},
  title     = {Observations of a systematically selected sample of high frequency peaked BL Lac objects with the MAGIC telescope},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-28115},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2008},
  abstract  = {At the beginning of regular observations with the MAGIC telescope in December 2004, all but one extragalactic sources detected at very high energy (VHE) gamma-rays belonged to the class of high frequency peaked BL Lac (HBL) objects. This motivated a systematic scan of candidate sources to increase the number of known sources and to study systematically their spectral properties. As candidate sources for VHE emission, X-ray bright HBLs were selected from a compilation of active galactic nuclei. The MAGIC observations took place from December 2004 to March 2006. The declination of the objects was restricted to values between -1.2° and +58.8° corresponding to a maximum zenith distance lower than 30° at culmination. Since gamma-rays are absorbed by photo-pair production in low energy background radiation fields, the redshift of the investigated objects was limitetd to z < 0.3. Under the assumption that HBLs generally emit the same energy flux at 1keV as at 200GeV, only the brightest X-ray sources were observed, leading to a cut in the X-ray flux of F(1keV) > 2µJy}. Of the fourteen sources observed, four have been detected: 1ES 1218+304 (for the first time at very high energies), 1ES 2344+514 (strong detection in a state of low activity), Mrk 421 and Mrk 501. A hint of a signal on a 3-sigma-level from the direction of 1ES 1011+496 has been observed. In the meantime the object has been confirmed as a source of VHE gamma-rays by a second MAGIC observation campaign triggered by an optical outburst. For ten sources, upper limits on their integral fluxes above 200GeV have been calculated on a 99\% confidence level. To cross calibrate the different data samples, collected during 14 months, bright muon ring images have been used, recorded as background events by the MAGIC telescope. Based on the development by Meyer (2003), the method has been improved and implemented into the automatic data analysis as a continuous monitor of the calibration and the point spread function of the optical system. While the ring images are generated by muons with small impact parameters, it could be shown that the image parameter distributions for muons with large impact parameters and gamma showers completely overlap, revealing these muons as the dominant background for gamma-ray observations below energies of 150GeV. The sample of HBLs (including all HBLs detected at VHE so far) has been investigated for correlations between broad-band spectral indices as determined from simultaneous optical, archival X-ray and radio luminosities, finding that the VHE emitting HBLs do not differ from the non-detected ones. In general the absorption corrected HBL gamma-ray luminosities at 200GeV are not higher than their X-ray luminosities at 1keV. Based on a complete X-ray BL Lac sample, the Hamburg/ROSAT X-ray BL Lac sample, the number of expected VHE sources has been estimated for the performed scan, finding a consistent number under the assumption of a 37\% completeness of the investigated sample and a 1keV-to-200GeV luminosity ratio of 1.4. An upper limit on the omnidirectional flux at 200GeV has been calculated by interpolating the sum over the observed fluxes and upper limits. Within the uncertainties, the result is in agreement with the expectations derived from the X-ray luminosity function of BL Lacs. For 1ES 1218+304 and 1ES 2344+514 the lightcurves have been derived, showing evidence for flux variability on a time scale of 17 days and 24h, respectively. In the case of 1ES 1218+304 variability has been reported for the first time at VHEs. For both sources the energy spectra have been reconstructed and discussed in the context of their broad band spectral energy distribution (SED), using a single zone synchrotron self Compton model. The SEDs are well fitted by the simulation even though the very high peak frequencies at gamma-rays push the model to its limits. The parameters derived from the simulation are in good agreement with the parameters found for similar HBLs.},
  subject      = {Aktiver galaktischer Kern},
  language  = {en}
}
@phdthesis{Summa2014,
  author    = {Summa, Alexander},
  title     = {Modelling high-energy observables of supernova explosions},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-94608},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2014},
  abstract  = {In this work, high-energy observables arising during different phases of SN explosions are studied with respect to their potential for allowing conclusions on suggested explosion scenarios and physical mechanisms that are thought to influence the evolution of SNe in a major way. The focus on selected observables at keV and MeV energies is motivated by the appearance of large degeneracies that can even be found for disparate scenarios in many wavelength regimes. Since the discussed emission in the high-energy regime is directly linked to nuclear processes being usually very distinct for different suggested physical models, the signatures at keV and MeV energies allow for meaningful comparisons of simulations with observations.},
  subject      = {Supernova},
  language  = {en}
}
@phdthesis{Elsaesser2011,
  author    = {Els{\"a}sser, Dominik Martin},
  title     = {Indirect Search for Dark Matter in the Universe - the Multiwavelength and Multiobject Approach},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-69464},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2011},
  abstract  = {Dunkle Materie ist ein zentraler Bestandteil der modernen Kosmologie, und damit von entscheidender Bedeutung f{\"u}r unser Verst{\"a}ndnis der Strukturbildung im Universum. Das offensichtliche Fehlen von elektromagnetischer Wechselwirkung in Kombination mit unabh{\"a}ngigen Messungen der Energiedichte der baryonischen Materie {\"u}ber die H{\"a}ufigkeit der primordialen leichten Elemente weisen auf eine nicht-baryonische Natur der Dunklen Materie hin. Die Wirkung der Dunklen Materie bei der Strukturbildung zeigt weiterhin dass ihre Konstituenten kalt sind, also zum Zeitpunkt des Gleichgewichts zwischen Strahlung und Materie eine Temperatur kleine als ihre Ruhemasse aufwiesen. Generische Kandidaten f{\"u}r das Dunkelmaterie-Teilchen sind stabile, schwach wechselwirkende Teilchen mit Ruhemassen von der Gr{\"o}ßenordnung der Skala der elektroschwachen Symmetriebrechung, wie sie zum Beispiel in der Supersymmetrie bei erhaltener R-Parit{\"a}t vorkommen. Derartige Teilchen frieren auf nat{\"u}rliche Weise im fr{\"u}hen Universum mit kosmologisch relevanten Reliktdichten aus. Die fortschreitende Strukturbildung im Universum f{\"u}hrt dann zur Bildung von {\"u}berdichten Regionen, in denen die Dunkelmaterie-Teilchen wiederum in signifikantem Ausmaß annihilieren k{\"o}nnen. Dadurch w{\"u}rde ein potentiell detektierbarer Fluß von Hochenergie-Teilchen einschließlich Photonen aus den instabilen Zwischenprodukten der Annihilationsereignisse erzeugt. Die Spektren dieser Teilchen w{\"u}rden R{\"u}ckschl{\"u}sse auf die Masse und den Annihilations-Querschnitt als wichtige Gr{\"o}ßen zur mikrophysikalischen Identifikation der Dunkelmaterie-Teilchen erlauben. Darin liegt die zentrale Motivation f{\"u}r indirekte Suchen nach der Dunklen Materie. Zum gegenw{\"a}rtigen Zeitpunkt jedoch haben weder diese indirekten Suchen, noch direkte Methoden zur Suche nach elastischen Streuereignissen zwischen Dunkelmaterie-Teilchen und Atomkernen sowie Beschleunigerexperimente einen eindeutigen Nachweis von Dunkelmaterie-Teilchen erbracht. Das an sich stellt keine {\"U}berraschung dar, denn die zu erwartenden Signale sind aufgrund der schwachen Wechselwirkung der Teilchen nur von geringer Intensit{\"a}t. Im Falle der indirekten Suchen steht zu erwarten, dass selbst f{\"u}r die gr{\"o}ßten Massekonzentrationen im Universum die St{\"a}rke des Annihilationssignals der Dunklen Materie den durch astrophysikalische Quellen verursachten Untergrund nicht {\"u}berschreitet. Die M{\"o}glichkeit der sicheren Unterscheidung zwischen einem m{\"o}glichen Signal aus der Annihilation der Dunklen Materie und eben diesem Untergrund ist daher entscheidend f{\"u}r die Erfolgsaussichten der indirekten Suchen. In der vorliegenden Arbeit wird eine neuartige Suchstrategie ausgearbeitet und vorgestellt, deren zentrale Komponente die Auswahl von Beobachtungszielen aus einem breiten Massebereich, die Kontrolle der astrophysikalischen Untergr{\"u}nde, und die Einbeziehung von Daten aus mehreren Wellenl{\"a}ngenbereichen ist. Die durchgef{\"u}hrten Beobachtungen werden vorgestellt und interpretiert. Ein Ergebnis ist, dass die Unsicherheiten in Bezug auf die Verteilung der Dunklen Materie in Halos und deren individuelle Dichtestruktur, sowie in Bezug auf die m{\"o}gliche Verst{\"a}rkung des Annihilationssignales durch Substruktur, im Falle der massearmen Halos (wie zum Beispiel bei den Zwerggalaxien) gr{\"o}ßer ist als bei massereichen Halos, wie denen der Galaxienhaufen. Andererseits weisen die massereichen Halos gr{\"o}ßere Unsicherheiten in Hinblick auf die zu erwartenden rein astrophysikalischen Untergr{\"u}nde auf. Die Unsicherheiten in Bezug auf die bisher unbekannte Teilchenphysik jenseits des Standardmodells schließlich sind unabh{\"a}ngig von der Masse der beobachteten Halos. Im Zusammenspiel erm{\"o}glichen es diese unterschiedlichen Skalierungsverhalten, die globale Unsicherheit durch eine kombinierte Analyse der Beobachtungen von Halos mit verschiedenen Massen, die einen bedeutenden Teil der Masseskala abdecken, nennenswert zu reduzieren. Diese Strategie wurde im Rahmen des wissenschaftlichen Beobachtungsprogrammes des MAGIC Teleskopsystems implementiert. Es wurden Beobachtungen von Zwerggalaxien sowie des Virgo- und des Perseus-Galaxienhaufens durchgef{\"u}hrt. Die resultierenden Grenzen auf Gammastrahlung aus der Annihilation von schwach wechselwirkenden, massereichen Teilchen geh{\"o}ren zum Zeitpunkt dieser Niederschrift zu den st{\"a}rksten Grenzen aus indirekten Suchen nach der Dunklen Materie. Die so gewonnenen Grenzen auf die Annihilations-Fl{\"u}sse schr{\"a}nken einige in der Literatur diskutierte und durch aussergew{\"o}hnlich große Annihilations-Fl{\"u}sse gekennzeichnete Szenarien stark ein.},
  subject      = {Gammastrahlung},
  language  = {en}
}
@phdthesis{Langejahn2022,
  author    = {Langejahn, Marcus},
  title     = {Hard X-ray Properties of Relativistically Beamed Jets from Radio- and Gamma-Ray-Bright Blazars},
  doi       = {10.25972/OPUS-28200},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-282009},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2022},
  abstract  = {In this work I characterize the hard X-ray properties of blazars, active galactic nuclei with highly beamed emission, which are notoriously hard to detect in this energy range. I employ pre-defined samples of beamed AGN: the radio-selected MOJAVE and TANAMI samples, as well as the most recent gamma-ray-selected Fermi/LAT 4LAC catalog. The hard X-ray data is extracted from the 105-month all-sky survey maps of the Swift/BAT (Burst Alert Telescope) in the energy band of 20 keV to 100 keV. A great majority of both the MOJAVE and TANAMI samples are significantly detected, with signal-to noise ratios of the sources often just below the X-ray catalog signal thresholds. All blazar sub-types (FSRQs, BL Lacs) and radio galaxies show characteristic ranges of X-ray flux, luminosity, and photon index. Their properties are correlated with the corresponding SED's shape / peak frequency. The LogN-LogS distributions of the samples show a scarcity of blazars in the middle and lower X-ray flux range, indicating differing evolutionary paths between radio and X-ray emission, which is also suggested by the corresponding luminosity functions. Compared to the radio samples, the 4LAC sources are on average significantly less bright in the BAT band since this range often coincides with the spectral gap region between the two big SED emission bumps. Also, the spectral shapes differ notably, especially for the sub-type of BL Lacs. Using the parameter space of X-ray and gamma-ray photon indices, 35 blazar candidate sources can be assigned to either the FSRQ or BL Lac type with high certainty. The reason why many blazars are weak in this energy band can be traced back to a number of factors: the selection bias of the initial sample, differential evolution of the X-rays and the wavelengths in which the sample is defined, and the limited sensitivity of the observing instruments.},
  subject      = {Aktiver galaktischer Kern},
  language  = {en}
}
@phdthesis{Berger2009,
  author    = {Berger, Karsten},
  title     = {Discovery and Characterization of the first Low-Peaked and Intermediate-Peaked BL Lacertae Objects in the Very High Energy Gamma-Ray Regime},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-37431},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2009},
  abstract  = {20 years after the discovery of the Crab Nebula as a source of very high energy gamma-rays, the number of sources newly discovered above 100 GeV using ground-based Cherenkov telescopes has considerably grown, at the time of writing of this thesis to a total of 81. The sources are of different types, including galactic sources such as supernova remnants, pulsars, binary systems, or so-far unidentified accelerators and extragalactic sources such as blazars and radio galaxies. The goal of this thesis work was to search for gamma-ray emission from a particular type of blazars previously undetected at very high gamma-ray energies, by using the MAGIC telescope. Those blazars previously detected were all of the same type, the so-called high-peaked BL Lacertae objects. The sources emit purely non-thermal emission, and exhibit a peak in their radio-to-X-ray spectral energy distribution at X-ray energies. The entire blazar population extends from these rare, low-luminosity BL Lacertae objects with peaks at X-ray energies to the much more numerous, high-luminosity infrared-peaked radio quasars. Indeed, the low-peaked sources dominate the source counts obtained from space-borne observations at gamma-ray energies up to 10 GeV. Their spectra observed at lower gamma-ray energies show power-law extensions to higher energies, although theoretical models suggest them to turn over at energies below 100 GeV. This opened the quest for MAGIC as the Cherenkov telescope with the currently lowest energy threshold. In the framework of this thesis, the search was focused on the prominent sources BL Lac, W Comae and S5 0716+714, respectively. Two of the sources were unambiguously discovered at very high energy gamma-rays with the MAGIC telescope, based on the analysis of a total of about 150 hours worth of data collected between 2005 and 2008. The analysis of this very large data set required novel techniques for treating the effects of twilight conditions on the data quality. This was successfully achieved and resulted in a vastly improved performance of the MAGIC telescope in monitoring campaigns. The detections of low-peaked and intermediate-peaked BL Lac objects are in line with theoretical expectations, but push the models based on electron shock acceleration and inverse-Compton cooling to their limits. The short variability time scales of the order of one day observed at very high energies show that the gamma-rays originate rather close to the putative supermassive black holes in the centers of blazars, corresponding to less than 1000 Schwarzschild radii when taking into account relativistic bulk motion.},
  subject      = {Aktiver galaktischer Kern},
  language  = {en}
}
@phdthesis{Glawion2014,
  author    = {Glawion, Dorit},
  title     = {Contemporaneous Multi-Wavelength Observations of the Gamma-Ray Emitting Active Galaxy IC 310 - New Clues on Particle Acceleration in Extragalactic Jets},
  url       = {http://nbn-resolving.de/urn:nbn:de:bvb:20-opus-113866},
  school      = {Universit{\"a}t W{\"u}rzburg},
  year      = {2014},
  abstract  = {In this thesis, the broad band emission, especially in the gamma-ray and radio band, of the active galaxy IC 310 located in the Perseus cluster of galaxies was investigated. The main experimental methods were Cherenkov astronomy using the MAGIC telescopes and high resolution very long baseline interferometry (VLBI) at radio frequencies (MOJAVE, EVN). Additionally, data of the object in different energy bands were studied and a multi-wavelength campaign has been organized and conducted. During the campaign, an exceptional bright gamma-ray flare at TeV energies was found with the MAGIC telescopes. The results were compared to theoretical acceleration and emission models for explaining the high energy radiation of active galactic nuclei. Many open questions regarding the particle acceleration to very high energies in the jets of active galactic nuclei, the particle content of the jets, or how the jets are launched, were addressed in this thesis by investigating the variability of IC 310 in the very high energy band. It is argued that IC310 was originally mis-classified as a head-tail radio galaxy. Instead, it shows a variability behavior in the radio, X-ray, and gamma-ray band similar to the one found for blazars. These are active galactic nuclei that are characterized by flux variability in all observed energy bands and at all observed time scales. They are viewed at a small angle between the jet axis and the line-of-sight. Thus, strong relativistic beaming influences the variability properties of blazars. Observations of IC 310 with the European VLBI Network helped to find limits for the angle between the jet axis and the line-of-sight, namely 10 deg - 20 deg. This places IC 310 at the borderline between radio galaxies (larger angles) and blazars (smaller angles). During the gamma-ray outburst detected at the beginning of the multi-wavelength campaign, flux variability as short as minutes was measured. The spectrum during the flare can be described by a simple power-law function over two orders of magnitude in energy up to ~10 TeV. Compared to previous observations, no significant variability of the spectral shape was found. Together with the constraint on the viewing angle, this challenges the currently accepted models for particle acceleration at shock waves in the jets. Alternative models, such as stars moving through the jets, mini-jets in the jet caused, e.g., by reconnection events, or gap acceleration in a pulsar-like magnetosphere around the black hole were investigated. It was found that only the latter can explain all observational findings, which at least suggests that it could even be worthwhile to reconsider published investigations of AGN with this new knowledge in mind. The first multi-wavelength campaign was successfully been conducted in 2012/2013, including ground-based as well as space-based telescopes in the radio, optical, ultraviolet, X-ray, and gamma-ray energy range. No pronounced variability was found after the TeV flare in any energy band. The X-ray data showed a slightly harder spectrum when the emission was brighter. The long-term radio light curve indicated a flickering flux variability, but no strong hint for a new jet component was found from VLBI images of the radio jet. In any case, further analysis of the existing multi-wavelength data as well as complimentary measurements could provide further exciting insights, e.g., about the broad band spectral energy distribution. Overall, it can be stated that IC 310 is a key object for research of active galactic nuclei in the high-energy band due to its proximity and its peculiar properties regarding flux variability and spectral behavior. Such objects are ideally suited for studying particle acceleration, jet formation, and other physical effects and models which are far from being fully understood.},
  subject      = {Aktiver galaktischer Kern},
  language  = {en}
}