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- ItemGravitational lensing in astronomy(Berlin : Springer, 1998) Wambsganss, J.Deflection of light by gravity was predicted by General Relativity and observationally confirmed in 1919. In the following decades, various aspects of the gravitational lens effect were explored theoretically. Among them were: the possibility of multiple or ring-like images of background sources, the use of lensing as a gravitational telescope on very faint and distant objects, and the possibility of determining Hubble's constant with lensing. It is only relatively recently, (after the discovery of the first doubly imaged quasar in 1979), that gravitational lensing has became an observational science. Today lensing is a booming part of astrophysics. In addition to multiply-imaged quasars, a number of other aspects of lensing have been discovered: For example, giant luminous arcs, quasar microlensing, Einstein rings, galactic microlensing events, arclets, and weak gravitational lensing. At present, literally hundreds of individual gravitational lens phenomena are known. Although still in its childhood, lensing has established itself as a very useful astrophysical tool with some remarkable successes. It has contributed significant new results in areas as different as the cosmological distance scale, the large scale matter distribution in the universe, mass and mass distribution of galaxy clusters, the physics of quasars, dark matter in galaxy halos, and galaxy structure. Looking at these successes in the recent past we predict an even more luminous future for gravitational lensing.
- ItemMagnetic holes in the solar wind between 0.3 AU and 17 AU(Göttingen : Copernicus GmbH, 2000) Sperveslage, K.; Neubauer, F.M.; Baumgärtel, K.; Ness, N.F.Magnetic holes (MHs) are depressions of the magnetic field magnitude. Turner et al. (1977) identified the first MHs in the solar wind and determined an occurrence rate of 1.5 MHs/d. Winterhalter et al. (1994) developed an automatic identification criterion to search for MHs in Ulysses data in the solar wind between 1 AU and 5.4 AU. We adopt their criterion to expand the search to the heliocentric distances down to 0.3 AU using data from Helios 1 and 2 and up to 17 AU using data from Voyager 2. We relate our observations to two theoretical approaches which describe the so-called linear MHs in which the magnetic vector varies in magnitude rather than direction. Therefore we focus on such linear MHs with a directional change less than 10°. With our observations of about 850 MHs we present the following results: Approximately 30% of all the identified MHs are linear. The maximum angle between the initial magnetic field vector and any vector inside the MH is 20°in average and shows a weak relation to the depth of the MHs. The angle between the initial magnetic field and the minimum variance direction of those structures is large and very probably close to 90°. The MHs are placed in a high β environment even though the average solar wind shows a smaller β. The widths decrease from about 50 proton inertial length in a region between 0.3 AU and 0.4 AU heliocentric distance to about 15 proton inertial length at distances larger than 10 AU. This quantity is correlated with the β of the MH environments with respect to the heliocentric distance. There is a clear preference for the occurrence of depressions instead of compressions. We discuss these results with regard to the main theories of MHs, the mirror instability and the alternative soliton approach. Although our observational results are more consistent with the soliton theory we favor a combination of both. MHs might be the remnants of initial mirror mode structures which can be described as solitons during the main part of their lifetime.
- ItemMetagalaktische Röntgenhintergrund : Schlussbericht zum Vorhaben(Potsdam : Leibniz-Institut für Astrophysik, 2002) AIP[no abstract available]
- ItemAutomatische Mustererkennunng dispergierter Interferenzbilder : Schlussbericht zur Studie(Potsdam : Leibniz-Institut für Astrophysik, 2001) Scholz, Ralf-Dieter; Schilbach, E.[no abstract available]
- ItemDie Verarbeitung des Rohdatenflusses eines Weltrauminterferometers : Schlussbericht zur Studie ; Zeitraum: 1.3.2000 - 31.12.2001(Potsdam : Leibniz-Institut für Astrophysik, 2002) Hirte, Sonja; Scholz, Ralf-Dieter; Schilbach, E.[no abstract available]
- ItemTomographische Untersuchungen magnetischer CVs mit HST und ROSAT : Schlussbericht zum Vorhaben(Potsdam : Leibniz-Institut für Astrophysik, 2002) Schwope, Axel[no abstract available]
- ItemMitwirkung bei Aufbau und Betrieb des XMM Survey Scientist Center : Schlußbericht zum DLR Projekt 50 OX 9801 3(Potsdam : Leibniz-Institut für Astrophysik, 2001) Brunner, Hermann; Schwope, Axel[no abstract available]
- ItemVorhaben: Untersuchung von Teilchenbeschleunigungsmechanismen an Stoßwellen mittels der Daten des EPAC-Instruments an Bord des ULYSSES-Satelliten(Potsdam : Leibniz-Institut für Astrophysik, 2000) Mann, Gottfried[no abstract available]
- ItemVorhaben: KORONAS/SORS-Satellitenprojekt (Radiospektrographie) : Schlussbericht(Potsdam : Leibniz-Institut für Astrophysik, 2001) Mann, G.[no abstract available]
- ItemDeutsche Beteiligung am Röntgenexperiment SODART : Abschlußbericht für den Zeitraum: 1997 - 2000(Potsdam : Leibniz-Institut für Astrophysik, 2001) Wiebicke, Hans-Joachim[no abstract available]