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Abstract

For two years, the Gaia satellite has been scanning the sky to obtain an unmatched positional accuracy of stars and a variety of data. In this thesis, we investigate two different kinds of questions with respect to Gaia. In our first research focus we explore Gaia data that is suitable to learn more about the structure of quasars. For this, we simulate low- and high-resolution quasar spectra as they would be generated by Gaia’s blue and red photometers and the radial velocity spectrograph (RVS). Furthermore, we investigate bright SDSS quasars with broad emission lines (BELs) redshifted into the wavelength range of Gaia’s RVS. We find out that quasar low-resolution spectra enable the study of equivalent widths, continuum variability, and the so called Baldwin effect. For about seventy bright quasars, Gaia will obtain high-resolution spectra from which BEL variability can be studied using the line profile. From our analysis we conclude that Gaia provides a large amount of data which we can use for a better understanding of variability in quasar spectra. In our second research focus, we improve the prediction of astrometric microlensing events with Gaia data. When we predict such events precisely, we could plan to observe the corresponding photometric amplification simultaneously. To improve our published search for microlensing events (Proft et al. 2011), we increase the search radius around a potential lensing star and check once more the proper motion of the lenses. Due to the revision of our program, we find fifty new potential microlensing events. Six have estimated positional changes that could lead to a detectable Gaia signal. Currently, the errors of our calculated quantities are too large to follow up the events in real time. We will monitor whether our microlensing predictions are correct and with future Gaia data we can make more precise predictions in order to develop observational campaigns.