@article{Wambsganss2002,
  author    = {Wambsganß, Joachim},
  title     = {What gravitational microlensing can reveal about (the central parts of) AGNs},
  isbn      = {1-583-81135-4},
  year      = {2002},
  language  = {en}
}
@article{Wambsganss2002,
  author    = {Wambsganß, Joachim},
  title     = {Mimicking the most luminous objects with gravitational lensing},
  isbn      = {3-540-43769- x},
  year      = {2002},
  language  = {en}
}
@article{Wambsganss2002,
  author    = {Wambsganß, Joachim},
  title     = {The search for matter with gravitational lensing},
  year      = {2002},
  language  = {en}
}
@article{SchmidtKundicPenetal.2002,
  author    = {Schmidt, Robert W. and Kundic, T. and Pen, U.-L. and Wambsganß, Joachim and Bergeron, L. E. and Colley, W. and Corson, C. and Hastings, N. G. and Hoyes, T. and Long, D. C. and Loomis, K. A. and Malhotra, S. and Rhoads, J. E. and Stanek, K. Z.},
  title     = {Optical monitoring of the gravitationally lensed quasar Q2237+0305 from APO between June 1995 and January 1998},
  year      = {2002},
  abstract  = {We present a data set of images of the gravitationally lensed quasar Q2237+0305, that was obtained at the Apache Point Observatory (APO) between June 1995 and January 1998. Although the images were taken under variable, often poor seeing conditions and with coarse pixel sampling, photometry is possible for the two brighter quasar images A and B with the help of exact quasar image positions from HST observations. We obtain a light curve with 73 data points for each of the images A and B. There is evidence for a long (ga 100 day) brightness peak in image A in 1996 with an amplitude of about 0.4 to 0.5 mag (relative to 1995), which indicates that microlensing has been taking place in the lensing galaxy. Image B does not vary much over the course of the observation period. The long, smooth variation of the light curve is similar to the results from the OGLE monitoring of the system (Wozniak et al. cite{Wozniak00}). Based on observations obtained with the Apache Point Observatory 3.5-meter telescope, which is owned and operated by the Astrophysical Research Consortium.},
  language  = {en}
}
@article{SchechterWambsganss2002,
  author    = {Schechter, P. L. and Wambsganß, Joachim},
  title     = {Quasar microlensing at high magnification and the role of dark matter : enhanced fluctuations and suppressed saddle points},
  year      = {2002},
  abstract  = {Contrary to naive expectation, diluting the stellar component of the lensing galaxy in a highly magnified system with smoothly distributed ``dark'' matter increases rather than decreases the microlensing fluctuations caused by the remaining stars. For a bright pair of images straddling a critical curve, the saddle point (of the arrival time surface) is much more strongly affected than the associated minimum. With a mass ratio of smooth matter to microlensing matter of 4:1, a saddle point with a macromagnification of ;=9.5 will spend half of its time more than a magnitude fainter than predicted. The anomalous flux ratio observed for the close pair of images in MG 0414+0534 is a factor of 5 more likely than computed by Witt, Mao, \& Schechter, if the smooth matter fraction is as high as 93\%. The magnification probability histograms for macroimages exhibit a distinctly different structure that varies with the smooth matter content, providing a handle on the smooth matter fraction. Enhanced fluctuations can manifest themselves either in the temporal variations of a light curve or as flux ratio anomalies in a single epoch snapshot of a multiply imaged system. While the millilensing simulations of Metcalf \& Madau also give larger anomalies for saddle points than for minima, the effect appears to be less dramatic for extended subhalos than for point masses. Moreover, microlensing is distinguishable from millilensing because it will produce noticeable changes in the magnification on a timescale of a decade or less.},
  language  = {en}
}
@article{GilMerinoWisotzkiWambsganss2002,
  author    = {Gil-Merino, Rodrigo and Wisotzki, Lutz and Wambsganß, Joachim},
  title     = {The Double Quasar HE 1104-1805 : a case study for time delay determination with poorly sampled lightcurves},
  year      = {2002},
  abstract  = {We present a new determination of the time delay of the gravitational lens system HE 1104-1805 (``Double Hamburger'') based on a previously unpublished dataset. We argue that the previously published value of Delta tA-B=0.73 years was affected by a bias of the employed method. We determine a new value of Delta tA-B=0.85+/-0.05 years (2sigma confidence level), using six different techniques based on non interpolation methods in the time domain. The result demonstrates that even in the case of poorly sampled lightcurves, useful information can be obtained with regard to the time delay. The error estimates were calculated through Monte Carlo simulations. With two already existing models for the lens and using its recently determined redshift, we infer a range of values of the Hubble parameter: H0=48+/-4 km s-1 Mpc-1 (2sigma ) for a singular isothermal ellipsoid (SIE) and H0=62+/-4 km s-1 Mpc-1 (2sigma ) for a constant mass-to-light ratio plus shear model (M/L+gamma ). The possibly much larger errors due to systematic uncertainties in modeling the lens potential are not included in this error estimate.},
  language  = {en}
}
@article{deFilippisSchindlerCastilloMoralesetal.2002,
  author    = {de Filippis, E. and Schindler, Sabine and Castillo-Morales, A. and Schwope, A. D and Wambsganß, Joachim},
  title     = {Discovery of holes in the core of the distant galaxy cluster RBS797 in a CHANDRA observation},
  isbn      = {1-583-81108-7},
  year      = {2002},
  language  = {en}
}