@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{WisotzkiSchechterBradtetal.2002,
  author    = {Wisotzki, Lutz and Schechter, P. L. and Bradt, H. V. and Heinm{\"u}ller, Janine and Reimers, Dieter},
  title     = {HE 0435-1223 : a wide separation quadruple QSO and gravitational lens},
  year      = {2002},
  abstract  = {We report the discovery of a new gravitationally lensed QSO, at a redshift z = 1.689, with four QSO components in a cross-shaped arrangement around a bright galaxy. The maximum separation between images is 2farcs 6, enabling a reliable decomposition of the system. Three of the QSO components have g =~ 19.6, while component A is about 0.6 mag brighter. The four components have nearly identical colours, suggesting little if any dust extinction in the foreground galaxy. The lensing galaxy is prominent in the i band, weaker in r and not detected in g. Its spatial profile is that of an elliptical galaxy with a scale length of ~ 12 kpc. Combining the measured colours and a mass model for the lens, we estimate a most likely redshift range of 0.3 < z < 0.4. Predicted time delays between the components are la 10 days. The QSO shows evidence for variability, with total g band magnitudes of 17.89 and 17.71 for two epochs separated by ~ 2 months. However, the relative fluxes of the components did not change, indicating that the variations are intrinsic to the QSO rather than induced by microlensing. Based in part on observations obtained with the Baade 6.5-m telescope of the Magellan Consortium. Also based in part on observations collected at the European Southern Observatory, La Silla, Chile.},
  language  = {en}
}