Microlensing Analysis for the gravitational lens systems SDSS0924+0219,
  Q1355-2257, and SDSS1029+2623
  We use spectroscopic observations of the gravitationally lensed systems
SDSS0924+0219(BC), Q1355-2257(AB), and SDSS1029+2623(BC) to analyze
microlensing and dust extinction in the observed components. We detect
chromatic microlensing effects in the continuum and microlensing in the broad
emission line profiles of the systems SDSS0924+0219(BC), and Q1355-2257(AB).
Using magnification maps to simulate microlensing and modeling the emitting
region as a Gaussian intensity profile with size $r_s \propto \lambda ^p$, we
obtain the probability density functions for a logarithmic size prior at
$\lambda_{rest-frame}=3533$ {\AA}. In the case of SDSS0924+0219, we obtain:
$r_s = 4^{+3}_{-2}$ $\sqrt{M/M_{\odot}}$ light-days (at $1 \sigma$), which is
larger than the range of other estimates, and $p = 0.8 \pm 0.2$ (at $1
\sigma$), which is smaller than predicted by the thin disk theory, but still in
agreement with previous results. In the case of Q1355-2257 we obtain (at $1
\sigma$): $r_s = 3.6^{+3.0}_{-1.6}$ $\sqrt{M/M_{\odot}}$ light-days, which is
also larger than the theoretical prediction, and $p = 2.0 \pm 0.7$ that is in
agreement with the theory within errors. SDSS1029+2326 spectra show evidence of
extinction, probably produced by a galaxy in the vicinity of image C. Fitting
an extinction curve to the data we estimate $\Delta E \sim 0.2$ in agreement
with previous results. We found no evidence of microlensing for this system.
