Microlensing of the Lensed Quasar SDSS 0924+0219

We analyze V, I and H band HST images and two seasons of R-band monitoringdata for the gravitationally lensed quasar SDSS0924+0219. We clearly see thatimage D is a point-source image of the quasar at the center of its host galaxy.We can easily track the host galaxy of the quasar close to image D becausemicrolensing has provided a natural coronograph that suppresses the flux of thequasar image by roughly an order of magnitude. We observe low amplitude,uncorrelated variability between the four quasar images due to microlensing,but no correlated variations that could be used to measure a time delay. MonteCarlo models of the microlensing variability provide estimates of the meanstellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disksize (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15cm), and the black hole mass (2.0 x 10^7 Msun < MBH \eta_{0.1}^{-1/2}(L/LE)^{1/2} < 3.3 x 10^8 Msun), all at 68% confidence. The black hole massestimate based on microlensing is consistent with an estimate of MBH = 7.3 +-2.4 x 10^7 Msun from the MgII emission line width. If we extrapolate thebest-fitting light curve models into the future, we expect the the flux ofimages A and B to remain relatively stable and images C and D to brighten. Inparticular, we estimate that image D has a roughly 12% probability ofbrightening by a factor of two during the next year and a 45% probability ofbrightening by an order of magnitude over the next decade.Comment: v.2 incorporates referee's comments and corrects two errors in the original manuscript. 28 pages, 10 figures, published in Ap