20,972 research outputs found
Microlensing of the Lensed Quasar SDSS0924+0219
We analyze V, I and H band HST images and two seasons of R-band monitoring
data for the gravitationally lensed quasar SDSS0924+0219. We clearly see that
image 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 because
microlensing has provided a natural coronograph that suppresses the flux of the
quasar 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. Monte
Carlo models of the microlensing variability provide estimates of the mean
stellar mass in the lens galaxy (0.02 Msun < M < 1.0 Msun), the accretion disk
size (the disk temperature is 5 x 10^4 K at 3.0 x 10^14 cm < rs < 1.4 x 10^15
cm), 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 mass
estimate 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 the
best-fitting light curve models into the future, we expect the the flux of
images A and B to remain relatively stable and images C and D to brighten. In
particular, we estimate that image D has a roughly 12% probability of
brightening by a factor of two during the next year and a 45% probability of
brightening 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
Rings in the Solar System: a short review
Rings are ubiquitous around giant planets in our Solar System. They evolve
jointly with the nearby satellite system. They could form either during the
giant planet formation process or much later, as a result of large scale
dynamical instabilities either in the local satellite system, or at the
planetary scale. We review here the main characteristics of rings in our solar
system, and discuss their main evolution processes and possible origin. We also
discuss the recent discovery of rings around small bodies.Comment: Accepted for the Handbook of Exoplanet
Gravitational Lenses as High-Resolution Telescopes
The inner regions of active galaxies host the most extreme and energetic
phenomena in the universe including, relativistic jets, supermassive black hole
binaries, and recoiling supermassive black holes. However, many of these
sources cannot be resolved with direct observations. I review how strong
gravitational lensing can be used to elucidate the structures of these sources
from radio frequencies up to very high energy gamma rays. The deep
gravitational potentials surrounding galaxies act as natural gravitational
lenses. These gravitational lenses split background sources into multiple
images, each with a gravitationally-induced time delay. These time delays and
positions of lensed images depend on the source location, and thus, can be used
to infer the spatial origins of the emission. For example, using
gravitationally-induced time delays improves angular resolution of modern
gamma-ray instruments by six orders of magnitude, and provides evidence that
gamma-ray outbursts can be produced at even thousands of light years from a
supermassive black hole, and that the compact radio emission does not always
trace the position of the supermassive black hole. These findings provide
unique physical information about the central structure of active galaxies,
force us to revise our models of operating particle acceleration mechanisms,
and challenge our assumptions about the origin of compact radio emission.
Future surveys, including LSST, SKA, and Euclid, will provide observations for
hundreds of thousands of gravitationally lensed sources, which will allow us to
apply strong gravitational lensing to study the multi-wavelength structure for
large ensembles of sources. This large ensemble of gravitationally lensed
active galaxies will allow us to elucidate the physical origins of
multi-wavelength emissions, their connections to supermassive black holes, and
their cosmic evolution.Comment: Invited (Accepted) review for Physics Report
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