3,275 research outputs found
Probing ~100 AU Intergalactic MgII Absorbing "Cloudlets" with Quasar Microlensing
Intergalactic MgII absorbers are known to have structures down to scales ~
10^{2.5} pc, and there are now indications that they may be fragmented on
scales <~ 10^{-2.5} pc (Hao et al., astro-ph/0612409). When a lensed quasar is
microlensed, the micro-images of the quasar experience creation, destruction,
distortion, and drastic astrometric changes during caustic-crossing. I show
that quasar microlensing can effectively probe MgII and other absorption
"cloudlets" with sizes ~ 10^{-4.0} - 10^{-2.0} pc by inducing significant
spectral variability on the timescales of months to years. With numerical
simulations, I demonstrate the feasibility of applying this method to
Q2237+0305, and I show that high-resolution spectra of this quasar in the near
future would provide a clear test of the existence of such metal-line
absorption "cloudlets" along the quasar sight line.Comment: 13 pages, 2 figures, ApJ, submitted; for PDF file with high-res
figures, see http://www.astronomy.ohio-state.edu/~dong/mg2/mg2.pd
Microlensing of Lensed Supernovae
Given the number of recently discovered galaxy-galaxy lens systems, we
anticipate that a gravitationally lensed supernova will be observed within the
next few years. We explore the possibility that stars in the lens galaxy will
produce observable microlensing fluctuations in lensed supernova light curves.
For typical parameters, we predict that ~70% of lensed SNe will show
microlensing fluctuations > 0.5 mag, while ~25% will have fluctuations > 1 mag.
Thus microlensing of lensed supernova will be both ubiquitous and observable.
Additionally, we show that microlensing fluctuations will complicate
measurements of time delays from multiply imaged supernovae: time delays
accurate to better than a few days will be difficult to obtain. We also
consider prospects for extracting the lens galaxy's stellar mass fraction and
mass function from microlensing fluctuations via a new statistical measure, the
time-weighted light curve derivative.Comment: 13 pages, emulateapj format; accepted in ApJ; expanded discussion of
time delay uncertaintie
How can we test seesaw experimentally?
The seesaw mechanism for the small neutrino mass has been a popular paradigm,
yet it has been believed that there is no way to test it experimentally. We
present a conceivable outcome from future experiments that would convince us of
the seesaw mechanism. It would involve a variety of data from LHC, ILC,
cosmology, underground, and low-energy flavor violation experiments to
establish the case.Comment: 5 pages, 4 figure
A method to measure a relative transverse velocity of source-lens-observer system using gravitational lensing of gravitational waves
Gravitational waves propagate along null geodesics like light rays in the
geometrical optics approximation, and they may have a chance to suffer from
gravitational lensing by intervening objects, as is the case for
electromagnetic waves. Long wavelength of gravitational waves and compactness
of possible sources may enable us to extract information in the interference
among the lensed images. We point out that the interference term contains
information of relative transverse velocity of the source-lens-observer system,
which may be obtained by possible future space-borne gravitational wave
detectors such as BBO/DECIGO.Comment: 27 pages, 9 figures. Accepted for publication in Physical Review
Talented and gifted programs in the middle school : critical components
As middle school educators and teachers of the gifted and talented continue to debate issues such as equity vs. excellence, homogeneous vs. heterogeneous grouping, and cognitive vs. affective education, the needs of gifted and talented middle school students in the general education classroom appear to be ignored. This paper reviewed current literature relating to the needs of gifted and talented pre-adolescents in the middle school setting in order to determine what were the critical components necessary for meeting their unique needs in the general education classroom. From the reviewed literature, critical components identified include content differentiation, teaching strategies, grouping for instruction, and addressing the social-emotional needs of acceptance and self-esteem. The paper closes with a discussion of conclusions which may be drawn from the literature and recommendations for further study
Microlensing Detections of Moons of Exoplanets
We investigate the characteristic of microlensing signals of Earth-like moons
orbiting ice-giant planets. From this, we find that non-negligible satellite
signals occur when the planet-moon separation is similar to or greater than the
Einstein radius of the planet. We find that the satellite signal does not
diminish with the increase of the planet-moon separation beyond the Einstein
radius of the planet unlike the planetary signal which vanishes when the planet
is located well beyond the Einstein radius of the star. We also find that the
satellite signal tends to have the same sign as that of the planetary signal.
These tendencies are caused by the lensing effect of the star on the moon in
addition to the effect of the planet. We determine the range of satellite
separations where the microlensing technique is optimized for the detections of
moons. By setting an upper limit as the angle-average of the projected Hill
radius and a lower limit as the half of the Einstein radius of the planet, we
find that the microlensing method would be sensitive to moons with projected
separations from the planet of for a Jupiter-mass planet, for a Saturn-mass planet, and for a Uranus-mass planet. We compare the
characteristics of the moons to be detected by the microlensing and transit
techniquesComment: 6pages, 6 figure
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