374 research outputs found
Identification of the OGLE-2003-BLG-235/MOA-2003-BLG-53 Planetary Host Star
We present the results of HST observations of the host star for the first
definitive extrasolar planet detected by microlensing. The light curve model
for this event predicts that the lens star should be separated from the source
star by ~6mas at the time of the HST images. If the lens star is a late G, K or
early M dwarf, then it will be visible in the HST images as an additional
source of light that is blended with the source image. Unless the lens and
source have exactly the same colors, its presence will also be revealed by a
systematic shift between centroids of the source plus lens in different filter
bands. The HST data indicates both of these effects: the HST source that
matches the position of the source star is 0.21 magnitudes brighter in the
ACS/HRC-F814W filter than the microlensing model predicts, and there is an
offset of ~0.7mas between the centroid of this source in the F814W and F435W
filter bands. We conclude the planetary host star has been detected in these
HST images, and this identification of the lens star enables a complete
solution of the lens system. The lens parameters are determined with a Bayesian
analysis, averaging over uncertainties in the measured parameters, interstellar
extinction, and allowing for the possibility of a binary companion to the
source star. This yields a stellar mass of M_* = 0.63(+0.07/-0.09) M_solar and
a planet mass of M_p = 2.6 (+0.8/-0.6) M_Jup at an orbital separation of 4.3
(+2.5/-0.8) AU. Thus, the lens system resembles our own Solar System, with a
planet of ~3 Jupiter-masses in a Jupiter-like orbit around a star of two-thirds
of a Solar mass. These conclusions can be tested with future HST images, which
should reveal a broadening of the blended source-plus-lens point spread
function due to the relative lens-source proper motion.Comment: 11 pages, with 3 figures. to appear in ApJ Lett (Aug 20 issue
Robust synthesis of epoxy resin-filled microcapsules for application to self-healing materials
Mechanically and thermally robust microcapsules containing diglycidyl ether bisphenol A-based epoxy resin and a high-boiling-point organic solvent were synthesized in high yield using in situ polymerization of urea and formaldehyde in an oil-in-water emulsion. Microcapsules were characterized in terms of their size and size distribution, shell surface morphology and thermal resistance to the curing cycles of commercially used epoxy polymers. The size distribution of the capsules and characteristics such as shell thickness can be controlled by the specific parameters of microencapsulation, including concentrations of reagents, stirrer speed and sonication. Selected microcapsules, and separated core and shell materials, were analysed using thermogravimetric analysis and differential scanning calorimetry. It is demonstrated that capsules lose minimal 2.5 wt% at temperatures no higher than 120°C. These microcapsules can be applied to self-healing carbon fibre composite structural materials, with preliminary results showing promising performance
Optimization of an Air Film Cooled CFRP Panel with an Embedded Vascular Network
This paper summarizes research performed on thermodynamic simulation and design optimization of a composite panel cooled by an external cool film and an internal vascular network
A Second Method to Photometrically Align Multi-Site Microlensing Light Curves: Source Color in Planetary Event MOA-2007-BLG-192
At present, microlensing light curves from different telescopes and filters
are photometrically aligned by fitting them to a common model. We present a
second method based on photometry of common field stars. If two spectral
responses are similar (or the color of the source is known) then this technique
can resolve important ambiguities that frequently arise when predicting the
future course of the event, and that occasionally persist even when the event
is over. Or if the spectral responses are different, it can be used to derive
the color of the source when that is unknown. We present the essential elements
of this technique and apply it to the case of MOA-2007-BLG-192, an important
planetary event for which the system may be a terrestrial planet orbiting a
brown dwarf or very low mass star. The refined estimate of the source color
that we derive here, V-I=2.36 +- 0.03, will aid in making the estimate of the
lens mass more precise.Comment: 16 pages including 3 figures. Submitted to Ap
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