29,732 research outputs found
Seasonal Flight Patterns of Miridae (Hemiptera) in a Southern Illinois Black Walnut Plantation
The seasonal flight patterns of 92 species of Miridae collected in window traps in a southern Illinois black walnut plantation are compared with similar data from a North Carolina black walnut plantation. Flying height distributions and seasonal flight activities of Amblytylus nasutus, Deraeocoris nebulosus, Leptopterna dolabrata, Lopidea heidemanni, Lygus lineolaris, and Plagiognathus politus are considered in detail. Six species are newly recorded for Illinois
Landform identification: Lunar radar images
Three sets of polarized radar-echo images of the Moon were examined to establish the relation between radar resolution and landform-identification resolution. After comparison with lunar maps and photographs, real and apparent landforms on the radar images were grouped into one of seven classes. Results show strong relations between radar resolution and diameter or relief of landforms that are clearly identified and those that would probably be correctly identified (class 1 and class 2). Landforms are not detected (class 5) at all diameters and reliefs, but the percentage of undetected landforms decreases with increasing mean diameter and mean relief. Landforms are simply detected (class 4) at most mean diameters and reliefs. Ambiguous arrays (class 6) portrayed by the radar constitute up to about 16, 22, and 15% of the landforms at various diameters and relief values for the 3.8 cm, 70 cm high resolution, and 70 cm low resolution images, respectively. Only a few percent of the landforms portrayed by the radar images at various diameters and relief values are fictitious (class 7)
The Origin of the Spatial Distribution of X-ray luminous AGN in Massive Galaxy Clusters
We study the spatial distribution of a 95% complete sample of 508 X-ray point
sources (XPS) detected in the 0.5-2.0 keV band in Chandra ACIS-I observations
of 51 massive galaxy clusters found in the MACS survey. Covering the redshift
range z=0.3-0.7, our cluster sample is statistically complete and comprises all
MACS clusters with X-ray luminosities in excess of 4.5 x 10^44 erg/s (0.1-2.4
keV, h_0=0.7, LCDM). Also studied are 20 control fields that do not contain
clusters. We find the XPS surface density, computed in the cluster restframe,
to exhibit a pronounced excess within 3.5 Mpc of the cluster centers. The
excess, believed to be caused by AGN in the cluster, is significant at the 8.0
sigma confidence level compared to the XPS density observed at the field edges.
No significant central excess is found in the control fields. To investigate
the physical origin of the AGN excess, we study the radial AGN density profile
for a subset of 24 virialized clusters. We find a pronounced central spike
(r<0.5 Mpc), followed by a depletion region at about 1.5 Mpc, and a broad
secondary excess centered at approximately the virial radius of the host
clusters (~2.5 Mpc). We present evidence that the central AGN excess reflects
increased nuclear activity triggered by close encounters between infalling
galaxies and the giant cD-type elliptical occupying the very cluster center. By
contrast, the secondary excess at the cluster-field interface is likely due to
black holes being fueled by galaxy mergers. In-depth spectroscopic and
photometric follow-up observations of the optical counterparts of the XPS in a
subset of our sample are being conducted to confirm this picture.Comment: ApJ Letters, accepted (4 pages, 3 figures, uses emulateapj
Home Appreciation Participation Notes: A Solution to Housing Affordability and the Current Mortgage Crisis
This paper introduces Home Appreciation Participation Notes (HAPNs), an innovative new housing finance tool. Housing is a commodity providing two distinct utilities: shelter and investment. Traditionally, buyers have had to purchase both elements in tandom. HAPNs allow buyers to purchase these elements individually. Thus, buyers can focus on purchasing housing units that best fit their shelter needs, investing in housing appreciation to whatever extent is appropriate for the needs of their investment portfolio. HAPNs are different from previous financing tools in three key ways: there is no payment burden until ownership of the home is transferred, the risk of housing price declines is shifted to investors, and the final payoff is indexed to the appreciation rates of local housing prices. With these three features, HAPNs considerably improve the affordability of homeownership while reducing the risk of default and avoiding the moral hazard associated with shared appreciation instruments.
Spectroscopic Binary Mass Determination using Relativity
High-precision radial-velocity techniques, which enabled the detection of
extrasolar planets are now sensitive to relativistic effects in the data of
spectroscopic binary stars (SBs). We show how these effects can be used to
derive the absolute masses of the components of eclipsing single-lined SBs and
double-lined SBs from Doppler measurements alone. High-precision stellar
spectroscopy can thus substantially increase the number of measured stellar
masses, thereby improving the mass-radius and mass-luminosity calibrations.Comment: 10 pages, 1 figure, accepted for publication by the Astrophysical
Journal Letter
The Solar Neighborhood VIII: Discovery of New High Proper Motion Nearby Stars Using the SuperCOSMOS Sky Survey
Five new objects with proper motions between 1.0 arcsec/yr and 2.6 arcsec/yr
have been discovered via a new RECONS search for high proper motion stars
utilizing the SuperCOSMOS Sky Survey. The first portion of the search,
discussed here, is centered on the south celestial pole and covers declinations
-90 degrees to -57.5 degrees.
Photographic photometry from SuperCOSMOS and JHKs near-infrared photometry
from 2MASS for stars nearer than 10 pc are combined to provide a suite of new
M_Ks-color relations useful for estimating distances to main sequence stars.
These relations are then used to derive distances to the new proper motion
objects as well as previously known stars with mu >= 1.0 arcsec/yr (many of
which have no trigonometric parallaxes) recovered during this phase of the
survey.
Four of the five new stars have red dwarf colors, while one is a nearby white
dwarf. Two of the red dwarfs are likely to be within the RECONS 10 pc sample,
and the white dwarf probably lies between 15 and 25 pc. Among the 23 known
stars recovered during the search, there are three additional candidates for
the RECONS sample that have no trigonometric parallaxes.Comment: 17 pages, 5 figures; accepted for publication in Astronomy Journa
Spot activity of the RS CVn star {\sigma} Geminorum
We model the photometry of RS CVn star Geminorum to obtain new
information on the changes of the surface starspot distribution, i.e., activity
cycles, differential rotation and active longitudes. We use the previously
published Continuous Periods Search-method (CPS) to analyse V-band differential
photometry obtained between the years 1987 and 2010 with the T3 0.4 m Automated
Telescope at the Fairborn Observatory. The CPS-method divides data into short
subsets and then models the light curves with Fourier-models of variable orders
and provides estimates of the mean magnitude, amplitude, period and light curve
minima. These light curve parameters are then analysed for signs of activity
cycles, differential rotation and active longitudes. We confirm the presence of
two previously found stable active longitudes, synchronised with the orbital
period d and find eight events where the active longitudes
are disrupted. The epochs of the primary light curve minima rotate with a
shorter period d than the orbital motion. If the
variations in the photometric rotation period were to be caused by differential
rotation, this would give a differential rotation coefficient of . The presence of two slightly different periods of active regions may
indicate a superposition of two dynamo modes, one stationary in the orbital
frame and the other one propagating in the azimuthal direction. Our estimate of
the differential rotation is much higher than previous results. However,
simulations show that this can be caused by insufficient sampling in our data.Comment: 10 pages, 6 figures. Submitted to A&
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