77 research outputs found
Book Reviews
Reviews of the following books: Chansonetta: The Life and Photographs of Chansonetta Stanley Emmons, 1859-1937 by Marius B. Peladeau; Raymond Then and Now by Ernest H. Knight; The Jesuit Heritage of New England by Vincent A. Lapomarda; The Landing: A Remembrance of Her People and Shipyards by Thomas W. Murphy; A History of the Town of Hancock, 1828-1979 prepared by the Sesquicentennial Committee of the Town of Hancoc
Population and Size Distribution of Small Jovian Trojan Asteroids
We present a study of Jovian Trojan objects detected serendipitously during
the course of a sky survey conducted at the University of Hawaii 2.2-meter
telescope. We used a 8192 x 8192 pixel charge-coupled device (CCD) mosaic to
observe 20 deg^2 at locations spread over the L4 Lagrangian swarm and reached a
limiting magnitude V = 22.5 mag (50% of maximum detection efficiency).
Ninety-three Jovian Trojans were detected with radii 2 - 20 km (assumed albedo
0.04). Their differential magnitude distribution has a slope of 0.40 +/- 0.05
corresponding to a power law size distribution index 3.0 +/- 0.3 (1-sigma). The
total number of L4 Trojans with radii > 1 km is of order 1.6 x 10^5 and their
combined mass (dominated by the largest objects) is ~ 10^{-4} M_{Earth}. The
bias-corrected mean inclination is 13.7 +/- 0.5 deg. We also discuss the size
and spatial distribution of the L4 swarm.Comment: 21 pages, 11 figures. AJ, in pres
Densities of Solar System Objects from their Rotational Lightcurves
We present models of the shapes of four Kuiper belt objects (KBOs) and Jovian
Trojan (624) Hektor as ellipsoidal figures of equilibrium and Roche binaries.
Our simulations select those figures of equilibrium whose lightcurves best
match the measured rotational data. The best fit shapes, combined with the
knowledge of the spin period of the objects provide estimates of the bulk
densities of these objects. We find that the lightcurves of KBOs (20000) Varuna
and 2003 EL61 are well matched by Jacobi triaxial ellipsoid models with bulk
densities 992 (-15,+86) kg/m^3 and 2551 (-10,+115) kg/m^3, respectively. The
lightcurves of (624) Hektor and KBO 2001 QG298 are well-described by Roche
contact binary models with densities 2480 (-80,+292) kg/m^3 and 590 (-47,+143)
kg/m^3, respectively. The nature of 2000 GN171 remains unclear: Roche binary
and Jacobi ellipsoid fits to this KBO are equivalent, but predict different
densities, ~2000 kg/m^3 and ~650 kg/m^3, respectively. Our density estimates
suggest a trend of increasing density with size.Comment: 13 pages (emulateapj), 20 figures, AJ, accepted 2006/12/
Properties of the Trans-Neptunian Belt: Statistics From the CFHT Survey
We present the results of a wide-field survey designed to measure the size,
inclination, and radial distributions of Kuiper Belt Objects (KBOs). The survey
found 86 KBOs in 73 square degrees observed to limiting red magnitude 23.7
using the Canada-France-Hawaii Telescope and the 12k x 8k CCD Mosaic camera.
For the first time, both ecliptic and off-ecliptic fields were examined to more
accurately constrain the inclination distribution of the KBOs. The survey data
were processed using an automatic moving object detection algorithm, allowing a
careful characterization of the biases involved. In this work, we quantify
fundamental parameters of the Classical KBOs (CKBOs), the most numerous objects
found in our sample, using the new data and a maximum likelihood simulation.
Deriving results from our best-fit model, we find that the size distribution
follows a differential power law with exponent q = 4.0 (+0.6)(-0.5) (1 sigma,
or 68.27% confidence). In addition, the CKBOs inhabit a very thick disk
consistent with a Gaussian distribution of inclinations with a Half-Width of
i(1/2) = 20 (+6)(-4) deg (1 sigma). We estimate that there are N = 3.8
(+2.0)(-1.5) x 10^4 (1 sigma) CKBOs larger than 100 km in diameter. We also
find compelling evidence for an outer edge to the CKBOs at heliocentric
distance R = 50 AU.Comment: To be published in the Astronomical Journal, July 200
A Wide-Field CCD Survey for Centaurs and Kuiper Belt Objects
A modified Baker-Nunn camera was used to conduct a wide-field survey of 1428
square degrees of sky near the ecliptic in search of bright Kuiper Belt objects
and Centaurs. This area is an order of magnitude larger than any previously
published CCD survey for Centaurs and Kuiper Belt Objects. No new objects
brighter than red magnitude m=18.8 and moving at a rate 1"/hr to 20"/hr were
discovered, although one previously discovered Centaur 1997 CU26 Chariklo was
serendipitously detected. The parameters of the survey were characterized using
both visual and automated techniques. From this survey the empirical projected
surface density of Centaurs was found to be SigmaCentaur(m<18.8)=7.8(+16.0
-6.6)x10^-4 per square degree and we found a projected surface density 3sigma
upper confidence limit for Kuiper Belt objects of SigmaKBO(m< 18.8)<4.1x10^-3
per square degree. We discuss the current state of the cumulative luminosity
functions of both Centaurs and Kuiper Belt objects. Through a Monte Carlo
simulation we show that the size distribution of Centaurs is consistent with a
q=4 differential power law, similar to the size distribution of the parent
Kuiper Belt Objects. The Centaur population is of order 10^7 (radius > 1 km)
assuming a geometric albedo of 0.04. About 100 Centaurs are larger than 50 km
in radius, of which only 4 are presently known. The current total mass of the
Centaurs is 10^-4 Earth Masses. No dust clouds were detected resulting from
Kuiper Belt object collisions, placing a 3sigma upper limit <600 collisionally
produced clouds of m<18.8 per year.Comment: 13 pages, 5 figures, Accepted for Publication in A
Discovery of Reflection Nebulosity Around Five Vega-like Stars
Coronagraphic optical observations of six Vega-like stars reveal reflection
nebulosities, five of which were previously unknown. The nebulosities
illuminated by HD 4881, HD 23362, HD 23680, HD 26676, and HD 49662 resemble
that of the Pleiades, indicating an interstellar origin for dust grains. The
reflection nebulosity around HD 123160 has a double-arm morphology, but no
disk-like feature is seen as close as 2.5 arcsec from the star in K-band
adaptive optics data. We demonstrate that uniform density dust clouds
surrounding HD 23362, HD 23680 and HD 123160 can account for the observed
12-100 micron spectral energy distributions. For HD 4881, HD 26676, and HD
49662 an additional emission source, such as from a circumstellar disk or
non-equilibrium grain heating, is required to fit the 12-25 micron data. These
results indicate that in some cases, particularly for Vega-like stars located
beyond the Local Bubble (>100 pc), the dust responsible for excess thermal
emission may originate from the interstellar medium rather than from a
planetary debris system.Comment: The Astrophysical Journal, in press for March, 2002 (32 pages, 13
figures
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