4,394 research outputs found
The History of the Mysterious Eclipses of KH 15D: Asiago Observatory, 1967-1982
We are gathering archival observations to determine the photometric history
of the unique and unexplained eclipses of the pre-main-sequence star KH 15D.
Here we present a light curve from 1967-1982, based on photographic plates from
Asiago Observatory. During this time, the system alternated periodically
between bright and faint states, as observed today. However, the bright state
was 0.9 mag brighter than the modern value, and the fractional variation
between bright and faint states (Delta I = 0.7 mag) was smaller than observed
today (3.5 mag). A possible explanation for these findings is that the system
contains a second star that was previously blended with the eclipsing star, but
is now completely obscured.Comment: Accepted to AJ. 24 pages, 10 figures, 2 tables. v2: Phase error
corrected in figures 8 and 1
The effects of experimental uncertainty in parameterizing air-sea gas exchange using tracer experiment data
It is not practical to measure air-sea gas fluxes in the open ocean for all conditions and areas of interest. Therefore, in many cases fluxes are estimated from measurements of air-phase and water-phase gas concentrations, a measured environmental forcing function such as wind speed, and a parameterization of the air-sea transfer velocity in terms of the environmental forcing function. One problem with this approach is that when direct measurements of the transfer velocity are plotted versus the most commonly used forcing function, wind speed, there is considerable scatter, leading to a relatively large uncertainty in the flux. Because it is known that multiple processes can affect gas transfer, it is commonly assumed that this scatter is caused by single-forcing function parameterizations being incomplete in a physical sense. However, scatter in the experimental data can also result from experimental uncertainty (i.e., measurement error). Here, results from field and laboratory results are used to estimate how experimental uncertainty contributes to the observed scatter in the measured fluxes and transfer velocities as a function of environmental forcing. The results show that experimental uncertainty could explain half of the observed scatter in field and laboratory measurements of air-sea gas transfer velocity
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A descriptive study of the effectiveness of an independent living program
The project is concerned with the effectiveness of the Independent Living Program (ILP) in assessing the effectiveness of preparing youth for emancipation from the foster care system. Specifically, the project focused on ILP participants\u27 preparedness to live independently as determined by: education, housing, employment/career, and money management skills attained
The Populations of Comet-Like Bodies in the Solar system
A new classification scheme is introduced for comet-like bodies in the Solar
system. It covers the traditional comets as well as the Centaurs and
Edgeworth-Kuiper belt objects. At low inclinations, close encounters with
planets often result in near-constant perihelion or aphelion distances, or in
perihelion-aphelion interchanges, so the minor bodies can be labelled according
to the planets predominantly controlling them at perihelion and aphelion. For
example, a JN object has a perihelion under the control of Jupiter and aphelion
under the control of Neptune, and so on. This provides 20 dynamically distinct
categories of outer Solar system objects in the Jovian and trans-Jovian
regions. The Tisserand parameter with respect to the planet controlling
perihelion is also often roughly constant under orbital evolution. So, each
category can be further sub-divided according to the Tisserand parameter. The
dynamical evolution of comets, however, is dominated not by the planets nearest
at perihelion or aphelion, but by the more massive Jupiter. The comets are
separated into four categories -- Encke-type, short-period, intermediate and
long-period -- according to aphelion distance. The Tisserand parameter
categories now roughly correspond to the well-known Jupiter-family comets,
transition-types and Halley-types. In this way, the nomenclature for the
Centaurs and Edgeworth-Kuiper belt objects is based on, and consistent with,
that for comets.Comment: MNRAS, in press, 11 pages, 6 figures (1 available as postscript, 5 as
gif). Higher resolution figures available at
http://www-thphys.physics.ox.ac.uk/users/WynEvans/preprints.pd
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