2,872 research outputs found
Dynamical Measurements of the Young Upper Scorpius Triple NTTS 155808-2219
The young, low-mass, triple system NTTS 155808-2219 (ScoPMS 20) was
previously identified as a ~17-day period single-lined spectroscopic binary
with a tertiary component at 0.21 arcseconds. Using high-resolution infrared
spectra, acquired with NIRSPEC on Keck II, both with and without adaptive
optics, we measured radial velocities of all three components. Reanalysis of
the single-lined visible light observations, made from 1987 to 1993, also
yielded radial velocity detections of the three stars. Combining visible light
and infrared data to compute the orbital solution produces orbital parameters
consistent with the single-lined solution and a mass ratio of q = 0.78 +/- 0.01
for the SB. We discuss the consistency between our results and previously
published data on this system, our radial-velocity analysis with both observed
and synthetic templates, and the possibility that this system is eclipsing,
providing a potential method for the determination of the stars' absolute
masses. Over the ~20 year baseline of our observations, we have measured the
acceleration of the SB's center-of-mass in its orbit with the tertiary.
Long-term, adaptive optics imaging of the tertiary will eventually yield
dynamical data useful for component mass estimates.Comment: 6 Tables, 8 Figures, updated to match published tex
The Double-Lined Spectroscopic Binary Haro 1-14c
We report detection of the low-mass secondary in the spectroscopic binary
Haro 1-14c in the Ophiuchus star forming region. The secondary/primary mass
ratio is . With an estimated photometric primary mass of 1.2
, the secondary mass is and the projected
semi-major axis is AU. The system is well-suited for astrometric
mapping of its orbit with the current generation of ground-based IR
interferometers. This could yield precision values of the system's component
masses and distance.Comment: Accepted by ApJ Letter
Disk Evolution in Young Binaries: from Observations to Theory
The formation of a binary system surrounded by disks is the most common
outcome of stellar formation. Hence studying and understanding the formation
and the evolution of binary systems and associated disks is a cornerstone of
star formation science. Moreover, since the components within binary systems
are coeval and the sizes of their disks are fixed by the tidal truncation of
their companion, binary systems provide an ideal "laboratory" in which to study
disk evolution under well defined boundary conditions.
In this paper, we review observations of several inner disk diagnostics in
multiple systems, including hydrogen emission lines (indicative of ongoing
accretion), and color excesses (evidence of warm inner disks), and
polarization (indicative of the relative orientations of the disks around each
component). We examine to what degree these properties are correlated within
binary systems and how this degree of correlation depends on parameters such as
separation and binary mass ratio. These findings will be interpreted both in
terms of models that treat each disk as an isolated reservoir and those in
which the disks are subject to re-supply from some form of circumbinary
reservoir, the observational evidence for which we will also critically review.
The planet forming potential of multiple star systems is discussed in terms of
the relative lifetimes of disks around single stars, binary primaries and
binary secondaries. Finally, we summarize several potentially revealing
observational problems and future projects that could provide further insight
into disk evolution in the coming decadeComment: 16 pages, 7 figures, chapter in Protostars and Planets
Strong Solutions of Stochastic Generalized Porous Media Equations: Existence, Uniqueness and Ergodicity
Explicit conditions are presented for the existence, uniqueness and
ergodicity of the strong solution to a class of generalized stochastic porous
media equations. Our estimate of the convergence rate is sharp according to the
known optimal decay for the solution of the classical (deterministic) porous
medium equation.Comment: 15 pages; BiBoS-Preprint No. 04-09-157; to appear in Commun. PD
The GL 569 Multiple System
We report the results of high spectral and angular resolution infrared
observations of the multiple system GL 569 A and B that were intended to
measure the dynamical masses of the brown dwarf binary believed to comprise GL
569 B. Our analysis did not yield this result but, instead, revealed two
surprises. First, at age ~100 Myr, the system is younger than had been reported
earlier. Second, our spectroscopic and photometric results provide support for
earlier indications that GL 569 B is actually a hierarchical brown dwarf triple
rather than a binary. Our results suggest that the three components of GL 569 B
have roughly equal mass, ~0.04 Msun.Comment: 29 pages, 10 figures, accepted for publication in the Astrophysical
Journal; minor corrections to Section 5.1; changed typo in 6.
MULTIPLE-OBJECTIVE DECISION MAKING FOR AGROECOSYSTEM MANAGEMENT
Multiple-objective decision making (MODEM) provides an effective framework for integrated resource assessment of agroecosystems. Two elements of integrated assessment are discussed and illustrated: (1) adding noneconomic objectives as constraints in an optimization problem; and (2) evaluating tradeoffs among competing objectives using the efficiency frontier for objectives. These elements are illustrated for a crop farm and watershed in northern Missouri. An interactive, spatial decision support system (ISDSS) makes the MODEM framework accessible to unsophisticated users. A conceptual ISDSS is presented that assesses the socioeconomic, environmental, and ecological consequences of alternative management plans for reducing soil erosion and nonpoint source pollution in agroecosystems. A watershed decision support system based on the ISDSS is discussed.Agribusiness,
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