60,586 research outputs found
Circumstellar Disks Around Binary Stars in Taurus
We have conducted a survey of 17 wide (> 100 AU) young binary systems in
Taurus with the Atacama Large Millimeter Array (ALMA) at two wavelengths. The
observations were designed to measure the masses of circumstellar disks in
these systems as an aid to understanding the role of multiplicity in star and
planet formation. The ALMA observations had sufficient resolution to localize
emission within the binary system. Disk emission was detected around all
primaries and ten secondaries, with disk masses as low as .
We compare the properties of our sample to the population of known disks in
Taurus and find that the disks from this binary sample match the scaling
between stellar mass and millimeter flux of
to within the scatter found in previous studies. We also compare the properties
of the primaries to those of the secondaries and find that the
secondary/primary stellar and disk mass ratios are not correlated; in three
systems, the circumsecondary disk is more massive than the circumprimary disk,
counter to some theoretical predictions.Comment: To appear in the Astrophysical Journal, 12 page
Factors Associated with the Selection of Cooperative vs. Proprietary Handlers of Milk in Tennessee
Factors that influenced the decision by dairy farmers to select cooperatives milk handlers versus proprietary handlers were examined. In a 1989 survey, Tennessee dairy farmers were asked to indicate reasons that influenced their choice of milk handler, such as better price, an assured market, and better service. Characteristics of the dairy farmers were then compared between those who selected a specific reason and those who did not. Better service and an assured market were the most often cited reasons by cooperative members, and higher price and lower deductions were cited more often by nonmembers. Farmers who cited price as a reason tended to have larger dairy farms, be less diversified, and more indebted than those who did not cite price as a reason. Those who selected service as a reason had more dairying experience and were less indebted than those who did not select service.Agribusiness, Livestock Production/Industries,
Protoplanetary Disk Mass Distribution in Young Binaries
We present millimeter-wave continuum images of four wide (separations 210-800
AU) young stellar binary systems in the Taurus-Auriga star-forming region. For
all four sources, the resolution of our observations is sufficient to determine
the mm emission from each of the components. In all four systems, the primary
star's disk has stronger millimeter emission than the secondary and in three of
the four, the secondary is undetected; this is consistent with predictions of
recent models of binary formation by fragmentation. The primaries'
circumstellar disk masses inferred from these observations are comparable to
those found for young single stars, confirming that the presence of a wide
binary companion does not prevent the formation of a protoplanetary disk. Some
of the secondaries show signatures of accretion (H-alpha emission and K - L
excesses), yet their mm fluxes suggest that very little disk mass is present.Comment: Accepted by ApJ, to appear Feb. 2003; 9 pages, 5 postscript figures,
uses aastex, emulateapj5, and apjfonts style files. Also available at
http://astro.swarthmore.edu/~jensen/publications.htm
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