241 research outputs found

    The R-Process Alliance: Chemical Abundances for a Trio of R-Process-Enhanced Stars -- One Strong, One Moderate, One Mild

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    We present detailed chemical abundances of three new bright (V ~ 11), extremely metal-poor ([Fe/H] ~ -3.0), r-process-enhanced halo red giants based on high-resolution, high-S/N Magellan/MIKE spectra. We measured abundances for 20-25 neutron-capture elements in each of our stars. J1432-4125 is among the most r-process rich r-II stars, with [Eu/Fe]= +1.44+-0.11. J2005-3057 is an r-I star with [Eu/Fe] = +0.94+-0.07. J0858-0809 has [Eu/Fe] = +0.23+-0.05 and exhibits a carbon abundance corrected for evolutionary status of [C/Fe]_corr = +0.76, thus adding to the small number of known carbon-enhanced r-process stars. All three stars show remarkable agreement with the scaled solar r-process pattern for elements above Ba, consistent with enrichment of the birth gas cloud by a neutron star merger. The abundances for Sr, Y, and Zr, however, deviate from the scaled solar pattern. This indicates that more than one distinct r-process site might be responsible for the observed neutron-capture element abundance pattern. Thorium was detected in J1432-4125 and J2005-3057. Age estimates for J1432-4125 and J2005-3057 were adopted from one of two sets of initial production ratios each by assuming the stars are old. This yielded individual ages of 12+-6 Gyr and 10+-6 Gyr, respectively.Comment: 30 pages, includes a long table, 5 figure

    Model-based motion estimation for synthetic animations

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    One approach to performing motion estimation on syn-thetic animations is to treat them as video sequences and use standard image-based motion estimation meth-ods. Alternatively, we can take advantage of informa-tion used in rendering the animation to guide the motion estimation algorithm. This information includes the 3D movements of the objects in the scene and the projec-tion transformations from 3D world space into screen space. In this paper we examine how to use this high level object motion information to perform fast, accu-rate block-based motion estimation for synthetic anima-tions. The optical ow eld is a 2D vector eld describ-ing the translational motion of each pixel from frame to frame. Our motion estimation algorithm rst com-putes the optical ow eld, based on the object motion information. We then combine the per-pixel motion in-formation for a block of pixels to create a single 2D projective matrix that best encodes the motion of all the pixels in the block. The entries of the 2D matrix are determined using a least squares formulation. Our algo-rithms are more accurate and much faster in algorithmic complexity than many image-based motion estimation algorithms.
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