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Full-Text Articles in Physical Sciences and Mathematics
Sic Particles From Asymptotic Giant Branch Stars: Mg Burning And The S-Process, Lawrence E. Brown, Donald D. Clayton
Sic Particles From Asymptotic Giant Branch Stars: Mg Burning And The S-Process, Lawrence E. Brown, Donald D. Clayton
Donald D Clayton
The question of whether isotopically anomalous SiC particles found in meteorites originate in AGB stars is addressed. It is shown that if the peak helium shell flash temperatures of massive (6-9 solar masses) stars are about 10 percent larger than they are normally assumed to be, alpha particle reactions with the magnesium will become significant. Then the (Mg-29)(alpha, n)Si-29 reaction produces a large excess of Si-29. With a light element nuclear reaction network, the evolution of the silicon isotopic composition during AGB evolution is calculated. It is found that the experimentally determined correlation between excess Si-29 and excess Si-30 in …
Supernova Reverse Shocks: Sic Growth And Isotopic Composition, Ethan A-N. Deneault, Donald D. Clayton, Alexander Heger
Supernova Reverse Shocks: Sic Growth And Isotopic Composition, Ethan A-N. Deneault, Donald D. Clayton, Alexander Heger
Donald D Clayton
We present new mechanisms by which the isotopic compositions of X-type grains of presolar SiC are altered by reverse shocks in Type II supernovae. We address three epochs of reverse shocks: pressure wave from the H envelope near t ¼ 106 s, reverse shock from the presupernova wind near 108–109 s, and reverse shock from the interstellar medium near 1010 s. Using one-dimensional hydrodynamics we show that the first creates a dense shell of Si and C atoms near 106 s in which the SiC surely condenses. The second reverse shock causes precondensed grains to move rapidly forward through decelerated …
The Sdss–2mass–Wise 10 Dimensional Stellar Color Locus, James R. A. Davenport, Željko Ivezić, Andrew C. Becker, John J. Ruan, Nicholas M. Hunt-Walker, Kevin R. Covey, Alexia R. Lewis, Yusra Alsayyad, Lauren M. Anderson
The Sdss–2mass–Wise 10 Dimensional Stellar Color Locus, James R. A. Davenport, Željko Ivezić, Andrew C. Becker, John J. Ruan, Nicholas M. Hunt-Walker, Kevin R. Covey, Alexia R. Lewis, Yusra Alsayyad, Lauren M. Anderson
Physics & Astronomy
We present the fiducial main-sequence stellar locus traced by 10 photometric colours observed by Sloan Digital Sky Survey (SDSS), Two Micron All Sky Survey (2MASS), and Wide-field Infrared Survey Explorer(WISE). Median colours are determined using 1052 793 stars with r-band extinction less than 0.125. We use this locus to measure the dust extinction curve relative to the r band, which is consistent with previous measurements in the SDSS and 2MASS bands. The WISE band extinction coefficients are larger than predicted by standard extinction models. Using 13 lines of sight, we find variations in the extinction curve …
An Anomalous Extinction Law In The Cep Ob3b Young Cluster: Evidence For Dust Processing During Gas Dispersal, Thomas S. Allen, Jakub J. Prchlik, Thomas S. Mageath, R. A. Gutermuth, Judith L. Pipher, Tim Naylor, R.D. Jeffries
An Anomalous Extinction Law In The Cep Ob3b Young Cluster: Evidence For Dust Processing During Gas Dispersal, Thomas S. Allen, Jakub J. Prchlik, Thomas S. Mageath, R. A. Gutermuth, Judith L. Pipher, Tim Naylor, R.D. Jeffries
Robert A. Gutermuth
We determine the extinction law through Cep OB3b, a young cluster of 3000 stars undergoing gas dispersal. The extinction is measured toward 76 background K giants identified with MMT/Hectospec spectra. Color excess ratios were determined toward each of the giants using V and R photometry from the literature, g, r, i, and z photometry from the Sloan Digital Sky Survey and J, H, and Ks photometry from the Two Micron All Sky Survey. These color excess ratios were then used to construct the extinction law through the dusty material associated with Cep OB3b. The extinction law through Cep OB3b is …