7,567 research outputs found
A Tale of Two Impostors: SN2002kg and SN1954J in NGC 2403
We describe new results on two supernova impostors in NGC 2403, SN 1954J(V12)
and SN 2002kg(V37). For the famous object SN 1954J we combine four critical
observations: its current SED, its Halpha emission line profile, the Ca II
triplet in absorption in its red spectrum, and the brightness compared to its
pre-event state. Together these strongly suggest that the survivor is now a hot
supergiant with T ~ 20000 K, a dense wind, substantial circumstellar
extinction, and a G-type supergiant companion. The hot star progenitor of V12's
giant eruption was likely in the post-red supergiant stage and had already shed
a lot of mass. V37 is a classical LBV/S Dor variable. Our photometry and
spectra observed during and after its eruption show that its outburst was an
apparent transit on the HR Diagram due to enhanced mass loss and the formation
of a cooler, dense wind. V37 is an evolved hot supergiant at ~10^6 Lsun with a
probable initial mass of 60 -80 Msun.Comment: To appear in the Astrophysical Journa
An efficient MPI/OpenMP parallelization of the Hartree-Fock method for the second generation of Intel Xeon Phi processor
Modern OpenMP threading techniques are used to convert the MPI-only
Hartree-Fock code in the GAMESS program to a hybrid MPI/OpenMP algorithm. Two
separate implementations that differ by the sharing or replication of key data
structures among threads are considered, density and Fock matrices. All
implementations are benchmarked on a super-computer of 3,000 Intel Xeon Phi
processors. With 64 cores per processor, scaling numbers are reported on up to
192,000 cores. The hybrid MPI/OpenMP implementation reduces the memory
footprint by approximately 200 times compared to the legacy code. The
MPI/OpenMP code was shown to run up to six times faster than the original for a
range of molecular system sizes.Comment: SC17 conference paper, 12 pages, 7 figure
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