2,959 research outputs found
Use of a large jet transport as an inflight dynamic simulator
Modified jet transport used as inflight dynamic simulator for supersonic transport low speed approach and landing characteristic
Core-collapse supernovae ages and metallicities from emission-line diagnostics of nearby stellar populations
Massive stars are the main objects that illuminate H II regions and they
evolve quickly to end their lives in core-collapse supernovae (CCSNe). Thus it
is important to investigate the association between CCSNe and H II regions. In
this paper, we present emission line diagnostics of the stellar populations
around nearby CCSNe, that include their host H II regions, from the PMAS/PPAK
Integral-field Supernova hosts COmpilation (PISCO). We then use BPASS stellar
population models to determine the age, metallicity and gas parameters for H II
regions associated with CCSNe, contrasting models that consider either single
star evolution alone or incorporate interacting binaries. We find binary-star
models, that allow for ionizing photon loss, provide a more realistic fit to
the observed CCSN hosts with metallicities that are closer to those derived
from the oxygen abundance in O3N2. We also find that type II and type Ibc SNe
arise from progenitor stars of similar age, mostly from 7 to 45 Myr, which
corresponds to stars with masses < 20 solar mass . However these two types SNe
have little preference in their host environment metallicity measured by oxygen
abundance or in progenitor initial mass. We note however that at lower
metallicities supernovae are more likely to be of type II.Comment: 22 pages, 19 Figures, 6 Tables. Accepted by MNRAS. Comments welcom
Observations of the Optical Afterglow of GRB 050319 : Wind to ISM transition in view
The collapse of a massive star is believed to be the most probable progenitor
of a long GRB. Such a star is expected to modify its environment by stellar
wind. The effect of such a circum-stellar wind medium is expected to be seen in
the evolution of a GRB afterglow, but has so far not been conclusively found.
We claim that a signature of wind to constant density medium transition of
circum-burst medium is visible in the afterglow of GRB 050319. Along with the
optical observations of the afterglow of GRB 050319 we present a model for the
multiband afterglow of GRB 050319. We show that the break seen in optical light
curve at 0.02 day could be explained as being due to wind to constant
density medium transition of circum-burst medium, in which case, to our
knowledge, this could be the first ever detection of such a transition at any
given frequency band. Detection of such a transition could also serve as a
confirmation of massive star collapse scenario for GRB progenitors, independent
of supernova signatures.Comment: 11 pages, 3 tables, 1 figure
Arkansas Soybean Performance Tests 2008
Soybean cultivar performance tests are conducted each year in Arkansas by the University of Arkansas Division of Agriculture. The tests provide information to companies developing cultivars and/or marketing seed within the state, and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for soybean producer
Arkansas Soybean Performance Tests 2007
Soybean cultivar performance tests are conducted each year in Arkansas by the University of Arkansas Division of Agriculture. The tests provide information to companies developing cultivars and/or marketing seed within the State, and aid the Arkansas Cooperative Extension Service in formulating cultivar recommendations for soybean producers
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