2,124 research outputs found
Alfven seismic vibrations of crustal solid-state plasma in quaking paramagnetic neutron star
Magneto-solid-mechanical model of two-component, core-crust, paramagnetic
neutron star responding to quake-induced perturbation by differentially
rotational, torsional, oscillations of crustal electron-nuclear solid-state
plasma about axis of magnetic field frozen in the immobile paramagnetic core is
developed. Particular attention is given to the node-free torsional
crust-against-core vibrations under combined action of Lorentz magnetic and
Hooke's elastic forces; the damping is attributed to Newtonian force of shear
viscose stresses in crustal solid-state plasma. The spectral formulae for the
frequency and lifetime of this toroidal mode are derived in analytic form and
discussed in the context of quasi-periodic oscillations of the X-ray outburst
flux from quaking magnetars. The application of obtained theoretical spectra to
modal analysis of available data on frequencies of oscillating outburst
emission suggests that detected variability is the manifestation of crustal
Alfven's seismic vibrations restored by Lorentz force of magnetic field
stresses.Comment: 10 pages, 10 figure
Discovery of {\gamma}-ray pulsation and X-ray emission from the black widow pulsar PSR J2051-0827
We report the discovery of pulsed {\gamma}-ray emission and X-ray emission
from the black widow millisecond pulsar PSR J2051-0827 by using the data from
the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope and
the Advanced CCD Imaging Spectrometer array (ACIS-S) on the Chandra X-ray
Observatory. Using 3 years of LAT data, PSR J2051-0827 is clearly detected in
{\gamma}-ray with a signicance of \sim 8{\sigma} in the 0.2 - 20 GeV band. The
200 MeV - 20 GeV {\gamma}-ray spectrum of PSR J2051-0827 can be modeled by a
simple power- law with a photon index of 2.46 \pm 0.15. Significant (\sim
5{\sigma}) {\gamma}-ray pulsations at the radio period were detected. PSR
J2051-0827 was also detected in soft (0.3-7 keV) X-ray with Chandra. By
comparing the observed {\gamma}-rays and X-rays with theoretical models, we
suggest that the {\gamma}-ray emission is from the outer gap while the X-rays
can be from intra-binary shock and pulsar magnetospheric synchrotron emissions.Comment: 10 pages, 4 figures, accepted by ApJ on Jan 28, 201
Farnesyl diphosphate synthase may determine the accumulation level of (−)-rotundone in 'Syrah' grapes
(−)-Rotundone is an oxygenated sesquiterpene responsible for the peppery aroma in grapes, wines, herbs, and spices, and it was first identified in 'Syrah' wine from Australia. In this study, we demonstrated the expression profiles of genes related to (−)-rotundone biosynthesis during the maturation of 'Syrah' grapes from two different vineyards, namely, the Iwaimura and Johnohira vineyards in Japan. The α-guaiene and (−)-rotundone accumulation levels in the grape exocarp from the Johnohira vineyard, which has a cool climatic condition located at a high altitude, were extremely higher than those from the Iwaimura vineyard. Among the 2-C-methyl-D-erythritol-4-phosphate (MEP) pathway genes, the transcript levels of 1-deoxy-D-xylulose-5-phosphate synthase gene (DXS) in the grape exocarp from the Johnohira vineyard were higher than those from the Iwaimura vineyard after véraison. The expression levels of the mevalonate pathway genes, Vitis vinifera terpene synthase gene (VvTPS24) and cytochrome P450 gene (CYP71BE5) in the final step of (−)-rotundone biosynthesis were not significantly different between samples from the two vineyards during grape maturation. In contrast, the farnesyl diphosphate synthase gene (FPPS) expression level was considerably higher in the grape exocarp from the Johnohira vineyard than in that from the Iwaimura vineyard. Consistent with these observations, FPPS was constantly expressed at higher level in 'Syrah' grape exocarp compared with 'Merlot' grape which is a low-rotundone cultivar. These findings suggest that FPPS may play a key role in determining the accumulation level of (−)-rotundone, which can provide abundant substrates for VvTPS24 catalysis to produce α-guaiene as a precursor of (−)-rotundone. In addition, among the MEP pathway genes, DXS may have a regulatory role for a precursor supply from the plastids to (−)-rotundone biosynthesis
Asteroseismic detection of latitudinal differential rotation in 13 Sun-like stars
The differentially rotating outer layers of stars are thought to play a role
in driving their magnetic activity, but the underlying mechanisms that generate
and sustain differential rotation are poorly understood. We report the
measurement of latitudinal differential rotation in the convection zones of 40
Sun-like stars using asteroseismology. For the most significant detections, the
stars' equators rotate approximately twice as fast as their mid-latitudes. The
latitudinal shear inferred from asteroseismology is much larger than
predictions from numerical simulations.Comment: 45 pages, 11 figures, 4 tables, published in Scienc
ADIPLS -- the Aarhus adiabatic oscillation package
Development of the Aarhus adiabatic pulsation code started around 1978.
Although the main features have been stable for more than a decade, development
of the code is continuing, concerning numerical properties and output. The code
has been provided as a generally available package and has seen substantial use
at a number of installations. Further development of the package, including
bringing the documentation closer to being up to date, is planned as part of
the HELAS Coordination Action.Comment: Astrophys. Space Sci., in the pres
- …