231 research outputs found
Element Stratification in the Middle-Aged Type Ia Supernova Remnant G344.7-0.1
Despite their importance, a detailed understanding of Type Ia supernovae (SNe
Ia) remains elusive. X-ray measurements of the element distributions in
supernova remnants (SNRs) offer important clues for understanding the explosion
and nucleosynthesis mechanisms for SNe Ia. However, it is challenging to
observe the entire ejecta mass in X-rays for young SNRs, because the central
ejecta may not have been heated by the reverse shock yet. Here we present over
200 kilosecond Chandra observations of the Type Ia SNR G344.7-0.1, whose age is
old enough for the reverse shock to have reached the SNR center, providing an
opportunity to investigate the distribution of the entire ejecta mass. We
reveal a clear stratification of heavy elements with a centrally peaked
distribution of the Fe ejecta surrounded by intermediate-mass elements (IMEs:
Si, S, Ar Ca) with an arc-like structure. The centroid energy of the Fe K
emission is marginally lower in the central Fe-rich region than in the outer
IME-rich regions, suggesting that the Fe ejecta were shock-heated more
recently. These results are consistent with the prediction for standard SN Ia
models, where the heavier elements are synthesized in the interior of an
exploding white dwarf. We find, however, that the peak location of the Fe K
emission is slightly offset to the west with respect to the geometric center of
the SNR. This apparent asymmetry is likely due to the inhomogeneous density
distribution of the ambient medium, consistent with our radio observations of
the ambient molecular and neutral gas.Comment: 16 pages, 10 figures, Accepted for publication in Astrophysical
Journa
Single-component reflecting objective for low-temperature spectroscopy in the entire visible region
A single-component reflecting objective was constructed for low-temperature spectroscopy with optimal imaging and transmission properties at all visible wavelengths. The performance of the objective immersed in superfluid helium at a temperature of 1.5 K was tested by comparing dark-field images of uncolored polymer beads taken at wavelengths of 400 and 800 nm. Under conditions optimized for imaging at both wavelengths, the size of the image i
Magnetization and transport properties in the superconducting PrBaCuO with metallic double-chain
We have reported the effect of pressure on the magnetization, and transport
properties in the nominal composition PrBaCuO
synthesized by a sol-gel technique. A reduction treatment of the as-sintered
sample in vacuum causes higher superconductivity achieving K
for . Application of hydrostatic pressure on the oxygen depleted
sample enhances its onset temperature up to 36 K at 1.2 GPa, indicating the
nearly optimum doping level of the charge carrier in comparison to the pressure
dependence of lower samples with . Seebeck coefficient of
the superconducting sample shows a metallic conduction, followed by a clear
drop below and is in its temperature dependence below 100 K quite
different from that of the non-superconducting one. This finding strongly
suggests a dramatic change of the electronic state along the CuO double chain
due to the reduction treatment for the appearance of superconductivity .Comment: 5 pages,4 figure
Generating Vegfr3 reporter transgenic mouse expressing membrane-tagged Venus for visualization of VEGFR3 expression in vascular and lymphatic endothelial cells
Vascular endothelial growth factor receptor 3 (Vegfr3) has been widely used as a marker for lymphatic and vascular endothelial cells during mouse embryonic development and in adult mouse, making it valuable for studying angiogenesis and lymphangiogenesis under normal and pathological conditions. Here, we report the generation of a novel transgenic (Tg) mouse that expresses a membrane-localized fluorescent reporter protein, Gap43-Venus, under the control of the Vegfr3 regulatory sequence. Vegfr3-Gap43-Venus BAC Tg recapitulated endogenous Vegfr3 expression in vascular and lymphatic endothelial cells during embryonic development and tumor development. Thus, this Tg mouse line contributes a valuable model to study angiogenesis and lymphangiogenesis in physiological and pathological contexts
The ASTRO-H X-ray Observatory
The joint JAXA/NASA ASTRO-H mission is the sixth in a series of highly
successful X-ray missions initiated by the Institute of Space and Astronautical
Science (ISAS). ASTRO-H will investigate the physics of the high-energy
universe via a suite of four instruments, covering a very wide energy range,
from 0.3 keV to 600 keV. These instruments include a high-resolution,
high-throughput spectrometer sensitive over 0.3-2 keV with high spectral
resolution of Delta E < 7 eV, enabled by a micro-calorimeter array located in
the focal plane of thin-foil X-ray optics; hard X-ray imaging spectrometers
covering 5-80 keV, located in the focal plane of multilayer-coated, focusing
hard X-ray mirrors; a wide-field imaging spectrometer sensitive over 0.4-12
keV, with an X-ray CCD camera in the focal plane of a soft X-ray telescope; and
a non-focusing Compton-camera type soft gamma-ray detector, sensitive in the
40-600 keV band. The simultaneous broad bandpass, coupled with high spectral
resolution, will enable the pursuit of a wide variety of important science
themes.Comment: 22 pages, 17 figures, Proceedings of the SPIE Astronomical
Instrumentation "Space Telescopes and Instrumentation 2012: Ultraviolet to
Gamma Ray
The Quiescent Intracluster Medium in the Core of the Perseus Cluster
Clusters of galaxies are the most massive gravitationally-bound objects in
the Universe and are still forming. They are thus important probes of
cosmological parameters and a host of astrophysical processes. Knowledge of the
dynamics of the pervasive hot gas, which dominates in mass over stars in a
cluster, is a crucial missing ingredient. It can enable new insights into
mechanical energy injection by the central supermassive black hole and the use
of hydrostatic equilibrium for the determination of cluster masses. X-rays from
the core of the Perseus cluster are emitted by the 50 million K diffuse hot
plasma filling its gravitational potential well. The Active Galactic Nucleus of
the central galaxy NGC1275 is pumping jetted energy into the surrounding
intracluster medium, creating buoyant bubbles filled with relativistic plasma.
These likely induce motions in the intracluster medium and heat the inner gas
preventing runaway radiative cooling; a process known as Active Galactic
Nucleus Feedback. Here we report on Hitomi X-ray observations of the Perseus
cluster core, which reveal a remarkably quiescent atmosphere where the gas has
a line-of-sight velocity dispersion of 164+/-10 km/s in a region 30-60 kpc from
the central nucleus. A gradient in the line-of-sight velocity of 150+/-70 km/s
is found across the 60 kpc image of the cluster core. Turbulent pressure
support in the gas is 4% or less of the thermodynamic pressure, with large
scale shear at most doubling that estimate. We infer that total cluster masses
determined from hydrostatic equilibrium in the central regions need little
correction for turbulent pressure.Comment: 31 pages, 11 Figs, published in Nature July
- …