110 research outputs found
Investigation of planetary ionospheres
Feasibility of using radio sounding techniques to investigate ionospheric properties of planet
Confucian Economics: The World at Work
Chinese have their school of economics. Not recognized as a discipline, it can be extracted from Confucian doctrine. Called here “Confucian economics,” it is a form of ethics. Its seven consecutive principles are identified for the first time. They differ from and overlap with the corresponding principles of liberal economics. People are assumed to seek posterity rather than care for “instant gratification.” Physical resources they need are not viewed as scarce but as abundant. To survive under abundance, people rely on their work effort rather than try to take resources away from others. “Work ethics” and not a “profit margin” is a key motive. People work not for themselves but for others, basically families. As a source of moral rules, family is viewed as the main “work unit” and not the individual. Equality of income is paramount for retaining social peace, which precedes economic efficiency. Built on Confucian principles, economic system is basically a market system. However, it is animated not by individuals but by families. This design is called here “Confucian system.” Rather than to build based on liberal economics “capitalist system,” recent China is rebuilding “Confucian system.” Drawn from ancient teachings, “Confucian economics” is China's modernity
Discovery of Variability of the Progenitor of SN 2011dh in M51 Using the Large Binocular Telescope
We show that the candidate progenitor of the core-collapse SN 2011dh in M51
(8 Mpc away) was fading by 0.039 +- 0.006 mag/year during the three years prior
to the supernova, and that this level of variability is moderately unusual for
other similar stars in M 51. While there are uncertainties about whether the
true progenitor was a blue companion to this candidate, the result illustrates
that there are no technical challenges to obtaining fairly high precision light
curves of supernova progenitors using ground based observations of nearby (<10
Mpc) galaxies with wide field cameras on 8m-class telescopes. While other
sources of variability may dominate, it is even possible to reach into the
range of evolution rates required by the quasi-static evolution of the stellar
envelope. For M 81, where we have many more epochs and a slightly longer time
baseline, our formal 3 sigma sensitivity to slow changes is presently 3
millimag/year for a M_V ~= -8 mag star. In short, there is no observational
barrier to determining whether the variability properties of stars in their
last phases of evolution (post Carbon ignition) are different from earlier
phases.Comment: 17 pages, 5 figures, submitted to Ap
Supernova 2007bi as a pair-instability explosion
Stars with initial masses 10 M_{solar} < M_{initial} < 100 M_{solar} fuse
progressively heavier elements in their centres, up to inert iron. The core
then gravitationally collapses to a neutron star or a black hole, leading to an
explosion -- an iron-core-collapse supernova (SN). In contrast, extremely
massive stars (M_{initial} > 140 M_{solar}), if such exist, have oxygen cores
which exceed M_{core} = 50 M_{solar}. There, high temperatures are reached at
relatively low densities. Conversion of energetic, pressure-supporting photons
into electron-positron pairs occurs prior to oxygen ignition, and leads to a
violent contraction that triggers a catastrophic nuclear explosion. Tremendous
energies (>~ 10^{52} erg) are released, completely unbinding the star in a
pair-instability SN (PISN), with no compact remnant. Transitional objects with
100 M_{solar} < M_{initial} < 140 M_{solar}, which end up as iron-core-collapse
supernovae following violent mass ejections, perhaps due to short instances of
the pair instability, may have been identified. However, genuine PISNe, perhaps
common in the early Universe, have not been observed to date. Here, we present
our discovery of SN 2007bi, a luminous, slowly evolving supernova located
within a dwarf galaxy (~1% the size of the Milky Way). We measure the exploding
core mass to be likely ~100 M_{solar}, in which case theory unambiguously
predicts a PISN outcome. We show that >3 M_{solar} of radioactive 56Ni were
synthesized, and that our observations are well fit by PISN models. A PISN
explosion in the local Universe indicates that nearby dwarf galaxies probably
host extremely massive stars, above the apparent Galactic limit, perhaps
resulting from star formation processes similar to those that created the first
stars in the Universe.Comment: Accepted version of the paper appearing in Nature, 462, 624 (2009),
including all supplementary informatio
SN 2008jb: A "Lost" Core-Collapse Supernova in a Star-Forming Dwarf Galaxy at ~10 Mpc
We present the discovery and follow-up observations of SN 2008jb, a
core-collapse supernova in the dwarf irregular galaxy ESO 302-14 at 9.6 Mpc.
This transient was missed by galaxy-targeted surveys and was only found in
archival optical images obtained by CRTS and ASAS. It was detected shortly
after explosion and reached a bright optical maximum, Vmax = 13.6 mag (M_Vmax ~
-16.5). The shape of the light curve shows a plateau of 100 days, followed by a
drop of 1.4 mag in V-band to a decline with the approximate Co 56 decay slope,
consistent with 0.04 Msun of Ni 56 synthesized in the explosion. A spectrum
obtained 2 years after explosion shows a broad, boxy Halpha emission line,
which is unusual for type IIP supernovae. We detect the supernova in archival
Spitzer and WISE images obtained 8-14 months after explosion, which show clear
signs of warm dust emission. The dwarf irregular host galaxy has a low
gas-phase oxygen abundance, 12 + log(O/H) = 8.2 (~1/5 Solar), similar to those
of the SMC and the hosts of long gamma-ray bursts and luminous core-collapse
supernovae. We study the host environment using GALEX FUV, R-band, and Halpha
images and find that the supernova occurred in a large star-formation complex.
The morphology of the Halpha emission appears as a large shell (R = 350 pc)
surrounding the FUV and optical emission. We estimate an age of ~9 Myr and a
total mass of ~2 x 10^5 Msun for the star-formation complex. These properties
are consistent with the expanding Halpha supershells observed in well-studied
nearby dwarf galaxies, which are tell-tale signs of feedback from the
cumulative effect of massive star winds and supernovae. The age estimated for
the star-forming region suggests a relatively high-mass progenitor star with
initial mass of ~20 Msun. We discuss the implications of these findings in the
study of core-collapse supernova progenitors. (Abridged)Comment: 41 pages, 10 figures, accepted in ApJ; small changes, conclusions
unchange
Feasibility studies of the time-like proton electromagnetic form factor measurements with PANDA at FAIR
The possibility of measuring the proton electromagnetic form factors in the
time-like region at FAIR with the \PANDA detector is discussed. Detailed
simulations on signal efficiency for the annihilation of into a
lepton pair as well as for the most important background channels have been
performed. It is shown that precision measurements of the differential cross
section of the reaction can be obtained in a wide
angular and kinematical range. The individual determination of the moduli of
the electric and magnetic proton form factors will be possible up to a value of
momentum transfer squared of (GeV/c). The total cross section will be measured up to (GeV/c).
The results obtained from simulated events are compared to the existing data.
Sensitivity to the two photons exchange mechanism is also investigated.Comment: 12 pages, 4 tables, 8 figures Revised, added details on simulations,
4 tables, 9 figure
Spectroscopic identification of r-process nucleosynthesis in a double neutron-star merger.
The merger of two neutron stars is predicted to give rise to three major detectable phenomena: a short burst of γ-rays, a gravitational-wave signal, and a transient optical-near-infrared source powered by the synthesis of large amounts of very heavy elements via rapid neutron capture (the r-process). Such transients, named 'macronovae' or 'kilonovae', are believed to be centres of production of rare elements such as gold and platinum. The most compelling evidence so far for a kilonova was a very faint near-infrared rebrightening in the afterglow of a short γ-ray burst at redshift z = 0.356, although findings indicating bluer events have been reported. Here we report the spectral identification and describe the physical properties of a bright kilonova associated with the gravitational-wave source GW170817 and γ-ray burst GRB 170817A associated with a galaxy at a distance of 40 megaparsecs from Earth. Using a series of spectra from ground-based observatories covering the wavelength range from the ultraviolet to the near-infrared, we find that the kilonova is characterized by rapidly expanding ejecta with spectral features similar to those predicted by current models. The ejecta is optically thick early on, with a velocity of about 0.2 times light speed, and reaches a radius of about 50 astronomical units in only 1.5 days. As the ejecta expands, broad absorption-like lines appear on the spectral continuum, indicating atomic species produced by nucleosynthesis that occurs in the post-merger fast-moving dynamical ejecta and in two slower (0.05 times light speed) wind regions. Comparison with spectral models suggests that the merger ejected 0.03 to 0.05 solar masses of material, including high-opacity lanthanides
Feasibility studies for the measurement of time-like proton electromagnetic form factors from p¯ p→ μ+μ- at P ¯ ANDA at FAIR
This paper reports on Monte Carlo simulation results for future measurements of the moduli of time-like proton electromagnetic form factors, | GE| and | GM| , using the p¯ p→ μ+μ- reaction at P ¯ ANDA (FAIR). The electromagnetic form factors are fundamental quantities parameterizing the electric and magnetic structure of hadrons. This work estimates the statistical and total accuracy with which the form factors can be measured at P ¯ ANDA , using an analysis of simulated data within the PandaRoot software framework. The most crucial background channel is p¯ p→ π+π-, due to the very similar behavior of muons and pions in the detector. The suppression factors are evaluated for this and all other relevant background channels at different values of antiproton beam momentum. The signal/background separation is based on a multivariate analysis, using the Boosted Decision Trees method. An expected background subtraction is included in this study, based on realistic angular distributions of the background contribution. Systematic uncertainties are considered and the relative total uncertainties of the form factor measurements are presented
Astronomical Distance Determination in the Space Age: Secondary Distance Indicators
The formal division of the distance indicators into primary and secondary leads to difficulties in description of methods which can actually be used in two ways: with, and without the support of the other methods for scaling. Thus instead of concentrating on the scaling requirement we concentrate on all methods of distance determination to extragalactic sources which are designated, at least formally, to use for individual sources. Among those, the Supernovae Ia is clearly the leader due to its enormous success in determination of the expansion rate of the Universe. However, new methods are rapidly developing, and there is also a progress in more traditional methods. We give a general overview of the methods but we mostly concentrate on the most recent developments in each field, and future expectations. © 2018, The Author(s)
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