570 research outputs found
Location of the Gamma-Ray Flaring Emission in the Parse-Scale Jet of the BL Lac Object AO 0235+164
We locate the gamma-ray and lower frequency emission in flares of the BL Lac
object AO 0235+164 at >12pc in the jet of the source from the central engine.
We employ time-dependent multi-spectral-range flux and linear polarization
monitoring observations, as well as ultra-high resolution (~0.15
milliarcsecond) imaging of the jet structure at lambda=7mm. The time
coincidence in the end of 2008 of the propagation of the brightest superluminal
feature detected in AO 0235+164 (Qs) with an extreme multi-spectral-range
(gamma-ray to radio) outburst, and an extremely high optical and 7mm (for Qs)
polarization degree provides strong evidence supporting that all these events
are related. This is confirmed at high significance by probability arguments
and Monte-Carlo simulations. These simulations show the unambiguous correlation
of the gamma-ray flaring state in the end of 2008 with those in the optical,
millimeter, and radio regime, as well as the connection of a prominent X-ray
flare in October 2008, and of a series of optical linear polarization peaks,
with the set of events in the end of 2008. The observations are interpreted as
the propagation of an extended moving perturbation through a re-collimation
structure at the end of the jet's acceleration and collimation zone.Comment: To be published in the proceedings of High Energy Phenomena in
Relativistic Outflows III (HEPRO III, IJMPCS). 6 page
On the Location of the Gamma-ray Emission in the 2008 Outburst in the BL Lacertae Object AO 0235+164 through Observations across the Electromagnetic Spectrum
We present observations of a major outburst at centimeter, millimeter,
optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO
0235+164. We analyze the timing of multi-waveband variations in the flux and
linear polarization, as well as changes in Very Long Baseline Array (VLBA)
images at 7mm with 0.15 milliarcsecond resolution. The association of the
events at different wavebands is confirmed at high statistical significance by
probability arguments and Monte-Carlo simulations. A series of sharp peaks in
optical linear polarization, as well as a pronounced maximum in the 7 mm
polarization of a superluminal jet knot, indicate rapid fluctuations in the
degree of ordering of the magnetic field. These results lead us to conclude
that the outburst occurred in the jet both in the quasi-stationary "core" and
in the superluminal knot, both parsecs downstream of the supermassive black
hole. We interpret the outburst as a consequence of the propagation of a
disturbance, elongated along the line of sight by light-travel time delays,
that passes through a standing recollimation shock in the core and propagates
down the jet to create the superluminal knot. The multi-wavelength light curves
vary together on long time-scales (months/years), but the correspondence is
poorer on shorter time-scales. This, as well as the variability of the
polarization and the dual location of the outburst, agrees with the
expectations of a multi-zone emission model in which turbulence plays a major
role in modulating the synchrotron and inverse Compton fluxes.Comment: Accepted for Publication in the Astrophysical Journal Letters. 7
pages (including 5 figures). Minor corrections with regard to previous
version, as proposed by the refere
Exoplanet Science Priorities from the Perspective of Internal and Surface Processes for Silicate and Ice Dominated Worlds
The geophysics of extrasolar planets is a scientific topic often regarded as
standing largely beyond the reach of near-term observations. This reality in no
way diminishes the central role of geophysical phenomena in shaping planetary
outcomes, from formation, to thermal and chemical evolution, to numerous issues
of surface and near-surface habitability. We emphasize that for a balanced
understanding of extrasolar planets, it is important to look beyond the natural
biases of current observing tools, and actively seek unique pathways to
understand exoplanet interiors as best as possible during the long interim
prior to a time when internal components are more directly accessible. Such
pathways include but are not limited to: (a) enhanced theoretical and numerical
modeling, (b) laboratory research on critical material properties, (c)
measurement of geophysical properties by indirect inference from imprints left
on atmospheric and orbital properties, and (d) the purpose-driven use of Solar
System object exploration expressly for its value in comparative planetology
toward exoplanet-analogs. Breaking down barriers that envision local Solar
System exploration, including the study of Earth's own deep interior, as
separate from and in financial competition with extrasolar planet research, may
greatly improve the rate of needed scientific progress for exoplanet
geophysics. As the number of known rocky and icy exoplanets grows in the years
ahead, we expect demand for expertise in 'exogeoscience' will expand at a
commensurately intense pace. We highlight key topics, including: how water
oceans below ice shells may dominate the total habitability of our galaxy by
volume, how free-floating nomad planets may often attain habitable subsurface
oceans supported by radionuclide decay, and how deep interiors may critically
interact with atmospheric mass loss via dynamo-driven magnetic fields
Highly Volcanic Exoplanets, Lava Worlds, and Magma Ocean Worlds:An Emerging Class of Dynamic Exoplanets of Significant Scientific Priority
Highly volcanic exoplanets, which can be variously characterized as 'lava
worlds', 'magma ocean worlds', or 'super-Ios' are high priority targets for
investigation. The term 'lava world' may refer to any planet with extensive
surface lava lakes, while the term 'magma ocean world' refers to planets with
global or hemispherical magma oceans at their surface. 'Highly volcanic
planets', including super-Ios, may simply have large, or large numbers of,
active explosive or extrusive volcanoes of any form. They are plausibly highly
diverse, with magmatic processes across a wide range of compositions,
temperatures, activity rates, volcanic eruption styles, and background
gravitational force magnitudes. Worlds in all these classes are likely to be
the most characterizable rocky exoplanets in the near future due to
observational advantages that stem from their preferential occurrence in short
orbital periods and their bright day-side flux in the infrared. Transit
techniques should enable a level of characterization of these worlds analogous
to hot Jupiters. Understanding processes on highly volcanic worlds is critical
to interpret imminent observations. The physical states of these worlds are
likely to inform not just geodynamic processes, but also planet formation, and
phenomena crucial to habitability. Volcanic and magmatic activity uniquely
allows chemical investigation of otherwise spectroscopically inaccessible
interior compositions. These worlds will be vital to assess the degree to which
planetary interior element abundances compare to their stellar hosts, and may
also offer pathways to study both the very young Earth, and the very early form
of many silicate planets where magma oceans and surface lava lakes are expected
to be more prevalent. We suggest that highly volcanic worlds may become second
only to habitable worlds in terms of both scientific and public long-term
interest.Comment: A white paper submitted in response to the National Academy of
Sciences 2018 Exoplanet Science Strategy solicitation, from the NASA Sellers
Exoplanet Environments Collaboration (SEEC) of the Goddard Space Flight
Center. 6 pages, 0 figure
Positive impacts of important bird and biodiversity areas on wintering waterbirds under changing temperatures throughout Europe and North Africa
Migratory waterbirds require an effectively conserved cohesive network of wetland areas throughout their range and life-cycle. Under rapid climate change, protected area (PA) networks need to be able to accommodate climate-driven range shifts in wildlife if they are to continue to be effective in the future. Thus, we investigated geographical variation in the relationship between local temperature anomaly and the abundance of 61 waterbird species during the wintering season across Europe and North Africa during 1990-2015. We also compared the spatio-temporal effects on abundance of sites designated as PAs, Important Bird and Biodiversity Areas (IBAs), both, or neither designation (Unlisted). Waterbird abundance was positively correlated with temperature anomaly, with this pattern being strongest towards north and east Europe. Waterbird abundance was higher inside IBAs, whether they were legally protected or not. Trends in waterbird abundance were also consistently more positive inside both protected and unprotected IBAs across the whole study region, and were positive in Unlisted wetlands in southwestern Europe and North Africa. These results suggest that IBAs are important sites for wintering waterbirds, but also that populations are shifting to unprotected wetlands (some of which are IBAs). Such IBAs may therefore represent robust candidate sites to expand the network of legally protected wetlands under climate change in north-eastern Europe. These results underscore the need for monitoring to understand how the effectiveness of site networks is changing under climate change.Peer reviewe
Differential cross section measurements for the production of a W boson in association with jets in proton–proton collisions at √s = 7 TeV
Measurements are reported of differential cross sections for the production of a W boson, which decays into a muon and a neutrino, in association with jets, as a function of several variables, including the transverse momenta (pT) and pseudorapidities of the four leading jets, the scalar sum of jet transverse momenta (HT), and the difference in azimuthal angle between the directions of each jet and the muon. The data sample of pp collisions at a centre-of-mass energy of 7 TeV was collected with the CMS detector at the LHC and corresponds to an integrated luminosity of 5.0 fb[superscript −1]. The measured cross sections are compared to predictions from Monte Carlo generators, MadGraph + pythia and sherpa, and to next-to-leading-order calculations from BlackHat + sherpa. The differential cross sections are found to be in agreement with the predictions, apart from the pT distributions of the leading jets at high pT values, the distributions of the HT at high-HT and low jet multiplicity, and the distribution of the difference in azimuthal angle between the leading jet and the muon at low values.United States. Dept. of EnergyNational Science Foundation (U.S.)Alfred P. Sloan Foundatio
Optimasi Portofolio Resiko Menggunakan Model Markowitz MVO Dikaitkan dengan Keterbatasan Manusia dalam Memprediksi Masa Depan dalam Perspektif Al-Qur`an
Risk portfolio on modern finance has become increasingly technical, requiring the use of sophisticated mathematical tools in both research and practice. Since companies cannot insure themselves completely against risk, as human incompetence in predicting the future precisely that written in Al-Quran surah Luqman verse 34, they have to manage it to yield an optimal portfolio. The objective here is to minimize the variance among all portfolios, or alternatively, to maximize expected return among all portfolios that has at least a certain expected return. Furthermore, this study focuses on optimizing risk portfolio so called Markowitz MVO (Mean-Variance Optimization). Some theoretical frameworks for analysis are arithmetic mean, geometric mean, variance, covariance, linear programming, and quadratic programming. Moreover, finding a minimum variance portfolio produces a convex quadratic programming, that is minimizing the objective function ðð¥with constraintsð ð 𥠥 ðandð´ð¥ = ð. The outcome of this research is the solution of optimal risk portofolio in some investments that could be finished smoothly using MATLAB R2007b software together with its graphic analysis
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