4,173 research outputs found
High-resolution polarization imaging of the Fermi blazar 3C 279
Ever since the discovery by the Fermi mission that active galactic nuclei (AGN) produce copious
amounts of high-energy emission, its origin has remained elusive. Using high-frequency radio
interferometry (VLBI) polarization imaging, we could probe the magnetic field topology of the
compact high-energy emission regions in blazars. A case study for the blazar 3C 279 reveals
the presence of multiple g -ray emission regions. Pass 8 Fermi-Large Area Telescope (LAT) data
are used to investigate the flux variations in the GeV regime; six g -ray flares were observed in
the source during November 2013 to August 2014. We use the 43 GHz VLBI data to study
the morphological changes in the jet. Ejection of a new component (NC2) during the first three
g -ray flares suggests the VLBI core as the possible site of the high-energy emission. A delay
between the last three flares and the ejection of a new component (NC3) indicates that highenergy
emission in this case is located upstream of the 43 GHz core (closer to the black hole).Accepted manuscrip
Social and Economic Decline as Factors in Conflict in the Caucasus
We argue that the conflicts in the Caucasus are the result of the abrogation by the elite of the earlier, Soviet era, social contract. This process was accompanied by the collapse of the formal economy; evidenced by huge national income compression, falling public goods provision, and growing inequality and poverty. In the absence of state provision of basic amenities and governance, ordinary people are compelled to fall back on kinship ties. Declining standards of governance facilitate state-sponsored corruption and criminality in a setting where the shadow economic activity is increasingly important to individual survival strategies. Oil pipelines and the right to control the transit of goods both legal and illegal also underlie conflict in the region. Criminality has replaced ethnicity as the major motivation for conflict and conflict per se has become a lucrative source of income.Caucasus, conflict, natural resources
Modeling the time-dependent polarization of blazars
Linear polarization is an extremely valuable observational tool for probing the dynamic physical conditions of blazar jets. Some patterns are seen in the data, suggestive of order that can be explained by shock waves and helical magnetic field components. However, much disorder is apparent, which implies that turbulence plays a major role as well, especially in the fluctuations of flux and polarization, and perhaps particle acceleration. Here, we present some actual flux and polarization versus time data, plus simulations of model jets. We analyze the output of the simulations in a manner that can be compared with observational data. The results suggest that the ratio of turbulent to ordered magnetic fields varies with time.AST-1615796 - National Science Foundation; NASA; NNX14AQ58G; NNX15AR45
"Orphan" -ray Flares and Stationary Sheaths of Blazar Jets
Blazars exhibit flares across the entire electromagnetic spectrum. Many
-ray flares are highly correlated with flares detected at longer
wavelengths; however, a small subset appears to occur in isolation, with little
or no correlated variability at longer wavelengths. These "orphan" -ray
flares challenge current models of blazar variability, most of which are unable
to reproduce this type of behavior. Macdonald et al. have developed the Ring of
Fire model to explain the origin of orphan -ray flares from within
blazar jets. In this model, electrons contained within a blob of plasma moving
relativistically along the spine of the jet inverse-Compton scatter synchrotron
photons emanating off of a ring of shocked sheath plasma that enshrouds the jet
spine. As the blob propagates through the ring, the scattering of the ring
photons by the blob electrons creates an orphan -ray flare. This model
was successfully applied to modeling a prominent orphan -ray flare
observed in the blazar PKS 1510089. To further support the plausibility of
this model, Macdonald et al. presented a stacked radio map of PKS 1510089
containing the polarimetric signature of a sheath of plasma surrounding the
spine of the jet. In this paper, we extend our modeling and stacking techniques
to a larger sample of blazars: 3C 273, 4C 7101, 3C 279, 1055018, CTA 102,
and 3C 345, the majority of which have exhibited orphan -ray flares. We
find that the model can successfully reproduce these flares, while our stacked
maps reveal the existence of jet sheaths within these blazars.Comment: 19 pages, 27 figures, accepted for publication in ApJ. arXiv admin
note: text overlap with arXiv:1505.0123
Features of the Functioning of Housing and Communal Services of Ukraine Особенности функционирования сферы жилищно-коммунальных услуг Украины
In the article the state and the peculiarities of the housing and communal services in today's socio-economic development of the Ukrainian economy is investigated. Indicator-based national statistics the main tendencies in the pricing policy of the enterprise services. The features of the pricing mechanism of this industry is determined. It is concluded that, in the post-crisis period, the housing and communal complex becomes an important element of economic activity. With proper grounded socio-economic policies it can be used as an engine of economic growth, and therefore can serve as a basis for the formation of private capital.<br>В статье исследовано состояние и особенности функционирования сферы жилищно-коммунальных услуг в условиях современного социально-экономического развития экономики Украины. На основе показателей национальной статистики определены основные тенденции в ценовой политике предприятий этой сферы услуг. Исследованы особенности механизма формирования цен этой отрасли. Сделан вывод о том, что в условиях посткризисного периода жилищно-коммунальный комплекс становится важным элементом экономической деятельности. При должной обоснованной социально-экономической политике он может использоваться как двигатель экономического роста, а следовательно и может служить основой для формирования частного капитала
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