19,300 research outputs found
Central Limit Results for Jump-Diffusions with Mean Field Interaction and a Common Factor
A system of weakly interacting particles whose dynamics is given in terms
of jump-diffusions with a common factor is considered. The common factor is
described through another jump-diffusion and the coefficients of the evolution
equation for each particle depend, in addition to its own state value, on the
empirical measure of the states of the particles and the common factor. A
Central Limit Theorem, as , is established. The limit law is
described in terms of a certain Gaussian mixture. An application to models in
Mathematical Finance of self-excited correlated defaults is described
Benchmarking Air Emissions of the 100 Largest Electric Power Producers in the United States
The 2015 Benchmarking report is the eleventh collaborative effort highlighting environmental performance and progress in the nation's electric power sector. The Benchmarking series uses publicly reported data to compare the emissions performance of the 100 largest power producers in the United States. The current report is based on 2013 generation and emissions data.The Benchmarking report facilitates the comparison of emissions performance by combining generation and fuel consumption data compiled by EIA with emissions data on sulfur dioxide (SO2), nitrogen oxides (NOx), carbon dioxide (CO2) and mercury compiled by EPA; error checking the data; and presenting emissions information for the nation's 100 largest power producers in a graphic format that aids in understanding and evaluating the data. The report is intended for a wide audience, including electric industry executives, environmental advocates, financial analysts, investors, journalists, power plant managers, and public policymakers
Calibration of BVRI Photometry for the Wide Field Channel of the HST Advanced Camera for Surveys
We present new observations of two Galactic globular clusters, PAL4 and
PAL14, using the Wide-Field Channel of the Advanced Camera for Surveys (ACS) on
board the Hubble Space Telescope (HST), and reanalyze archival data from a
third, NGC2419. We matched our photometry of hundreds of stars in these fields
from the ACS images to existing, ground-based photometry of faint sequences
which were calibrated on the standard BVRI system of Landolt. These stars are
significantly fainter than those generally used for HST calibration purposes,
and therefore are much better matched to supporting precision photometry of ACS
science targets. We were able to derive more accurate photometric
transformation coefficients for the commonly used ACS broad-band filters
compared to those published by Sirianni, et al. (2005), owing to the use of a
factor of several more calibration stars which span a greater range of color.
We find that the inferred transformations from each cluster individually do not
vary significantly from the average, except for a small offset of the
photometric zeropoint in the F850LP filter. Our results suggest that the
published prescriptions for the time-dependent correction of CCD
charge-transfer efficiency appear to work very well over the ~3.5 yr interval
that spans our observations of PAL4 and PAL14 and the archived images of
NGC2419.Comment: 22 pages, 12 figures. Accepted for publication in PAS
Origin of gamma-ray emission in the shell of Cassiopeia A
Non-thermal X-ray emission from the shell of Cassiopeia A (Cas A) has been an
interesting subject of study, as it provides information about relativistic
electrons and their acceleration mechanisms in the shocks. Chandra X-ray
observatory revealed the detailed spectral and spatial structure of this SNR in
X-rays. The spectral analysis of Chandra X-ray data of Cas A shows unequal flux
levels for different regions of the shell, which can be attributed to different
magnetic fields in those regions. Additionally, the GeV gamma-ray emission
observed by Large Area Telescope on board Fermi Gamma Ray Space Telescope
showed that the hadronic processes are dominating in Cas A, a clear signature
of acceleration of protons. In this paper we aim to explain the GeV-TeV
gamma-ray data in the context of both leptonic and hadronic scenario. We
modeled the multi-wavelength spectrum of Cas A. We use synchrotron emission
process to explain the observed non-thermal X-ray fluxes from different regions
of the shell. These result in estimation of the model parameters, which are
then used to explain TeV gamma-ray emission spectrum. We also use hadronic
scenario to explain both GeV and TeV fluxes simultaneously. We show that a
leptonic model alone cannot explain the GeV-TeV data. Therefore, we need to
invoke a hadronic model to explain the observed GeV-TeV fluxes. We found that
although pure hadronic model is able to explain the GeV-TeV data, a
lepto-hadronic model provides the best fit to the data.Comment: Accepted in A&
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