7,837 research outputs found
Solving the kilo-second QPO problem of the intermediate polar GK Persei
We detect the likely optical counterpart to previously reported X-ray QPOs in
spectrophotometry of the intermediate polar GK Persei during the 1996 dwarf
nova outburst. The characteristic timescales range between 4000--6000 s.
Although the QPOs are an order of magnitude longer than those detected in the
other dwarf novae we show that a new QPO model is not required to explain the
long timescale observed. We demonstrate that the observations are consistent
with oscillations being the result of normal-timescale QPOs beating with the
spin period of the white dwarf. We determine the spectral class of the
companion to be consistent with its quiescent classification and find no
significant evidence for irradiation over its inner face. We detect the white
dwarf spin period in line fluxes, V/R ratios and Doppler-broadened emission
profiles.Comment: 14 pages, 11 figures. Accepted for publication in MNRA
Numerical simulations of the internal shock model in magnetized relativistic jets of blazars
The internal shocks scenario in relativistic jets is used to explain the
variability of the blazar emission. Recent studies have shown that the magnetic
field significantly alters the shell collision dynamics, producing a variety of
spectral energy distributions and light-curves patterns. However, the role
played by magnetization in such emission processes is still not entirely
understood. In this work we numerically solve the magnetohydodynamic evolution
of the magnetized shells collision, and determine the influence of the
magnetization on the observed radiation. Our procedure consists in
systematically varying the shell Lorentz factor, relative velocity, and viewing
angle. The calculations needed to produce the whole broadband spectral energy
distributions and light-curves are computationally expensive, and are achieved
using a high-performance parallel code.Comment: 7 pages, 5 figures, proceeding of the "Swift: 10 Years of Discovery"
conference (December 2014, Rome, Italy
The problem of negatives in input-output analysis: a review of the solutions
The main models to construct technical coefficients are the industry technology model and the commodity technology model. The former yields nonnegative coefficients and the latter fulfills nice theoretical properties, such as price invariance. Although the models are very different, this paper presents a flexible formula that encompasses both of them. Various solutions to the problem of negatives of the commodity technology model-including replacements by industry technology based coefficients-are reviewed in our framework.Input-output analysis; technical coefficients; use and make matrices
The self-consistent general relativistic solution for a system of degenerate neutrons, protons and electrons in beta-equilibrium
We present the self-consistent treatment of the simplest, nontrivial,
self-gravitating system of degenerate neutrons, protons and electrons in
-equilibrium within relativistic quantum statistics and the
Einstein-Maxwell equations. The impossibility of imposing the condition of
local charge neutrality on such systems is proved, consequently overcoming the
traditional Tolman-Oppenheimer-Volkoff treatment. We emphasize the crucial role
of imposing the constancy of the generalized Fermi energies. A new approach
based on the coupled system of the general relativistic
Thomas-Fermi-Einstein-Maxwell equations is presented and solved. We obtain an
explicit solution fulfilling global and not local charge neutrality by solving
a sophisticated eigenvalue problem of the general relativistic Thomas-Fermi
equation. The value of the Coulomb potential at the center of the configuration
is and the system is intrinsically stable against
Coulomb repulsion in the proton component. This approach is necessary, but not
sufficient, when strong interactions are introduced.Comment: Letter in press, Physics Letters B (2011
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