4,585 research outputs found
Magnetic Fields and Afterglows of BdHNe: Inferences from GRB 130427A, GRB 160509A, GRB 160625B, GRB 180728A and GRB 190114C
GRB 190114C is the first binary-driven hypernova (BdHN) fully observed from
the initial supernova appearance to the final emergence of the optical SN
signal. It offers an unprecedented testing ground for the BdHN theory and it is
here determined and further extended to additional gamma-ray bursts (GRBs).
BdHNe comprise two subclasses of long GRBs with progenitors a binary system
composed of a carbon-oxygen star (CO) and a neutron star (NS)
companion. The CO explodes as a SN leaving at its center a
newborn NS (NS). The SN ejecta hypercritically accretes both on the
NS and the NS companion. BdHNe I are the tightest binaries where the
accretion leads the companion NS to gravitational collapse into a black hole
(BH). In BdHN II the accretion onto the NS is lower, so there is no BH
formation. We observe the same structure of the afterglow for GRB 190114C and
other selected examples of BdHNe I (GRB 130427A, GRB 160509A, GRB 160625B) and
for BdHN II (GRB 180728A). In all the cases the explanation of the afterglow is
reached via the synchrotron emission powered by the NS: their magnetic
fields structures and their spin are determined. For BdHNe I, we discuss the
properties of the magnetic field embedding the newborn BH, inherited from the
collapsed NS and amplified during the gravitational collapse process, and
surrounded by the SN ejecta.Comment: 7 figures, 3 tables, submitted to Ap
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
Long-Term Load Forecasting Considering Volatility Using Multiplicative Error Model
Long-term load forecasting plays a vital role for utilities and planners in
terms of grid development and expansion planning. An overestimate of long-term
electricity load will result in substantial wasted investment in the
construction of excess power facilities, while an underestimate of future load
will result in insufficient generation and unmet demand. This paper presents
first-of-its-kind approach to use multiplicative error model (MEM) in
forecasting load for long-term horizon. MEM originates from the structure of
autoregressive conditional heteroscedasticity (ARCH) model where conditional
variance is dynamically parameterized and it multiplicatively interacts with an
innovation term of time-series. Historical load data, accessed from a U.S.
regional transmission operator, and recession data for years 1993-2016 is used
in this study. The superiority of considering volatility is proven by
out-of-sample forecast results as well as directional accuracy during the great
economic recession of 2008. To incorporate future volatility, backtesting of
MEM model is performed. Two performance indicators used to assess the proposed
model are mean absolute percentage error (for both in-sample model fit and
out-of-sample forecasts) and directional accuracy.Comment: 19 pages, 11 figures, 3 table
On Two Complementary Types of Total Time Derivative in Classical Field Theories and Maxwell's Equations
Close insight into mathematical and conceptual structure of classical field
theories shows serious inconsistencies in their common basis. In other words,
we claim in this work to have come across two severe mathematical blunders in
the very foundations of theoretical hydrodynamics. One of the defects concerns
the traditional treatment of time derivatives in Eulerian hydrodynamic
description. The other one resides in the conventional demonstration of the
so-called Convection Theorem. Both approaches are thought to be necessary for
cross-verification of the standard differential form of continuity equation.
Any revision of these fundamental results might have important implications for
all classical field theories. Rigorous reconsideration of time derivatives in
Eulerian description shows that it evokes Minkowski metric for any flow field
domain without any previous postulation. Mathematical approach is developed
within the framework of congruences for general 4-dimensional differentiable
manifold and the final result is formulated in form of a theorem. A modified
version of the Convection Theorem provides a necessary cross-verification for a
reconsidered differential form of continuity equation. Although the approach is
developed for one-component (scalar) flow field, it can be easily generalized
to any tensor field. Some possible implications for classical electrodynamics
are also explored.Comment: no figure
On the nature of some SGRs and AXPs as rotation-powered neutron stars
We investigate the possibility that some SGRs/AXPs could be canonical
rotation-powered pulsars using realistic NS structure parameters instead of
fiducial values. We show that realistic NS parameters lowers the estimated
value of the magnetic field and radiation efficiency, ,
with respect to estimates based on fiducial NS parameters. We show that nine
SGRs/AXPs can be described as canonical pulsars driven by the NS rotational
energy, for computed in the soft (2--10~keV) X-ray band. We compute the
range of NS masses for which . We discuss the observed
hard X-ray emission in three sources of the group of nine potentially
rotation-powered NSs. This additional hard X-ray component dominates over the
soft one leading to in two of them. We show that 9
SGRs/AXPs can be rotation-powered NSs if we analyze their X-ray luminosity in
the soft 2--10~keV band. Interestingly, four of them show radio emission and
six have been associated with supernova remnants (including Swift J1834.9-0846
the first SGR observed with a surrounding wind nebula). These observations give
additional support to our results of a natural explanation of these sources in
terms of ordinary pulsars. Including the hard X-ray emission observed in three
sources of the group of potential rotation-powered NSs, this number of sources
with becomes seven. It remains open to verification
1) the accuracy of the estimated distances and 2) the possible contribution of
the associated supernova remnants to the hard X-ray emission.Comment: 11 pages, 14 figures, to appear in A&
Revealing the Archetype: The Journey of a Trecento Madonna and Child at the National Museum of Scotland
The National Museums Scotland Madonna and
Child project sought to uncover and document
the history of a fine polychrome wood carving
attributed to The Master of the Gualino St
Catherine and to prepare it for display. A new
body of knowledge has been assembled by
the interdisciplinary team. The conservation
treatment was informed by this work and led
to further discoveries: the removal of overpaint
exposing a previously hidden underdrawing.
The ethics of the treatment decisions, including
the removal of the Christ Child’s 1960s’ fingers required team dialogue and was opened up for
the public to respond to in a series of blogs.
The discovery of a rich polychromy including
gold and glazed tin has led to further plans to
produce a 3-D colour reconstruction. The collaborations
developed during this project will
facilitate future joint ventures for polychrome
sculpture in Scottish collections
Processing of attended and ignored words in the parafovea. Inhibitory aspects of semantic processing.
- …