8,004 research outputs found
The Second Swift BAT Gamma-Ray Burst Catalog
We present the second Swift Burst Alert Telescope (BAT) catalog of gamma-ray
bursts (GRBs), which contains 476 bursts detected by the BAT between 2004
December 19 and 2009 December 21. This catalog (hereafter the BAT2 catalog)
presents burst trigger time, location, 90% error radius, duration, fluence,
peak flux, time-averaged spectral parameters and time-resolved spectral
parameters measured by the BAT. In the correlation study of various observed
parameters extracted from the BAT prompt emission data, we distinguish among
long-duration GRBs (L-GRBs), short-duration GRBs (S-GRBs), and short-duration
GRBs with extended emission (S-GRBs with E.E.) to investigate differences in
the prompt emission properties. The fraction of L-GRBs, S-GRBs and S-GRBs with
E.E. in the catalog are 89%, 8% and 2% respectively. We compare the BAT prompt
emission properties with the BATSE, BeppoSAX and HETE-2 GRB samples. We also
correlate the observed prompt emission properties with the redshifts for the
GRBs with known redshift. The BAT T90 and T50 durations peak at 70 s and 30 s,
respectively. We confirm that the spectra of the BAT S-GRBs are generally
harder than those of the L-GRBs. The time-averaged spectra of the BAT S-GRBs
with E.E. are similar to those of the L-GRBs. Whereas, the spectra of the
initial short spikes of the S-GRBs with E.E. are similar to those of the
S-GRBs. We show that the BAT GRB samples are significantly softer than the
BATSE bright GRBs, and that the time-averaged Epeak of the BAT GRBs peaks at 80
keV which is significantly lower energy than those of the BATSE sample which
peak at 320 keV. The time-averaged spectral properties of the BAT GRB sample
are similar to those of the HETE-2 GRB samples. By time-resolved spectral
analysis, we find that only 10% of the BAT observed photon indices are outside
the allowed region of the synchrotron shock model.Comment: 65 pages, 33 figures, 13 tables, Accepted in ApJS, Nine
machine-readable tables are available at
http://swift.gsfc.nasa.gov/docs/swift/results/bat2_catalog
Self-Consistent Velocity Dependent Effective Interactions
The theory of self-consistent effective interactions in nuclei is extended
for a system with a velocity dependent mean potential. By means of the field
coupling method, we present a general prescription to derive effective
interactions which are consistent with the mean potential. For a deformed
system with the conventional pairing field, the velocity dependent effective
interactions are derived as the multipole pairing interactions in
doubly-stretched coordinates. They are applied to the microscopic analysis of
the giant dipole resonances (GDR's) of , the first excited
states of Sn isotopes and the first excited states of Mo isotopes.
It is clarified that the interactions play crucial roles in describing the
splitting and structure of GDR peaks, in restoring the energy weighted sum
rule, and in reducing the values of .Comment: 35 pages, RevTeX, 7 figures (available upon request), to appear in
Phys.Rev.
Generalized sine-Gordon/massive Thirring models and soliton/particle correspondences
We consider a real Lagrangian off-critical submodel describing the soliton
sector of the so-called conformal affine Toda model coupled to
matter fields (CATM). The theory is treated as a constrained system in the
context of Faddeev-Jackiw and the symplectic schemes. We exhibit the parent
Lagrangian nature of the model from which generalizations of the sine-Gordon
(GSG) or the massive Thirring (GMT) models are derivable. The dual description
of the model is further emphasized by providing the relationships between
bilinears of GMT spinors and relevant expressions of the GSG fields. In this
way we exhibit the strong/weak coupling phases and the (generalized)
soliton/particle correspondences of the model. The case is also
outlined.Comment: 22 pages, LaTex, some comments and references added, conclusions
unchanged, to appear in J. Math. Phy
A year in the life of GW170817: the rise and fall of a structured jet from a binary neutron star merger
We present the results of our year-long afterglow monitoring of GW170817, the
first binary neutron star (NS) merger detected by advanced LIGO and advanced
Virgo. New observations with the Australian Telescope Compact Array (ATCA) and
the Chandra X-ray Telescope were used to constrain its late-time behavior. The
broadband emission, from radio to X-rays, is well-described by a simple
power-law spectrum with index ~0.585 at all epochs. After an initial shallow
rise ~t^0.9, the afterglow displayed a smooth turn-over, reaching a peak X-ray
luminosity of ~5e39 erg/s at 160 d, and has now entered a phase of rapid
decline ~t^(-2). The latest temporal trend challenges most models of choked
jet/cocoon systems, and is instead consistent with the emergence of a
relativistic structured jet seen at an angle of ~22 deg from its axis. Within
such model, the properties of the explosion (such as its blastwave energy
E_K~2E50 erg, jet width theta_c~4 deg, and ambient density n~3E-3 cm^(-3)) fit
well within the range of properties of cosmological short GRBs.Comment: 11 pages, 8 figures, 2 tables, MNRAS, in press. Final version, minor
changes only relative to original submission dated 21 August 201
Magnetic translation groups in an n-dimensional torus
A charged particle in a uniform magnetic field in a two-dimensional torus has
a discrete noncommutative translation symmetry instead of a continuous
commutative translation symmetry. We study topology and symmetry of a particle
in a magnetic field in a torus of arbitrary dimensions. The magnetic
translation group (MTG) is defined as a group of translations that leave the
gauge field invariant. We show that the MTG on an n-dimensional torus is
isomorphic to a central extension of a cyclic group Z_{nu_1} x ... x
Z_{nu_{2l}} x T^m by U(1) with 2l+m=n. We construct and classify irreducible
unitary representations of the MTG on a three-torus and apply the
representation theory to three examples. We shortly describe a representation
theory for a general n-torus. The MTG on an n-torus can be regarded as a
generalization of the so-called noncommutative torus.Comment: 29 pages, LaTeX2e, title changed, re-organized, to be published in
Journal of Mathematical Physic
Galerkin FEM for fractional order parabolic equations with initial data in
We investigate semi-discrete numerical schemes based on the standard Galerkin
and lumped mass Galerkin finite element methods for an initial-boundary value
problem for homogeneous fractional diffusion problems with non-smooth initial
data. We assume that , is a convex
polygonal (polyhedral) domain. We theoretically justify optimal order error
estimates in - and -norms for initial data in . We confirm our theoretical findings with a number of numerical tests
that include initial data being a Dirac -function supported on a
-dimensional manifold.Comment: 13 pages, 3 figure
Linkage mapping reveals sex-dimorphic map distances in a passerine bird
Linkage maps are lacking for many highly influential model organisms in evolutionary research, including all passerine birds. Consequently, their full potential as research models is severely hampered. Here, we provide a partial linkage map and give novel estimates of sex-specific recombination rates in a passerine bird, the great reed warbler (Acrocephalus arundinaceus). Linkage analysis of genotypic data at 51 autosomal microsatellites and seven markers on the Z-chromosome (one of the sex chromosomes) from an extended pedigree resulted in 12 linkage groups with 2â8 loci. A striking feature of the map was the pronounced sex-dimorphism: males had a substantially lower recombination rate than females, which resulted in a suppressed autosomal map in males (sum of linkage groups: 110.2cM) compared to females (237.2cM; female/male map ratio: 2.15). The sex-specific recombination rates will facilitate the building of a denser linkage map and cast light on hypotheses about sex-specific recombination rates
Epeak estimator for Gamma-Ray Bursts Observed by the Swift Burst Alert Telescope
We report a correlation based on a spectral simulation study of the prompt
emission spectra of gamma-ray bursts (GRBs) detected by the Swift Burst Alert
Telescope (BAT). The correlation is between the Epeak energy, which is the peak
energy in the \nu F_\nu spectrum, and the photon index (\Gamma) derived from a
simple power-law model. The Epeak - \Gamma relation, assuming the typical
smoothly broken power-law spectrum of GRBs, is \log Epeak = 3.258 - 0.829\Gamma
(1.3 < \Gamma < 2.3). We take into account not only a range of Epeak energies
and fluences, but also distributions for both the low-energy photon index and
the high-energy photon index in the smoothly broken power-law model. The
distribution of burst durations in the BAT GRB sample is also included in the
simulation. Our correlation is consistent with the index observed by BAT and
Epeak measured by the BAT, and by other GRB instruments. Since about 85% of
GRBs observed by the BAT are acceptably fit with the simple power-law model
because of the relatively narrow energy range of the BAT, this relationship can
be used to estimate Epeak when it is located within the BAT energy range.Comment: 27 pages, 31 figures, accepted for publication in Ap
Bar-driven Transport of Molecular Gas to Galactic Centers and Its Consequences
We study the characteristics of molecular gas in the central regions of
spiral galaxies on the basis of our CO(J=1-0) imaging survey of 20 nearby
spiral galaxies using the NRO and OVRO millimeter arrays. Condensations of
molecular gas at galactic centers with sizescales < 1 kpc and CO-derived masses
M_gas(R<500pc) = 10^8 - 10^9 M_sun are found to be prevalent in the gas-rich
L^* galaxies. Moreover, the degree of gas concentration to the central kpc is
found to be higher in barred systems than in unbarred galaxies. This is the
first statistical evidence for the higher central concentration of molecular
gas in barred galaxies, and it strongly supports the theory of bar-driven gas
transport. It is most likely that more than half of molecular gas within the
central kpc of a barred galaxy was transported there from outside by the bar.
The supply of gas has exceeded the consumption of gas by star formation in the
central kpc, resulting in the excess gas in the centers of barred systems. The
mean rate of gas inflow is statistically estimated to be larger than 0.1 - 1
M_sun/yr.
The correlation between gas properties in the central kpc and the type of
nuclear spectrum (HII, LINER, or Seyfert) is investigated. A correlation is
found in which galaxies with larger gas-to-dynamical mass ratios tend to have
HII nuclear spectra, while galaxies with smaller ratios show spectra indicating
AGN.
Also, the theoretical prediction of bar-dissolution by condensation of gas to
galactic centers is observationally tested. It is suggested that the timescale
for bar dissolution is larger than 10^8 - 10^10 yr, or a bar in a L^* galaxy is
not destroyed by a condensation of 10^8 - 10^9 M_sun gas in the central kpc.Comment: AASTeX, 20 pages, 8 eps figs, ApJ in press (10 Nov. 1999 issue
A luminous blue kilonova and an off-axis jet from a compact binary merger at z=0.1341
The recent discovery of a faint gamma-ray burst (GRB) coincident with the
gravitational wave (GW) event GW 170817 revealed the existence of a population
of low-luminosity short duration gamma-ray transients produced by neutron star
mergers in the nearby Universe. These events could be routinely detected by
existing gamma-ray monitors, yet previous observations failed to identify them
without the aid of GW triggers. Here we show that GRB150101B was an analogue of
GRB170817A located at a cosmological distance. GRB 150101B was a faint short
duration GRB characterized by a bright optical counterpart and a long-lived
X-ray afterglow. These properties are unusual for standard short GRBs and are
instead consistent with an explosion viewed off-axis: the optical light is
produced by a luminous kilonova component, while the observed X-rays trace the
GRB afterglow viewed at an angle of ~13 degrees. Our findings suggest that
these properties could be common among future electromagnetic counterparts of
GW sources.Comment: 28 pages, 8 figures, 2 tables. Accepted for publicatio
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