702 research outputs found
Simulation of transient energy distributions in sub-ns streamer formation
Breakdown and streamer formation is simulated in atmospheric pressure nitrogen for a 2D planar electrode system. A PIC code with multigrid potential solver is used to simulate the evolution of the non-equilibrium ionization front on sub-nanosecond timescales. The ion and electron energy distributions are computed, accounting for the inclusion of inelastic scattering of electrons, and collisionally excited metastable production and ionization. Of particular interest is the increased production of metastable and low-energy ions and electrons when the applied field is reversed during the progress of the ionization front, giving insight into the improved species yields in nanosecond pulsed systems
X - Ray Flares and Their Connection With Prompt Emission in GRBs
We use a wavelet technique to investigate the time variations in the light
curves from a sample of GRBs detected by Fermi and Swift. We focus primarily on
the behavior of the flaring region of Swift-XRT light curves in order to
explore connections between variability time scales and pulse parameters (such
as rise and decay times, widths, strengths, and separation distributions) and
spectral lags. Tight correlations between some of these temporal features
suggest a common origin for the production of X-ray flares and the prompt
emission.Comment: 7th Huntsville Gamma-Ray Burst Symposium, GRB 2013: paper 15 in eConf
Proceedings C130414
Gamma-Ray Bursts: Temporal Scales and the Bulk Lorentz Factor
For a sample of Swift and Fermi GRBs, we show that the minimum variability
timescale and the spectral lag of the prompt emission is related to the bulk
Lorentz factor in a complex manner: For small 's, the variability
timescale exhibits a shallow (plateau) region. For large 's, the
variability timescale declines steeply as a function of (). Evidence is also presented for an intriguing
correlation between the peak times, t, of the afterglow emission and the
prompt emission variability timescale.Comment: Accepted for publication in Ap
Corrections to Gravity due to a Sol Manifold Extra Dimensional Space
The corrections to the gravitational potential due to a Sol extra dimensional
compact manifold, denoted as , are studied. The total spacetime is of
the form . The range of the Sol corrections is investigated
and compared to the range of the corrections.Comment: 13 pages, 10 figures, published versio
The Hurst Exponent of Fermi GRBs
Using a wavelet decomposition technique, we have extracted the Hurst exponent
for a sample of 46 long and 22 short Gamma-ray bursts (GRBs) detected by the
Gamma-ray Burst Monitor (GBM) aboard the Fermi satellite. This exponent is a
scaling parameter that provides a measure of long-range behavior in a time
series. The mean Hurst exponent for the short GRBs is significantly smaller
than that for the long GRBs. The separation may serve as an unbiased criterion
for distinguishing short and long GRBs.Comment: Accepted for publication in Monthly Notices of the Royal Astronomical
Societ
Optimizing astrophotonic spatial reformatters using simulated on-sky performance
One of the most useful techniques in astronomical instrumentation is image
slicing. It enables a spectrograph to have a more compact angular slit, whilst
retaining throughput and increasing resolving power. Astrophotonic components
like the photonic lanterns and photonic reformatters can be used to replace
bulk optics used so far. This study investigates the performance of such
devices using end-to-end simulations to approximate realistic on-sky
conditions. It investigates existing components, tries to optimize their
performance and aims to understand better how best to design instruments to
maximize their performance. This work complements the recent work in the field
and provides an estimation for the performance of the new components.Comment: Conference proceedings in SPIE 2018 Austin Texa
(Z)-2-Amino-3-[(E)-benzylideneamino]but-2-enedinitrile
The asymmetric unit of the title compound, C11H8N4, contains two independent molecules. In the crystal structure, intermolecular N—H⋯N hydrogen bonds link molecules into ribbons extended in the [100] direction
On multiplicities in length spectra of arithmetic hyperbolic three-orbifolds
Asymptotic laws for mean multiplicities of lengths of closed geodesics in
arithmetic hyperbolic three-orbifolds are derived. The sharpest results are
obtained for non-compact orbifolds associated with the Bianchi groups SL(2,o)
and some congruence subgroups. Similar results hold for cocompact arithmetic
quaternion groups, if a conjecture on the number of gaps in their length
spectra is true. The results related to the groups above give asymptotic lower
bounds for the mean multiplicities in length spectra of arbitrary arithmetic
hyperbolic three-orbifolds. The investigation of these multiplicities is
motivated by their sensitive effect on the eigenvalue spectrum of the
Laplace-Beltrami operator on a hyperbolic orbifold, which may be interpreted as
the Hamiltonian of a three-dimensional quantum system being strongly chaotic in
the classical limit.Comment: 29 pages, uuencoded ps. Revised version, to appear in NONLINEARIT
- …