300 research outputs found
Implications of the Visible and X-Ray Counterparts to GRB970228
The gamma-ray burst source GRB970228 has been observed after a delay of 8--12
hours in X-rays and after one day in visible and near infrared light. This
marks the first detection of emission at lower frequencies following the
gamma-ray observation of a GRB and the first detection of any visible
counterpart to a GRB. We consider possible delayed visible and X-ray emission
mechanisms, and conclude that the intrinsic gamma-ray activity continued at a
much reduced intensity for at least a day. There are hints of such continued
activity in other GRB, and future observations can decide if this is true of
GRB in general. The observed multi-band spectrum of GRB970228 agrees with the
predictions of relativistic shock theory when the flux is integrated over a
time longer than that required for a radiating electron to lose its energy.Comment: 5 pp., tex, 1 figur
Very High Energy Gamma-Ray Emission from the Blazar Markarian 421
Very high energy gamma-ray emission from the BL Lac object Markarian 421 has
been detected over three observing seasons on 59 nights between April 1992 and
June 1994 with the Whipple 10-meter imaging Cherenkov telescope. During its
initial detection in 1992, its flux above 500 GeV was
1.610photons cm s. Observations in 1993 confirmed
this level of emission. For observations made between December 1993 and April
1994, its intensity was a factor of 2.20.5 lower. Observations on 14 and
15 May, 1994 showed an increase over this quiescent level by a factor of
10 (Kerrick et al. 1995). This strong outburst suggests that 4 episodes
of increased flux measurements on similar time scales in 1992 and 1994 may be
attributed to somewhat weaker outbursts. The variability of the TeV gamma-ray
emission from Markarian 421 stands in contrast to EGRET observations (Lin et
al. 1994) which show no evidence for variability.Comment: gzip compressed tar file including LaTeX text and 4 postscript
figures (14 pages total incl. 4 tables), accepted for publication in the
Astrophysical Journal. Contact address is [email protected]
The Gamma Ray Burst section of the White Paper on the Status and Future of Very High Energy Gamma Ray Astronomy: A Brief Preliminary Report
Original paper can be found at: http://proceedings.aip.org/proceedings/ Copyright American Institute of Physics DOI: 10.1063/1.2943545otherPeer reviewe
Effect of the dynamical phases on the nonlinear amplitudes' evolution
In this Letter we show how the nonlinear evolution of a resonant triad
depends on the special combination of the modes' phases chosen according to the
resonance conditions. This phase combination is called dynamical phase. Its
evolution is studied for two integrable cases: a triad and a cluster formed by
two connected triads, using a numerical method which is fully validated by
monitoring the conserved quantities known analytically. We show that dynamical
phases, usually regarded as equal to zero or constants, play a substantial role
in the dynamics of the clusters. Indeed, some effects are (i) to diminish the
period of energy exchange within a cluster by 20 and more; (ii) to
diminish, at time scale , the variability of wave energies by 25 and
more; (iii) to generate a new time scale, , in which we observe
considerable energy exchange within a cluster, as well as a periodic behaviour
(with period ) in the variability of modes' energies. These findings can be
applied, for example, to the control of energy input, exchange and output in
Tokamaks; for explanation of some experimental results; to guide and improve
the performance of experiments; to interpret the results of numerical
simulations, etc.Comment: 5 pages, 15 figures, submitted to EP
Modeling Kelvin wave cascades in superfluid helium
We study two different types of simplified models for Kelvin wave turbulence on quantized vortex lines in superfluids near zero temperature. Our first model is obtained from a truncated expansion of the Local Induction Approximation (Truncated-LIA) and it is shown to possess the same scalings and the essential behaviour as the full Biot-Savart model, being much simpler than the later and, therefore, more amenable to theoretical and numerical investigations. The Truncated-LIA model supports six-wave interactions and dual cascades, which are clearly demonstrated via the direct numerical simulation of this model in the present paper. In particular, our simulations confirm presence of the weak turbulence regime and the theoretically predicted spectra for the direct energy cascade and the inverse wave action cascade. The second type of model we study, the Differential Approximation Model (DAM), takes a further drastic simplification by assuming locality of interactions in k-space via using a differential closure that preserves the main scalings of the Kelvin wave dynamics. DAMs are even more amenable to study and they form a useful tool by providing simple analytical solutions in the cases when extra physical effects are present, e.g. forcing by reconnections, friction dissipation and phonon radiation. We study these models numerically and test their theoretical predictions, in particular the formation of the stationary spectra, and closeness of numerics for the higher-order DAM to the analytical predictions for the lower-order DAM
IPN localizations of Konus short gamma-ray bursts
Between the launch of the \textit{GGS Wind} spacecraft in 1994 November and
the end of 2010, the Konus-\textit{Wind} experiment detected 296 short-duration
gamma-ray bursts (including 23 bursts which can be classified as short bursts
with extended emission). During this period, the IPN consisted of up to eleven
spacecraft, and using triangulation, the localizations of 271 bursts were
obtained. We present the most comprehensive IPN localization data on these
events. The short burst detection rate, 18 per year, exceeds that of many
individual experiments.Comment: Published versio
The Interplanetary Network Supplement to the Fermi GBM Catalog of Cosmic Gamma-Ray Bursts
We present Interplanetary Network (IPN) data for the gamma-ray bursts in the
first Fermi Gamma-Ray Burst Monitor (GBM) catalog. Of the 491 bursts in that
catalog, covering 2008 July 12 to 2010 July 11, 427 were observed by at least
one other instrument in the 9-spacecraft IPN. Of the 427, the localizations of
149 could be improved by arrival time analysis (or triangulation). For any
given burst observed by the GBM and one other distant spacecraft, triangulation
gives an annulus of possible arrival directions whose half-width varies between
about 0.4' and 32 degrees, depending on the intensity, time history, and
arrival direction of the burst, as well as the distance between the spacecraft.
We find that the IPN localizations intersect the 1 sigma GBM error circles in
only 52% of the cases, if no systematic uncertainty is assumed for the latter.
If a 6 degree systematic uncertainty is assumed and added in quadrature, the
two localization samples agree about 87% of the time, as would be expected. If
we then multiply the resulting error radii by a factor of 3, the two samples
agree in slightly over 98% of the cases, providing a good estimate of the GBM 3
sigma error radius. The IPN 3 sigma error boxes have areas between about 1
square arcminute and 110 square degrees, and are, on the average, a factor of
180 smaller than the corresponding GBM localizations. We identify two bursts in
the IPN/GBM sample that did not appear in the GBM catalog. In one case, the GBM
triggered on a terrestrial gamma flash, and in the other, its origin was given
as uncertain. We also discuss the sensitivity and calibration of the IPN.Comment: 52 pages, 12 figures, 4 tables. Revised version, resubmitted to the
Astrophysical Journal Supplement Series following refereeing. Figures of the
localizations in Table 3 may be found on the IPN website, at
ssl.berkeley.edu/ipn3/YYMMDD, where YY, MM, and DD are the year, month, and
day of the burst, sometimes with suffixes A or
Integrating the Fermi Gamma-Ray Burst Monitor into the 3rd Interplanetary Network
We are integrating the Fermi Gamma-Ray Burst Monitor (GBM) into the
Interplanetary Network (IPN) of Gamma-Ray Burst (GRB) detectors. With the GBM,
the IPN will comprise 9 experiments. This will 1) assist the Fermi team in
understanding and reducing their systematic localization uncertainties, 2)
reduce the sizes of the GBM and Large Area Telescope (LAT) error circles by 1
to 4 orders of magnitude, 3) facilitate the identification of GRB sources with
objects found by ground- and space-based observatories at other wavelengths,
from the radio to very high energy gamma-rays, 4) reduce the uncertainties in
associating some LAT detections of high energy photons with GBM bursts, and 5)
facilitate searches for non-electromagnetic GRB counterparts, particularly
neutrinos and gravitational radiation. We present examples and demonstrate the
synergy between Fermi and the IPN. This is a Fermi Cycle 2 Guest Investigator
project.Comment: 5 pages, 11 figures. 2009 Fermi Symposium. eConf Proceedings C09112
Comparison of Mental Toughness and Power Test Performances in High-Level Kickboxers by Competitive Success
Background
Kickboxing is a high-intensity intermittent striking combat sport, which is characterized by complex skills and tactical key actions with short duration.
Objectives
The present study compared and verified the relationship between mental toughness (MT), countermovement jump (CMJ) and medicine ball throw (MBT) power tests by outcomes of high-level kickboxers during National Championship.
Materials and Methods
Thirty two high-level male kickboxers (winner = 16 and loser = 16: 21.2 ± 3.1 years, 1.73 ± 0.07 m, and 70.2 ± 9.4 kg) were analyzed using the CMJ, MBT tests and sports mental toughness questionnaire (SMTQ; based in confidence, constancy and control subscales), before the fights of the 2015 national championship (16 bouts). In statistical analysis, Mann-Withney test and a multiple linear regression were used to compare groups and to observe relationships, respectively, P †0.05.
Results
The present results showed significant differences between losers vs. winners, respectively, of total MT (7(7;8) vs. 11(10.2;11), confidence (3(3;3) vs. 4(4;4)), constancy (2(2;2) vs. 3(3;3)), control (2(2;3) vs. 4(4;4)) subscales and MBT (4.1(4;4.3) vs. 4.6(4.4;4.8)). The multiple linear regression showed a strong associations between MT results and outcome (r = 0.89), MBT (r = 0.84) and CMJ (r = 0.73).
Conclusions
The findings suggest that MT will be more predictive of performance in those sports and in the outcome of competition.Ministry of Higher Teaching and Scientific Research, Tunisi
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