2,090 research outputs found
INTEGRAL observations of TeV plerions
Amongst the sources seen in very high gamma-rays several are associated with
Pulsar Wind Nebulae (``TeV plerions''). The study of hard X-ray/soft gamma-ray
emission is providing an important insight into the energetic particle
population present in these objects. The unpulsed emission from pulsar/pulsar
wind nebula systems in the energy range accessible to the INTEGRAL satellite is
mainly synchrotron emission from energetic and fast cooling electrons close to
their acceleration site. Our analyses of public INTEGRAL data of known TeV
plerions detected by ground based Cherenkov telescopes indicate a deeper link
between these TeV plerions and INTEGRAL detected pulsar wind nebulae. The newly
discovered TeV plerion in the northern wing of the Kookaburra region
(G313.3+0.6 powered by the middle aged PSR J1420-6048) is found to have a
previously unknown INTEGRAL counterpart which is besides the Vela pulsar the
only middle aged pulsar detected with INTEGRAL. We do not find an INTEGRAL
counterpart of the TeV plerion associated with the X-ray PWN ``Rabbit''
G313.3+0.1 which is possibly powered by a young pulsar.Comment: 4 pages, 6 figures, proceedings of conference "The Multi-Messenger
Approach to High-Energy Gamma-ray Sources" Barcelona/Spain (2006
Charge Symmetry Violation Effects in Pion Scattering off the Deuteron
We discuss the theoretical and experimental situations for charge symmetry
violation (CSV) effects in the elastic scattering of pi+ and pi- on deuterium
(D) and 3He/3H. Accurate comparison of data for both types of targets provides
evidence for the presence of CSV effects. While there are indications of a CSV
effect in deuterium, it is much more pronounced in the case of 3He/3H. We
provide a description of the CSV effect on the deuteron in terms of single- and
double- scattering amplitudes. The Delta-mass splitting is taken into account.
Theoretical predictions are compared with existing experimental data for pi-d
scattering; a future article will speak to the pi-three nucleon case.Comment: 16 pages of RevTeX, 7 postscript figure
Electroless Plating of Thin Gold Films Directly onto Silicon Nitride Thin Films and into Micropores
A method to directly electrolessly plate silicon-rich silicon nitride with thin gold films was developed and characterized. Films with thicknesses \u3c100nm were grown at 3 and 10°C between 0.5 and 3 hours, with mean grain sizes between ~20-30nm. The method is compatible with plating free-standing ultrathin silicon nitride membranes, and we successfully plated the interior walls of micropore arrays in 200nm-thick silicon nitride membranes. The method is thus amenable to coating planar, curved, and line-of-sight-obscured silicon nitride surfaces
Search for TeV Gamma-Rays from Shell-Type Supernova Remnants
If cosmic rays with energies <100 TeV originate in the galaxy and are
accelerated in shock waves in shell-type supernova remnants (SNRs), gamma-rays
will be produced as the result of proton and electron interactions with the
local interstellar medium, and by inverse Compton emission from electrons
scattering soft photon fields. We report on observations of two supernova
remnants with the Whipple Observatory's 10 m gamma-ray telescope. No
significant detections have been made and upper limits on the >500 GeV flux are
reported. Non-thermal X-ray emission detected from one of these remnants
(Cassiopeia A) has been interpreted as synchrotron emission from electrons in
the ambient magnetic fields. Gamma-ray emission detected from the
Monoceros/Rosette Nebula region has been interpreted as evidence of cosmic-ray
acceleration. We interpret our results in the context of these observations.Comment: 4 pages, 2 figures, to appear in the proceedings of 26th
International Cosmic Ray Conference (Salt Lake City, 1999
Limits to Quantum Gravity Effects from Observations of TeV Flares in Active Galaxies
We have used data from the TeV gamma-ray flare associated with the active
galaxy Markarian 421 observed on 15 May 1996 to place bounds on the possible
energy-dependence of the speed of light in the context of an effective quantum
gravitational energy scale. The possibility of an observable time dispersion in
high energy radiation has recently received attention in the literature, with
some suggestions that the relevant energy scale could be less than the Planck
mass and perhaps as low as 10^16 GeV. The limits derived here indicate this
energy scale to be in excess of 4x10^16 GeV at the 95% confidence level. To the
best of our knowledge, this constitutes the first convincing limit on such
phenomena in this energy regime.Comment: 6 pages, including 2 figure
- …