72 research outputs found
An Optical Reflector System for the CANGAROO-II Telescope
We have developed light and durable mirrors made of CFRP (Carbon Fiber
Reinforced Plastics) laminates for the reflector of the new CANGAROO-II 7 m
telescope. The reflector has a parabolic shape (F/1.1) with a 30 m^2 effective
area which consists of 60 small spherical mirrors. The attitude of each mirror
can be remotely adjusted by stepping motors. After the first adjustment work,
the re ector offers a point image of about 0.14 degree (FWHM) on the optic
axis. The telescope has been in operation since May 1999 with an energy
threshold of ~ 300 GeV.Comment: 5 pages, 2 figures, to appear in the proceedings of the GeV-TeV
Gamma-Ray Astrophysics Workshop, "Towards a Major Atmospheric Cherenkov
Detector VI" (Snowbird, Utah, August 13-16, 1999
Fermi-LAT study of two gamma-ray binaries, HESS J0632+057 and AGL J2241+4454
GeV gamma-ray emission from two gamma-ray binary candidates, HESS J0632+057
and AGL J2241+4454, which were recently reported by H.E.S.S. and AGILE,
respectively, have been searched for using the Fermi-LAT archival dataset.
Spatial and temporal distribution of gamma-ray events are studied, but there
was no evidence for GeV gamma-ray signal from either sources.Comment: 2012 Fermi Symposium proceedings - eConf C12102
Suzaku Observation of the RCW86 Northeastern Shell
This paper reports the Suzaku results on the northeast shell of RCW 86. With
the spatial and spectral analysis, we separated the X-rays into three distinct
components; low (kT_e~0.3keV) and high (kT_e~1.8keV) temperature plasmas and a
non-thermal component, and discovered their spatial distributions are different
from each other. The low temperature plasma is dominated at the east rim,
whereas the non-thermal emission is the brightest at the northeast rim which is
spatially connected from the east rim. The high temperature plasma, found to
contain the ~6.42keV line (K alpha of low-ionized iron), is enhanced at the
inward region with respect to the east rim and has no spatial correlation with
the non-thermal X-ray (the northeast). The Fe-Kalpha line, therefore, is not
related to the non-thermal emission but originates from Fe-rich ejecta heated
to the high temperatures by the reverse shock. Since the metal abundances of
the low temperature plasma are sub-solar, the most possible origin of this
component is interstellar medium heated by a blast wave. The non-thermal X-ray,
which has a power-law index of ~2.8, is likely to be synchrotron emission. A
possible scenario to explain these morphologies and spectra is: A fast moving
blast wave in a thin cavity of OB association collided with a dense
interstellar medium or cloud at the east region very recently. As the result,
the reverse shock in this interior decelerated, and arrived at the Fe-rich
region of the ejecta and heated it. In the northeast rim, on the other hand,
the blast wave is still moving fast, and accelerated high energy electrons to
emit synchrotron X-rays.Comment: 13 pages, 5 figures (9 figure files), accepted for publication in
PAS
Hydrodynamic Interaction between the Be Star and the Pulsar in the TeV Binary PSR B1259-63/LS 2883
We study the interaction between the Be star and the pulsar in the TeV binary
PSR B1259-63/LS 2883, using 3-D SPH simulations of the tidal and wind
interactions in this Be-pulsar system. We first run a simulation without pulsar
wind nor Be wind, taking into account only the gravitational effect of the
pulsar on the Be disk. In this simulation, the gas particles are ejected at a
constant rate from the equatorial surface of the Be star, which is tilted in a
direction consistent with multi-waveband observations. We run the simulation
until the Be disk is fully developed and starts to repeat a regular tidal
interaction with the pulsar. Then, we turn on the pulsar wind and the Be wind.
We run two simulations with different wind mass-loss rates for the Be star, one
for a B2V type and the other for a significantly earlier spectral type.
Although the global shape of the interaction surface between the pulsar wind
and the Be wind agrees with the analytical solution, the effect of the pulsar
wind on the Be disk is profound. The pulsar wind strips off an outer part of
the Be disk, truncating the disk at a radius significantly smaller than the
pulsar orbit. Our results, therefore, rule out the idea that the pulsar passes
through the Be disk around periastron, which has been assumed in the previous
studies. It also turns out that the location of the contact discontinuity can
be significantly different between phases when the pulsar wind directly hits
the Be disk and those when the pulsar wind collides with the Be wind. It is
thus important to adequately take into account the circumstellar environment of
the Be star, in order to construct a satisfactory model for this prototypical
TeV binary.Comment: 10 pages, 5 figures, accepted for publication in PAS
New Particle Identification Approach with Convolutional Neural Networks in GAPS
The General Antiparticle Spectrometer (GAPS) is a balloon-borne experiment
that aims to measure low-energy cosmic-ray antiparticles. GAPS has developed a
new antiparticle identification technique based on exotic atom formation caused
by incident particles, which is achieved by ten layers of Si(Li) detector
tracker in GAPS. The conventional analysis uses the physical quantities of the
reconstructed incident and secondary particles. In parallel with this, we have
developed a complementary approach based on deep neural networks. This paper
presents a new convolutional neural network (CNN) technique. A
three-dimensional CNN takes energy depositions as three-dimensional inputs and
learns to identify their positional/energy correlations. The combination of the
physical quantities and the CNN technique is also investigated. The findings
show that the new technique outperforms existing machine learning-based methods
in particle identification.Comment: 7 pages, 10 figure
Thermal Control System to Easily Cool the GAPS Balloon-borne Instrument on the Ground
This study developed a novel thermal control system to cool detectors of the
General AntiParticle Spectrometer (GAPS) before its flights. GAPS is a
balloon-borne cosmic-ray observation experiment. In its payload, GAPS contains
over 1000 silicon detectors that must be cooled below -40^{\circ}\mbox{C}.
All detectors are thermally coupled to a unique heat-pipe system (HPS) that
transfers heat from the detectors to a radiator. The radiator is designed to be
cooled below -50^{\circ}\mbox{C} during the flight by exposure to space. The
pre-flight state of the detectors is checked on the ground at 1 atm and ambient
room temperature, but the radiator cannot be similarly cooled. The authors have
developed a ground cooling system (GCS) to chill the detectors for ground
testing. The GCS consists of a cold plate, a chiller, and insulating foam. The
cold plate is designed to be attached to the radiator and cooled by a coolant
pumped by the chiller. The payload configuration, including the HPS, can be the
same as that of the flight. The GCS design was validated by thermal tests using
a scale model. The GCS design is simple and provides a practical guideline,
including a simple estimation of appropriate thermal insulation thickness,
which can be easily adapted to other applications.Comment: 8 pages, 14 figures, 3 table
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