528 research outputs found
Development of Thick-foil and Fine-pitch GEMs with a Laser Etching Technique
We have produced thick-foil and fine-pitch gas electron multipliers (GEMs)
using a laser etching technique. To improve production yield we have employed a
new material, Liquid Crystal Polymer, instead of polyimide as an insulator
layer. The effective gain of the thick-foil GEM with a hole pitch of 140 um, a
hole diameter of 70 um, and a thickness of 100 um reached a value of 10^4 at an
applied voltage of 720 V. The measured effective gain of the thick-foil and
fine-pitch GEM (80 um pitch, 40 um diameter, and 100 um thick) was similar to
that of the thick-foil GEM. The gain stability was measured for the thick-foil
and fine-pitch GEM, showing no significant increase or decrease as a function
of elapsed time from applying the high voltage. The gain stability over 3 h of
operation was about 0.5%. Gain mapping across the GEM showed a good uniformity
with a standard deviation of about 4%. The distribution of hole diameters
across the GEM was homogeneous with a standard deviation of about 3%. There was
no clear correlation between the gain and hole diameter maps.Comment: 21 pages, 9 figure
Kiso observations for 20 GRBs in HETE-2 era
We have established a GRB follow-up observation system at Kiso observatory
(Japan) in 2001. Since the east Asian area had been blank for the GRB follow-up
observational network, this observational system is very important in studying
the temporal and spectral evolution of early afterglows. Using this system, we
have performed quick observations for optical afterglows from early phase based
on HETE-2 and INTEGRAL alerts. Thanks to the quick follow-up observation
system, we have been able to use the Kiso observatory in 20 events, and conduct
their follow-up observations in optical and near infrared wavelengths.Comment: 5 pages, 4 figure. Accepted for publication into "il nuovo cimento".
Proceeding of the 4th Rome GRB conference, eds. L. Piro, L. Amati, S. Covino,
B. Gendr
Suzaku Discovery of the Strong Radiative Recombination Continuum of Iron from the Supernova Remnant W49B
We present a hard X-ray spectrum of unprecedented quality of the Galactic
supernova remnant W49B obtained with the Suzaku satellite. The spectrum
exhibits an unusual structure consisting of a saw-edged bump above 8 keV. This
bump cannot be explained by any combination of high-temperature plasmas in
ionization equilibrium. We firmly conclude that this bump is caused by the
strong radiative recombination continuum (RRC) of iron, detected for the first
time in a supernova remnant. The electron temperature derived from the
bremsstrahlung continuum shape and the slope of the RRC is 1.5 keV. On the
other hand, the ionization temperature derived from the observed intensity
ratios between the RRC and K-alpha lines of iron is 2.7 keV. These results
indicate that the plasma is in a highly overionized state. Volume emission
measures independently determined from the fluxes of the thermal and RRC
components are consistent with each other, suggesting the same origin of these
components.Comment: 5 pages,4 figures, accepted for publication in ApJ Lette
GRBs Optical follow-up observation at Lulin observatory, Taiwan
The Lulin GRB program, using the Lulin One-meter Telescope (LOT) in Taiwan
started in July 2003. Its scientific aims are to discover optical counterparts
of XRFs and short and long GRBs, then to quickly observe them in multiple
bands. Thirteen follow-up observations were provided by LOT between July 2003
and Feb. 2005. One host galaxy was found at GRB 031203. Two optical afterglows
were detected for GRB 040924 and GRB 041006. In addition, the optical
observations of GRB 031203 and a discussion of the non-detection of the optical
afterglow of GRB 031203 are also reported in this article.Comment: 5 pages, 2 figure. Accepted for publication into "il nuovo cimento".
Proceeding of the 4th Rome GRB conference, eds. L. Piro, L. Amati, S. Covino,
B. Gendr
Early (0.3 day) R-band light curve of the optical afterglow of GRB030329
We observed the optical afterglow of the bright gamma-ray burst GRB030329 on
the nights of 2003 March 29, using the Kiso observatory (the University of
Tokyo) 1.05 m Schmidt telescope. Data were taken from March 29 13:21:26 UT to
17:43:16 (0.072 to 0.253 days after the burst), using an -band filter. The
obtained -band light curve has been fitted successfully by a single power
law function with decay index of . These results remain
unchanged when incorporating two early photometric data points at 0.065 and
0.073 days, reported by Price et al.(2003) using the SSO 40 inch telescope, and
further including RTT150 data (Burenin et al. 2003) covering at about 0.3 days.
Over the period of 0.065-0.285 days after the burst, any deviation from the
power-law decay is smaller than 0.007 mag. The temporal structure reported
by Uemura et al. (2003) does not show up in our -band light curve.Comment: 9 pages, 2 figures, 1 table, accepted for publication in ApJ
Termination of Electron Acceleration in Thundercloud by Intra/Inter-cloud Discharge
An on-ground observation program for high energy atmospheric phenomena in
winter thunderstorms along Japan Sea has been performed via measurements of
gamma-ray radiation, atmospheric electric field and low-frequency radio band.
On February 11, 2017, the radiation detectors recorded gamma-ray emission
lasting for 75 sec. The gamma-ray spectrum extended up to 20 MeV and was
reproduced by a cutoff power-law model with a photon index of
, being consistent with a Bremsstrahlung radiation from a
thundercloud (as known as a gamma-ray glow and a thunderstorm ground
enhancement). Then the gamma-ray glow was abruptly terminated with a nearby
lightning discharge. The low-frequency radio monitors, installed 50 km
away from the gamma-ray observation site recorded leader development of an
intra/inter-cloud discharge spreading over 60 km area with a 300 ms
duration. The timing of the gamma-ray termination coincided with the moment
when the leader development of the intra/inter-cloud discharge passed 0.7 km
horizontally away from the radiation monitors. The intra/inter-cloud discharge
started 15 km away from the gamma-ray observation site. Therefore, the
glow was terminated by the leader development, while it did not trigger the
lightning discharge in the present case.Comment: 12 pages, 4 figures, accepted for publication in Geophysical Research
Letter
A Suborbital Payload for Soft X-ray Spectroscopy of Extended Sources
We present a suborbital rocket payload capable of performing soft X-ray
spectroscopy on extended sources. The payload can reach resolutions of
~100(lambda/dlambda) over sources as large as 3.25 degrees in diameter in the
17-107 angstrom bandpass. This permits analysis of the overall energy balance
of nearby supernova remnants and the detailed nature of the diffuse soft X-ray
background. The main components of the instrument are: wire grid collimators,
off-plane grating arrays and gaseous electron multiplier detectors. This
payload is adaptable to longer duration orbital rockets given its comparatively
simple pointing and telemetry requirements and an abundance of potential
science targets.Comment: Accepted to Experimental Astronomy, 12 pages plus 1 table and 17
figure
Discovery of a Compact X-ray Source in the LMC Supernova Remnant N23 with Chandra
An X-ray compact source was discovered with Chandra in a supernova remnant
(SNR) N23, located in the Large Magellanic Cloud. The compact source (CXOU
J050552.3-680141) is seen in only the hard band (> 2 keV) image of N23, while
the soft band image (< 2 keV) shows diffuse emission of the SNR, with an extent
of ~60 arcsec times ~80 arcsec. The compact source is located at almost the
center of N23, and there is no identifiable object for the source from previous
observations at any other wavelength. The source spectrum is best explained by
a power-law model with a photon index of 2.2 (1.9-2.7) and an
absorption-corrected luminosity of 1.0 x 10^34 ergs s^-1 in the 0.5--10 keV
band for a distance of 50 kpc. Neither pulsation nor time variability of the
source was detected with this observation with a time resolution of 3.2 sec.
These results correspond with those of Hughes et al. (2006) who carried out
analysis independently around the same time as our work. Based on information
from the best-fit power-law model, we suggest that the source emission is most
likely from a rotation-powered pulsar and/or a pulsar wind nebula. It is
generally inferred that the progenitor of N23 is a core-collapsed massive star.
Based on information from the best-fit power-law model, we suggest that the
source emission is most likely from a rotation-powered pulsar and/or a pulsar
wind nebula. It is generally inferred that the progenitor of N23 is a
core-collapsed massive star.Comment: 16 pages, 5 figures, 1 table, Accepted to Ap
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