23,754 research outputs found
An X-Ray Detection Possibility of Star-Formation-Bursting Proto-Elliptical Galaxies
A possibility to detect X-rays from star-formation burst activities in
proto-elliptical galaxies is considered. The X-ray flux of an emission due to
inverse Compton scattering of the cosmic microwave background (CMB) by high
energy electrons accelerated in SNRs is shown to increase as z increases far
beyond unity, since the local CMB flux largely increases in association with a
z-increase. The flux is estimated for the case of a very high rate of type II
supernovae at an initial star formation burst of a proto-elliptical galaxy and
is found to be detectable with a future large X-ray telescope such as intended
in the XEUS mission.Comment: 4 pages, 1 figure, will appear in PAS
X-ray and Radio Follow-up Observations of High-Redshift Blazar Candidates in the Fermi-LAT Unassociated Source Population
We report on the results of X-ray and radio follow-up observations of two GeV
gamma-ray sources 2FGL J0923.5+1508 and 2FGL J1502.1+5548, selected as
candidates for high-redshift blazars from unassociated sources in the {\it
Fermi} Large Area Telescope Second Source Catalog. We utilize the Suzaku
satellite and the VLBI Exploration of Radio Astrometry (VERA) telescopes for
X-ray and radio observations, respectively. For 2FGL J0923.5+1508, a possible
radio counterpart NVSS J092357+150518 is found at 1.4 GHz from an existing
catalog, but we do not detect any X-ray emission from it and derive a flux
upper limit 1.37 10 erg cm
s. Radio observations at 6.7 GHz also result in an upper limit of
19 mJy, implying a steep radio spectrum that is not
expected for a blazar. On the other hand, we detect X-rays from NVSS
J150229+555204, the potential 1.4 GHz radio counterpart of 2FGL J1502.1+5548.
The X-ray spectrum can be fitted with an absorbed power-law model with a photon
index =1.8 and the unabsorbed flux is =4.3 10 erg cm s. Moreover,
we detect unresolved radio emission at 6.7 GHz with flux =30.1
mJy, indicating a compact, flat-spectrum radio source. If NVSS J150229+555204
is indeed associated with 2FGL J1502.1+5548, we find that its multiwavelength
spectrum is consistent with a blazar at redshift .Comment: 24 pages, 7 figures, 6 tables, accepted for publication in Ap
Measurement of the thickness of an insensitive surface layer of a PIN photodiode
We measured the thickness of an insensitive surface layer of a PIN
photodiode, Hamamatsu S3590-06, used in the Tokyo Axion Helioscope. We made
alpha-particles impinge on the PIN photodiode in various incidence angles and
measured the pulse height to estimate the thickness of the insensitive surface
layer. This measurement showed its thickness was on the
assumption that the insensitive layer consisted of Si. We calculated the peak
detection efficiency for low energy x-rays in consideration of the insensitive
layer and escape of x-rays and Auger electrons. This result showed the
efficiency for 4-10keV x-rays was more than 95%.Comment: 7 pages, 7 figure
A new method of alpha ray measurement using a Quadrupole Mass Spectrometer
We propose a new method of alpha()-ray measurement that detects
helium atoms with a Quadrupole Mass Spectrometer(QMS). A demonstration is
undertaken with a plastic-covered Am -emitting source to detect
-rays stopped in the capsule. We successfully detect helium atoms that
diffuse out of the capsule by accumulating them for one to 20 hours in a closed
chamber. The detected amount is found to be proportional to the accumulation
time. Our method is applicable to probe -emitting radioactivity in bulk
material.Comment: 8 pages, 6 figure
Influence of magnetic impurities on charge transport in diffusive-normal-metal / superconductor junctions
Charge transport in the diffusive normal metal (DN) / insulator / - and -wave superconductor junctions is studied in the presence of magnetic
impurities in DN in the framework of the quasiclassical Usadel equations with
the generalized boundary conditions. The cases of - and d-wave
superconducting electrodes are considered. The junction conductance is
calculated as a function of a bias voltage for various parameters of the DN
metal: resistivity, Thouless energy, the magnetic impurity scattering rate and
the transparency of the insulating barrier between DN and a superconductor. It
is shown that the proximity effect is suppressed by magnetic impurity
scattering in DN for any value of the barrier transparency. In low-transparent
s-wave junctions this leads to the suppression of the normalized zero-bias
conductance. In contrast to that, in high transparent junctions zero-bias
conductance is enhanced by magnetic impurity scattering. The physical origin of
this effect is discussed. For the d-wave junctions, the dependence on the
misorientation angle between the interface normal and the crystal axis
of a superconductor is studied. The zero-bias conductance peak is suppressed by
the magnetic impurity scattering only for low transparent junctions with
. In other cases the conductance of the d-wave junctions does
not depend on the magnetic impurity scattering due to strong suppression of the
proximity effect by the midgap Andreev resonant states.Comment: 11 pages, 13 figures;d-wave case adde
An x-ray detector using PIN photodiodes for the axion helioscope
An x-ray detector for a solar axion search was developed. The detector is
operated at 60K in a cryostat of a superconducting magnet. Special care was
paid to microphonic noise immunity and mechanical structure against thermal
contraction. The detector consists of an array of PIN photodiodes and tailor
made preamplifiers. The size of each PIN photodiode is $11\times 11\times 0.5\
{\rm mm^3}$ and 16 pieces are used for the detector. The detector consists of
two parts, the front-end part being operated at a temperature of 60K and the
main part in room temperature. Under these circumstances, the detector achieved
1.0 keV resolution in FWHM, 2.5 keV threshold and 6\times 10^{-5} counts
sec^{-1} keV^{-1} cm^{-2} background level.Comment: 8 pages, 5 figures, submitted to Nucl. Instr. Meth.
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