237 research outputs found
Study of the Large-scale Temperature Structure of the Perseus Cluster with Suzaku
We report on a study of the large-scale temperature structure of the Perseus
cluster with Suzaku, using the observational data of four pointings of 30'
offset regions, together with the data from the central region. Thanks to the
Hard X-ray Detector (HXD-PIN: 10 - 60 keV), Suzaku can determine the
temperature of hot galaxy clusters. We performed the spectral analysis, by
considering the temperature structure and the collimator response of the PIN
correctly. As a result, we found that the upper limit of the temperature in the
outer region is 14 keV, and an extremely hot gas, which was reported for
RXJ 1347.5-1145 and A 3667, was not found in the Perseus cluster. This
indicates that the Perseus cluster has not recently experienced a major merger.Comment: 17 pages, 25 figures, accepted for Publications of the Astronomical
Society of Japan, references adde
X-Ray View of the Shock Front in the Merging Cluster Abell 3376 with Suzaku
We report on a Suzaku measurement of the shock feature associated with the
western radio relic in the merging cluster A3376. The temperature profile is
characterized by an almost flat radial shape with kT ~ 4 keV within 0.5 r200
and a rise by about 1 keV inside the radio relic. Across the relic region
(0.6-0.8 r200), the temperature shows a remarkable drop from about 4.7 keV to
1.3 keV. This is a clear evidence that the radio relic really corresponds to a
shock front possibly caused by a past major merger. The observed sharp changes
of the temperature and electron density indicate the Mach number M~3. The
radial entropy profile is flatter than the prediction (r^1.1) of numerical
simulations within 0.5 r200}, and becomes steeper around the relic region.
These observed features and time-scale estimation consistently imply that the
ICM around the radio relic has experienced a merger shock and is in the middle
of the process of dynamical and thermal relaxation.Comment: Accepted for publication in PASJ (12 pages, 6 figures
ASCA Observations of Three Shakhbazyan's Compact Groups of Galaxies
X-ray observations of three Shakhbazyan's Compact Groups of Galaxies, SCGG
202, SCGG 205, and SCGG 223, are presented for the first time. Extended X-ray
emission was detected from SCGG 202 and SCGG 223 with 0.5-2 keV luminosity of
1E42 erg/s and 3E42 erg/s (for H_0 = 75 km/s/Mpc), respectively, while no
significant emission was detected from SCGG 205 with an upper limit of 0.7E42
erg/s. The X-ray spectra of SCGG 202 and SCGG 223 can be described with
thin-thermal plasma emission with temperature about 1 keV. X-ray properties of
SCGG 202 and SCGG 223 are in good agreement with those of other known groups of
galaxies, proving the physical nature of their grouping.Comment: text 8 pages, 4 figures, submitted to PAS
An autoencoder-classified cluster of SARS-CoV-2 strain with two mutations in helicase
Using an autoencoder-based analysis to classify genomes of SARS-CoV-2 coronaviruses, we found a cluster consisting only of a specific genotype with two mutations in the helicase. This virus genotype, called C-type SARS-CoV-2, was almost exclusively prevalent in the United States from March to July 2020. This type of virus, characterized by a pair of the C17747T (P504L) and A17858G (Y541C) mutations on the nsp13 gene, had never been highly prevalent at any other time or in any other part of the world. In the U.S., Washington State was the center of the epidemic, and the C-type viruses, along with the viruses with wild-type helicase, seemed to have aroused the pandemic. In Washington State, USA, the CoViD-19 epidemic during the first two months of the year, starting at the end of February 2020, was mainly caused by the type-C virus. During this period, the infection spread rapidly; from May onwards, the number of viruses with wild-type helicases became higher than that of type-C viruses, and no type-C viruses have been collected since early July. The involvement of the helicase in this COVID-19 disease was discussed
Detection of Excess Hard X-ray Emission from the Group of Galaxies HCG62
From the group of galaxies HCG62, we detected an excess hard X-ray emission
in energies above keV with \A SCA. The excess emission is spatially
extended up to from the group center, and somewhat enhanced toward
north. Its spectrum can be represented by either a power-law of photon index
0.8-2.7, or a Bremsstrahlung of temperature keV. In the 2-10 keV range,
the observed hard X-ray flux, erg cm
s, implies a luminosity of erg s for a
Hubble constant of 50 km s Mpc. The emission is thus too luminous
to be attributed to X-ray binaries in the memb er galaxies. We discuss possible
origin of the hard X-ray emission.Comment: 6 pages, 3 Postscript figures, uses emulateapj.sty. Accepted for
publication in the Astrophysical Journal Letter
Development of a Si/CdTe semiconductor Compton telescope
We are developing a Compton telescope based on high resolution Si and CdTe
imaging devices in order to obtain a high sensitivity astrophysical observation
in sub-MeV gamma-ray region. In this paper, recent results from the prototype
Si/CdTe semiconductor Compton telescope are reported. The Compton telescope
consists of a double-sided Si strip detector (DSSD) and CdTe pixel detectors,
combined with low noise analog LSI, VA32TA. With this detector, we obtained
Compton reconstructed images and spectra from line gamma-rays ranging from 81
keV up to 356 keV. The energy resolution is 3.8 keV and 7.9 keV at 122 keV and
356 keV, respectively, and the angular resolution is 9.9 degrees and 5.7
degrees at 122 keV and 356 keV, respectively.Comment: 12 pages, 14 figures, submitted to SPIE conference proceedings vol.
5501, "High-Energy Detectors in Astronomy", Glasgow UK, 6/21-6/24 200
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