617 research outputs found
X-Ray Observations of the Supernova Remnant W28 with Suzaku --- I. Spectral Study of the Recombining Plasma
We present the Suzaku results of the mixed-morphology supernova remnant W28.
The X-ray spectra of the central region of W28 exhibit many bright emission
lines from highly ionized atoms. An optically thin thermal plasma in
collisional ionization equilibrium, either of single-temperature or
multi-temperature failed to reproduce the data with line-like and bump-like
residuals at the Si Lyman energy and at 2.4--5.0 keV, respectively. The
bumps probably correspond to radiative recombination continua from He-like Si
and S. A simple recombining plasma model nicely fit the bump structures, but
failed to fit low energy bands. The overall spectra can be fit with a
multi-ionization temperature plasma with a common electron temperature. The
multi-ionization temperatures are interpreted as elemental difference of
ionization and recombination timescales. These results prefer the rarefaction
scenario for the origin of the recombining plasma.Comment: Accepted for publication in PASJ; Vol.64 No. 4 (8 pages, 5 figures
Relative stabilities of metastable states of convecting charged-fluid systems by computer simulation
X-Ray Observations of the W51 Complex with Suzaku
We present a detailed analysis of the X-ray emission from the middle-aged
supernova remnant W51C and star-forming region W51B with Suzaku. The soft X-ray
emission from W51C is well represented by an optically thin thermal plasma in
the non-equilibrium ionization state with a temperature of 0.7 keV. The
elemental abundance of Mg is significantly higher than the solar value. We find
no significant feature of an over-ionized plasma in W51C. The hard X-ray
emission is spatially coincident with the molecular clouds associated with
W51B, overlapping with W51C. The spectrum is represented by an optically thin
thermal plasma with a temperature of 5 keV or a powerlaw model with a
photon index of 2.2. The emission probably has diffuse nature since its
luminosity of 1 erg s in the 0.5-10 keV band cannot be
explained by the emission from point sources in this region. We discuss the
possibility that the hard X-ray emission comes from stellar winds of OB stars
in W51B or accelerated particles in W51C.Comment: 11 pages, 5 figures, accepted for publication in PAS
Discovery of Enhanced Radiative Recombination Continua of He-like Iron and Calcium from IC 443 and Its Implications
We present deep observations of the Galactic supernova remnant IC 443 with
the {\it Suzaku X-ray satellite}. We find prominent K-shell lines from iron and
nickel, together with a triangle residual at 8--10~keV, which corresponds to
the energy of the radiative recombination continuum (RRC) of He-like iron. In
addition, the wavy residuals have been seen at 5.1 and 5.5~keV. We
confirm that the residuals show the first enhanced RRCs of He- and H-like
calcium found in supernova remnants. These facts provide robust evidence for
the recombining plasma. We reproduce the plasma in the 3.7--10~keV band using a
recombining plasma model at the electron temperature 0.65~keV. The
recombination parameter ( is electron density and
is elapsed time after formation of a recombining plasma) and abundances of iron
and nickel are strongly correlated, and hence the errors are large. On the
other hand, the ratio of nickel to iron relative to the solar abundances is
well constrained to 11 (1). A possibility is that the large
abundance ratio is a result of an asymmetric explosion of the progenitor star.Comment: 4 pages, 5 figures, published in Ap
New Identification of the Mixed-Morphology Supernova Remnant G298.6-0.0 with Possible Gamma-ray Association
We present an X-ray analysis on the Galactic supernova remnant (SNR)
G298.6-0.0 with Suzaku. The X-ray image shows a center-filled structure inside
the radio shell, implying this SNR is categorized as a mixed-morphology (MM)
SNR. The spectrum is well reproduced by a single temperature plasma model in
ionization equilibrium, with a temperature of 0.78 (0.70-0.87) keV. The total
plasma mass of 30 solar mass indicates that the plasma has interstellar medium
origin. The association with a GeV gamma-ray source 3FGL J1214.0-6236 on the
shell of the SNR is discussed, in comparison with other MM SNRs with GeV
gamma-ray associations. It is found that the flux ratio between
absorption-corrected thermal X-rays and GeV gamma-rays decreases as the MM SNRs
evolve to larger physical sizes. The absorption-corrected X-ray flux of
G298.6-0.0 and the GeV gamma-ray flux of 3FGL J1214.0-6236 closely follow this
trend, implying that 3FGL J1214.0-6236 is likely to be the GeV counterpart of
G298.6-0.0.Comment: 11 pages, 6 figures, PASJ, in pres
Risk factors for primary open-angle glaucoma in Japanese subjects attending community health screenings
Makoto Ishikawa, Yu Sawada, Noriko Sato, Takeshi YoshitomiDepartment of Ophthalmology, Akita Graduate University School of Medicine, Akita, JapanBackground/aims: To describe risk factors associated with primary open-angle glaucoma (POAG) in Japanese subjects who participated in community health screenings.Methods: Residents of Akita, Japan, participating in a community health checkup were selected to undergo a comprehensive ophthalmic examination. Glaucoma was diagnosed based on optic disk appearance, perimetric results, and other ocular findings. Systemic blood pressure and intraocular pressure were measured and ocular perfusion pressure was calculated. Logistic regression analysis was performed to determine risk factors for POAG patients.Results and conclusion: Of the 710 subjects examined, 26 had POAG. The estimated prevalence of POAG was 3.7%. After adjusting for age, the prevalence of POAG was similar to that found in the Tajimi Study of Japanese subjects. Multivariate logistic regression analysis demonstrated that older age (≥60 years, odds ratio [OR]: 3.49), lower diastolic blood pressure (≤58 mmHg, OR: 2.11), higher intraocular pressure (≥19 mmHg, OR: 4.12), and lower ocular perfusion pressure (≤34 mmHg, OR: 5.78) were associated with increased risk of having POAG. These findings may be relevant for identifying high risk groups.Keywords: glaucoma, community health screening, risk factor
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