23 research outputs found
The Suzaku Observations of SS Cygni in Quiescence and Outburst
We present results from the Suzaku observations of the dwarf nova SS Cyg in
quiescence and outburst in 2005 November. Owing to high sensitivity of the HXD
PIN detector and high spectral resolution of the XIS, we have determined
parameters of the plasma with unprecedented precision. The maximum temperature
of the plasma in quiescence 20.4 +4.0-2.6 (stat.) +/- 3.0 (sys.) keV is
significantly higher than that in outburst 6.0 +0.2-1.3 keV. The elemental
abundances are close to the solar ones for the medium-Z elements (Si, S, Ar)
whereas they decline both in lighter and heavier elements. Those of oxygen and
iron are 0.46 and 0.37 solar, respectively. That of carbon is exceptionally
high and 2 solar at least. The solid angle of the reflector subtending over the
optically thin thermal plasma is Omega/2\pi = 1.7+/-0.2 (stat.) +/-0.1 (sys.)
in quiescence. A 6.4 keV iron Ka line is resolved into a narrow and broad
components. These facts indicate that both the white dwarf and the accretion
disk contribute to the continuum reflection and the 6.4 keV iron Ka line. We
consider the standard optically thin boundary layer as the most plausible
picture for the plasma configuration in quiescence. The solid angle of the
reflector in outburst Omega/2\pi = 0.9 +0.5-0.4 and a broad 6.4 keV iron line
indicates that the reflection in outburst originates from the accretion disk
and an equatorial accretion belt. From the energy width of the 6.4 keV line, we
consider the optically thin thermal plasma in outburst as being distributed on
the accretion disk like solar coronae.Comment: 28 pages, 15 figures, accepted for publication in PASJ Suzaku 3rd
special issue Pdf of this paper can be downloaded from
http://www.astro.isas.jaxa.jp/~ishida/Papers/sscyg_sub2.pd
Aortic dissection caused by aortitis associated with hepatitis C virus–related cryoglobulinemia
Suzaku Discovery of Hard X-ray Pulsations from the Rotating Magnetized White Dwarf, AE Aquarii
The fast rotating magnetized white dwarf, AE Aquarii, was observed with
Suzaku, in October 2005 and October 2006 with exposures of 53.1 and 42.4 ks,
respectively. In addition to clear spin modulation in the 0.5--10 keV band of
the XIS data at the barycentric period of 33.0769 \pm 0.0001 s, the 10--30 keV
HXD data in the second half of the 2005 observation also showed statistically
significant periodic signals at a consistent period. On that occasion, the
spin-folded HXD light curve exhibited two sharp spikes separated by about 0.2
cycles in phase, in contrast to approximately sinusoidal profiles observed in
energies below about 4 keV. The folded 4--10 keV XIS light curves are
understood as a superposition of those two types of pulse profiles. The phase
averaged 1.5--10 keV spectra can be reproduced by two thermal components with
temperatures of keV and keV, but
the 12-25 keV HXD data show a significant excess above the extrapolated model.
This excess can be explained by either a power-law model with photon index of
or a third thermal component with a temperature of
keV. At a distance of 102 pc, the 4--30 keV luminosities of
the thermal and the additional components become and
erg s, respectively. The latter
corresponds to 0.09% of the spin down energy of the object. Possible emission
mechanisms of the hard pulsations are discussed, including in particular
non-thermal ones.Comment: Accepted for publication on PASJ Vol.60, No.2, 2008 see Press Release
page(http://www.heal.phy.saitama-u.ac.jp/~terada/01work/press_release2008/index_e.html
Mitral valve replacement via right thoracotomy approach for prevention of mediastinitis in a female patient with long-term uncontrolled diabetes mellitus: a case report
A 76-year-old woman with a history of percutaneous transvenous mitral commissurotomy and repeated hospital admissions due to heart failure was referred for an operation for severe mitral valve stenosis. She presented with hypertension, hyperlipidemia and cerebral infarction with stenosis of right internal carotid artery, retinopathy, neuropathy and nephropathy caused by long-term uncontrolled diabetes mellitus, hemoglobin A1c of 9.4%, and New York Heart Association (NYHA) functional classification of 3/4. Echocardiography revealed severe mitral valve stenosis with mitral valve area of 0.6 cm2, moderate tricuspid valve regurgitation, and dilatation of the left atrium. Taking into consideration the NYHA functional classification and severe mitral valve stenosis, an immediate surgical intervention designed to prevent mediastinitis was performed. The approach was via the right 4th thoracotomy, as conventional sternotomy would raise the risk of mediastinitis. Postoperative antibiotics were administered intravenously for 2 days, and signs of infection were not recognized
Impact of tricuspid regurgitation after redo valvular surgery on survival in patients with previous mitral valve replacement
ObjectiveThe impact on survival of tricuspid regurgitation (TR) after redo valvular surgery in patients with previous mitral valve replacement (MVR) is unclear.MethodsWe retrospectively analyzed 118 consecutive patients undergoing redo valvular surgery after MVR over a 20-year period. We determined the impact of TR after redo valvular surgery on survival and clinical factors that were associated with TR of 2+ or higher. The mean follow-up period was 7.1 ± 6.5 years.ResultsOverall hospital mortality was 8.5% (10 of 118). Logistic regression analysis revealed that cardiopulmonary bypass duration (odds ratio, 1.025; P = .0270) was an independent risk factor for hospital death. There were 25 late deaths. Survival after 5, 10, and 15 years was 77.5% ± 4.2%, 68.5% ± 5.1%, and 58.8% ± 6.3%, respectively. Multivariate Cox regression analysis showed that TR less than 2+ at discharge was a predictor of late survival (hazard ratio, 0.043; P < .0382), whereas age, female sex, left ventricular end-diastolic dimension, and cardiopulmonary bypass duration were predictors of late death. Survival for patients with TR less than 2+ versus 2+ or higher after redo surgery were 91.4% ± 3.4% versus 59.5% ± 11.9% at 5 years and 81.1% ± 5.3% versus 52.1% ± 12.5% at 10 years, respectively (log-rank P = .0285). Logistic regression analysis indicated that preoperative TR (odds ratio, 3.718; P = .0044) and chronic obstructive pulmonary disease (odds ratio, 28.576; P = .0154) were independent risk factors for TR of 2+ or higher after redo surgery.ConclusionsSurvival in patients with TR of 2+ or higher after redo valvular surgery was poor. The results of this study suggest that it is important to maintain a postoperative TR less than 2+ to improve long-term survival