727 research outputs found
Search for serendipitous TNO occultation in X-rays
To study the population properties of small, remote objects beyond Neptune's
orbit in the outer solar system, of kilometer size or smaller, serendipitous
occultation search is so far the only way. For hectometer-sized Trans-Neptunian
Objects (TNOs), optical shadows actually disappear because of diffraction.
Observations at shorter wave lengths are needed. Here we report the effort of
TNO occultation search in X-rays using RXTE/PCA data of Sco X-1 taken from June
2007 to October 2011. No definite TNO occultation events were found in the 334
ks data. We investigate the detection efficiency dependence on the TNO size to
better define the sensible size range of our approach and suggest upper limits
to the TNO size distribution in the size range from 30 m to 300 m. A list of
X-ray sources suitable for future larger facilities to observe is proposed.Comment: Accepted to publish in MNRA
CSS1603+19: a low-mass polar near the cataclysmic variable period minimum
CSS1603+19 is a cataclysmic variable (CV) with an orbital period of 81.96
min, near the minimal period of cataclysmic variables. It is unusual in having
a strong mid-infrared excess inconsistent with thermal emission from a brown
dwarf companion. Here we present time-resolved multi-wavelength observations of
this system. WISE photometry indicates that the mid-infrared excess displays a
one-magnitude eclipsing-like variability during the orbit. We obtained
near-infrared and optical spectroscopy using Gemini, MDM and APO telescopes.
Near-infrared spectra show possible cyclotron features indicating that the
white dwarf has a magnetic field of about 5MG. Optical and near-infrared
spectra display double-peaked emission lines, with both components showing
strong radial velocity variations during the orbital period and with the broad
component leading the narrow component stably by about 0.2 of the orbital
phase. We construct a physical model informed by existing observations of the
system and determine that one component likely originates from the accretion
column onto the magnetized white dwarf in synchronous rotation with the orbital
motion and the other from the Roche overflow point. This allows us to constrain
the masses of the binary components to be for the white
dwarf accretor and for the donor. We classify the
system as an AM Herculis star, or a polar. It has likely completed its stint on
the period gap, but has not yet gone through the period bounce
Effect of diabetes on mortality and length of hospital stay in patients with renal or perinephric abscess
OBJECTIVES: We compared the risk of in-hospital mortality and the length of hospital stay between diabetic and non-diabetic patients hospitalized for renal or perinephric abscess. METHOD: The data analyzed in this study were retrieved from Taiwan's National Health Insurance claims. The risk of in-hospital mortality and the length of hospital stay were compared between 1,715 diabetic patients, hospitalized because of renal or perinephric abscess in Taiwan between 1997 and 2007, and a random sample of 477 non-diabetes patients with renal or perinephric abscess. RESULTS: The in-hospital mortality rates from renal or perinephric abscess for the diabetic patients and the non-diabetic patients were not different, at 2.3% and 3.4%, respectively. However, diabetes was significantly associated with a longer length of hospital stay among patients with renal abscess, by 3.38 days (95% confidence interval [CI]: 1.59-5.17). CONCLUSIONS: Diabetes does not increase the risk of in-hospital mortality from renal or perinephric abscess. Nevertheless, appropriate management of patients with diabetes and concurrent renal or perinephric abscess is essential to reduce the length of hospital stay
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