445 research outputs found
A Survey of Far Ultraviolet Spectroscopic Explorer Observations of Cataclysmic Variables
During its lifetime, the Far Ultraviolet Spectroscopic Explorer (FUSE) was
used to observe 99 cataclysmic variables in 211 separate observations. Here, we
present a survey of the moderate resolution (R\simeq10,000), far-ultraviolet
(905 - 1188 {\deg}A), time-averaged FUSE spectra of cataclysmic variables
(CVs). The FUSE spectra are morphologically diverse. They show contributions
from the accretion disk, the disk chromosphere, disk outflows, and the white
dwarf, but the relative contribution of each component varies widely as a
function of CV subtype, orbital period and evolutionary state, inclination,
mass accretion rate, and magnetic field strength of the white dwarf. The data
reveal information about the structure, temperature, density and mass flow
rates of the disk and disk winds, the temperature of the white dwarf and the
effects of ongoing accretion on its structure, and the long-term response of
the systems to disk outbursts. The complete atlas of time-averaged FUSE spectra
of CVs are available at the Multimission Archive at Space Telescope Science
Institute as a High Level Science Product.Comment: ApJS, in press. The extra panels in the figure sets for Figures 1 and
2 are included at the end of the manuscrip
Simulations of the Boundary Layer Between a White Dwarf and its Accretion Disk
Using a 2.5D time-dependent axisymmetric numerical code we recently
developed, we solve the full compressible Navier-Stokes equations (including an
alpha-viscosity prescription) to determine the structure of the boundary layer
between the white dwarf and the accretion disk in non-magnetic cataclysmic
varia ble systems. In this preliminary work, our numerical approach does not
include radiation. In the energy equation, we either take the dissipation
function (Phi) into account or we assumed that the energy is instantly radiated
away (Phi). For a slowly rotating non magnetized accreting white dwarf, the
accretion disk e xtends all the way to the stellar surface. There, the matter
impacts and spread s towards the poles as new matter continuously piles up
behind it. We carried out numerical simulations for different values of the
alpha viscosity parameter (alpha), corresponding to different mass accretion
rates. In the high viscosity cases (alpha=0.1), the spreading boundary layer
sets off a gravity wave in the s urface matter. The accretion flow moves
supersonically over the cusp making it s usceptible to the rapid development of
gravity wave and/or Kelvin-Helmholtz shea ring instabilities. This BL is
optically thick and extends more than 30 degrees to either side of the disk
plane after only 3/4 of a Keplerian rotation period (19s). In the low viscosity
cases (alpha=0.001), the spreading boundary layer does not set off gravity
waves and it is optically thin.Comment: final version, ApJ, in pres
Hubble space telescope STIS spectroscopy of the peculiar nova-like variables BK Lyn, V751 Cygni, and V380 Oph
We obtained Hubble STIS spectra of three nova-like variables: V751 Cygni, V380 Oph, and—the only confirmed nova-like variable known to be below the period gap—BK Lyn. In all three systems, the spectra were taken during high optical brightness state, and a luminous accretion disk dominates their far-ultraviolet (FUV) light. We assessed a lower limit of the distances by applying the infrared photometric method of Knigge. Within the limitations imposed by the poorly known system parameters (such as the inclination, white dwarf mass, and the applicability of steady state accretion disks) we obtained satisfactory fits to BK Lyn using optically thick accretion disk models with an accretion rate of for a white dwarf mass of Mwd = 1.2M and for Mwd = 0.4M. However, for the VY Scl-type nova-like variable V751 Cygni and for the SW Sex star V380 Oph, we are unable to obtain satisfactory synthetic spectral fits to the high state FUV spectra using optically thick steady state accretion disk models. The lack of FUV spectra information down to the Lyman limit hinders the extraction of information about the accreting white dwarf during the high states of these nova-like systems
Planets opening dust gaps in gas disks
We investigate the interaction of gas and dust in a protoplanetary disk in
the presence of a massive planet using a new two-fluid hydrodynamics code. In
view of future observations of planet-forming disks we focus on the condition
for gap formation in the dust fluid. While only planets more massive than 1
Jupiter mass (MJ) open up a gap in the gas disk, we find that a planet of 0.1
MJ already creates a gap in the dust disk. This makes it easier to find
lower-mass planets orbiting in their protoplanetary disk if there is a
significant population of mm-sized particles.Comment: 5 pages, 3 figures, accepted for publication in A&A Letter
Scedosporium apiospermum complex Catalase A1 and Cu-Zn SOD recombinant proteins are useful tools for serodiagnosis of Scedosporium infection
International audienc
Pharmacokinetics of voriconazole and posaconazole administered in experimental models of disseminated scedosporiosis with cerebral involvement
International audienc
Far Ultraviolet Observations of the Dwarf Nova VW Hyi in Quiescence
We present a 904-1183 A spectrum of the dwarf nova VW Hydri taken with the
Far Ultraviolet Spectroscopic Explorer during quiescence, eleven days after a
normal outburst, when the underlying white dwarf accreter is clearly exposed in
the far ultraviolet. However, model fitting show that a uniform temperature
white dwarf does not reproduce the overall spectrum, especially at the shortest
wavelengths. A better approximation to the spectrum is obtained with a model
consisting of a white dwarf and a rapidly rotating ``accretion belt''. The
white dwarf component accounts for 83% of the total flux, has a temperature of
23,000K, a v sin i = 400 km/s, and a low carbon abundance. The best-fit
accretion belt component accounts for 17% of the total flux, has a temperature
of about 48,000-50,000K, and a rotation rate Vrot sin i around 3,000-4,000
km/s. The requirement of two components in the modeling of the spectrum of VW
Hyi in quiescence helps to resolve some of the differences in interpretation of
ultraviolet spectra of VW Hyi in quiescence. However, the physical existence of
a second component (and its exact nature) in VW Hyi itself is still relatively
uncertain, given the lack of better models for spectra of the inner disk in a
quiescent dwarf nova.Comment: 6 figures, 10 printed page in the journal, to appear in APJ, 1 Sept.
2004 issue, vol. 61
Use of Sysmex XE-2100 and XE-5000 hematology analyzers for the diagnosis of malaria in a nonendemic country (France).
INTRODUCTION: Most studies dealing with automated hematology analyzers (HAs) and malaria diagnosis are conducted in endemic countries.
METHODS: We retrospectively studied cell blood counts (CBCs) performed with Sysmex XE-2100 and XE-5000 HAs in our center (Angers, France) regarding 67 patients returning from endemic areas and infected with various Plasmodium species.
RESULTS: In 83% of infected samples with Plasmodium vivax (Pv), ovale (Po), or malariae (Pm), extra clouds of dots were present in neutrophil and/or eosinophil area(s) on routine differential (DIFF) scattergrams. In contrast, samples infected with Plasmodium falciparum (Pf) failed to show such DIFF scattergrams, or any other suggesting malaria infection (0/ 49 pts). Abnormal areas from DIFF scattergrams were related to the presence of mature schizonts and gametocytes, undestroyed by lysis agent, the latter not observed in Pf-infected patients from our series. The internal parameter WBC[DIFF] - WBC[BASO] raised in parallel to parasitemia in Pv, Po, and Pm samples but could not be used as a surrogate for parasitemia. In Pf infection, reticulocyte/ immature reticulocyte fraction (IRF) ratio showed a significant correlation with parasitemia (P < 0.05). A diagnostic model developed for Pf in endemic countries showed sensitivity of 77%.
CONCLUSION: Using SYSMEX analyzers, Pv, Po, and Pm infections are easy to ascertain as DIFF scattergrams are almost specific (specificity = 99.9%). Pf infection diagnosis by CBC may be a more promising tool
- …