615 research outputs found
The Massive Wolf-Rayet Binary SMC WR7
We present a study of optical spectra of the Wolf--Rayet star AzV 336a (= SMC
WR7) in the Small Magellanic Cloud. Our study is based on data obtained at
several Observatories between 1988 and 2001. We find SMC WR7 to be a double
lined WN+O6 spectroscopic binary with an orbital period of 19.56 days. The
radial velocities of the He absorption lines of the O6 component and the strong
He{\sc ii} emission at 4686\AA of the WN component describe antiphased
orbital motions. However, they show a small phase shift of 1 day. We
discuss possible explanations for this phase shift. The amplitude of the radial
velocity variations of He {\sc ii} emission is twice that of the absorption
lines. The binary components have fairly high minimum masses, 18
\modot and 34 \modot for the WN and O6 components, respectively.Comment: Accepted by MNRA
A Search for Wolf-Rayet Stars in the Small Magellanic Cloud
We conducted an extensive search for Wolf-Rayet stars (W-Rs) in the SMC,
using the same interference filter imaging techniques that have proved
successful in finding W-Rs in more distant members of the Local Group.
Photometry of some 1.6 million stellar images resulted in some 20 good
candidates, which we then examined spectroscopically. Two of these indeed
proved to be newly found W-Rs, bringing the total known in the SMC from 9 to
11. Other finds included previously unknown Of-type stars (one as early as
O5f?p)),the recovery of the Luminous Blue Variable S18, and the discovery of a
previously unknown SMC symbiotic star. More important, however, is the fact
that there does not exist a significant number of W-Rs waiting to be discovered
in the SMC. The number of W-Rs in the SMC is a factor of 3 lower than in the
LMC (per unit luminosity), and we argue this is the result of the SMC's low
metallicity on the evolution of the most massive stars.Comment: Accepted by Astrophysical Journal. Postscript version available via
ftp.lowell.edu/pub/massey/smcwr.ps.gz Revised version contains slightly
revised spectral types for the Of stars but is otherwise unchange
An Atlas of FUSE Sight Lines Toward the Magellanic Clouds
We present an atlas of 57 Large Magellanic Cloud (LMC) and 37 Small
Magellanic Cloud (SMC) observations obtained with the Far Ultraviolet
Spectroscopic Explorer (FUSE) satellite. The atlas highlights twelve
interstellar absorption line transitions at a resolution of ~15 km/s. These
transitions cover a broad range of temperatures, ionization states, and
abundances. The species included are OVI, which probes hot (T~3x10^5 K) ionized
gas; CIII and FeIII, which probe warm (T~10^4 K) ionized gas; SiII, PII, CII,
FeII, and OI, warm neutral gas; and six different molecular hydrogen
transitions, which trace cold (T<=500 K) gas. We include Schmidt Halpha CCD
images of the region surrounding each sight line showing the morphology of warm
ionized gas in the vicinity, along with continuum images near each FUSE
aperture position. Finally, we present several initial scientific results
derived from this dataset on the interstellar medium of the Magellanic Clouds
and Galactic halo.Comment: 29 pages, 6 figures. Complete Atlas of 94 additional images (~800kB
each) is available at http://fuse.pha.jhu.edu/~danforth/atlas Accepted to the
ApJS March 200
A near-infrared study of AGB and red giant stars in the Leo I dSph galaxy
A near-infrared imaging study of the evolved stellar populations in the dwarf
spheroidal galaxy Leo I is presented. Based on JHK observations obtained with
the WFCAM wide-field array at the UKIRT telescope, we build a near-infrared
photometric catalogue of red giant branch (RGB) and asymptotic giant branch
(AGB) stars in Leo I over a 13.5 arcmin square area. The V-K colours of RGB
stars, obtained by combining the new data with existing optical observations,
allow us to derive a distribution of global metallicity [M/H] with average
[M/H] = -1.51 (uncorrected) or [M/H] = -1.24 +/- 0.05 (int) +/- 0.15 (syst)
after correction for the mean age of Leo I stars. This is consistent with the
results from spectroscopy once stellar ages are taken into account. Using a
near-infrared two-colour diagram, we discriminate between carbon- and
oxygen-rich AGB stars and obtain a clean separation from Milky Way foreground
stars. We reveal a concentration of C-type AGB stars relative to the red giant
stars in the inner region of the galaxy, which implies a radial gradient in the
intermediate-age (1-3 Gyr) stellar populations. The numbers and luminosities of
the observed carbon- and oxygen-rich AGB stars are compared with those
predicted by evolutionary models including the thermally-pulsing AGB phase, to
provide new constraints to the models for low-metallicity stars. We find an
excess in the predicted number of C stars fainter than the RGB tip, associated
to a paucity of brighter ones. The number of O-rich AGB stars is roughly
consistent with the models, yet their predicted luminosity function is extended
to brighter luminosity. It appears likely that the adopted evolutionary models
overestimate the C star lifetime and underestimate their K-band luminosity.Comment: MNRAS, accepte
Developing and piloting a communication assessment tool assessing patient perspectives on communication with pharmacists (CAT-Pharm)
Background: Effective communication strategies in health care help to enhance patient empowerment and improve clinical outcomes. Objective: Adapt the original Communication Assessment (CAT) instrument for the pharmacist profession (CAT-Pharm) and to test its validity and reliability in two different settings. Setting: Five hospital pharmacies in Italy and five community pharmacies in Malta. Method: Pilot study involving a standardized multi-step process adhering to internationally accepted and recommended guidelines. Corrections and adjustments to the translation addressed linguistic factors and cultural components. CAT-Pharm, compared to the original CAT, maintained 10 out of the 14 items: one was slightly modified; three were changed to better fit the pharmacist role; one was added. Main outcome measure: CAT-Pharm development and testing its practicality to Assess patient perceptions of pharmacistsâ interpersonal and communication skills. Results CAT-Pharm was tested on 97 patients in the Italian setting and 150 patients in the Maltese setting to assess the practicality of the tool and its usefulness in investigating gaps and priorities for improving pharmacist-patient communication. Results: Show reliability and internal validity of the CAT-Pharm tool. The analysis of patient perceptions of communication with the pharmacist in Italy indicated differences from that in Malta. The different settings provided insight into the utility of CAT-Pharm. Conclusion: This study provided a valid and reliable tool that could be applied to assess patient perception of the pharmacist's communication abilities
Gram Negative Wound Infection in Hospitalised Adult Burn Patients-Systematic Review and Metanalysis-
BACKGROUND:
Gram negative infection is a major determinant of morbidity and survival. Traditional teaching suggests that burn wound infections in different centres are caused by differing sets of causative organisms. This study established whether Gram-negative burn wound isolates associated to clinical wound infection differ between burn centres.
METHODS:
Studies investigating adult hospitalised patients (2000-2010) were critically appraised and qualified to a levels of evidence hierarchy. The contribution of bacterial pathogen type, and burn centre to the variance in standardised incidence of Gram-negative burn wound infection was analysed using two-way analysis of variance.
PRIMARY FINDINGS:
Pseudomonas aeruginosa, Klebsiella pneumoniae, Acinetobacter baumanni, Enterobacter spp., Proteus spp. and Escherichia coli emerged as the commonest Gram-negative burn wound pathogens. Individual pathogens' incidence did not differ significantly between burn centres (F (4, 20)â=â1.1, pâ=â0.3797; r2â=â9.84).
INTERPRETATION:
Gram-negative infections predominate in burn surgery. This study is the first to establish that burn wound infections do not differ significantly between burn centres. It is the first study to report the pathogens responsible for the majority of Gram-negative infections in these patients. Whilst burn wound infection is not exclusive to these bacteria, it is hoped that reporting the presence of this group of common Gram-negative "target organisms" facilitate clinical practice and target research towards a defined clinical demand.peer-reviewe
Exploring the Leo II dSph I.: The Variable Star Content
We present the first comprehensive catalogue of variable stars in the Leo II
dwarf spheroidal galaxy. We have identified 148 RR Lyrae type variables, of
which 140 were amenable to derivation of variability parameters with our data.
We have also confirmed the existence of four anomalous Cepheids as identified
in previous studies.
The average period of the RR Lyrae ab variables (0.62 days), the fraction of
c variables (0.24) and the minimum period of the RR Lyrae ab variables (0.51
days) all define Leo II as an "Oosterhoff intermediate" galaxy. We have used
the properties of these variables to derive a metallicity for Leo II of
approximately [Fe/H]=-1.9. The presence of longer period, higher amplitude RR
Lyrae variable implies a metallicity distribution that extends to as poor as
[Fe/H]=-2.3.
Leo II's location on the period-metallicity relation of clusters, like that
of other ``Ootershoff intermediate'' objects, falls between the Oosterhoff
Class I and Oosterhoff Class II clusters. The properties of the variable
populations of these objects are consistent with the idea that the Oosterhoff
"dichotomy" is a continuum. The gap between the classes seems to be explained
by the horizontal branch of Galactic globular clusters shifting away from the
instability strip at at intermediate metallicities. However, Leo II, as well as
other Oosterhoff intermediate objects, has a second parameter effect strong
enough to leave horizontal branch stars in the instability strip.Comment: 44 pages, 8 figures, 3 tables, accepted in Astronomical Journa
The iron abundance of the Magellanic Bridge
High-resolution HST ultra-violet spectra for five B-type stars in the
Magellanic Bridge and in the Large and Small Magellanic Clouds have been
analysed to estimate their iron abundances. Those for the Clouds are lower than
estimates obtained from late-type stars or the optical lines in B-type stars by
approximately 0.5 dex. This may be due to systematic errors possibly arising
from non-LTE effects or from errors in the atomic data as similar low Fe
abundances having previously been reported from the analysis of the
ultra-violet spectra of Galactic early-type stars. The iron abundance estimates
for all three Bridge targets appear to be significantly lower than those found
for the SMC and LMC by approximately -0.5 dex and -0.8 dex respectively and
these differential results should not be affected by any systematic errors
present in the absolute abundance estimates. These differential iron abundance
estimates are consistent with the underabundances for C, N, O, Mg and Si of
approximately -1.1 dex relative to our Galaxy previously found in our Bridge
targets. The implications of these very low metal abundances for the Magellanic
Bridge are discussed in terms of metal deficient material being stripped from
the SMC.Comment: Accepted for publication in MNRA
A Study of Time-Dependent CP-Violating Asymmetries and Flavor Oscillations in Neutral B Decays at the Upsilon(4S)
We present a measurement of time-dependent CP-violating asymmetries in
neutral B meson decays collected with the BABAR detector at the PEP-II
asymmetric-energy B Factory at the Stanford Linear Accelerator Center. The data
sample consists of 29.7 recorded at the
resonance and 3.9 off-resonance. One of the neutral B mesons,
which are produced in pairs at the , is fully reconstructed in
the CP decay modes , , , () and , or in flavor-eigenstate
modes involving and (). The flavor of the other neutral B meson is tagged at the time of
its decay, mainly with the charge of identified leptons and kaons. The proper
time elapsed between the decays is determined by measuring the distance between
the decay vertices. A maximum-likelihood fit to this flavor eigenstate sample
finds . The value of the asymmetry amplitude is determined from
a simultaneous maximum-likelihood fit to the time-difference distribution of
the flavor-eigenstate sample and about 642 tagged decays in the
CP-eigenstate modes. We find , demonstrating that CP violation exists in the neutral B meson
system. (abridged)Comment: 58 pages, 35 figures, submitted to Physical Review
The Physical Properties and Effective Temperature Scale of O-type Stars as a Function of Metallicity. II. Analysis of 20 More Magellanic Cloud Stars, and Results from the Complete Sample
We analyze the optical and UV spectra of an additional sample of 20
Magellanic Cloud O stars, and draw conclusions from the complete sample of 40
stars. We find (1) The SMC O3-7 dwarfs are about 4000 K cooler than their
Galactic counterparts; this is in the sense expected from the decreased
signficiance of line-blanketing and wind-blanketing at lower metallicities. The
difference decreases with later types, becoming negligible by B0 V. A similar
difference is found for the supergiants. (2) The wind momentum of these stars
scales with luminosity and metallicty in the ways predicted by
radiatively-driven wind theory. (3) A comparison of the masses derived from
spectroscopy with those derived from stellar evolutionary theory shows a
significant discrepancy for stars hotter than 45000, although good agreement is
found for cooler stars. (4) For the hottest O stars (O2-3.5) neither the
NIII/NIV ratio, nor even the HeI/HeII ratio, does a good job of predicting the
effective temperature by itself. Instead, a full analysis is needed to derive
physical parameters. Thus there are O3.5V stars which are as hot or hotter than
stars classified as O2V. (5) The two stars with the most discordant radial
velocities in our sample happen to be O3 "field stars". This provides the first
compelling observational evidence that the "field" O stars in the Magellanic
Clouds may be runaway OB stars, ejected from their birth place.Comment: Accepted by the Astrophysical Journal. A version with
higher-resolution figures may be found at
ftp://ftp.lowell.edu/pub/massey/haw2final.pdf This replacement included a
revised version of Fig 29a and the accompanying tex
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